UNITED STATES DEPARTMENT OF THE INTERIOR

Ray Lyman Wilbur, Secretary

GEOLOGICAL SURVEY

W. C. Mendenhall, Director

STOCKTON AND FAIRFIELD QUADRANGLES, ·UTAH

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON: 1932
Abstract _

Introduction _

Location and accessibility _

Physical features _

Climate and vegetation _

Fieldwork _

Acknowledgments _

Bibliography _

General geology _

Principal features _

Sedimentary rocks _

General section _

Cambrian system _

Lower Cambrian series ~ _

Tintic quartzite _

Lower and Middle Cambrian series _

Ophir formation _

Middle Cambrian series _

Hartmann limestone _

Bowman limestone _

Middle (1) and Upper Cambrian series _

Lynch dolomite _

General relations of the Utah Cambrian __

Pre-Middle Devonian unconformity _

Devonian system _

Middle (1) Devonian series _

Jefferson (?) dolomite _

Pre-Mississippian unconformity _

Carboniferous system _

Mississippian series _

Madison limestone (lower Mississippian) _

.Deseret limestone (upper Mississippian) _

Humbug formation (upper Mississippian) _

"Great Blue" limestone (upper Mississippian) _

Mississippian and Pennsylvanian series _

Manning Canyon shale _

Pennsylvanian series ~ _

Oquirrh formation _

Regional correlation of the Carboniferous

of western Utah _

Tertiary system ~ _

conglomerate _

Quaternary system _

Alluvium and fanglomerate _

Lake Bonneville beds _

Talus deposits _

Glacial moraines _

Igneousrocks _

General features _

Extrusive rocks _

Subdivisions _

South Mountain, Stockton quadrangle _

Hornblende-hypersthene andesite or

latite breccia _

l'aa:e

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General geology-Continued.

Igneous rockS'-Continued.

Extrusive rocks-Continued.

Traverse Mountains ..__- _

General field relations _

General petrologic f.eatures _

Latitic bl'eccias _

Latite or andesite tuffs _

Latite flows _

Quartz latite flows ~. _

Rhyolite obsidian _

Nephelite basalt flow _

Olivine basalt flow _

Intrusive rocks _

Monzonite and related rocks _

Subdivisions _

Porphyry Knob and Lion HilL _

Soldier Canyon _

Stockton area ~ _

Settlement and Middle Canyons _

Tickville Gulch _

Butterfield Canyon _

Summary of structural relations _

Rhyolites __~ _

Subdivisions _

Eagle Hill rhyolite ~ _

Shaggy Peak rhyolite _

Tickville rhyolite ~ _

Andesite or latite intrusions _

Nephelite basalt _

Lamprophyre (kersantite) _

Geologic relations of the igneous rocks _

Mutual relations _

Source of the volcanic rocks _

Date of igneous activity _

Petrologic relations of the igneous rocks _

Regional relations of the igneous rocks _

Summary of igneous history _

Structure .. _

General features _

Folds ~ _

Ophir anticline _

Pole Canyon syncline ~ _

Long Ridge anticline _

Bingham syncline . _

Minor folds_. _

Regional relations of the folding _

Supposed extension of Uinta axis through BinghaDl _

Date of the folding _

Fautis _

General features _

Ophir-Silverado fault area~ _

Canyon fault _

Cliff fault c _

Lion Hill fault _

Minor faults. _~ • _

m
Structure--Continued.

Faults-Continued.

Ophir-Silverado fault area-Continued.

Age and origin of the Ophir-Silverado

faults _

Dry Canyon fault area _

Mono fault block _

Faults on Sharp Mountain ._

Date and origin of the Dry Canyon faults_

Basin Range fault system _

General features _

Fault south of Mercur Canyon _

West Mercur faulL _

Lakes of Killarney fault _

Unnamed fault north of Dry Canyon _

Soldier Canyon faulL _

Other faults supposedly to belong to the

Basin Range system _

General features of the Basin Range faults_

Distributive and en echelon faulting __

Length of faults _

Dips of faults _

Age of faulting _

Early movement _

Basin Range movemenL _

Cause of the Basin Range faulting _

Faults in the Stockton mining area _

Summary of geologic history _

Rock alteration _

Processes _

Dynamic metamorphism _

Igneous metamorphism _

Varieties _

Metamorphism within the igneous rocks _

Metamorphism of the sedimentary rocks _

Metamorphism of the quartzites, sandstones, and shales _

Metamorphism of the limestones _

General features _

Marmarization _

Silicification _

Alteration to lime silicates and accompanying sulphides _

Lime hornfels masses d ire c t I y

along igneous contacts _

Hornfels masses not dire c tly

along igneous contacts _

Paragenesis d u r in g horn f els

metamorphism _

Alteration to sulphide ores and accompanying gangue _

Replacement ore _

Fissure ore _

Alteration to dolomite _

Theory of igneous metamorphism and ore

deposition _

Agents of igneous metamorphism _

Transfer of material during metamorphism_

Composition of metamorphosing solutions_

Zonal theory of mineralization _

Weathering _

Weathering of the nonmetamorphic rocks _

Weathering of the metamorphosed rocks _

Jasperoid _

Lime silicate and sulphide bodies _

Mining history and production _

Rush Valley (Stockton) district _

Ophir districL _

Camp Floyd (Mercur) district _

Mineralogy _

Native elements _

Sulphides and arsenides _

Sulpharsenites and sulphantimonites _

Haloids _

Oxides _

Carbonates _

Silicates _

Titanosilicate _

Phosphates, arsenates, vanadates, etc _

Sulphates _

Ore deposits _

Classification _

Gold and gold-mercury deposits _

Bedded replacement deposits _

Fissure and vein deposits .

Silver and silver-lead deposits _

Bedded replacement deposits _

Mercur-Lion Hill area _

Foothill area between Ophir and Dry

Canyons _

Lead-silver-zinc-copper deposits _

Bedded replacement deposits _

Irregular replacement deposits _

Fissure deposits _

The mines _

Camp Floyd districL _

Mercur area _

Consolidated Mercur _

Geyser-Marion_ - - - - - - - - - - - - - - - - c - - - - --

Sacrarnento _

Sunshine area _

Overland _

Sunshine _

West Mercur or West Dip area _

Daisy (Norma) _

La Cigale _

Ophir district _

Lion Hill area _

Buffalo _

Chloride Point _

East Side, Monarch, Iron, Empire, Northern Light, and Woodruff _

Lion, ZelIa, Douglas, and adjacent mines_

Three Metals _

Foothill area ~ _

Lakes of Killarney _

Ophir Hill area _

Admiral Dewey " _

Cliff _

Hidden Treasure, Chicago, and Sacramento

Jim Fisk _

Ophir Coalition (Montana) _

Ophir Hill Consolidated _

Ophir Queen _

Dry Canyonarea _

Brooklyn _

Cornrnodore _

Deseret _

Eureka-Ophir _

lCearsarge _

Magnolia _

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The mines-Continued.

Ophir district-Continued.

Dry Canyon area-Continued.

~ono _

Queen of the Hills _

Surprise _

Thad Stevens _

Utah Queen .. _

Rush Valley district _

Stockton area . __. _

Argent _

Ben Harrison _

Calumet _

Galena King _

Honerine _

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1511

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160

The mines-Continued.

Rush Valley district-Continued.

Stockton area-Continued.

~uerbrook _

~uscatine _

Salvation-Hercules _

Southport _

Tiptop _

Soldier Canyon area _

~arj orie _

West ~ountain district _

West Canyon area _

~ayflower _

Index _

162

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Page

PLATE 1. Dry Canyon from hill west of Wandering Jew mine, looking east._________________________________________ 10

2. View looking north and northeast from a point on the Dry Canyon-Ophir Canyon divide about a quarter of a

mile southwest of mineral monument No. 4_ _ _____ ___ ____________ _ ______ ___ _ 10

3. A, View looking north from Lowe Peak; B, Lion Hill from north side of Ophir Canyon, showing Ophir anticline;

C, Landslide scar near head of Settlement Canyon, on main divide of Oquirrh Range______________________ 10

4. A, B, Specimens of Hartmann limestone, illustrating typical lithology ______________________________________ 26

5. A, Hand specimen of edgewise limestone conglomerate from Bowman limestone; B, Hand specimen of partly

metamorphosed basal ledge-forming member of Bowman limestone ______________________________________ 26

6. A, Hand specimen of "Eye bed" dolomite of Jefferson (?) dolomite; B, Hand specimen of Bluebird type of

dolomite from Lynch dolomite; C, Hand specimen of finely la~inated white-weathering dolomite from Lynch

dolomite ~_ 26

7. Correlations and variations of ~ississippian and Pennsylvanian formations of western Utah__________________ 42

8. A, Andesite breccia at northeast foot Of South ~ountain, Stockton quadrangle; B, Volcanic tuff, overlain by

andesite breccia, on divide between Stockings Fork and City Canyon, Fairfield quadrangle; C,Water-laid tuff on

divide between City Canyon and Water Fork, Fairfield quadrangle______________________________________ 42

9. A, Latite breccia at head of Oak Spring Canyon, Fairfield quadrangle; B, Scarp of West ~ercur fault in alluvium

at Bates ranch, Ophir Creek__ _____________ __ ____ _____________________ _____ 42

10. A, Step ~ountain plug from southwest, showing part of the sub circular ring dike; B, Step ~ountain from southeast, showing horizontal columnar structure of the ring dike surrounding the central plug ___________________ 74

11. Block diagram showing relations of Corbon No.1 and Garber-~ark Antony faults to ~ono fault block, Dry

Canyon__________________________________________________________________________________________ 74

12. Topographic and geologic map of the Stockton and Fairfield quadrangles, Utah In pocket.

13. Detailed geologic map of Ophir and Dry Canyons -------------------________________ 90

14. A, "Typical jasperoid" textured variety of jasperoid, with crossed nicols; B, Same as A, plain light; C, Anhedral

variety of jasperoid, veined with barite that contains euhedral quartz crystals, with crossed nicols; D, Same

as C, plain light -__ __ ____________________________________ ___ 106

15. A, Basal section of euhedral quartz crystal outlined by carbon, plain light; B, Same as A, with crossed nicols;

C, Quartz showing "ghosts" of spherules; D, Same as C, with crossed nicols______________________________ 106

16. A, Brecciated barite plate in matrix of fine anhedral quartz which shows no brecciation and replaces and is euhedral

in detail against the barite, plain light; B, Same as A, with crossed nicols_ __ _____________________________ 106

17. A, Fine-grained anhedral quartz brecciated and veined with coarsely crystalline quartz; B, Colloform structures

in chalcedony .____ 106

18. A, Third-generation quartz showing flow lines along boundaries of cracks in barite, plain light; B, same as A, with

crossed nicols_____________________________________________________________________________________ 106

19. A, Quartz showing strain twinning; B, Calcite replaced by stringers of quartz, carrying minute sericite plates

and a little barite_ ________________________________________________________________________________ 106

20. A, Lime hornfels, consisting of calcite-rich, orthoclase-rich, and epidote-rich bands, partly replaced by pyrrhotite;

B, Photomicrograph of hornfels ore, showing tendency of sulphides to be molded on the euhedral quartz

crystals___________________________________________________________________________ 106

21. A, Hand specimen of banded hornfels; B, Hand specimen showing vertical fissure vei.n consisting of pyrite,

sphalerite, and galena, cutting cleanly the horizontally banded hornfels ._________ 106

22. A, Hand specimen showing rosettes of sericite replacing and invading earlier pyrite and galena; B, Sulphideimpregnated hornfels showing banding due to selective replacement._____________________________________ 106

23. A, Hand specimen of ore from Ophir Hill mine; B, Garnet hornfels impregnated and partly replaced by pyrite,

sphalerite. and galena, Ophir Hill mine . ___________ ______ 106
Page

PLATE 24. Hand specimen of dolomite, veined and partly replaced by sulphides, orthoclase, and quartz, Ophir Hill mine__ 106

25. Mine map of the workings on the east side of Lion Hill and Chloride Point, Ophir district In pocket.

26. Map of the workings of the Sacramento mine, Mercur area__________ _ __ _______ _ . 138

27. Map showing workings of the Cliff, Hidden Treasure, Sacramento, and Chicago mines, Ophir district 154

28. Stope map and sections of ore bodies of the Ophir Hill Consolidated mine, Ophir district_ _ __________ _______ _ 154

29. Map of the Mono mine and Surprise tunnel, Dry Canyon_______________________________________________ 154

30. Map of the Galena King mine, Stockton district_ _ _ _ _______________________________ ____________________ 162

31. Map of the Honerine mine, Stockton district In pocket.

32. East-west vertical projection of workings on the "Galena King" limestone, Stockton district________________ 162

FrGURE 1. Index map showing location of Stockton and Fairfield quadrangles and of other metalliferous districts of Utah

described in detailed reports of the United States G~ological Survey___________________________________ 2

2. Variations of Cambrian formations of western Utah in a west-east direction in the latitude of Ophir-_______ 18

3. Variations of Cambrian formations of western Utah and southeastern Nevada in a southwest-northeast direction_ 19

4. Detail of contact between Jefferson (?) dolomite and Madison limestone, showing typical small-scale karst

topography of the contact surface__________________________________________________________________ 22

5. Partial sections of the lower part of the Oquirrh formation measured on the west slope of Lewiston Peak,

Fairfield quadrangle, showing lateral variations in beds_______________________________________________ 35

6. Eastward shift in site of thick sedimentation between pre-Carboniferous and Carboniferous time in western

Utah, southeastern Idaho, and eastern Nevada, as shown by stratigraphic sections_______________________ 39

7. Relations of dike and country rock in east fork of Settlement Canyon, showing deformation of the country rock,

presumably by the force of igneous intrusion_ ___ __________ _____ _____________________________ _ 54

8. Relations of weight percentages of CaO, Na20, and K20 with variations in the silica content of the analyzed

rocks from the Oquirrh Mountains_ ______________ ___________ ________ ____________________ ___ _______ 66

9. Relations of West Mercur fault in inclined shaft of Daisy (West Dip No.1) mine__________________________ 82

10. Relations of West Mercur fault in inclined shaft of La Cigale mine .•. 82

11. Relations of West Mercur fault to the topography, alluvium, and bedrock near West Mercur________________ 82

12. Map showing .the distribution of jasperoid in the vicinity of Mercur_________ 97

13. Tracing of photomicrograph, showing euhedral orthoclase (adularia) crystals inclosed in quartz groundmass 106

14. Paragenetic relations of minerals in hornfels ore at Ophir _ _ _ _____________________ _______________________ 108

15. Paragenesis of limestone-replacement ore minerals_ _ _______ __________________ __________________________ 110

16. Generalized section of the ore beds in the Mercur districL ____________________________ _____ ______ _______ 133

17. Geologic map of the Three Metals tunnel; Ophir district________________________________________________ 142

18: Map of the workings of the Jim Fisk mine, Ophir district_______________________________________________ 147

19. Map of the accessible workings of the Brooklyn mine, Dry Canyon______________________________________ 151

20. Map and section of the Kearsarge mine workings, Dry Canyon__________________________________________ 153

21. Map of the Ben Harrison mine, Stockton districL_____________________________________________________ 158

22. Map of the Salvation-Hercules mine, Stockton district_________________________________________________ 164
GEOLOGY AND ORE DEPOSITS OF THE STOCKTON AND FAIRFIELD

QUADRANGLES, UTAH

The Stockton and Fairfield quadrangles lie in west-central

Utah and embrace the southern portion of the Oquirrh Mountains, one of the most easterly ranges of the Basin and Range

province. The mass of the Oquirrh Range is composed of sedimentary rocks, chiefiy of Paleozoic age. The Cambrian system

is represented b~' Lower Cambrian quartzite and shale, Middle

Cambrian shale, limestone, and dolomite, and Upper Cambrian

dolomite, aggregating about 2,500 feet in thickness and apparently conformable throughout. The Upper Cambrian is unconformably overlain by Middle (?) IJevonian dolomite about

185 feet thick. Unconformably overlying the Devonian dolomite, in which karst topography had been developed on a small

scale, are Mississippian beds including 450 feet of Madison

limestone (lower Mississippian) and nearly 5,000 feet of limestone, with some shale and sandstone, equivalent in age to

the Brazer limestone (upper Mississippian) of northeastern

Utah and Idaho. A phosphatic shale at the base of this group

of upper Mississippian age is noteworthy. Overlying the limestone are Mississippian shale and quartzite, immediately followed by similar rocks of Pennsylvanian age. This transition

unit is about 1,100 feet thick and probably includes a minor

unconformity. It is succeeded by fully 15,000 feet, perhaps

20,000 feet, of interbedded quartzite and limestone of Pennsylvanian age. There is no record of possible Permian or

Mesozoic sedimentation.

At the end of the Cretaceous period or early in the Tertiary

the region was compressed and the strata folded along axes

which toward the south of the range trend in a north-north-.

west direction but toward the north edge of the quadrangles

curve gradually into northwesterly and even westerly trends.

These folds are all asymmetric, and some are overturned toward

the northeast, but all are open and nowhere closely appressed.

Subsequent to the folding, which was accompanied by minor

faulting, volcanic activity began, and considerable thicknesses

of latitic breccias and tuffs were deposited, burying a topography of considerable relief. After these pyroclastic rocks (in

which a few thin flows are interbedded) were laid down flow

rocks predominated among the volcanic products, and a total

thickness of more than 3,000 feet of extrusives accumulated.

In this volcanic area there were at least two volcanic vents,

one of which, Step Mountain, is marked by a breccia-filled plug

surrounded by a fine example of a ring dike.

The monzonitic magma, whose ejected representatives form

the volcanic series, rose locally to and into the base of its own

ejecta, as in Tickville Gulch, where a diorite plug is intrusive

into a latite flow. Elsewhere the monzonitic rocks, which

range in composition from granodiorite to quartz diorite and

diorite, probably failed to reach the prevolcanic surface. The

intrusive rocks appear in small stocks, dikes, and sills which

trend in an irregular belt southwestward from Butterfield

Canyon to Soldier Creek and thence southward in less quantity

almost to Mercur. They were accompanied by rhyolite dikes

and plugs, which intruded both the volcanic rocks of the

Traverse Mountains and the Paleozoic sediments. A few

bodies of lamprophyre and nephelite basalt also occur, the

latter both in sills and a flow.

The monzonitic intrusive rocks show some evidence of forcible

injection in the deformation of the inclosing rocks. Two large

normal faults in Ophir Callyon, whose combined displacement

amounts to nearly 3,000 feet, are thought to owe their origin

to igneous forces. Typical Basin Range faulting is prominent

along the west front of the range. Contact metamorphism has

been notable in the sediments surrounding the larger monzonitic masses. Marbleization, dolomitization of some limestone, and propylitization of igneous rocks have all occurred

on a small scale, silicification with the production of jasperoid

is widespread, and large amounts of " contact" silicates such as

wollastonite, epidote, garnet, and adularia have been produced.

The formation of sulphides has accompanied both the jasperoid

and the silicate varieties of metamorphism, and the economically important deposits are due to this phase of the igneous

metamorphism.

Ore was discovered in this area in 1864, and mining has continued on a greater or less scale to the present time. The production from the beginning of mining to the end of 1927 from

all the mines of the quadrangles was probably about $49,000,000,

of which over $19,000,000 was derived from the gold and goldmercury deposits of Mercur, where work was stopped in 1913,

over $20,000,000 from Ophir, and the remainder from the Rush

Valley district, near Stockton. The Ophir and Rush Valley

districts produce chiefly lead, silver, and zinc.

The ores occur chiefly as bedded replacement deposits and

veins. Gold and mercury occur in and associated with jasperoid at Mercur, and silver and silver-lead with jasperoid

near Mercur and on Lion Hill. Lead-silver-zinc-copper deposits, chiefly of bedded replacement type, occur in hornfels at

Ophir and are associated with metamorphic lime-silicate rock

in Dry Canyon and at Stockton. Supergene enrichment has

been slight.

INTRODUCTION

LOCATION AND ACCESSIBILITY

The Stockton and Fairfi~ld quadrangles embrace

the area bounded by meridians 112° and 112° 30' and

parallels 40° 15' and 40° 30' and include a little more

of the Oquirrh Mountains than the southern half.

This area lies about 20 miles southwest of Salt Lake

City, its north boundary passing 2 or 3 miles south of

Bingham and Tooele, and includes portions of Tooele,

Utah, and Salt Lake Counties. (See fig. 1.) The

1
Camp Floyd, Ophir, and Rush Valley mining districts, which include the mines of Mercur and Sunshine (inactive since 1913), Ophir, Dry Canyon, and

Stockton, lie within the area, and the great mines of

Bingham Canyon are just outside its northern limits.

The main line of the Los Angeles & Salt Lake Railroad passes through the Stockton quadrangle, with

stations at Bauer, Stockton, St. John, and Ajax. The

Toward the northern part of the Basin and Range

province 1 its eastern limit is placed at the western

base of the great Wasatch Range. Next to the west,

and separated from the Wasatch only by the valley of

the Jordan River, is the Oquirrh Range, which is

itself less than 30 miles long but is a link in a roughly

linear uplift that is continued, with only narrow interrupting lowlands, far to the south

in the East Tintic and Canyon Ranges

and to the north in Antelope Island, in

Great Salt Lake.

Northwest of the Oquirrh Mountains

lies Tooele Valley, northeast is Salt

Lake Valley, and the deep depression to

which both are tributary is occupied by

Great Salt Lake, whose waves wash the

base of the northern spurs of the range.

South of Tooele Valley and separated

from it by South Mountain, which

forms a comparatively low transverse

divide, Rush Valley forms a typical

Basin Range depression between the

Oquirrh and East Tintic Mountains on

the east and the Stansbury, Onaqui, and

'West Tintic Mountains on the west. Its

lowest portion, at the extreme north end,

is occupied by Rush Lake, a fresh-water

body, which fluctuates widely in area

with the changing seasons.

East from the Oquirrh Mountains a

lower spur, the Traverse Mountains, extends far out toward the Wasatch Range

and divides Salt Lake Valley on the

north from Cedar and Utah Valleys on

the south. The constricted depression

between the Traverse and Wasatch

Mountains is occupied by the Jordan

River, ~hich drains the waters of Utah

Lake northward toward Great Salt

Lake. The undrained basin of Cedar

Valley lies south of the Traverse Mountains and east of the Oquirrh Mountains

and is separated from Utah Lake farther east by a narrow range, the Lake

Mountains. On the south Cedar Valley is separated

from Goshen Valley, a small tributary of Utah Valley, by a low divide whose existence testifies to the

inadequacy of the rainfall quickly to integrate the

drainage of this typical portion of the Basin and

Range province.

The Oquirrh Range trends practically north and

south and is from 6 to 12 miles wide. Its main divide

lies a few miles east of the meridian dividing the

FIGUREI.-Index map showing location of Stockton and Fairfield quadrangles and of

other metalllferous districts of Utah described in detailed reports of the United

States Geological Survey. 1, Fairfield; 2, Stockton; 3, Bingham; 4, Park City; 5,

Cottonwood; 6, Gold Hill; 7, Tintlc; 8, Frisco; 9, Iron Springs

St. John & Ophir Railroad, owned by the Ophir Hill

Consolidated Mining Co., connects the Ophir mines

with this railroad ~t St. John station. A branch line

of the Los Angeles & Salt Lake Railroad, connecting

Lehi Junction with the Tintic disrict, traverses the

southeastern portion of the Fairfield quadrangle, with

a station near Fairfield, where the junction was formerly made with the Salt Lake & Mercur Railroad to

the Mercur mining district. The line to this camp

was dismantled in 1914, one year after the camp was

abandoned. 1Fenneman, N. M., and others, Physiographic divisions of the United

States: Assoc. Am. Geog. Annals, vol. 6, pp. 19-98, map, 1917.
Base enlarged from U. S. G. S. map of

Stockton and Fairfield quadrangles

Surveyed in 1915 and 1916

Geology by James Gilluly assisted by

:1. Mile H. G. Mitchell, W. D. Mark, and M. J. Buerger

I Surveyed in 1926 and 1927.

DETAILED GEOLOGIC MAP OF OPHIR AND DRY CANYONS.

OQUIRRH RANGE. UTAH

EXPLANATION

SEDIMENTARY ROCKS

oAlluvium

~

.;1

~

! Oquirrh formation

~

.§l>. "Great Blue" limestone -

.~ (with Long Trail shale member•

.; Clt. abo", t 500 feet above tJu base)

~

Iil>.

~

Madison limestone

UNCONFORMITY

~

Jefferson (?) dolomite

UNCONFORMITY

I~Itl

Lynch dolomite

~

~

Hartmann limestone

Tintic quartzite

-

JIo

[BJ

Lamprophyre (kersantite)

l~lJ

Mon7onite. monzonite por~

phyry, and related rocks

L(indUding "Birdseye" porphyry)

'('so·

Strike and dip

1('18

Mine

(See list of mines on areal geologic map)

X

Prospect
Stockton and Fairfield quadrangles. Altitudes in the

two quadrangles range from less than 5,000 feet in

'Tooele, Rush, Cedar, and Salt Lake Valleys to 10,572

feet on Lowe Peak and to 10,626 feet on the unnamed

peak about a mile north of Lewiston Peak, as shown

on the Fairfield topographic map. This unnamed

peak was called Lewiston Peak on the topographic map

of the Fortieth Parallel Survey.2

The mountains are rather rugged, especially near

the border of the mass, though toward the south end

of the range they present more rounded slopes and less

precipitous canyons. Similar subdued topography is

found at altitudes above 8,000 feet over a large part

of the range, and it is evident that the rugged character of the parts near the intermontane depressions and

the major drainage courses of the mountain mass itself

is due to rejuvenation of erosion in an area formerly

less sharply dissected.

Great alluvial deposits slope away from the mountain mass into the adjacent basins, there to coalesce

with similar fans from the other bordering ranges.

These alluvial deposits meet at very gentle slopes but

rise at increasing gradients toward the mountains.

The lowest parts of all these depressions were formerly

occupied by the waters of the great Lake Bonneville,3

and many of the shore features of that water body are

clearly recognizable. The most marked of these features is doubtless the Stockton Bar, which extends

across the valley between South Mountain and the

Oquirrh Mountains just north of Stockton; but many

remnants of the old beach line are clearly recognizable

for 10nO'distances in both Rush and Cedar Valleys.

The ~eneral topography of the area is fairly well

illustrated in the accompanying Plates 1, 2, and 3.

The drainage of the mountain mass is effected by

many small canyons and a few large ones. The principal drainage courses on the west flank of the range

within the area covered by this report are, from south

to north, Sunshine, Mitchell, Mercur, Silverado,

Ophir, Dry, Soldier, Settlement, and Middle Canyons.

On the east side, Manning, Pole, West, Rose, and Butterfield Canyons are ~he dominant ones. Of these,

only Ophir, Soldier, Settlement, Middle, West, Rose,

and Butterfield Canyons carry perennial streams, and

these are all very small, though of vital importance

to the people of the region. Ophir and Settlement

Canyons carry enough water to operate small hydroelectric plants. The drainage tunnel of the Honerine

mine is a significant factor in irrigation, supplying

water to 360 acres of excellent orchard and farm land.

Hickman Creek and Clover Creek rise in the Stansbury Mountains, west of Rush Valley, and supply

water for irrigating several farms in the valley.

• u. s. Geol. Expl. 40th Par., Atlas sheet III, 1877.

• Gilbert, G. K., Lake Bonneville: U, S, Geol. Survey Mon. 1, 1890.

67463-3Zr--2

CLIMATE AND VEGETATION

The climate of the Stockton-Fairfield area, in common with that of the remainder of the Great Basin,

is arid but the precipitation varies widely with the

altitud~. The only weather data for points within

the quadrangles are some partial records from St.

John,4 according to which the annual precipitation

may be as low as 6.43 inches. This is probably a

minimum for the area,. The maximum, which would

be on the higher summits of the range, may approach.

or even slightly exceed 20 inches.' St. John has a

temperature range from -36° to 110° F. It is probable that this maximum is not greatly exceeded anywhere in the Stockton-Fairfield area, but on the higher

peaks the minimum temperature may be somewhat

lower than this.

The vegetation of the area varies notably, in response to varying conditions of rainfall, temperature,

and depth of ground water. The higher areas carry,

especially on northward-facing slopes, good growths

of Douglas fir, with considerable spruce and some

pinon and yellow pine. Aspen, scrub oaks, box elders,

and alders are thick in the higher canyons and gulches.

Lower mountain slopes bear a considerable growth of

juniper (" cedar "), pinon, and scrub oak. The cliff

rose, buck brush, June berry, and several varieties of

mountain mahogany grow on many of the mountain

slopes, in places making nearly impenetrable patches.

Brigham's tea is a plant of the mountain slopes, and

the bulb cactus, prickly pear, and sagebrush are practically ubiquitous at lower altitudes. The alluvial deposits along the watercourses near the mountain front

Dud in the lowest parts of the intermontane depressions support considerable greasewood, but on the

flanks of the basins the vegetation is practically

limited to sagebrush, salt sage, bulb cactus, and prickly

pear, with some bunch grasses and salt grass. Grasses

are rather luxuriant on the higher slopes, or would

be if the area were not so overgrazed. Lupine, Mariposa lily (Sego lily), gilia, pie weed, B alsamorhiza,

numerous varieties of aster, and many other flowering

plants are widely distributed.

A great many sheep and some cattle and horses

graze over the higher hills. A few farms, irrigated

from the mountain streams or from springs in the

valleys, complete the rather meager list of the agricultural resources of the district. Fairfield and Cedar

Fort, in Cedar Valley, and Clover and St. John, in

Rush Valley, are agricultural villages. Ophir, Stockton, and Bauer are primarily mining communities,

though a few small farms are tributary to each of

them.
FIELD WORK

The field work upon which this report is based

began in 1925, when a reconnaissance preliminary to

prospective detailed work was carried on by Sidney

Paige. Mr. Paige resigned from the Geological Survey before the field season of 1926,when the work devolved upon the present writer.

With Mr. Paige's preliminary results in hand, detailed work was carried on by the writer from June

25 to October 10, 1926, and from May 1 to October 1,

1927, a total period of 8% months. During the season

of 1926 M. J. Buerger served as assistant, and in 1927

Gordon New, Leland Capener, Harold G. Mitchell,

and William D. Mark assisted at different times.

The geologic map was made by means of plane table

&ndopen-sight alidade, upon a topographic base photographed to a scale of 1: 31,250. The sole vertical control used was the contoured base map; accordingly

stratigraphic thicknesses computed from the outcrop

maps are not reliable within a limit of plus or minus

two cOilltourintervals, or 100 feet. All stratigraphic

sections of less than 1,000 feet were measured by clinometer, and thicker sections were measured directly

from the topographic base, details being filled in by

clinometer and tape surveys. Accurate transit and

tape surveys across the outcrops of the pre-Carboniferous rocks in Ophir Canyon were available through

the courtesy of the Ophir Hill Consolidated Mining

Co., and sections of these formations were tied to these

surveys.

ACKNOWLEDGMENTS

G. F. Loughlin, geologist in charge of the section of

metalliferous deposits, supervised the work throughout

and visited the field twice during the progress of the

work. Hearty acknowledgement is made for his numerous valuable suggestions both in the field and in

the office. Adolph Knopf, then a member of the section of metalliferous deposits, spent a week visiting the

writer in the field during the season of 1926 and offered

many useful ideas from his wide experience in mining

geology. To Sidney Paige the writer is also indebted,

for his reconnaissance work was of great usefulness in

giving the general setting essential to detailed geologic

work, and numerous hints left in his field notes were

of the utmost value. Edwin Kirk and G. H. Girty,

of the United States Geological Survey, visited the

writer in the field and assisted in making fossil collections and in stratigraphic work based on them. To

them and to Dr. C. E. Resser, of the Smithsonian Institution, is due the credit for all fossil identifications

herein incorporated. H. G. Mitchell and W. D. Mark

furnished exceptionally energetic and intelligent

assistance during their cOlllnectionwith the work.

To the numerous mining men of the region the

writer is especially indebted for unfailing courtesy

and cooperation. Special thanks are due to H. M.

Hartmann and E. S. Bowman, of the Ophir Hill Consolidated Mining Co.; E. H. Snyder, S. E. Craig, and

W. A. Young, of the Combined Metals Reduction Co.;

M. C. Godbe, A. J. May, and H. G. Mitchell, of the

Ophir Mono Coalition; D. W. Lynch and George St.

Clair, of Ophir; Frank Dederich, of Stockton; and

R. T. Walker and J. Fewson Smith, of the U. S.

Smelting, Refining & Mining Co., of Salt Lake City.

Much of the map of the Honerine mine is a direct

copy of the work· of W. A. Young, with only very

minor emendations.

The following papers touch upon the geology or

mining industry of the Stockton and Fairfield quadrangles:

1858. Engelmann, Henry, Prelimins.ry report on the geology

of the country between Fort Bridger and Camp Floyd,

Utah Territory, etc.: 35th Cong., 2d sess., S. Ex. Doc.

40, pp. 45-75. Of merely historical interest.

1872. Murphy, J. R., The mineral resources of the Territory

of Utah, pp. 20-21, 29-31, 40, Salt Lake City, James

Dwyer. A brief discussion of early mining.

1875. Gilbert, G. K., Report on the geology of portions of

Nevada, Utah, California, Arizona, etc.: U. S. Geog.

and Geol. Surveys W. 100th Mer. Rept., vol. 3, pp.

25-26, 181; and Howell, E. E., idem, pp. 237-238.

Very brief mention of Silurian (now Cambrian) and

Carboniferous strata.

1876. Zirkel, F., Microscopical petrography: U. S. Geol. Expl.

40th Par. Rept., vol. 6, pp. 66, 67, 132,'156. Very short

notes on rock collections.

1877. Emmons, S. F., Descriptive geology: U. S. Geol. Expl.

40th Par. Rept., vol. 2, pp. 443-456. Notes on structure and stratigraphy, with fossil lists.

1877. White, C. A., Report upon the invertebrate fossils collected in portions of Nevada, Utah, etc.: U. S. Geog.

and Geol. Surveys W. l00th Mer. Rept., vol. 4, pt. I,

pp. 44, 92 et seq. Faunal lists with brief notes on the

stra tigrapby.

1878. King, Clarence, Systematic geology: U. S. Geol. Expl.

40th Par. Rept., vol. 1, pp. 184-185, 197-199, 213-214,

393, 590. Very brief notes on stratigraphy, paleontology, and volcanic rocks.

1885. Huntley, D. B., The mining industries of Utab: U. S.

10th Census, vol. 13, pp. 447-455. Excellent brief descriptions of ea.rly-day mining.

1886. Walcott, C. D., Cambrian faunas of North America:

U. S. Geol. Survey Bull. 30, pp. 39-40, 1886. A brief

correlation note on the Ophir Canyon Cambrian section.

1890. Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon.

1, pp. 14, 52, 58, 97, 104, 137-138, 149, 184, 228, 352,

365-372, 412-419. Describes the fault scarp at the

mouth of Ophir Creek, the shore features of Lake

Bonneville, especially the Stockton Bar, and the relations of Rush and Tooele Valleys.

1891, Walcott, C. D., Correlation papers-Cambrian: U. S.

Geol. Survey Bull. 81, pp. 319-320, 1891, Discusses

correlation of the section at Ophir with other Cambrian sections in Utah.
1894. Moeller, ..W. H., The Mercur gold deposits in the Camp

Floyd district, Utah: Eng. and Min. Jour., vol. 57,

p. 51. A brief note only.

1894. Hills, R. C., Ore deposits of the Camp Floyd mining district, Tooele County, Utah: Colorado Sci. Soc.-Proc.,

vol. 5, pp. 54-65, 1898. (Read Aug. 6, 1894.) A summary discussion of Mercur in the early days of gold

mining.

1895. Spurr, J. E., Economic geology of the Mercur mining district, Utah, with an introduction by S. F. Emmons:

U. S. Geol. Survey Sixteenth Ann. Rept., pt. 2, pp.

395-455. A detailed account of the Mercur ore deposits.

1896. Neill, J. W., The Camp Floyd district, Utah: Eng. and

Min. Jour., vol. 61, pp. 85--86,1896. A short note.

1896. Waring, W. G., The Mercur district: Eng. and Min. Jour.,

vol. 62, p. 27. A short note only.

1897. Gemmell, R. C., The Camp Floyd mining district and the

Mercur mines, Utah: Eng. and Min. Jour., vol. 63, pp.

403-404. Treats chiefly of mines and mining methods.

1898. Maguire, Don, Gold mines of Mercur: Mines and Minerals, vol. 19, pp. 81-83, 130-131. Treats chiefly of

mining methods.

1904. Dern, G. H., The geology of Mercur: Mines and Minerals,

vol. 24, pp. 543-545. Discusses ore occurrences and

ore shoots.

1905. Boutwell, J. M., Economic geology of the Bingham mining district, Utah: U. S. Geol. Survey Prof. Paper 38.

Area covered includes part of Butterfield Canyon, in

the Fairfield quadrangle.

1907. Boutwell, J. M., Quicksilver: U. S. Geol. Survey Mineral

I Resources, 1906, p. 494. Has a brief note on the

quicksilver ore of the Sacramento mine at Mercur.

1908. Brinsmade, R. R, Mining and milling at Stockton, Utah:

Eng. and Min. Jour., vol. 85, pp. 611-612. Contains a

very superficial and inaccurate description of the

geology of the Honerine mine.

1908. Wilson, G. B., Geology of the Honerine mine, Stockton,

Utah: Eng. and Min. Jour., vol. 85, pp. 869-870. Corrects the inaccuracies of Brinsmade's paper.

1908. Walcott, C. D., Cambrian geology and paleontology:

Smithsonian Misc. CoIl., vol 53, No.5, p. 171, 1908.

Gives faunal and stratigraphic notes.

1909. Palmer, L. A., Milling practice at the Consolidated

Mercur: Salt Lake Min. Rev., vol. 10, p. 16. Deals

only with milling.

1910. Allen, R. H., Mines and mills of the Consolidated Mercur

Co.: Eng. and Min. Jour., vol. 89, pp. 1273-1277.

Treats chiefly of mining methods.

1910. Gansl, G. C., and Keep, G. A., Ophir mining district of

Utah: Salt Lake Min. Rev., vol. 12, No.8, pp. 17-20,

1910. A short sketch of the geology and mines.

1912. Walcott, C. D., Cambrian Brachiopoda: U. S. Gool. Survey Mon. 51, pt, 1, pp. 164-165, 261. Gives faunal

lists from Cambrian of Ophir Canyon.

1913. Maguire, Don, and Howard, L. 0., The romance of a

famous gold mine: Salt Lake Min. Rev., vol. 12, June

15, pp. 13-15; June 30, pp. 13-17; July 15, pp. 10-15.

Treats principally of milling methods at Mercur, Sunshine,.and West Dip.

1913. Carpenter, Everett, Ground water in Box Elder and

Tooele Counties, Utah: U. S. Geol. Survey WaterSupply Paper 333. Has brief account of the alluvial

filling of Rush Valley.

1914. Burling, L. D., Early Cambrian stratigraphy in the North

American Cordillera, with discussion of Albertella

and related faunas: Canada Geol. Survey Mus. Bull.

2, pp. 93-129. A discussion of the Lower and Middle

Cambrian section at Ophir.

191~. Walcott, C. D., The Cambrian and its problems in the

Cordilleran region: Problems in American geology,

p. 165, New Haven, Yale University Press. A brief

account of the Cambrian formations.

1916. Atwood, W. W., The physiographic conditions at Butte,

Mont., and Bingham Canyon, Utah, when the copper

ores in these districts were enriched: Ecoo. Geolegy;

vol. 11, pp. 73Z--140,1916. TreatB<ilt a cunlOl'y way the

physiography 01 thes'Oqulzrb Monntains.

1918. Loughlin, G. F., Zinc carbonate and related copper carbonate ores at Ophir, Utah: U. S. Geol. Survey Bull.

690, pp. 1-14. A description of the oxidized ores of

the Hidden Treasure mine, with a discussion of the

chemistry of their formation.

1920. Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof. Paper 111, pp. 362-395. A penetrating discussion of the economic geology of the area, although

based only upon brief reconnaissance studies.

1920. Wichman, F. M., The Ophir mining district, Utah; Eng.

and Min. Jour., vol. 110, pp. 560-563. A description of

the geology of Ophir and an attempted correlation

with Tintic.

1921. Olmstead, S. G., Economic geology of the Ophir mining

district, Utah: Econ. Geology, vol. 16, PI>. 433--456.

An attempted correlation of the section at Ophir with

that in the Tintic district, with a brief account of the

structure and mineral deposits.

1924. Porter, C. A., Intersecting fracture zones and mineral districts: Eng. and Min. Jour., vol. 118, pp. 650-651. An

interpretation of the Bingham and Stockton mining

areas as controlled by east-west fissuring connected

with the extension of the Uinta axis westward.

1925. Davis, W. M., The Basin Range problem: Nat. Acad.

Sci. Proc., vol. 11, pp. 391-392. Discusses the faultblock origin of the Oquirrh Mountains.

1926. Robie, E. H., Selective flotation at Bauer, Utah: Eng.

and Min. Jour.-Press, vol. 121, p. 405. Describes the

flotation mill of the Combined Metals Reduction Co. at

Bauer.

1926. Martin, Gail, Flotation and leaching plant of the Combined Metals Reduction Co.: Eng. and Min. Jour., vol.

122, p. 542. Describes flotation mill of the Combined

Metals Co.

1927. Beeson, J. J., Mining districts and their relation to

structural geology: Am. Inst. Min. and Met. Eng.

Trans., vol. 75, pp. 768-792. Treats principally of

Bingham but is based on general geology of the

Oquirrh Mountains. Discussion by C. A. Porter, pp.

793-796, is a reply to Beeson's interpretation that

fissuring and mineralization in the Oquirrh Mountains

are connected with a continuation of the Uinta uplift.

1928. Walker, R. T., Deposition of ore in preexisting limestone

caves: Am. lnst. Min. and Met. Eng. Tech. Pub. 154,

p. 17. Contains casual mention of the ore bodies of

the Ophir Hill mine as being localized by bedding

faults.

1928. Keiser, H. D., Flotatiod equipment of the Combined

Metals Reduction Co.: Eng. and Min. Jour., vol. 126,

pp. 253-255. Deals only with the mills.

1928. Gilluly, James, Basin Range faulting along the Oquirrh

Range, Utah: Geol. Soc. America BulL, vol. 39, pp.

1103-1130. A description of the Basin Range faults

in the area, with some consideration of their

mechanics.

1929. Gilluly, James, Possible desert-basin integration in Utah:

Jour. Geology, vol. 37, pp. 672-682. A discussion of

possible drainage diversion from Rush to Tooele Valley in pre-Lake Bonneville time.
1930. Larsen, E. S., and Shannon, E. V., The minerals of the

phosphate nodules from near Fairfield, Utah: Am.

Mineralogist, vol. 15, pp. 307-331, 1930. Contains descriptions of a number of rare phosphate minerals

from a prospect dump in Clay CanYon, Fairfield

quadrangle.

1901~. Annual volumes of Mineral Resources of the United

States, published by U. S. Geol. Survey 1882-1923, by

U. S. Bureau of Mines since 1924. Each volume contains a brief review of the mining activities in the

area for the year treated. Production statistics and

notes on the mining and milling operations are given.

Before 1905 the reports were not as accurate or complete as they have been since that time. From 1905 to

1925 they were prepared by V. C. Heil{e8 and from

1926 by C. N. Gerry. The reports of these men are

very complete and furnish a thorough picture of the

mining industry of the area.

PRINCIPAL FEATURES

The Oquirrh Mountains are composed of Paleozoic

sedimentary rocks and Tertiary igneous and sedimentary rocks. The bordering depressions are occupied by

Quaternary alluvium and lacustrine deposits. The

Paleozoic rocks include representatives of the Cambrian, Devonian, and Carboniferous systems. Of these,

the Cambrian is composed of 1,800 feet of limestone,

dolomite, shale, and quartzite; the Devonian, 185 feet

thick, is almost wholly dolomite; and the Carboniferous, over 20,000 feet thick, is dominantly limestone

and quartzite but includes subordinate amounts of

shale and dolomite. The Tertiary rocks include, in

addition to a negligible amount of conglomerate, monzonite porphyry, rhyolite, and latite intrusives and

latite and rhyoliteeffusives.

Detailed regional correlations' of these rocks is not

yet possible because of the lack of information about

many of the individually isolated ranges of western

Utah. General stratigraphic similarity seems to be

shown in the East Tintic and Canyon Ranges 5 and in

the Wasatch Range,6 and an attempt is made to extend

such correlations as seem at present warranted.

The geologic structure of the Oquirrh Mountains is

similar to that of many other ranges in the Basin and

Range province. The strata have been thrown into

open folds and later cut at a narrow angle by normal

faults, to the displacement along which is due the

present existence of the mountains. In the southern

part of the range two large asymmetric anticlines, the

Ophir anticline and the Long Ridge-Middle Canyon

anticline, which are separated by the Pole CanyonSelkirk Canyon syncline, are the most prominent folds.

• Loughlin, G. F., Geology and ore deposits of the Tintic mining district, Utah: U. S. Geol. Suryey Prof. Paper 107, p. 21, 1919; A reconnaissance in the Canyon Range, west-central Utah: U. S. Geol. Survey

Prof. Paper 90, pp. 53-58, 1914.

• Calkins, F. C., in Butler, B. S., and others, The ore deposits of

Utah: U. S. Geol. Survey Prof. Paper 111, pp. 233-239, 1920.

The southern continuation of the Bingham syncline

borders the Long Ridge-Middle Canyon anticline on

the east and extends farther south in the Lake Mountains,. just outside this area, where it is the dominant

structural feature.

The principal normal faults of the part of the

range discussed in the present report border the

mountains on the west in an en echelon series running

about N. 30° W. from the area south of Mercur

Canyon to the north edge of the Stockton quadrangle.

Along most of this distance the faults are clearly indicated by stratigraphic displacement, distillct brecciation, and gouge, as well as notable topographic discordance on the two sides. The fact that the evidence

for the normal faulting is stratigraphic and structural as well as physiographic is of added interest in

view of the objections repeatedly made against the

validity of the argument for " Basin Range structure"

from physiography alone.

Other major faults occur in Ophir Canyon, where

the dominant trends are east-west, and in Dry Canyon,

where the somewhat complex faults trend mainly

north, but neither of these groups of faults belong to

the Basin Range system. Minor faults are present

elsewhere almost throughout the quadrangles, but

they are of slight importance structually as compared

to the folds, although of prime economic importance.

SEDIMENTARY ROCKS

The sedimentary rocks exposed within the Stockton

and Fairfield quadrangles have a total thicloiess of at

least 21,000feet, 01' about 4 miles. They include Cambrian, Devonian, Mississippian, Pennsylvanian, Tertiary, and Quaternary strata. Unconformities occur

below the Devonian, below the Mississippian, possibly below the Pennsylvanian, below the Tertiary, and

below the Quaternary rocks.

The stratigraphy of the Ophir district has been previously discussed by Wichman 7 and Olmstead,S who

made commendable efforts to correlate the rocks with

the section established at Tintic by Loughlin.9 In

this work they were severely handicapped by the lack

of paleontologic assistance and were forced to depend

entirely upon lithologic resemblances between the two

areas. Paleontologic information has revealed remarkable differences in the stratigraphy of the two

areas, so that the writer has felt impelled to apply

new names to several units rather than to extend the

Tintic nClmenclatureto this area. As a result it has

7 Wichman, F. 1\1.,The Ophir mining district, Utah: Eng. and :Min.

Jour., vol. 110, pp. 560-563, 1920.

8 Olmstead, S. G., Economic geology of the Ophir mining district,

Utah: Econ. Geology, yolo 16, pp. 433-456, 1921.

• Loughlin, G. F., The geology and ore deposits of the Tintic mining

district, Utah: U. S. Geol. Survey Prof. Paper 107, pp. 23-41, 1919.
been necessary to differ with Olmstead and ·Wichman

011 several points, as well as with some suggestions

offered by Loughlin in the Tintic report.

The stratigraphy of the area, as presented in detail

in succeeding pages, is summarized in the following

table:

Quaternary (Recent and

Pleistocene) .

Alluvial and lacustrine deposits, including Lake

Bonneville beds (of Wisconsin and probably preWisconsin age).

Unconsolidated. or only partly consolidated gravel, sand,

and silt, overlain in the lower areas by lake silt and

gravel beaches of Lake Bonneville. Some glacial fill of

probable Wisconsin age in the high mountains. Some

fanglomerate and stream gravel.of post-Lake Bonneville

age.

200+ I Fine conglomerate and coarse grit, unfossiliferous.

Unconformity

Tertiary (Miocene or Oligocene).

Unconformity

I

Interbedded lenticular quartzite and limest<;>ne,becoming

Oquirrh formation. 15,000+ more quartzitic toward the top. With very subordinate

I

thin beds of shale and dolomite. Top not exposed in this

area.

I

I Dominantly shale with some thin beds of limestone and, in

I Manning Canyon shale.

i

1,140± the lower half, 2 fairly persistent quartzite beds. The I

I

, portion above the upper quartzite is Pennsylvanian; the

I

i portion below it, upper Mississippian.

!

I

i Light-blue limestone, with thin partings of reddish-weath- ,

"Great Blue" limestone.

, ering shale and with an 85-foot bed of black carboI I

3,600 naceous shale, the Long Trail shale member, about 500

feet above the base.

I !

Humbug formation.

I

Interbedded limestontj and lenticular sandstone and quartz650 ite in beds as much as 100 feet thick but ordinarily from

2 to 10 feet thick.

I

I

Blue-gray cherty limestone in beds averaging about 2 feet

Deseret limestone. 650 thick, with a 6 to 8 foot bed of phosphatic shale at the

base. ---. ----I -----

Highly fossiliferous blue-gray limestone, rather thin

Madison limestone. 460 hedded at the base, more massive and cherty toward

the top.

Coarsely crystalline gray dolomite, weathering dark gray;

Jefferson (?) dolomite. 185 one massive bed containing conspicuous white calcite

fossil casts.

Thick-bedded light-gray dolomite, with some dark-gray

Lynch dolomite. 825-1,000 dolomite spangled with short white rods in the lower

part and with a few limestone beds, especially in the

I

lower half.

Bowman limestone.

I

Mottled shaly limestones, intraformational conglomerate,

280 and oolitic limestone, with a shaly member about 35

feet thick at the base.

Unconformity

Middle (?) Devonian.

Unconformity

650 .1 Gray mottled limestone in thin beds with shaly partings

some oolite toward the top.

------ ----

Micaceous shales, sandy toward the base, becoming less

320 so upward and containing several beds of mottledshaly

limestone.

Thick-bedded cross-bedded white quartzite weathering

with a rusty surface. Becomes shaly toward the top

and grades into the overlying Ophir formation.

CAMBRIAN SYSTEM

LOWER OAMBRIAN SERIES

III only two small areas northwest of the town of

Ophir, in the gulches on both sides of the spur in

which is situated the portal of the old Ophir Hill

Consolidated mine. In these gulches the quartzite

stands in almost vertical cliffs, above which are the

more gentle slopes of the Ophir formation.

TINTlC QUARTZITE

Distribution ami topographic ewpre88ion.-The oldest formation exposed within the Stockton and Fairfield quadrangles is the Tintic quartzite. It crops out
Stratif!l'aphy.-The lowest exposures of the Tintic

quartzite are cut by the Canyon fault, on the south

side of which the rocks have been relatively depressed

so that the stratigraphic base of the formation is

concealed.

The formation is almost wholly quartzite, white on

fresh fracture, but with a rusty weathered surface.

Its individual beds range in thickqess from perhaps

half an inch to about 6 feet; the average bed is about

1 foot thick. Thin argillaceous layers which are now

somewhat schistose occur as partings and increase in

both number and thickness toward the top, where, by

their final dominance over the quartzite, the transition

to the sandy shale of the Ophir formation is effected.

The beds are very irregular. Cross-bedding is

prominent in all the quartzite beds. No constancy of

direction of cross-bedding is apparent, complete reversal of direction being seen in a number of adjoining beds. Numerous joints and small faults oriented

in many directions are visible in the cliffs, and along

many of these fissures secondary silica has been deposited, making a network of quartz veins. None of

the small faults can be traced beyond the quartzite

outcrop, the displacements being taken up in the overlying Ophir formation by folding.

In hand specimens the rock is seen to consist almost

entirely of subrounded to well-rounded quartz grains,

poorly sorted and of very irregular sizes, ranging from

perhaps 0.1 millimeter to 1 centimeter in diameter,

~houghthis maximum is exceptional. The rock is very

thoroughly cemented, except for a few small cavities

in which the grains show only slight enlargement with

silica and are stained by limonite, which produces a

pock-marked effect. Except in the very subordinate

schistose layers, bedding laminations are practically

invisible in the hand specimen.

The microscope shows the medium-grained quartzite

to consist of fairly well-rounded quartz grains, most of

which carry numerous minute inclusions of some

highly refracting mineral, possibly rutile. The original outlines' of the grains are faintly marked by

brownish-iron stains, beyond which secondary enlargement has extended till the grains mutually interfere,

producing a mosaic pattern when seen with crossed

nicols. Some muscovite and chlorite have been developed. At a period subsequent to cementation the

rock was sheared, and the brecciated silica along the

shear planes has recrystallized into linear series of

unoriented fine grains.

Coarser-grained specimens show less grain enlargement and apparently a greater development of muscovite than the medium-grained rock. In some of them

the muscovite plates are visible to the naked eye, a

feature which is also shown by the fine-grained quartzite that grades into the shale of the overlying Ophir

formation. The finer-grained specimens examined

also carry conspicuous quantities of angular grains of

microcline, a mineral only sparsely represented in the

coarser-grained specimens.

The interpretation that the Tintic quartzite grades

into the Ophir formation is decidedly at variance with

that advanced by Wichman/o who believed that there

was a surface of marked erosional unconformity with

a relief of at least 300 feet between the Tintic quartzite and the Ophir formation. According to Wichman's interpretation, the narrowing of the exposed

part of the Ophir formation is due to this unconformity, but the writer believes that this narrowing is

entirely explained by structural features of much later

origin-the Ophir anticline and the Canyon fault,

through the conjunction of which the crescentic outcrop of the Ophir formation has developed. The

lithology of the beds just above and below the contact

strongly supports the view of the conformity of the

two formations. Olmstead 11 differed with his coworker, Wichman, on this point, for he states that the

two formations are conformable. As the transition

zone between continuous quartzite and continuous

shale is 30 to 40 feet thick, the selection of a boundary

between the two formations is quite arbitrary. In surface mapping the boundary was drawn at the base of

the lowest thick bed of sandy shale, which, in the gulch

below the old Wild Delirium, mine, is 5 feet thick.

This choice of boundary limits the exposed Tintic

quartzite to a thickness of 294 feet and throws perhaps most of the transition zone into the Ophir formation. Comparison of the section as exposed on the

surface with that penetrated on the tunnel level of the

old Ophir Hill Consolidated mine suggests that for underground work the boundary would be better placed

some 30 feet higher, for underground the affinities of

most of the transition beds appear to lie with the

quartzite rather than with the shale. However, the

underground exposures are so few that the location of

the boundary is believed to be better based upon the'

surface information.

Oorrelation.-Although none of the basal Paleozoic

quartzite formations in Utah contain fossils, it seems

fairly certain that the quartzite at Ophir is to be correlated with the Tintic quartzite of the Tintic Range,

30 miles to the south, and with the Cambrian quartzites

of the Wasatch and House Ranges, as all these quartzites lie conformably beneath a shale formation which

carries fossils that have been referred to Lower and

Middle Cambrian time.

10 Wichman, F. M., The Ophir mining district, Utah: Eng. and Min.

Jour., vol. 110, pp. 561-563, 1920.

11 Olmstead, S. G.,Economlc geology of the Ophir mining district,

Utah: Econ. Geology, vol. 16, p. 439, 1921.
Hartmann limestone.

Section crossed by small fault with throw of less than 4

feet.

Ophir formation:

1. Interbedded limestone and shale, highly altered

and bleached, containing epidote and pyrite__ 4

2. Dark-gray shale, mottled with brown on fresh

surfaces and weathering uniformly dark

brown, fine grained, not sandy, blocky and

highly jointed, with no marked tendency to

split along bedding surfaces_________________ 62

3. Dense blue-gray limestone, mottled by irregular

bands of shale. The shale layers range from

% inch to 1 inch in thickness and weather

dark brown; the limestone, in layers of l/5

inch to 2 inches, weathers dark blue-gray,

giving a streaked appearance to the outcrop.

These mottled beds range from 6 inches to 2

feet in thickness and are separated by wavy

bedding surfaces and broken by numerous

faults of small throw. This member includes

part or all of the" Big vein" and "Top vein"

of the Ophir Hill mine______________________ 41

4. Light-gray shale, poorly laminated, which

weathers almost white except along fractures,

where it is stained brown. The shale is practically free from mica, very blocky, and with

very poor lamination. Some layers are decidedly limy 32

5. White-weathering shale, light gray on fresh fracture, poorly exposed, poorly bedded, with only

tine particles of mica and no tendency to

schistosity. The" Middle vein" of the Ophir

Hill mine is probably represented in this member________________________________________ 26

6. Concealed, the "Blue vein" and "Copper vein"

of the Ophir Hill mine are doubtless represented in this member______________________ 54

Within this member, 70 feet east of the line

of the section and with exact stratigraphic

location indeterminate, are the following

exposures:

Poorly bedded, iron-stained shale__ 4

Poorly exposed gossan; presumably

represents alteration of a replaced limestone bed____________ 17

Pyritized and somewhat silicified

limestone 3

7. Thinly laminated, somewhat sandy, very light

greenish-gray shale which weathers practically

white with some rusty blotches. The shale

is blocky, with only a small amount of mica.

Grades downward into No. 8________________ 40

8. Chiefly very light greenish-gray, white-weathering, thinly laminated blocky shale with many

interbedded lenses of white quartzite. The

quartzite lenses range from 1inch to 1foot in

thickness but are everywhere subordinate to

the shale. Grades downward into No. 9_____ 12

9. Thinly ,lamina ted quartzitic sha Ie. blocky,

closely. jointed, breaking into angular blocks

:Ih inch to 2 inches on a side_________________ 18

Ophir fonnation-Continued. Feet

10. Quartzose mica schist similar to bed 12 and

quartzite like the Tintic quartzite, alternating

in layers fro1111,4 inch to 2 inches thick. The

member is highly quartzitic but has a laminated aspect Iil_e a typical schisL____________ 20

11. Quartzite, very light gray, identical in appearance with Tintic quartzite, in one bed_______ 5

12. Highly quartzose, thinly laminated greenishgray, brown-weathering schist. The bedding

surfaces are greatly slickensided, with a considerable development of mica. The chief constituent is fine-grained quartz. Individual

laminae of schist range from nr to 14 inch in

thickness. Sporadic quartzite lenses as much

as 2 inches thick are presenL_______________ 5l/2

Conformable contact.

'l'intic quartzite. 319%

The limestone beds of the Ophir formation, which

are of paramount economic importance, have been

thoroughly investigated in the workings of the Ophir

Hill Consolidated Mining Co., whose engineer, E. S.

Bowman, kindly furnished the following summary of

the section as it appears in the mine workings:

Unnamed limestone, only slightly productive _

Shale _

"Top vein" limestone _

Parting, shaly _

"Big vein" limestone _

Shale, approximately _

"Middle vein" limestone _

Shale, approximately _

"Copper vein" limestone _

Parting, shaly limestone _

"Blue vein" limestone _

Shale _

Quartzitic shale _

l~eet

5-8

60

5-8

2

20-40

25

10-14

25

8

1112- 2

6

57

44%

299%

The two units at the base of this section were measured by the writer.

The limestones of the Ophir formation are, as a rule,

poorly exposed on the surface, and they are so much

altered in most of the mining exposures that it is

difficult to get any good idea of their unaltered appearance. However, in the "7%" drift of the old

Ophir Hill Consolidated mine apparently unaltered

limestone of the " Copper vein," remote from any ore

body, is seen. This limestone is dense, very dark gray,

and very faintly mottled. The mottling seems to be

due to variations in the silt content of the various

layers and slightly to the carbon content. Toward the

ore body the mottling is more and more striking, with

the development of metamorphic minerals and oxidation or removal of the carbon content. These changes

are more fully described in the section of this report

dealing with metamorphism and are mentioned here

merely to call attention to the fact that the banded and

mottled crystalline rock (" zebra rock") which is com-
VIEW LOOKING NORTH AND NORTHEAST FROM A POINT ON THE DRY CANYON-OPHIR CANYON DIVIDE ABOUT A QUARTER OF A MILE SOUTHWEST OF MINERAL

MONUMENT NO. 4

a, Hornfels ledge at base of Bowman limestone; h, Lynch dolomite; c, Jefferson (?) dolomite; d, Madison limestone; e, cherty ledge at top of Madison limestone; C, tramway station of Cliff (Buckhorn) mine; g, upper

tunnel of Cliff mine; h, Chicago incline; i, Hidden Treasure incline.

monly seen near the edges of the ore bodies owes its

striking color banding to changes connected with o.re

deposition, not to its original character.

The microscope reveals a little silt but almost no

constituent of importance, other than calcite, in the

limestone. Much of the mica of the shales of the

upper part of the formation is seen to have a haphazard arrangement, though lamination is pronounced.

This lack of parallelism among the mica individuals

is in distinct contrast to their parallel leaf-like

arrangement in the schist in the lower part of the

formation, but the possibility that the upper beds

where examined may have undergone hydrothermal

alteration, with the resultant development of the haphazard mica (or sericite) plates renders the textural

differences of questionable significance. As nearly as

can be determined, either in the field or under the

microscope, the schistosity is parallel to the bedding

in these lower layers. It seems probable that this

parallelism resulted from differential tangential movements in the lower beds of the Ophir formation in

response to the folding of the Ophir anticline. This

adjustment presumably produced the proper stress

conditions for growth of the mica plates, whose orientation was doubtless governed in part by the resolution

of the forces of compression normal to and parallel to

the bedding and perhaps in part by greater permeability of the rock in this direction. That the schistosity is hardly to .be attributed to pure load metamorphism seems very probable, as stress conditions,

due to load above, can not have been appreciably more

rigorous in the lower than in the upper part of the

formation, which likewise must have been buried under fully 20,000 feet of rock during this folding. This

conception of the cause of the schistosity is supported

by the slickensided condition of the lower, more

schistose beds as contrasted with the upper shaly ones.

The area of outcrop of the Ophir formation is very

small at Ophir, and opportunities for observation are

correspondingly meager; but even so, its variations

seem considerable, a characteristic of the formation

elsewhere, as is pointed out by Loughlin 21 for the

Tintic district. The notable variations in the thickness of the several limestone beds indicated in the

section furnished by Mr. Bowman are not due entirely

to variations in the thickness of minable ore, but in a

considerable degree, at least, to actual local differences

in the beds themselves.

The determination of the upper contact of the

Ophir formation, like that of the lower, is arbitrary,

though there is considerably less transitional material

at the top than at the bottom. The boundary between

this formation and the Hartmann limestone is drawn

at the top of the highest shale bed in this part of the

section. It is probable that over a wider area this

boundary would prove to be of variable horizon, as

the shale probably lenses in and out through a greater

or less stratigraphic interval, but in the small exposure of Ophir Canyon no notable variation was seen.

Age and correlation.-Fossils from the Ophir formation, collected from schistose beds less than 50 feet

above the base, were submitted to Dr. C. E. Resser, of

the Smithsonian Institution, who reports as follows:

Localities 4 and 6 contain a Middle Cambrian fauna which

is characterized by Dolichometopu8 prod~wtu8. Col'ection 5

seems to have a specimen of Neolenu8. All of this Ophir shale

group is represented in the near-by Wasatch and elsewhere,

occupying a position below the middle of the Middle Cambrian.

Walcott 22lists the following fossils from the Ophir

formation at Ophir:

About 75 feet above the quarizitic sandstones of the

Cambrian:

Obolus (Westonia) ella.

Concretionary limestone about 100 feet above the quartzitic

sandstones of the Cambrian:

Mif'romitra sp.

Micromitra (Paterina) labradorica utahensis.

Obolus (Westonia) ella.

Olenoides(?).

These are all assigned to the Middle Cambrian.

However, in discussing the Cambrian of Utah, Walcott 23stated: .

The section in the Oquirrh Range above Ophir City has a

quartzite at the base with shale above it carrying Lingulella

ella, Olenellu8 gilberti, and Bath,yuNscu8 producta, as determined by the collections brought in by the Wheeler Survey. It

is probable, however, that as in the case of the Big Cottonwood

section, Olenellu8 gilberti occurs at the base of the shale, and

the other two species at a higher horizon.

In this paper, as in other publications, 'Walcott restricted Olenellu8 to the Lower Cambrian. This restriction has been questioned by Ulrich 24 and by

Burling,25 though Burling agrees with 'Valcott in assigning the lOlwerpart of the Ophir formation to the

Lower Cambrian. However, later stud.y by 1Valcott 26

of the Albertella fauna (upon which Burling's question was based) failed to convince him that Olenellug

has been yet found at any horizons stratigraphically

above Albertella. He accordingly did not relinquish

his position that the presence of Olenellus is alone a

sufficient criterion for ascribing beds to the Lower

Cambrian.

22 Walcott, C. D.• Cambrian Brachiopoda: U. s. Geol. Survey Mon.

51, pt. 1, pp. 164-165, 261, 1912.

asWalcott, C. D., Correlation papers-Cambrian: U. S. Geol. Survey

Bull. 81, pp. 319-320, 1891.

.< Ulrich, E. 0., Revision of the Paleozoic system&: Geol. Soc. America BUll., vol. 22, pp. 619-620, 1911.

.5 Burling, L. D., Early Cambrian stratigraphy in the North American

Cordillera, with discussion of Alberte/la and related faunas: Canada

Geol. Survey Mus. Bull. 2, pp. 113, 128--129, 1914.

••Walcott, C. D., The Albertella fauna in British Columbia and

Montana: Smithsonian :Misc.CoIl., vol. 67, No.2, pp. 9-60, 1917.
On this basis, the Ophir formation is in part Lower

Cambrian and in part Middle Cambrian in age. Diligent search during this survey failed to reveal any

specimens of Olenellus, so that it is impossible to say

how much is Lower and how much Middle Cambrian.

The fossils ascribed to the Middle Cambrian by Doctor

Resser were cOtllectedwithin 50 feet of the base of the

formation, so that if the Lower Cambrian is present it

includes less than this thickness of Ophir beds. Careful search failed to reveal any sharp lithologic change

or any unconformity within this interval. The schistose material discussed above extends higher than this,

so that the absence of schistosity in the topmost part

of the formation and its presence toward the base can

not be considered evidence of a significant difference

in the age of these beds. Accordingly, either sedimentation was here continuous between Lower and Middle

Cambrian time, or Olenellus survived into the Middle

Cambrian, as was stated by Ulrich 27to be true in the

Appalachian region. The only other possible interpretation is that an unconfoiI'mity really is present but

£scaped observation. If so it is not marked by notable

erosion, angular discordance, or sharp lithologic differences, and the writer believes it exceedingly improbable that one exists.

The rocks here included in the Ophir formation

were correlated with the shale just above the Cambrian

quartzite of the Wasatch Range by Emmons,28 and

this correlation was accepted by Walcott.29 Walcott

correlated it further with the shale at the top of the

Cambrian quartzite in the Highland Range, Nevada;

with that at the top of the Prospect Mountain quartzite in the Eureka district, central Nevada; and with

the lowest shale of the House Range, Utah. These

correlations he later modified in some details 30 as

more thorough studies were made. Burling 31 gives

an excellent summary of the correlations made by

Walcott up to 1908, laying great stress on the presence

of the two faunal zones-the Olenell'U!8gilberti zone

and the BathyurisC1J)Jproducta zone. This summary

presents the paleontologic results, which have not

since been questioned. Stratigraphic and lithologic

variations that were originally thought to be slight in

this part of the section over wide areas in Utah,

Idaho, and Nevada have since proved to be more complex,32so that formation names are not to be extended

!7 Ulrich, E. 0., op. cit., pp. 619-620.

osEmmons, S. F., Descriptive geology: U. S. Geol. Exp!. 40th Par.

Rept., vol. 2, p. 444, 1877.

••Walcott, C. D., Cambrian faunas of North America: U. S. Geol.

Survey Bull. 30, pp. 39-40, 1886.

••Walcott, C. D., Cambrian sections of the Cordllleran area: Smithsonian Misc. Coil., vo!. 53, No.5, pp. 171-185, 1908.

81 Burling, L. D., op. cit., pp. 120-125.

•• See especially Nolan, T. B., Geology and ore deposits of the Gold

Hlll quadrangle, Utah: U. S. Geol. Survey Prof. Paper (in preparation). Westgate, L. G., and Knopf, Adolph, Geology of Pioche, Nev.,

and vicinity: Am, Inst. Min. and Met. Eng. Tech. Paper 1647, I, 1927;

Geology and ore deposits of the Pioche district, Nev.: U. S. Goo!.

Survey Prof. Paper 171, 1932.

with as much confidence as the paleontologi~ correlations. Such correlations as seem justified from the

evidence are indicated in Figures 2 and 3. The term

Ophir formation, from the locality here described,

was proposed for these beds by B. S. Butler.33 It has

been extended by Loughlin 34to the Tintic district,

and the formation has been identified by Calkins 31

in the Cottonwood district.

Distribution and topographio ewpression.-Resting

conformably upon the Ophir formation is the formation here named Hartmann limestone, from its excellent exposures on the west side of Hartmann Gulch

(sometimes called Graveyard Gulch), just north of

Ophir. It crops out in the north wall of Ophir Canyon from the large gulch that descends the southeast

flank of Dry Mountain about a mile due west of Ophir,

where it is cut off by a fault on the west, to Hartmann

Gulch, on the east side of which it is cut off and

dropped out of sight by the northeastward-trending

branch of the Canyon fault. It is exposed nowhere

else within these quadrangles.

In this area the formation makes a steep slope, clad

rather thickly with scrub oaks and mountain mahogany.

Stratigraphy.-The boundary between the Ophir

formation and the Hartmann limestone is an arbitrary

one, the transition from the shale and limestone of the

Ophir to the uninterrupted limestone sequence of the

Hartmann being somewhat gradual. No evidence of

any depositional hiatus between them was detected,

and the boundary was' placed at the top of the highest

observed shale bed, throwing all the shales into the

Ophir formation.

The Hartmann formation consists dominantly of

limestone, banded with mudstone material, which is

distributed in a peculiar manner so that the weathered

surfaces of the limestones are irregularly mottled with

light gray, buff, and brown. Some of the mudstone

bands are parallel to the bedding and are connected at

closely spaced intervals by streaks of the same material

normal to the bedding and suggestive of filled mud

cracks. Another group of strata in the formation has

similar mudstone arranged in extremely sinuous, bulbous, and involved patterns, giving the impression of

filled worm borings. Still another type shows rounded

biscuit-shaped masses of mudstone of a pseudoconcretionary aspect, connected, at least in part, by thin

streaks of the same material. Many of these struc-

••Butler, B. S., and others, The ore deposits of Utah: U. S. Geol.

Survey Prof. Paper 111, pp. 79 et seq., 1920. The use of the term in

many of the areas farther west in Utah, as advocated by Butler, is

believed to be at present premature, in view of the detailed work of

Westgate and Nolan, cited above.

••Loughlin, G. F., Geology and ore deposits of the Tintic mining

district, Utah: U. S. Geol. Survey Prof. Paper 107, pp. 25 et seg., 1919.

•• Calkins, F. C., oral communication.
tures seem explicable as those of edgewise conglomerates or as filled worm tubes, but no adequate explanation of many of the other types occurs to the writer.

The mottling is so definite, however, and so widespread in the lower Paleozoic section of much of Utah

that it is of great value in stratigraphic work. The

Cambrian of the 'Vasatch Mountains near Salt Lake

City and in the Cottonwood Canyon section, the Cambrian and Ordovician of the Tintic district, and most

of the early Paleozoic of the Deep Creek Range 36 are

all characterized by similar mottling. Typical examples are illustrated in Plate 4. The following section

is a continuation of the section of the Ophir formation

given on page 10.

Eeotion of Hartmann limestone, on spur a1JoooWild Delirium

mine

.Bowman limestone; thick brown-weathering pyritized

hornfels at base.

Apparent conformity.

Hartmann limestone: Feet

1. Limestone, blue mottled, crystalline to dense,

containing round black spots about % inch in

diameter and irregular lumpy partings of buffweathering mudstone. Locally oolitic, carrying black oolites about n inch in diameter in

a gray shaly matrix. Bedding irregular, with

wavy surfaces; beds range from 2 inches to 5

feet in thickness~___________________________ 31

2. Limestone, dark and light gray, sandy and

oolitic, in beds about 2 feet thick. Poorly

exposed ~----________________________ 21

3. Concealed; probably limestone_________________ 39

4. Oolitic limestone, like No. 2.._________________ 6

5. Limestone, dark blue-gray, very irregularly mot·

tled with mudstone, which weathers white

through buff to brown. The mudstone partings are very irregular but are spaced from

% inch to 2 inches apart and range between

% and 112 inch in thickness. The banding is

pronounced on general view but is not particularly noticeable in hand specimens. Bedding massive, chiefly in beds 8 to 10 feet thick_ 107

~. Limel!ltone, dense, gray, and greenish-gray mudstone, weathering brown, poorly bedded. The

mudstone shows slickensides and silicification.

The limestone carries irregular dark-gray

blebs, some of which are vermicular. The

member forms a ledge and weathers light

gray as a whole____________________________ 3

7. Concealed; probably limestone, mottled with

mudstone like No. 8_________________________ 38

:8. Limestone, dark blue, weathering lighter bluegray, in beds % inch to 1% inches thick separated by butT·to cream weathering sandstone

in layers 1fs to % inch thick. Sparsely fossiliferous______________________________________ 102

9. Limestone, light blue-gray, fine grained, somewhat cross-bedded, banded with brown-weathering mudstone, which' locally shows "contact" minerals. Forms strong, persistent

ledge_______________________________________ 6

Hartmann limestone--Continued.

10. Poorly exposed; irregularly bedded limestone _

11. Limestone, mottled somewhat with sandstone.

Average bedding 2 inches to 1 foot thick.

The limestone carries numerous black vermicular marks % to 14 inch in diameter and as

much as 1% inches long, arranged entirely

without system. These markings are now

composed each of a single calcite crystaL _

12. Limestone, average bed about 2 inches thick.

Crystalline locally, mottled with mudstone.

Occasional trilobite remains occur. Upper

part poorly exposed _

Fault crosses section, and mine developments

show that 40 feet of beds are here lost to view _

13. Limestone, dark blue-gray on fresh fracture,

weathering light gray, in layers % to 3 inches

thick, mottled with mudstone in layers % to

% inch thick, with tendency to follow the bedding, which weather buff. Weathers into beds

from 1 to 4 feet thick, broken by joints into

large blocks _

Transitional boundary.

OPhir formation: Interbedded limestone and shale.

Feet

74

Microscopic examination reveals no unusual features of sedimentary origin, the banding being apparently due merely to variations in proportions of silty

matter. No dolomite was detected in this formation.

The upper limit of the Hartmann limestone is taken

at the base of a conspicuous thick brown-weathering

hornfels ledge that crops out in a roughly semicircular arc around the exposures of the older rocks.

The contact is apparently conformable and is discussed further in treating the Bowman limestone, of

which this ledge is considered the basal member.

Age ana c01'relatim.-Fossils are not numerous in

the Hartmann limestone, but scant faunules have been

collected at several horizons within it. The collections made by the writer have been reported on as

follows by Dr. C. E. Resser:

Collection F1: About 110 feet above base of Hartmann limestone, on west side of Hartmann Gulch, Ophir Canyon.

Collection F2: About 310 feet above collection F1, in Hartmann limestone.

Collections F1 and F2 are Middle Cambrian, containing well·

known but largely undescribed faunas. F1 contains Dorypyge;

F2 represents the common blue Middle Cambrian limestone as

it occurs in the House Range.

Wichman 37 correlates the strata here included in the

Hartmann limestone with the Teutonic and Dagmar

limestones as recognized by Loughlin 38 in the Tintic

mining district. In this correlation he was followed

by Olmstead.39 The writer is unwilling to attempt so

close a correlation between districts so widely sepa-

'" Wichman, F. M., The Ophir mining district, Utah: Eng. and Min.

Jour., vol. 110, pp. 560-563, 1920.

•• Loughlin, G. F., Geology and ore deposits of the Tintic mining district, Utah: U. S. Gool. Survey Prof. Paper 107, pp. 27-28, 1919.

•• Olmstead, S. G., Economic geology of the Ophir mining district:

Econ. Geology, vol. 16, p. 440, 1921.
rated (30 miles) as Ophir and Tintic. There is little

doubt, however, that the lower part of the Hartmann

limestone as here described is equivalent to the lower

part of the Teutonic limestone of Tintic. The very

remarkable lithology of the Dagmar limestone of that

district finds no counterpart in Ophir Canyon, however, and as the ages of these several formations can

not be differentiated from the paleontologic evidence

at hand and the original distinction of the Dagmar is

based solely on its peculiar lithology, the extension of

the term seems unacceptable. The writer was able to

observe no really mappable division of the strata here

grouped. It is true that oolites and edgewise conglomerates begin to come in toward the top, but these

are not persistent features so far as observed, and no

adequate basis for a division of the unit was found.

The Hartmann limestone is probably to be correlated, at least in part, with the Cambrian limestones

of the Cottonwood district of the Wasatch Mountains described by Calkins,40but no precise correlation

between these two areas seems warranted from the

information at hand, as the fossils from both districts

are few and not particularly good horizon markers.

Distribution and topographic empression.-Conform ably overlying the Hartmann limestone is a series

of mottled limestones and limy mudstones and shales,

the latter now found as hornfels, which crop out in a

rough arc in the wall of Ophir Canyon north of the

town. This formation is here called the Bowman

limestone, from its excellent exposures in BO'Nman

Gulch, northwest of Ophir. The outcrop is cut off on

the west by the Canyon fault in the gulch that descends southeastward from Dry Mountain, west of

Ophir. From this point its outcrop extends east arid

northeast to the lower buildings of the Cliff mine and

thence south and east to the east wall of Hartmann

Gulch, where it is again cut off by the Canyon fault.

A small area on the spurs between the Canyon fault

and the town of Ophir and within the town exposes

mottled limestone resembling this formation and so

shown on the map (pI. 12), but the upper boundary

of this formation is not distinctive, and it is possible

that these rocks correspond in horizon to the base of

the Lynch dolomite as mapped near the Cliff mine.

Stratigraphy.-The outcrop of the basal bed of the

formation is a prominent ledge almost throughout its

length. Its resistance to erosion is doubtless due to

its metamorphism from a limy shale to a massive

hornfels. The degree of metamorphism varies decidedly from place to place and from layer to layer

within the member at any given locality, so that some

•• Calkins, F. C., in Butler, B. S., and others, The ore deposits of

Utah: U. S. Geol. Survey Prof. Paper 111, pp. 236, 237, 1920.

limestone, some argillite, and some shaly dolomite are

found to make up portions of the unit. Its lithology

is illustrated in Plate 5, B. The alteration is described

in more detail in the section on metamorphism.

Above the hornfels member, which averages perhaps

35 feet in thickness, is a series of mottled shaly limestones, edgewise conglomerates, and oolite beds, the

limestones practically indistinguishable from the mass

of the Hartmann limestone and the conglomerates and

oolitic beds finding counterparts in the upper portion

of that formation. A typical example of the edgewise

conglomerate is illustrated in Plate 5, A. Argillaceous

layers, also in part altered to hornfels similar to the

basal bed, recur at several horizons in the limestone

but are subordinate in the formation as a whole.

The following section of the Bowman limestone represents its character where exposed on Lynch Ridge

just east of the lowest tunnel of the Cliff mine:

L~-nch dolomite: Dark blue-gray dolomite spangled with

rods of white calcite.

Conformable contact.

Bowman limestone: Feet

1. Dark blue-gray limestone, streaked with irregular

white crystalline calcite markings roughly parallel to the bedding, carrying sporadic nearly

black oolites and numerous scattered cylindrical rods of calcite. The beds of the member

range from 1 foot to 4 feet in thickness_______ 55

2. Concealed_____________________________________ 53

3. Poorly exposed limestone, dark bluish gray,

weathering light gray, mottled with shaly material in irregular and discontinuous layers.

'l.'he limestone beds range from ¥.! inch to 8

inches in thickness and average about 3 inches.

The shaly streaks hardly exceed % inch in

thickness and weather buff to brown. A few

oolitic layers occur___________________________ 28

4. Hornfels and magnesian argillite with subordinate limestone. Much pyrite occurs in the bed,

which has a greenish-gray cast on fresh fracture but weathers to a deep brown. Forms a

low ledge 8

5. Limestone like that in bed 3____________________ 8%

6. Somewhat shaly and metamorphosed limestone

and dolomite with some flat rouncled limestonepebble conglomerates of the intraformational

type. Some thin layers of unaltered limestone

occur 14

T. Limestone like that in bed 3, with prominent

dark-gray vermicular markings due to somewhat more carbonaceous material. These

markings range from -r.- to 1/1 inch in diameter

and are as much as 1 inch long. They seem to

show no general orientation. About 30 feet

above the base is a i-foot bed of "intraformational" limestone conglomerate. (See pI. 5,

A.) Similar beds occur 5 feet and 7 feet

higher. The top 15 feet is not well exposecL~ 70
Bowman limestone--Continued. Feet

8. Argillaceous limestone and limy argillite, containing considerable pyrite. Gray to greenish

gray on fresh fracture; weathers to a reddish

brown. "Contact minerals such as epidote

and garnet are plentiful, and the whole member

is now dominantly hornfels. Interbedded are a

number of layers of limestone conglomerate___ 41

277112

The upper boundary of the Bowman limestone is

difficult to draw. The normal limestones of the upper

strata pass gradually into a series of beds that vary

along the strike between limestone and dolomite. In

tracing a given bed it was observed to vary from

limestone to dolomite and back to limestone within 20

feet. In several sections measured within 200 yards of

one another the position of the lowest dolomite bed

varied over 80 feet stratigraphically, yet this was not a

feature related to any apparent mineralized fissures,

nor could the relation be ascribed to faulting or unconformity. Similar difficulty in fixing the lower boundary of the Lynch dolomite was experienced by the local

mining geologists and engineers, and it is believed by

them as well as the writer that the variation in the

position of the base is a sedimentary feature, not connected with unconformity or local strueture. No

boundary that would be everywhere satisfactory could

be established in the field. It is believed that the section measured on the backbone of Lynch Ridge east of

the Cliff mine probably carries dolomite as low stratigraphically as any other section in the district and ,

the boundary between the Bowman limestone and the

Lynch dolomite is here arbitrarily drawn at the base

of the lowest dolomite outcrop on that ridge.

The boundary as mapped shows only the approximate limit between limestone and dolomite. To show

the actuallim.it would be rather confusinO'than other-

• • I:>

~lse, as It passes up and down through a stratigraphic

mterval of well over 100 feet and its delineation would

introduce apparent structural complexities where none

exist. Accordingly, in a number of places rocks

mapped as part of the Lynch dolomite are quite as

pure limestones as any in the Hartmann or Bowman

but such limestones are nowhere very thick, nor i~

there any confusion as to their true position in the

section save possibly in the locality referred to above,

on the spurs south of the Canyon fault and between

it and the valley of Ophir Creek in the town of Ophir.

In the new shaft of the Ophir Hill Consolidated

Mi~ing Co., on the south side of Ophir Canyon, in

WhICh,as the beds are there practically horizontal

nearly their true thickness is revealed, the lowest dolo~

mite was penetrated at 150 feet below the adit and ,

the basal shale of the Bowman formation was bottomed at 510 feet. This interval, 360 feet, is over 80

feet greater than the one arrived at by the surface

measurements given above and seems clearly to point

to transition of dolomite to limestone at the base of

the Lynch dolomite in the interval between these

localities, such as was verified near the type section of

the Bowman limestone just discussed.

Age and correlation.-The rocks here included in

the Bowman limestone have been referred to the

Herkimer limestone of the Tintic district by Wichman.41 Olmstead 42 also included them in the Herkimer limestone, but his formation was apparently somewhat more inclusive than Wichman's or the present

writer's, for he gives a total thickness of 405 feet for

th: Herkimer, compared with 268 feet as given by

",Vlehman and 277 feet for the Bowman limestone as

given in this report. This discrepancy is doubtless

due, at least in part, to the variable position of

the boundary between limestone and dolomite above

referred to.

As is evident from Loughlin's 43 description of the

Herkimer limestone in its type locality, the Tintic district, it greatly resembles the Teutonic limestone of

that district-so closely, in fact, that WGreit not for

the intervening Dagmar limestone, of unique lithology,

the two would not have been differentiated. The

writer considers it highly probable that the rocks of

the Bowman limestone as here defined are at least in

part equivalent to a portion of the type Herkimer;

nevertheless he feels that the use of that name in the

area here described, predicated as it would be on the

recognition of a subjacent unit equivalent to the

Dagmar and an overlying ooe equivalent to the Blueb.ird dolomite, is not warranted. Useless multiplicatIOn of stratigraphic names is certainly to be deplored . ,

but the writer feels that too widespread correlation of

stratigraphic units that are primarily established for

local reasons on a merely lithologic basis is equally to

be avoided without rather conclusive evidence of their

equivalence.

A few poor collections of fossils were made from

this formation, upon which Doctor Ressel' reports as

follows:

Collection F3: E'rom limestone about 120 feet above the

base of the Bowman formation on Lynch Ridge.

Collection F14: From limestone about 240 feet above the

base of the Bowman formation on Lynch Ridge.

Collection F3 is Middle Cambrian, containing well known

but largely un described faunas. It contains Dorypyge. Collection F14 contains a strange trilobite, and guessing at its

age I would put it as upper Middle or lower Upper Cambrian.

o

<l Wichman. F. M.• op. cit., p. 560.

., Olmstead, S. G., op. cit., p. 440.

., Loughlin, G. F., op. cit. (Prof. Paper 107), p. 28.
Distribution and topograpMa ewpression.-Conformably overlying the Bowman limestone is a thick series

of dominantly massive gray dolomites here called

f

. ,. ,

r?m Its exposures on Lynch Ridge, the Lynch dolomIte. The Lynch dolomite crops out on the south

wall of Ophir Canyon southeast of Ophir, where it

forms much of the canyon wall from the old tailing

dumps a mile below the town to the baseball park.

On the north side of Ophir Creek the dolomite is

exposed in a belt extending from the baseball park to

the spur northeast of the Ophir Central shaft and

then curving successively northwest, west, and southwest around the outcrops of the older rocks. It forms

the divide between Dry and Ophir Canyons from a

p?int near the old Chicago mine to a point a short

dIstance west of the summit of Dry Mountain west of

Ophir. The Canyon fault here cuts the outcr~p off on

the south. The formation forms the southeast wall of

Dry Canyon from a point a short distance below the

buildings of the Hidden Treasure mine nearly to the

mouth.

~tratigraphy.-The lower beds of the Lynch dolomIte are apparently conformable upon the Bowman

limestone. As was stated in the description of the

Bowman limestone, the boundary is far from satisfactory. Rapid local changes, apparently unrelated to

fissures, occur within the lower beds of this unit so

that a given bed may change from limestone to d~lomite within less than 50 feet. Sections measured

within 100 yards along the strike and assuredly uncomplicated by faulting showed variations of more

than 80 feet in the stratigraphic position of the lowest

dolomite beds; To some extent this variability is

doubtless due to interfingering of dolomite and limestone lenses, but there is actual variation within individual beds also, as can be seen near Lynch Ridge east

of the Cliff mine. The lowest beds of dolomite on this

ridge when followed westward are seen to change to

limestone within 200 feet. Messrs. Hartmann and

~owman, of the .Ophir Hill Consolidated Mining Co.,

mformed the Writer that painstaking detailed work on

their part showed this to be a characteristic feature.

The present survey bears out their observations on

this point, as has been shown in the section describing

the Bowman limestone.

The lower part of the Lynch dolomite is an alternating series of limestone and dolomite but a short

distance above the base a rather unusu~l variety of

rock occurs. This is a dark steel-gray crystalline dolomite, :weathering almost black except for a spangling

of whIte rods and vermicular tubelike markings which

average perhaps one-sixteenth of an inch in diameter

and are a quarter to half an inch in length. The rock

is practically identical in appearance with the Bluebird dolomite of the Tintic district, and Bluebird is

the name locally applied to it. Unfortunately, so far

as accurate geologic mapping is concerned, the lithology is not limited to a single zone but occurs in zones

of varying thickness and stratigraphic position from

place to place. However, it is useful to the extent that

it marks a zone rather low in the dolomite series-in

some places the very base itself as in the Tintic dis-

. A '

trIct. hand specimen of this peculiar rock is illustrated in Plate 6, B.

The upper three-fourths of the Lynch dolomite is

composed of rather thick-bedded light-gray and darkgray dolomites, the former predominating, in somewhat massive beds which only exceptionally show thin

bedding. Distinctive beds are rare and probably discontinuous; at least careful studies failed to identify

any single horizon on both sides of Ophir Canyon.

Magnesian limestones occur here and there, but they

are decidedly subordinate. A finely laminated lightgray dolomite which weathers dull chalky white is

rather common in the formation and makes good local

marker beds. An example is illustrated in Plate 6, O.

The following section was measured on Lynch

Ridge east of the Cliff mine and is considered representative of the formation:

Sectwn of Lynch tZowmite east of aUff mine

[Strike N. 65° W.; dip 17° NE.]

Jefferson ( ?) dolomite: Thin limy sandstone at base.

Unconformity, showing slight irregularity but traced

with difficulty.

Lynch dolomite: Feet

1. Thin-bedded light-gray dolomite_______________ 23

2. Light-gray dolomite in beds, 4 to 10 feet thick,

forming very steep cliffs 374

3. Gray dolomite, in beds 3 to 4 feet thick' a

little magnesian limestone at the base ~__ 44

4. Dark-gray finely crystalline dolomite, in beds

ranging from 1 to 7 feet in thickness. Forms

a strong ledge, the top 1-foot bed of which is

conspicuously black_________________________ 19

5. Light-gray, very dense dolomite which is conspicuously white and finely banded on weathering. (See pl. 6, a.) 41h

6. Light-gray with subordinate dark-gray dense

dolomite -_______________________ 29

7. Blue-gray limestone with white shale partings.

Trilobite fragments were found in this member________________________________________ 571/2

8. Rather coarsely crystalline dark-gray dolomite,

which weathers nearly black. Contains short

rods of white dolomite spangled throughout,

which are probably organic remains of uncertainaffinities. Bluebird type. (Seep1.6,B.)_ 29

9. Alternating limestone and light-gray dolomite in

thin beds__________________________________ 11

10. Limestone, light blue-gray, mottled with irregular white-weathering shaly streaks___________ 15
Lynch dolomite--Con tin ued.

11. Light-gray dense dolomite, weathering almost

white and with finely streaked surfaces, like

~o. 5______________________________________ 5

12. Dense blue magnesian limestone mottled with

thin irregular streaks of white-weathering

shaly material_____________________________ 21

13. Gray mottled dolomite________________________ 15

14. Dark-gray dolomite, like bed 8; Bluebird type__ 20

15. Blocky siliceous shale_________________________ ¥.a

16. Dark-gray dolomite, like bed 8; Bluebird type__ 31

17. Poorly exposed blue mottled limestone__________ 18

18. Massive blue limestone mottled with light-gray

shaly material______________________________ 4%

19. Chert parting ~_______________ ~

20. Limestone, dark blue, streaked with a few thin

shaly streaks and with numerous vermicular

tubes of coarsely crystalline calcite. Poorly

exposed____________________________________ 35¥.a

21. Dark-blue limestone, dense and streaked with

thin discontiIiuous white shaly layers and carrying white rodlike markings like the Bluebird type of dolomite_______________________ 64¥.a

22. Dark-gray dolomite like bed 8; Bluebird type____ 6

Conformable contact. 8271,4

Bowman limestone: Dark blue-gray limestone, streaked

with irregular white crystalline calcite markings

roughly parallel to the bedding, carrying sporadic

nearly black oolites and numerous scattered cylindrical

rods of calcite.

The Lynch dolomite is well exposed on the south

side of Ophir Canyon, and a section was measured

here from the portal of the new Ophir Hill tunnel to

the base of the Jefferson (?) dolomite about half a

mile below the town. Owing to the Lion Hill fault it

is impossible to get a complete section directly south

of the Ophir Hill portal on the anticlinal axis, and the

measurement as made is doubtless not very exact, as

ehanging dips and slight uncertainties in stratigraphic tracing as well as the steep slopes with many

low vertical cliffs that were encountered all hindered

accurate work. This measurement gave approximately

900 feet as the thickness of Lynch dolomite exposed.

Dolomite was found in the new Ophir Hill shaft to

depths of about 150 feet, which would give a total of

1,050 feet of Lynch dolomite on the south side of the

canyon as compared with 827 feet on the north side a

difference of over 200 feet in less than 1 mile. Ev~n

when the inaccuracies of compass and tape surveys are

taken into account, this difference seems to indicate

considerable lateral' variation of the formation. This

variation may be in large part due merely to lithologic

change, but as there is an uncomformity at the top of

the formation, it seems not unreasonable to ascribe

some of the changes to differential erosion in preDevonian time.

The upper limit of the Lynch dolomite is put at the

base of a thin sandstone bed that separates beds of

very similar overlying dolomites, which, however,

carry a Devonian fauna, whereas the Lynch dolomite

is of Upper and Middle Cambrian age.

Age and correWiio'fb.-A single collection of fossils

was made from the Lynch dolomite, at a horizon about

280 feet from the base on Lynch Ridge. This collection was submitted to Dr. C. E. Resser for identification, and he reports as follows:

Locality F16, containing numerous Hyolithes, would seem to

be Upper Cambrian, but that is not certain.

Correlation of the dolomite section at Ophir with

that at Tintic is very tempting, owing to the remarkable similarity of individual rock types in the two districts. There is undeniably a strong resemblance between many dolomite beds of the Ophir district-for

example, Nos. 8, 14, 16, and 22 of the above sectionand the Bluebird dolomite at Tintic. However, at

Ophir these beds do not occur in thick sections of uniform lithology as they do at Tintic, but are interbedded with limestones and other dolomites through a

thickness of over 2,75 feet in the section most carefUlly

studied by the writer. Wichman 44 puts 600 feet of the

dolomite series into the Bluebird as he defines it,

whereas his coworker Olmstead 45 limits the Bluebird

to 140 feet. The writer hesitates to make the correlation at all on the basis of lithology only, especially as

dolomite of the Bluebird type interfingers with mottled limestone at the base in this area, so that closely

adjacent sections show variations of 100 feet or more

in the stratigraphic position of the lowest representative of the type. Similar and even more striking variations OCCurin the Bluebird type of dolomite in the

Deep Creek Range, 100 miles to the west, where they

have been studied by Nolan.46 In view of these variations, the writer does not designate any formation as

Bluebird dolomite in the Ophir district but includes

the dolomite of Bluebird lithology with the overlying

dolomites in one formation, the Lynch dolomite. It

seems probable that the Lynch dolomite as here defined includes beds equivalent, at least in part, to the

Bluebird, Cole Canyon, and perhaps Opex dolomites

of Tintic, but as already shown, no boundary between

the two lower units can be established in this area, and

no clear and constant distinctions were recognized by

the writer in the upper beds which might serve as a

basis for dividing the formation into two upper units

equivalent to the Cole Canyon and Opex dolomites.

The Lynch dolomite, except for the beds of Bluebird

type, resembles the Cole Canyon of Tintic throughout,

and no beds resembling the Opex were noted here.

This does not support the correlation offered by Olmstead of 530 feet of the dolomite with the Cole Canyon

and 218 feet with the Opex.

•• Wichman, F. M., op. cit., p. 560.

•• Olmstead, S. G., op. cU., p. 441,

•• Nolan, T. B., Geology and ore dl'posits of the Gold Hill quadrangle,

Utah: U. S. Geol. Survey report (in preparation).
Deep Creek Range, Utah

Gold Hill district

(1".B.Nolan, 1930l

~

Quartzite

~

Limestone

~Dolomite

f

ph,rformation

320'

Middle Cambrian ---~w;~Cam~~n----

Tintic quartz ite

300'

/::.x·:

~:.:\(..

¥d

I.;:':\';'·~' Prosguea~iz~~untain •.•.•·~.:i).: 4,750'

)).g)

Xi/;

Concealed

FIGURE 2.-Variations of Cambrian formations of western Utah in a

west-east direction In the latitude of Ophir

Vertical scale

500 c 500 Feet

--~----~,

Correlations of the Cambrian of the Oquirrh Range

with Cambrian rocks of other districts in Utah are

shown diagrammatically in Figures 2 and 3. These

diagrams bring out a number of regional relationships

(}f some significance. Figure 2 shows the remarkable

thickening of the Cambrian section westward from the

Cottonwood district of the Wasatch Range. To dislegard the Lower Cambrian, of which, except in the

Cottonwood district, the base is everywhere concealed,

the Middle Cambrian shows in round numbers 800

feet in the Cottonwood district, 1,200 feet in the

Oquirrh Mountains, and 4,300 feet in the Deep Creek

Range. These figures, in connection with the fairly

uniform lithology of all three sections, suggests very

strongly that the area of maximum deposition-the

Middle Cambrian geosyncline-had its axis of depression far to the west, in the neighborhood of the Deep

Creek Range, as has been pointed out by Nolan.47

That the axis extended in a north-northeasterly direction near Pioche, Nev., the Deep Creek and House

Ranges, and Blacksmith Fork, in the northern

Wasatch Range of Utah, is very probable, in view of

the remarkable similarities in thickness of all these

sections, as seen in Figure 3.

The Upper Cambrian variations can not be so confidently referred to original depositional differences,

as the Cottonwood, Oquirrh, Tintic, and Deep Creek

sections are all limited at the top by unconformities.

Figure 3 also brings out a point made by Walcott 48

that the Cambrian sea advanced from the south, so

that the deposition of coarser clastic materials persisted in the northerly areas to a

much later date than in the southerly areas, which, correspondingly,

earlier became the seats of offshore

sedimentation.

Wasatch Range,Utah

Cottonwood district

(F.C Calkins, 1920)

An unconformity limits the Lynch

dolomite at the top, separating it

from the overlying Jefferson (?)

dolomite, as described later. This

unconformity represents a time interval including the Ordovician, Silurian, and part of the Devonian, so

Cambrian Quartzite 800' that in the Oquirrh Mountains, Middle (?) Devonian beds rest directly

upon the Upper Cambrian. The sections of Figures 2 and 3 show either

that the Oquirrh locality, near the

border of the Middle Cambrian and Upper Cambrian

., Nolan, T. B., Late PaleOZOicpositive area in Nevada: Am. Jour.

Scl., 5th ser., vol. 16, pp. 153-161, 1928.

••Walcott, C. D., Cambrian sections of the Cordll1eran area: Smithsonian Misc. ColI., vol. 53, No.5, p. 191, 1908; Problems of American

geology, p. 170, New Haven, 1915.
geosyncline, was never the seat of important sedimentation during this interval or that the deposits of these

periods have been here eroded. In the other districts

Abundant evidence has been marshaled by Loughlin 49 to show notable erosion in central Utah during

post-Cambrian and pre-Mississippian time. The

House Range, Utah

(WalcoH,1908)

Pioche, Nevada

(West~ate -\

Knopt, 1927J

Ordovician

Ifh:r\?~rSandstone

1~<W~:;'\1Quartzite

[.~·};·::.?nilSandy limesione

~Limestone

Wasatch R"nge, Utah

Blacksmith Fork section

(Walcott, 1908)

OI"doV1Cian

i77t!;~I Limestone containine nod- :,,~:- utes of chert orflint'

~DOlomite

• Shale

rT,"~rlClayey qr ar~illa- .:: -= ~ C€OU5 lImestone

Bloomington

formation 1.320'

Ope x dolomite

UPPerCole Canyon dolomite

510' !I1,d.~",~

.Cqf/j~an

Bluebird dolomite 175'?

Herkimer limestone 235'

Dagmar limestone lOa'

Chisholm shale 150' Howell formation 435'

Lyndon limestone 400' Spence shale 20' ,

Langston(?) fm. 205-

Middle Cambrian ~ _Midd~C~b.!:i.a~? Lower Combrian -.... Lower Combrian .

0.:.:::::.". ~Pioche shale 125'

D::~·:'U

i:if~1·:i~:Pioo:::~:~ol~~;5jn

:N?~~::

Spence shale 30'

Langston formalion 498'

Ophir formation 355'

Middle Cambrian

LOwerCalTibrian righam formation 1,230'+

11~ii·l I,~.,.., ::,;,.f..:::-.. quart zite'""0'"'0 1,500'

;J~&.

Concealed

FIGURE 3.-Varlatlons of Cambrian

the Upper Cambrian is succeeded by Ordovician rocks,

but in the Oquirrh Mountains the lowest postCambrian rocks represented are Devonian, and in the

central part of the Wasatch Range Mississippian.

major part of this erosion is assigned by him to late

Devonian pre-Mississippian time, an assignment which

•••Loughlin, G. F., Geology and ore deposits of the Tlntlc mlnln~

district, Utah ~U. S. Geol. Survey Prof. Paper 107, pp. 36-38, 1919.
seems eminently suitable. However, there is definite

local evidence that some of this erosion occurred earlier

than Middle Devonian time. Much of the evidence

vf erosion adduced by Loughlin can be interpreted, as

he recognized, to indicate pre-Devonian as reasonably

as post-Devonian emergence, and the absence oil:Silurian rocks at Tintic and of both Silurian and

Ordovician rocks at Cottonwood and Ophir Canyons,

with the presence of Devonian at Tintic and Ophir,

points clearly toward this region as being of positive

t~ndencies in pre-Devonian time.

The absence of late Silurian and of Lower Devonian

at Gold Hill, Utah,50 indicates that the entire region

may have been emergent just prior to the Middle

Devonian. In the absence of more detailed information from other districts in central and western Utah,

further discussion is hardly profitable; suffice it to

point out that future work may well demonstrate that

the fourth (pre-Middle Devonian) period of erosion

in pre-Mississippian time recognized by Loughlin 51

at Tintic was of much more than local significance.

The erosion may indeed have been fully as widespread

as the post-Devonian erosion, but this remains to be

demonstrated.

DEVONIAN SYSTEM

MIDDLE (1) DEVONIAN SERIES

Distribution wul topographic expression.- The

Lynch dolomite is unconformably overlain by the Jefferson (?) dolomite. This formation crops out just

above the Lynch dolomite, forming steep cliffs with

slight benches beneath them. Such cliffs and benches

occur on both sides of Ophir Canyon and in Dry

Canyon, without any breaks except such as are due to

the faults which have been mentioned as offsetting the

Lynch dolomite outcrops.

Stratigraphy.-The lowest bed of the Jefferson (n

dolomite is a fine-grained soft shaly and dolomitic

sandstone whose softness and general textural similarity to the beds between which it lies unite in making

it inconspicuous. It is highly probable that the dolomites here referred to, the Jefferson (~), would not

have been differentiated from the Lynch except that

the identification of post-Cambrian fossils within

them by Edwin Kirk led him to search for evidence

of a stratigraphic break below. Close search was rewarded by the identification of this thin clast.ic bed,

whose lower surface is seen to be somewhat irregular.

Shaly fragments and quartz grains occur' in it, but it

is composed chiefly of dolomite sand. Once discovered by Mr. Kirk, he and the writer were able to recognize the horizon at each place at which search for it

was made, but the boundary as shown on the map was

IONolan, T. B., op. cit. (in preparation).

51 Loughlin, G. F., op. cit., p. 34.

not actually traced in detail, because the interval between it and the easily followed contact at the top of

the formation is so slight and the variations observed

in this interval are so nearly negligible. Accordingly

the establishment of a dozen or so control points for

the basal contact sufficed to permit its deHneation by

reference to the upper contact, at least within the

limit of error permissible on the scale of the accompanying map.

The most characteristic lithologic feature of the

formation is exhibited by a very massive bed a short

distance below the top. This bed consists of crystalline very dark gray dolomite, with almost no discernible tendency toward bedding, which carries numerous white blebs of calcite. These white calcite

masses are very conspicuous, standing out in distinct

contrast to their dark matrix. They range from about

a quarter of an inch to 2 inches, or even, exceptionally,

3 inches in diameter. Their shapes are reminiscent of

some large pentameroid brachiopod, but diligent

search failed to bring to light any identifiable forms,

and it is even doubtful that they are organic, although

no other explanation of their presence is apparent.

The bed is useful for stratigraphic tracing and is

locally called the" eye bed" because these" eyes" are

so conspicuous. A specimen of the rock composing the

bed is illustrated in Plate 6, A.

The Jefferson (~) dolomite is limited upward by an

unconformity upon which rest the basal beds of the

Madison limestone, of lower Mississippian age. The

following section is a continuation of the measured

section of the Lynch dolomite:

Section Of Jefferson (l') dolomite on spur east of Cliff mine

Madison limestone: Thin-bedded bluish-gray crystalline, highly fossiliferous limestone.

Unconformity, marked by chert pebbles and a typical

small-scale karst topography (illustrated in fig. 4).

Jefferson (?) dolomite: Feet

1. Gray massive coarsely crystalline dolomite, in

one bed_____________________________________ 40

2. Dark-gray coarsely crystalline massive dolomite,

weathering almost black, with large oval calcite blebs conspicuously distributed throughout.

Passes upward by the gradual elimination of

the blotches into bed 1. Locally called the

" eye bed" in reference to the calcite blotches_ 75

3. Medium-gray finely crystalline dolomite, weathering dark gray, in beds ranging from 2 to 8

inches in thickness 45

4. Massive white siliceous limestone, poorly bedded

and not well exposed________________________ 17

5. Poorly exposed soft sandstone, alternating in

layers about 2 or 3 inches thick with limestone.

The sandstone is gray, weathering with slight

reddish to brownish tinges, poorly bedded,

somewhat shaly, fine grained, probably in large

part composed of reworked dolomitic sand_____ 8

Unconformity, a slightly wavy surface. 185

Lynch dolomite: Thin-bedded light-gray dolomite at top.
Age and correlation.-The Jefferson (~) dolomite

has yielded, from the massive" eye bed," a number of

poorly preserved fossils upon which Mr. Kirk reports

as follows:

Lot Gy-26-15. Dolomitic limestones overlying the Cambrian

.and underlying the highly fossiliferous Mississippian. Collected in the main near the ball park, east side of Ophir, Utah:

Cyathophyllum sp.

Syr'ingopora, 2 species.

Spirifer sp. .

The preservation of the material is so poor that accurate

determination of the fossils is out of the question. However,

the fossils of this lot suggest Devonian rather than Mississippian. The lithology of the beds is that of the Middle Devonian

(Jefferson limestone and its equivalents), at variance with the

Mississippian as known. Moreover, the field relations of this

horizon with the overlying typical Mississippian indicate a

time break of considerable magnitude. Taking all these factors

into consideration it seems reasonably safe to assign the beds

to the Middle Devonian.

Rocks of Upper Devonian age (the Pinyon Peak

limestone) have been reported from the Tintic district,52 but they are limestones instead of dolomites as

at Ophir, and though of comparable thickness (about

150 feet) they have been tentatively assigned to the

Upper Devonian (Three Forks) instead of Middle

Devonian (Jefferson). It is possible that Devonian

dolomites of Jefferson age are present in the upper 400

feet of the underlying Bluebell dolomite at Pinyon

Peak, in the Tintic district, but no fossils were found

in them, and the possibility that they may be of Jefferson age is the most that can be suggested.

South and west of Tintic the next place from which

Devonian rocks have been described is the San Francisco district, Utah. 53 Here the only fossils collected

were determined as presumably correlating the

Mowitza shale with the upper part of the Jefferson.

No unconformities were found in the section, and, as

Butler states, it is not known how much of the underlying Red Warrior limestone is also Devonian. Possibly several hundred feet of the overlying Topache

limestone is. also Devonian, although Butler believed

that its lithology suggested that it is all of Mississippian age, as the upper part is known to be.

In the Deep Creek Range, about 90 miles west of

the Oquirrh Mountains, from 2,350 to 2,850 feet of

dolomite, with subordinate limestone and sandstone,

haS been assigned to the Middle Devonian.54 Possibly

the Jefferson dolomite is to be correlated with some

part of this section, but in the present state of our

knowledge such correlation must be considered only

possible, not probable. No other sections in Utah west

of the Oquirrh Mountains have been studied suffi-

•• Loughlin, G. F., op. clt. (Prof. Paper 107), pp. 36-38.

53 Butler, B. s., Geology and ore deposits of the San Francisco and

adjacent districts, Utah: U. S. Geol. Survey Prof. Paper 80, pp. 29-35,

1913.

54 Nolan, T. B., Geology and ore deposits of the Gold Hill quadrangle,

Utah: U. S. Geol. Survey report (in preparation).

ciently to determine the presence or absence of beds

equivalent to the Jefferson.

The Jefferson dolomite is probably represented in

the Wasatch Range north of Ogden,55 but the fossils

from Big Cottonwood Canyon referred to the Devonian by Hintze 56 are actually of Mississippian

age.57

Schneider 58 refers casually to Devonian rocks at

Neffs Canyon, near Salt Lake City, but he gives no

faunal list, apparently basing his age determinations

on correlations with the Cottonwood district. Hence,

this determination can be regarded as questionable.

No other Devonian rocks have yet been recognized in

the Wasatch Range south of Salt Lake City.59

In the Randolph quadrangle, in northern Utah, the

Jefferson dolomite is prominently developed,60 resting

with apparent conformity upon the Laketown dolomite, of Silurian age. In the Randolph quadrangle

the formation is overlain with probable conformity

by the Threeforks limestone, of Upper Devonian age,

and the Threeforks is in turn apparently conformable

beneath the Madison limestone. The Jefferson consists

of dense dark-gray, dominantly massive dolomite,

with some thin beds toward the base.

The dolomites lying unconformably above the Cambrian at Ophir are dense, dark gray, and massiveaccording to Kirk, lithologically very like the J efferson of the Randolph quadrangle. They lie unconformably beneath the fossiliferous limestone with a

characteristic Madison fauna, which is, throughout

the Rocky Mountain region, as far as known, the

earliest representative of the Mississippian. The

meager and unsatisfactory faunule collected from

these dolomites appears to indicate a Middle Devonian

age, and, on account of the lithologic similarity, it is

suggested that the rocks at Ophir are equivalent to

part of the Jefferson dolomite. The element of uncertainty in the extension of such a correlation over

the interval (about 80 miles) between the Randolph

quadrangle and Ophir, without adequate study at intermediate points, it seems best to express by placing

a query after the name. The southward and westward continuation of even this tentative correlation

seems at present impossible. It is distinctly possible

that this area marks the approximate limit of the J ef50 Blackwelder, Eliot, New light on the geology of the Wasatch

Mountains, Utah: Geol. Soc. America Bull., vol. 21, pp. 527-528, 1910.

.., Hintze, F. F., A contribution to the geology of the Wasatch Mountains, Utah: New York Acad. ScL Annals, vol. 23, pp. 108-109, 1913.

51 Kirk, EdWin, oral commnnication.

..,Schneider, Hyrum, A discussion of certain geologic features of the

Wasatch Mountains: Jour. Geology, vol. 33, pp. 36-37, 1925.

•• Loughlin, G. F., Reconnaissance in the southern Wasatch Mountains: Jour. Geology, vol. 21, pp. 436-452, 1913.

eoKindle, E. M., The fauna and stratigraphy of the Jefferson limestone in the northern Rocky Mountain region: Bull. Am. Paleontology.

vol. 4, No. 20, pp. 14-18, 1908. Richardson, G. R, The Paleozoic section in northern Utah: Am. Jour. Sc!., 4th ser., vol. 36, pp. 406,

411, 1913.
ferson in this direction, but it would be premature to

express so definite a limit.

PRE-MISSISSIPPIAN UNCONFORMITY

The presence of a pre-Mississippian unconformity

in Utah has been emphasized by Loughlin.61 In the

Stockton and Fairfield quadrangles the base of the

Mississippian rocks is exposed for only about 4 miles

and over this distance gives little evidence of either

angular unconformity or significantly variable depth

of erosion in the pre-Mississippian rocks. Nevertheless, there is ample local evidence of erosion and sea

transgression in the Oquirrh Mountains, and the regional evidence of a significant break at this horizon

is entirely convincing.

The pre-Mississippian erosion is very clearly indicated by the contact of the Madison limestone with the

Jefferson (~) dolomite. This contact appears to repreFIGURE 4.-Detail of contact between Jefferson (?) dolomite

and Madison limestone, shOWingtYPical small-scale karst

topograpby of the contact surface

sent a preserved karst topography, the top of the

coarsely crystalline gray Jefferson (?) dolomite having a relief of fully 2 feet in many places and being

marked by scattered solution cavities as much as 6

feet deep, now filled with the dense blue-gray limestone of the Madison. Figure 4 represents common

features of the contact. At some places there are

pebbles of dolomite and black chert in the base of the

Madison, and the maximum observed thickness of this

pebble bed is about 1 foot.

In the Uinta Range the Mississippian overlaps the

Ordovician and rests directly on the Cambrian.62

Whether the erosion thus indicated was chiefly preDevonian or post-Devonian, however, is not surely

known. No unconformity has been definitely recognized between the Devonian and Mississippian in

southeastern Idaho 63 and northeastern Utah,64 but a

•, Loughlin, G. F., op. cit. (Prof. Paper 107), pp. 36-38.

.2 Weel's, F. B., Stratigraphy and structure of the Uinta Range:

Geol. Soc. America Bull., vol. 18, p. 438, 1907.

"Mansfield, G. R., Geography, geology, and mineral resources of a

part of southeastern Idaho: U. S. Geol. Survey Prof. Paper 152,

p. 182, 1927.

64 Richardson, G. B., Am. Jour. Scl., 4th ser., vol. 36, p. 412, 1913.

doubtful one near Ogden has been referred to by

Blackwelder 65 with the suggestion that it is probably

unimportant. This unconformity may be within

rather than beneath the Mississippian, according to

Blackwelder.

Just north of Salt Lake City the Mississippian rests

upon the Upper Devonian,66but a short distance to the

south, at Big Cottonwood Canyon, it rests directly

upon beds at widely varying horizons in the Camllrian,67 indicating significant post-Cambrian erosion,

which, however, may have been in part pre-Devonian

rather than all post-Devonian. Between Big Cottonwood Canyon and Mount Nebo, Loughlin 6Sdiscovered

the Mississippian limestones resting on varying thicknesses of pre-Mississippian limestones, perhaps locally

Gill the Ophir formation itself. At Tintic the Mississippian begins with a clastic member, the Victoria

quartzite, and rests in some places on Upper Devonian

and elsewhere on Ordovician beds.69 This is clearly

due to an erosional unconformity, as is confirmed by

the relations in the Oquirrh Mountains, described

&bove,and in the southern part of the Wasatch Range.

Still farther south, in the San Francisco district,

Butler 70was able to detect no unconformity between

the Mississippian Topache limestone and the Devonian

l\1owitza shale, but the fossils from the Topache

suggest Ii, post-Madison age, which may indicate

an unconformity, with the omission of the lower

Mississippian.

In the Gold Hill quadrangle Nolan 71 has found

evidence of pre-Mississippian unconformity, with the

upper Mississippian overlapping a wedge of Madison

limestone and resting directly on Middle Devonian.

From Gold Hill westward there is strong evidence of

orogeny in late Devonian or Carboniferous time in

western Nevada.72

The pre-Mississippian unconformity is accordingly

seen to be, as suggested by Loughlin, of widespread

occurrence and significance.

Distribution arnd topographic ewpression.-The

Madison limestone crops out on the north wall of

Ophir Canyon above the belt of Jefferson (~) dolomite at the Cliff mine and, forming a rather less pre65 Blackwelder, Eliot, Phosphate deposits east of Ogden, Utah :U. S.

Geol. Survey Bull. 430, p. 539, 1910.

66 Kirk, Edwin, and Mathews, A. A. L., oral communications.

• 7 Calkins, F. C., in Butler, B. S., and others, The ore deposits of

Utah: U. S. Geol. Survey Prof. Paper 111, pp. 237-238, 1920.

•• Loughlin, G. F., Reconnaissance in the southern Wasatch Mountains: Jour. Geology, vol. 21, pp. 444-447, 1913.

•• Loughlin, G. F., U. S. Geol. Survey Prof. Paper 107, pp. 37, 39,

Ifllll.

70 Butler, B. S., U. S. Geol. Survey Prof. Paper 80, pp. 35-36, 1913.

71 Nolan, T. B., op. cit.

72 Nolan, T. B., A late Paleozoic positive area in Nevada: Am. Jour.

Scl., 5th ser., vol. 16, pp. 153-161, 1928.
cipitous slope than that formation, swings over the

divide into Dry Canyon, where it forms much of the

lower part of the north wall as far as the mouth.

Here its outcrop crosses the canyon and forms a

wedge-shaped area on the west slope of the hill between Dry Canyon and the west end of the Canyon

fault. South of the Canyon fault the Madison limestone forms much of the prominent spur southea'st of

Dry Mountain west of Ophir, and its outcrop forms

a U-shaped area extending between the Canyon fault

on the north and the Lion Hill fault on the south,

with its base pointing downstream in conformity to

the westerly dip on this portion of the Ophir anticline.

Along much of the course of the Lion Hill fault the

Madison limestone is dropped from sight, though

there are some" slivers" of the formation caught in

as horses along the fault. Northeast of the small

knoll where the trail from Long Trail Gulch passes

into Ophir Canyon the Mad.ison forms a continuous

belt down into Ophir Canyon, which it reaches south

of the baseball park. North of the baseball park the

formation is offset about 1,000 feet by the several

branches of the Canyon fault, but northwest of them

its outcrop is uninterrupted by faults of consequence

except the Cliff fault, which cuts it in the Cliff mine

workings.

Stratigraphy.-The Madison limestone rests on the

Jefferson (~) dolomite without notable angular discordance but with very clear and unmistakable unconformity, as shown by the distinct karst topography

(fig. 4) already described. At some places there are

pebbles of dolomite and black chert in the base of the

Madison, and the maximum thickness of this pebble

bed is about 1 foot.

The Madison limestone is a bluish-gray dense limestone, easily distinguished from all the underlying

limestones by its freedom from mottling of any sort.

H is of considerable economic importance, as the basal

part is ore bearing in the Buckhorn mine.

The following section, which is a continuation of

the section of the Jefferson (~) dolomite, is considered

typical of the formation as developed in the Ophir

district:

Section of Madison limestone on ridge east of Buckhorn mine

[Strike N. 60· W.; dip 28· N.]

Deseret limestone: Dense blue-gray limestone, with a soft

carbonaceous and phosphatic shale at base.

Conformable contact.

Madison limestone: Feet \

1. Very cherty blue-gray limestone. The black chert

is arranged in lenses, which average 6 inches

apart stratigraphically and are as much as 6

feet long and 3 inches thick__________________ 55

2. Gray blocky limestone, in beds averaging about

2 inches thick. '1'he member is much viened

with calcite and is more coarsely granular

than bed 1. Little or no chert is presenL_____ 29

Fault of unknown but probably slight displacement.

Madison limestone-Continued. Feet

3. Cherty blue-gray limestone, rather massive below, somewhat thinner bedded above. Black

chert lenses occur within the individual limestone beds as well as between them. The chert

lenses are spaced perhaps 2 feet apart stratigraphically and range from knife-edges to 21;2

inches in thickness and several feet in length.

The limestone beds are considerably broken and

recemented with white calcite. The member

forms a ledge 1001;2

4. Very light bluish-gray dense limestone, very fossiliferous, pure except for subordinate brown

shaly streaks, thin bedded at the base, where

the beds range from 1 to 5 inches in thickness,

but becoming thicker bedded and somewhat

more coarsely crystalline upward. Some of the

beds near the top are as much as 8 feet thick __ 2681h

Irregular surface of unconformity. 462

Jeft'erson (:) dolomite: Light-gray dolomite at top.

Age anrlJcorrelation.-Fossils from the Madison

limestone have been reported on by G. H. Girty as

follows:

The lowest of the Carboniferous formations recognized is

the l\ladison limestone, from which we have seven COllections,

1 made in 1925 by Paige, 6 made in 1926 by Gilluly and Kirk,

and 1 in 1927 by Girty. These lots have essentially the fauna

of the Madison limestone and are of early Mississippian age.

5799. Limestone below the heavy chert member of the Madison limestone, Ophir Creek, north side, near road, Ophir,

Utah; collected by Sidney Paige:

Triplophyllum sp. Pustula sp.

Cystodictya sp. Camarotoechia sp.

Rhipidomella sp. Dielasma sp.

Schizophoria aft'. S. sedalien- Spirifer centronatus.

sis. Syringothyris aft'. S. newarkLeptaena analoga. ensis?

Schuchertella aft'. S. chemung- Reticularia cooperensis.

ensis. Cliothyridina aft'. C. glenparkChonetes loganensis. ensis.

Prod uctus aft'. P. sedaliensis. Hustedia circularis?

Productus ovatus. Euomphalus utahensis.

Product us aft'. P. sampsoni. Euomphalus utahensis val'.

'Productus parviformis. Straparollus sp.

Pustula patula? Platyceras sp.

6015. Within 50 feet of the base, Madison limestone on

Lynch Ridge, east of Clift' mine, Ophir Canyon, Utah; collected

by James Gilluly:

Tripiophyllum excavatum.

Syringopora surcularia.

Fenestella sp.

Spirifer centronatus.

Spiriferina solidirostris.

Straparollus ophirensis.

Euomphalus luxus.

Loxonema sp.

6015A. Same locality as 6015; collected by James Gilluly

and M. J. Buerger:

Schuchertella chemungensis. I Spirifer centronatus.

Chonetes loganensis. Spiriferina solidirostris.

Productus sp. Euomphalus luxus.

6016. Middle of Madison limestone 500 feet southwest of

mineral monument No.4, Ophir Canyon and Dry Canyon

divide, Stockton quadrangle; collected by James Gilluly:

Triplophyllum excavatum. Spirifer centronatus.

Schuchertella chemungensis. Composita humilis.

Chonetes loganensis. Eumetria verneuiliana.

Pustula sp.
6017. Base of Madison limestone, 200 yards northwest of

ball park, Ophir Canyon, Stockton quadrangle; collected by

Edwin Kirk:

Syringopora surcularia. Composita humilis.

Aulopora sp. Cliothyridina crassicardinalis.

Triplophyllum excavatum. Eumetria verneuiliana.

Cyathophyllum sp. Parallelodon sp.

Cyathophyllum? sp. Aviculipecten sp.

Lithostrotion n. sp. Conocardium sp.

Echinocrinus sp. Laevidentalium aff. L. venusSchuchertella chemungensis. tum.

Chonetes loganensis. Bucanopsis aff. B. deflecta.

Productus ovatus. Platyceras sp.

Productus g.allatinensis. Naticopsis sp.

Productus aff. P. arcuatus. Euomphalus luxus.

Productus sp. Straparollus utahensis.

Pustula n. sp. Sphaerodoma? sp.

Camarotoechia metallica. Cyclonema sp.

Girtyella? sp. Loxonema n. sp.

Spirifer centronatus. Griffithides sp.

Spiriferina solidirostris. Paraparchites sp.

6021. Collected from limestone just below the shale in which

is located the Fisk mine, north side of Ophir Canyon, 1 mile

above Ophir, Fairfield quadrangle; collected by Edwin Kirk,

M. J. Buerger, and James Gilluly:

Triplophyllum sp. Spirifer centronatus.

Crinoid fragments. Spirifer mysticensis.

Schizophoria aff. S. compacta. Brachythyris aff. B. gurleyi.

Schuchertella chemungensis. C<lmposita monticola?

Chonetes illinoisensis. Aviculipecten sp.

Productus gallatinensis.

6255. About 200 feet above the base of Madison limestone,

north side of Ophir Creek, west of Ophir, above old tailing

dump; collected by G. H. Girty:

Zaphrentis sp. I Spirifer centronatus.

Lithostrotionella n. sp.

The type locality of the Madison limestone is in

the Madison Range, in western Montana, but its characteristic lithology and fauna have justified the extension of the name through southeastern Idaho 73to

northern Idaho.a

In the Cottonwood district of the Wasatch Range

limestone carrying the typical Madison fauna and of

comparable lithology with the type Madison have been

referred to that formation by Calkins.76 In view of

the fossil evidence as reviewed above by Girty, it

seems thoroughly justifiable to refer the rocks in the

Oquirrh Mountains to the Madison limestone as well.

The Madison is also recognized in the Deep Creek

Range, Utah,76 where it is overlapped by rocks of

upper Mississippian age. .

In the Tintic district 7'7the Gardner dolomite carries fossils of Madison age, which, with the uncon73 Mansfield, G. R., Geography, geology, and mineral resources of part

of southeastern Idaho: U. S. Geol. Survey Prof. Paper 152, pp. 60-

61, 1927.

••Richardson, G. B., The Paleozoic section in northern Utah: Am.

Jour. Sc!., 4th ser., vol. 36, p. 412, 1920.

7. Calkins, F. C., Geology and ore deposits of the Cottonwood district, Utah: U. S. Geol. Survey report (in preparation).

7. Nolan, T. B., Geology and ore deposits of the G()ldHill quadrangle,

Utah: U. S. Geol. Survey rePQrt (in preparation).

•• Loughlin, G. F., op. clt. (Prof. Paper 107), p. 40.

formity beneath the Victoria quartzite, support a correlation of the Gardner dolomite and Victoria quartzite with these rocks, although the lithology of the sections is quite different. It seems highly probable that

the Victoria quartzite, Gardner dolomite, and Pine

Canyon limestone of 'rintic are equivalent, at least in

part, to the Madison and Deseret limestones of the

Ophir district, as here defined. The fact that both

the Madison limestone of the Ophir district and the

Gardner dolomite of Tintic are succeeded by black

shale suggests that the Pine Canyon limestone of

Tintic may be wholly later than the Madison. Only

Brazer fossils have been found in the Pine Canyon

limestone, and as the cherty character of some of its

lower beds can be duplicated in the post-Madison limestones of the Oquirrh Mountains this character can

hardly of itself prove the Madison lligeof these lower

beds, as was tentatively suggested by Loughlin from

comparison of the Tintic section with the Mississippian of the southern part of the Wasatch Range.

However, the continuity of so thin a shale as the one

succeeding the Madison in the Oquirrh Mountains is

so doubtful that the occurrence of a shale in both sections at compllirable horizons can hardly be held tOo

disprove Loughlin's tentative assignment of a Madison age to the lower part of his Pine Canyon limestone. Nevertheless, the parallelism between the two·

sections is suggestive. ~

Loughlin suggested, because of their lithoJogic similarity, that the black shale bed at the base of the Pine

Canyon limestone and a thinner shale bed in the underlying Gardner dolomite might be equivalent to the two

shale beds at Mercur described by Spurr,78 but the

lower shale at Mercur belongs to the "Great Blue'"

limestone and is much higher stratigraphically.

The correlation suggested by Olmstead 79made the

lower part of the Madison limestoille as here limited

equivalent to part of the Ajax limestone (Ordovician)

of Tintic (which the fossil evidence immediately negatIves) and the rest of the Madison and the Deseret of

this report equivalent to the Pine Canyon of Tintic.

The part of this correlatiolll referring to the Deseret

seems well supported by the paieontologic evidence,.

though, as suggested above, there is doubt that any of

the Madison is to be correlated with the Pine Canyon.

Wichman so suggested a correlation very similar to the

one here offered except that he believed that the Buckhorn ore beds (the basal 30 feet of the Madison limestone as here defined) werE~not represented at Tintic.

'1'0 the writer this appears to be a minor point, as there

is doubt if any member so thin can be said (in the

absence of tracing or definite fossil evidence) to per73 Spurr, J. E., U. S. Geol. Surv"l' Sixteenth Ann. Rept., pt. 2, pp..

375-377, 1895.

79 Olmstead, S. G., op. clt., pp. 438, 441-442.

soWichman, F. M., op. dt., p. 563.
sist for such a distance as separates Ophir and Tintic,

f'.ndhe is in practical agreement with Wichman on the

classification of this part of the section.

The lowest Carboniferous of the San Francisco district is probably somewhat younger than Madison,81

so that the time represented by the Madison limestone

was probably one oct:nondeposition or even of erosion

in that area. Carboniferous rocks occur in many of

the other ranges of western Utah, and it is probable

that the Madison is represented in several if not in all

of them, but sufficient detailed work to prove its

presence has not yet been done.

Di8tribution and topographic expre'88ion.-The

limestone here named Deseret limestone because of its

exposures at the Deseret mine, in Dry Canyon, directly

overlies the Madison limestone, and its distribution

closely follows that of the Madison in both Ophir

and Dry Canyons. However, it is also exposed south

of Ophir Creek, in Mercur Canyon, which does not

cut deeply enough to lay bare the Madison limestone.

Its outcrop in Mercur Canyon is about a mile long and

occurs close to the anticlinal axis. It plunges beneath

the Humbug formation both up and down stream.

Silverado Canyon has not cut deeply enough to expose

the formation.

The Deseret, save for a thin, noticeably soft benchforming shale at Its base (a zone which is not exposed

in Mercur Canyon), forms a fairly even steep surface,

not so precipitous as that of the thick chert member of

the Madison limestone, but somewhat steeper than the

slopes of the thin-bedded limestones in the lower part

of that formation.

St'/'(J)tigraphy.-Except for the basal beds the Deseret limestone would be separable only with difficulty

on lithologic criteria from the underlying Madison

limestone. Like the Madison, it consists almost

wholly of blue-gray fine-grained limestone with

greater or less amounts of chert. The basal bed of the

formation is a black shale, of some economic importance as marking the top of the zone of mineralization

in the Hidden Treasure mine. It is immediately overlain by a thin bed of highly phosphatic oolite, the

grains of which average perhaps 1 millimeter in

diameter. Considerable numbers of broken and phosphatized fossil fragments also occur in this bed.

There are a few sandy limestone and shaly layers

above the basal shale, but these are rather thin with

the exception of an 8-foot bed of quartzite which

locally, near the Jim Fisk mine, occurs about 320 feet

above the base. The following section is believed to

81 Girty, G. B., quoted by Butler, B. S., Geology and ore deposits of

the San Francisco and adjacent districts, Utah: U. S. Geol. Survey

Prof. Paper SO, p. 36, 1913.

represent the character of the formation in this

district:

Section of Deseret limestone on north, sieZeOf Ophir OreelQ

[West from a point about 200 feet north of the St. John & Ophir

Railroad, west of the Cliff mine loading bins. Strike N. 40° W.;

dip 3So SW.]

Humbug formation: Brown fine-grained 2-foot quartzite

at the base.

Conformable contact.

Deseret limestone: Feet

1. Dark-blue fine-grained limestone, with much black

chert and some red-weathering shale. The

chert nodules and lenses range from half an

inch to 3 inches in thickness and occur at stratigraphic intervals of 2 to 3 inches near the

base. The limestone contains large nodules of

white calcite a quarter of an inch to 4 inches

in diameter, disttibuted irregularly. Toward

the top the member becomes more sandy, and

sand beds 3 or 4 inches thick appear 131

2. Massive light-blue coarsely crystalline limestone,

weathering light gray. Blocky, poorly bedded,

very fossiliferous, carrying many crinoid stems,

as well as other fossils_______________________ 13

3. Thin-bedded limy, poorly laminated shale, carrying large amounts of cherL__________________ 3

4. Limestone like bed 2_---------_________________ 20

5. Massive-bedded blue limestone, not noticeably fos:

siliferous; weathers brown in patches owing to

small amounts of irregularly distributed sand.

Becomes more sandy and cherty upward 168%

6. Poorly exposed thin-bedded, somewhat sandy

limestone 138

7. Massive, blocky sandy limestone; beds range from

8 inches to 3 feet in thickness and weather

brown but are dark blue-gray on fresh fracture_ 30

8. Poorly exposed cherty blue limestone 137%

9. Poorly exposed black, red-weathering shale with

a phosphatic oolite bed at the top ~_ 9

Conformable contact. 650

Madison limestone, very cherty toward the top.

The upper boundary of the Deseret limestone is

arbitrarily placed at the base of the first sandstone or

quartzite bed of notable thickness. It is not a fixed

stratigraphic horizon, for the quartzites and sandstones

of the overlying Humbug formation are exceedingly

lenticular and variable, so that the basal clastic bed

at one locality is likely to be several tens of feet above

the base only a few hundred yards away. Conversely,

a sandstone or quartzite which is the lowest in one

locality may be traced to its vanishing point, where

the limestones of the Deseret are uninterrupted, possibly for as much as 50 feet higher stratigraphically.

At best, the boundary is arbitrary, but it is believed

that the distinction oct:the two units is decidedly important in connection both with historical geology and

with structure determinations. The complex faulting

of the Dry Canyon area is brought out most clearly by

the displacement of this boundary.
Age and correlation.-Fossils collected from the

Deseret limestone during the course of this survey were

~ubmitted to G. H. Girty, who reports as follows:

From the Deseret limestone we have only one collection,

6256. It shows a marked faunal change from the preceding

collections having a Madison fauna, but is itself more or less

novel in facies. This fauna in some respects appears allied to

the Moorefield fauna of Arkansas and Oklahoma, in others

to the fauna of the White Pine shale of Nevada, which are

mutually allied. In the Idaho section the fauna would find

place in the lower part of the Brazer, and in the typical section of the Mississippi Valley somewhere in the middle

Mississippian.

6256. About middle of Deseret limestone, north side of Ophir

Creek, west of and above old tailing pond west of Ophir

(Brazer) ; collected by G. H. Girty, Gordon New, and James

Gilluly:

Triplophyllum sp.

Fenestella sp.

Lingula n. sp.

Schizophoria sp.

Productus ovatus.

Product us aft. P. altonensis.

Productus aft. P. sampsoni.

Pustula vittata.

Pustula hirsutiformis.

Pustula aft. P. moorefieidella

var. pusilla.

Pustula, 3 sp. indet.

Camarotoechia sp.

Camarophoria thera?

Spirifer aft. S. moorefieldanus.

Spirifer aft. S. washingtonensis.

Spirifer sp.

Reticularia sp.

Brachythyris aft. B. suborbicularis.

Brachythyris sp.

Composita sp.

Cliothyridina aft. C. subl.amellosa.

Pterinopecten n. sp.

Platyceras sp.

The shale that is taken as the base of the formation

evidently marks a distinct change in the conditions of

sedimentation represented by the highly cherty limestones below. The phosphatic oolite associated with

the shale is also similar to material that has been elsewhere interpreted as marking disconformities in the

stratigraphic column. There are no distinct members

apparent between the phosphatic bed and the lowest

fossils, which are of Brazer (upper Mississippian)

affinities, and accordingly it seems very probable that

the boundary between the upper and lower Mississippian occurs either immediately below or immediately

above this shale, probably below.

As suggested in the discussion of the Madison limestone, it is possible that this shale should be correlated

with the one at the top of the Gardner dolomite at

Tintic, though this is by no means assured. If this

correlation is correct, the rocks here named the Deseret

limestone are the direct equivalents of those included

by Loughlin in the Pine Canyon limestone at Tintic

and that name could be transferred to Ophir without

coining a new term. However, as reviewed above,

Loughlin regarded the Pine Canyon (because of the

cherty beds in the lower part) as probably in part of

Madison age, whereas these rocks at Ophir are almost

surely entirely of Brazer age. Even if the shales of

the two sections are not equivalent, the Deseret must

represent a partial correlative of the Pine Canyon, for

the upper and only fossiliferous part of the Pine

Canyon is of upper Mississippian (Brazer) age and

both formations lie conformably beneath closely similar lenticular sequences of quartzite and limestone.

It is uncertain where Olmstead drew the boundaries

for his Pine Canyon formation,82 but apparently he

included in it much of the group here considered

Madison and foUowed no consistent usage in drawing

the top of the unit, for in one place he speaks of the

Hidden Treasure mine being in the upper member of

the formation, whereas in another place he states that

the upper member crops out in Mercur Canyon. The

shale here considered the base of this formation is

just above the Hidden Treasure ore bodies-hence in

the usage of the writer the workings of that mine are

not in the Deseret but in the Madison limestone. The

Deseret as here defined, however, includes the strata

in Mercur Canyon referred to the Pine Canyon by

Olmstead. The Madison rocks in which the Hidden

Treasure mine is situated do not crop out in Mercur

Canyon. Wichman pointed out the Mississippian age

of these rocks but did not suggest correlation with

other areas.

The Deseret is the lowest formation included in the

area studied by Spurr 83around Mercur. He referred

to it there as the" Lower Blue limestone" and cited a

report by Charles Schuchert giving its age as " Lower

Carboniferous."

The type locality of the Brazer limestone is in the

Randolph quadrangle, Utah.84 In· that district the

formation, which ranges in thickness from 800 to 1,400

feet, carries a phosphatic member in shaly beds near

the base. Considerable cherty and sandy material is

present higher in the formation, and in this respect it

resembles the upper Mississippian pf the Oquirrh

Mountains considered as a whole. However, a precise

correlation between the areas is at present impossible,

though it seems likely that the Deseret corresponds to

the lower part of the type Brazer. The Cottonwood

Canyon section of the Wasatch Range 85and that of

the San Francisco district 86resemble the Oquirrh section in general, but a discussion of regional correlations

can hardly be profitable in the present state of our

knowledge, because no faunal zones have yet been

recognized as significant in the upper Mississippian

rocks of the Rocky Mountain region.

Distribution and topographic empression.- The

Humbug formation is prominently exposed in Ophir

Canyon, above the Deseret limestone. The outcrop

west of the Cliff fault passes over the divide into Dry

Canyon and, after being displaced in a complex man82 Olmstead, S. G.• op. cit., pp. 442-443.

8. Spurr, J. E., op. cit., p. 371.

••Richardson, G. B.. op. cit., p. 413.

••Calkins, F. C., op. cit., pp. 238-239.

S6 Butler, B. S., op. cit., pp. 35-36.
ner by several faults on the north side of Dry Canyon,

passes above the Queen of the Hills mine and the Surprise (Garber) tunnel and thence down the west flank

of Bald Mountain to the mountain front. South of

Ophir Creek it is exposed on Lion Hill, in the westward-facing saddle between Lion Hill and Chloride

]>oint, and in Silverado Canyon, West Dip Canyon,

and Mercur Canyon. South of Mercur Canyon the

formation crops out in an irregular area as far south

as McFait Canyon, beyond which it is represented by

very small exposures in the bottom of Mitchell Canyon

and its northern tributary.

On the east flank of the range the Humbug is the

lowest formation exposed on the axis of the Long

Ridge anticline. It crops out over the southern tip of

Long Ridge from the alluvium boundary nearly to the

6,500-foot contour, a distance along the ridge of about

1% miles.

Over all its area of exposure the formation, owing to

the alternation of sandstones (or quartzites) and limestones of which it is composed, has a tendency to develop a ledge and slope topography only slightly

more irregular than that of the limestones between

which it lies but conspicuous because of the brownweathering sandstones and quartzites whose float

masks to a considerable extent the really considerable

portion of limestone in the formation.

Stmtigraphy.-The lower boundary of the Humbug

formation is arbitrarily placed at the base of the lowest

considerable quartzite or sandstone in the Mississippian

section. The sandstones (or quartzites) are lenticular,

so that the lowest sandstone in a given section when

followed along the outcrop is found to lens out, leaving a sandstone that in the given section was locally

some feet higher as the lowest sandstone in the new

section; or another lens may appear below, so that a

new base must be selected for the formation. Similar

relations exist at the top of the formation, and it is

fairly certain that exactly the same time unit is not

represented by this formation at different localities.

Nevertheless, the wide distribution of an interfingering

8eries of upper Mississippian sandstone and limestone

in Utah makes it seem probable that no very great

time differences are involved.

The following section represents the general character of the formation, though it is quite certain that

another section measured only a few feet away would

differ considerably.

"~6ction of Humbug formation on north wan of Ophir Canyon,

on south slope of Dry Mountain, 300 to 400 foot abooo Ophir

Creek

[Strike N. 40· W.; dip 45° SW.l

••Great Blue" limestone: Dark blue-gray limestone,

weathering light gray.

Conformable contact.

Humbug formation: Feet

1. Interbedded blue-gray fossiliferous limestones

and sandstones as much as 2 feet thick______ 1272

67463-32~

Humbug formation-Continued.

2. Light blue-gray fossiliferous limestones _

3. Brown even-grained sandstone _

4. Dark blue-gray limestone _

5. Brown sandstone _

6. Blue-gray coarsely crystalline fossiliferous limestone_______________________________________ 11

7. Poorly exposed brown limy sandstone__________ 13

8. Poorly exposed limestones and sandstones, alternating in beds as much as 1 foot thick.. _

9. Buff sandstone _

10. Gray limestone _

11. Platy, thin-bedded brown quartzite _

12. Gray limestone with white blotches of calcite,

fossHiferous________________________________ 25

13. Quartzite with some interbedded thin limestone- ~ 4---

14. Limestone in beds that average about 2 feet

thick _

15. Brown quartzite _

16. Gray crystalline fossiliferous limestone _

17. Brown quartzite _

18. Shaly gray limestone _

19. Brown quartzite _

20. Thick-bedded light-gray fossiliferous crystalline

limestone carrying white blotches of calcite___ 15

21. Brown quartzite______________________________ 6

22. Gray limestone in beds 2 to 4 feet thick, containing a few small lenses of quartzite _

23. Irregular quartzite lens; disappears within a

few feet to the south but increases to the north_

24. Blue-gray limestone _

25. Massive brown quartzite _

26. Gray limestone _

27. Gray, brown-weathering blocky quartzite _

28. White calcite breccia, containing fragments of

bluish-gray limestone and stringers of sand.

Very persistent and can be followed long distances _

29. Light-brownish quartzite _

30. Breccia zone like bed 28 ~_

31. Light-gray sandy limestone, carrying small

lenses of brownish-weathering quartzite _

32. Brown quartzite _

33. Blue-gray limestone _

34. Brown quartzit(> ~ _

35. Dense blue-gray limestone, in one bed _

36. Concealed; probably chielly limestone _

37. Coarsely crystalline fossiliferous blue-gray limestone --- _

38. Gray, bUff-weathering quartzite _

39. Coarsely crystalline blue-gray limestone _

40. Gray, brown-weathering quartzite, in beds from

1 inch to 2 feet thick ~________________ 37

41. Poorly exposed alternating thin limestones and

quartzites__________________________________ 30

42. Limy gray sandstone varying to sandy limestone_ 12

43. Blocky, poorly bedded brown sandy shale______ 1

44. Dense irregular lenticular blue limestone_______ 1

45. Brown limy sandstone_________________________ 7

46. Gray sandy limestone_________________________ 11

47. Fine-grained blocky, evenly bedded quartzite in

layers 1 to 18 inches thick; highly silicified

and weathers dark brown _

Feet

17th

472

3

672

34

1

872

1172

11

3

972

4

4

572

2

7th

572

2

24

572

12th

7%

11%

3

1472
6257. From lower 200 feet of the Humbug formation north

side of Ophir Canyon, west of Ophir; collected bY' G. H.

Girty and James Gilluly:

Syringopora sp.

Cyathophyllum sp.

Pentremites sp.

Crinoid indet.

Echinocrinus sp.

Productus brazerianus.

Humbug formation-Continued.

48. Sandy limestone varying to limy sandstone both

along and across the bedding; weathers brownish gray and breaks into blocks. The beds

range between 1 and 3 feet in average thickness and lens in and out____________________ 72

49. Brown fine-grained quartzite__________________ 2

Conformable contact. 645%

Deseret limestone: Dark-blue cherty limestones without sandstone beds, except very locally.

Sandstones and quartzites make up roughly 30 per

c~nt ?f the above section, and in this respect the sectIOn IS probably typical of the formation. The general absence of finer clastic material is striking in

view of the numerous alternations of limestone ~nd

coarser clastic rocks. '

The field discrimination between sandstone and

q~artzlte waf; made on the basis of scratching tests

WIth the geologic .pick. It is probable that few of

the b~ds ~~signated quartzite are cemented throughout WIthSIlIca,but certainly many of them are in large

part ~o cemented. To a certain extent this may be a

surfiCIal ?~enomenon connected with weathering, but

much of It ISassuredly not of this origin.

Microscopic examination shows that the sandstones

are co~posed of subrounded grains of quartz with

subordmate amounts of microcline and plagioclase.

The grain size of the specimens studied was very uniform, ranging between about 0.2 and 0.3 millimeter in

diameter .. In the specimens examined microscopically, calcIte cement was predominant over silica.

The variations in the Humbug (Spurr's "Lower

Intercalated series") from place to place were noted

by Spurr,87 who measured two sections about threequarters of a mile apart. One of these was considerably greater than the other, the beds of sandstone bein?, thic~er and more numerous and separated by

thICker lImestone beds. One section had 19 beds of

s~n~stone, the other only 14, and the lensing out of indIVIdual beds was observed in the field. The thickness

(120 feet) of one of the sandstones he measured is

much greater than that of any measured by the writer

and still further illustrates the lateral lensing of the

beds.

Age (JffI,dJ cOrr'elation.-Fossils collected from the

Humbug in Ophir Canyon were referred t G H o . .

Girty for study. His report is as follows:

The Humbug formation has given us two collections, 5800

and 6257. The fauna is a rather small one, and its closest

affinities are with the earlier faunas of thl;l Brazer limestone.

5800: Humbug formation, north side of Ophir Canyon, about

1% mIles below Ophir, Utah; collected by Sidney Paige:

Fenestella, several sp. Orthotetes? sp.

Pinnatopora sp. Productus brazerianus.

Polypora sp. Girtyella? sp.

Rhombopora sp. Spirifer aff. S. centronatus.

Productus ovatus?

Productus sp.

Pugnoides aff. P. ottumwa.

Spirifer n. sp. aff. S. breckenridgensis.

Regional correlation of the Humbug formation in

view of its considerable local variations would s~em ,

rather dubious, yet it seems not unreasonable to extend the usage of the name to this area from ~intic

where the formation was established.88 This correla~

tion is based partly on the age determination from fossil ?vi~ence and partly on the remarkable lithologic

SImIlarIty of the two sections, not in details which

differ very greatly, but in the larger features, 'such as

the presence of interlensing brown quartzite brown

and reddish sandstones, and blue and gray li~estones

with a very little shale. It is probable that the base of

the formation as delimited at Ophir is not at the exact

horizon of the base at Mercur and that both of these

differ from the base at Tintic, but the fairly comparable

pre-Humbug Mississippian sections of 1100 feet at

Ophir and an uncertain total of about 1500 feet at

Tintic seem to point to their essentially si~ilar stratigraphic relations being due to a close age equivalence.

This correlation has been previously suggested by Olmstead 89and seems strengthened by the presence of similar lithology in the Mississippian at so distant a locality as Gold Hill,90in the Deep Creek Range, Utah. At

Gold Hill, however, there is very little limestone of

post-Madison age beneath these rocks, and they may

I'.epresent a somewhat greater age than the Humbug,

though the fact that they orverlap the Madison and

locally rest on Devonian may indicate that there was a

considerable post-Madison time interval before their

deposition. Loughlin 91reports lithologically similar

rocks of upper Mississippian age in the Lake Mountains, just east of the Fairfield quadrangle. Interbedded limestolIlesand quartzites in the Cottonwood

q:ua~rangle seem also closely comparable. Deposits so

SImIlar and unusual at localities so widely separated

seem likely to represent a unit of deposition. It seems

highly probable that the Humbug is equivalent to a

rart of the type Brazer-what part, however it will

. '

reqUIretracing through intervening areas to determine.

Oonditions of deposition.-The presence of such a

series of clastic rocks as the quartzites of the Humbug

formation undoubtedly connotes their origin in localities accessible to considerable currents. Yet the fine

88 Tower, G. W., and Smith, G. 0., The geology and mining indu8try

of the Tintic district, Utah: U. S. Geoi. Survey Nineteenth An~.

Rept., pt. 3, p. 626, 1899.

•• Olmstead, S. G., op. cit., p. 443.

•• Nolan, T. B., op. elt.

01 Loughlin, G. F., op. cit. (Prof. Paper 107), p. 42.
limestones, which rest directly upon the quartzites and

interfinger with them, must have required, it would

seem, a depositional environment free from powerful

currents. Apparently the conditions demanded are

those of alternating periods of active currents and

calm, and for this reason the totally insignificant quantity of silt in the formation is very striking and may

indicate that the sediments were supplied by the erosion of a terrane consisting dominantly of quartzose

and limy sediments, and probably not from an igneous,

metamorphic, or shaly land mass.

Distribut'ion and topographic expression.-Above

the Humbug formation is the" Great Blue" limestone,

which crops out over most of the southwestern part

of the Oquirrh Mountains. South and southwest of

Soldier Creek and Manning Canyon most of the mountain area is covered by this great limestone. Only in

the canyons are older formations exposed. Its area of

outcrop in this part of the range exceeds 33 square

miles.

The formation is likewise exposed on the east flank

of the range, where it is brought to the surface by the

Long Ridge anticline. This eastern outcrop covers

an area of 5 or 6 square miles, from Iron Canyon on

the north to the alluvium south of Bald Knoll. Another exposure, believed to represent this formation,

occurs in the extreme southwest corner of the Stockton

quadrangle, in the foothills of the Stansbury Range.

Over most of its outcrop the "Great Blue" limestone

forms slopes that are considerably less rugged than

those of the Humbug formation below and the Oquirrb

formation above, though here and there it makes

ledges of considerable height.

Stratigraphy.-The "Great Blue" limestone rests

conformably on the Humbug formation, the boundary,

which is purely arbitrary, being placed at the top of

the highest considerable group of sandstone beds.

Sandstones occur higher in the section, in the lower

1,000 feet of the" Great Blue," but these are sporadic

individual lenses, and the boundary is placed to. mark

the practical cessation of notable sandy deposition.

The " Great Blue" limestoiIleconsists of a lower and

an upper limestone, separated by shaly beds herein

named the Long Trail shale member. The lower limestone member, between the top of the Humbug and the

base of the Long Trail shale, is, according to the mean

of four measurements, about 500 feet thick. The thickness as given by Spurr 92 is about twice this figure, but

the four measurements by the writer agreed within 100

feet, and although exposures are not sufficiently complete to make this thickness certainly correct, some confi.denceis felt that this approximation is fairly close

to the truth.

Because of its close association with the great ore

bodies of Mercur and with the Oil'esof the Mono mine,

in Dry Canyon, as well as its value as a stratigraphic

marker, the black carbonaceous shale that separates the

thick limestones of the" Great Blue" has been mapped

as a distinct member. The name Long Trail shale

member is herein applied to it because of its excellent

exposure at the head of Long Trail Gulch, in Ophir

Canyon. Elsewhere this shale is very poorly exposed,

as it weathers much more readily than the limestones

between which it lies. The only thoroughly satisfactory exposure of the unit throughout its extent is that

at the head of Long Trail Gulch, where it is about 85

feet thick. Elsewhere it appears to be much thinner,

but its topographic importance !is a valley maker is so

great that the measurement is thought tol be fairly

representative of the member throughout the area.

Overlying the Long Trail shale is the upper limestone member of the" Great Blue" limestone, consisting of blue-gray limestone like that beneath the shale

and containing sporadic chert layers, some sandy limestone, and a very subordinate quantity of black shale.

This upper limestone member was measured at three

places. A measurement east from the head of Silverado Canyon gave 2,400 feet; one at Mercur gave

nearly 3,100 feet; and the third, on Bald Knoll, on the

eastern flank of the range, yielded a figure very nearly

the mean of these-2,725 feet. It is practically certain that no real changes so great as these occur in the

thickness of the "Great Blue" within distances so

short, and the differences are almost surely due to

errors in measurement. These errors are doubtless

due to variable dips in the limestone, the changes in

which are difficult to evaluate.

If the mean of the three measurements is rounded

off at 2,750 feet and used as the most probable thickness of the upper limestone member of the "Great

Blue," the total thickness of that formation is about

3,600 feet. The total thickness of the "Great Blue"

limestone, if the" upper shale" of Spurr 93 (the Manning Canyon shale of the present report) is taken as

its upper limit, is given by Spurr as 3,525 feet, a fair

agreement in total,' despite the discrepancy between

his measurement of the thickness of the lower limestone member and that of the present report.

Other than the Long Trail shale member, no good

marker beds were discovered in the "Great Blue"

limestone: it is a monotonous thick series of limestones throughout. In local areas, as at Mercur, individual thinner beds, mostly shales, were recognized

in the formation, and it is probable that similar distinctive members could be determined in many other

parts of the quadrangles, but such distinctions must

rest upon much more detailed work than was possible

in this survey.
Age and aOr'r'elation.-The "Great Blue" limestone

was named by Spurr from its exposures in the Mercur

district. The name has become so firmly established

among the mining men of Utah that its retention

seems best, despite the fact that it indicates no definite

type locality and has no geographic significance. The

fossils collected from the lower part of the formation

by Spurr were determined by Schuchert to be lower

Carboniferous (Mississippian). The upper part was

considered probably upper Carboniferous (Pennsylvanian). Fossils collected from the "Great Blue"

limestones during the present survey have been examined by G. H. Girty, who reports as follows:

From the" Great Blue" limestone we have three collections

definitely located stratigraphically-lot 6018, from the lower

part, below the Long Trail shale member; lot 6020, from the

Long Trail itself; and lot 6258, from about 1,000 feet above

the Long Trail shale. The fauna of lot 6018 is not especially

distinctive, but I should group it with the preceding faunas

and assign it on broad lines to the lower part of the Brazer

limestone and the middle part of the typical Mississippian.

The fauna of lot 6020 is sui generis by reason especially of

the large pelecypod representation, though naturally most of

the species are related to species that we know already. This

fauna is in marked contrast to those that preceded it and also

to those that followed it, without suggesting a great difference

in geologic age. Tentatively it may be referred to the lower

Brazer and to the middle Mississippian. The fauna of lot

6258 is small and the specimens not well preserved. It carries

suggestions of a younger facies than the preceding faunas but

has nothing decisive. Provisionally this lot may be grouped

with those already considered.

It remains to discuss a few lots whose stratigraphic relations were not obvious in the field. These are 6264, 6264a,

6267, 6270, and 6272.

Lot 6270 is remarkable in several ways, especially in containing numerous Pentremites, though unfortunately these

fossils occur in such a condition that they can not be identified

specifically. Tentatively the age may be placed at high middle

or upper Mississippian. Nothing in the Mississippian collections just discussed shows the same peculiar feature, however.

Another fauna of striking individuality is represented by lots

6264 and 6264a, which probably represent about the same horizon and fauna. Nothing closely comparable to this fauna is

found in any of the other collections, whether of Mississippian

or Pennsylvanian age, and their geologic age must be given in

a very qualified way, inasmuch as it rests on very general

relations Tentatively the age may be set down as upper

Mississippian, though it is not specifically related to any of

the typical Mississippian faunas nor closely allied to any of

those called Mississippian in the same area, in the Gold Hill

area, or in the Brazer of Idaho, although this assignment

would of necessity make it Brazer. It is to be borne in mind,

however, that this fauna is much larger and more varied than

most of the Mississippian faunas from the Oquirrh Mountains

and that some of the other collections might be of the same

age as this and contain a few of the same species without showing a resemblance that was very obvious or that could be

relied on for correlation. Lot 6272 appears to be Mississippian

also, judged by its general character, yet it has no counterpart

in the other Mississippian fauna of this area nor yet in the

Gold Hill area; still less in the typical Mississippian faunas

of the Middle West. The evidence on which it is assigned

may be unreliable in view of the new values in range that

certain types appear to hold in the faunas of western Utah.

Collection 6267, on the paleontologic evidence, definitely b~

longs in the Brazer.

6018. Limestone low in "Great Blue," just east of Lakes of

Killarney fault, 6,400-foot contour, between Ophir and Dry

Canyons, Stockton quadrangle; collected by James Gilluly:

Echinocrinus sp. Pugnoides aff. P. ottumwa.

Fenestella sp. Girtyella indianensis?

Chonetes capax? Spirifer n. sp. atf. S. pellensis.

Productus ovatus. Composita trinuclea.

Avonia sp. Cliothyridina sublamellosa.

Productus richardsi? Myalina sp.

6020. From Long Trail shale at mouth of pr-ospect tunnel on

south side of Ophir Canyon opposite baseball grounds; collected

by Edwin Kirk and M. J. Buerger:

Fenestella several sp. Cardiomorpha? sp.

Cystodictya atf. C. lineata. Sphenotus atf. S. vulgaris.

Rhombopora sp. Allerisma? sp.

Lingula afl:. L. varsoviensis. Yoldia atf. Y. multistriata.

Lingulidiscina sp. Leda atf. L. stevensiana.

Chonetes afl:.C. oklahomensis. Schizodus sp.

Productus ovatus. Posidonomya fragosa?

Productus semireticulatus. Myalina arkansana?

Pustula atf. P. vittata. Myalina afl:. M. keokuk.

Avonia atf. A. arkansana. Myalina sp.

Camarotoechia afl:. C. purduei Aviculipecten afl:.A. tahlequahval'. agrestis. ensis.

Pugnoides afl:. P. ottumwa. Aviculipecten atf. A. talboti.

Spirifer afl:. S. pellensis. Aviculipecten sp.

Composita atf. C. trinuclea. Aclisina? sp.

Cliothyridina sublamellosa.

6258. "Great Blue" limestone, about 1,000 feet stratigraphically above the Long Trail shale member, west of road to Gisborn, just above alluvium; collected by G. H. Girty, Gordon

New, and James Gilluly:

Stenopora sp.

Batostomella sp.

Fenestella sp.

Rhombopora sp.

Schizophoria? sp.

Orthotetes atf. O. kaskasiensis.

Chonetes afl:. C. levis.

Productus ovatus.

Productus atf. P. inflatus.

Productus afl:. P. parvus.

Diphragmus? sp.

Composita sp.

6264. From fault block west of Lakes of Killarney fault, just

north of Dry Canyon; possibly contaminated by fioat, but probably not; collected by G. H. Girty and James Gilluly:

Triplophyllum sp.

Stenopora afl:. S. ramosa.

Stenopora &p.

Anisotrypa sp.

Fenestella several sp.

Polypora sp.

Rhombopj>ra sp.

Chonetes atf. C. oklahomensis.

Productus ovatus.

Productus ovatus val'. minor.

Productus afl:. P. richardsi.

Productus afl:. P. parvus.

Productus semireticulatus.

Productus afl:. P. infiatus.

Productus atf. P. gallatinensis.

Productus afl:. P. viminalis.

Avonia atf. A. arkansana.

Avonia sp.

Pustula sp.

Pustula n. sp. atf. P. biseriata.

Pustula· sp.

Pustula? sp.

Camarophoria atf. C. explanata.

Dielasma atf. D. formosum.

Spirifer atf. S. arkansanus.

Spirifer atf. S. missouriensis.

Spirifer afl:. S. leidyi.

Spiriferina spinosa.

Reticularia setigera?

Ambocoelia sp.

Composita atf. C. subquadrata.

Cliothyridina sublamellosa.

Naticopsis &p.

Griffithides sp.
6264a. Same locality as 6264, from bedrock:

Campophyllum torquium. Productus ovatus.

Stenopora sp. Composita afr. C. subquadrata.

Orthotetes afr. O. kaskaskien- Cliothyridina sublamellosa.

sis. Griffithides sp.

Productus afr. P. coloradoensis.

6267. From" Great Blue" limestone at extreme southwest

corner of Stockton quadrangle, from foothills of Stansbury

Range; collected by G. H. Girty:

Clisiophyllum? sp. I Productus brazerianus.

Orthotetes? sp. Deltopecten? sp.

6270. From foothills of Oquirrh Mountains, south of Dry

Canyon, west of Lakes of Killarney fault, near Lakes of Killarney mine; collected by James Gilluly:

Triplophyllum sp. Productus afr. P. gallatinenPentremites sp. sis.

Echinocrinus sp. Diaphragmus elegans?

Crinoidal fragments. Spirifer afr. S. pellensis.

Glyptopora sp. Spiriferina spinosa.

Fenestella sp. Composita afr. C. trinuclea.

Polypora sp. Cliothyridina sublamellosa.

Schizophoria n. sp.

6272. Bald Knob, Fairfield quadrangle, "Great Blue" limestone; collected by James Gilluly and W. D. Mark:

Tripiophyllum sp. Conocardium sp.

Stenopora sp. Streblopteria tenuilineata?

Orthotetes? sp. Astartella sp.

Chonetes afr. C. levis? Bellerophon afr. B. sublevis.

Productus ovatus. Euphemus sp.

Productus afr. P. gallatinensis. Pleurotomaria 2 sp.

Avonia? sp. Goniospira? sp.

Spirifer aff. S. leidyi. Holopea afr. H. proutana.

Spiriferina spinosa. Diaphorostoma aff. D. peoriEumetria verneuiliana. ense.

Composita subquadrata. Bulimorpha afr. B. inornata.

Cliothyridina sublamellosa. Straparollus afr. S. subumbiliCardimorpha? sp. catus.

Nucula afr. N. subrotundata. Aclisina sp.

Schizodus sp. Griffithides sp.

The upper Mississippian age of the" Great Blue"

limestone is seen to be firmly established. Doubtless

it finds its correlatives in the limestones of this age

that immediately succeed the Humbug type of sediments in adjacent portions of Utah. In the present

state of our knowledge detailed correlations with other

areas are almost impossible, owing to the absence of

recognizable fossil zones in the upper Mississippian of

the Rocky Mountains. However, it seems pertinent

to point out the similarity between the" Great Blue"

limestone of the Oquirrh Mountains and the Ochre

Mountain limestone 04of the Deep Creek Range, each

consisting of a great thickness of limestones with an

intercalated shale member and each conformably overlying the Humbug formation. Each formation is upper Mississippian and is followed by black shales and

quartzites within which occurs the PennsylvanianMississippian boundary. Possible correlatives of the

9' Nolan, T. B., Paleozoic formations in the Gold Hill quadrangle,

Utah: Washington Acad. Scl. Jour., yo!. 20, pp. 430-431, 1930.

" Great Blue" limestone may exist in the Cottonwood

district,05 the San Francisco district,06 and the Randolph quadrangle 07and adjacent parts of Idaho,os inasmuch as the upper Mississippian is represented in

those areas, but the lithologic similarities are apparently slight, and it hardly seems profitable to discuss

the question in the absence of more definite faunal

zones than have been so far recognized in this

region.oo

:MISSISSIPPIAN AND PENNSYLVANIAN SERIES

Distribut'ion and topographic ewpression.- The formation here named the Manning Canyon shale crops

out in a rather narrow band from Manning Canyon

on the southeast over the divide to the valley of the

E'outh fork of Ophir Creek. Its outcrop follows the

east side of the valley of the south fork into Ophir

Canyon, which it crosses about half a mile above the

forks. Here its position is somewhat doubtful owing

to brush cover and slide rock, but after some displacement by faulting the outcrop trends northwestward,

up the north side of Ophir Canyon, and thence down

the south fork of Soldier Creek. The outcrop swings

westward and determines the main valley of Soldier

Creek to a point within a mile of its mouth but here

diverges from the creek and climbs the north wall of

the canyon. Just north of the canyon mouth it is cut

off by a rather large fault of the Basin Range system.

Several small outcrops interpreted to belong to this

formation occur in the low foothills on the west flank

of the range near the Lakes of Killarney mine, between Dry and Ophir Creeks, and others occur just

south of Ophir Creek across from the Bates ranch.

On the eastern slope of the range the Manning Canyon shale crops out in a northwestward-trending belt

from Threemile Canyon to the head of Iron Canyon,

where it swings sharply east and then southeast. Exposures are very poor farther southeast, but it seems

very probable that the main valley of West Canyon

below Iron Canyon is in part determined by the presence of this soft, easily eroded shale. However, other

factors are involved, and it is possible that the formation is faulted out and does not determine the lower

course of West Canyon.

Throughout its a-rea the Manning Canyon shale is

a valley-forming formation, and because it is relatively impervious to water it gives rise to numerous

springs. Owing to these springs the vegetation is

much more flourishing on this shale than on the other

formations, and exposures are very poor. Structural

95 Calkins, F. C., op. cit. (Prof. Paper 111), pp. 238-239.

96 Butler, B. S., op. cit. (Prof. Paper 80), p. 29.

97 Richardson, G. B., op. cit., PP. 413, 414.

98 G1rty, G. H., in Mansfield, G. R., op. cit., pp. 63-71.

99 For a discussion of the unsatisfactory character and distribution

of the Brazer fauna, see Girty, G. H., idem.
and stratigraphic details respecting the formation are

accordingly very difficult to obtain.

Stratigmphy.-The lower boundary of the Manning

Canyon shale is exposed in only a very few places

within the Stockton and Fairfield quadrangles. Perhaps the clearest exposure is that on the north side of

Soldier Canyon about a quarter to half a mile above

the mouth. In this locality the "Great Blue" limestone becomes more shaly toward the top and by interbedding of limestone and shale, with increasing quantities of shale, passes by gradation into the dominantly

shale unit, the Manning Canyon shale. The gradation

occurs through a series of beds about 200 to 300 feet

thick.

Because of the position of the Manning Canyon

shale between two very thick and strong formations,

it has been decidedly squeezed and deformed by the

forces that folded the strata, the contortion and differential thinning being so great that it is doubtful

whether a section measured at any place in the quadrangles can be considered accurate within about 30

per cent. Nevertheless, four nearly complete sections

and several partial sections were measured, but, as was

expected, they yielded very inconsistent figures fo[' the

thickness of the formation. The results of the four

measurements are as follows: At the saddle west of

Lewiston Peak (top uncertain within 200 feet), 't50

feet; south side of Hall Canyon (base not exposed) , 980

feet; north side 0:£Hall Canyon (base not exposed),

1,140 feet; near mouth of Soldier Creek, 1,140 feet.

Probably the last measurement is the most reliable,

but it must be considered only a rough approximation

to the thickness of the formation where it is undisturbed. These differences in the measured thickness

may indicate either lateral depositional thinning or

an erosional unconformity within the formation, but

inasmuch as the strata measured are all disturbed and

squeezed, there is doubt as to the differences having

any real stratigraphic significance; they may all be

due to differential compaction during the folding.

It is believed that an assumption of an unconformity

within the formation would be, on the evidence at

hand, gratuitous, although Hintze 1 reports one at this

horizon in the Wasatch Range.

The section measured in Soldier Canyon is believed

to represent the formation better than any 0:£ the

others, and although none of the members could be

traced or recognized over any considerable distances

along the strike, it is given in some detail in order to

furnish data for the discussion of the fossil evidence

regarding the boundary between the upper Mississippian and the Pennsylvanian which occurs within

the formation.

1Hintze, F. F., jr., A contribution to the geology of the Wasatch

Mountains, Utah: New York Acad. Scl. Annals, vol. 23, PP. 115-120,

1913.

Section of Manning Oanvon shale measurell on north sille of

Soldier Oanyon about half a mile above its mouth

Oquirrh formation: Limestone, in beds as much as 1

foot thick, carrying plentiful fossils. (See collection

6266a, made about 300 feet stratigraphically above the

base.)

Conformable contact.

Manning Canyon shale: Feet

1. Limy shale and shaly limestone, interbedded,

carrying a fauna represented by collections

6260 and 6266 in a limestone bed about the

middle of the member______________________ 185

2. Dark shale, with a few thin limestones interbedded_____________________________________ 235

3. Thick-bedded gray limestones, forming a ledge__ 32

4. Black shale, without fossils___________________ 78

5. Thin-bedded limestone carrying fossils represented by collections 6259, 6265, and 6265a____ 1

6. Dark-gray carbonaceous shale, unfossiliferous__ 150

7. Brown-weathering quartzite, forming a ledge___ 4

8. Dark-gray shale______________________________ 147

9. Gray limestone, in beds about 2 feet thick______ 12

10. Chiefly shale, with some interbedded limestone__ 35

11. Limestone, in beds about 2 inches thick________ 17

12. Carbonaceous shale___________________________ 43

13. Limestone like bed 11, carrying fossils_________ 40

14. Carbonaceous shale___________________________ 78

15. Limestone, like hed 11________________________ 8

16. Concealed, probably chiefly shale, but with some

limestone 75

Conformable contact. 1,140

"Great Blue" limestone: Shaly limestone interbedded

with less shaly material, the shale decreasing in abundance downward.

At several localities quartzite beds with thicknesses

as great as 40 :£eetwere seen in the formation. These

beds appear to be very lenticular, however, and though

found in nearly every section which is at all well exposed, they can not be traced for any considerable

distance.

As noted in the section given above, the upper contact of the Manning Canyon shale is, like the lower

contact, conformable, and the transition to the adjacent formations both above and below is a gradual one.

If any unconformity is associated with the formation,

it must lie within it. The lithology of the formation

represents deposition in much shallower waters than

those in which the formations above and below it were

laid down, but no evidence was discovered that shows

that the region was emergent at any time during the

interval, although it may have been.

Age and co-rrelation.-Abundant fossils were obtained from this formation during the survey by G. H.

Girty and the writer. Mr. Girty's study of the collections, a report of which is given below, showed

that the Manning Canyon shale is in part upper Mississippian and in part Pennsylvanian. It was first

thought that the quartzite (No. 't) of the section in

Soldier Canyon marked the base of the Pennsylvanian.
This supposition was, however, proved erroneous by

the work of Mr. Girty, who discovered in several

localities, including the one described above, typical

Chester (upper Mississippian) fossils at horizons

above the lowest quartzite beds of the formation. It

is true that in one locality, not far from the place

where the section was measured, a quartzite member

occurs between the highest Mississippian and lowest

Pennsylvanian fossils found, but this quartzite is not

the lowest in the section, an even more prominent one

beneath it at the same locality being succeeded by

fossiliferous limestones of Chester age. Owing to

the poor exposures and absence of distinctive beds it

proved impossible to distinguish the Pennsylvanian

and Mississippian portions of the formation in mapping; the accompanying geologic map accordingly

shows the distribution of the lithologic (not time)

unit.

The Manning Canyon shale is the" upper shale" of

Spurr's" Great Blue" limestone.2 The thickness, reported by him "somewhat more than 100 feet," is

much too small, but the error is due to the very poor

exposures in the area which he studied.

Similar lithology is found in the Manning Canyon

formation of the Gold Hill quadrangle, Utah,3 where

the formation likewise includes the lowest Pennsylvanian rocks and may possibly contain some upper

Mississippian rocks. No other comparable beds in this

stratigraphic position have yet been described from

Utah, so far as the writer is aware.

Mr. Girty's discussion of the fossil collections if'

as follows:

Five collections were made in the Manning Canyon shalelots 6259, 6260, 6265, 6265a, and 6266. Lot 6265 contains little

that is distinctive, but it is interesting inasmuch as the pelecypod representation strikingly recalls that of the Long Trail

shale (lot 6020). Lot 6265a, from about the same locality and

horizon, does not contain those pelecypod species but does contain other forms that indicate an upper Mississippian and

upper Brazer age. The same is true also of lot 6259. I should

remark, however, that the upper Brazer fauna in its integrity

has not been found in the Oquirrh Mountains, and the Oquirrh

faunas are called upper Brazer less because they agree exactly

with the typical upper Brazer and more because they appear to

be correlative, like the typical upper Brazer, with the Chester

faunas of the Mississippi Valley. Even in Idaho the terms

upper Brazer and lower Brazer do not imply as a rule any

definite boundaries. We know only that certain collections are

stratigraphically lower and paleontologically older, in appearance at least, than others. No sharp distinction can at present

be made either in the faunas of the Oquirrh Mountains, and

from these facts it would follow that the boundary between

upper Brazer and lower Brazer may not be taken at the same

horizon in the two areas.

Collections 6260 and 6266 came from the upper half of the

Manning Canyon shale and are of Pennsylvanian age. Inasmuch as this fauna immediately follows one of Chester age,

2 Spurr, J. Eo, op. cit., p. 375.

8 No.1an, 'r. B., op. cit.

it should contain (and probably does) beds that can be correlated with the Pottsville, but as the Pottsville faunas of the

West would presumably differ materially from the Pottsville

faunas of the East, and as the Pottsville deposits of the East

are either nonmarine or contain faunalil only partly described,

the problem here is a rather delicate one. In the Gold Hill

district there occurs a series of beds which I at first believed

to be upper Mississippian but which later with Mr. Nolan's

help I decided to correlate with the Pottsville. The Pottsville faunas of the Gold Hill area, though not very varied,

were abundant and well preserved. The same facies is poorly

represented in the collections from the Oquirrh Mountains,

though I seem to recognize it there, especially in lots 6260

and 6266. Other lots (notably 6266a, b, and c, collected low

in the overlying Oquirrh formation) probably belong in the

Pottsville also and quite possibly still others, but their discussion will be included with that of the other collections

from that formation, it merely being pointed out here that

there is no marked faunal change at the top of the Manning

Canyon shale. The boundary between the Mississippian and

Pennsylvanian series occurs within the Manning Canyon shale.

6259. Shale just below the horizon of a second quartzite

along the strike in the Manning Canyon, north side of Soldier

Canyon, about a quarter of a mile above mouth (Chester);

collected by G. H. Girty, James Gilluly, and Gordon New:

Stenopora sp. Diaphragmus elegans var.

Meekopora sp. Pustula sp.

Septopora sp. Avonia aff. A. arkansana.

Schizophoria n. sp. Dielasma aff. D. chouteauense.

Orthotetes aff. O. kaskas- Spirifer aff. S. pellensis.

kiensis. Cliothyridina sublamellosa.

Diaphragmus elegans. Griffithides sp.

6260. From limestone about 300 feet above the middle quartzite of the Manning Canyon shale, north side of Soldier Canyon, about a quarter of a mile above mouth (Pennsylvanian);

collected by G. H. Girty, James Gilluly, and Gordon New:

Hederella n. sp. Pugnoides aff. P. ottumwa.

Stenopora sp. Spirifer opimus var. occidenFenestella sp. taUs?

Cystodictya aff. C. anisopora. Spiriferina spinosa var.

Orthotetes sp. Spiriferina sp.

Productus semireticulatus. Composita subtilita.

Productus aff. P. gallatinensis. Cliothyridina orbicularis.

Produetus ovatus var. minor. AViculipecten n. sp.

Avonia aff. A. arkansana var. Pleurophorussp.

multilirata. Euphemus? sp.

Pustula aff. P. semipunctata.

6265. From shales of Manning Canyon shale on north side of

Soldier Creek about half a mile above canyon mouth, below

middle quartzite; same horizon as collection 6259; collected

by G. H. Girty, James Gilluly, and Gordon New:

Avonia aff. A. arkansana. Ambocoelia? sp.

Diaphragmus elegans? Cliothyridina sublamellosa.

Pustula aff. P. punctata. Cliothyridina sp.

Pustula sp. Sphenotus aff. S. vulgaris.

Dielasma sp. Cardiomorpha? sp.

Spirifer aff. S. increbescens. Leptodesma sp.

Spiriferina sp. Myalina aff. M. monroensis.

6265a. Same as 6265:

Triplophyllum sp.

Meekopora sp.

Orthotetes aff. O. kaskaskiensis.

Chonetes aff. C. levis.

Productus brazerianus.

Diaphragmus elegans.

Avonia aff. A. arkansana.

Spirifer aff. S. increbescens.

Reticularia setigera.
Spiriferina spinosa. ! Leptodesma sp.

Composita subquadrata. SUlcatipinna atf. S; missouCliothyridina hirsuta? riensis.

6266. From limestone in upper 200 feet of Manning Canyon

shale, probably same horizon as collection 6260, north side of

Soldier Canyon, about half a mile above canyon mouth (Pennsylvanian); collected by G. H. Girty, James Gilluly, and

Gordon New:

Lingula sp.

Chonetes sp.

Pustula sp. I

Productus ovatus val'. minor.

Avonia atf. A. arkansana.

Myalina perniformis?

Distribution and topogmpMo eaJpression.-By far

the thickest stratigraphic unit in the Oquirrh Mountains is the great mass of alternating limestones and

sandstones (or quartzites) here named the Oquirrh

formation. The name is assuredly appropriate-this

formation is nearly twice as thick as all the previously

discussed beds together and is the surface formation

over far more than half of the range. It constitutes

practically all of South Mountain and projects above

the alluvium of Rush Valley in a number of knolls

near Morgan Warm Spring.

Owing to the interbedding of limestones and sandstones, rapid erosion of the formation usually produces

a ledge and slope topography, but quartzite and sandstone talus develops rather rapidly and soon masks the

ruggedness of much of the terrane. The topography

produced on the formation is illustrated in Plates 4

and 5.

StraJtigmphy.-The Oquirrh formation,4 to the

lower part of which Spurr applied the descriptive

name" Upper Intercalated series," 5 is, as that name

implies, a great series of interbedded limestones and

coarse quartzites and sandstones, with very little dolomite and only subordinate amounts of shale. Quartzites, or silica-cemented sandstones, greatly predominate over lime-cemented sandstones throughout the

formation, and there seems no systematic relation between the two varieties of cementing material. In

this report the usage of the local mining men will be

followed, and all the coarser clastic beds of the formation will be referred to as quartzites without implying

that only silica-cemented clastic rocks are under disCllssion to the exclusion of the lime-cemented rocks.

It will be clear from the context when the name is

intended to imply the technical distinction.

The boundary drawn between the Oquirrh formation and the underlying Manning Canyon shale is an

• The name OquIrrh appears In a generalized section by C. R. Keyes

(The grand staIrcase of Utah: Pan-Am. GeologIst, vol. 41, p. 37, 1924)

as a formatIon name withIn the ••Weberlan series," but as no descrIption Is gIven and the thIckness as reported Is wholly at variance

with the field facts, It Is thought that no confusion will be caused by

the present usage of the term.

, Spurr, J. E., op. clt., p. 376.

arbitrary one, as the two formations grade into each

other. Where limestone becomes greatly preponderant

over shale, the beds are assigned to the Oquirrh fofmati on. There are few quartzite beds in the lower

1,000 feet of the Oquirrh formation, but they become

thicker and more numerous higher in the section and

constitute by far the greater part of the upper half

of the unit.

The great mines of Bingham Canyon, just north of

the Fairfield quadrangle, are in the higher beds of

the Oquirrh formation. The rocks in this local area

were long ago named the Bingham quartzite 6 and

constitute the upper part of a conformable series of

which Spurr's "Upper Intercalated series" is the

lower part. The lithologic name quartzite, however,

is hardly applicable to the entire series, for the lower

part is chiefly limestone.

At least 8,000 feet and possibly 10,000 feet of this

quartzite is exposed in the Bingham district.7 About

8,000 feet of the formation is exposed below the lowest

strata of the Bingham area between Butterfield Canyon, at the south edge of the Bingham district, and

the Manning Canyon shale at the head of Iron Canyon. Thus the total thickness ,is probably 16,000 or

18,000 feet, depending on which of the Bingham

measurements is accepted. The possibility of serious

errors in measuring so great a thickness of strata

which are nearly devoid of distinctive beds is very

great, and the result may be in error by 20 per cent

or perhaps more. But that the error ,involved is so

great as to invalidate the order of magnitude of the

thickness derived can be confidently denied, for a

measurement of the section of the Oquirrh formation

exposed between Selkirk Canyon and Iron Canyon

(most of which is an evenly dipping monocline) gives

a thickness of 17,000 feet. At South Mountain, where

neither the top nor the bottom of the formation is

seen, fully 11,000 feet of the formation is exposed

with even westward dips on the southwest flank of

the South Mountain anticline. In fact, it can be said

with some confidence that the stratigraphically lowest

rocks of South Mountain, those at the southeast end,

are fully 3,000 feet and probably as much as 5,000

feet above the base of the Oquirrh formation, so that

the section there indicates a total thickness of the

formation in excess of 14,000 feet.

This tremendous thickness, which far exceeds that

of the Pennsylvanian of any other locality in the entire Rocky Mountain province yet described, is so great

that it appears almost inconceivable that the formation can not be subdivided-indeed, it seems at first

glance that there must be some duplication of strata

• Boutwell, J. M., and others, EconomIc geology of the BIngham

mIning dIstrIct, Utah: U. S. Geol. Survey Prof. Paper 38, pp. 33-50,

1905.

'Idem, p. 35.
by overthrusting or step faulting which has led to

such results of measurements. It can be said with

great confidence, however, in view of the -several sections measured and the simple folded structure of the

beds, that the thickness is real and almost surely in

excess of 15,000 feet.

Diligent search was made to locate distinctive beds

that could be traced in order to effect correlations between the rocks of the Stockton and Bingham districts-one of the principal objectives of the survey.

But detailed study has shown definitely that the

quartzite beds that form so great a portion of the section are all lenticular and vary in thickness remarkably within very short distances along the strike. On

tracing a bed whose thickness may be as great as 300

feet in a given locality it was observed to lens out to

a knife-edge, perhaps within only half a mile. No

single quartzite member of the 13 that were traced

on the west slope of Lewiston Peak, where exposures

are probably better than in any similar area of the

quadrangles, could be followed for more than 4 miles;

moreover, it was established that faulting has not occurred in this portion of the range. There is likewise

evidence that some of the limestones also are lenticular, as has been stated by Keith and Boutwell with

respect to the Bingham section. Their conclusions

regarding the limestones have been questioned, however,s and no unequivocal evidence was discovered during this survey that would prove the lenticular nature

of the limestones in the Stockton district. Nevertheless, several features suggesting such lensing were observed, and, in the opinion of the writer, it is probable

that the lensing of the limestone is original and not

merely due to strike faulting, though it is doubtless

far less prevalent than that of the quartzites.

The three sections plotted in Figure 5 illustrate the

rapid lateral variations in the formation. These sections are, in order from south to north, (1) on the west

spur of Lewiston Peak, which rises above the saddle

between the drainage basins of Mercur and Ophir

Creeks; (2) on the spur forming the south wall of

Hall Canyon; and (3) on the north spur of Hall Canyon. These sections, which were measured with tape

and clinometer, are less than 2 miles apart, and in

fact, Nos. 1 and 2 converge and are less than a quarter of u mile apart at their upper ends, yet it is evident on inspection that the striking lateral changes

between them are so great as practically to preclude

regional tracing of any particular member.

Despite these rapid variations, which prevent correlation of individual beds over any considerable distances, it is possible to map many subdivisions of the

formation in certain areas. This has been done in

great detail in the Bingham mining district by Keith

8 Walker, R. T. (geologist of the United States Smelting, Refining &

Mining C()., Salt Lake City), oral communication.

---

---

_? --

--- ---

-----_?---

---- -_?-- ---

--~~~;?~;;-;;:;~--

II

Sandy limestone

III

GJ

Concealed

FIGURE5.-Partial sections of the lower part of the Oquirrh formation

measured on the west slope of Lewiston Peak, Fairfield quadrangie,

showing laterai variations in beds. Correlations of some of the

larger quartzite members are shown
and Boutwell,9 and in still greater detail, as mining

development has progressed, by the geologists of the

mining companies. Similar work has been done in

the Stockton district" but has not been facilitated by

large-scale maps and has not yet resulted in such detailed knowledge of the stratigraphy as has been obtained in Bingham Canyon. The local stratigraphy in

the Stockton district will be discussed in the section

treating of the economic geology of that area, as it is

of purely local value.

. Despite the failure to effect exact correlations between Bingham and Stockton, it can be stated that the

highest productive bed at Stockton, that in the Ben

Harrison mine, is roughly as far above the base of the

formation as the Butterfield limestone of Butterfield

Canyon (at about the base of the section of the Bingham district). Consequently, as nearly all the productive limestones of Bingham are over 1,000 feet

higher than the Butterfield limestone and by far the

greater part of the production at Stockton has been

obtained from beds about 3,000 feet below those of

the Ben Harrison mine, the local stratigraphy of one

area can be of little or no assistance in the exploitation

of the other unless entirely new ore-bearing beds are

found.

The top of the formation does not occur in the

Stockton and Fairfield quadrangles and may not be

. present anywhere in the range, although that can not

be asserted in the absence of detailed study in the

more northerly areas.

Age and ()()rrelation.-A number of collections of

fossils were made from the lower and middle parts of

the formation during this survey, in part by the writer

and assistants but chiefly by Mr. Girty, who had previously collected extensively from the higher beds in

the Bingham area.10 All these collections are interpreted by Mr. Girty as indicating a Pennsylvanian

age for the formation. His report is as follows:

The Oquirrh formation, on the evidence of the faunas collected, appears to be of Pennsylvanian age throughout. As

stated above, in the discussion of the fauna of the Manning

Canyon shale, some of the lots of both the Manning Canyon

shale and the Oquirrh formation appear to represent the

Pottsville. The lots from the Oquirrh formation which have

a Pottsville facies are 6266a, b, and c. Lots 6262 and 6271,

on the other hand, should find place in the higher Pennsylvanian. Whether the group of beds represented by lots 6263,

6268, and 6269 are Pottsville or a little younger I would hesitate to say. Their faunas are in some respects anomalous.

In the field I referred lot 6263 to the Pennsylvanian, and I

might have referred lot 6268 to the Mississippian if Mr.

Gilluly had not found that its stratigraphic position was above

6263. 'l'he fauna of these three lots does not occur in recog-

• Boutwell, J. M., and Keith, Arthur, Economic geology of the

Bingham mining district, Utah: U. S. Geol. Survey Prof. Paper 38,

pI. 1, 1915.

,. Glrty, G. R., in Boutwell, J. M., and others, Economic geology of

the Bingham mining district, Utah: U. S. Geol. Survey Prof. Paper 38,

pp. 387-393, 1925.

nizable facies among our collections from the Gold Hill district, but it does occur without question in lot 2556b, collected

many years ago in the Bingham district. In reporting upon

the Bingham collections I felt satisfied that this lot was of

Chester age because it contained spirals of the genus ArcMmedies, though I expressed that opinion in conservative language. Lot 6268, however, contains types that either were not

found at all in lot 2556b or were not obtained in identifiable

condition (such as MOIrgmifera splendens). This fact, together with the stratigraphic relations of lots 6268 and 6263,

removes any reasonable doubt that the geologic age of the

former is not Pennsylvanian. Inasmuch as we have in these

collections a type of fossil that has always been regarded as

distinctively Pennsylvanian, Ohonetes mf3solobus, associated

with Archimedes, which is all but confined to the Mississippian, the age of the fauna may fairly be held to be Pottsville.

Indeed, OhoMtes mf3sowbus occurs in abundance in the higher

Pottsville of Ohio and also in beds that overlie the Morrow

group, of upper Pottsville age, in Arkansas.

T,he collections made from the Oquirrh formation in 1926

give little occasion for comment. Some of them may belong

in the Pottsville zone. If so, they carry no recognizable evidence of this fact. For the most part they comprise species

that are common in the post-Pottsville Carboniferous, though

some of the species with scarcely recognizable variation occur

in the Pottsville also. Specifically, I have in mind lots 6019,

6022, 6024, 6024a, and 6025. Of these lot 6019 possesses

especial individuality and is especially distinct from the common run of Pennsylvanian faunas, but I can only point out

its differences, not its affinities. The other lots in the list

below are all referred to the Pennsylvanian, but more definite

assignment is hardly warranted by our knowledge of the range

of the species represented .

6019. From low mound near Morgan ranch, Rush Valley,

Stockton quadrangle; collected by M. J. Buerger.

Cystelasma? sp. Productus semireticulatus.

Lioclema sp. Productus semistriatus.

Rhipidomella carbonaria. Spirifer triplicatus var.

Schizophoria texana. Spiriferina kentuckyensis.

6022. From about the same horizon as collection OO24a. West

spur of Lewiston Peak at 9,950-foot contour, Oquirrh formation; collected by M. J. Buerger.

Syringopora multattenuata. Marginifera splendens.

Triplophyllum sp. Spirifer triplicatus.

Pinnatopora sp. Spiriferlna sp.

Fenestella? sp. Composita subtilita.

Rhombopora lepidodendroideR. Cliothyridina orbicularis?

Rhombopora sp.

6024. From limestone in Oquirrh formation just below

pinnacle at 9,950-foot contour, west spur of Lewiston Peal.,

about 3,500 feet stratigraphically above the Manning Canyon

shale; collected by M. J. Buerger:

Syringopora multattenuata. Productus cora.

Fenestella sp. Productus pertenuis?

Rhombopora lepidodendroides. Marginifera splendens.

Rhombopora sp. Spirifer triplicatus.

Streblotrypa prisca. Squamularia perplexa?

Derbya? sp. Composita subtilita.

Orthotetes aff. O. kaskaskien- Hustedia mormoni.

SiB. Griffithides sp.

Dielasma sp.

6024a. From limestone about 100 feet below collection 6024,

on west spur of Lewiston Peak; collected by M. J. Buerger:

Fenestella sp. I Derbya eras sa.

Polyp ora sp. Chonetes sp.
Productus cora. Spirifer opimus.

Productus cora val'. Composita subtilita.

Pustula nebraskensis? Aviculipecten sp.

Spirifer tripIicatus. Ostracoda indet.

6025. From limestone at 8,900-foot contour on west spur

of Lewiston Peak, about 1,500 feet above base of Oquirrh formation; collected by M. J. Buerger:

Stenopora carbonaria. I Productus cora.

Orthotetes afr. O. kaskaskien- Spirifer opimus val'. occidensis. talis.

6261. From limestone on north side of Soldier Creek about

half a mile west of the canyon mouth, west of the Soldier

Canyon fault; collected by G. H. Girty and James Gilluly:

Syringopora sp. Orthotetes afr. O. kaskaskleDFenestella sp. sis.

Pinnatopora sp. Productus semireticulatus.

Rhombopora lepidodendroldes. Squamularia perplexa.

Streblotrypa prisca? Sphaerodoma? sp.

Cystodictya sp. Griffithides sp.

6262. West end of South Mountain, Stockton quadrangle,

upper part of Oquirrh formation (Pennsylvania) ; collected by

G. H. Girty and James Gilluly:

Fusulina secalica.

Fistulipora sp.

Stenopora afr. S. carbonaria.

Rhombopora lepidodendroldes.

Orbiculoidea sp.

Schizophoria sp.

Orthotetes afr. O. kaskaskiensis.

Chonetes afr. C. verneuilianus.

Productus semireticulatus.

Squamularia perplexa.

Spiriferina spinosa.

Hustedia mormonl.

Pteria? sp.

Acanthopecten carboniferus?

Bellerophon? sp.

Euconospira sp.

6263. East tip of South Mountain, Stockton quadrangle,

north side of Rush Lake, lower part of Oquirrh formation

(Pennsylvania) ; collected by G. H. Girtyand James Gilluly:

Fenestella several sp. Chonetes mesolobus val'. de·

Archimedes afr. A. laxus. cipiens.

Pinnatopora afr. P. pyriformi- Chonetes granulifer.

pora. Productus semireticulatus.

Polypora several sp. Productus ovatus val'. minor.

Acanthocladia n. sp. Squamularia perplexa?

Drymotrypa? n. sp. Hustedia mormoni.

Rhombopora lepidodendroides. Aviculipecten sp.

Streblotrypa prisca. Platyceras n. sp.

Cystodictya sp. Griffithides sp.

Prismopora triangulata?

6266a. From the first 200 feet above Manning Canyon shale,

north side of Soldier Canyon, about half a mile above canyon

mouth; collected by G. H. Girty and James Gilluly:

Hydreionocrinus afr. H. acan- Pustula afr. P. semipunctata.

thophorus. Spirifer opimus val'. occidenFistulipora sp. talis.

Rhombopora lepidodendroides. Spirifer afr. S. wellsianus.

Cystodictya afr. C. divisa. Spiriferina spinosa val'.

Productus cora. Composita subtilita.

Productus semireticulatus val'. J Cliothyridina orbicularis?

Avonia afr. A. arkansana val'. Avicuiipecten afr. A. pelluelmultilirata. dus.

6266b. Scattered up to lowest quartzite of the Oquirrh formation, above collection 6266 and at same locality; collected

through a stratigraphic interval of about 1,000 feet by G. H.

Girty and James Gilluly:

Echinocrinus sp.

Fistulipora sp. I

Fenestella sp.

Rhombopora lepidodendroides.

Schizophoria sp. Spirifer opimus val'. occldeDOrthotetes afr. O. kaskaskien- talis.

sis. Spiriferina sp.

Chonetes sp. Composita subtilita.

Productus cora. Aviculipecten atf. A. pelluclProductus semiretieulatlls val'. dus.

Avonia arkansana? Myalina sp.

Pugnoides sp. Ostracoda indet.

6266c. Above lowest quartzite of Oquirrh formation, same

spur as collections 6265a, 6266, 6266a, and 6266b; includes

fossils from over 2,000 feet of beds extending to the top of

the 7,525-foot hill; collected by G. H. Girty and James Gilluly:

Chaetetes milleporaceus? I Composita subtilita.

Productus cora.

6268. From 200 to 300 feet stratigraphically above lot 6263,

on southeast corner of South Mountain, on next spur south

of lot 6263; contains Archimedes but is stratigraphically above

Chonetes mesolobus; collected by G. iI. Girty:

Sponge spicules. Productus cora.

Triplophyllum? sp. Marginifera splendens.

Fistulipora sp. . Marginifera splendens val'.

Batostomella sp. Pustula nebraskensis?

LeiocIema sp. Pustula afr. P. symmetrica.

Fenestella several sp. Spirifer cameratus val'.

Polypora several sp. Spirifer opimus val'. occidenPinnatopora afr. P. pyriformi- talis.

pora. Spirifer sp.

Pinnatopora sp. Squamularia perplexa?

Archimedes afr. A. laxus. Composita subtilita.

Septopora sp. Acanthopecten carboniferus

Rhombopora sp. val'.

Orbiculoidea sp. Aviculipecten afr. A. pellucl·

Orthotetes afr. O. kaskaskien- dus.

sis. PhilIipsia major?

Chonetes granulifer.

6268a. Essentially the same locality as 6268, 6269, and 6263,

but about 1,000 feet stratigraphically above 6268; collected by

James Gilluly:

Fusulina secalica

6269. Above collection 6263, on same spur, probably overlying horizon of lot 6268, Oquirrh formation; collected by G. H.

Girty and James Gilluly:

Stenopora. Marginifera splendens val'.

Fenestella several sp. Spirifer opimus val'. occidenArchi!Dedes afr. A. laxus. talis.

Chonetes granulifer. Spirifer cameratus.

Pustula nebraskensis. Composita subtilita.

Marginifera splendens. Griffithides sp.

6271. From quartzite at northeast end of Traverse Moun·

tains, in sec. 13, T. 2 S., R. 4 W., Fairfield quadrangle, upper

part of Oquirrh formation; collected by James Gilluly:

Fusulina cylindrica

The Oquirrh formation of the Gold Hill quadrangle 11 cOOlsistsof roughly 5,000 feet of limestone,

sandstone, chert, conglomerate, and shale of Pennsylvanian age and is considered to be a correlative of the

typical Oquirrh formation. It is highly probable

that the Weber quartzite of the Wasatch Range is

equivalent to some part of the Oquirrh formation, but

the Weber is only 2,000 feet thick in the Park City
district and 1,350 feet in Big Cottonwood Canyon,12

thicknesses which are minor fractions of that of the

great Oquirrh formation. Farther north, in the Randolph. quadrangle, according to Richardson,I3 the

Wells formation, the only representative of the Pennsylvanian in that region, ranges from 300 to 600 feet

in thickness and rests unconformably upon the Brazer

limestone. Still farther north, in southeastern Idaho,

Mansfield 14 found the Wells formation to be about

2,400 feet thick and to be unconformable on the Brazer

as well as limited at the top by an unconformity. To

the south, in the San Francisco district,I5 about 1,400

feet of quartzite and limestone assigned to the Talisman quartzite and Elephant limestone are referred

to the Pennsylvanian. Probably all these Pennsylvanian rocks are partial equivalents of the Oquirrh

formation, but exact correlations between these areas

are at present impossible.

Oonditions of deposition.-The remarks on pages

28-29, with reference to the conditions of sedimentation prevailing during the deposition of the Humbug

formation apply with equal force to the deposition of

the Oquirrh formation. The area must have been subjected to widely fluctuating currents, with tremendous

amounts of detritus, almost wholly of sand, supplied

by the strong currents and with great quantities of

lime available for deposition during more quiet times.

The numerous fossils of the limestone layers and the

grain and bedding of the sandstones show that at no

time were the waters very deep, yet no continental deposits have been recognized in the formation, and it

seems likely that the rate of deposition never exceeded

that of depression in the district. This means that

the sea floor on the site of the Oquirrh Mountains sank

for at least 3 miles during the deposition of the

Oquirrh formation and over 4 miles during the whole

Carboniferous period, although that site had been a

stable or even a dominantly positive area probably

from Upper Cambrian time.

REGIONAL CORRELATION OF THE CARBONIFEROUS OF WESTERN

UTAH

The sections of Carboniferous rocks of western

Utah that have been studied in detail are shown diagrammatically in Plate 7. It is evident from these

diagrams that there is no such uniform trend toward

westward thickening of these formations as characterizes the Cambrian formations, nor is there uniformity along a northeasterly line similar to that of

the Cambrian rocks.

More specifically, the Madison rocks show a slight

thinning along an east-west line and finally are over12 Boutwell, J. M., Geology and ore deposits of the Park City district,

Utah: U. S. Geol. Survey Prof. Paper 77, p. 46, 1912.

lS Richardson, G. B., op. cit., p. 415.

14 Mansfield, G. R., op. clt., PP. 71-73.

10 Butler, B. S., op. cit. (Prof. Paper 80), pp. 36-37.

lapped by limestones of Brazer age in the southern

part of the Gold Hill quadrangle. A general tendency of these rocks to thin southward also appears.

With the upper Mississippian an era of very active

sedimentation began in the Oquirrh Mountains. The

eastern edge of the area of greatest sedimentation

must have been between the Oquirrh Mountains and

the middle of the Wasatch Range; toward the west the

section, according to the meager available evidence,

thins much less rapidly. That the depressed trough

which received these sediments on the present site of

the Oquirrh Mountains was not very greatly elongated

parallel to the present structural trend appears likely

from the sections of Plate 7, B. This figure shows

that rocks of this age are less than 2,000 feet thick

both in the San Francisco district and in the Randolph

quadrangle. The Humbug is the highest Paleozoic

formation exposed at Tintic, so it can not be told from

the evidence at hand whether or not the area of great

depression of Brazer time included this district also.

The east-west sections shown in Plate 7, A, show

that conditions during Pennsylvanian time were similar to those of the upper Mississippian. On the site

of the Oquirrh Mountains one of the thickest sections

of the Pennsylvanian yet described in the world was

laid down. The area subject to this great sedimentation was probably rather small, as none of the other

districts that have been studied in the region have

shown thicknesses even remotely approaching this.

Figure 6 brings together in generalized form most

of the data available on the thickness of the Paleozoic

rocks of this portion of the Great Basin.

These sections indicate that the Oquirrh and middle

Wasatch areas, which were near the border of the

Middle Cambrian geosyncline, were subjected to

deeper erosion in pre-Devonian and pre-Mississippian

time, or else that they were consistently seats of less

active sedimentation during the early and middle

Paleozoic than the other areas represented; because,

whereas in the other districts a considerable thickness

of Ordovician rocks rests on the Upper Cambrian, in

the Oquirrh Mountains the Devonian, and in the

southern Wasatch the Mississippian, are the lowest

post-Cambrian rocks present. Whichever interpretation is placed on these stratigraphic relations, they

indicate that the Oquirrh and southern 1Vasatch area,

compared to the other districts of which detailed sections are available, was one of more positive tendency

in pre-Mississippian time. This tendency was reversed in a most striking manner during Carboniferous

time, as is seen from the great thickness of the Carboniferous of the Oquirrh Mountains-over 20,000

feet. This thickness is much greater than that of any

other Carboniferous section so far found in the entire

Rocky Mountain region of the United States. From

a dominantly positive area in pre-Carboniferous time
39

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Top e~oded

SEDIMENTARY ROCKS

the area became, during the Carboniferous, one of the

most strikingly negative areas yet known.

Distribution and topographia ercpression.-Conglomerates and coarse sandstones considered to be of

Tertiary age occur in two small areas in sees. 23

and 26, T. 4 S., R. 2 W., near the northeast corner of

the Fairfield quadrangle. The larger body forms the

crest and upper and western slopes of the prominent

6,355-foot hill; the smaller outcrop is across the gulch

to the southeast. The rock in places is poorly cemented and weathers into slopes but for the most part

is well cemented and forms prominent ledges, especially on the west slope of the hill.

Stratigraphy.-The conglomerate rests with marked

angular unconformity upon a surface of very strong

relief. For the most part the beds of the Oquirrh

formation dip very steeply, and rather high dips occur

also in the conglomerate. The attitude of the conglomerate may be fairly sai.d to be nearly normal to

that of the Oquirrh formation.

The contact between the conglomerate and the Tertiary eruptive rocks is poorly exposed, but inasmuch

as the conglomerate is composed almost wholly of volcanic detritus there can be no question of its younger

age. There is also a very probable overlap of the conglomerate upon the volcanic rocks. Near the contact

there appears to be some discordance in dip between

them, but this is not quite certain.

The conglomerate is in thick beds, rather blocky and

massive. The beds are made up of fine gravel, chiefly

of various volcanic rocks, crystals, and glass. The

fragments are subrounded to subangular, and the

largest are about 5 centimeters in diameter, though

most are nearer 2 or 3 millimeters. They are cemented by silica. The greatest thickness of the conglomerate exposed is on the west flank of the 6,355-foot

hill. Here the rocks dip about 32° N., and about 200

feet of beds were estimated to be present.

Age and aorrelation.-As no fossils were found in

the conglomerate, positive evidence of its age is lacking, and its geologic relations furnish the sole clue.

Inasmuch as the conglomerate is composed of volcanic

debris of evident local origin, it is younger than the

volcanic rocks. The lavas (see p. 65) are almost

surely late Eocene, and this suggests that the age of

the conglomerate is later than Eocene. The fact that I

FIGURE 6.-Eastward shift in site of thick sedimentation

between pre-Carboniferous and Carboniferous time in

western Utah, southeastern Idaho, and eastern Nevada,

as shown by stratigraphic sections. (a) Westgate, L. G., and Knopf, Adolph, Geology of Piocbe, Nev., and vicinity: Am. Inst. Min. and Met.

Eng. Trans., [preprlntl 1647, 1927. (b) Nolan, T. B., Geology and ore deposits ot. the Gold Hill quadrangle, Utah: U. S. Geo!. Survey

report (in preparation). (0) Butler, B. S., Geology and ore deposits of the San Francisco and adjacent districts, Utah: U. S. Goo!. Survey

Prof. Paper 80, p. 29, 1913. (d) Lindgren, Waldemar, and Lougblin, G. F., Geology and ore deposits of the Tintlc mining district, Utah;

U. S. Geo!. Survey Prof. Paper 107, p. ~~, 1919. (e) This report. (f) Butler, B. S., and others, The ore deposits of Utah: U. S. Geol. Survey Prof. Paper 111, pp. 235, 239, 295, 1920. (g) Mansfield, G. R., Geography, geology, and mineral resources of a part of southeastern

Idaho: U. S. Geo!. Survey Prof. Paper 152, pp. 50-52, 1927.
the conglomerate has been strongly folded, with present dips as high as 32° (diverging in a manner which

precludes the possibility that these dips may be original), together with the dissection which has occurred

since the gravel was deposited, leads to the impression

that it is probably pre-Pliocene, and it is here tentatively classified as Oligocene or Miocene.

The facts just mentioned show at any rate that the

conglomerate long antedates the Lake Bonneville

epoch of the Pleistocene, for no folding or erosion

comparable to that which has affected these rocks is

known anywhere in the Pleistocene of the Bonneville

Basin. Furthermore, the altitude at which the beds

occur is such that a very long period of erosion must

be invoked-to account for the removal of the portions

of the conglomerate together with considerable subjacent rock which must once have surrounded the

present residual bodies.

Surficial deposits of Quaternary age occupy a very

large part of the Stockton and Fairfield quadrangles.

These deposits are of four principal varieties-alluvium, including fanglomerate; Lake Bonneville sediments; talus deposits; and glacial moraines. All these

varieties are grouped together on Plate 12.

Rush, Tooele, and Cedar Valleys are very largely

floored with deposits laid down by the streams rising

in the mountains. These deposits form huge fans with

apexes at the mouths of the mountain canyons and

with gradients flattening to lower and lower angles as

the lowlands are approached. In the lower parts of

the valleys they coalesce with and are partly covered

by the lacustrine deposits o,f Lake Bonneville and its

relics, such as Rush Lake.

The material making up these fans is coarsely stratified, of characteristically poor sorting and with little

cementing material, composed of boulders of all sizes,

the largest several feet in diameter, cobbles, sand, and

silt in heterogeneous arrangement. There is little or

no sorting of the finer material from the coarser, and

the included rocks depend in composition solely upon

the source material. To this material, which is the

characteristic alluvium of the Basin and Range province, the name" fanglomerate" has been appropriately

given.16

The thickness of these fanglomerate deposits is of

course variable, depending not only upon the nearness

to the source of material but also on the topography

of the bedrock basement. Several shafts west of Mercur Canyon are at least 300 feet deep and show only

,. Lawson, A. C., The petrographic designation of alluvial-fan formations: California Univ. Dept. Geology Bull., vol. 7, 'pp. 325-334, 1913.

fanglomerate material on their dumps, and a well at

Clover penetrated only unconsolidated sediments to a

depth of more than 1,000 feet.17

Locally, at least, and presumably in areas favorably

situated with respect to the more permeable portions

of the deposits, the fanglomerate is cemented by lime

to form caliche. Even the caliche is usually rather

poorly cemented, however. It is evidently formed at

a temporary perched water table a sh'ort distance below the surface, for it is rarely exposed except in the

walls of the very young gullies that locally strip the

fans.

In addition to the fanglomerate normal stream sediments occur in the lower parts of the mountain canyons. These deposits are all small and nowhere more

than a few feet deep.

The deposits of Lake Bonneville floor the lowest

parts of Rush, Tooele, and Cedar Valleys. These deposits include well-bedded lake silt in the lowest depressions and the coarse gravel and sand spits and

bars which are the direct product of shore processes.

Among these shore features the most striking are the

great bar and spit at Stockton, which have been exhaustively discussed by Gilbert.18

The lacustrine deposits form a veneer over the lower

parts of the alluvial slopes. Within the area of this

survey this veneer is probably nowhere more than a

few feet thick. The smooth concavity of the basins

is due much more probably to reworking of unconsolidated materials by the shore processes of the lake during rising and falling stages than to the deposition of

sufficient silt to mask the alluvial topography.

The talus deposits of the area are generally small.

The largest occur below the cliffs that were oversteepened by glaciation, such as those at the head of Settlement Canyon (pI. 3, 0, B), Mill Canyon, and The

Jumpoff. Where the Humbug and Oquirrh formations appear at the surface, talus is generally present,

owing to the angular character of the quartzite debris

from these formations.

Evidence that very small glaciers, perhaps merely

neve fields, occupied the highest northward-facing

valleys of the Oquirrh Mountains, presumably during

Wisconsin time, is afforded by small cirque lakes, such

as those at the head of the first canyon north of Hall

Canyon and below The Jumpoff; by roches mouton17 Carpenter, Everett, Ground water in Boxelder and Tooele Counties,

Utah: U. S. Geol. Survey Water-Supply Paper 333, p. 77, 1913.

18 Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon. 1, pp.

137, 149-151, pIs. 9, 20, 1890.
nees, seen in these two localities and in Mill Canyo~

and Jackson Hollow; by moraine topography in all

the above-named localities; and by "steps" in the

profile of these several valleys. The glaciers were all

above 8,000 feet and most of them above 8,500 feet in

altitude. The largest was less than a mile long, and

the moraines they left were also correspondingly small,

the largest one, below The J umpoff, being only a few

hundred feet long.

IGNEOUS ROCKS

GENERAL FEATURES

Both intrusive and extrusive igneous rocks occur

in the Stockton and Fairfield quadrangles. The extrusive rocks cover by far the larger area, but except

for a small outcrop near the northeast foot of South

Mountain, in the Stockton quadrangle, they are limited to the northeast corner of the :Fairfield quadrangle. They are chiefly latite and quartz latite, with

some minor flows of basalt, rhyolite obsidian, and

nephelite basalt. Among the extrusive rocks, flows,

although numerous, are quantitatively subordinate to

breccias. The intrusive rocks include numerous small

stocks, dikes, volcanic plugs, and sills, distributed at

intervals from Butterfield Canyon in a belt toward

Stockton and thence down the west front of the range

to the Me'rcur district. No large bodies of intrusive

rock are included in the area, but just north of the

Butterfield Canyon localities is the considerable stock

of the Bingham mining district. The intrusive rock&

are chiefly of monzonitic and rhyolitic composition

but include also andesite (or latite) , lamprophyre, and

nephelite basalt.

The order of eruption is uncertain, as but few contacts between the igneous rocks occur. However, there

is indisputable evidence that at least one of the monzonitic bodies intrudes members of the extrusive series

and is therefore younger.

A striking unconformity between the extrusive rocks

and the underlying sedimentary rocks is conclusive

proof that the volcanism was much later than the

orogenic folding of the Oquirrh Mountains.

SUllDIVISIONS

Volcanic rocks occur in two distinct areas in the

Stockton and Fairfield quadrangles, although there is

considerable probability that the areas were formerly

continuous and have been separated by later faulting

and erosion. The smaller area lies at the northeast

foot of South Mountain, in the Stockton quadrangle,

where a body of hypersthene latite or andesite tuff and

breccia is exposed in a belt a few hundred feet wide

and about 2 miles long. The other area is about 12

miles to the east, on the eastern flanks of the Oquirrh

Mountains, covering most of the northeastern part of

the Fairfield quadrangle. This volcanic field continues

still farther east and covers much of the Traverse

Mountains, including the spur at the Point of the

Mountains, east of Jordan Valley.19 It also extends

north of the Fairfield quadrangle along the base of the

Oquirrh Mountains east of Bingham.20 The volcanic

rocks of this field include augite andesitic latite,21

hypersthene latite, quartz latite, nephelite basalt, olivine basalt; rhyolitic obsidian, and trachyte.22

Field relations.-The volcanic rocks of the northeast foot of South Mountain, in the Stockton quadrangle, include breccias, water-laid tuffs, and flows.

The breccias are the most abundant, though flows are

numerous in the southern part of the area. The interbedded water-laid tuffs give opportunity to ascertain

the attitude of the rocks. They strike about N. 550

W. and dip about 180 NE., so that the flows appear to

underlie the breccias and tuffs. The outcrop of the

volcanic rocks is completely surrounded by alluvium

and lake deposits, which are without question much

younger than the volcanic rocks.

Lithology.-The breccias consist of angular to subrounded fragments, the largest 6 feet or more in

length, set in a matrix of smaller fragments. Bedding

is obscure or entirely absent where the coarser fragments are most numerous but can be determined in

many finer layers. (See pI. 8, A, B.)

A representative collection of specimens from the

larger breccia fragments includes few varieties. The

dominant rock of the breccia is medium to dark gray,

dense, and somewhat vesicular, with recognizable hornblende and plagioclase phenocrysts somewhat less than

1millimeter long in an aphanitic groundmass. Subordinate varieties carry larger phenocrysts, as much as

3 millimeters long. Weathering produces various hues

of purplish gray, red, and red-brown.

Under the microscope the rock is seen to be microporphyritic, with microphenocrysts of plagioclase, hypersthene, augite, basaltic hornblende, and biotite set

in a groundmass of plagioclase laths, some glass, and

7eolites. The texture of the groundmass is felted, with

a rough tendency toward a linear arrangement of the

,. Emmons, s. F., U. S. Geo!. Exp!. 40th Par. Rept., vol. 2, pp. 440-

441, 1877.

,.,Boutwell, J. M., and others, The geology of the Bingham mining

district, Utah: U. S. Geol. Survey Prof. Paper 38, pp. 55-56, 1905.

21 Emmons, S. F., op. cit., p. 440.

•• Zirkel, Ferdinand, Microscopical petrography: U. S. Geol. Expl.

40th Par. Rept., vol. 6, pp. 132, 156, 1816. The" trachyte" from the

Traverse Mountains descrihed by Zirkel would probably be now classed

as a latite. It probably differs but little from rocks described in the

present report as latHe. Although true trachyte has been found in the

area, it was determined only from a few fragments in an andesitic

breccia and can hardly be an important rock in the district.
crystals (pilotaxitic texture). The plagioclase phenocrysts reach 1millimeter in greatest length. They are

strongly zoned, with a composition ranging from about

Ab4oAn6oin the cores to about Ab6oAn4oin the border

zones. Carlsbad, albite, and pericline twinning occurs.

In most specimens hypersthene is the dominant mafic

mineral, although in some it is subordinate to hornblende. The hypersthene occurs in fairly well formed

crystals as much as 1millimeter long. Most of it is

strongly pleochroic (X = Y reddish, Z pale green), but

this feature is variable, and in some specimens the pleo:-

chroism is barely discernible, although the mineral is

readily determined by its parallel extinction, low birefringence, and negative character. Basaltic hornblende is commonly the next most abundant mafic mineral and in a few slides exceeds the hypersthene quantitatively. It is strongly pleochroic (X yellowish

brown, Z=Y dark reddish brown). The extinction

angle is small, ranging from 12° in some specimens to

practically zero. Commonly the hornblende is surrounded by a reaction rim of magnetite and pyroxene.

Augite is a subordinate mafic mineral, not exceeding 3

per cent of the rock. One or two slides show a little

biotite, but it is rare. Apatite and magnetite are accessory primary minerals, and calcite is present as an

alteration product in some slides.

Over 60 per cent of the rock is composed of the

groundmass, which consists of minute plagioclase laths

set in a cryptocrystalline to glassy base. These plagioclase laths can hardly be more calcic than Ab6oAn4o

and may be as sodic as A1:'70An30' Some undoubted

glass is interstitial, but there is probably some alkalic

feldspar in the base as well. A little analcite replaces

plagioclase phenocrysts along cracks, and some opal

lines minute cavities. Very minute radiating crystals

of low birefringence, negative elongation, and low refraction occur in some vesicles and may be tridymite,

but their identity could not be established. The tuffs

were not examined microscopically, but there is no reason to doubt their close relationship with the breccias.

The specimens examined vary so slightly in composition that all may be fairly characterized from their

microscopic features as hornblende-hypersthene andesite. However, the rocks closely resemhle the breccias

of the east flank of the range, which would also be

classed, from their recognizable minerals, as andesites;

but the glassy or cryptocrystalline groundmass contains so much potash that the entire rock proves on

chemical analysis to be higher in potassa than in soda

and falls into the group of latites. It seems probable

that the "andesites" just described would also, on

chemical analysis, prove ti> be latitic. This suggestion

is based not alone on the resemblance of these rocks to

the latites of the Fairfield quadrangle, but also upon

the fact that by far the greater part of the rocks in

western Utah that have been called andesite from

their mineralogy have proved to be latitic when subjected to chemical analysis. Such rocks have now been

described from Park City,23 Tintic,24 San Francisco,25

Iron Springs,2'6 and Gold Hill,27 as well as this area ..

The volcanic rocks of the Traverse Mountains and

the eastern slopes of the Oquirrh Mountains were

poured out over a surface very similar in degree of

dissection though not in geographic relations to that

of the present time. The prevolcanic surface was one

of considerable relief, some of the valleys being not

less than 1,000 feet lower than heights less than a mile

distant. In consequence of this and doubtless in part

because of unequal distribution of the erupted materials and of variations in erosion between successive

eruptions, the volcanic series presents different facies

at its base in different parts of the area. Thul:! the

only volcanic rock in place on the south side of West

Canyon is a small body of olivine basalt just below the

mouth of Iron Canyon. In sec. 2, T. 5 S., R. 2 W.,

in Tickville Gulch, the rock at the base of the voleanic

series is locany a light-green rhyolitic obsidian, but

not far away it is a latite breccia. In the west fork

of Tickville Gulch it is quartz latite, but in the northern part of secs. 3 and 4, T. 5 S., R. 2 W., the lowe::;t

member of the volcanic series is a latite. By far the

dominant materials toward the base of the volcanic

series, however, are latitic pyroclastic rocks, and there

can be little doubt that these rocks represent the principal product of the earliest volcanism of the region.

Flows become increasingly more abundant toward the

top of the preserved portion of the volcanic section,

and east of a line from Oak Spring Canyon to Step

Mountain they form much the greater part of the

senes.

It is quite impossible to determine accurately from

surface observations the thickness of the volcanic rocks

exposed in this area. West of Rose Canyon, in the

angle between this canyon and Water Fork, however,

there is not less than 1,900 feet of latitic breccia with

subordinate lavas. These rocks are overlain east of

Rose Canyon by not less than 1,000 feet of lava and

subordinate breccias. Inasmuch as both these estios Boutwell,J. M., and Woolsey,L. H., Geologyand ore depositsof

the Park Cityminingdistrict,Utah: U. S. Geol.SurveyProf. Paper

77, p. 74, 1912•

••Lindgren,Waldemar,andLoughlln,G.F., Geologyandoredeposits

of the Tintlcminingdistrict,Utah: U. S. Geol.SurveyProf. Paper

107, pp. 55, 63, 67, 1919.

••Butler,B. S., Geologyand ore depositsof the San Franciscoand

adjacentdistricts,Utah: U. S.Geol.SurveyProf.Paper80, p. 49, 1913.

••Leith, C. K., and Harder,E. C., Iron ores of the Iron Springs

district,Utah: U. S. Geol.SurveyBull.338, p. 58, 1908.

'"Nolan,T. Bo,Geologyand ore depositsof the GoldHill quadrangle,Utah: U. S. Geol.Surveyreport (in preparation).
Stockton -Fairfield

ql!adrangles, Utah

(This report)

Tertiary

•

Gold Hill, Utah

IT B. Nolan)

Permiar!

Pennsylvanian?

c:

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U)

;

""Great Blue"

limestone

c

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Long Trail ~'

sh.mem. fb(

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Humbugformation

/ 7. Deseret limestone

/ . Madisonlimestone

San Francisco

district, Utah

(B.S. Butler)

Tinhc d istn ct

Utah

Elephant (G.FLoughlin)

limestone

---120 mile5~ ;<;---30 I

TertIary

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dolomite

Vietoris

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On

A

CORRELATION AND VARIATIONS OF MISSISSIPPIAN AND PENNSYLVANIAN FORMATION~
B. VOLCANIC Tun', OVERLAIN BY ANDESITE BRECCIA, ON DIVIDE BETWEEN STOCKINGS FOHK

AND CITY CANYON, FAIHFIELD QUADRANGLE

C, WATER-LAID TUFF ON DIVIDE BETWEEN CITY CANYON AND WATER FORK, FAIRFIELD

QUADRANGLE
mates are conservative and there has been very considerable erosion, it is quite certain that locally the

original thickness of the volcanic series exceeded 3,000

feet, and it may have been much greater.

The volcanic series of the Traverse and eastern

Oquirrh Mountains has been somewhat deformed since

its extrusion. Eastward dips of 10° to 15° characterize most of the series west of a line between Rose

Canyon and Oak Spring Canyon; east of this line the

rocks lie either nearly horizontal or with dips rarely

exceeding 4° and having no apparent system.. Many

of the water-laid tuff members that are interbedded

with the breccias are composed of such fine materials

that it is highly probable that they could not have had

original dips of more than 1° or 2°. Accordingly the

dips of 10° and more are probably due to postvolcanic

deformation. This deformation was doubtless in part

a result of the eastward tilting of the Oquirrh Mountains as a whole, for which independent evidence is

advanced in the section of this report on structural

geology (pp. 81-88). The minor and apparently unsystematic folding in the Traverse Mountains may

readily have been due to differential vertical movements in the crust above a magma reservoir during

and after its volcanic activity. Similar irregularities

that may have existed west of Rose Canyon could be

detected with difficulty if masked by the dominant

t'astward tilt of the rocks in that area.

A considerable diversity of types occurs among the

volcanic rocks of the Traverse Mountains. Breccias

and tuffs predominate, but flows are very numerous

and of considerable thickness. With two exceptions,

however, despite the variety of structural and textural

characters, all the rocks studied are of latitic to quartz

latitic composition. Microscopic study alone would

classify the rocks almost wholly as andesites or dacites, but chemical analyses demonstrate that nearly

all the flows carry notable quantities of pot assa and

should be classed as latites or quartz latites. However, potash feldspar occurs as phenocrysts only in one

rock collected-a fragment of trachyte from a dominantly latitic breccia. Owing to the relatively poor

exposures of the volcanic series, the considerable relief of its under surface, the lenticular character of its

individual members, and the general lithologic similarity of the breccia fragments and flow rocks, no attempt was made to map the different member!';of the

series. Two varieties whose composition differs notably from that of the main mass of the volcanic rocks

were distinguished in the field. One of these is the

body 9f olivine basalt exposed on the south side of

West Canyon just below the mouth of Iron Canyon.

The other is a small flow of nephelite basalt which

caps a small hill in the NE. % sec. 31, T. 4 S., R. 2 W.,

just east of Sheep Ridge.

Field relations.-Although locally underlain by

flows, as mentioned above, latitic breccias are usually

found at the base and predominate throughout the

lower half of the volcanic series.

Bedding is almost lacking in many breccia members, but most outcrops show a faint stratification or

contain enough interbedded tuff layers to furnish information as to the attitude of the rocks. (See pI.

9, A..) The rock fragments composing the breccia

range widely in size, from dust-like particles to huge

masses 6 or 8 feet long or even larger. No statistical

study was attempted, but the impression was received

that the bulk of the breccia is composed of fragments

ranging from 3 inches to a foot in diameter. No systematic variations in size of the fragments that might

serve as a clue to the source of the material were

discovered.

The principal bodies of latitic breccia lie west of a

line between Rose Canyon and Oak Spring Canyon,

although there are considerable bodies east of this

line. The former extent must have been very much

greater, for fragments of breccia were found on Long

Ridge at the 6,300-foot contour, a few hundred feet

east of bench mark 6604, and other fragments of unmistakably similar rock were seen at an altitude of

7,700 feet on the spur west of the head of Iron Canyon.

Lithology.-The varieties of rock found as fragments in the breccia comprised biotite-hornblende

latite or andesite, biotite-augite latite or andesite, olivine basalt (very little), and biotite-augite trachyte

(only one fragment seen).

The biotite-hornblende latite or andesite, which is

by far the most abundant of the breccia fragments, is

a medium-gray to purplish-gray porphyritic rock that

weathers to various shades of reddish brown and purple. Biotite, plagioclase, and hornblende are recoguizable as phenocrysts, set in a dense groundmass.

A few of the mafic phenocrysts reach 1 centimeter in

length, but the feldspar crystals only exceptionally

exceed 1 millimeter. The microscope shows that the

feldspar phenocrysts are zoned, with a composition

showing the very considerable range from about

AbgoAn7oto about Ab6~Ang~. The zoning is normalthat is, the external zones are more sodic than the

core, with only a few alternations. Albite and carlsbad twins are characteristic. The hornblende is of

the basaltic variety, with X light greenish brown, Y

dark brown, and Z very dark brown. The extinction

angle is 7°. Alteration to magnetite has been intense

along the borders. Biotite, of quite normal pleochroism

and with sagenite crystals well developed, occurs in
€uhedral plates. Magnetite and apatite are accessories.

The groundmass [isfelted, with minute plagioclase laths

Qf composition about Ab65An35 set in a glassy base of

greater or less abundance (hyalopilitic ranging to

pilotaxitic). A little analcite occurs as an alteration

product of the plagioclase. The texture and mineral

composition of this rock are like those of biotitehornblende andesite. The chemical analyses of similar rocks of the area, however, suggest that this too is

really a latite. Some specimens carry augite in addition to the biotite and hornblende. Other varieties

also occur which strongly resemble this except for the

absence of hornblende and a somewhat marked tendency of the plagioclase phenocrysts to lie in aggregates in a decidedly glassy base.

Another rock variety which is prominent among the

breccia fragments is biotite-augite latite or andesite.

This is a dark-gray porphyritic rock, with phenocrysts of biotite in flakes as much as 1centimeter in diameter, pyroxene, and plagioclase (exceptionally as

much as 1millimeter long), in a groundmass too fine

for resolution with the hand lens. The microscope

shows the plagioclase to have a composition close to

Ab1oAnao,being thus much more sodic than the phenocrysts of the biotite-hornblende andesite (latite).

The pyroxene has an extinction angle of 48° and is

normal augite. The rock is vesicular, with opal and

a zeolite resembling phillipsite lining the vesicles.

The groundmass of the rock is more glassy than in

the biotite-hornblende andesite (latite). The texture

is felted, with a glassy base throughout.

Hornblende-augite latites or andesites are also common as fragments in the breccia. The more abundant

variety is a light-gray porphyritic rock with phenocrysts of hornblende as much as 3 millimeters long and

-of pyroxene as much as 1millimeter long, with rare

biotite plates as much as 5 millimeters across, set in a

dense light-gray groundmass. The plagioclase has a

-composition close to Ab1oAnao. The hornblende is a

brown basaltic variety, and the pyroxene is augite.

The texture is felted, with a crude tendency to linear

arrangement of the crystals and with very little glass

in the groundmass. Analcite and a zeolite resembling

phillipsite occur as secondary minerals.

Another variety of hornblende-augite andesite or

latite differs from the one just described in many particulars. This is a red-brown lithoidal rock, with

phenocrysts of plagioclase and hornblende, which

rarely attain 1 millimeter in length, set in a dense

groundmass. The microscope shows the plagioclase

microphenocrysts, which rarely reach 0.5 millimeter

in length, to be of calcic andesine, between Ab5oAn5o

and Ab55An45• They show both carlsbad and albite

twinning. The minute feldspars of the groundmass

are more sodic, about Ab1oAnao. The most conspicuous mafic mineral of the rock is titaniferous augite,

which occurs in beautiful euhedral crystals that rarely

exceed 0.4 millimeter in length and 0.1 millimeteJ" in

diameter. Aggregates of the augite crystals are com:

mono The pyroxene is strongly zoned, with extinction angles of 45° for the inner zone and 51° for the

outer zone, measuring between Z and the a axis. The

birefringence also varies zonally, being about 0.026

in the inner zone and 0.021 in the outer zone. The dispersion is very strong, so that there is no position of

complete extinction in sections parallel to 010. The

pleochroism is faint in reddish brown and yellow, with

Y>Z>X. The cleavage is poor and in many crystals

lacking. These properties indicate a titaniferous augite. Brownish hornblende occurs in fairly large

crystals, which, however, are much altered to magnetite and other minerals. The hornblende is strongly

pleochroic (Z, red-brown, > Y, yellow-brown, > X,

pale greenish yellow). It has an extinction angle of

16°. One or two crystals of biotite occur. Natrolite

and analcite occur in vesicles of the rock, and apatite

and magnetite are accessories. The groundmass texture is pilotaxitic.

The rocks just described are, with the possible exception of the last, obviously all closely related and

resemble the flows with which they are interbedded.

Two varieties of rock, however, occur as fragments

in the breccia but, as far as determined, do not appear

among the main series of flows of the area. These

. varieties are quantitatively unimportant, but they are

worthy of note as indicative of the complexity of the

volcanic history of the area. One fragment is determined to be biotite-augite trachyte; the oither is olivine

basalt.

The trachyte is a medium-gray porphyritic rock

carrying phenocrysts of biotite as much as 8 millimeters long and of pyroxene about 1millimeter long

in a dense groundmass. The microscope reveals the

presence of light-greenish augite, hornblende (totally

resorbed and now represented only by reaction prodl~ctS), biotite, and magnetite as the mafic minerals.

The only feldspar determined is orthoclase, in minute

prisms and carlsbad twins. If plagioclase occurs at

all it must be in very minute crystals in the groundmass. No quartz was seen. The minerals just enumerated rest in a glassy groundmass constituting about

20 per cent of the rock. A partial chemical analysis

shows the rock to be a normal trachyte, though the

OaO content is a little high, which may mean an approach to latite, the dominant volcanic rock of the area.

The olivine basalt was not studied microscopically,

inasmuch as the olivine could be determined megascopically and the rock closely resembles, both texturally and in color, a flow rock from West Canyon

which has been determined as olivine basalt.
Partial analysis of trachyte and analyses of average sub alkaline

trachyte and latite

Si02 ~

CaO _

~a20 _

]{20 _

62.38

5.50

2.68

5.08

63.91

2.81

3.08

5.80

57.65

G 5.74

3.59

4.39

1. Biotite-hornblende augite trachyte, fragment of breccia

near head of City Canyon, Fairfield quadrangle. J. G. Fairchild, analyst.

2. Average subalkaline trachyte. Daly, R. A" Igneous

rocks and their origin, p. 21, ~ew York, 1914.

3. Average latite. Daly, R. A" op. cit., p. 23.

The breccia matrix containing the fragments of the

various rocks just described is composed of finer comminuted fragments of andesitic or latitic rocks and

individual crystals of feldspar and ferromagnesian

minerals. In places it is structureless, but generally a

faint stratification is determinable.

Origin of the brecoia.-The structureless portions of

the breccia may represent consolidated mud flows such

as are common in volcanic eruptions, or they may be

due to accumulations of volcanic bombs, lapilli, and

ash; but the common interbedding of the massive

breccias with definitely water-laid tuffs renders the

probability of their origin as mud flows a little

stronger. It is distinctly possible that the breccias

are of diverse origin.

Beds of true tuff, whose largest fragments are smaller than 1centimeter in diameter, are decidedly subordinate among the volcanic rocks of this field. They are

prominent on the divide between Stockings Fork of

Butterfield Canyon and the head of City Canyon, and

also on the hill between Water Fork of Rose Canyon

and the main canyon. (See pI. 8, B, 0.) Such beds

rarely exceed 10 to 20 feet in thickness and are commonly much thinner, being interbedded with the

.coarser breccias.

The fine-grained pyroclastic rocks of the area are

practically all water-laid, as is indicated by their even

lamination, alternation of coarser and finer layers, and

arrangement of larger fragments in lenses. The tuffs

are but slightly consolidated, very friable rocks, chiefly

very light gray on fresh fracture but weathering vari-

-ousshades of green, yellow, and brown. Examination

under a binocular shows the rocks to be commonly

crystal tuffs, according to the nomenclature of Pirsson,

hut the larger fragments are of rock. Plagioclase,

biotite, and hornblende are recognizable megascopi-

,cally~and there can be no doubt of the close relation-

:ship of the tuffs to the interbedded breccias and flows.

Distribution and st1"lJXJturatrelations.-The most

abundant lava in the Fairfield quadrangle is biotitehornblende latite. From top to bottom of the volcanic

series it is the dominant flow rock. It is especially

prominent as forming most of the hills from Oak

Spring Canyon southeastward toward Tickville Gulch.

It also caps the long flat ridge followed by the boundary between Salt Lake and Utah Counties for several

miles east of the head of Rose Canyon. The flow rocks

predominate over the pyroclastic members in the upper

part of the volcanic series. With the possible exception of the olivine basalt of West Canyon, which is

not in contact with other volcanic rocks, the youngest

volcanic rocks of the area are latite flows.

Lithology.-The principal variety of latite is a lightgray porphyritic rock. Clearly recognizable phenocrysts of biotite, hornblende, and plagioclase, ranging

from 1to 4 millimeters in length, are set in a dense

groundmass. Flow structure is commonly conspicuous

m hand specimens. Weathering results in various hues

of red, brown, and purple. Under the microscope the

plagioclase of the phenocrysts is seen to be faintly

zoned, twinned according to the carlsbad and albite

laws. Its indexes, measured by the immersion method,

and its extinction angles are those of oligoclase-andesine, Ab1oAnso. The minute plagioclase laths of the

groundmass seem to be slightly more sodic, about

Ab15An25' The principal mafic mineral is hornblende,

of the basaltic variety. It is chiefly in crystals from

0.2 to 0.5 millimeter long. It is strongly pleochroic

(Z= Y red-brown to dark olive-brown, X light yellowi~h green). The extinction angle is small and variable,

ranging from a maximum 0& 13° down to O. The mineral is optically negative. Less prominent than the

hornblende is biotite, in plates as much as 2 millimeters

long. It is pleochroic (Y =Z deep red-brown, X light

greenish brown) and practically uniaxial. Augite occurs in minute crystals, mostly less than 0.1 millimeter

long. It is light green, with birefringence of 0.025

(from the interference chart) and extinction angles of

about 45°. Apatite, zircon, and magnetite are accessories. Most commonly the groundmass is hyalopilitic,

but in some specimens glass is subordinate, and the

texture is to be classed as pilotaxitic. Some specimens

show a development of zeolites in vesicles and partly

replacing feldspar phenocrysts. Thomsonite and analcite commonly occur thus.

Variants closely related to the rock just described

include biotite-augite-hypersthene latite and quartzbearing latite that is gradational to true quartz latite.

The hypersthene latite differs very little from the normal biotite-hornblende latite, being indistinguishable

in hand specimens and showing in thin section the
same mineral composition as the biotite-hornblende

latite save for the addition of hypersthene as the chief

mafic mineral. The feldspar of the hypersthene latite

is slightly more calcic than that of the hornblende

latite, being close to AbaoAn4o•

The quartz-bearing latite is practically indistinguishable either megascopically or microscopically

from the normal latite except for the sporadic quartz

crystals. These are very small, and in some slides not

more than two or three rounded grains, less than 0.2

millimeter in diameter, occur. They are commonly

surrounded by narrow reaction rims of minute pyroxene granules. By increase in the number and size

of the quartz phenocrysts, these rocks grade into true

quartz latite. A partial chemical analysis of the

quartz-bearing rock shows it to be a siliceous latite,

with both the alkalies a trifle low but not closely approaching the percentages of the average hornblende

andesite, although its silica content does.

Partial alflalyses of quartz-bearing hornblende latite and of

aoorage latite and average hornblende andesite

SiOz_

CaO _

NazO - _

KzO _

57.65

05.74

3. 59

4.39

61. 12

5. 80

3.83

1. 72

61. 09

4.70

3.00

3. 77

1. Augite-biotite-hornblende latite fr.->IDOak Spring Canyon,

Fairfield quadrangle. J. G. Fairchild, analyst.

2. Average latite. Daly, R. A., Igneous rocks and their

origin, p. 23, New York, 1914.

3. Average hornblende andesite. Daly, R. A., op. cit., p. 26.

None of the rocks just described carry recognizable

orthoclase, and without doubt all would, in the absence of chemical analysis, be referred to the andesite

group. However, parti[lJ chemical analyses reveal

that potassa predominates over soda, and the conclusion seems inevitable that were the rocks entirely crystalline, potash feldspar would be a prominent constituent, comparable quantitatively to the plagioclase.

Accordingly, the rocks are referred to latite.

However, latites with orthoclase crystals occur interbedded in the volcanic series toward the northern

part of the Fairfield quadrangle. Inasmuch as they

are megascopically indistinguishable from the latites

that lack crystallized orthoclase, their occurrence may

be more widespread than this statement would imply;

but the only specimens recognized to be latites by the

microscope alone were aU obtained north of the latitude of Water Fork of Rose Canyon. These rocks are

also light gray and characterized by phenocrysts of

biotite, hornblende, and plagioclase in a dense groundmass. Only under the microscope is the presence of

considerable orthoclase made apparent. This is reflected in the common development of microgranular

texture in the groundmass, although some specimens

with felted texture also carry considerable orthoclase.

No potash feldspars were observed as phenocrysts.

Like the latites without orthoclase crystals, some of

these specimens carry strongly pleochroic hypersthene,

subordinate to augite, and no basaltic hornblende.

Most of the orthoclase-bearing latites, however, can

be classed as biotite-hornblende latites, very like the

dominant biotite-hornblende latites whose orthoclase

failed to crystallize.

A partial analysis of one of the hypersthene-bearing

specimens shows its close similarity to the latites that

are without recognizable orthoclase, as-well as to the

average latite according to Daly's compilation.

Parlial analyses of hypersthene-augite latite (with individualized orthoclase), augite-biotite-hornblende lalite (without individualized orthoclase), and average latite

2 3

61. 09[1

4. 70

3.00 I 3. 77

SiO

z

_

CaO _

NazO _

KzO _

59. 86

4. 62

3.31

4. 84

57.65

05.74

3. 59

4.39

1. Hypersthene-augite latite from 6,589-foot hill in the

southwest corner of sec. 8, T. 4 S., R. 2 W., Fairfield quadrangle.

J. G. Fairchild, analyst.

2. Augite-biotite-hornblende latite from Oak Spring Canyon,

Fairfield quadrangle. J. G. Fairchild, analyst.

3. Average latite. Daly, R. A., Igneous rocks and their origin, p. 23, New York, 1914.

Distribution arna structural relations.-Quartz latite

occurs in the lower part of the flow series in the Tickville Gulch area, lying directly on the quartzite of the

Oquirrh formation about a mile west of the forks of

Tickville Gulch. It also occurs near Tickville Spring,

on the south slopes of South Mountain (Fairfield

quadrangle), and just west of Butterfield Canyon, at

the north edge of the Fairfield quadrangle. Inasmuch

as quartz is rarely a very conspicuous mineral megascopically, and as except for its presence the rocks are

practically identical with the latites just described,

the quartz latite may be much more widespread than

the foregoing statements indicate. Its similarities to

the non quartz-bearing latites are so great that no attempt was made to distinguish the two varieties of

lava in mapping.

Lithology.-The quartz latite strongly resembles the

latites, into which, indeed, it grades. The rocks are

light gray to medium gray in color, weathering to still

lighter gray, cream, yellow, and brown hues. Commonly phenocrysts of biotite, hornblende, plagioclase,

and a very few of quartz are recognizable megascopically. The phenocrysts reach 3 or 4 millimeters in
maximum diameter but are commonly much smaller,

about 1 millimeter. The groundmass is aphanitic.

In thin section the plagioclase is seen to occur in

broken and partly resorbed phenocrysts, which are

twinned according to both albite and carlsbad laws

and have a composition near Ab7oAnsoor slightly more

sodic. The biotite strongly resembles that of the latite,

but there is no augite in the quartz latite studied. The

hornblende of the quartz latite is less basaltic than

that of the latites, is pleochroic in greens rather than

brown, and has extinction angles of 14°. Quartz

occurs as broken and partly resorbed phenocrysts.

Commonly the texture is hyalopilitic, but in some

specimens it is microgranitic, with individualized orthoclase and quartz developed in the groundmass.

A partial analysis of a typical specimen of this rock

reveals the fact that, although there is a lack of

crystallized or at least identifiable orthoclase, the rock

is to be classed with the quartz latites rather than with

the dacites, as is shown by the preponderance of K20

over Na20. Despite the fact that some of the K20

enters into modal biotite, there is no question that a

great deal of it must be available for potash feldspar,

far more than should be present in even a micaceous

dacite.

Partial analyses of quartz latite and of average dacite and

average mica andesite

Si02;

l!:i\6:::::::::::::::::::::::::-:j

65. 64

3.26

3.26

3. 50

66.91

3.27

4.13

2.50

62.25

4. 05

3. 55

2.44

1. Quartlllatite from northwest corner sec. 2, T. 5 S., R. 2 W.,

Fairfield quadrangle. J. G. Fairchild, analyst.

2. Average dacite. Daly, R. A., Igneous rocks and their

origin, p. 215, New York, 1914.

3. Average mica andesite. Daly, R. A., op. cit., p. 26.

A few specimens of quartz latite carry a little hypersthene, but it is nowhere the dominant mafic

mineral.

Some quartz latites are recognizable as such by the

microscope alone, as well-individualized orthoclase is

prominent in them. Such rocks occur near Tickville

Spring.

These quartz latites are light-gray porphyritic rocks

carrying phenocrysts of quartz, plagioclase, biotite,

and hornblende in a very fine-grained groundmass.

Fluidal structure is common. The phenocrysts rarely

exceed 2 millimeters in length. Under the microscope

the plagioclase phenocrysts are seen to be practically

all andesine, with zones· ranging from Ab55An45 to

Ab7oAnso. The quartz phenocrysts are all rounded

and much embayed. The biotite and hornblende are

very like the biotite and hornblende of the latites, but

commonly show more alteration to iron oxide and

chlorite. No augite was seen in any of the slides.

Apatite and magnetite occur as accessories. Orthoclase is confined to the groundmass, of which it seems

to constitute about 50 per cent. The texture of the

groundmass, reflecting this high potassa content, is

microgranitic.

A partial analysis of a typical specimen of this orthoclase-bearing quartz latite shows a slightly less potassic composition than might be considered typical

of latite, yet the potassa predominates over soda, and

the rock can clearly not be classed as a dacite. Both

alkalies and the silica content are lower than the

average liparite (rhyolite).

Partial analyses of quartz latite from Tickville Spring and of

average latite, average dacite, and average liparite

Si0

2

_

CaO _

Na20 --

K20 -.- -- __-- --

57.65

a5.74

3.59

4. 39

66.91

3.27

4.13

2. 50

72. 60

1. 32

3.54

4. 03

1. Partial analysis of quartz latite from Tickville Spring,

Fairfield quadrangle. J. G. Fairchild, analyst.

2. Average latite. Daly, R. A., Igneous rocks and their

origin, p. 23, New York, 1914.

3. Average dacite. Daly, R. A., op. cit., p. 25.

4. Average liparite (including 40 rhyolites). Daly, R. A.,

op. cit., p. 19.

Distribution arnd st'l'U(;tural relations.-A few small

outcrops of greenish obsidian occur in both sides of

Tickville Gulch, in sec. 35, T. 4 S., R. 2 W., and sec.

2, T. 5 S., R. 2 W. These exposures show the obsidian

lying directly on the quartzite of the Oquirrh formation and overlain by latite flows and breccias.

Lithology.-The obsidian occurs mainly in flows

and subordinately in breccias with volcanic ash. The

rock is a light-greenish translucent glass with marked

fluidal structure and perlitic fracture. Phenocrysts

of plagioclase as much as 2 millimeters long are very

numerous. No other minerals are identifiable megascopically. In thin section the plagioclase is seen to

be close to Ab70Anso in composition. Minute flakes

of biotite, very small granules which are probably

augite, and a few crystals of zircon are the only other

minerals seen. The glass is perlitic and has a refractive index of about 1.503. The rock was classed microscopically as an andesitic obsidian, but a partial chemical analysis reveals the surprising fact that despite

the prominence of the plagioclase phenocrysts, the

rock has the chemical composition of a typical rhyolite-in fact, it has even lower soda and lime and

higher potassa than the average.
Partial ana yses of obsidian from Tickville Gulch and of average

liparite and average dacite

8io

2

_

CaO _

~a20 _

K

2

0 _

66.91

3.27

4.13

2.50

72.11

.71

2.53

4.78

72.60

1. 32

3.54

4.03

1. Rhyolitic obsidian from ~E. X sec. 2, T. 5. S., R. 2 W.,

Fairfield quadrangle. J. G. Fairchild, analyst.

2. Average liparite (including 40 rhyolites). Daly, R. A.,

Igneous rocks and their origin, p. 19, ~ew York, 1914.

3. Average dacite. Daly, R. A., op. cit., p. 25.

Field oCCUQ"1'ence.-Onlyone body of nephelite basalt

lava was found in the Fairfield quadrangle. This

occupies an area of a few acres in the NE. % sec. 31,

T. 4 S., R. 2 W., capping a small knoll on the east flank

of Sheep Ridge. At the north the nephelite basalt

overlies latite breccia, but at the south end 0'£ the small

outcrop it overlaps the breccia onto the quartzite of

the Oquirrh formation. .

LithoZogy.-The nephelite basalt is a very heavy

lOck, of dark-brown to almost black color. It is porphyritic, with phenocrysts of brown mica about 2 or

o millimeters in diameter and of olivine about 1 millinJeter in diameter set in a dense groundmass.

Under the microscope the dominant phenocrysts are

seen to be olivine and a pale variety of biotite in about

equal amounts, together making up about 20 per cent

of the rock. The olivine crystals are euhedral, ranging from about 1 millimeter down to about 0.2 millimeter in length in seriate porphyritic fashion. The

olivine is optically positive, with large axial angle and

birefringence abaut 0.034. The biotite is a beautifully

pleochroic variety, with X very pale yellow and Y =Z

light rosy brown, with a striking golden luster. It is

twinned on the face 001 and sho,wsinclined extinction

of 4°. Its birefringence is about 0.035. The biotite

crystals are anhedral and poikilitically inclose great

numbers of subhedral augite crystals, most of which

are very small-less than 0.05 millimeter long and

grading down to the limits of the microscope. Some

of the augite crystals, however, attain lengths 0'£ 0.3

millimeter. They are colorless, nonpleochroic, with extinction angles of 40° and birefringence of about 0.025.

Probably 35 or 40 per cent of the rock is composed of

augite. NO!feldspar occurs in the rock, the groundmass being composed of a mat of nephelite and augite

crystals nearly all less than 0.05 millimeter long. The

lephelite has the characteristic short, stumpy prisms

of hexagonal cross section where cut at right angles to

the axis and rectangular section parallel to the axis.

It has indexes equal to or slightly higher than that of

canada balsam, negative elongation, parallel extinction, and very low birefringence, so that the determination as nephelite is assured.

Distribution and structwral relations.-A small remllant of a flow of olivine basalt occurs on the south

side of West Canyon just below the mouth of Iron

Canyon. Except for a few fragments in the latitic

breccia, this is the only feldspar basalt in the Stockton

and Fairfield quadrangles. It is not in contact with

any other volcanic rock, but its topographic situation

suggests that it may possibly be the youngest volcanic

rock of the area. However, it is perhaps equally possible that its position is accounted for by the exhumation of a prevolcanic valley and that the flow is older

than the bulk of the extrusives.

Lithology.-The rock composing the West Canyon

flow is a dark greenish-gray amygdaloid. The only

minerals recognizable in hand specimens are olivine

and feldspar. The amygdules are filled with opal and

zeolites.

In thin section the rock is seen to contain microphenocrysts of olivine as much as 1 millimeter long

and of augite as much as 1.5 millimeter long, commonly in aggregates resembling phenocrysts. The

augite is less than 0.1 millimeter in minimum grain

size. It has a pale-green color, a birefringence of

about 0.025, and an extinction angle of about 45°

and is optically positive. The olivine is in rounded

to subhedral grains showing the characteristic

rough cleavage and alteration to light-greenish serpentine. Plagioclase occurs in laths as much as 0.4

millimeter long. It has a composition close to

Ab6oAn5o. Magnetite is a conspicuous accessory, and

apatite is also present. A small amount of glass occurs in the base, and the texture of the groundmass,

though chiefly intersertal, varies locally to pilotaxitic.

The zeolites in the amygdules are chiefly phillipsite,

with n less than 1.51 and greater than 1.50, low birefringence, and extinction angles of 32°. The esti..

mated mineral composition of the rock is as follows:

Per cent

Plagioclase 08

Augite_____________________________________ 25

Olivine 8

Serpentine_________________________________ 5

~agnetite__________________________________ 3

Apa Ute -__________ 1

The intrusive rocks of the Stockton and Fairfield

quadrangles, including granular rocks and porphyries,

are prevailingly monzonitic but range from diorite

through monzonite to granodiorite and quartz monzonite and their corresponding porphyries. However,

rhyolite and andesite (or latite) are present, and a
few small bodies of nephelite basalt and lamprophyre

are likewise found.

The monzonite and related rocks have a considerable

range in composition, but despite the variations the

rocks appear to be very closely related genetically and

are conveniently grouped together, although the local

variations are sufficient to justify separate descriptions of the larger bodies. For this reason, these rocks

will be discussed in groups according to their geographic distribution.

The intrusive rocks on Porphyry Knob and Lion

Hill were given the miner's name "Bird's-eye" porphyry by Spurr.2S These localities are in the northern portion of the Mercur mining area.

Distribution and struotwral relations.-The occurrences of the" Bird's-eye" porphyry of Spurr are isolated from the other intrusions of closely comparable

character and are grouped in the vicinity of Porphyry

Knob and Lion Hill. Fourteen separate masses were

mapped, all of which have general sill-like relations

although they may be more irregular in detail; but

exposures at and near the contacts are too poor or too

few to permit detailed mapping.

Where well exposed (as on Porphyry Knob and on

the larger mass west of Porphyry Hill) the intrusive

rocks exhibit two prominent sets of joint planes which

intersect in a direction roughly normal to the stratification of the inclosing limestones. Locally one set

is better developed than the other, giving rise to a

slabby or sheeted appearance. Where the sets are

about equally developed a rude columar structure becomes evident.

A number of small faults cut the sill of Porphyry

Knob, but they are of slight displacement and have

no apparent control of the distribution of the igneous

rock.

The thickest sill, that outcropping on the west slope

of Porphyry Hill, is over 400 feet thick, but none of

the other sills of "Bird's-eye" porphyry exceed a few

tens of feet. The sills on Lion Hill appear to have

exercised some control of the ore deposition, for the

jasperoid that carries the ore seems to lie immediately

beneath one of the sills. The writer concurs in the

opinion of Butler 29 that this sill, as well as all the

others on Lion Hill, is to be referred to the "Bird'seye" (monzonite) porphyry rather than to the Eagle

III Spurr, J. E., Economic geology of the Mercur mining district,

Utah: U. S. Geol. Surve.y Sixteenth Ann. Rept., pt. 2, pp. 379-380,

1895.

••Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof.

Paper 111, p. 381, 1920.

Hill rhyolite, as was suggested by Spurr. so Two sills

of this rock, each only a few feet thick, are cut by the

Buffalo tunnel, on the east flank of Lion Hill, but here .

there is no apparent relation between the igneous rock

and the ore bodies.

Lithology.-The "Bird's-eye" porphyry is very

poorly exposed, and its exposures are very much altered, either by weathering, as in most outcrops, or by

the action of hydrothermal solutions related to ore

deposition, as in most of the exposures on Lion Hill.

For this reason it is difficult to obtain satisfactory

material for study.

The freshest material seen is a medium-gray porphyritic rock with numerous phenocrysts of feldspar,

biotite, hornblende, and quartz in a greenish-gray

groundmass of which the constituent minerals are unrecognizable. Where more decidedly weathered the

rock has a lighter cast, the feldspar crystals contrast

less strongly with the groundmass, and the biotite assumes a bronzelike luster. Hydrothermal alteration

has resulted in a very light-gray rock with dull-white

feldspar, only faint buff pseudomorphs after biotite,

and a pyrite-bearing groundmass of light-gray hue.

The feldspar phenocrysts jn the rock all appear to

be plagioclase. They range from about 1 millimeter

to about 6 millimeters in size. The biotite occurs in

barrel-like hexagonal tablets which reach about 3 millimeters in length. Hornblende is less conspicuous,

although a few crystals with typical amphibole cleavage and greenish-black color are recognizable. They

are chiefly less than 2 millimeters long. Quartz is not

a conspicuous mineral among the phenocrysts, but occurs in rounded grains 2 or 3 millimeters in maximum

diameter.

Under the microscope the rock is seen to be seriate

porphyritic with respect to the feldspar crystals, which

range from 6 millimeters in length down to less than

0.1 millimeter, without sharp discontinuity in size

I'ange. The larger feldspar phenocrysts appear to be

well-formed, equant, and somewhat zoned and show

both carlsbad and albite twinning. Their composition

is close to Ab6oAn4o. The smaller crystals are slightly

more sodic, about Ab65Ans5•

The quartz phenocrysts are much resorbed and exhibit no crystal faces. They are considerably fractured

and show deep embayments of groundmass. Orthocla-sephenocrysts are subordinate, although a few wellformed crystals as much as 1 millimeter in diameter

occur. Bio,tite is largely altered to chlorite, but some

still remains unaltered. It originally formed crystals

of clear-cut outlines as much as 3 millimeters long.

Apatit~ is conspicuous, some crystals approximating

1 millimeter in diameter. No hornblende occurs in the

two slides of this rock that were studied, but without
question it is sparingly present. Pyrite and probably

magnetite also occur in small amounts.

The groundmass of the specimens studied is much

clouded with alteration products but is evidently composed chiefly of quartz and orthoclase in microgranitic

arrangement. The grain size of the constituent minerals averages perhaps 0.05 millimeter. Among the

phenocrysts the plagioclase predominates over orthoclase in about the ratio of 10 to 1. This proportion is

reversed in the groundmass.

OlasllifWation.-The rock is completely crystalline

and porphyritic, with total plagioclase predominating I

over total orthoclase in a ratio somewhat greater than

2 to 1. As quartz is an essential constituent, the rock

falls into the class of granodiorite porphyries. The

" Bird's-eye" porphyry is the only granodioritic rock

found in the Stockton-Fairfield area, but its relation to

the more potassic monzonites farther north is doubtless

very close.

Distribution and structural relationB.-The largest

intrusive mass within the Stockton and Fairfield quadrangles crops out high on the north wall of Soldier

Canyon in secs. 28 and 27, T. 4 S., R. 4 W. This body

is a stocklike mass approaching quartz monzonite in

composition. Its contacts are crosscutting, despite the

fact that its major axis lies roughly parallel to the

strike of the country rock and apparently reflects a

notable amount of control of the intrusion channel by

the preexisting structure. Toward the south and east

of this stock are a number of dioritic and monzonitic

sills, evidently closely related to it and extending for

about 3 miles along the strike. Most of these sills are

of slight thickness, and the largest is only about 30

feet thick. In addition to these dioritic and monzonitic sills there are a few thin sills of andesite and

one of dacite in this area. They are mapped with the

monzonite sills. All these bodies except the large mass

first mentioned are accordant with the structure of

the sedimentary rocks in which they lie but show local

minor discordances.

Lithology and classifioation of quartz monzonite

.~tock.-The dominant variety of the rock composing

the Soldier Canyon stock is a medium-gray equigranular millimeter-grained rock which contains quartz,

plagioclase, orthoclase, biotite, and pyroxene recognizable in the hand specimen. There is a slight tendency for aggregates of pyroxene crystals to form

pseudophenocrysts, but otherwise the rock possesses

no unusual features.

Locally along the border of the mass the rock is

decidedly more coarse grained and feldspathic than it

is in the middle. The quartz, orthoclase, and plagioclase form a light-gray rock speckled with bright-green

pyroxene crystals 2 to 3 millimeters in length. Pyrite

is also present in veinlets through this rock. Elsewhere the stock possesses no unusual mineral development at the border.

In thin section the normal facies of the rock exhibits

granitic texture. Plagioclase occurs in fairly wellformed crystals which range in size from 0.1 to 2

millimeters and average between 0.3 and 0.5 millimeter.

There is very little zonal development, and the composition is about Ab1oAnso(oligoclase-andesine). Microcline, one of the last minerals to crystallize, is

largely anhedral, but a few of its crystals are rather

well formed and are nearly 1millimeter long. Plagioclase and orthoclase occur in about equal amounts and

together constitute about two-thirds of the whole rock.

Quartz, which makes up about 15 per cent of the rock,

is anhedral, like the orthoclase.

The most prominent mafic mineral is light-green

diopside, which occurs in well-formed crystals about

1.millimeter in greatest length. It is accompanied

and in part replaced by biotite and to a less extent by

magnetite. A small amount of light-green pleochroic

uralitic hornblende is also developed. Biotite occurs

along cracks and borders of the diopside and in independent euhedral plates which reach 1.5 millimeters

in diameter. In part it is replaced by magnetite

through magmatic reactions. Original magnetite, apatite, and titanite are minor accessory minerals.

The coarser border facies differs from the normal

rock in having its plagioclase subordinate to the microcline in about the ratio of 2 to 5. The pyroxene also

shows somewhat more alteration to uralitic hornblende

than that in the normal rock. No biotite is present in

this variety. Small nodules and angular fragments

of calcite, which probably represent r.esidual xenoliths

of country rock, are present. There is a suggestion,

which may readily be exaggerated, that the diopside

is more plentiful in the neighborhood of such inclusions, an expectable association but one which it would

be difficult to establish in the specimens studied. The

rock is very fresh, and the calcite can not be attributed

to weathering.

The texture of this rock is not a simple granitic one

but possesses analogies to the "sieve structure" of

Grubenmann,sl in which the several minerals inclose

one another. This texture he attributes to sudden

crystallization of a supersaturated solution. It is possible that rapid growth of crystals leading to mutual

inclosures might be induced by subsequent" seeding"

of a slightly supersaturated magma solution-a seeding which might occur through the picking up of

xenoliths. The consequent rapid consolidation may

be the cause of the lack of biotite as a reaction product

of the diopside.

81 Grubenmann, D., and Niggll, P., Die Gesteinsmetamorphose, p. 420,

Berlin, 1924.
The principal facies of the Soldier Canyon stock,

containing plagioclase and microcline in essentially

equal amounts and plentiful quartz, is a normal quartz

monzonite. The border facies studied, with its microcline-plagioclase ratio of about 5 to 2, would be classified by Johannsen as a quartz syenomonzonite, but

most writers would class it as a granite. It is quantitatively unimportant.

Lithology and elasBifWation of sills.-The sills that

crop out on the north wall of Soldier Canyon are obviously closely related to the stock, though varying

considerably among themselves. They are all shown

on the geologic map as "quartz monzonites and related rocks," but, as will be seen from the descriptions

below, they range from quartz monzonite porphyry to

diorite.

The sills, which roughly parallel the southern contact of the stock, at a distance of a few score feet, are

coarsely porphyritic rocks. The prominent phenocrysts are plagioclase and sanidine, reaching 1 centimeter in length and averaging well over 5 millimeters.

They are accompanied by much smaller quartz phenocrysts, few of which exceed 2 millimeters in diameter,

and small biotite crystals and are set in a dense

groundmass. The rock is much altered and staiIwd

brown through weathering. Under tlie microscope

the only minerals identifiable are oligoclase-andesine,

of about the composition Ab7oAnao,sanidine, quartz,

biotite largely altered to chlorite, apatite, and magnetite. The oligoclase occurs in well-formed but highly

weathered and cloudy phenocrysts about 2 millimeters

in length. The sanidine is almost uniaxial, with extinction angle 90 between a and 001. The phenocrysts

range from 1 centimeter to 1 millimeter and average

about 4 millimeters. The quartz occurs in much resorbed crystals about 2 millimeters in maximum diameter. The biotite is almost all altered to a nearly

colorless chlorite and iron rust. Apatite and magnetite are accessories. The phenocrysts altogether constitute about 40 per cent of the rock and include

roughly equal amounts of plagioclase and sanidine

with much less quartz and biotite. They are set in a

microgranitic groundmass which is much clouded with

weathering products. These characteristics permit

the classification of the rock only as a quartz monzonite porphyry. Rocks resembling it very closely

are common in the Stockton mining area.

Several of the Soldier Canyon sills can be described as diorite porphyry. These rocks are medium

to dark gray and more or less altered. They contain

recognizable phenocrysts of hornblende and plagioclase and, in some specimens, of biotite and epidote in

a dense groundmass. The microscope shows them to

consist of much altered plagioclase phenocrysts which

reach 2.5 millimeters in length, hornblende, and a

very little quartz, with apatite and magnetite as minor

accessories. The plagioclase is sodic andesine, with a

composition of about Ab6sAna5. Some specimens carry

a small amount of augite as phenocrysts which show

alteration in hornblende; others carry no pyroxene but

considerable epidote of the variety pistacite. The epidote is probably to be referred to hydrothermal alteration related to ore deposition. Orthoclase is subordinate and is confined to the groundmass. The groundmass makes up more thim half of the rocks examined

and is much altered to a mass of calcite, clay minerals,

and quartz. The texture is seriate porphyritic with

microcrystalline groundmass, and the rocks are to be

classed as diorite porphyries.

Fine equigranular medium-gray rocks which are referred to diorite also occur as sills, both closely associated with the Soldier Canyon stock and half a mile or

so to the southwest of it. These rocks carry megascopically recognizable biotite, amphibole, and plagioclase. Under the microscope the rocks are seen to be

fine grained, of granitic texture, with predominant

plagioclase in crystals about 0.1 to 0.3 millimeter long,

biotite, hornblende (or, in some rocks, uralitic amphibole), and subordinate orthoclase with a small amount

of interstitial quartz and accessory apatite and magnetite. The rocks are altered both by magmatic reactions, leading to the breaking up' of the mafic minerals

to yield magnetite, and by weathering, which has produced a very cloudy appearance in the feldspar and

considerable halloysite and presumably other clay minerals. The plagioclase is strongly zoned, the center of

some crystals being about Ab45Anss,whereas the border

is close to AbsoAn2o. The average composition is

doubtless not far from Ab7oAnao. The rocks are to be

classed as fine-grained biotite-hornblende diorites.

One sill of quartz diorite porphyry was found low

on the north wall of Soldier Canyon in sec. 33, T. 4 S.,

R. 4 W. This rock resembles the diorite last described

except for the presence of very large phenocrysts of

biotite and feldspar, which reach 5 millimeters or even

1 centimeter in length, in a groundmass resemQling the

equigranular diorite just described. Quartz is more

prominent than in the nonporphyritic rock, and the

specimens available to study are much more weathered

r.nd calcitized; otherwise the rock is very like the equigranular diorite.

High on the wall of Soldier Canyon in the southern

part of secs. 26 and 27, T. 4 S., R. 4 W., is a sill which

is composed of porphyritic medium-gray rock carrying conspicuous phenocrysts of plagioclase, biotite,

and pyroxene in a fine-grained groundmass. The

plagioclase crystals reach 6 millimeters in length, the

biotite 3 or 4 millimeters, and the pyroxenes about 2

millimeters. The microscope reveals a seriate porphyritic, completely crystalline rock. Plagioclase (zoned,
Aba5An35to Ab75An25,the more sodic zones toward the

exterior) occurs in well-formed crystals that range

from less than 0.1 millimeter to 6 millimeters in size.

It makes up nearly 40 per cent of the rock. Orthoclase, though occurring in smaller crystals and largely

as anhedral interstitial grains, is fully as abundant.

The pyroxene is common augite of a light-green hue,

nonpleochroic, and reaching 2 millimeters in size but

averaging perhaps 0.2 millimeter. It is partly altered

to biotite, which is also independently developed.

The biotite has normal pleochroism and where it is

clearly a reaction product of pyroxene is accompanied

by conspicuous magnetite. There is a small amount

of common hornblende, pleochroic in green and greenish brown (Z= Y> X) and with extinction angle of

25°. Apatite and magnetite are conspicuous accessories. The quartz is all interstitial and can hardly

exceed 5 per cent of the total rock. The groundmass

is of granitic texture, with an average grain of about

0.05 millimeter. The rock is best described as a monzonite porphyry.

In the SW. 1,4 sec. 36, T. 4 S., R. 4 W., is a sill of

biotite dacite which can be traced for a few hundred

feet. It is strictly accordant with the structure of the

inclosing rocks, as far as can be judged from the discontinuous exposures. Its thickness hardly exceeds

20 feet. The microscope reveals a rock of trachytic

texture consisting of sparse phenocrysts of feldspar,

biotite, and quartz set in a groundmass composed almost wholly of feldspar laths. These feldspar laths

are very small, mostly less than 0.1 millimeter long,

and from their indexes are presumably calcic oligoclase, about Ab75An25. A very little orthoclase, a

considerable amount of quartz, and some minute biotite flakes also occur in the groundmass. Zircon and

apatite are accessory. Considerable alteration has occurred and the rock studied has been impregnated

with a good deal of calcite. The mineral composition

and texture of this rock are such as to classify it as

a biotite dacite. It does not closely resemble any of

the other rocks of the area, but there is no reason to

doubt that it is a derivative of the magma whose dominant representatives are dioritic and monzonitic

rocks.

The longest sill exposed in Soldier Canyon is composed of andesitic rock. It can be followed from a

point near the center of sec. 35, T. 4 S., R. 4 W., in a

west-northwesterly direction nearly to the middle of

the south line of section 28. The sill is about 20 feet

in average thickness and conforms to the structure of

the country rock as far as the relations are revealed by

the rather poor exposures.

The rock composing this sill is a light-gray porphyry. The only minerals identifiable in the hand

specimen are hornblende and feldspar, both much

altered. A trachytic texture is apparent. In thin

section the feldspar is seen to be chiefly in small laths

with a composition near AbaoAn4o, Hornblende and

possibly biotite are represented by iron-stained pseudomorphs of calcite, and the feldspathic constituents

are likewise much altered to calcite and cloudy aggregates of clay mineral. The rock is an andesite, doubtless related to the diorites and monzonites of the

neighboring sills.

Distribution and structural relations.-In and near

the mining area of Stockton there are many dikes,

sills, and small stocks, chiefly of quartz monzonite

porphyry, with some closely related rocks, such as

diorite porphyry. In the southern part of this district,

in sees. 29 and 30 and the southern part of sec. 20, T.

4. S., R. 4 'V., most of these igneous bodies are in the

form of small, irregular transgressive stocks, although

a few dikes occur. Farther north, in sections 17,18,19,

and 20, the intrusive rocks occur chiefly as northwardtrending, westward-dipping dikes, although a few sills

were seen in the workings of the Honerine mine.

The parallelism of these dikes to numerous faults

in this area suggests strongly that most of them have

been intruded along preexisting fault fractures. Con8iderable brecciation of wall rock along one or two

of the dikes strengthens this suggestion, although the

brecciation may have been due to the forcible intrusion

of the dikes instead of to earlier faulting. Although a

certain amount of postporphyry faulting has occurred

in this area, there is no likelihood that the brecciation

can be attributed to this late period.

The largest intrusive mass near Stockton is the

stocklike body known locally as the "Raddatz" porphyry, because it was first cut by mine workings under

the supervision of Mr. Raddatz. This mass is very

inconspicuous at the surface, near the Honerine air

shaft, but widens considerably in depth and where cut

on the 1,200-foot level of the Honerine mine is 300

feet wide. This and the other stocklike masses farther south are in contrast with the narrower dikes

in having notable contact zones about them, whereas

the metamorphosing effects of the smaller bodies on

the country rock are much less pr.onounced. The

metamorphosing effects of the intrusions are discussed

in detail in a later section of this report.

North of Selkirk Canyon, not far outside the mineralized area of Stockton, are two sills which resemble, in general, the intrusive rocks of the Stockton area

and can be conveniently discussed at this point. These

sills are rather conspicuous. The eastern one is only

a few feet thick but is traceable for well over a mile,

and the western one is about 100 feet thick and forms

a prominent light-gray band across the mountain
spurs just above the alluvium. Both conform closely

to the bedding of the country rock.

Lithology of the qoortz monzonite.-The commonest

intrusive rock of the Stockton area is quartz monzonite porphyry. Several variants of the rock occur,

distinguished chiefly by their grain size. Of these

variants the most abundant, which closely resembles

the first-described group of sills associated with the

Soldier Canyon stock, is a medium-gray porphyry that

carries very conspicuous pink orthoclase, less prominent quartz, plagioclase, biotite, and hornblende as

phenocrysts in a dense groundmass. The orthoclase

phenocrysts range from 5 mirlimeters to 1 centimeter

in average length. Plagioclase occurs in lathlike

crystals, rarely exceeding 3 millimeters in length. The

quartz phenocrysts are rounded, do not exhibit crystal

faces, and rarely exceed 2 millimeters in diameter.

The biotite plates are about 1 millimeter long, and the

hornblende of about the same size. Many of the

specimens show mottling of the feldspars by epidote.

In thin section the rock is seen to consist of about 50

per cent phenocrysts and 50 per cent microgranitic

groundmass, with an average grain of about 0.05

millimeter in the better-crystallized specimens and

somewhat smaller in the less well crystallized. The

orthoclase phenocrysts are commonly twinned according to the carlsbad law and are euhedral. Plagioclase,

which is about equal in amount to the orthoclase, is

comrg.onlytwinned according to both albite and carlsbad laws. Its composition is that of sodic andesine,

slightly more calcic than Ab7oAnao• A very little

pyroxene, probably augite, occurs in some specimens,

but most of it has been altered to biotite and amphibole. Biotite shows no unusual characters. Hornblende is not present in all the specimens examined but

where present is pleochroic in green and brown, with

extinction angles between 16° and 22°. Epidote is

commonly present in the mineralized areas, probably

as a result of the action of hydrothermal solutions on

the consolidated rocks. It replaces the mafic minerals

and both feldspars. It is chiefly pistacite, although

considerable clinozoisite also occurs. Both hornblende

and biotite, as well as epidote, are altering to chlorite

because of weathering. The quartz phenocrysts are

much resorbed and exhibit rounded outlines and some

fracturing. Apatite, zircon, magnetite, and a little

titanite are common accessories, and the more epidotized specimens also carry pyrite, which is presumably epigenetic. Sericite in small amounts is a

common replacement product of feldspar. Some of

the much-weathered specimens show calcite. In most

of the specimens examined orthoclase predominates

f'lightly over the plagioclase, but nowhere to the extent

that might be expected from the megascopic prominence of the orthoclase.

The commonest variants from the type of rock just

described are distinguished chiefly by the large size of

their orthoclase phenocrysts. The" Raddatz" porphyry and the two sills north of Selkirk Canyon are

especially conspicuous in this respect. The rocks of

these bodies carry orthoclase phenocrysts fully 1.5 centimeters in average length, and many of the crystals

are as much as 3 or 4 centimeters long. Most of these

large phenocrysts are beautifully euhedral. Sharply

bounded simple crystals and carlsbad twins 2 and 3

centimeters in length can be found in profusion on

weathered outcrops. Microscopically these varieties

do not differ notably from the dominant rock except

that they contain few orthoclase crystals intermediate

in size between the large phenocrysts and the groundmass. Thus, although the orthoclase is decidedly

more conspicuous in these rocks than in the common

type, it is probably not more abundant.

Varieties of finer grain than the main type also occur, but beyond the difference in grain size and correspondingly less conspicuous porphyritic texture, they

possess few noteworthy features.

Lithology of m,inor related types.-A few of the intrusive rocks of the Stockton mining area are to be

classified as monzonite porphyry, diorite porphyry,

and quartz diorite porphyry, although they are included on the geologic map with the quartz monzonites under the somewhat elastic phrase "quartz

monzonites and related rocks."

A few bodies of fine-grained monzonite porphyry

crop out near the Calumet mine. They are chiefly

small dikes and irregular pluglike bodies of mediumgray rock. They differ from the common facies of

quartz monzonite porphyry only in their much smaller

grain size, few of the phenocrysts reaching 1 millimeter in length, and in the absence of quartz among

the phenocrysts. Even the groundmass carries very

little quartz, estimated at well under 5 per cent.

In the mines of Stockton dikes of highly altered

dark greenish-gray rock occur. One of these, on the

] ,OOO-footlevel of the Ben Harrison mine just east of

the shaft, carries 1-millimeter phenocrysts of hornblende, plagioclase, quartz, and chloritized biotite in a

dense groundmass. Alteration has been intense, but

the microscope reveals the absence of orthoclase as

phenocrysts and its subordinate importance in the

groundmass. The rock is an altered quartz diorite

porphyry.

Several dikes in the Honerine mine, especially in

the Weir crosscut and the 1650 north crosscut, are dark

greenish-gray porphyry which the microscope shows to

be diorite porphyry. These rocks are characterized by

andesine in phenocrysts 1 millimeter long and in the

microlitic groundmass, uralitic hornblende containing

small pyroxene remnants, common hornblende, chlorit-
ized biotite, serpentine, and small amounts of quartz

and orthoclase, both of which are confined to the

groundmass. Sericite and chlorite are prominent, and

some of the quartz may be due to hydrothermal silicification. The original rocks were without doubt to be

dassed as diorite porphyry.

Distribwtion amdstruotural relations.-Owing to the

cover of vegetation and talus, exposures are very poor

in both Settlement and Middle Canyons, so that there

are probably a number of igneous bodies there which

escaped detection. However, it is probable that any

such bodies are small. An isolated sill occurs on the

north slope of Settlement Canyon just below the mouth

of Dry Fork; a group of small stocks and associated

sills occur in the valley of the east fork of Settlement

Creek and extend over the divide into White Pine

Flat; a small stock crops out in the north wall of

Middle Canyon just below the mouth orf White Pine

FlGURm 7.-Relations of dike and country rock in east fork

of Settlement Canyon, showing deformation of the country

rock, presumably by the force of igneous intrusion

Canyon; and a number of small dikes occur on the extreme edge of the Fairfield quadrangle north of this

stock. Besides these bodies a specimen of andesite was

found on the dump of a caved prospect tunnel a few

hundred yards east of the Middle Canyon portal of the

Utah Metal Co.'s tunnel, but no exposure of the rock

in place could be discovered.

The structural relations of most of these bodies are

sufficiently summarized by their classification as sills,

stocks, and dikes, but the relations of one dike are of

sufficient interest to warrant description as demonstrating the powerful intrusive force of the magma.

This dike is an offshoot of the westernmost stock in

the east fork of Settlement Canyon, and its exposed

part extends upward from the main stock as a crosscutting body some 20 feet wide. The east wall of the

dike is concealed, but the west wall is formed by thinbedded limestone of the Oquirrh formation. Where

these limestones abut against the dike they are bent

from their normal westward dip of about 30° nearly

to the vertical, the displacement of the end of a given

bed amounting to several tens of feet. There is no

suggestion of postigneous faulting, and it is difficult

to escape the impression that very powerful injection

forces have caused the emplacement of the dike. The

relations are illustrated by Figure 7.

Lithology.-The sill exposed northwest of the mouth

of Dry Fork of Settlement Canyon is of quartz monzonite porphyry, so nearly resembling the siNs north of

Selkirk Canyon just described and the" Raddatz"

porphyry of the Honerine mine that it was not studied

microscopically. It contains very large orthoclase phenocrysts with smaller ones of quartz and plagioclase.

The stocks in the east fork of Settlement Canyon

and extending over the divide into White Pine Canyon

are composed of dioritic rock in its various facies,

light, medium, and dark gray. Most specimens are

equigranular, but in places the border facies of the

stocks are porphyritic. Biotite, pyroxene, and plagioclase are recognizable in all specimens, and a few show

quartz in addition.

The more mafic equigranular facies are shown by

the microscope to have granitic texture, with the

grain size of the plagioclase averaging about 0.5 millimeter and that of the mafic minerals somewhat larger.

The principal constituent is plagioclase, which makes

up about 50 per cent of the rock. It occurs in

ragged-ended laths, twinned according to both carlsbad and albite laws. Its composition is close to

AbooAn4o (andesine). Orthoclase is subordinate, not

exceeding 10 per cent of the rock, and is chiefly interstitial, although in sporadic euhedral crystals. Pyroxene makes up more than 20 per cent of the rock and

occurs in aggregates forming pseudo phenocrysts and

as isolated euhedral crystals. It is a light-green, nonpleochroic augite, with some zoning. It shows alteration by magmatic reactions in two ways-to amphibole, pleochroic in green and brown, and more commonly to biotite. The alteration to biotite is controlled by the cleavage of the augite to a slight extent,

but more ofthe biotite appears to be developed parallel

to a steep end face of the host mineral. Biotite also

occurs in well-individualized plates as much as 2 millimeters long. Apatite, titanite, and magnetite are

accessories. One of the striking features of the rock

is the presence of narrow veins of zeolites, chiefly analcite and thomsonite, which cut through the rock. The

zeolites also replace the plagioclase feldspar to a notable extent. This facies of the rock is to be classed as

a biotite-augite diorite.

The more felsic equigranular facies of the rock is

somewhat finer grained and is composed of the same

minerals as the mafic facies, except that it contains

only about 20 per cent of dark minerals, the difference

being made up by quartz and analcite. The texture
of the rock is also decidedly different from that of the

mafic facies. The feldspar laths are disposed in a

divergent mesh suggesting the texture of a lamprophyre, but the mafic minerals are far less abundant

and less well crystallized than they should be for a

true lamprophyric rock. Magmatic reactions have decidedly frayed the augite crystals, and there has been

more development of uralitic hornblende than of biotite after augite, although biotite does occur in this

manner. The small amount of biotite independent of

augite is less well formed than in the mafic rock.

There is a more striking association of magnetite with

the dark minerals than in the darker facies. The plagioclase is more calcic in this facies, being about

Ab5oAn5o. Quartz is chiefly interstitial but occurs also

in grains as much as 0.2 millimeter in diameter. Zeolitization of the feldspar has been intense. The chief

zeolite present is analcite. The rock is analcitized

quartz-augite diorite.

A third variant of the Settlement Canyon stocks is

the porphyritic contact rock mentioned above. This

rock exhibits phenocrysts of hornblende as much as 1

centimeter long and of biotite about 2 millimeters long,

set in a medium-gray groundmass in which plagioclase

is the only megascopically identifiable mineral. Under the microscope the phenocrysts are seen to be

hornblende, pyroxene, and biotite. The hornblende is

pleochroic in green and dark brown (Z=Y>X). It

is optically negative, with an extinction angle of 25°.

It is corroded about the borders, with the development

of a nearly continuous inner zone of magnetite and an

outer rim of biotite about each crystal. Augite is also

developed in these zones. Some of the augite is in a

few poorly formed phenocrysts as much as 1 millimeter long which show a tendency to occur in aggregates, but most of it occurs as granules through the

groundmass. Biotite phenocrysts as much as 2 millimeters long occur in addition to the reaction rims

.around the hornblende and a few small wisps developed in association with the augite. Plagioclase,

with composition close to Ab5oAn5o,occurs in laths

.and tables as much as 1 millimeter long but mostly

less, and considerable plagioclase occurs as granules

interstitial to the other minerals. Orthoclase is a very

subordinate mineral, not exceeding 10 per cent of the

rock. It is wholly interstitial. A little quartz may be

present. with the orthoclase. Magnetite and apatite

are accessories. The texture of the rock is very unusual. Areas of coarser crystallized plagioclase and

mafic minerals are set in a fine-textured groundmass

composed of granules of plagioclase, augite, biotite,

,orthoclase, and possibly quartz. There are " log-jam"

arrangements of plagioclase laths around the larger

mafic phenocrysts, and the groundmass shows in places

:a micropoikilitic texture.

A short distance south of the stock that crops out

east of the main divide of the mountains, between

White Pine Flat and Settlement Canyon, are a few

thin sills. Most of these are much weathered, brownstained fine-grained rocks. Under the microscope the

rock is seen to be a highly analcitized andesite, containing biotite plates and plagioclase laths (Ab65Ans5)

showing flow structure, in a fine-grained, felted

groundmass which may contain a little orthoclase.

Analcite has replaced much of the feldspar. A sill of

similar rock occurs in the north flank of the 9,245-foot

peak just north of this stock, but it was not examined

microscopically.

The stock cropping out on the north wall of Middle

Canyon just below White Pine Canyon is composed of

a handsome medium-gray porphyry. The phenocrysts include orthoclase, plagioclase, biotite, and hornblende, of which all but the orthoclase are only

slightly more than 1 millimeter long. The orthoclase

crystals, however, reach or even exceed 1 centimeter in

length. The .microscope shows the pragioclase to be a

calcic oligoclase, about Ab15An25,twinned according to

both carlsbad and albite laws. It makes up about a

third of the rock, mostly as phenocrysts. Orthoclase,

despite the greater size of its crystals, is not so abundant among the phenocrysts but makes up nearly or

quite half the entire rock. It forms beautiful carlsbad twins, much resembling those of the Stockton

mining area. Biotite is the most conspicuous dark

mineral but exhibits no noteworthy features beyond

its euhedral character. The rock contains a little palegreen, nonpleochroic augite and a very little hornblende, pleochroic in green and brown. Quartz occurs

in broken phenocrysts 1 millimeter in diameter and

forms about 5 per cent of the groundmass. Apatite,

magnetite and titanite are accessory, and a little calcite,

doubtless due to weathering, completes the list of minerals determined. The texture of the rock is seriate

porphyritic, with respect to the feldspars. The

groundmass textures range from granitic to micrographic, with the former predominant .

Distribution amd structural relations.-There is a

small mass of dioritic rock near the center of sec. 2-6,

T. 4 S., R. 2 W.; in a tributary to Tickville Gulch. It

is indicated on the geologic maps as about 500 feet

north of the plug of Tickville rhyolite breccia. The

mass is a small plug, only about 100 to 150 feet wide,

intruding the Oquirrh formation and a quartz latite

flow belonging to the volcanic series of the Traverse

Mountains. This fact is of considerable interest, because this locality is the only place in the Stockton

and Fairfield quadrangles where volcanic and coarse

intrusive rocks are in contact and shows that this par-
ticular plug is younger than the volcanic rocks of the

Traverse Mountains. This relation is commented on

further in the section dealing with the age of these

rocks. As will appear on its description, the rock of

this plug is decidedly aberrant and possibly is not

closely related to the monzonitic and dioritic rocks

previously discussed; however, the assumption of contemporaneity seems reasonable.

Along the tributary in which this small plug crops

out, and only about 200 yards below it, occurs a small

exposure of diorite porphyry whose relations are obscure. The contacts with the alluvium and volcanic

rocks are concealed by talus, and nothing was learned

of either the extent or the shape of the body. Presumably, however, it is related to its better-exposed

neighbor and, like it, is intrusive in the volcanic series

of the Traverse Mountains.

Lithology.- The rock of the small, well-exposed plug

is a dark-gray porphyry. The only megascopically

recognizable phenocrysts are plagioclase, in crystals as

much as 3 millimeters long, and pyroxene, in crystals

about 1 millimeter long on an average but exceptionally

:1 millimeters. In thin section the rock is seen to

possess a seriate porphyritic texture with respect to

the plagioclase, which, with the pyroxenes, occurs as

phenocrysts in a micmpoikilitic groundmass of quartz

and orthoclase. Almost half the rock consists of plagioclase phenocrysts ranging from 3 millimeters down

to about 0.2 millimeters, and a small amount of plagioclase of even smaller grain also occurs in the groundmass. The plagioclase shows combined carlsbad and

albite twinning and is zoned very decidedly. The zoning is abnormal, inasmuch as the central zone is more

sodic (Ab6aAns8 to AbssAn4s) than the border zone

(AbsoAn5oto Ab45An55)' The second mineral in abundance among the phenocrysts is hypersthene, with the

nOll'IIlalpleochroism (X and Y reddish brown and

Z greenish). The mineral occurs in phenocrysts ranging from 0.2 to 1 millimeter in length and in granules

down to the limit of resolving power of a No. '[ objective. It is accompanied by normal augite. The augite

is subordinate to the hypersthene among the phenocrysts but seems tOibe nearly equal to it among the

granulitic pyroxenes. A small amount of biotite occurs, replacing augite and hypersthene along their

borders and cracks. All these minerals are set in a

microgranitic groundmass of plagioclase, orthoclase,

and quartz. If the granulitic pyroxenes are regarded

as a part of the groundmass, it constitutes about 40 per

cent of the total rock; otherwise about 30 per cent.

Magnetite and apatite are accessories.

The abnormal zoning of the plagioclase, the granulitic character of much of the pyroxene, and the occurrence of hypersthene in this rock combine to suggest

that it is contaminated by assimilation of xenolithic

material. The fact that the inner zones of the plagioclase consist of andesine, which is the common feldspar

of the diorites and monzonites of the general region,

together with the presence of the light-green, nonpleochroic augite, which is indistinguishable from that

common to all these normal diorites and monzonites,

suggests that this rock also was derived from the same

magmatic source and that its aberrant features are due

to local causes.

No xenoliths are recognizable in the rock, and if the

abnormality is due to local assimilation the process

appears to have been carried to completion. If it is

assumed that the hypersthene is due to contamination

of the magma, the appeal must be made to either limestone or quartzite as the xenolithic material, for the

Oquirrh formation is almost free from shaly beds.

It is difficult to see how addition of limestone to a

magma saturated with diopside would act to transform this mineral into orthopyroxene, although it

would readily account for the more calcic nature of

the plagioclase border zones. Silica, on the other

hand, as has been suggested by Bowen,sa might react

with an alumina-bearing diopside to yield anorthite

and orthopyroxene, according tol the reaction

SiOa+AlaOs+CaMgSia06 =CaAIaSia08 +MgSiOa

The Fe necessary to produce hypersthene in association with the MgSiOa of this reaction may be assumed

to have been derived from the hedenbergite molecule

of the augite, according to some such parallel reaction as

Si02 +AlaOs+CaFeSia06 =CaAIaSia08 +FeSiOs

The first reaction given above has been suggested by

Bowen to be applicable only to basic magmas, and he

differs with Evans's position ss that such reactions are

effective in producing orthopyroxenes in granitic

magmas such as the charnockite series. However, with

an intermediate magma, such as the monzonite of the

Bingham district, containing about 58 per cent of SiOa,

such a reaction seems conceivable, especially in view

of the prominence of augite and the sparseness of biotite among the mineral phases of the normal rock.

Nevertheless such reactions are by no means the only

ones that might have produced the minerals here

found. Niggli S4has supposed that when the water

content of a magma is insufficient, rhombic pyroxene

and potash feldspar are formed rather than biotite.

Poverty of the magma in water may indeed be the

•• Bowen, N. L., The behavior of inclusions in igneous magmas:

Jour. Geology, vol. 30, pp. 549, 562, 1922.

8S Evans, J. W., discussion of paper by C. E. Tilley, ••The granite,

gneisses of Southern Eyre Peninsula (South Australia) and their associated amphibolites": GeoI. Soc. London Quart. Jour., vol. 77, pt. 2"

p. 133, 1921. Evans suggests the addition of argillaceous material to.

combine with magmatic silica.

SA Niggli, Paul, Homogeneous eqUilibria in magmatic melts and their'

bearing on the processes of igneous rock formation: Faraday Soc..

Trans., vol. 20, pt. 3, p. 434, 1925.
main factor in the persistence of pyroxene as a stable

phase in the monzonite (or diorite) magmas of this

area, but the hypothesis that it is the cause of the

presence of orthopyroxenes has no support other than

its mere possibility. This factor could not account for

either reversal of the customary zoning of the plagioclase or the granulitic character of the pyroxenes, both

of which appear to support the hypothesis of contamination by xenolithic material.

The specimen collected from the small plug downstream from the one whose rock has just been described has suffered so much weathering that its original mafic minerals are unrecognizable. However, its

pl!ligioclase exhibits zoning, from a more sodic interior to a more calcic exterior, in the same manner as

,in that rock, and the presumption is rather strong

that it is a part of the same or a closely related body.

Distribution and strwotural relations. - Rocks

classed by Boutwell as monzonite occur in considerable qU!lintityon the north side of Butterfield Canyon,

adjoining the Bingham Canyon area. Most of the

bodies are sill-like, although the large mass just above

the old Queen mine and the one in the angle between

Blackjack Gulch and the main canyon have crosscutting relations in p!lirt and are better classed as

small stocks. The sills are only 20 to 40 feet thick

as a maximum, and the stocks are likewise small

bodies. There is every probability that all unite with

the main mass of the monzonite at a rather moderate

depth.

Lithology 01 principal type.-The commonest rock

variety of these masses is a medium-gray fine-grained

porphyry in which crystals of plagioclase, biotite, and

pyroxene, rarely exceeding 1 millimeter in length, are

the only megascopically recognizable phenocrysts.

In thin section phenocrysts of andesine (about

Ab6oAn4o),augite, and biotite are seen to occur in a

granitic groundmass of orthoclase, quartz, and plagioclase. The phenocrysts are as much as 1 millimeter in

length; the mineral grains of the groundmass rarely

exceed about 0.4 millimeter in greatest dimension and

average between 0.1 and 0.2 millimeter. The plagioclase occurs in fairly well-formed tablets only moderately zoned. It makes up about one-third of the entire

rock. The pyroxene is a normal augite, light green,

nonpleochroic, and with an extinction angle of 410

•

It constitutes nearly a fifth of the rock. It is somewhat altered tQhornblende in a very few places and to

biotite somewhat more commonly but is chiefly quite

fresh. The hornblende is pleochroic in green and

brown, in small fibrous masses, and occurs only in

small quantities. The biotite occurs not only around

the edges of the augite as reaction rims but independently in the body of the rock. It forms about 5 per

cent of the rock. Orthoclase is an abundant constituent, making up about 30 per cent of the rock. It is

chiefly interstitial to the other minerals, but a few

grains about 0.2 millimeter in greatest diameter are to

be seen. Quartz makes up about 10 per cent of the

rock, in irregular grains, few of which exceed 0.2 millimeter in diameter. Apatite, zircon, and magnetite are

accessory, and a small amount of chlorite after augite

and hornblende also occurs. The rock is a quartz

monzonite porphyry.

Study of thin sections of rocks collected by Keith

and Boutwell from the Bingham district, which included the stock near the Queen mine, shows that this

rock is fairly representative of the monzonite of the

Bingham district, although there is on the average

probably a little more hornblende present in the rock

of the Bingham district than in this. However, the

Bingham rocks, like most of the monzonitic and dioritic rocks of the Stockton and Fairfield quadrangles,

are characterized by the preponderance of augite

among the dark constituents. Biotite and hornblende

are locally more abundant than augite, and even where

the biotite is subordinate to the augite it is more conspicuous in many places, both in the Bingham district

and in the areas to the south covered by this report;

none the less, the generalization just made is believed

to hold.

Lithology of minor fades.-A small sill branching

from the body north of the Queen mine is much more

conspicuously porphyritic than the main body. It is

a dark-gray rock with conspicuous phenocrysts of

hornblende, biotite, and plagioclase in a dense groundmass. The hornblende blades are commonly 3 or 4

millimeters long and exceed this length in places. The

other phenocrysts are smaller. The microscope shows

phenocrysts of common green pleochroic hornblende,

biotite, plagioclase (about Ab7oAnao), pyroxene (in

small vestigial grains, largely altered to hornblende),

and a small amount of quartz set in a groundmass of

quartz, plagioclase, and subordinate orthoclase. The

groundmass is very fine grained and makes up fully

60 per cent of the rock. This facies of the intrusive

rock is to be classed as a quartz diorite porphyry. Despite the mineralogic differences between them, this

rock is undoubtedly a part of the same body as the

monzonite last described. Such local variations are,

of course, to be expected in any intrusive rock.

The dominant sill form of the smaller intrusive

bodies and the evidence of thrusting action of one of

the larger masses, together with the outlines of the
larger masses, suggest forcible intrusion as the mode

of emplacement of these rocks. The writer sees in

their relations no suggestion of" stoping."

All the rhyolitic rocks of the Stockton and Fairfield quadrangles are intrusive. They occur in small

stocks or necks and dikes, although one or two smaller

bodies exhibit concordant relations and constitute sills.

For purposes of description, these rocks are separated

into three local formations-the Eagle Hill rhyolite,

Shaggy Peak rhyolite, and Tickville rhyolite. The

age relations of most of these rocks to the other intrusive bodies are not clear, as they are not in contact,

but the Shaggy Peak rhyolite intrudes and hence is

younger than the latite breccia of the Traverse Mountains. It is not in contact with any of the other

intrusive rocks.

The Eagle Hill rhyolite was named Eagle Hill

"porphyry" by Spurr,35 from its exposures in the

vicinity of Eagle Hill, just south of Mercur.

Distribution and struotural relations.- The occurrences of this rock were interpreted by Spurr as sills

and so appear on his maps. He calls attention, however to the fact that "in places the boundary cuts

acro~s the bedding at a considerable angle, which

sometimes is as much as 90°." The two large bodies

of this rock near Mercur, one west of the Sacramento

mine and the other on the top and south slopes of

Eagle Hill, are both definitely crosscutting and transect over 800 feet of beds of the "Great Blue" limestone, as is clearly shown on the accompanying map.

By no stretch of terminology can these bodies be referred to as "sheets." They are discordant throughout nearly every foot of their contacts. The rock

mapped as Eagle Hill "porphyry" by Spurr and

shown as narrow sills passing through the mines of

Mercur and northward toward Rover Hill is shown

by microscopic study to be either jasperoid, corresponding to the" Silver Ledge" of Spurr, or sandy

limestone altered by contact metamorphism of the

true Eagle Hill rhyolite or by hydrothermal solutions

related to the ore mineralization. There are no

igneous rocks exposed in the mines, according to Butler 36and although the mines are no longer accessible,

ex;osures at and near the portals are still sufficient

to show that the rocks which there resemble altered

igneous material and were so interpreted by Spurr

are actually altered sediments. No true igneous rock

•• Spurr, J. E., Economic geology of the Mercur milling district,

Utah: U. S. Geo!. Survey Sixteenth Ann. Rept., pt. 2, p. 377, 1895.

86 Butler, B. S., The ore deposits of Utah: U. S. Geo!. Survey Prof.

Paper 111, p. 390, 1920.

is exposed in Mercur Canyon north or east of the

rhyolite body near the Sacramento mine.

However, small remnants of true sills composed of

the Eagle Hill rhyolite are to be seen on the south side

of Mercur Canyon near the mouth, about threequarters of a mile somewhat south of east from the

West Mercur town site, and in the NW. 1,4 sec. 2, T. 6

S., R. 4 W. (unsurveyed). Neither of these exposures

covers more than a few feet, however, and none can be

said to be characteristic of the rock.

In Ophir Canyon a dike referred to the Eagle Hill

rhyolite crops out from the bottom of the canyon

nearly to the summit of the north wall at mineral

monument No.4. This dike ranges from 10 to 30 feet

in thickness and cuts straight through its country

rocks, without offset at either the Canyon fault or the

Cliff fault. Its dip is essentially vertical. It is decidedly streaked, showing strong flow banding and

sheeting parallel to the walls. This character was not

observed in any of the other masses.

At its north end the dike appears to coalesce with

an irregular mass of brecciated rhyolite and limestone

which locally has the relations of a sill, although there

is little doubt that it is chiefly crosscutting.

Northeast of mineral monument No.4, near the

top of the north wall of Ophir Canyon, are a few

exposures of this rhyolite breccia containing a great

number of limestone fragments. At first these exposures were interpreted merely as inclusions in the

rhyolite, but careful study of many outcrops at this

point and in Dry Canyon, where similar masses were

observed, led to the discovery that all gradations occur

between rhyolite containing sporadic angular fragments of limestone and limestone breccia containing

isolated angular fragments of rhyolite. Many or even

most of the limestone inclusions in the rhyolite are

interpreted as xenoliths acquired during the original

injection of the magma, but the rhyolite fragments in

limestone imply either a renewal of intrusion which

led to the brecciation of already consolidated rhyolite

or postrhyolite faulting. The second suggestion is

given weight by the fact that locally the rhyolite

breccia follows the Cliff fault, but as the dike crosses

the same fault a quarter of a mile to the south without

being offset, it seems unlikely that important postrhyolit{l faulting has occurred here. Even if faulting

has recurred at this point, the presence of a number

of other breccia outcrops in Dry Canyon, so related as

to be inexplicable by postrhyolite faulting, led the

writer to the conclusion that most of the brecciation is

due to renewal of intrusion.

A large mass of rhyolite breccia lies on the hill

slope above the Dry Canyon portal of the Hidden

Treasure mine. This body has obscure contacts, but

may represent ll; sill, as little igneous rock occurs in
constitutes a volcanic plug. The plug is about half a

mile long and about a third of a mile wide, of roughly

ovoid shape.

Litholofl!!.-The Shaggy Peak rhyolite has two chief

varieties. One variety consists of a light-gray rock

carrying numerous rounded and fractured phenocrysts

of very dark colored quartz ranging from 2 to 5 millimeters in length, with subordinate white or colorless

feldspars of somewhat smaller size, in a groundmass

that presents no directional features. This variety of

rock occupies the central portion of the plug or at

least makes up a large part of the plug. The other

variety is more purplish gray, and contains far fewer

and very much smaller phenocrysts. The dark quartz

phenocrysts are chiefly less than 1 millimeter in length,

and the feldspar crystals are of about the same size.

A very few small flakes of biotite are also recognizable

in hand specimens. These phenocrysts are set in a

stony-textured groundmass which exhibits intense flow

structure. Cross fractures due to tension during flow

of the viscous mass are common, and fluidal lines

marked by streaks of phenocrysts as well as slight

variations in grain size are prominent. This variety

of the rock forms the border of the mass, which

accounts for the prominence of the flow structure.

Only one thin section of this rock was studied. This

section, representing the fluidal border facies, exhibits

strong sheeting on a microscopic scale. This sheeting

is developed chiefly in the groundmass, and the phenocrysts of both quartz and sanidine are little broken.

The quartz occurs in irregular aggregates of subhedral

grains. Most of the aggregates are less than 1 millimeter in diametBr. The sanidine crystals are chiefly

oriented parallel to the streaking of the groundmass.

They are more nearly euhedral than the quartz and

form clear-cut prisms with small optic angle. They

probably have a rather high soda content. No plagioclase phenocrysts occur in this slide. A few biotite

crystals with frayed edges are present but offer no

unusual or noteworthy features. Microphenocrysts of

apatite and magnetite are not uncommon.

The groundmass is microcrystalline granular, with

little or no glass, despite the small size of the phenoerysts, which would suggest very imperfect crystallization of the groundmass. Quartz and alkaline feldspar

are the only recognizable minerals of the groundmass.

Olas8ifio(JJtion.-The presence of quartz and sanidine

as the sole salic phenocrysts and the negligible

quantity of mafic constituents, together with the

porphyritic development and very fine-grained groundmass, permit the classification of the rock only as a

porphyritic rhyolite. Its distinction from the Eagle

Hill rhyolite rests on its markedly different texture,

the Eagle Hill rhyolite possessing few phenocrysts

even in its coarser facies and nowhere exhibiting such

marked flow structure as characterizes the border

facies of the Shaggy Peak plug. The Shaggy Peak

rock is also without plagioclase phenocrysts.

Distribution and structural reZations.-The rocks of

five small bodies are here named Tickville rhyolite,

because of the grouping of the masses near Tickville

Gulch. All are intrusive, so far as could be discovered.

Two small dikes of the Tickville rhyolite cut the

Oquirrh formation in the SE. :l;4 sec. 34, T. 4 S., R. 2

W., about half a mile west of Tickville Gulch; the

other exposures of this rock are in section 26. The

exposures near the center of section 26 are tather poor,

but the rock appears to intrude the latite flows and the

Oquirrh formation. A fifth exposure of the Tickville

rhyolite forms the round white hill next east of the

6,355-foot hill on the north boundary of section 26.

This mass appears to be a breccia plug which cuts

through the Oquirrh formation.

Lithology.-The breccia plug just mentioned exhibits two principal rock varieties. One is a palegray to dull-white breccia, consisting of angular fragments of rhyolite in a rhyolitic groundmass. The

other has a similar rhyolitic matrix but contains breccia fragments of rhyolite, quartzite, and some chert

(or jasperoid) as much as 2 or 3 centimeters in diameter. Both varieties are highly altered, kaolinized, and

silicified, with a porcellaneous appearance and decidedly conchoidal fracture. The only recognizable

phenocrysts are quartz in crystals as much as 3 millimeters long and a few feldspars as much as 1 centimeter long.

The rock from the small plug near the center of

section 26 is also highly altered. Its color ranges

from pinkish and yellowish gray through light purplish gray to porcellaneous white. No brecciation

was observed at this locality. Quartz phenocrysts as

much as 3 millimeters long are common, and a few

feldspar crystals as much as 6 millimeters long were

recognized. No mafic minerals occur as phenocrysts.

These rocks are also highly altered, and a small

amount of pyrite has been developed.

The rocks of the dikes in section 34 are of a light

cream color. Alteration has induced a chalky appearance. No noteworthy features beyond the occurrence of numerous quartz phenocrysts and sporadic

minute quartzite inclusions were observed.

Alteration of all these rocks has been so intense that

microscopic study reveals little more than megascopic

study as to their original character. The silicified

breccia contains a small percentage of quartz phenocrysts. These arc considerably fractured but not

notably resorbed and contain numerous inclusions of

the ground mass of the rock. These phenocrysts are 1
or 2 millimeters in greatest length. All the feldspar

phenocrysts have been altered beyond recognition of

their original character. They are now represented

by cavities of feldspar crystal shapes partly filled

with spherulitic aggregates of a clay mineral. This

mineral is probably dickite,37 as it has oblique extinction and is optically positive, with birefringence of

about 0.006 and with indices slightly higher than that

of canada balsam. The groundmass has entirely

lost its original character and is thoroughly opalized.

No mafic minerals are to be seen. A little calcite and

considerable sericite are present.

Little information is yielded by study of the sections representative of the dikes in section 34. Alteration has been so intense as to have masked almost completely the original character of the rock. However, a

few broken phenocrysts of quartz and sanidine occur,

as well as a very few of oligoclase. No mafic minerals

are recognizable. The groundmass is thoroughly altered to isotropic material of lower index than balsam-presumably opal with perhaps a little allophane.

Olas8ification.-Inasmuch as alteration of these

rocks has been so intense, it is now impossible to

ascribe accurate quantitative values to the original

mineral constituents. The only statements which can

be made with confidence are that quartz is the dominant phenocryst mineral and that sanidine is the next

mO<ltplentiful. These facts suffice,however, for placing the rocks as rhyolites, in the qualitative classification of Rosenbusch. Although they resemble somewhat the more altered facies of the Eagle Hill rhyolite, the resemblance is not so close as to warrant the

exteIlsion of that term to cover the rocks of these

more easterly occurrences.

ANDESITE OR LATITE INTRUSIONS

The rocks discussed here would be classed as andesites frpm their microscopic characters. Their resemblances to the analyzed flow rocks, however, are

exceedingly strong, and inasmuch as all the andesitic

flow rocks analyzed carry notably more potassa than

soda and hence are to be classed as latites, it is highly

proba.ble that chemical analyses would reveal the same

relationships in these rocks. Thus they are tentatively

called latite.

Distribution and structuml relations.-Andesite or

latite occurs as minor intrusions at two localities in

the Fairfield quadrangle. The more conspicuous occurrence is the volcanic plug at Step Mountain, in the

NE. 1,4 sec. 16, T.· 4 S., R. 2 W. This is a beautiful

example of a volcanic neck, a cylindrical column of

elliptical shape, about 1,000 feet long and somewhat

less than 1,000 feet wide, standing as a prominent

37 Ross. C. S., and Kerr, P. F., Dickite, a kaolin mineral: Am.

Mineralogist, vol. 15, pp. 34-39, 1930.

topographic feature above the volcanic breccias surrounding it. The topographic prominence of the neck

is emphasized by a vertical bordering ring dike which

can be traced entirely around the neck except for a

short distance on the northwest flank where talus obscures the relations. (See pI. 10, A.) This dike has

'well-developed columnar jointing normal to its walls.

This feature is seen in Plate 10, B, and it is doubtless

in reference to the steplike profile of the columnar

jointing that the name of the mountain was given.

The center of the plug is of massive andesite or latite

porphyry carrying many xenoliths, although the rock

is not a typical agglomerate.

The other intrusion of andesite or latite porphyry is

a dike in the northern part of sec. 4, T. 5 S., R. 2 W.

This dike, which is about 50 feet in maximum width,

trends northeastward and cuts through latite breccia

for about a quarter of a mile; then, with a short offset,

it cuts through the Oquirrh formation and bounds, in

part, a small breccia plug. The dike dies out to the

north near the line between Ts. 4 and 5 S., R. 2 "'iV.

This dike also has nearly horizontal columnar jointing

similar to that of the ring dike at Step Mountain.

The small volcanic plug associated with this dike

near its central part is only about 200 feet in diameter

and appears to have nearly vertical walls. The andesite breccia composing it is highly altered and is

stained red-brown throughout. It represents a minor

volcanic vent.

Mention should perhaps be made of a much altered

andesitic rock found along the east side of the rhyolite plug on the north flank of Bald Mountain, in the

Stockton quadrangle. The specimen collected was too

highly altered to permit any more definite statement

than that the rock has an andesitic texture. The exposure is small, and nothing is shown of the relations

of the rock to the rhyolite.

Lithology.-The dominant rock of the Step Mountain plug is a light-gray, very coarsely porphyritic

biotite-hornblende andesite or latite. In hand specimens it closely resembles many of the latites of the

flows but on the whole carries larger phenocrysts than

most of the flow rocks. The plagioclase phenocrysts

reach dimensions of 1.5 centimeters, hornblende 1

centimeter, and biotite 3 millimeters. In thin section

the rock greatly resembles the latite flow rocks. The

plagioclase phenocrysts are slightly more sodic than

Ab7oAn30' Biotite and hornblende are much like

those of the flow rocks, except that the hornblende is

pleochroic in greens rather than browns and has a

slightly large,r extinction angle. Augite grains as

much as 0.5 millimeter in diameter are abundant constituents of the rock. A few olivine crystals also

occur. Several resorbed quartz crystals of rounded

and embayed outline were seen, but it is difficult to
accept them as normal constituents of the rock, despite

the occurrence of similar grains in many of the flows.

It seems more likely that the quartz is xenolithic, a

suggestion which receives some support from the considerable number of quartzite fragments of various

sizes which the plug contains. A small amount of

orthoclase appears in the groundmass of the porphyry.

Apatite and magnetite are accessories. Analcite and

other zeolites that are too fine grained for specific determination in thin section are present as alteration

minerals. The texture of the rock is porphyritic, with

a groundmass that ranges from pilotaxitic to microgranular.

A subordinate facies of the plug, with a darker and

less coarsely porphyritic aspect than the main mass,

appears near the borders. The only phenocrysts recognizable in hand specimens are hornblende, with a

tendency to be arranged in rosettes. The microscope

reveals a rock with green pleochroic hornblende, biotite, augite, and iddingsite pseudomorphs after olivine

as the dominant dark minerals, set in a subvariolitic

mass of plaiioclase of composition slightly more sodic

than Ab7oAn3o. The hornblende also has a tendency

toward radial arrangement, but the other mafic minerals are chiefly in irregular crystal aggregates. No

unusual mineralogic features were noted in the rock,

which is obviously merely a textural variant of the

mam mass.

The dike in sec. 4, T. 5 S., R. 2 W., is composed of

light-gray quartz-bearing biotite-hornblende andesite

or latite, with a bordering selvage a few inches to a

few feet thick of dark-gray porphyry. The light-gray

facies contains plagioclase phenocrysts of a composition close to Ab7oAn3o,which reach 4 millimeters in

length. Brown hornblende and biotite occur as

phenocrysts. Augite is present in small amount,

chiefly as groundmass microlites. A very few crystals

of quartz occur as phenocrysts. Zircon, apatite, and

magnetite are accessories. The texture is porphyritic,

with a chiefly pilotaxitic groundmass that in places

varies to hyalopilitic.

The mafic border facies of the dike carries only a

slightly higher proportion of dark minerals than the

light-gray central facies. No quartz phenocrysts are

present. The only other differences between the two

varieties are in the presence of a considerably greater

number of augite microlites in the groundmass of the

dark rock and in its larger percentage of glass. The

texture of the dark facies is accordingly porphyritic

with a hyalopilitic groundmass.

Di.stribution and struotwral relations .-Three sills

of nephelite basalt occur near the west end of South

Mountain, in the Stockton quadrangle, in secs. 17 and

18, T. 4 S., R. 5 W. The most easterly outcrop is

in a saddle of the east-west ridge of South Mountain at about the 6,000-foot contour. The intrusion

takes the form of a sill about 40 feet thick which can

be traced for about half a mile. It is obscured by talus

in both directions, so that how much farther it extends is not known, but inasmuch as it is rather thin

at the extreme exposures the total length is presumably but little greater than the exposed length.

Two sills occur on the crest of the western summit

of South Mountain but can be traced only a few hundred feet. Neither exceeds 15 feet in thickness. A

fourth outcrop, too small to be shown on the accompanying map, occurs in a small gulch in the NE. 14

sec. 13, T. 4 S., R. 6 \V., on the north slope of South

Mountain. This exposure probably represents a pipelike intrusion, for it can not be traced in any direction

and occupies only a very small area.

Lithology.-The rock forming these sills is very

dark greenish gray on fresh fracture, but weathers

with rusty shades. It has a porphyritic texture, with

phenocrysts of greasy-Iustered olivine as much as 5

millimeters long and of biotite perhaps as much as 3

millimeters long in a fine-grained groundmass in which

minute plates of biotite are the only visible grains.

The microscope reveals a porphyritic texture in

which olivine forms the dominant phenocrysts, although it is in part inclosed poikilitically by still

larger plates of light-colored biotite. The olivine

cystals range from 0.3 to 5 millimeters in length and

ure subhedral, showing some resorption with development of a border phase of pyroxene and resultant partial obliteration of the crystal outlines. They constitute about 20 per cent of the entire rock.

Diopside, although the dominant mafic mineral, constituting about 40 per cent of the rock studied, occurs

only in small crystals, ranging from about 0.05 to possibly 0.3 millimeter in length. These crystals are subhedral, most of them having the prism, side, and front

pinacoids well developed, with terminal faces poorly

developed or absent. Many of the crystals are poikilitically inclosed by biotite, and others exhibit slight

lesorption, with biotite as a magmatic reaction 'product. They are of pale-green hue, nonpleochroic, opti-

, cally positive with notable dispersion, p>1J, shown by

the optic axis emergent on 100 and no dispersion

shown by the axis emergent on the base. Extinction

angles as great as 43° Zl\o were measured. These

properties do not indicate a notable content in alkalies.

The biotite is of late crystallization and incloses

diopside and olivine, forming sporadic pseudophenocrysts about 2 millimeters in maximum size, although

most of the biotite grains are less than 0.3 millimeter

long and are interstitial. The mica exhibits variable

pleochroism, most of it being abnormal, with absorp-
tion X> Y = Z, although some has normal absorption

Y=Z>X. The biotite is of faint-yellow color, with

darker hues around the borders of the crystals. Both

the light and the dark portions of crystals show abnormal absorption, and in some individuals both show

normal absorption. The mica makes up about 20 per

cent of the rock. Mica having the abnormal pleochroism scheme of the variety first described has been

reported by Ross 38 from a Montana alnoite, by 'Vagner 39 from South African kimberlite, and by Ross 40

from Arkansas kimberlite (peridotite). It seems to

be not very rare in alkalic rocks.

The above-described mafic constituents are embedded in a matrix of anhedral nephelite. This mineral is colorless and exhibits parallel extinction with

two cleavages, the better of which is parallel to the

faster ray. In thicker portions ofthe slide the uniaxial

negative character of the mineral is determinable. Its

indexes are slightly higher than that of canada balsam and its birefringence not higher than 0.006.

These properties suffice to determine the mineral as

nepheline. It is interstitial to the mafic minerals, but

areas in optical continuity and inclosing mafic minerals reach dimensions as great as 0.2 millimeter. The

mineral makes up about 15 per cent of the rock.

Magnetite and apatite to the extent of about 2 per

cent of the rock complete the list of primary minerals.

No feldspar was observed in the slide examined.

The rock is remarkably fresh. The only alteration

products observed were about 3 per cent of analcite

and almost negligible quantities of a confused aggregate of cancrinite, hydronephelite, or some zeolite,

such as thomsonite, with a fairly high birefringence.

These minerals are probably derived solely from alteration of the nephelite by late magmatic or more likely

hydrothermal reactions.

Olassification.-As this rock is lacking in feldspar

and carries nephelite as the only primary salic mineral, it is classed as a nephelite basalt, although the

conspicuous biotite is an abnormal feature in nephelite

basalt. The conspicuous biotite and the dark aspect

give the rock a resemblance to the lamprophyre camptonite, but the absence of alkalic amphibole and plagioclase distinguish it.

Distrib11!tion (Jj}1,(j structural reZations.-Lamprophyre

dikes crop out in four places in Ophir Canyon. The

exposures are all poor, owing to the rapid disintegration of the rock. The most southerly dike crops out

on the northwest flank of Lion Hill, near the old Zella

as Ross, C. S., Nephelite-hauynite alnoite from Winnett, Mont.: Am.

Jour. Scl., 5th ser., vol. 11, p. 219, 1924.

••Wagner, P. A., The diamond fields of South Africa, p. 58, 1914.

'" Miser, H. D., and Ross, C. S., Diamond-bearing peridotite in Pike

County, Ark. : U. S. Geol. Sur\'ey Bull. 735, pp. 315-316, 1923.

mine. The ore shoot in this mine is reported to have

followed the dike rather closely. The dike is about 4

feet thick, dips vertically, and, though poorly exposed,

can be followed with some interruptions for about a

quarter of a mile northward from the Zella mine. A

hundred yards or so to the south of the Lion Hill fault

this dike is well exposed in two tunnels which have

been driven along it. The dike can not be traced to

the north of these prospects. However, nearly on the

strike of this dike there is a small exposure of lamprophyre about 30 feet west of the portal of the new

Ophir Hill adit. This dike is not continuous on the

surface and can not be traced any appreciable distance, but a similar body of lamprophyre, now highly

altered by hydrothermal solutions, was cut in the new

Ophir Hill shaft at about 1,350 feet below the surface.

Where cut in the shaft, this lamprophyre is of

irregular shape but tends to conform roughly to the

bedding.

On the north side of Ophir Creek there is a small

exposure of lamprophyre on the east side of Hartmann

Gulch, just below the headframe of the projected

Ophir Central shaft. Here the rock forms a dike

about 4 feet thick which strikes north and appears to

have a nearly vertical dip. It is exposed for only a

short distance and appears to be cut off by a fault of

the Canyon fault system, but this is not certain. The

rock probably crops out somewhere to the north in the

east fork of Hartmann Gulch, as cOlllsiderablefloat was

found there, but diligent search failed to reveal the

rock in place.

A fourth exposure of lamprophyre occurs on the

Admiral Dewey claim, about half a mile north of the

Ophir Central headframe. A prospect tunnel has

been driven along this dike, which ranges from 1 to 4

feet in width. The dike strikes N. 40° E. and dips

70° ""V. It can be traced only a few hundred feet

owing to talus and brush cover.

A lamprophyre is cut by the 71jz drift of the Ophir

Hill mine, about 900 feet east of the 71;2 No. 2 fissure.

This is presumably a continuation of the dike that

crops out on the Admiral Dewey claim. It is possible

that this dike is the same as the one at the Ophir

Central shaft. If it is, the dike is earlier than the

Canyon fault and gives a measure of the hOil.'izontal

displacement of that fault of about 800 feet, on the

nssumption that the dike is vertical at this point.

However, in view of the apparent discontinuity of the

dikes as known, it is not at all certain that the dike is

cut off by the Canyon fault. They may be distinct

intrusions of postfaulting age. If so there is no way

of dating the lamprophyres within the igneous period;

but if the lamprophyre is really cut off by the Canyon

fault, it is older than the Eagle Hill rhyolite, which

is younger than the fault. (See p. 58.)
An exposure (too small to be shown on the accompanying map) of a rock strongly resembling these

lamprophyres occurs on the crest of the ridge that rises

north of the junction of the south fOll'kof Ophir Creek

with the main stream. The exposure is very small,

and the rock could not be traced. No other lamprophyres were discovered during the survey of these

quadrangles.

LithoZogy.-The lamprophyre is a dark-gray to

greenish-gray rock of very fine grain. It readily

weathers to a greenish or greenish-brown rock with

spheroidal tendencies. One or two inclusions of

quartzite were observed, but on the whole the rock is

free from foreign material. The only mineral recognized in hand specimens is biotite, in very small plates,

of which the largest hardly reach 1 millimeter in

length.

In thin section the texture is panidiomorphic to

hypidiomorphic. There is some tendency to porphyritic development of olivine (now represented by serpentine), some crystals of which reach 1 millimeter

in length. The olivine shows considerable resorption,

although enough of the .original outlines remain to

permit identification of the mineral. The reaction of

the olivine and the residual magma during the consolidation process resulted in the formation of biotite borders around many grains. A great deal of

biqtite in well-formed plates occurs. This mineral

has normal pleochroism, Very pale green augite is

present in prisms, which, however, have poorly developed basal pinacoids. In many specimens the augite

is considerably altered to uralitic hornblende, with

faint pleochroism in greens. Plagioclase microlites

and once-twinned plates occur with well-developed

crystal faces. They are labradorite, with composition approximately Ab45An55' Apatite and magnetite

are prominent minor constituents of the rock, and

calcite is a conspicuous alteration product. One or

two slides showed rather large crystals of quartz with

reaction rims of biotite. These are probably xenoliths

and are not uncommon in lamprophyres, despite the

fact that many of these rocks are olivine bearingY

The ferromagnesian minerals predominate over the

feldspar. Among these minerals biotite appears to

predominate, although in some specimens augite is

more abundant. No hornblende except the uralite replacing the augite was seen. Olivine pseudomorphs

occur in varying amounts, at most nearly 20 per cent

of the rock, but in some slides very little olivine was

seen.

The specimen collected from the new Ophir Hill

mine shaft is highly altered. The biotite, olivine, and

pyroxene of the original rock are recognizable by the

<1 Rosenbusch, H., Elemente der Gesteinslehre, 4th ed., by A. Osann,

pp. 329-330, Stuttgart, 1923.

ghosts of their crystal outlines and sufficeto show, by

their textural and quantitative relations, that the rock

belongs to the lamprophyre suite. The rock is, however, reduced to a confused aggregate of bleached serpentine, carbonates, and an isotropic base of index n

close to 1.55, probably halloysite.

Olassijication.- The texture of the rock and the predominance of biotite and plagioclase show that it

should be classified as the lamprophyre kersantite.

GEOLOGIC RELATIONS OF THE IGNEOUS ROCKS

MUTUAL RELATIONS

As is evident from the detailed descriptions above,

contacts among the several varieties of igneous rocks

are few, and their mutual relations are accordingly not

well known. This is especially true of all the igneous

bodies west of the main divide of the Oquirrh Mountains, no two of which are in contact.

Little more detailed information is available with

respect to the rocks in the northeastern part of the

Fairfield quadrangle, but the general sequence is indicated-latite breccias, followed by latite flows, volcanic

necks and dikes, and lastly monzonitic intrusions.

The wide diversity of rock varieties found at the

base of the volcanic series'affords little ground for any

conclusions as to the relative order of eruption of the

various rocks. The most that can be said is that of

the volcanic rocks remaining in the area, latitic rocks

form the overwhelming proportion; basalt, trachyte,

nephelite basalt, and rhyolite obsidian all locally preceded them or were intercalated in the lower part of

the series, and rhyolite and andesite or latite dikes followed them. Possibly the volcanic cycle was ended by

basalt eruptions, but this is uncertain. It is perhaps

noteworthy that here, as at many other localities in

Utah the most extensive fragmental deposits occur

, . .

near the base of the senes and the flows becomemcreasingly abundant toward the top.42 .

As stated in the detailed descriptions, several latIte

dikes and two volcanic necks cut the extrusive rocks.

This is naturally to be expected in any volcanic area

and can hardly be considered evidence of any notable

age difference. In fact, it is entirely probable that

the Step Mountain volcanic neck was the source of at

least a part of the extrusive rocks of the area. The

Shaggy Peak rhyolite also may be only slightly

younger than the rocks which it intrudes.

In Tickville Gulch (see p. 55) a small stock of

dioritic rock is intrusive into a quartz latite flow. The

intrusive rock is somewhat aberrant, but there is no

42 Butler, B. S., The ore deposits of Utah: U. S. GeoI. Survey Prof.

Paper 111, p. 89, 1920; Geology and ore deposits of the San Francisco

and adjacent districts, Utah: U. S. Geol. Survey Prof. Paper 80, pp.

44-45, 1913. Lindgren, Waldemar, and Loughlin, G. F., Geology and

ore deposits of the Tintic mining district, Utah: U. S. Geol. Survey

Prof. Paper 107, pp. 54, 75, 1919.
evidence that it is of different age from the other

dioritic or monzonitic rocks of the area. Accordingly

it is tentatively held that the extrusive rocks as a

whole antedate the intrusives, although the. intervening time may have been very short. This conclusion

is diametrically o/pposedto that reached by Emmons 43

and by Boutwell and Keith 44in the Bingham district.

Although it would be easy to exaggerate evidence

obtained from a single isolated exposure, such as the

one in Tickville Gulch, especially in view of the somewhat aberrant composition of the intrusive stock, still

the relations at this point are unequivocal, and there is

no doubt that the dioritic rock has cut and metamorphosed the extrusive quartz latite. Therefore more

weight is given to this one actual exposure than to the

topographic relations which suggested to Emmons,

Keith, and Boutwell that the extrusives were much

younger than the intrusives. That the conclusion here

set forth of a slightly greater age of the extrusives

accords with the topographic relations of the two rocks

is evident from the fact that it was advanced as a suggestion by Butler 45merely from analogy with other

neighboring localities and a study of the geologic

maps. That all the rocks are comagmatic seems beyond doubt, because of the remarkable resemblances

between the extrusives and intrusives and the rather

constant composition of the intrusives throughout most

of the Oquirrh Mountains. The rhyolites, lamprophyres, and nephelite basalts differ considerably in

chemical composition from the monzonites and latites,

but there is no reason to doubt that these are merely

differentiation facies of the normal intermediate

magma. The magmatic differentiation of the area is

discussed on page 66.

The fine interbedding of tuffs and breccias and their

diversity in dip due to postvolcanic disturbances leaves

no clue as to the locations of their sources. It is safe

to say there are no volcanic necks in the area of the

main Oquirrh Mountains within these quadrangles

which could have been a source for the material.

However, Step Mountain, in sec. 16, T. 4 S., R. 2 W.,

is an old volcanic plug, and a second small plug occurs

in sec. 4, T. 5 S., R. 2 W. It is very probable that

still other necks existed in the area now covered by

alluvium in Jordan, Cedar, and Utah Valleys, to the

east of this area, for andesitic and latitic flows and

breccias are very widespread in this part of Utah,

being found in the Park City district, about 20 or 30

., Emmons, S. F., Geology of the Bingham mining district, Utah:

U. S. Geol. Survey Prof. Paper 38, pp. 24-25, 1905.

••Boutwell, J. M., and Keith, Arthur, idem, pp. 50, 55, 56.

45 Butler, B. S., The ore deposits of Utah: U. S. Geoi. Survey Prof.

Paper 111, p. 337, 1920.

miles to the east,46and in the Tintic district, about the

same distance to the southY There is every probability that such necks communicate at depth with the

magma chamber from which sprang the monzonitic

and rhyolitic stocks now exposed by erosion.

The relative ages of the intrusive and extrusive

rocks indicated by the evidence reviewed above is in

line with the conditions found at Tintic 48and in the

San Francisco district.49 Butler 50 has also given

reasons for believing, contrary to the conclusions of

Leith and Harder,51 that in the Iron Springs district

the intrusive rocks are the younger, the whole activity,

however, being essentially continuous. Butler also describes similar relations in the Marysvale district,52 in

the Tushar Range, and points out that although Boutwell and Woolsey 53note their belief that the extrusives

of Park City are younger than the intrusives, still they

postulate essential contemporaneity of the tWO.54 In

view of the additional information furnished by the

present study, Butler's conclusion 55that" the igneous

rocks represent one long general epoch of igneous

activity, during which both intrusion and extrusion

occurred," seems strengthened. However, sight should

not be lost of the fact that in the Deep Creek Range,

only 90 miles west of the Oquirrh Mountains, a considerable period of erosion followed the intrusion of the

pIutonic rocks before the extrusi ves were erupted. 56

From evidence obtainable within the Stockton and

Fairfield quadrangles it can only be stated that the

volcanic rocks of the area are much younger than the

folding of the Paleozoic rocks and much older than

the Lake Bonneville beds, of Pleistocene age. To fix

the date more closely it is necessary to appeal to a

parallelism in geologic history between this area and

near-by areas.

A.sis pointed out on page 73, the most probable date

of the folding of the Oquirrh Mountains is postCretaceous, probably very early Tertiary. The volcanism can accordingly be fixed as post-Cretaceous.

46 Boutwell, J. M., Geology and ore deposits of the Park City district,

Utah: U. S. Geol. Survey Prof. Paper 77, pp. 69-75, 1912.

47 Lindgren, Waldemar, and Loughlin, G. F., Geology and ore deposits

of the Tintic mining district, Utah: U. S. Geol. Survey Prof. Paper

107, pp.'42-63, 1919.

48 Idem, p. 75.

•• Butler, B. S., Geology and ore deposits of the San Francisco and

adjacent districts, Utah: U. S. Geol. Survey Prof. Paper 80, p. 50, 1918.

50 Butler, B. S., The ore deposits of Utah: U. S. Geoi. Survey Prof.

Ps.per 111, p. 571, 1920.

51 Leith, C. K., and Harder, E. C., The iron ores of the Iron Springs

district, southern Utah: U. S. Geol. Survey Bull. 338, p. 46, 1908.

52 Butler, B. S., op. cit. (Prof. Paper 111), p. 539.

53 Boutwell, J. M., and Woolsey, L. H., Geology and ore deposits of

the Park City district, Utah: U. S. Geol. Survey Prof. Paper 77, p. 93,

1912.

54 Idem, p. 67.

55 Butler, B. S., op. cit. (Prof. Paper 111), p. 99.

•• Nolan, T. B., Geology and ore deposits of the Gold Hill quadrangle,

Utah: U. S. Geol. Survey report (in preparation).
In the southern Wasatch Mountains near Santaquin,57 at the south end of the East Tintic Mountains,58 in the Canyon Range,59 and in the northern

part of the Wasatch Range 60 volcanism was later than

Eocene conglomerate, and it is reasonable to suggest

that the volcanism of the Oquirrh Mountains likewiEe

occurred during late Eocene (post-\Vasatch) or postEocene time.

3

W

<b

~

Z

W

U

0:: 2

W

a.

I

I

I

I

I

have the appearance of andesites, the fact that all of

those analyzed have the alkali ratios characteristic of

latites, whether they contain orthoclase or not, justifies

the inference that all may belong to the latite and

quartz latite groups. The consanguinity of these

latitic lavas and the monzonites of Bingham is emphasized by the following regrouping of partial

chemical analyses.

+- °A 70% 2 3 4 60% 6 ~ 7

5i02 5 Averageintrusive

monzonite of

Bingham district

FIGURE 8.-Relations of weight percentages of CaO, Na20, and K20 with variations in the silica content of the analyzed rocks from the Oquirrh Mountains. A, Rhyolite obsidian described on page 47;

1-7, rocks of which partial analyses are given below

There is evidence in the' tilting of the volcanic rocks

roughly parallel to the eastward tilt of the Oquirrh

Mountain block (see p. 86) that the volcanism preceded the principal" Basin Range" fault movement

ef the Oquirrh block. The date of this movement is

uncertain but probably not later than late Pliocene nor

earlier than Oligocene. As the considerable erosion

which mUf'ltbe conceded to have followed the volcanism in order tOIhave exposed the intrusive rocks took

place chiefly earlier than the faulting, a late Eocene or

Oligocene date of the volcanism seemsmost reasonable.

PETROLOGIC RELATIONS OF THE IGNEOUS ROCKS

The close relationship between the chief varieties of

cxtrusives is evident from their petrography. Although several of the type volcanic rocks described

57 Loughlin,G. F., Reconnaissance in the southern Wasatch MOUDtains: .Tour. Geology, vol. 21, p. 448. 1913.

58 Tower, G. W., and Smith, G. 0., Geology and mining industry of

the Tintic district, Utah: U. S. Geol. Survey Nineteenth Ann. Rept.,

pt. 3, p. 673, 1899.

59 Loughlin, G. F., A reconnaissance in the Canyon Range, west-central

Utah: U. S. GeoI. Survey Prof. Paper 90, p. 51, 1914.

60 Emmons, S. F., U. S. Geol. Expl. 40th Par. Rept., vol. 1, PP. 586-

587, 1878.

Partia,l analyses of predominant latitic volcanic rocks of the

Fairfield quadrangle and mOrnzonite of the Bingham district

1 2 3 4 __5_1__6

__

7

SiO2_______ 66.90 65. 64 61. 09 60. 90 59. 86 58.64 .57.16

CaO ______. 2.35 3. 26 4. 70 4.16 4. 62 5.37 5. 86

Na20. ----c 3. 34 3. 26 3. 00 3. 26 3.31 3.60 3.82 K2O _______ 3.75 3.50 3.77 3.28 4.84 4.23 4. 49

1. Quartz latite from Tickville Spring, Fairfield quadrangle.

J. G. Fairchild, analyst. (Contains individualized orthoclase

in ground mass, none in phenocrysts.)

2. Quartz latite from northwest corner of sec. 2, T. 5 S., R. 2

W. Fairfield quadrangle. J. G. Fairchild, analyst. (Contains

no recognizable orthoclase:)

3. Quartz-bearing latite from Oak Spring Canyon, Fairfield

quadrangle. J. G. Fairchild, analyst. (Contains no recognizable orthoclase.)

4. Hornblende-biotite andesite (latite) from the Bingham district. Boutwell, J. M., and Keith, Arthur, Geology of the Bingham mining district, Utah: U. S. Geol. Survey Prof. Paper 38,

p. 130, 1905.

5. Hypersthene-augite latite from southwest corner of sec.

8, T. 4 S., R. 2 W., Fairfield quadrangle. J. G. Fairchild,

analyst. (Contains individualized orthoclase in the groundmass.)

6. Monzonite, British tunnel, Bingham. E. T. Allen, analyst.

Boutwell, J. M., and Keith, Arthur, op. cit., p. 178.

7. Monzonite, Tribune tunnel, Bingham. E. T. Allen. analvst. ldem.
Although the molecular ratios of potassa calculated

from the percentages in these analyses do not equal

those of soda, they are sufficient to demonstrate a monzonitic magma.

The two analyses of monzonite from the Bingham

district may be considered representative of by far

the most of the monzonitic rocks of the Stockton and

Fairfield quadrangles. There are, however, many

minor variations, as has been already pointed out in the

petrographic description of the rocks. None of these

variations, toward diorite, quartz diorite, granodiorite,

or quartz monzonite, are sufficiently divergent from the

average to imply more than very moderate differentiation. Comparison of these two partial analyses with

the partial analyses of the latitic extrusive rocks reveals

:t decided relationship, shown especially well by the

proportions of the alkalies. (See fig. 8.) Plotting the

CaO, K20, and Na20 as ordinates and the silica as

abscissas reveals the interesting fact that the soda

shows almost linear decrease with increase of silica.

The average slope of the curve of soda is almost precisely that which would appear from the mere addition of silica to the monzonite magma. However, the

lime decreases at a rate altogether disproportionate

to the silica content, and the potassa remains very

nearly constant or decreases at a much lower rate than

the silica increases. This relationship is close to that

which would be expected as a result of differentiation

of a monzonitic magma by fractional crystallization,

in accordance with the theory to which Bowen 61 has

contributed so much weighty evidence. The more

siliceous and less calcic character of the lavas as compared with the intrusive rocks is rational on the basis

that the upper parts of the magma chamber, from

which the early calcic minerals would be eliminated by

sinking, would consistently furnish the material of

volcanic eruptions.62

The rhyolite intrusions and obsidian flows may have

been similarly derived from the originally monzonitic

magma by the elimination through settling of the

early formed crystals of calcic plagioclase and mafic

minerals by crystal sinking; however, the lamprophyres are not satisfactorily explained on this basisa fact that constitutes one of the most serious flaws in

this theory of differentiation. Derivation of nephelite

basalt from the same monzonitic magma by differentiation might seem incompatible with the sodic character of the nephelite rock, but the close association

with the latites and monzonites favors this inference

rather than the assumption of an independent magma.

61 Bowen, N. L., The later stages of the evolution of the igneous

rocks: Jour. Geology, vol. 23, No.8, supplement, 1915; The reaction

principle in petrogenesis: Jour. Geology, vol. 30, pp. 177-1\l8, 1\ll!2;

Origin of ultrahasic and related rocks: Am. Jour. Scl., 5th ser., vol. 14,

pp. 89-108, 1927. Summarized in Bowen, N. L., The evolution of the

igneous rocks, pp. 92-124, Princeton, N. J., 1928.

6' Daly, R. A., Igneous rocks and their origin, p. 229, New York, 1914.

Quite as noteworthy as the parallelism between the

igneous history of Park City, Tintic, Marysvale, San

Francisco, and possibly Iron Springs and that of the

Stockton and Fairfield quadrangles is the striking

similarity in composition of the igneous rocks of these

localities. The igneous rocks of Gold Hill, Utah, are

also very similar. This is clear from the following

tables of partial analyses:

Partial analyses of intrusive rocks of western Utah and

eastern Nevada

Si02_ - - - - - - - -- CaO _

~:o~= = = = = = = = = =,

58. 64

5. 37

3. 60

4. 23

2 i

~7. 16-1

5.86 II 3. 82

4.49

I

59. 35

5. 03

3.73 i

3.85 I

I

I

63. 46 I 59. 68

4.33 i 4.63

3.661' 3.96

3.49 2.92

Si O2_

CaO _

Na20 __----- _

K20 --- _

61. 64

4. 65

2.71

3. 07

64. 00

2.95

3.55

5. 45

59. 76

3. 88

3.01

4. 40

62. 10

5.31

5.56

3.15 I

I

66.05

3. 93

3.60

4. 04

64.41 I

3.71

3.60 !

3.46 [

I 65.29 63.63

4.85 4.46

2. 10 1. 70

5.18 5.22

---------------

14 I 15

!

70.67 \

1.71 ,

3.95 \ 4.85

62. 84

4.72

2. 85

4.60

55. 251--~9.-4;

7.19 I 6.24

3.48

1

2.98

4. 11 1. 93

,

-------------

66.64

3. 50

3.41

3. 72

65. 10

4. 66

3.82

2. 29

1. Monzonite, British tunnel, Bingham. E. T. Allen, analyst.

Boutwell, J..M., and Keith, Arthur, Economic geology of the

Bingham mining district, Utah: U. S. Geol. Survey Prof. Paper

38, p. 178, 1905.

2. Monzonite, Tribune tunnel, Bingham. E. T. Allen, analyst.

Idem.

3. Quartz diorite, %, mile northeast of Clayton Peak, Park

City district, Utah. W. F. Hillebrand, analyst. Boutwell,

J. M., and Woolsey, L. H., Geology and ore deposits of the

Bark City district, Utah: U. S. GeoL Survey Prof. Paper 77,

p. 79, 1912.

4. Quartz diorite, east side of Brighton Gap, Park City district, Utah. W. F. Hillebrand, analyst. Idem.

5. Quartz diorite porphyry dike northwest of Daly West

shaft, Park City district, Utah. W. F. Hillebrand, analyst.

Idem, p. 84.

6. Quartz diorite porphyry, Valeo mine, Cottonwood Canyon,

Park City district, Utah. \V. F. Hillebrand, analyst. Idem.

7. Monzonite near Iron Dike mine, east of Silver City, Tintic mining district, Utah. H. N. Stokes, analyst. Tower,

G. W., jr., and Smith, G. 0., U. S. Geol. Survey Nineteenth

Ann. Rept., pt. 3, p. 647, 1898.

1'1. Quartz monzonite, Cactus tunnel, San Francisco district,

Utah. George Steiger, analyst. Butler, B. S., Geology and

ore deposits of the San Francisco and adjacent districts, Utah:

U. S. Geol. Survey Prof. Paper 80, p. 55, 1913.

9. Quartz mOIlzonite, O. K. mine, Beaver Lake district, Utah.

R. C. Wells, analyst. Idem, p. 57.
10. Quartz monzonite, Beaver Harrison dump, Beaver Lake

district, Utah. R. C. Wells, analyst. Idem.

11. Quartz monzonite, Star district, Utah. R. C. Wells,

analyst. Idem, p. 59.

12. Fresh andesite, east of Granite Mountains, Iron Springs

district, Utah. R. D. Hall, analyst. Leith, C. K., and Harder,

E. C., The iron ores of the Iron Springs district, southern Utah:

U. S. Geol. Survey Bull. 338, p. 49, 1908.

13. Weathered andesite, Desert Mound, Iron Springs district, Utah. R. D. Hall, analyst. Idem.

14. Granodiorite, Ibapah stock, Deep Creek Range, Utah.

R. C. Wells, analyst. Butler, B. S., The ore deposits of Utah:

U. S. Geol. Survey Prof. Paper 111, p, 96, 1920.

15. Quartz monzonite, Clifton district, Deep Creek Range,

Utah. R. C. Wells, analyst. Idem.

16. Average post-Cambrian granite (Osann and Clarke).

Daly, R. A., Igneous rocks and their origin, p. 19, New York,

1914.

17. Average quartz monzonite (Clarke). Idem, p. 25.

18. Average granodiorite (Osann and Clarke). Idem.

19. Average monzonite (Osann and Washington). Idem,

p.23.

20. Average quartz diorite (Osann and Washington). Idem,

p.26.

In spite of the range in silica content (from 70.67to

57.16 per cent) shown by analyses 1 to 15, a range

which is reflected in the varying quartz content of the

rocks, it is clear that the proportions of CaO, Na20,

and K20 are all, except in the intrusives of the Iron

Springs district, much closer to those of the average

quartz monzonite than to those of any other of the

:,average rocks" given. The intrusive rocks of the

Iron Springs district were called andesites by Leith

and Harder, but it is clear that chemically they fall

far outside the permissible limits of the andesites.

They are a~suredly latitic or even rhyolitic rather than

andesitic. Butler 63 notes their strong resemblance to

the other late intrusive rocks in Utah.

The widespread regional similarity of the effusive

rocks is even more striking than that of the intrusive

rocks. The volcanic rocks of all these districts are

chiefly described as andesites and rhyolites, the former

predominating. The andesitic rocks have been so

named from their mineral composition. Wherever

chemical analyses are available, however, it is seen that

the so-called andesites are without exception so high

in potassa that they are more properly classed as

latites. Similarly, several so-called dacites resemble

quartz latite much more closely chemically. This is

apparent from the following table of the available

•

chemical analyses of the "andesites," dacites, and

latites of western Utah.

,

4 i I 6

---'---1--

59.86 54.23 i 53. 75

4. 62 6. 67 I 5. 95

3. 31 2. 96 I 3. 18

4. 84 2. 80 i 4. 13

SiD2 - __ - --

CaO _

Na20 -__

K20 - - - - - -

66. 90

2. 35

3. 34

3.75

65. 64

3. 26

3. 26

3.50

61. 09

4.70

3. 00

3. 77

'3 Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof.

Paper 111. p. 97, 1920.

Partial analyself 01' andesitio and latitio rocks of western

Utah--Continued

9 10 I 11 j 12

I I

,---~-_.- --I---I~~

I

SiD I 2___ - - - - - - 57.27 60.17 I

68. 04 67. 93 64. 48 63.04

CaO _________ 6.06 4.69 I 2. 76 1. 42

I

1. 95 4.13

Na20 __- - - - -- 2.94 2. 96 I 4. 06 3. 54 4.81 3. 43

K2O ___- _____ 3. 23 4.16 I 4.27 3.91 3.39 3. 26

I

--- -~_._-- ------- - ----_.----- -- ------- ---

--..:---1 13 I 14 15 16 17

I

Si02___________ 57.72 58. 04 61. 05 61. 52 57.94 CaO ___________ 6. 40 6.12 5. 40 5. 72 4.91

Na20 __- - - - - - -- 4. 94 2.26 1. 43 2. 31 1. 29

K20_ - - - - - - - - -- 4.36 I 4. 08 5. 58 3. 02 8.90

!

1. Quartz latite, Tickville Spring, Fairfield quadrangle. J. G".

Fairchild, analyst.

2. Quartz latite, sec. 2, T. 5 S., R. 2 W., Fairfield quadrangle.

J. G. Fairchild, analyst.

3. Quartz-bearing latite, Oak Spring Canyon, Fairfield quadrangle. J. G. Fairchild, analyst.

4. Hypersthene-augite latite, sec. 8, T. 4 S., R. 2 W., Fairfield

quadrangle. J. G. Fairchild, analyst.

5. Andesite, Ontario tunnel, Park City district. W. F.

Hillebrand, analyst. Boutwell, J. M., and Woolsey, L. H.,

U. S. Geol. Survey Prof. Paper 77, p. 74, 1912.

6. Augite latite, Volcano Ridge, Tintic district. George

Steiger, analyst. Lindgren, Waldemar, and LougWin, G. F.,

U. S. Geol. Survey Prof. Paper 107, p. 56, 1919.

7. Hornblende-augite latite, Tintic district. George Steiger,

analyst. Idem, p. 63.

8. Latite, Tintic Mountain, Tintic district. H. N. Stokes,

analyst. Idem, p. 69.

9. Quartz latite, Squaw Springs, San Francisco district.

George Steiger, analyst. Butler, B. S., U. S. Geol. Survey

Prof. Paper 80, p. 47, 1913.

10. Soda rhyolite, San Francisco district. George Steiger,

analyst. Idem, p. 48.

11. Dacite, 0. K. mine, San Francisco district. R. C. Wells,

analyst. Idem, p. 48.

12. Dacite, San Francisco district. George Steiger, analyst.

Idem, p. 46.

13. Latite or andesite, San Francisco. R. C. Wells, analyst.

Idem, p. 47.

14. Andesite, Antelope Range, Iron Springs district. R. D.

Hall, analyst. Leith, C. K., and Harder, E. C., U. S. Geol.

Survey Bull. 338, p. 58, 1908. "

15. Dacite, Sweet Hills, Iron Springs district. R. D. Hall,

analyst. Idem.

16. Hypersthene-augite latite, Deep Creek. J. G. Fairchild,

analyst. Nolan, T. B., Geology and ore deposits of the Gold Hill

quadrangle, Utah: U. S. Geol. Survey report (in preparation).

17. Biotite-augite latite, Deep Creek. J. G. Fairchild,

analyst. Idem.

Of these rocks, only the andesite of the Park City

district and the dacites of the San Francisco district

carry more soda than potassa, and even these are much

higher in potassa than the average andesite and dacite

as calculated by Daly. This widespread similarity in

the chemistry of the igneous rocks of western Utah

must reflect a regional magmatic character. However, it is impossible in the present state of our petrologic knowledge to be certain whether this is due to a

widespread peculiarity of the original subcrustal

magma or merely to a widespread similarity in the

conditions before intrusion, such that the courses of

differentiation of the several offshoots of the primary

magma have been parallel. Much more information
about the regional geology and the igneous history

will be needed before an attack on this problem can

be hopefully made.

The numerous points of uncertainty regarding the

igneous geology of the Stockton and Fairfield quadrangles have been set forth above. However, despite

the unsatisfactory status of information on these

pomts, the following summary of the igneous history

seems to be permitted by the known facts.

Probably in late Eocene or Oligocene time the maturely dissected surface of the northern part of the

Fairfield quadrangle and probably also of the Stockton quadrangle was covered by volcanic materials.

The nature of the earliest eruptions in the area is unknown. Among the oldest volcanic rocks remaining,

however, are remnants of rhyolite obsidian flows and

breccias containing fragments of latite, trachyte, and

basalt, indicating a somewhat complex history of volcanism. This early phase, of fragmentary record, was

followed by the formation of latitic pyroclastic rocks

and latite and quartz latite flows. Some nephelite

basalt dikes were also injected.

Contemporaneously with the superficial eruptions,

magma was injected at depth in the form of stocks,

sills, and possibly laccoliths, some of which extended

up into the base of the pyroclastic series. It is probable that the latitic volcanic necks were fed by these

or connected magma chambers. The volcanic rocks

were then, in the closing stages of activity, penetrated

by rhyolite dikes and plugs. The lamprophyres presumably were among the last products of the volcanism, which probably ended with minor basaltic effusions. It may be, however, that the basalts were much

later and only remotely connected with the principal

volcanic cycle.

STRUCTUR'E

GENERAL FEATURES

The chief structural features of the Stockton and

Fairfield quadrangles include folds, faults, fissures,

and the features related to igneous emplacement. The

structural relations of the igneous rocks have been set

forth in the preceding section; fissures to which ore

deposition is known to be related will be treated in

the section dealing with the ore bodies. It remains to

describe the more general structural features, folding

and faulting.

The southern Oquirrh Mountains and South Mountain, which together constitute about half of the Stockton and Fairfield quadrangles, consist for the most

part of simple foMs of large dimensions. Later volcanic deposits mask the sediments near the northeast

corner of the area, and huge aprons of alluvium conceal the bedrock beneath Rush, Tooele, Cedar, and

Salt Lake Valleys, but there is no reason to doubt that

these portions of the area are likewise underlain by

simply folded Paleozoic rocks, in attitudes analogous

to those so well exposed in the uplands. The Oquirrh

Mountains are bounded on the west by a series of

faults in steplike arrangement. These faults sharply

truncate the folds at varying angles, and to displacement along them is primarily due the existence of the

range as a topographic feature. Other faults of great

economic importance occur within the body of the

range, but in general faulting, save for the mountain-

:front faults just mentioned, has been subordinate to

folding throughout the area.

FOLDS

The strata composing the southern part of the

Oquirrh Mountains are thrown into four large folds,

two anticlines and two synclines, which are the dominating structural features of the Stockton and Fairfield quadrangles .. These folds are subparallel, with

northwest trends, thus making considerable angles

with the crest and borders of the mountains. The axis

of a transverse uplift crosses the range practically at

a right angle to the trend of these major folds, and

from this cross axis the folds plunge both north and

south.

The axis of"the western anticline of the range, long

known as the Ophir anticline, passes just west of the

abandoned site of Sunshine, thence northwestward:

about a mile west of Mercur, through Lion Hill (pI. 3,

B), Ophir, and, farther northwest, through the Queen

of the Hills mine in Dry Canyon and is interrupted

just south of Soldier Creek by the zone of en echelon

faults that limits the range on the west. A fold that

is almost certainly the continuation of the Ophir anticline appears in South Mountain, across Rush Valley

from this point.

In Ophir Canyon the Ophir anticline is cut by

an eastward-trending zone of branching faults whose

combined effect is a vertical displacement of the

beds in excess of 2,000 feet. Just north of the fault, on

the upthrown side, the oldest exposed rocks in the area

are to be seen. A little farther north the anticline

plunges steeply, so that the entire stratigraphic column

up to and including the "Great Blue" limestone is

traversed in following the axis northward before it is

cut off by the mountain-front fault near Soldier Creek.

In South Mountain the axis swings sharply to a more

westerly trend than it has in the main range. The

rocks composing South Mountain, with the exception

of some altogether insignificant sills, belong entirely

to the Oquirrh formation, indicating that the axis of
the fold has continued to plunge throughout its course

north of Ophir Canyon.

To the south of Ophir Canyon the anticline plunges

much more gently than it does to the north, but as the

altitude also declines from Lion Hill southward, approximately the same geologic horizons are exposed

well down the range. Silverado Canyon exposes the

Humbug formation, and Mercur Canyon cuts slightly

lower, penetrating the upper part of the Deseret limestone, but farther south no rocks are exposed older

than the Humbug formation, which is to be seen in

McFait and Mitchell Canyons. The" Great Blue"

limestone is the surface formation over the entire anticline west of Manning Canyon and south of Soldier

Creek except for the small areas of older beds exposed

ill the canyons just mentioned.

Throughout its exposed length the Ophir anticline

is asymmetric, but whereas toward the south it is only

slightly steeper on its eastern flank than on its western,

the dips half a mile from the axis being about 25° to

40° and 10° to 25°, respectively, the asymmetry becomes more marked farther northwest. At the east

end of South Mountain the northeast limb of the fold

is vertical but the southwest limb dips only about 30° ;

2 miles farther west the north limb is overturned and

dips as much as 55° S., but the southern limb maintains its 30° west dip and north-south strike rather

constantly.

POLE CANYON SYNCLINE

Bordering the Ophir anticline on the east is the

Pole Canyon syncline, an open fold whose axis passes

through Pole Canyon, trending parallel to that stream,

and thence slightly west of north through the highest

peak of the area, the 10,626-foot eminence about a

mile north of LewistDn Peak. The axis trends northnorthwestward from this peak and passes near the

southwest corner of T. 4 S., R. 3 W., whence, curving

slightly toward the west, it passes down Selkirk

Canyon and is concealed beneath alluvium.

Throughout its course the west limb of this syncline

is steeper than the east, the relations being complementary to those shown by the Ophir anticline and

Long Ridge anticline. Like the Ophir anticline also,

the syncline plunges both south and north from a

point near the latitude of Ophir, more steeply toward

the south and less steeply toward the north almost to

Selkirk Canyon, where the axis pitches more steeply

again. Despite this plunging and the great thickness

of strata thereby exposed, the surface formation

throughout the syncline is the Oquirrh formation

LONG RIDGE ANTICLINE

East of and subparallel to the Pole Canyon syncline

is the Long Ridge anticline, so called because the axis

of the fold almost coincides with the axis of Long

Ridge. The axis of the fold trends northwestward

from Long Ridge (south of which it is concealed by

alluvium) through the head of Iron Canyon, passes

thence near the old Mayflower mine and across the

saddle between White Pine Flat and West Canyon,

and leaves the area at a point near the common north

corner of the Stockton and Fairfield quadrangles.

Like the Ophir anticline, the Long Ridge anticline

is decidedly asymmetric, the southeast flank dipping

much more gently than the northeast. This asymmetry is very marked near Middle Canyon, where the

northeast flank stands practically vertical or is even

overturned, whereas the southwest flank is characterized throughout by moderate dips.

From Long Ridge northward the axis of the fold

plunges toward the north, somewhat gently near Long

Ridge but more steeply beyond West Canyon. The

result of the fold and the plunge of its axis is the

exposure along it of the Humbug formation, "Great

Blue" limestone, Manning Canyon shale, and Oquirrh

formation in succession from southeast to northwest.

The corresponding downfold east of the Long Ridge

anticline is the southward continuation of the Bingham syncline,64 a structural feature named from the

Bingham mining district, which it dominates. Owing

to the volcanic cover of much of the northeastern part

of the Fairfield quadrangle, it is difficult to trace the

axis of this fold in detail; apparently, however, it

passes near the mouth of Oak Spring Canyon and

crosses the north edge of the quadrangle near the point

where Butterfield Canyon leaves the area. The portion of this fold within the Fairfield quadrangle is

not so markedly asymmetric as the Pole Canyon syncline. Both the limbs are very steep, in places even

overturned, but the trough of the syncline appears to

be very wide and open, as it is in the Bingham district,

to the north. The northward pitch of the fold that

characterizes it in the Bingham district is less steep in

this area, and, indeed, it appears to pitch to the south

near Oak Spring Canyon. In this respect the Bingham syncline resembles all the previously discussed

folds of the quadrangles, for the pitch in all decreases

toward a cross axis in an east-west line in about the

latitude of Ophir. 1£ the Bingham syncline can be

said to have a cross axis, that feature is probably

somewhat north of the common cross axis of the other

folds. A small outlier of the Lake Mountains in sec.

25, T. 5 S., R. 2 W., is a part of the east limb of the

fold. The axis of the fold seems almost level at this

64 Boutwell, J. M., and others, Economic geology of the Bingham mining district, Utah: U. S. Geo!. Survey Prof. Paper 38, p. 56, 1905.
point. The northern part at least of the Lake Mountains southeast of this area seems to be a part of the

fold. The Oquirrh formation is the only sedimentary

rock exposed in the Bingham syncline within the Fairfield quadrangle.

MINOR FOLDS

Just east of the Bingham syncline near the edge of

the Fairfield quadrangle there is a short segment of

an anticline, whose west limb is formed by the steeply

dipping east limb of the Bingham syncline. Exposures are very poor, and the diversely oriented joints

of the quartzites of the Oquirrh formation, which is

the only sedimentary rock exposed, render it almost

impossible (in the absence of limestones) to determine

accurately the attitude of the beds, so that the details

d the fold are not certainly established. Such information as was obtained, however, indicates that the

axis of the fold trends in a northwesterly direction,

passing a short distance east of the center of sec. 25.

T. 4 S., R. 2 W. Only about a mile of the length of

the anticline is exposed within the area, but the northeastern limb dips north at an angle of about 60°, indicating that the axis ad' this fold, like those previously

described, pitches northward. To the southeast the

fold passes out of the' quadrangles and constitutes

most of the small part of the Traverse Mountains not

included within the area.

Within the area of Rush Valley, near Morgan

Warm Spring, a group of low rounded mounds rise

I).hove the alluvium. These mounds consist of the

Oquirrh formation, dipping very steeply toward the

west. A few small foothills of the Stansbury Range

E:ncroachupon the Stockton quadrangle. Their structural relations are of little moment, as they occupy

f'0 small a part of the area and belong to the main

mass of the Stansbury Range rather than to the

Oquirrh Mountains.

The attitude of the beds within the quadrangles,

so far as it was determined, is shown on Plate 12, by

the customary structure symbo,'s. In the absence of

recognizable" marker beds" within the Oquirrh formation, it is not· profitable to attempt to show the

structural relations by contours.

REGIONAL RELATIONS OF THE FOLDING

The northwesterly trend of the folds in the Stockton and Fairfield quadrangles is roughly parallel to

that of the folds of the Tintic district 65 and Canyon Range,66to the south, and the folds in the southern part of the Wasatch Range.67

•• Lindgren, Waldemar, and Loughlin, G. F., op. cit., p. 21.

•• Loughlin, G. F., A reconnaissance in the Canyon Range, west·

central Utah: U. S. Geol. Survey Prof. Paper 90, pp. 53-58, 1914.

• 7 Emmons, S. F., U. S. Geol. Expl. 40th Par. Rept., vol. 2, pp. 34::l350, 1877.

Several overthrust faults are present in the Wasatch

Range, northeast of this area,68in the Cottonwood district. Overthrusts have also been reported by Loughlin 69 from the Mount Nebo region, at the south end

of the range, and by Blackwelder 70 from the vicinity

of Ogden, much farther north. All these thrusts

have northerly trends and reveal movements of the

overthrust block to the east relative to the underlying

block.

About 90 miles to the west, in the Deep Creek

Range, overthrusting in response to east-west compression has been recorded by Nolan. 7l

Butler 72has called attention to the general northsouth trend of the folds in western Utah, pointing out,

however, that many folds strike in directions ranging

from nearly northwest to considerably east of north.

This subparallelism of the folds over a considerable

region, combined with the notable thickness of the

stratigraphic column involved in the deformation,

leads to a postulate of regional pressure parallel to a

roughly east-west direction as a proximate cause of

the folding and thrust faulting. That this stress was

exerted principally along a northeast-southwest line

within the Stockton and Fairfield quadrangles seems

probable from the general trend of the local folds in

a direction normal to this. However, even within so

small an area as that of the Stockton and Fairfield

quadrangles this compressive force could not have

been uniform, either in direction or in intensity. In

fact, the more nearly east-west portions of the folds

exhibit decidedly more asymmetry and even overturning than the more nearly north-south portions. On

account of the large concealed areas beneath the valleys and the lack of sufficient detailed studies in the

other near-by ranges it would be premature to attempt an "explanation" of this relation. If one is

forthcoming it will be established only as a result of

much more work than has yet been done in the region.

SUPPOSED EXTENSION OF THE UINTA AXIS THROUGH

BINGHAM

Butler 73 in a discussion of the general structural

relations in Utah pointed to the region between Bingham and Park City as the extension of the axis of the

6. Hintze. F. F., A contribution to the geology of tbe Wasatch Mountains, Utah: New York Acad. Sci. Annals, vol. 23, p. 133, 1913. Loughlin, G. F., Reconnaissance in the Wasatch Mountains, Utah: Jour.

Geology, vol. 21, pp. 439-443, 1913. Calkins, F. C., in Butler, B. S.,

and others, The ore deposits of Utah: U. S. Geol. Survey Prof. Paper

Ill, pp. 245-247, 1920.

• 9 Loughlin, G. F., op. cit., p. 449.

76 Blackwelder, Eliot, New light on the geology of the Wasatch

Range: Geo!. Soc. America Bull., vol. 21, pp. 517-542, 1910.

71 Nolan, T. B., Geology and ore deposits of the Gold Hill quadrangle,

Utah: U. S. Geo!. Survey report (in preparation).

72 Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof .

Paper 111, pp. 100-105. 1920.

" Butler, B. S., op. cit. (Prof. Paper 111), pp. 100-105.
Uinta Mountain uplift and hinted that intrusion may

have been a factor in producing or at least in continuing such an uplift.

This suggestion has been accepted by Olmstead 74

and framed more specifically by Spurr,75 Porter,76 and

Beeson.77Spurr believes that he can recognize the extension of the Uinta axis westward through Park

City and Bingham, then with an offset to Tintic and

west through the Deep Creek Range into Nevada.

Porter,78 however, believes that the Uinta uplift passes

through the Bingham district, thence westward to the

Stansbury Range. He attributes the localization of

igneous activity and ore deposition principally to intersection of the traverse fractures of this system with

the longitudinal fractures of the Wasatch ~nd Oquirrh

Ranges. He offers no explanation of the absence of

igneous intrusions on the supposed extension of the

axis through the Stansbury Range. In his earlier

paper 79he expressed the opinion that the widening of

the Oquirrh Range in the latitude of Stockton and the

Traverse Mountains is due to cross fracturing (and

presumably to uplift) along the extended Uinta axis.

Beeson interprets the Uintlll Mountains as due to an

elongated laccolithic intrusion and believes that the

intrusive mass and the uplift accompanying it extend

westward through Park City, Big and Little Cottonwood Canyons, and the Bingham district. He states

definitely 80that a continuous" ore zone" accompanies

this uplift and that the mineralization was not confined to isolated cent~rs.

The formation of this great zone of fissuring and mineralization [the "Bingham-Park City ore zone"] is believed to

have been caused by the forces of mountain-making disturbances rather than the contraction stresses of the cooling

magma, because the fissured zone is more or less restricted to

an area about 2 miles wide and at least 40 miles long and

parallel to the Uinta axis. The zone extends between and

through the Bingham and Park City mining districts.8'

Beeson suggests also that the localization of the

zone of fissuring is due to its situation above the feeding dike of the supposed laccolith to which the roughly

east-west anticlinal structure is attributed.

Without going deeply into the highly speculative

Question of the origin of the Uinta uplift it may bl'

pointed out that no post-Cambrian igneous rock has

ever been found in the Uintlll Mountains themselves,

although fully 30,000 feet of strata have been removed

from the core by erosion and the base of the Cambrian

•• Olmstead, S. G., Economic geology of the Ophir mining district,

Utah: Econ. Geoiogy, vol. 16, p. 437, 1921.

75 Spurr, ;r. E., The ore magmas, vol. 2, pp. 475-485, New York, 1913.

76 Porter, C. A., Intersecting fracture zones and mineral districts:

Eng. and Min. ;rour.-Press, vol. 118, pp. 650-651, 1924.

77 Beeson, ;r. ;r., Mining 'districts and their relation to structural geoi.

ogy: Am. Inst. Min. and Met. Eng. Trans., vol. 75, pp. 768-792, 1927.

78 Porter, C. A., discussion of paper by Beeson: Idem, pp. 793-796.

'7ll Porter, C. A., op. cit. (1924), p. 650.

80 Beeson, ;r. ;r., op. cit., p. 778.

Bl Idem. jlp. 780-781.

where it unconformably overlies pre-Cambrian

gneisses has been exposed. Accordingly if there is

any intrusive mass present it is well down within the

pre-Cambrian. Also there is evidence that the mountain mass is decidedly overthrust to the north,S2which

lends little support to a laccolithic theory of origin

but seems to suggest tangential compression as a cause

of the folding.

There is little doubt that the igneous intrusions in

the Cottonwood and Park City districts have been

effective factors in the deformation of those districts,

and although they are crosscutting and can not be

called laccolithic in shape they are assuredly either

the causes or the accompaniments of a decided transverse upwarp which is doubtless correctly attributed

to a westward extension of the Uinta folding. However, the geologic mapping of the Bingham district 83

and of the Stockton and Fairfield quadrangles shows

definitely that far from being on an east-west or eastnortheast uplift, the Bingham stock of monzonite is

intruded in a deep downwarp of northwest trend. In

fact, rough computations from outcrop data show that

the base of the Ophir formation is probably not less

than 18,000 feet below sea level near the center of the

Bingham district, or fully 4 miles deeper than it is

beneath Long Ridge, 10 miles to the south, and nearly

5 miles deeper than at Ophir. If there is an east-west

uplift in the Oquirrh Mountains its axis must pass

only slightly north of east, more probably almost due

east, through the latitude of Ophir, thus being fully

10 miles south of the area of principal mineralization

of Bingham. It is true that there is evidence of the

existence of igneous material beneath the principal

transverse upwarp near Ophir, and in the opinion of

the writer the sharpness of the Ophir anticline at this

place may be due in part to the intrusive force, as

Butler first suggested.

The interpretation of the cross axis through Ophir

as the extension of the Uinta fold seems to the writer

only a little more plausible than the interpretation of

the pre-Cambrian areas of Farmington and Antelope

Island, 35 miles farther north, as th~ extension of this

axis. On the evidence at hand, the question of a westward extension of the Uinta axis beyond the Wasatch

Range seems an open one. In the opinion of the

writer there is doubt whether it continues at all,

though it is without question to be found in the

Cottonwood district .

82 Schultz, A. R., A geologic reconnaissance of the Uinta Mountains,

northern Utah, with special reference to phosphate: U. S. Geol. Survey Bull. 690, pp. 70-71, 1918; Oil possibilities in and around Baxter

Basin, Wyo. : U. S. Geol. Survey Bull. 702, p. 38, 1920. Reeside,;r. R.

jr., Notes on the geology of Green River Valley between Green River,

Wyo., and Green River, Utah: U. S. Geol. Survey Prof. Paper 132, fig.

5, p. 39, 1923. Irwin,;r. S., Faulting in the Rocky Mountain region:

Am. Assoc. Petroleum Geologists Bull" vol. 10, pp. 108-109, 1926.

88 Boutwell, J. M., and others, Economic geology of the Bingham

mining district, Utah: U. S. Geol. Survey Prof. Paper 38, pI. 1, 1905
Porter's assumption that the wide part of the

Oquirrh Mountains is associated with an extension of

the Uinta axis is likewise not supported by field evidence. This wide place is purely an accident of topography due to late Tertiary faulting and has no relation

to the early Tertiary folding and intrusion. The only

east-west fold on this line is South Mountain, and it is

8ufficiently apparent that this is merely the curved

extension of the Ophir anticline.

Spurr's generalization deals with units far beyond

the scale of the present paper, but in so far as the disproof of an anticlinal location of the Bingham district

intrusive throws doubt on its association with the

Uinta anticline his generalization likewise must be

questioned. As to any offset of the Uinta axis from

Bingham to Tintic, there is no evidence of the presence

of such an axis at Bingham nor of any faulting of

sufficient horizontal displacement to account for such

a lateral shift of 40 miles, and the areal geology

renders such a speculation of doubtful validity.

In summarizing the regional structure it may be

said that the Stockton-Fairfield area contains northward and ndrthwestward trending folds reflecting

compressive forces operating parallel to east-west or

northeast-southwest directions, presumably associated

in origin with similarly trending folds and overthrust

faults of neighboring ranges. The supposed extension of the Uinta anticline to the west through Bingham and its superposition upon the folds of northward trend is definitely not a fact, and it remains

questionable whether or not the nearly east-west cross

axis through Ophir is a reflection of the north-south

compression to which the Uinta fold most probably

owes its origin. The association of the intrusive of

the Bingham district with a very deep syncline is in

marked contrast to the anticlinal location of the Cottonwood and Park City stocks, and there is therefore

no consistent evidence to support the suggestion that

the Uinta uplift is due mainly to igneous intrusion.

The existence of igneous rocks from Mercur on the

south through Ophir, Soldier Canyon, the Stockton

district, and Bingham on the north renders an eastwest trend of intrusions in the Oquirrh Range a matter of some doubt also.

The information obtainable within these quadrangles sufficesmerely to place the date of the folding

as post-Pennsylvanian and earlier than Lake Bonneville Pleistocene. However, the subparallelism of the

folds and overthrusts over a much wider region justifies an assumption of approximate contemporaneity of

folding throughout the region, and evidence of the

date of deformation in neighboring areas is to this

extent applicable to determining the date of the local

folding. In the Tintic district 84 and the Wasatch

Range 85 the Eocene conglomerates rest unconformably

upon the eroded surfaces of these folds, fixing their

age as greater than that of the Wasatch Eocene.

Upper Cretaceous rocks are involved in the folding

of the Wasatch Range, and according to Veatch 86the

major unconformity of the Cretaceous-Tertiary part

of the section occurs between the Adaville (Upper

Cretaceous) and the Evanston formations. The

:Evanston is pre-Wasatch in age and conformably overlain by the lower formations of the Wasatch group.

though separated from the upper Wasatch by another

though probably less pronounced unconformity. The

presumption of a late Cretaceous to very early Tertiary

date of the folding in the Wasatch Range seems well

established, and accordingly this is the most likely

clate of the folding in the Oquirrh Mountains. How-

('vel', the work of Veatch in southwestern Wyoming

and of White,87 Gale,88and Sears 89in northwestern

Colorado and the general summary of the whole problem of the deformation of the Rocky Mountain region

or Idaho, Utah, and Wyoming given by Mansfield 110

show that compression and folding recurred during a

considerable period in the general region of which this

is a part and that a definite and precise date can not

ue established for the principal deformation of the

Oquirrh Mountains. Probably most of the folding of

this part of the Rocky Mountains occurred before Fort

Union time, but that can not be proved locally.

Hintze,91 Calkins,92and Beeson 93have pointed out

the significant fact that the overthrusts of the Cottonwood area are involved in the folding of the Uinta

Mountains, showing at least a slight difference in age

uetween the north-south folds and overthrust of the

Wasatch Range and the east-west fold of the Uinta.

In the opinion of the writer there is no evidence within

the southern half of the Oquirrh Mountains that the

later movement (the Uinta folding) found expression

in this area. Thus the probabilities point to late

Cretaceous or very early Eocene time for the Oquirrh

folding.

84 Loughlin, G. E., op. cit. (Prof. Paper 107), pp. 103-104. .5 Emmons, s. F., The Wasatch Range: U. S. Geo!. Expl. 40th Par.

Rept., vo!. 2, pp. 381-383, 1877. Wegemann, C. H., The Coalville coal

field, Utah: U. S. Geo1,Survey Bull. 581, pp. 161-184, 1915.

• 6 Veatch, A. C., Geography and geology of a portion of southwestern

Wyoming: U. S. Geo!. Survey Prof. Paper 56, pp. 76-87, 1907.

• 7 White, C. A., in Hayden, E. V., U. S. Geo1,and Geog. Survey Terr.

Eleveuth Ann. Rept., pt. 1, pp. 227-229, 1877.

ssGale, H. S., Coal fields of northwestern Colorado and northeastern

Utah: U. S. Geo!. Survey Bull. 415, pp. 75-94, 1910.

.0 Sears, J. D., Geology and oil and gas prospects of part of Moffat

County, Colo., and southern Sweetwater County, Wyo.: U. S. Geo1,

Survey Bull. 751, PP. 291-293, 1924.

soMansfield, G. R., Geography, geology, and mineral resources of part

of southeastern Idaho: U. S. Geo1, Survey Prof. Paper 152, pp. 379-

384, 1927.

01 Hintze, E. E., jr .. op. cit., p. 128.

02 Calkins, E. C., in Butler, B. S., and others, The ore deposits of

Utah: U. S. Geo1, Survey Prof. Paper 111, p. 254.

o. Beeson, J. J., op. cit., p. 779.
The larger faults of the Stockton and Fairfield quadrangles fall into four principal groups. A group of

major economic importance, because the faults displace

the strata in which were found the Ophir Hill ore

bodies, has its center in Ophir Canyon. Inasmuch as

the faulted area extends to Silverado Canyon on the

south, the faults will be collectively called the OphirSilverado fault group. The principal faults, both in

magnitude and in economic importance, are those of

Ophir Canyon. A second group of faults, possibly related to the Ophir-Silverado group but conveniently

treated separately, is of less structural effect but of considerable economic interest. This group will be called

the Dry Canyon fault group, as it centers in Dry

Canyon near the Mono mine. Another principal

group is the zone of en echelon faults which trend

somewhat west of north along the west front of the

mountain range and to whose displacements the existence of the range is due. This is a typical" Basin

Range" fault system that has produced striking physiographic and structural effects. The fourth principal group is found in the mining area near Stockton

and consists of numerous subparallel, westward-dipping normal faults. It is barely possible that this

system is a part of the Basin Range system, but the

faults are not topographically expressed and are, therefore, presumably of greater age; for this reason they

will be considered separately. This group is of very

great economic importance, the Stockton ores being

genetically associated with it. Obscure bedding faults

are numerous in this district also, but it is thought

that they are principally connected with the folds,

althouah some later movement has taken place along b

them.

Evidences of faulting are common at many other

places throughout the quadrangles, but for lack of

"marker beds" few of the faults could be mapped in

any systematic way. Evidence is lacking, however,

to show that any of them are of either economic or

structural importance.

OPHIR-SILVERADO FAULT AREA

CANYON FAULT

Of the faults centering in Ophir Canyon the one

of grel,ltest magnitude and of principal economic interest is that locally called the Canyon fault. The

Canyon fault is not a simple fracture but consists

over most of its traceable outcrop of 'several faults,

which coalesce and redivide at many places. The westernmost exposures of the Canyon fault are about a

mile due north of the Ophir Canyon cemetery, where

the great Lakes of Killarney fault of the Basin Range

system transects the branches of the Canyon fault.

These branches are both conspicuous because of the

brecciated limestone associated with them. Their

combined stratigraphic displacement is clearly in excess of 1,200 feet and probably is close to -1,500 feet,

as the beds south of the fault are dropped relatively

to those on the north, so that the base of the " Great

Blue" limestone is almost opposite the base of the

Madison limestone. The fault can be traced eastward,

the branches rejoining, and can be followed up the

gulch that descends the southwest flank of Dry Mountain. The displacement is here somewhat greater than

at the more westerly locality, but probably does not

exceed 2,000 feet. From this point eastward the fault,

though of varying displacement, is increasingly conspicuous, both because of the contrast in the beds it has

brought together and because of the more notable

breccia associated with it.

The dip of the fault, which averages perhaps

60°-65° S., causes its outcrop to descend the southward-facing gulches of the tributaries to Ophir

Canyon and to ascend the interstream spurs, so that

its trace on the surfa·ce is considerably more sinuous

than the actual fault surface.

The' fault has several branches where it crops out

in Bowman Gulch, and on the spur on which is situated the Ophir Hill Consolidated mill the fault movement is seen to have occurred on at least five distinct

fractures. Of these fractures the northernmost one

has by far the greatest displacement-about 1,400 feet.

The total stratigraphic displacement of this fault zone

south of the old Ophir Hill mine is more than 1,800

feet and is distributed on the major fault just mentioned and on four small faults south of it. These

small faults, in order from north to south, have

throws of approximately 160, 190, 160, and 30 feet,

and it is probable that still another small fault exists

beneath the alluvium of Ophir Creek. The large

cumulative effect of all these faults is seen from the

Tact that beds somewhat above the base of the Lynch

dolomite on the south side of the creek stand opposite

to the Tintic quartzite on the north side.

The displacement of this fault zone is almost surely

not all in a vertical sense, for the axis of the Ophir

anticline is offset along it for fully 1,200 feet, possibly

somewhat more, the south side having moved relatively

eastward. If the small dike of lamprophyre below the

abandoned· shaft of the Ophir Coalition mine, on the

north side of the canyon, is considered the offset extension of the dike just above the portal of the new

tunnel of the Ophir Hill Consolidated Mining Co., on

the south side of the canyon, the shift is 750 to 800

feet. Indeed, it is this lateral component of movement

which is in a measure responsible for the variations in

throw of the Canyon fault from place to place. Meas-
ured in a plane normal to the fault, the total throw is

more than 1,800 feet at the old adit of the Ophir Hill

mine, but opposite the new adit it is only a little over

1,000 feet, and still farther up the canyon, north of the

grand stand at the baseball grounds, it is only about

600 feet. The first two localities are only about a

quarter of a mile apart, and although it is believed

that the absolute displacement must decrease somewhat in this distance, it seems most probable that this

great difference in throw is due in large measure to the

lateral component of the fault movement.

Practically all the subsidiary faults of this major

zone trend about N. 70° E. and dip south at angles

from 60° to nearly vertical. North of the Ophir Cen~

tralshaft, however, a branch of more northerly trend

splits off and passes up the spur east of Hartmann

Gulch, at the crest of which its throw is about 100 feet

measured by the displacement of the base of the Madi-.

son limestone. This branch fault could be traced little

farther, as its displacement diminishes rapidly in this

direction, and Madison limestone forms both walls, so

that no distinctive horizons are available from which

to determine the displacement.

East of the Ophir Central shaft the spur is cut by

four other recognizable faults of the Canyon system,

whose displacement is very difficult to determine exactly because of the variability in the lithology of the

base of the Lynch dolomite, upon the dislocation of

which the determination must depend. However,

these faults, in order from north to south, including

the more northward-trending branch just mentioned,

appear to have throws of about 360, 90, 30, 130, and

380 feet. Still another fault of small throw, probably

less than 30 feet, must exist beneath the alluvium of

Ophir Creek at this place, for a distinct ledge of

siliceous dolomite is identifiable on both sides of the

creek, and a small fault must be inferred to explain its

difference in altitude.

For a few hundred feet between the Ophir Coalition shaft and the baseball grounds, farther northeast,

only two principal branches of the Canyon fault were

clearly identified, but there are three just north of the

baseball grounds. The two northerly ones are the

larger, and their combined throws are close to 600

feet where they displace the base of the Madison limestone. A short distance farther northeast the fault

traces descend into the valley alluvium and can no

10nO'er be followed. Doubtless, however, the fault

bec~mes identified with the northeastward-trending

Lion Hill fault, continuing at least 2 miles farther up

Ophir Canyon.

Throughout most of their courses the several

branches of the Canyon fault are marked by calcite.-

cemented breccia, but in places this is manganiferous

calcite, and some pyritic quartz fillings occur in some

of the branches above the Ophir Hill mill.

The Cliff fault is presumably a branch of the Canyon fault, for, although the possible junction of the

two is concealed, the Cliff fault can be traced within

about 200 feet of the Canyon fault, and the course is

such that they are almost surely joined beneath a talus

slope in the gulch southeast from Dry Mountain.

The general course of the Cliff fault on the spur

west of the old Montana mine is N. 55° E., and its

average dip is about 55° SE. On this spur the throw

of the fault, as determined from the displacement of

the hornfels at the base of the Bowman limestone, is

about 140 feet, although the exposures are not as complete as could be wished, and the error in this measurement may be as much as 25 feet. The next exposure of the fault trace is west of the old Montana

shaft in Bowman Gulch, where a breccia band and a

zone of steep dips in the lower part of the Hartmann

limestone afford evidence of the location. In the

workings of the Ophir Hill mine the fault has been

well exposed during the mining operations. Here it

is composed of as many as five branches, which separate horses of the Ophir formation and strike between

N. 15° E. and N. 45° E., averaging perhaps N. 25° E.

The total throw of the faults composing the zone, as

determined from measurements on the drain-tunnel

level of the mine, is close to 270 feet.

Talus and brush make it difficult to trace the fault

outcrop from the Montana shaft to the gulch just

below the lowest tunnel of the Cliff mine. Here a

small branch about 200 feet southeast of the main fault

displaces the hornfels at the base of the Bowman limestone about 40 feet. The principal fault has a throw

here of somewhat more than 300 feet. Slide rock conceals the fault for considerable distances up the hill

from the lower tunnel of the Cliff mine, which is

driven along the fault zone, but at the middle and

upper tunnels there are good exposures. At both these

places the fault is composed of several branches. It

can be traced still higher up the hill and to a small

saddle just west of the 9,450-foot hill south of Sharp

Mountain, but soil and talus prevent further tracing,

and it seems prol;>ablethat the fault must die out

within a short distance farther northeast.

The economic importance of the Cliff fault is very

great, and in the discussion of the Ophir Hill and Cliff

mines it will be necessary to consider the underground

relations in some detail.

Another fault whose structural effect is equal to that

of the Canyon fault is found in the north face of Lion

Hill, south of Ophir Canyon. The most westerly exposure of this fault is a brecciated and calcite-cemented

mass of limestone about 100 yards south of the railroad

crossing and a mile east of the power house in Ophir
Canyon. A short distance west of this locality it is

doubtless intersected by the Lakes of Killarney fault

of the Basin Range system, though the crossing is concealed by talus. At the westernmost exposure the

lower part of the" Great Blue" limestone south of the

fault is brought opposite the middle of the Humbug

formation on the north, a stratigraphic displacement

of roughly 600 feet. Half a mile to the northeast the

basal shale of the Deseret limestone north of the fault

abuts against beds near the middle of the Humbug

formation on the south, making the throw at this point

about 900to 1,000feet. A small prospect hole dug on

the fault furnishes an excellent exposure of it, from

which it can be seen to be normal with a dip of 60°-

68° S. It is marked by conspicuous breccias, cemented

with quartz and to a less degree with calcite and

carrying sufficient pyrite to produce a marked iron

stain on weathering.

A short distance farther northeast along the fault

there is a subordinate £ault of flatter dip to the north

of it. The trace of this fault joins the Lion Hill fault

again half a mile farther northeast, including between

it and the. main fault a horse of Madison limestone.

At the east end of this horse, due south of the Ophir

schoolhouse, the fault has dropped the lower part of

the Humbug formation against beds high in the Lynch

dolomite. The exact throw there was not determined,

but it is close to the aggregate thickness of the Madison

and Deseret limestones, about 1,100 feet.

A little farther northeast a slice of Madison limestone similar to the horse just mentioned lies north of

the fault and can be traced down the flank of Lion

Hill into the bottom of Long Trail Gulch. The fault

bounding this slice on the north is clearly seen on the

spur followed by meridian 112° 15' on the north slope

of Lion Hill. Here the fault strikes N. 45° E. and

dips about 62° SE., but the main Lion Hill fault, on

the south side of the slice, strikes about N. 60° E. and

dips somewhat more steeply. The included block of

Madison limestone has been strongly rotated, striking

N. 25° E. and dipping 38° SE.

The south fault passes south of the small 7,150-foot

knoll east of Long Trail Gulch, through the saddle

just west of the sharp curve in the wagon road from

Ophir to the Three Metals tunnel, and down the northwestward-facing slope into the bottom of Ophir Canyon, which it reaches, as nearly as could be determined

from the few exposures seen through the brush and

talus cover, about at the northeast end of the baseball

grounds. The north fault bounding the horse becomes

less pronounced toward the northeast, passes north of

the 7,150-foot knoll, and can be traced with great difficulty, because of brush and talus, for a short distance

farther down the hill toward the canyon bottom.

Here the alluvium of Ophir Creek conceals the relations of the faults of the Lion Hill group and those of

the Canyon group, but as their trends are so nearly

parallel it seems probable that the faults that can be

traced up the hill east of the Jim Fisk mine and for a

long distance farther up Ophir Canyon represent the

union of the two groups. South of the Jim Fisk mine

the combined throw of the faults seen and those which

must exist beneath the alluvium is not far short of

2,000 feet.

East of the Jim Fisk mine the fault can be traced

with some difficulty because of the thick brush cover

and the large quantity of talus, but at least one branch

passes across the nose of the hill northwest of the

creek, about 400 feet above the creek bottom. The

base of the Humbug formation on the north side of

this branch is brought opposite to the top of that formation on the south side, so that the throw is about

.650 feet. It seems necessary to infer a parallel fault

in the creek bed in order to account for the much

greater displacement of the beds south of the canyon

with respect to those on the north side. From a point

a few hundred feet farther northeast the fault sends

off two small branches to the north. These branches

are strongly marked by breccias but apparently are of

slight throw. From this point the main fault curves

more to the east. About 1,000 feet northeast of the

junction of Ophir Creek and its principal southern

tributary a fault of this system is clearly seen on a

spur in the north wall of the canyon, where a wide

breccia zone and marked drag in the limestone beds

give evidence of its presence. From this point northeastward no breccia zone is seen, the fault trace dropping beneath the valley alluvium, but at two points

somewhat farther upstream the limestones just north

of the valley alluvium show abnormally steep dips toward the southeast, and it is evident from the offset of

the Manning Canyon shale thatJ the fault continues

for some distance farther. The offset of the Manning

Canyon shale due to the fault along the valley of

Ophir Creek is about 1,000 feet, corresponding to a

throw of practically an equal amount, as the dips on

both sides of the fault approximate 45°.

Two minor faults parallel to the Canyon £ault

occur on the hillside southwest of the westernmost

outcrop of the Ophir formation. One of these displaces the beds downward on the north rather than

on the south, like the Canyon fault. These faults in

conjunction with a small northward-trending break

result in dropping a slice of the Madison limestone

down into the Jefferson (1) dolomite outcrop, but the

throw is slight. Similar small faults are common

throughout the quadrangles, but most of them are too

small to appear on maps of the scale of Plate 12.
A minor fault occurs in a tributary gulch that joins

Silverado Canyon from the north at the 6,500-foot

contour. This fault, which is cut off at its west end

by a small northwestward-trending fault whose relations are very obscure, begins with a small displacement about a quarter of a mile from Silverado Creek

and runs up the western spur of Chloride Point, passing over the shoulder of the spur at about the 7,950-

foot contour. Thence it can be traced with great difficulty perhaps 1,500 feet farther on the northwest

slope of Chloride Point, but its exact location is almost

impossible to determine because of the very poor exposures, and the fault either dies out or is concealed

east of a point north of the top of Chloride Point.

The fault is normal, and its displacement is probably

inconsiderable at both the west and east ends, but on

the northwest spur of Chloride Point beds about 200

feet above the base of the" Great Blue" limestone on

the north are dropped opposite beds possibly 300 feet

below the top of the Humbug formation on the south,

a movement of 500 feet or possibly somewhat less.

A similar normal fault on which the relative disc

placement has been down on the north crosses Silverado

Canyon close to the 6,800-foot contour. Southwest of

this point it passes up the west spur of Rover Hill

and drops into the next gulch to the west, where it is

cut off by one of the faults of the Basin Range system. It offsets the contact between the Humbug formation and "Great Blue" limestone nearly half a

mile horizontally and must have a throw of close to

600 feet, slightly less than the total thickness of the

Humbug formation. Northeastward the fault is traceable up the southwest slope of Chloride Point for

about a quarter of a mile and then along the slope,

parallel to Silverado Canyon, for about 1,000 feet. Its

displacement diminishes rapidly throughout this

course, and it finally becomes no longer traceable in

the brush and talus a little west of south of Chloride

Point. Its associated breccias are cemented by calcite

and silica.

Faulting of complex nature is indicated in the foothills between Ophir and Silverado Canyons, especially

in the valley tributary to Silverado Canyon near the

6,250-foot contour. Evidence for the faulting includes

steeply dragged blocks of limestone along strongly

brecciated zones, cemented with calcite and silica; its

complexity is indicated by the divergent traces of the

individual breccia zones and the evident and numerous local variations in strike and dip of the limestones

adjoining them. However, the only formation represented in this locality is the thick" Great Blue" limestone, which is practically devoid of traceable marker

beds, and no data were obtained that could be used

to determine the amount of displacement on the faults.

.The crescep.t-shaped hill whose summit reaches an altitude of 6,800 feet in the divide between Ophir and

Silverado Creeks is much cut by these faults, of which

only a few of the most conspicuous were traced and

are indicated on the accompanying map.

Evidences of a fault of uncertain but prebably

slight displacement are to be seen in the saddle between Sharp Mountain and the 8,757-foot hill about

a mile southeast of it. Brush and slide rock prevent

tracing of the fault, but its trend is such as to fall in

line with the offset of the Manning Canyon shale across

the next gulch to the east, and presumably that displacement is due to the same fault. Poor exposures

near the Manning Canyon shale outcrop and the lack

of other marker beds stratigraphically near it prevent

accurate delineation of the fault and interpretation of

its relations. It appears to be unimportant either

structurally or economically.

Three lines of evidence show that the faults of this

group are of greater age than the principal movements

of the Basin Range fault system.

1. There is no direct topographic expression of any

of the faults of the Ophir-Silverado group, and the

late-mature topography which extends from the south

end of the range to Lion Hill and probably to Bald

Mountain shows no displacement comparable to the

movement of roughly 3,000 feet due to the Canyon and

Lion Hill faults together. This topographic surface

has been displaced by the movement of the Basin

Range faults. (See pp. 81-86.)

2. The Canyon fault and its supposed branch, the

Cliff fault, are both mineralized, and there is no evidence of any notable postmineral movement on them.

Accordingly the faults of the Ophir Canyon group

were in existence before the cessation of the deepseated igneous activity which was the presumable

source of the ore of the district. This activity was

definitely earlier than the present topographic cycle,

which was initiated by the Basin Range faulting.

3. Perhaps the most convincing evidence of the

antiquity of the Ophir Canyon faults is furnished by

the continuity of a conspicuous rhyolite dike which

extends almost due south from mineral monument No.

4 and cuts without offset through the Cliff and Canyon faults. Obviously this dike, which is also of premineral age, is considerably older than the beginning

of the present topographic cycle, and its continuity

through the Canyon and Cliff faults fixes their age as

definitely older than the end of the magmatic cycle.

The possible offset of the dike that crops out above the

new Ophir Hill adit may show that the faulting was

later than some of the igneous activity.

Further evidence in support of this age assignment

is presented in a discussion of the relation of meta-
morphism and mineralization to these faults in the

Ophir Hill and Cliff mines (pp. 143, 150). In that

place the directly contradictory opinion of 'Wichman 94

and Olmstead 95 that the faulting is postmineral is

considered in detail.

The Canyon and Lion Hill faults can not be traced

west of the points where they meet the Lakes of Killarney fault of the Basin Range system. This criterion of relative age, though given much weight by

many geologists, is considered of doubtful significance

by the writer, because transverse faults contemporaneous with the Basin Range system in other ranges have

the same superficial relations. Also local stresses

within a single block of faulted ground may well

cause faults which are limited by earlier faults, although giving the superficial appearance of having

been cut off by them .. Fortunately the other criteria

cited above are sufficient to settle the question.

Although it is believed to be established that the

faults centering in Ophir Canyon are older than the

mineralization, there is still no precise information as

to their age. It seems probable, from the complete

similarity of the portion of the Ophir anticline south

of Lion Hill to the portion north of the Canyon fault,

that the faulting was later than the main folding but

perhaps contemporaneous with the later phases of the

folding. Butler 96 considered that the faulting was

due to the same forces that domed the strata and, accordingly, was of the same age as the development of

the Ophir anticline. At any rate the conclusion is

warranted that the Ophir-Silverado faults are not

older than the principal folding (say latest Cretaceous) nor younger than the period of igneous intrusion. Probably their movement occurred during the

igneous cycle,the early dikes being offset by the faults,

the later ones passing through them without offsets.

At present a more definite age assignment than to the

period from late Cretaceous to middle Tertiary time

seems unwarranted.

The origin of the faults is obscure, though perhaps

the inference that they are due to differential forces

acting in approximately vertical directions is warranted from their obvious close association with the

anticlinal axis and their very steep dips. On the

p.ssumption that differential vertical forces were the

proximate cause of the faulting, there are a number

c,rfpossible sources of the forces. The faulting might

be due to a marked local concentration of material and

upward squeezing beneath the Ophir anticline during

the folding and concomitant crustal shortening of the

region, or it might be due to differential release of

pressures subsequent to the folding. Another pos-

-

••Wichman, F. M., op. cit., p. 562.

9' Olmstead, S. G., op. cit., p. 447.

96 Butler, B. S., The ore deposits of Utah: U. S. GeoI. Survey Prof.

Paper 111, p. 376, 1920.

sibility is that the fOil'ceof an igneous intrusion from

below was concentrated on the portion of the Ophir

anticline just north of the faults. There is evidence,

in the localization of metamorphism along fissures

north of the Canyon faults, that an igneous mass is

not very far beneath the surface, but, of course, there

is no proof that its emplacement involved theproduction of the faults now visible. From the data at hand

it seems impossible to determine definitely the source

of the forces involved, and further discussion of the

point is hardly profitable.

A group of faults of great economic importance but

of most obscure origin and relationships is found in

Dry Canyon, centering near the Mono mines. A pair

of faults, locally called the Mark Antony and Garber

faults, strike about N. 35°-40° W. and dip steeply

northeast, passing through the saddle just east of

mineral monument No.5. Owing to poor exposures

and the close association of the two faults they have

been indicated as a single fault on Plate 11. Sporadic

outcrops of breccia and the displacement of the Humbug formation, however, permit the tracing of the

fault zone down the gulch toward the old Wandering

Jew mine. The two distinct breaks farther northwest

have probably joined in this vicinity, and the fault

passes over the spur just northeast of the Wandering

Jew incline and thence curves east and northeast to

join a northeastward-trending fault locally called the

Corbon No.1 fault, near or at the portal of the lower

Mono tunnel. The Corbon No.1 fault strikes northeast near the portal and has a rather flat dip, about

30° W. Tracing this fault northeastward reveals a

8teepening of the dip to 60° or 65° and a more northerly swing of the strike. The fault passes up the gulch

between the Mono boarding house and the Kearsarge

mine but is concealed above the level of the road. At

a point just west of the portal of the Brooklyn mine a

fault, thought from surface geology to be the Corbon

No. 1 fault, is exposed, but above the Brooklyn mine

poor exposures prevent continuous tracing. It probably passes through the westside of the saddle between

Sharp Mountain and Bald Mountain. Owing to the

absence of distinctive marker beds in the "Great

Blue" limestone it can not be traced farther . From

underground mapping there appears to be some doubt

that the Corbon No.1 fault passes west of the Brooklyn mine, as projections of dips indicate a more eastf~rlyposition. Surface exposures are too poor to settle

this important question.

By reference to the map it can be seen that the

Garber-Mark Antony fault and the Corbon No. 1

fault together outline a southward-pointing prowlike
mass, here called the Mono block because it contains

the Mono mine. The Mono block appears to have

d.ropped, relative to the adjacent rocks, with a throw

of about 650 feet on the west side and perhaps 750

feet on the east, measured on the two sides opposite to

the top of the Humbug formation within the block.

The keel or line of intersection of the faults bounding the block pitches N. 20°-30° W. at an angle of

only about 25° for the first 300 feet from its outcrop,

but projection of fault dips farther back from the

prow of the block, in the latitude of the Mono boarding house, .indicates a·steepening of its pitch to 60° N.

The grooving in the walls of the faults seems to indicate movements nearly normal to this keel, a direction

in which important movements must be mechanically

almost impossible. An attempt is made to show the

relations of the block in Plate 11, but the block is cut

too low to show the flat portion of the keel near the

·outcrop.

Within the Mono block there are many other faults

(shown in pI. 29 but not in pI. 11), which are exposed

in the Mono tunnels. The most prominent of these

faults strike N. 45°-60° E. and dip 45°-80° NW.

They appear, from their displacement of the Long

Trail shale, to be normal, with downthrow on the

northwest. Other less prominent faults within the

block strike northwest and dip southwest at rather

moderate angles. That they are normal seems indi-

<:ated by the great distance which the lower Mono

tunnel had to be extended to penetrate the Humbug

formation, almost certainly because of duplication by

these faults.

Any acceptable interpretation of these faults must

assume simultaneous movement on both sides of the

Mono block. Alternate faulting of first one side and

then the other could conceivably result in the production of such a flat-keeled block as well as of fault

grooving of the observed trends, but this interpretation must be rejected, because the basal shale of the

Deseret limestone and the prominent reef of the Madison limestone pass unbroken and well exposed beneath

the lower Mono tunnel, where at least one of the faults

would of necessity cut these strata. Accordingly the

bounding faults of the Mono block must be considered

-cognate, with simultaneous movement on them.

Three interpretations appear possible-(l) the

block was thrust from the north between curving

faults partaking of the nature of thrusts and transverse faults at the same time; (2) the block is the

·down-warped remnant of an overthrust; (3) the faults

bounding the Mono block are normal, with the induded block dropped between them. Neither of these

interpretations seems wholly satisfactory, however.

The hypothesis that the Mono block arrived in its

present position by thrusting from the north-northwest at a narrow angle to the keel, so that the Humbug

and overlying formations overrode the Deseret limestone, was first suggested to the writer by H. G.

Mitchell. According to this view, the Corbon and

Mark Antony-Garber faults would be interpreted as

rifts or transverse faults. The notable brecciation of

the rhyolite and limestone on the dip slope forming

the south wall of Dry Canyon opposite the Mono mine

is considered by Mr. Mitchell as supporting this view,

showing strong compressive movements in the direction of the keel of the Mono block. Inasmuch as the

keel near the surface plunges northwestward at a

slightly flatter angle than the dip of the beds, Mr.

Mitchell's suggestion is geometrically satisfactorythat is, the relations observed could have been produced by such a movement.

There are, howeve'r, several objections to this view.

One of these is the fact that the plunge of the keel

probably steepens notably toward the north, so that it

would be justifiable to expect, under this hypothesis,

considerably more brecciation of the Mono block (by

its compression between southward-converging faults)

than is actually to be seen. The faults within the

Mono block seem to have extended that block in the

line of its axis rather than shortened it, as would be

expected as a result of thrust faulting. Another objection is found in the trend of the fault groovings

above mentioned, but as this trend does not agree with

any likely direction of relative movement., perhaps it

can be neglected.

Another point that appears to weaken the hypothesis

of thrusting is seen in the widespread distribution of

the brecciated rhyolite, which Mr. Mitchell considered

fault breccia due to the overthrust. Such brecciated

rhyolite is found not only on the dip slope of the

Fouth wall of Dry Canyon but over the divide in

Ophir Canyon in many localities. It also occurs far

underground in the Hidden Treasure mine and in the

gulch east of the Kearsarge mine, all localities where

thrust breccia could not be expected from the surface

geology. Another objection to the hypothesis, though

nOltan exceedingly strong one, is that no severe compressive forces are known to have been operating in a

north-south direction in this part of the range and no

thrust faults unless this should prove to be one.

The hypothesis that the Mono block represents a

down-warped portion of an overthrust block seems

inadequate, because of the situation of the Mono block

near an anticlinal crest that has no other suggestion of

depression and because of the steep dip of the keel of

the block at the north end. The grooving of the fault

walls would fit such an interpretation, however.

The interpretation that the faults are normal and

the Mono block a dropped wedge appears to find its

i:'trongest support in the approximate parallelism of
the Corbon No.1 fault, which bounds the block on the

east and is conjugate with the Garber-Mark Antony

fault on the west, and the system of three faults (or

four, depending on the identification of the Corbon

No.1 fault) which run southwestward from the vicinity of the ridge line between Sharp Mountain and

Bald Mountain. As is sholwnon Plate 12, these faults

offset the Long Trail shale member and the base of the

" Great Blue" limestone and throw the strata successively down on the west. They are all most simply

interpreted as normal faults, and their parallelism

with the Corbon No.1 fault renders it highly probable that that fault too is normal. The extension

of the block in the line of its axis by the numerous

normal faults within it seems also decidedly to favor

the hypothesis of normal faulting.

The interpretation of the faults as normal, however,

though the one most favorably entertained by the

writer in the field, meets some very serious objections.

The first of these is the very fiat pitch of the keel of

the Mono block for the first 300 feet north of its outcrop, although the steeper plunge indicated farther

north seems compatible with this interpretation.

Furthermore, the pitch of the keel near the outcrop

seems too fiat to account by normal faulting for the

elimination of almost the entire thickness of the Deseret limestone, 600to 700 feet, within the short distance

occupied by the "prow" of the block. The direction

of grooving in the fault walls is contrary to that to

be expected on this hypothesis.

Thus, no hypothesis considered by the writer seems

to afford a completely satisfactory explanation of the

observed facts, and although the hypothesis of normal

faulting seems best to fit the geologic relations of the

neighboring areas, the evidence in support of it is too

inadequate to be offered with much confidence.

The determination of the faults that cut the southwest slope of Sharp Mountain is almost wholly dependent on recognition of the displacement of the

Long Trail shale member of the "Great Blue" limestone. Exposures are very poor in this part of the

area, and close study of the geologic map reveals that

the Humbug formation as mapped is very much

thicker here than in any other part of the quadrangles.

This doubtless means that it is thickened by duplicating faults. This condition was, of course, recognized in the field, but diligent and protracted search

failed to reveal other mappable faults. Innumerable

breccia zones, which might and probably do represent

fault outcrops, were observed, and their mapping was

attempted, but with no success because of the lack of

exposures and absence of marker beds in the formation. It can safely be concluded that other unmapped

faults are present on the hillside northeast of the

Hidden Treasure mine portal and that the abnormal

thickness of the Humbug formation there is due to

them.

Another fault of considerable displacement but too

thoroughly concealed to be accurately mapped extends along the ridge south of Sharp Mountain. Its

presence is indicated by the offset of the Long Trail

shale member of the" Great Blue" limestone, but its

position can not be determined within 200 or 300 feet,

possibly even more. The limestone exposures show

attitudes that completely preclude the presence of a

roll in the bedding as the cause of the discordant

relations.

There is less evidence bearing upon the date of the

Dry Canyon faulting than upon that of the OphirSilverado group. The small rhyolite mass exposed at

the mouth of the middle tunnel of the Mono mine is

doubtless of identical age with the dike that cuts the

Canyon and Cliff faults in Ophir Canyon, but it was

impossible to ascertain whether or not this rhyolite

mass is cut off by the Corbon No. 1 fault. The rhyolite is certainly not continuous across the fault, but it

contains great quantities of limestone fragments,

which may indicate that the mass was intruded along

the fault rather than that the fault cuts it off. However, the rhyolite is cut off on the northwest in the

tunnel by a fault which is roughly parallel to the Corbon No.1 fault, and it seems reasonable to ascribe this

fault to the same date as that of the Corbon No. 1

fault. If this inference is accepted, the Corbon No.1

fault and presumably the entire Dry Canyon group of

faults date from a time later than the rhyolite intrusion and are therefore younger than the principal

Ophir Canyon faults. However, as the faults show

some pyritization it is probably safe to assume that

the faulting was earlier than the mineralization, and

that the difference in age between the Dry Canyon and

Ophir Canyon faults is probably not so great that the

two groups can not be assigned to the same general

Deriod,which is roughly that of the igneous intrusion.

In view of the lack of decisive evidence as to the

movements involved in the emplacement of the Mono

fault block much uncertainty must attach to any analysis of the forces involved in the faulting. The general

parallelism of the Corbon No.1 fault and the three

or four recognized faults on Sharp Mountain, which

led to the tentative interpretation of the Corbon No.

1 fault as normal, naturally leads to a similarly tentative assignment of an identical cause for the production of the Corbon No. 1 and the Sharp Mountain

faults. The curvature of the faults around the Mono

block seems to indicate that here, too, as with the
Ophir Canyon faults, vertically acting differential

forces caused the fracturing. It seems probable that

uplifting forces acting on the periphery of the block

are a less likely possibility as causes of the movement

than depressive forces acting on the block itself, because the Sharp Mountain faults all drop toward the

west, in the direction of the anticlinal axis, where, on

the assumption of control by uplift during regional

compression the reverse would be expected. Furthermore, the Mono block is negligibly small compared

with the entire anticline, and there seems little likelihood of its having failed to respond to the uplift that

produced the anticline. Thus the faults seem more

accordant with a hypothesis of their origin by differential support from beneath durin!! a period of

relaxation following the folding than with one

involving faults formed during compression. The

possibility that the entire group may be due to forces

arising from igneous intrusion below can not be dismissed, however, and it may be that intrusion was the

real cause of the faulting. Of course, if the Mono·

block is really due to low-angle thrnsting from the

north, appeal must be made to quite different forces

in seeking its origin.

Evidence of a zone of faults that separates the

great mass of the Oquirrh Mountains from the alluvium-filled depression of Rush Valley is afforded by

actual exposure of many clearly defined faults, by

stratigraphic displacement, by transection of structure, and by topographic unconformity between the

adjoining areas. Not all these evidences accompany

each fault, but some of the faults show all four, and

many are indicated by two or three of them.

The zone of faults has been traced from a point

about a mile southeast of the mouth of Mercur Canyon

to a point just north of Soldier Canyon, and has an

average trend of about N. 20° W. There is reason to

believe that the system continues along the entire

west front of the range, although there is no unequivocal evidence to show it between Soldier Canyon and

the north edge of the Stockton quadrangle.

The zone consists, within the Stockton and Fairfield quadrangles, of five principal faults, so far as

available evidence indicates. In order from south to

north these are (1) an unnamed fault of unknown

displacement separating the mountain mass and the

alluvium south of Mercur Canyon; (2) the West

Mercur fault, almost continuously exposed from West

Mercur to the Bates ranch at Ophir Creek; (3) the

Lakes of Killarney fault, which is traceable from a

point south of Silverado Canyon to a point about a

mile south of Soldier Creek and is well definedjust east

of the Lakes of Killarney mine; (4) an unnamed fault

which separates the block of "Great Blue" limestone

just north of the mouth of Dry Canyon from the

Rush Valley alluvium; (5) the Soldier Canyon fault,

which can be traced for about a mile to the north and

about 2 miles to the south from the mouth of Soldier

Canyon.

The southernmost fault of this zone is concealed

beneath the alluvium in the S. % sec. 13, T. 6 S., R.

4 W. A prospect shaft about 60 feet deep and a few

feet west of the contact between the alluvium and the

"Great Blue" limestone penetrates, as shown by the

material on the dump, a considerable thickness of

black carbonaceous shale. Neither the Humbug nor

the part of the " Great Blue" limestone exposed east

of this shaft and dipping toward it contains any similar material, but such shale is present in the Long

Trail shale member, higher in the" Great Blue." It

is logical to infer that the shaft is sunk on the downthrown block west of the fault, thus penetrating these

stratigraphically higher beds. The throw of the fault,

on this interpretation of the relations, is about 100 to

200 feet. Additional support of this interpretation is

seen in the sharp, steep scarp separating alluvium and

limestone between the second gulch north of McFait

Canyon and the gulch next south of the mouth of

Mercur Canyon. Were these isolated occurrences, little

weight would be attached to them as evidence of faulting, but similar features farther northwest are definitely associated with demonstrable faults, and the

parallelism seems sufficient to warrant the conclusion.

No traces of this supposed fault appear on its strike

farther north, but the high tongue of alluvium which

reaches an altitude of 6,000feet just south of the mouth

of Mercur Canyon conceals a considerable interval,

and it may be that the fault curves westward to join

the West Mercur fault or that it dies out in this

interval.

The West Mercur fault is a strongly marked fracture that passes through the old camp of West Mercur

or West Dip and divides the rolling foothills on the

northeast from the smooth alluvial slopes on the southwest. A low scarp with some interruptions marks the

position of the fault and trends in a general course N.

30° W. from a point about half a mile southeast of

West Mercur to the alluvial fill of Silverado Canyon,

beyond which it is again traceable for a full mile to a

point just north or Ophir Creek, at the Bates ranch.

Between West Mercur and Ophir Creek the fault is

exposed in prospect pits at several places as a marked

breccia zone accompanied by dragged limestone beds.

Where so exposed, the drag suggests that the fault is

normal with the downthrow on the west. Accordingly
glomerate of the hanging wall is not very clearly seen,

because of the general absence of bedding, but it is

perceptible, and the gouge and slickensides are well

exposed. The fault dips about 60° 'V. here, but at a

prospect pit a little less than a mile farther

north it dips 49° W.

In the workings of the old La Cigale mine,

about a mile farther north, similar relations

are seen, as shown in Figure 10. The fault

here dips about 40° W. and is exposed from

the shaft collar, but the clearest exposure,

illustrated by the sketch, is seen about 150 feet

down the incline. Here the fault separates a

footwall of " Great Blue" limestone from the

hanging wall of alluvium. The alluvium is

here finer textured than in the Daisy mine,

and accordingly the drag of the fault is more

clearly visible. Considerable gouge occurs on

the fault and in two places is seen to cut

through the alluvium, leaving undisturbed

coarse gravel or fanglomerate in the footwall

against finer-textured material in the hanging

wall. This is clear evidence of rejuvenated

movement on a fault which had had its scarp

partly buried by alluvium.

The sharp break in the surface of the bedrock in this vicinity, as shown diagrammatically in Figure 11, is additi~nal evidence that

the lower contact of the alluvium is a buried

.fault scarp. The scarp is completely masked

by alluvium, however, and is not exposed in

the present topography for a few hundred feet

in this vicinity.

The La Cigale and Daisy mines both found

ore at depths of several hundred feet. The

workings are no longer accessible. According

to men familiar with these mines when they

were in operation, the ore occurred in the

fault, between limestone walls. The ore was

yery similar to that at the famous old camp

of Mercur, about 3 miles east,

and presumably was formed

at the same time-a time

fixed on grounds set forth below (pp. 84, 86) as almost

surely pre-Miocene. The existence of the fault since early

Tertiary time (though, of

course, it does not follow that

Basin Range faulting, as

such, began at so early a

date) is of interest in view of the recurrence of its

activity in Recent time. A similar phenomenon,

though not as well established, probably occurs in the

Stockton mining district, about 10 miles to the north.

(See p. 90.)

the scarps as exposed are interpreted as true fault

scarps, only slightly eroded.

A particularly instructive exposure of the £ault has

been made in the inclined shaft of the Daisy (West

West Mercur

-fault \

DAISY

SHAFT

j

FIGURE 9.-Relations of West Mercur fault in inclined shaft of Daisy (West Dip

No.1) mine

FIGURE H.-Relations of West Mercur fault to the topography, alluvium, and bedrock near West

Mercur

Dip No.1) mine, just south of the abandoned town

site of West Mercur. The relations here are shown in

Figure 9. A strongly slickensided mass of alluvium

is separated by a black gouge from the limestone footwall of the fault. The drag in the ill-assorted fan-
At the La Cigale mine the scarp does not project

above the surface, but, on what is probably the same

line of faulting, a scarp is to be seen in the alluvium

just south of Silverado Creek, and a similar searp

with a displacement of about 40 feet occurs north of

Ophir Creek just east of the road from Dry Canyon

to the Bates ranch. (See pI. 9, B.) The fault was

not seen north of Silverado Canyon except for a short

distance just south of the Bates ranch, where it drops

the Oquirrh formation on the west against the" Great

Blue" limestone and Manning Canyon shale on the

east. Although not well exposed, the dip here is probably about 55° W. Ample evidence for the existence'

of the fault, however, is seen in the sharp topographic

break between alluvium and limestone and in the abnormally steep dips in the limestone along this line.

The cappings of alluvium on the 5,950-foot hill just

north of Silverado Canyon and on the larger 6,100-

foot hill south of the power house in Ophir Canyon

may owe their high position to uplift along this fault,

but it is possible that they represent a higher stage

of alluviation in a more arid period than the present.

Perhaps the most striking of the Basin Range faults

in the Stockton quadrangle is the Lakes of Killarney

fault, which crosses Ophir Creek just west of the 6,000-

foot contour and trends about N. 40° ""V. It can be

traced to the south by the strong topographic contrast

on the two sides and by its own wide breccia zone.

The breccia is exposed on the saddle east of the 6,500-

foot hilltops on the divide between Ophir and Silverado Creeks and farther south on the hill between Silverado Creek and West Dip Gulch, on the south slope

of which it is represented in a zone of vertical brecciated beds of the Long Trail shale member of the

" Great Blue" limestone. It can not be traced farther

and apparently dies out before reaching West Dip

Gulch. The saddles through which the fault passes

to the north are continued to the south, almost to the

mouth of Mercur Canyon, but no faulting is associated

with those south of "Vest Dip Gulch, which are due

to the presence of the easily eroded Long Trail shale

member in the lower part of the" Great Blue" limestone. Dip measurements made by the three-point

method on the breccia zone give 60° as the average dip

of the fault south of Ophir Creek.

A breccia zone found in Silverado Canyon and apparently converging with the main fault just south

of the stream bed is the only branch of this fault

noted. As no recognizable marker beds other than

the Long Trail shale member in the "Great Blue"

limestone were discovered, the displa{lement of the

major fault could not be accurately determined.

However, the attitude of the beds cut by the fault and

the thickness of "Great Blue" limestone exposed

southwest of it seem to indicate that the fault begins

at the south as a fracture of slight displacement which

increases northward, reaching perhaps 1,000 feet on

the divide between Ophir and Silverado Creeks and

increasing yet more rapidly to the bottom of Ophir

Canyon. A short distance north of Ophir Creek the

Manning Canyon shale is dropped against the lower

beds of the" Great Blue" limestone, a stratigraphic

displacement of at least 3,000 feet. Perhaps half a

mile north of the creek the fault is exposed as a

slickensided surface, accompanied by considerable calcite-cemented breccia. Here its dip is 57° ""V. Across

the next gulch to the north a small prospect pit exposes the fault, which has much limonite-stained gouge

associated with it and locally strikes N. 55° W. and

dips 80° SW. Some other prospect pits between this

point and Dry Canyon expose the fault, though less

satisfadorily. North of Dry Canyon the fault is

easily traced by the breccia and steeply dipping

dragged beds across the saddle east of the small 6,724-

foot knoll. Here the displacement is indeterminate,

though certainly not less than 2,000 feet and perhaps

as much as 3,500 feet. The 3-point method here

yielded a measured fault dip of 62° W. Followed

north, the fault can be traced through the next saddle

and then down the mountain side to the 6,250-foot contour, where it is masked by alluvium for about a quarter of a mile. About a mile north of Dry Canyon it

emerges from the alluvium and crops out in a gulch

as a steeply dipping breccia zone, along which the

lower limestones of the" Great Blue" are dragged to

a nearly vertical dip. The fault here strikes N. 20°

W. and dips 65° SW. It crops out at intervals from

this point north to the point where the mountain front

swings sharply east, about a mile south of Soldier

Creek, beyond which it is masked by alluvium. Its

most northerly exposure reveals its dip as 60°. For

most of the distance the fault divides the alluvial

slopes from the limestone mountain, though it is itl'elf

covered at many places by alluvium.

Just west of the Lakes of Killarney fault, north of

Dry Canyon, is a block of "Great Blue" limestone,

which is cut off on the west by a fault of the Basin

Range system. This fault is well exposed for nearly

half a mile, and several prospect pits have been dug

along it, in one of which the fault is seen to strike

N. 5° W. and dip 54° W. This fault is cut by a

poorly exposed fault trending a little north of east and

dipping about 75° S. just south of the Dry Canyon

road. To the movement along this eastward-trending

fault is probably due the presence of the limestone hills

Horth of Dry Creek, opposite the alluvial slopes south
of the creek. It is possible that the Basin Range fault

is continued to the south of this eastward-trending

fault, for in an inlier of bedrock exposed beneath the

alluvium of Dry Canyon just south of the center of

sec. 21, T. 5 S., R. 4 W., there is a marked breccia zone

"Withassociated dragged beds, indicating faulting of

similar north-northwesterly trend and downthrow on

the west. The fault shown in this small exposure is

probably of slight displacement, however, inasmuch as

the rock on both sides of it belongs to the Manning

Canyon shale. It is probably merely sympathetic with

the movements on the major faults just described.

The Soldier Canyon fault begins obscurely about a

mile north-northwest of Gisborn, where it separates

the foothills from the main mass of Bald Mountain,

and has been traced to a point a little over half a mile

north of Soldier Creek, beyond which it could not be

identified, owing to diminishing throw, poor exposures,

and the fact that no recognized marker beds occur on

opposite sides of it. The few exposures of this fault

are limited to prospect pits. All indicate dips of

about 500

-600 W. The exposures are particularly

unsatisfactory, owing to talus and brush, and the

displacement of even so good a marker bed as the

Long Trail shale member is uncertain within perhaps

200 to 300 feet. This uncertainty is indicated on

Plate 12 by the dotted contacts of this shale member

on the east side of the fault.

OTHER FAULTS SUPPOSED TO BELONG TO THE BASIN RANGE

SYSTEM

Faults parallel to the West Mercur fault occur east

of that fault both north and south of Silverado Canyon, but as all are in the "Great Blue" limestone,

where no good marker beds are present, it is impossible to ascertain their magnitude. The more prominent faults, judged by the widths of their breccia

zones, are indicated on the map. A similar fault of

unknown displacement runs about a quarter of a mile

east of and parallel to the Lakes of Killarney fault

for perhaps half a mile just north of Silverado

Canyon.

It is probable that Basin Range faulting has occurred in the Stockton mining area, and some of the

numerous faults exposed in that district may be of

this system (see p. 90) ; but it is preferred to class as

Basin Range faults only those which are directly !,eflected in the topography, and on this definition all the

faults of the Stockton mining area, with possibly one

exception, are excluded and will be discussed as a

separate group.

The one exposed fault that is possibly to be assigned

to the Basin Range system is visible for about a third

of a mile north from Ben Harrison Gulch, opposite

the Stockton Standard prospect. This fault dips

about 400 W. as ·indicated by the silicified quartzite

breccia marking it. This breccia forms a steep slope

50 to 100 feet. high between two flattened slopes, the

lower of which is capped by alluvium. That this

fault belongs to the Basin Range system is by no

means certain: it may be much older, as its position

suggests that it is a northward continuation of the

Muerbrook fault, the most conspicuous of the great

number of mineralized normal faults of the Stockton

district. Also its breccia is cemented with silica, presumably indicating no recent movement. But it is

topographically expressed, and the sharp topographic

break continues along the Muerbrook fault as far

south as Southport Gulch, so that it is at least possible

that some downthrow of the west block has occurred

along this fault during the present erosion cycle. The

amount of displacement of this topographically prominent "fault could not be determined, but the Muerbrook

fault, which occurs on its strike to the south and passes

just east of the Black Diamond shaft, has a shift of

fully 800 feet, the west side moving southward relative

to the east. If the topographically prominent fault is

identical with the Muerbrook fault, its present scarp

must indicate recent rejuvenation of an old premineral

(pre-Miocene) fault-a phenomenon already noted as

having occurred on the West Mercur fault.

No other faults of the Basin Range system were

observed in the area between Soldier Creek and Tooele.

Nevertheless, full confidence is felt that the range

front is here also controlled in the large by faulting,

although in detail the wave cutting of Lake Bonneville is the cause of most of the distinctly alined transected spurs. The transection of the geologic structure

by the range front which farther south and farther

north 97 is due to demonstrable faults can here be

justifiably referred to an identical origin.

Among the characteristic features of the Basin

Range faults of the Stockton and Fairfield quadrangles

are their steplike displacements, their en echelon

tendency and consequent lack of persistence along the

strike, their variable but prevailingly steep dips, and

the possibility that some of the faults reflected in the

present topography represent merely rejuvenation of

much older faulting.

Distribwtive a;nd en echelon farultirl!g.-The displacement of the valley block with respect to the mountain

block occurred on demonstrable distributive faults

97 Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon. 1, p. 352,

1890. Atwood, W. W., The physiographic conditions of Butte, Mont.,

and Bingham Canyon, Utah, when the copper ores in these districts

were enriched: ECOll. Geology, vol. 11, p. 735, 1916.
from about the latitude of West Mercur nearly to

Soldier Canyon. It is possible, though not certain,

that the numerous subparallel, westward-dipping normal faults of the Stockton mining district, several

miles farther north, have also participated in the

Basin Range displacements, though the first movement along them probably dates back to pre-Miocene

time. The largest of these, the Mum'brook fault, as

mentioned above, falls in line with a topographically

expressed fault and lends some support to the suggestion of step faulting furnished by the local more gradual mountain slope, such as has been described by

Johnson.98 Step faulting of units comparable to those

south of Soldier Creek along Basin Range fronts has

also been described by Gilbert,99Russell,l Louderback,2

Reid,3 Knopf,4 and many others. There is every probability that many other faults bearing a steplike relation to those seen are concealed beneath the alluvium

of Rush Valley.

En echelon arrangement of some of the Basin Range

faults has not been so generally recognized, though it

has been described by Louderback 5 and Knopf.6

The tendency toward en echelon arrangement of the

Basin Range faults is evident on inspection. The

fault zone trends N. 20° W., but the individual faults

composing the zone trend N. 20°-50° W.

Length of faults.-The nonpersistence of the individual faults has been touched upon in the foregoing

descriptions. Nothing is known of the extent of the

West Mercur fault, as it passes beneath alluvium both

to the north and south. The great Lakes of Killarney

fault, bounding the mountain block for 4 miles, also

passes out beneath the alluvium toward the north, but

southward it dies out within less than 2 miles south of

Ophir Creek. The Soldier Canyon fault can not exceed 3 miles in length. Nothing is known of the strike

length of the faults farther north. It is probable that

a fault occurs beneath the alluvium near the highway

east of Bauer and Stockton, but no observations were

possible to establish the inference.

The very different distances to which the southern

spurs of the Oquirrh Mountains project into the low98Johnson, D. W., Block mountains in New Mexico: Am. Geologist,

vol. 31, pp. 135-139, 1903.

99 Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon. I, p. 348,

1890.

1Russell, 1. C., A geological reconnaissance in southern Oregon:

U. S. Geol. Survey Fourth Ann. Rept., pp. 431-461, 1883.

2 Louderback, G. D., Basin Range structure of the Humboldt region,

Nevada: Geol. Soc. America Bull., vol. 15, pp. 307-308, 1904; Morphologic features of the Basin Range displacements in the Great Basin:

California Univ. Dept. Geology Bull., vol. 16, pp. 17-25, 1926.

s Reid, .r. A., 'l'he geomorphogeny of the Sierra Nevada northeast of

Lake Tahoe: California Unlv. Dept. Geology Bull., vol. 6, pp. 112-136,

1911.

• Knopf, Adolph, Geologic reconnaissance of the Inyo Range an<1the

eastern slope of the southern Sierra Nevada, California: U. S. Geol.

Survey Prof. Paper 110, pp. 78-89, 1918.

5 LOUderback, G. D., op. cit. (1926), p. 29.

6 Knopf, Adolph, op. cit., p. 89.

land area of Rush Valley, which led Atwood" to interpret this portion of the range front as exhibiting an

erosion topography, are clearly seen to be due to a

combination of these factors of step faulting, en echelon faulting, and linear discontinuity of the individual

faults. The topography is as clearly a fault product

as that of the range front north of Tooele, which he

interpreted in that way.

This somewhat complex pattern of the Basin Range

faults is in contrast to the common diagrammatic representation of those features, but is by no means

unusual in the Great Basin. Louderback,8 Reid,9

Lawson,lO and Knopf 11 have described similar features. Gilbert concluded, after a thorough study of

the Wasatch Range, that whether or not the Wasatch

is typical of Basin Ranges in its contour, great simplicity of basal outline is evidently not an essential

characteristic of faulted range fronts.l2 The present

study supports this conclusion.

Dips of faults.-An additional point of interest in

connection with the frontal faulting of the Oquirrh

Mountains is the prevailingly steep dip of the fault

planes. Fourteen measurements of dip were made,

either on bedrock fault surfaces or by the 3-point

method, in places where the topographic relief of the

country traversed by the faults was sufficient. The

measurements range from 40° to 64° and average fi7°.

The West Mercur fault changes in dip from 40" to 60°

within about a mile, showing that the faults, as would

be expected, are surfaces warped in dip as well as in

azimuth. The other faults show comparable variations. The relation of the dip of the faults to the angle

of slope of the fault scarps is discussed elsewhere,I3

the conclusion being reached that the angles of slope

of the fault scarps are not indicative of the actual dips

of the faults, as has been maintained by Davis and

Gilbert, but that the scarps slope at lower angles than

the faults.

'Early movement.-That there have been repeated

movements, all later than the folding, on the West

Mercur fault seems well established, and the same may

be true of the Muerbrook fault. However, the dates

of the repeated movements of the West Mercur fault

can not be fixed with precision from the evidence at

hand.

7 Atwood, W. W., The physiographic conditions of Butte, Mont., and

Bingham Canyon, Utah, when the copper ores in these districts were

enriched: Econ. Geology, vol. 11, p. 735, 1916.

8 Louderback, G. D., op. cit. (1926), p. 25.

9Reid, J. A., op. cit.

10 Lawson, A. C., Recent fault scarps at Genoa, Nev.: Seismol. Soc.

America Bull., vol. 2, pp. 193-200, 1912.

11 Knopf, Adolph, op. cit., pp. 78-89.

12 Gilbert, G. K., Studies of Basin Range structure: U. S. Geol. Survey Prof. Paper 153, p. 22, 1928.

18 Gilluly, James, Basin Range faulting along the Oquirrh Range,

Utah: Geol. Soc. America Bull., vol. 39, pp. 1103-1130, 1928.
Premineral movement along the West Mercur fault

can not be proved in the mine shafts that remain

accessible, but inasmuch as ore was reported to have

occurred in the fault and was mined at points distributed along the strike for more than 2 miles, it seems

very probable that the ore was oiriginally deposited in

the fault and not merely dragged in and that the first

movement on the fault therefore antedated the mineralization. The ores of the Daisy and La Cigale mines

greatly resemble'd those of the Mercur district, only

about 3 miles to the east, and the presumption that

they were deposited at approximately the same time

is justifiable. If it is assumed, then, that the first

movement Oill the West Mercur fault antedated the

mineralization and that the mineralization at West

Mercur was contemporaneous with that at MereuI', it

remains to establish the age of the mineralization at

MereuI'. This question is likewise one that can not be

answered directly from evidence within the area.

The mineralization of the several districts of the

Oquirrh Mountains was closely associated with the

igneous intrusions and did not occur in parts of the

range where igneous rocks are absent. Without regard to the moot point whether or not the igneous

intrusions furnished the sourCeof the ore, it is a reasonable inference that the ores and the igneous activity

are somehow genetically related, and accordingly the

date of the mineralization may be presumed to be

almost the same as that of the igneous activity. On

grounds discussed previously, this date is fixed as falling sometime in the early Tertiary. Accordingly it

seems probable that the West Mercur fault dates from

early Tertiary time.

BasVn Range movement.-There is no direct means

available of determining the amount of movement

that occurred on the West MereuI' fault, either at the

time of its inception or later. But evidence of repeated movement along it and the presence of the

, fault sca·rpin the alluvium at the Bates ranch testify

to its activity until Recent time. Presumably the

period of principal movement along it was the same

as that of the principal movement on the other Basin

Range faults-that is, the movement which is expressed in the present topographic relief of the

country.

The local geology here again furnishes no definite.

information as to the date of this Basin Range movement. The latest consolidated rocks cut by the faults

are Carboniferous and obviously offer no clue as to

the date, but inasmuch as the folds are also transected

and evidence has been advanced above to show that the

folding was probably early Tertiary, there is no

doubt that the Basin Range faulting is of later date

than that. For more definite .information recourse

must be had to analysis of the topography of the

area.

The topography of the southern and eastern slopes

of the Oquirrh Mountains is in the stage of pronounced early maturity, or rather, considerable fragments of a mature erosion surface are still present.

This surface is in marked topographic unconformity

with the abrupt mountain slopes above the Basin

Range faults and with the canyon incisions, and obviously this contrast is due to the Basin Range faulting.

On grounds discussed elsewhere in this report (pp.

40 and 77) this prefaulting erosion surface is probably not younger than middle Pliocene nor older than

Oligocene, and the principal movements of uplift of

the tilted block of the range relative to Rush Valley

are presumed to have begun sometime in this interval-that is, in Miocene or earlier Pliocene time. The

evidence is strong, at least as regards the West MereuI' fault, that the movement has continued at intervals practically to the present day.

It is obvious that such a major question in geology

as that of the cause of mountain formation can never

be answered by a study of any single range, but its

decision must rest upon a synthesis of material gathered from sources all over the world. However, an

ultimate solution of this problem, as well as of any

other fundamental problem in geology, must fit the

facts of local geology or permit a satisfactory explanation of any discrepancies between fact and theory.

An attempt to determine the fundamental cause of the

Basin Range faults-that is, the factors involved in

the production of the particular orogenic type found

in the Oquirrh Mountains-is beyond the scope of

this report. It may be appropriate, however, to discuss briefly some of the limitations imposed by the

local geologic facts upon a satisfactory theory for the

origin of the Basin R-anges,of which the Oquirrh is a

typical example. A more detailed discussion is given

elsewhere.14

It is commonly recognized that the faulting of the

Great Basin must be largely independent of the local

surficial geology and of local loading and unloading

of the crust. The conclusion is so well accepted as

hardly to require argument, but it was thought worth

while to investigate the matter to some extent.

It has been suggested that erosion from the mountain blocks and deposition upon the valley blocks has

led to rising of the mountains and sinking of the valleys in response to isostasy. It is, of course, obvious

that such a process offers no key to the cause of the

initial faulting by which the mountains were produced, but there can be no doubt that the tendency of

the transfer of load is to continue the movement, even

though the process must eventually" run down." Ac14 Gilluly, James, Bashl Range faulting along the Oquirrh Range.

Utah: Geol. Soc. America Bull., vol. 39, pp. 1103-1130, 1928,
cordingly an attempt was made to determine the effect

of the tendency.

The first requirement of a test of this tendency is

the determination of the rock masses transferred from

mountain block to valley block since the inception

of the Basin Range faulting. This requires a reconstruction of the prefaulting topography, which in the

Stockton and Fairfield quadrangles can only be

crudely effected owing to the severe postfaulting

erosion on a surface that was originally by no means

reduced to a plain. The unevenness of the submature

erosion surface obviously offers great difficulties to reconstruction, but it is thought that a surface sloping

from 9,000 feet at Soldier Canyon to 8,500 feet at

Lion Hill and to 7,300 feet at Alma Young Canyon

would fairly represent the general pre faulting topography. Computation of the volume of material inclosed between such a surface and the present one

was made from planimeter measurements on contours

1,000 feet apart by means of the end-area formula.

The reconstruction of the surface was not considered

sufficiently accurate to justify the use of more precise

formulas or more closely spaced measurements. Because of inadequate remnants of the prefaulting

topography north of Soldier Creek, the computation

did not include areas north of the drainage basin of

this stream. For the same reason it was impossible

to include the east slope of the range. Accordingly

the computation was restricted to the area west of

the main divide and south of the water parting north

of Soldier Creek.

According to this computation about 10.2 cubic

miles of rock has been eroded from this district in the

present (postfaulting) cycle. The area from which

the material was derived is almost 49 square miles,

and the average thickness of the amount eroded is thus

0.21 mile, or 1,100 feet. In order to compute the

theoretical effect of the addition of this load to the

valley block, it is necessary to assume a certain area

of deposition. The assumptions were therefore made

that the material was all deposited in Rush Valley

and that the contributions of the Stansbury and

Oquirrh Ranges have not overlapped (or if they have,

they have canceled each other), so,that the area of the

present fans from the Oquirrh Range includes all the

deposits of postfaulting age derived from that mass.

Such assumptions are conservative rather than otherwise-for instance, it is evident that some material

was removed from Rush Valley to Tooele Valley before Lake Bonneville time, but it is thought that such

errors would cancel one another if larger areas were

compared and that the assumptions stated above will

lead to a maximum for the loading effects. In so far

as material has left the region, these assumptions will

lead to exaggeration of differential load effects.

On these assumptions, then, the 10.2 cubic miles of

rock was distributed over an area of roughly 80 square

miles, producing an average load 0.1275 mile, or 675

feet, thick. Owing to the lower specific gravity of the

alluvium, its thickness as deposited would be greater,

perhaps is- X 675, or 830 feet, but this would not affect

the load involved.

If the mountain and valley areas are regarded as

forming a system, the transfer of surface rock from

one to the other introduces a tendency for the mountain block to rise in response to the unloading and for

the valley block to sink in response to the loading,

until, by the transfer of material in the zone of flowage

from the loaded to the unloaded block the total masses

of the columns above the level of compensation are the

same and are equal to their respective masses before

the faulting. On the most favorable assumption-that

the subcrustal material has the same density as the

wrface rock transferred-complete local isostatic compensation could account for only 1,100+675=1,775

feet of the total displacement between the mountain

and valley blocks. But from the evidence in hand the

average displacement on the fault zone can hardly be

less than 3,000 feet and may exceed 5,000 feet. This

indicates that local compensation could theoretically

account for perhaps one-thiru to one-half of the observed displacement. As the most severe critics of the

idea of crustal competence are willing to grant to the

crust strength sufficient to sustain (at least in part)

loads of 3,000 :feet of rock over an area with a radius

of 18 miles,t5 it seems clear, even if there are large

errors in the assumptions above made as to volume

transfers, that in an evaluation of the causes of the

faulting the isostatic tendency between valley and

mountain blocks must be considered of entirely subordinate importance in producing the observed displacement between them.

The same conclusion-that individual Basin Ranges

are sustained by the strength of the earth's crust-was

reached by Gilbert in an entirely different way, from

consideration of the loading effect of the water of

Lake Bonneville and the lack of response to this

loading through faulting such as would be expected

on an assumption of local isostatic control of the

Basin Ranges.16

On any hypothesis of formation of the Basin Range

faults, loading and unloading of adjacent blocks could

not have occurred until there had been primary faulting to produce the necessary surface relief to bring

about erosion. It seems, from the evidence just briefly

reviewed and from other considerations, that the ulti15 Bowie, William, On the size of the block of the earth's crust which

may be independently in isostatic equilibrium: Washington Acad. Scl.

Jour., vol. 14, pp. 355-362, 1924.

" Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon. 1, pp.

357-360, 365-392, 1890.
mate cause of first faulting has likewise been the prime

factor in continuing the movement.

Whatever the ultimate forces involved in producing

the Basin Range faults of the Oquirrh Mountains may

have been, this range is so like the others of the Basin

and Range province that it seems safe to assume that

these forces were operative over the entire segment of

the continent between the Wasatch Range and the

Sierra Nevada. Several theories have been advanced

to account for the orogenic type here represented. The

discussion of these theories can hardly be profitable

here, but the writer can not refrain from expressing a

preference for one of the oldest of them all-that of

GilbertY This theory would explain the ranges by

vertical or nearly vertical adjustments of brittle surface rocks to folds induced by regional compression in

a deep-seated layer, thus accounting for the lack of

correspondence between the fault lines and the preexisting folds of the surface rocks and also for the

general parallelism of the ranges over the region as a

whole.

The mining area near Stockton is cut by a great

number of faults. Most of these are relatively very

small, but a few are of considerable throw. Because

of their close connection with the mineralization, all

are of prime economic importance.

The faults of this area fall into two principal systems, and there is evidence of at least two periods of

faulting in each system. The more prominent as well

38 the economically more important faults strike between N. 40° ",V. and N. 40° E., but by far the greatest

number strike between much more narrow limits, N.

10°-30° E. Nearly all dip westward at angles between 45° and the vertical, but most of them range

between 60° and 70° W. This system is called, in the

mining camp, the north-south system; the individual

faults and fissures are called crossings. The other

fault system is closely related to the attitude of the

beds, and the individual faults strike nearly east and

dip steeply north. This system is locally called the

east-west system.

The earliest fault movement for whieh evidence was

seen occurred on the east-west faults. Little indication of this movement is afforded by the surface exposures, but there is clear evidence in the workings of

nearly all the mines, consisting of shear zones develeped in the limestones of the Oquirrh formation and

locally in the adjoining quartzites, as in the Hampton

lease, on the 1,200-foot level of the Honerine mine,

where the " St. Patrick" limestone has been cut by a

gently curving fault, which passes into the footwall

17 Gilbert, G. K., U. S. Geog. and Geol. Surveys W. 100th Mer. Rept..

vol. 3, p. 62, 1875.

quartzites in both directioills along the strike after

lying in the limestone for over 400 feet. Other faults

of this system rigorously follow a given limestone.

Perhaps the most striking example is furnished by the

"Galena King gouge," a brecciated and highly altered

zone due to shearing and subsequent mineralization of

the limestone. The" Galena King gouge" has been

recognized from the Argent mine, the most easterly

development of the district, almost to the Muerbrook

fault, which cuts off the" Galena King" limestone at

the mouth of Southport Gulch. Through practically

all of this distance of nearly 1V2 miles the" Galena

King" limestone carries this" gouge" or fault ZOille,

in some places near the footwall of the bed, elsewhere

near the hanging wall. The" Hercules" limestone in

much of the workings of the Honerine mine shows

similar shearing and in places is even completely cut

out by faulting subparallel to the bedding. Similar.

faults have been observed in the" Honerine " limestoille

near the Palace ore shoot and at the 105 crosscut, as

well as farther east at the Wier stopes, all on the

1,200-foot level. These and other east-west faults will

be discussed in detail in the mine descriptions, as they

are of merely local importance.

As all the faults just mentioned are practically bedding faults and antedate the dike intrusions, it is quite

out of the question to prove the amount of movement

on any of them. It seems likely, however, in view of

the very moderate amount of brecciation that accompanied the faulting, as well as the rather remarkable

persistence (with few exceptions) of each fault within

a single bed, that the displacements have been very

slight and merely such differential movements as must

necessarily occur between competent beds in folding.

The practical restriction of the faults to the limestones

may be accounted for by the relative incompetence of

the limestones as contrasted with the strong quartzites

between which they lie. On this assumption the faults

are contemporaneous with the folding. Similar faults

may have been formed in the quartzites, but inasmuch

as the mine workings have been confined as much as

possible to the limestones, little opportunity was offered to determine the existence of strike faults in

the quartzites, and surface indications of such faults

are lacking.

The second fault movements took place on the northsouth system and are of greater economic importance

than any others recognized in the district. An attempt was made in the field mapping to portray these

faults, but the scale of the map (pI. 12) is too small

to reveal them without confusion, and therefore they

are not shown. However, a careful study was made

of the displacements of the " Galena King" limestone

from the Argent mine to Rush Valley, and in that

interval eight faults of measurable displacement were
mate cause of first faulting has likewise been the prime

factor in continuing the movement.

Whatever the ultimate forces involved in producing

the Basin Range faults of the Oquirrh Mountains may

have been, this range is so like the others of the Basin

and Range province that it seems safe to assume that

these forces were operative over the entire segment of

the continent between the Wasatch Range and the

Sierra Nevada. Several theories have been advanced

to account for the orogenic type here represented. The

discussion of these theories can hardly be profitable

here, but the writer can not refrain from expressing a

preference for one of the oldest of them all-that of

Gilbert.17 This theory would explain the ranges by

vertical or nearly vertical adjustments of brittle surface rocks to folds induced by regional compression in

a deep-seated layer, thus accounting for the lack of

correspondence between the fault lines and the preexisting folds of the surface rocks and also for the

general parallelism of the ranges over the region as a

whole.

The mining area near Stockton is cut by a great

number of faults. Most of these are relatively very

small, but a few are of considerable throw. Because

of their close connection with the mineralization, all

are of prime economic importance.

The faults of this area fall into two principal systems, and there is evidence of at least two periods of

faulting in each system. The more prominent as well

3S the economically more important faults strike between N. 40° "\V. and N. 40° E., but by far the greatest

number strike between much more narrow limits, N.

10°_30° E. Nearly all dip westward at angles between 45° and the vertical, but most of them range

between 60° and 70° W. This system is called, in the

mining camp, the north-south system; the individual

faults and fissures are called crossings. The other

fault system is closely related to the attitude of the

beds, and the individual faults strike nearly east and

dip steeply north. This system is locally called the

east-west system.

The earliest fault movement for which evidence was

seen occurred on the east-west faults. Little indication of this movement is afforded by the surface exposures, but there is clear evidence in the workings of

nearly all the mines, consisting of shear zones developed in the limestones of the Oquirrh formation and

locally in the adjoining quartzites, as in the Hampton

lease, on the 1,200-foot level of the Honerine mine,

where the " St. Patrick" limestone has been cut by a

gently curving fault, which passes into the footwall

17 Gilbert, G. K., U. S. Geog. and Geol. Surveys w. 100th Mer. Rept..

vol. 3, p. 62, 1875.

quartzites in both directions along the strike after

lying in the limestone for over 400 feet. Other faults

of this system rigorously follow a given limestone.

l>erhaps the most striking example is furnished by the

"Galena King gouge," a brecciated and highly altered

zone due to shearing and subsequent mineralization of

the limestone. The" Galena King gouge" has been

recognized from the Argent mine, the most easterly

development of the district, almost to the Muerbrook

fault, which cuts off the" Galena King" limestone at

the mouth of Southport Gulch. Through practically

all of this distance of nearly 1112miles the" Galena

King" limestone carries this "gouge" or fault zone,

in some places near the footwall of the bed, elsewhere

near the hanging wall. The" Hercules" limestone in

much of the workings of the Honerine mine shows

similar shearing and in places is even completely cut

out by faulting subparallel to the bedding. Similar.

faults have been observed in the" Honerine " limestone

near the Palace ore shoot and at the 105 crosscut, as

well as farther east at the Wier stopes, all on the

1,200-foot level. These and other east-west faults will

be discussed in detail in the mine descriptions, as they

are of merely local importance.

As all the faults just mentioned are practically bedding faults and antedate the dike intrusions, it is quite

out of the question to prove the amount of movement

on any of them. It seems likely, however, in view of

the very moderate amount of brecciation that accompanied the faulting, as well as the rather remarkable

persistence (with few exceptions) of each fault within

a single bed, that the displacements have been very

slight and merely such differential movements as must

necessarily occur between competent beds in folding.

The practical restriction of the faults to the limestones

may be accounted for by the relative incompetence of

the limestones as contrasted with the strong quartzites

between which they lie. On this assumption the faults

are contemporaneous with the folding. Similar faults

may have been formed in the quartzites, but inasmuch

as the mine workings have been confined as much as

possible to the limestones, little opportunity was offered to determine the existence of strike faults in

the quartzites, and surface indications of such faults

are lacking.

The second fault movements took place on the northsouth system and are of greater economic importance

than any others recognized in the district. An attempt was made in the field mapping to portray these

faults, but the scale of the map (pI. 12) is too small

to reveal them without confusion, and therefotre they

are not shown. However, a careful study was made

of the displacements of the" Galena King" limestone

from the Argent mine to Rush Valley, and in that

interval eight faults of measurable displacement were
seen, and it is quite certain from underground explorations that fissures of this system upon which greater

or less displacement has occurred are to be numbered

by scores, if not by hundreds.

Inasmuch as the beds dip between 60° and 80°

throughout this part of the mining area and the faults

are practically dip faults, it is more convenient in

this report to refer to the displacements due to these

faults in terms of the horizontal separation of the

strata than in any other way.

The" Galena King" limestone is faulted in the gulch

just west of the Argent mine, the west block being

displaced to the north about 150 feet. Another fault

cuts it on the east slope of the hill in which is situated

the No You Don't tunnel, and here too the west block

is displaced to the north about 190 feet. Two small

faults, each of which offsets the" Galena King" limestone about 5 to 10 feet, occur on the crest of the hill

above the No You Don't tunnel. On each the west

block is displaced to the south relative to the east

block.

Exposures of the "Galena King" limestone are

poor west of the No You Don't tunnel, but the" Paisley" limestone just up the gulch to the north shows a

displacement of 40 feet, due to a fault in the bottom

of the gulch, the ,west block having moved south with

reference to the east block.

There is no evidence of noteworthy faulting between

this point and the Palace crossing, on the hill east of

the Galena King mine, and although some of the

mining men believe that the Palace crossing is a fault

with a displacement at this point of several scores of

feet, the writer could find no indication on the surface

that it has any such displacement. Indeed, comparison of the maps of the 300-foot level of the Galena

King mine with the surface geology seems to offer

strong reasons for questioning the existence of any

large displacement on this fault here. Yet a denial

of the possibility is certainly not warranted, in view

of the poor exposures at the critical locality and the

demonstrated fact that several faults of this system

are rotational, with displacements varying widely from

one level to another as well as along the strike. Thus

the Palace fault, a thousand feet or so to the south of

this point, has a horizontal offset of 40 feet on the

600-foot level of the Honerine mine, the west block

being stepped relatively north, while on the 1,200-foot

level no offset at all is to be found in the Honerine

drift, and the west block is stepped south 8 feet relative to the east block in the St. Patrick drift.

No faults were seen to offset the "Galena King"

limestone between the Palace crossing and the west

end of the Joe Pull stope of the Galena King mine.

At this point the "Galena King" bed on the west

block is displaced 20 feet to the south, referred to the

east block, but the fault is a scissors fault, because

on the 300-foot level of the Galena King mine the

displacement is about 30 feet in the opposite sense.

Another small fault offsets the "Galena King"

limestone in the gulch just northeast of the air shaft

of the Honerine mine and displaces the west block

about 20 feet to the north.

The next fault observed was across the gulch west

of the Tiptop tunnel of the Stockton Lead Co., where

the west block is displaced a few feet to the north.

No other faults were observed between the one just

mentioned and the point where the "Galena King"

bed passes beneath the alluvium, but there can be little

doubt that many other small displacements occur.

The Muerbrook fault must be beneath the alluvium,

only a few scores of feet from the contact with the

bedrock.

The Muerbrook fault probably has a much greater

displacement than any of the other north-south faults.

Unfortunately, surface exposures are far from satisfactory along the low foothills where this fault occurs,

and underground the relations are obscured by igneous

intrusion and the accompanying metamorphism of the

sedimentary rocks along the line of the Honerine drain

tunnel. But the drag exhibited by the "Larsen"

limestone west of the Muerbrook mine and by the

" Paisley" limestone just north of Southport Gulch is

very strong, in the sense suggesting a movement of

the west block to the south relative to the east block.

Just south of the Black Diamond shaft, west of the

portal of the 600-foot level of the Honerine mine, is

an outcrop of cherty limestone over 60 feet thick.

The only limestone of this character and thickness observed in the entire mining area is the "Paisley"

limestone, and the projection of this bed to the drainage-tunnel level makes it seem almost certain that the

limestone cut by the drain tunnel west of the Bullion

crosscut is the "Paisley" bed and that the Bullion

mine is in the " Galena King" limestone rather than

in the " Honerine " limestone, as has been assumed by

many of the mining men of the district. This interpretation is supported by the character of the section

penetrated by the Bullion crosscut and has been arrived at independently Oy Mr. W. A. Young, of the

Combined Metals Reduction Co., and the writer. According to this interpretation, the Muerbrook fault has

!l; displacement of about 800 feet, the west wall having

moved south relative to the east.

Innumerable other north-south faults of varying

throw are to be seen in the mines, but their discussion

can more profitably be deferred to the individual mine

descriptions. It can not be safely assumed that all

these faults are of the same age, as there has been

later movement on faults of this system. However,

inasmuch as the great majority of the numerous por-
phyry dikes of this district trend parallel to these

faults and some, if not all, of them occupy fault fissures, it is inferred that the larger faults are older

than the porphyry intrusions and probably are essentially contemporaneous, and that they are all younger

than the east-west faults.

There is evidence in the Honerine mine of at least

two periods of faulting later than the porphyry intrusions and earlier than the mineralization. The first of

these periods is represented by small north-south

faults and shear zones within and cutting along the

contacts of porphyry dikes. No satisfactory measure

of the displacement along these faults was obtained,

but all appear to be minor.

Still later additional movements occurred on some

of the east-west faults. These resulted in minor displacements, the observed maximum being 60 feet, cutting porphyry dikes and postporphyry north-south

fissures, usually setting the blocks south of the faults

westward compared to the blocks north of the faults.

All the above-described faults of the Stockton mining area are older than the mineralization, as shown

by the presence in all of undisturbed sulphides.

Locally there is some suggestion of postmineral faulting as well, but no evidence was discovered that any

postmineral movements were very great. The few I

occurrences of sheared sulphides are discussed in the

descriptions of the mines. The fact that the scarp

north of the Stockton Standard prospect, which may

be due to Basin Range faulting, is on the strike of the

Muerbrook fault has led to the suggestion (p. 84) of

possible rejuvenation of movement on this fault in late

Tertiary or Quaternary time. With this possible exception it seems likely that nearly all the faults date

back to the time of folding and igneous intrusion,

presumably early in the Tertiary period.

To summarize the sequence of faulting in the vicinity of Stockton: The earliest faults are bedding faults,

presumably accompanying the folding. These were

followed by north-south faults formed presumably by

subsequent tensional forces. After intrusions of monzonitic porphyries minor north-south and later eastwest faulting occurred, perhaps because of readjustments of the roof of a larger magma reservoir below.

These faults were followed by the mineralization.

Minor postmineral faulting has occurred locally, and

possibly the Muerbrook fault was rejuvenated at the

time of Basin Range faulting.

SUMMARY OF GEOLOGIC HISTORY

The geologic history of the southern Oquirrh Mountains, as far as it can be deciphered from evidence

obtained within the Stockton and Fairfield quadrangles, begins with the area depressed beneath the

Lower Cambrian sea and receiving coarse sandy deposits, now represented by the Tintic quartzite. The

purity of the quartzite and the absence of shaly detritus or evidence of local channeling support the interpretation that the sedimentation was marine rather

than continental.

Toward the end of Lower Cambrian time the area

became further depressed, so that instead of receiving

coarse sand it began to receive clay-now recognized

in an altered condition in the shaly part of the Ophir

formation. There is no evidence that the area was

exposed to erosion between the Lower and Middle

Cambrian epochs. On the contrary, it was probably

somewhat depressed, or at least was no longer subject

to detrital accumulation but began to receive limy

deposits. At first these alternated with clayey deposits, as in the upper part of the Ophir formation,

but later the contributions of clay were greatly

diminished, so that the lime deposits were only slightly

argillaceous. The deposits of this part of Middle

Cambrian time are now represented by the Hartmann

limestone.

In later Middle Cambrian time an unusual contribution of clastic material, now represented by the

basal shale of the Bowman limestone, was received,

owing probably to change in relation to the shore line,

as indicated by the repeated occurrence of intraformational conglomerates. Several minor repetitions of

clay deposition occurred later, but finally the accumulation of limy material again prevailed. If, as has

been suggested by several writers, dolomite is derived

by the reaction of newly formed calcium carbonate

sediments with sea water and hence is favored by

slower sedimentation, the area, although still subsiding, did so at a considerably slower rate in the time

represented by the Lynch dolomite.

No apparent break in sedimentation occurred between Middle and Upper Cambrian time in this area,

and it seems highly probable that conditions continued without change.

Evidence is lacking as to conditions prevailing

within the area in the interval between Upper Cambrian and Middle Devonian time. The area may have

been the seat of deposition during Ordovician time, as

at Tintic, but if so, it was exposed to erosion before

the Middle Devonian. It is highly probable that the

area was land during the Silurian period. The sea

again transgressed over the area probably in Middle

Devonian time, depositing as a basal layer a thin

veneer consisting largely of reworked Cambrian dolomite but containing little clastic material. The deposition of dolomite was almost immediately resumed,

but whether it continued into the Upper Devonian or

not is uncertain. Upper Devonian beds do not occur

in the area, but they may have been deposited and

later removed by erosion.
At some time between the Middle Devonian and the

Mississippian the area was uplifted to form a land

mass, and upon it was developed a sink-hole (karst)

topography in the Jefferson (?) dolomite. The

Mississippian submergence that followed was unaccompanied by clastic deposition. Limestone was

formed under conditions extremely favorable for invertebrate life, for the deposits of lower Mississippian

age carry profuse fossils. It is uncertain whether or

not there was an emergent interval between the lower

and upper Mississippian, but the phosphatic shales at

the base of the Deseret limestone doubtless represent a

considerable interval of very slow accumulation.

The area was submerged and sinking at roughly the

same rate as the limy sediments accumulated through

most of upper Mississippian time, but during a shod

interval, represented by the Humbug formation, shallower water or stronger currents than usual prevailed

and permitted the accumulation of much sandy detritus. Somewhat later, after a time of lime deposition,

more clay was deposited, fOirmingthe I"ong Trail shale

member.

Toward the end of Mississippian time, after a long

time of depression, concomitant with sedimentation,

the rate of accumulation of sediments overtook that of

depression, so, that shallower water prevailed. The

sediments became dominantly clastic, chiefly clay but

with some sand. It is possible though not certain that

the area was emergent for a time. At any rate the

early Pennsylvanian sediments are very similar to

those of the late Mississippian, both probably connoting shallow-water conditions.

The Pennsylvanian was an epoch of very marked

depression. At first the depression was probably

rather slow, although the area was probably always

Lelowwave base. Later, despite the deposition of vast

amounts of sand, aggregating many thousands of feet

in thickness, which must necessarily have been laid

down rapidly and in a relatively shallow sea, there

,,-ere interbedded marine lime sediments, which testify

to the area having been constantly submerged. This

must mean a very rapid depression.

No sedimentary record of the interval between the

Pennsylvanian and Tertiary is to be found in the

Stockton and Fairfield quadrangles. However, the

presence of Permian, Triassic, and Jurassic rocks in

considerable thickness in the Park City district,lS about

~iOmiles to the east, suggests that at least during part

of this time the site of the southern part of the Oquirrh

Mountains was receiving deposits. It was probably

emergent during most of Cretaceous time, however.19

18 Boutwell, J. M., and Woolsey, L. H., Geology and ore deposits of

the Park City district, Utah: U. S. Geol. Survey Prof. Paper 77, pp.

49-59, 1912.

,. Spi~ker, E. M., and Reeside, J. B., jr., Upper Cretaceous shore line

in Utah: Geol. Soc. America Bull., vol. 37. pp. 429-438, 1926.

67463-32--7

At the end of the Cretaceous or in early Tertiary

time the region was compressed in an east-northeast to

northeast direction, and the rocks were thrown into

large, rather open but somewhat asymmetric, folds

with steep northeast flanks. A certain amount of

shearing and minor faulting took place during this

folding.

After erosion had carved the folded rocks into a

somewhat dissected, perhaps even mountainous topog-

.raphy, volcanism ensued, probably in Eocene time.

The first volcanic products were breccias and tuffs of

considerable thickness, with subordinate flow~. The

flows became more abundant later in the volcanic history. Although other rocks occurred, latites were predominant, apparently throughout the volcanic activity,

at least so far as it is recorded in the rocks preserved

to the present time. The irruptive magma finally

penetrated even into the previously built volcanic piles.

Rhyolite and latite volcanic plugs were' intruded and

probably added their ejecta to the older flows. Where

the magma failed to reach the surface it consolidated

into monzonitic rocks.

Probably the force of igneous intrusion was in

some places effectivein rupturing the previously folded

rocks. Perhaps the large faults at Ophir are results

of this force. At any rate, after the emplacement of

the igneous rocks emanations given off by them, probably chiefly in the hydrothermal condition, brought

about considerable metamorphism within the previously faulted rocks, leading finally to deposits of gold,

lead, silver, zinc, and copper.

The Oligocene and early Miocene were presumably

uneventful periods of erosion with, possibly, the deposition of some coarse grit beds (now represented by

fine conglomerate) in low parts of the area. The result of this erosion was the production of a subdued

mature surface at the site of the present Oquirrh

Mountains. Either in the late Miocene or in the

Pliocene epoch faulting began which has continued to

the present day. Some of these faults, which are the

cause of the topographic prominence of the present

range, were probably rejuvenations of earlier breaks

dating from the early Tertiary, but others were probably newly formed.

The result of these faults and the accompanying tilting movements has been the rotation of a huge block

of the crust, with the uplift of the west edge of the

Oquirrh Mountains. Erosion consequent upon this

uplift has carved the range deeply, largely destroying

the previous mature erosion surface and producing the

present rugged topography. Erosion has gone on in

the mountains and huge alluvial fans have been built

out onto the valleys. Percolating ground water has

attacked the ore deposits, oxidizing the sulphides and

leading to some slight enrichment.
For the most part the valleys have been independent

basins, but during at least a brief h,umid time in the

Pleistocene they were united by the waters of Lake

Bonneville. There is some suggestion that some valley integration occurred through normal processes

before Lake Bonneville time.20 The small glaciers or

snow fields of the higher peaks of the range probably

were contemporaneous with the existence of Lake

Bonneville. Since Lake Bonneville time the geologic

history of the area has been uneventful, with continued erosion in the mountains and deposition in the

valleys.

ROCK ALTERATION

PROCESSES

The mineralogic and textural modifications which

the rocks of the Stockton and Fairfield quadrangles

have undergone subsequent to their cementation and

consolidation are included under metamorphism, or

the changes which occur below the border zone between the lithosphere and the atmosphere and hydrosphere,21 and weathering, which occurs in the border

zone between the lithosphere and the atmosphere and

bydrosphere.

Metamorphism has been of two varieties-dynamic

and igneous. To the action of dynamic metamorphism are ascribed such features as fault breccias,

which are common throughout the area, and the schistosity of the lower beds of the Ophir formation.

Under igneous metamorphism are included all the

changes, chemical, textural, or mineralogic, which

have been effected in the rocks by the igneous intrusions and the deep-seated solutions associated with

them. Among such changes the most ,important economically has been the formation of the valuable mineral deposits of the area. Igneous metamorphism includes the changes brought about in the country rock

and the postconsolidation changes within the intrusive

itself. Systematic study of metamorphism by many

investigators has resulted in the common recognition

of two varieties of igneous metamorphism of the country rocks of an intrusive mass-(l) "normal" metamorphism, involving changes brought about without

significant addition of material to the country rocks

from the magma; (2) metamorphism involving transfer of material from the magma chamber to the wall

rocks. The variety of igneous metamorphism involving material transfer includes what have been called

pneumatolytic and hydrothermal metamorphism. The

terms "pneumatolytic" and "hydrothermal" imply

knowledge of the phase, gaseous or liquid, through

which the material transfer occurs. Inasmuch as such

'" Gllluly, James, Possible desert-basin integration in Utah: Jour.

Geology, vol. 37, pp.672-682, 1929.

21 This Is the definition of Grubenmann and Niggli (Die Gesteinsmetamorphose, p. 179, Berlin, 1924).

knowledge is rarely available and evidence bearing on

it is rarely unequivocal, the writer agrees with Ross 22

that the term" pneumatolytic" is better avoided. As

the same arguments apply, though less forcefully,

against the term "hydrothermal," the present writer

believes it best to avoid this term also. In view of the

uncertainties as to the criteria of phase relations during metamorphism the noncommittal term" solution"

if"preferred, without reference to whether the solution

is in the gas or the liquid phase. The reasons adduced by Ross seem to compel the belief that truly

" hydrothermal" solutions are more important than

gas-phase reactions, but the writer does not wish to

deny a certain effect to both.

Weathering includes the decomposition and leaching

of rocks and ores at and near the surface and the

changes involving the deposition at lower levels of the

materials taken into solution. Such changes have locally been of considerable importance in separating

zinc from lead ores, but on the whole they are not, in

this area, of great economic significance.

DYNAMIC METAMORPHISM

Dynamic metamorphism has been rare in the Stockton-Fairfield area. In the description of the Ophir

formation on page 11, mention is made of the schistose

texture of some of its lower beds as evidence of dynamic metamorphism, perhaps due to the folding of

the beds under great pressure. None of the other rocks

of the area exhibit any of the characters of dynamic

metamorphism and recrystallization, however.

The fault breccias that are so common in the western

part of the range are due to friction during the fault

movement and crushing of the rocks. Most of them

consist of angular fragments of the bordering rock

an,d are of little special interest, but one exposed on

the No.3 level of the Muerbrook mine, at Stockton, is

noteworthy as containing well-rounded quartzite

pebbles ranging from half an inch to 3 inches in

diameter. The rock of these pebbles is almost surely

derived locally from the walls of the fault, but the

remarkable smooth rounding which they have undergone seems noteworthy.

It is possible that the sericitic gouge which occurs

along many faults at Ophir, in Dry Canyon, and in

the Stockton district is to be attributed to purely

dynamic metamorpshim, but inasmuch as all three of

these areas have been subjected to intense activity of

circulating solutions which closely followed the igneous intrusions, and there is elsewhere evidence of sericitization by these solutions in the absence of dynamic

action, it seems more likely that this sericite along the

faults is a product of igneous metamorphism also.

ll2 Ross, C. S., Physico-chemical factors controlling magmatic dill'erentiation and vein formation: Econ. Geology, vol. 23, p. 869, 1928.
Igneous metamorphism as here defined includes all

the mineral and textural transformations induced in

the solid rocks by the intrusion of an igneous body

and the after effects of the intrusion. These alterations are, at least in this area, effected chiefly by the

thermal changes due to the intrusion of the highly

heated igneous mass and its subsequent 900ling and by

the chemical changes due to the circulation of highly

heated fluids containing material in solution through

the rocks. The more influential of these factors in this

area has been the transfer of material and heat by

circulating fluids as an after-effect of the intrusion.

Metamorphism due to an igneous body is in general both endomorphic-that is, effective within the

igneous rock itself-and exomorphic-that is, occurring within the inclosing country rocks. Strictly endomorphic alterations in this area have been slight,

most of the metamorphism even of the igneous rocks

having been effected by solutions derived from deeperlying bodies of intrusive rock.

There have been four chief varieties of alteration of

the igneous rocks of the Stockton and Fairfield quadrangles. These are propylitization, sericitization,

silicification, and zeolitization.

Propylitization, which involves the alteration of the

mafic minerals to chlorite, epidote, and carbonates,

the alteration of feldspars to epidote, carbonates, and

sericite, and the introduction of pyrite, has been common near the ore deposits of the quadrangles, especially in the immediate neighborhood of ore-bearing

fissures. The" Birdseye" porphyry exhibits alteration of this type near the mines on Lion Hill. Propylitization has occurred to a much less extent in the

monzonitic rocks of Soldier Canyon but has been the

dominant variety of alteration in the Stockton mining

area, where hardly a specimen of porphyry can be

found that shows no evidence of at least incipient alteration, whereas the more highly mineralized rocks,

as in the Honerine mine, have had their dark minerals

completely replaced by actinolite, epidote, chlorite,

and calcite. The feldspars of these rocks are less altered except immediately adjacent to the mineralized

fissures, where the plagioclase has been completely

altered to epidote, clinozoisite, sericite, and calcite, although some sericite and carbonate are found in all

the specimens collected in the mine. Impregnation

with pyrite has been intense.

Sericitization, in which sericite, the fine scaly or

silky variety of muscovite, is developed almost to the

exclusion of chlorite, etc., has been common throughout the region. The Eagle Hill rhyolite at Mercur,

the dike west of Ophir, and the rhyolite cut in the

Hidden Treasure and Mono mines are all considerably

sericitized. In the Stockton mining area some of the

gouge clays along mineralized fissures in the poryhyry

dikes consist chiefly of sericite. At some places on

Lion Hill the "Birdseye" porphyry has been altered

to a white chalky rock which the microscope shows to

be a mass of quartz and sericite, heavily impregnated

with pyrite. In all these places the plagioclase seems

to have been altered most readily to sericite, while the

dark minerals have been changed to calcite or chlorite

aggregates. More severe alteration results in the replacement of orthoclase by sericite, though this has

gone to completion only in small areas. Pyrite and

locally quartz, as in the rhyolite in the Hidden Treasure mine, have been introduced at the same time as the

sericite. Most specimens show considerable calcite

also. Unfortunately, all the specimens that were collected as representative of sericitization had been subject to considerable weathering, with the production

of gypsum, iron hydroxides, and clay minerals, so that

details of the sericite alteration have been obscured.

However, the close association of sericite, epidote, and

chlorite in the igneous rocks of the Stockton area indicates much similarity in the composition of the solutions which produced at one extreme a sericite-pyritequartz rock and at the other a chlorite-epidote-calcitepyrite rock with subordinate sericite and with remnants of quartz and feldspar.

Silicification has not been extensive in most of the

intrusive rocks of the area, although some quartz has

been introduced along the contacts and in joints in the

Eagle Hill rhyolite at Mercur as well as in some of

the altered monzonitic rocks in the Honerine mine.

Silicification accompanied sericitization in the rhyolite

vf the Hidden Treasure mine. The rhyolite breccia

plugs east of Tickville Gulch have undergone very considerable silicification, some of which may, however, be

due to weathering only.

Zeolitization has affected only one of the intrusive

masses studied-the diorite stock in the east fork of

Settlement Canyon. Here late magmatic or hydrothermal reactions have resulted in the replacement of

plagioclase and orthoclase crystals by analcite and

thomsonite. Narrow veins cutting through the rock

have also been filled by these zeolites. The development of zeolites has been widespread in the lava and'

breccia flows of the Fairfield and Stockton quadrangles. Hot solutions expelled from the lavas themselves (with possibly some meteoric waters) have traversed the rocks and deposited zeolites, chiefly analcite,

thomsonite, natrolite, and phillipsite, in innumerable

cavities and fissures
METAMORPHISM: OF THE QUARTZITES, SANDSTONES, AND

SHALES

Igneous metamorphism of the coarser-grained sedimentary rocks of the Stockton and Fairfield quad1'angles has in general not been great. Near the monzonitic intrusive rocks of the Soldier Canyon area,

where the most intense alteration has occurred, the

sandstones and quartzites of the Oquirrh formation

show considerable bleaching close to the contacts. In

places the bleached zone is 20 or 30 feet wide, especially near the larger masses, although 5 or 10 feet is a

more usual measure. Brecciation is common in such

sandstone border zones.

Under the microscope these rocks commonly show

some enlargement of the quartz grains, though not

significantly more than other quartzites not altered by

igneous intrusion. Calcite cement between the quartz

grains has locally been replaced by diopside and sericite. Nests and veinlets of microcrystalline quartz

also occur as metamorphic products. Locally sericite

is developed, replacing quartz and detrital feldspar

grains. In one specimen the limy cement of the sandstone has been altered, with the formation of a darkgreen pleochroic hornblende which penetrates and

replaces quartz grains. Fractures through the rock

are filled with calcite and, in one specimen, lined with

a zeolite whose optical properties correspond with

those of epidesmine.

In the mines at Stockton the alteration has been

considerably greater. A very light gray fine-grained

quartzite at the contact of the "Raddatz" porphyry

near the Honerine air shaft shows bleaching and the

development of considerable sericite. A hornfels in

the Bullion crosscut of the Honerine mine shows, in

this section, pronounced fine banding. Rounded clastic quartz grains forming some bands are surrounded

by a matrix of calcite and orthoclase, and the intervening bands, which were probably higher in calcite cement, have been altered tOIirregularly and finely intergrown orthoclase, sericite, epidote, and garnet., Diopfoideis common in the altered sandstone penetrated by

this crosscut. The rock is cut by calcite veinlets in

many directions. The sandstone footwall of the " St.

Patrick" limestone commonly sholws the development

of diopside, orthoclase, and colorless chlorite with a

little sericite, at the expense of the calcite cement.

The original rounded quartz grains of the sandstone

are but slightly attacked. A quartzite in the hanging

wall of the" St. Patrick" limestone east of the Hampden stope of the Honerine mine shows the clastic quartz

much recrystallized into a fine mosaic, and the cement

bas been altered to diopside, andradite, orthoclase, and

apatite. Euhedral calcite rhombs and rhombic crystals

of orthoclase (adularia) occur in the recrystallized

quartz, and pyrite impregnates the rock thoroughly.

A strongly dichroic and birefringent mineral with a

mean index of about 1.51 is very plentiful in the quartz

mosaic. This is probably beidellite, but its identity is

not quite certain. Detrital grains of zircon and microcline appear to have survived the metamorphism unaltered.

Examination of the immediate footwall of the

" Honerine" limestone at the Palace ore shoot on the

drain-tunnel level of the Honerine mine shows the

cement of the sandstone to have been altered, with the

production of diopside, orthoclase, and wollastonite.

Strongly pleochroic and birefringent epidote, apparently of the pistacite variety, occurs in some specimens. The rock is cut by veinlets of calcite, and

locally grains of calcite (w= 1.66) replace quartz.

Some garnet, probably of the variety andradite, as its

refractive index is clearly higher than 1.85, occurs

along these calcite stringers. The detrital quartz has

only locally been recrystallized into a fine mosaic.

Euhedral crystals of orthoclase (adularia) are sporadically distributed through the quartz aggregate. A

little sericite is present in most specimens. Pyrite

cubes occur rarely. Similarly altered quartzite of the

footwall of the " Honerine " limestone is also present

at the Knickerbocker crosscut of the Honerine mine.

The metamorphosed rocks just described occur only

in the mineralized area near Stockton and are nowhere

far from the fissures along which the ore deposits are

localized. There can be no question that the solutions

from which the ore deposits were derived and the solutions which induced these alterations in the near-by

sandstones were the same.

Similarly altered sandstone is to be seen in Drv

Canyon just above the portal of the Deseret inclin~,

where the rock is distinctly bleached. The calcite cement of the rock has been partly altered to diopside.

A small amount of orthoclase is also developed, as well

as some colorless chlorite. In this area the only igneous rocks exposed are rhyolite dikes and breccias.

The metamorphism of the sandstone and limestone in

Dry Canyon can not, however, be attributed to these

small igneous bodies, for they have produced no similar metamorphism in the country rocks with which

they are in direct contact. The alteration must be due

to emanations from deeper-lying igneous bodies, not

yet exposed by erosion.

No evidence of igneous metamorphism of sandstone

has been found farther south in the area except a little

sericitization along faults in the Tintic quartzite at

Ophir.

Igneous metamorphism has affected shale significantly only in the immediate vicinity of Ophir, for the

stratigraphic section contains few shale members and

in the rest of the quadrangles they are not associated
with igneous masses. In fact, only the limy shales

are altered to any considerable extent. Even at Ophir

the metamorphism is not to be ascribed to the small

dikes of rhyolite and lamprophyre now exposed.

Along the rhyolite dike west of Ophir the Ophir

formation shows little change even at the direct contact, where a little rearrangement of muscovite and

chlorite is the sole evidence of igneous alteration. The

metamorphism of the Ophir shales and the shaly members of the Bowman limestone in Ophir Canyon is

localized near the Cliff fault and the fissures extending southward from it. Accordingly it is to be attributed to circulating heated solutions traversing the

. rocks along these fissures from a deeper-seated igneous

mass.

The bed taken as the base of the Bowman limestone

is variable. It was originally a mottled limy mudstone with irregular shaly limestone facies. 'Where

least altered, on the east flank of Hartmann Gulch,

these facies are clearly recognizable. The dominant

facies is dense mudstone breaking with a conchoidal.

fracture. Even here there is evidence of some igneous

metamorphism, for the confused aggregate of muscovite (sericite) and quartz that makes up most of the

rock is penetrated by seams of pyrite and considerable

pleochroic tourmaline in brown to greenish-yellow

needles. As the bed is followed along the outcrop toward the Cliff fault, however, the metamorphism becomes increasingly evident. Reaction has occurred

between the more limy and the less limy facies of the

original rock, resulting, in some layers, in the segrega·

tion of calcite in irregular nodules embedded in silicate

minerals. This facies is illustrated in Plate 5, B.

Other beds of this basal member are dense, nearly

massive argillites showing only a faint banding

parallel to the bedding.

Under the microscope several varieties of hornfels

are recognized. The commonest variety is a dense

porcellaneous rock faintly banded parallel to the bedding with light gray and medium brown. The microscope shows the gray bands to consist of orthoclase,

in very minute serrate crystals, interlocking in a

mosaic of quartz, a little albite, and epidote. The

brownish layers are carbonaceous and carry fine grains

of epidote (pistacite), quartz, and chlorite. Gradations. occur in which orthoclase, epidote, quartz, chlorite, calcite, and carbonaceous matter are all finely

intergrown.

Thick beds of massive dense dark-brown hornfels

occur in this basal member of the Bowman. The microscope shows them to consist of a matted mass of

sericite without common orientation which contains

minute grains of orthoclase (locally forming an interlocking mosaic), quartz, and tourmaline and crystals

of rutile. The rutile is probably recrystallized sedimentary material, but the elongated needlelike tourmaline is undoubtedly of metamorphic origin. Another variety of hornfels is exceedingly fine grained

and consists of bands of quartz and feldspar, probably

all of sedimentary origin, separated by bands composed of minute aggregates of sericite, orthoclase,

pyrite, and calcite. It is evident on inspection of

hand specimens that the principal development of

epidote has occurred at the junction of layers of carbonate and siltstone, and this is confirmed by study

of thin sections. Minute tourmaline needles are ubiquitous but appear to be more numerous in the darker,

more carbonaceous layers than in the lighter ones.

In more limy portions of the member the calcite has

been recrystallized. Epidote of a bright-green pleochroic variety is very commoiIl,and diopside, tremolite,

chlorite, and subordinate garnet (probably andradite)

occur. Pyrite is prominent in this facies as well as in

the more shaly variety. In all the metamorphic rocks

pyrite occurs both disseminated and in veinlets that

cut through the other minerals and are undoubtedly

somewhat younger than most of the silicate minerals.

Some parts of the basal member of the Bowman

limestone show fairly even, very thin banding of more

silty and more limy layers. The more silty layers have

altered to a mass of epidote, orthoclase, and quartz in

which calcite is developed in flat tables parallel to the

base. The texture resembles very closely that of the

reticulated calcite common to many Tertiary veins.23

It seems probable that under conditions permitting the

formation of adularia the form of calcite tabular paraBel to the base is the more stable one.

Alteration similar to that olf the basal member has

occurred in higher shaly beds throughout the Bowman

limestone and, like that in the basal member, has been

progressively more intense near the Cliff fault.

The pure shales of the Ophir formation show evidence of igneous metamorphism only near the mineralized fissures, and here the sole effects are the development of a mat of sericite in random orientation and

a small amount of blue-green tourmaline. The purer

limestones and shales between which these altered

limy shales lie show little or no metamorphism except very close to the Cliff fault. It is evident, therefore, that the localization of metamorphism has been

governed mainly by the opportunity for intimate :reaction between calcite and clay minerals, although the

development of tourmaline, iron-rich garnet, and pyrite in the basal member of the Bowman limestone

implies the introduction of a minor amount of material from a magmatic source. The chief function of

the magmatic emanations, to which the metamorphism

was doubtless due, was to furnish the temperature and

23 Lindgren, Waldemar, Mineral deposits, 3d ed., pp. 521-524, New

York, 1!l28.
with igneous masses. In fact, only the limy shales

are altered to any considerable extent. Even at Ophir

the metamorphism is not to be ascribed to the small

dikes of rhyolite and lamprophyre now exposed.

Along the rhyolite dike west of Ophir the Ophir

formation shows little change even at the direct contact, where a little rearrangement of muscovite and

chlorite is the sole evidence of igneous alteration. The

metamorphism of the Ophir shales and the shaly members of the Bowman limestone in Ophir Canyon is

localized near the Cliff fault and the fissures extending southward from it. Accordingly it is to be attributed to circulating heated solutions traversing the

rocks along these fissures from a deeper-seated igneous

mass.

The bed taken as the base of the Bowman limestone

is variable. It was originally a mottled limy mudstone with irregular shaly limestone facies. 'Where

least altered, on the east flank of Hartmann Gulch,

these facies are clearly recognizable. The dominant

facies is dense mudstone breaking with a conchoidal.

fracture. Even here there is evidence of some igneous

metamorphism, for the confused aggregate of muscovite (sericite) and quartz that makes up most of the

rock is penetrated by seams of pyrite and considerable

pleochroic tourmaline in brown to greenish-yellow

needles. As the bed is followed along the outcrop toward the Cliff fault, however, the metamorphism becomes increasingly evident. Reaction has occurred

between the more limy and the less limy facies of the

original rock, resulting, in some layers, in the segrega"

tion of calcite in irregular nodules embedded in silicate

minerals. This facies is illustrated in Plate 5, B.

Other beds of this basal member are dense, nearly

massive argillites showing only a faint banding

parallel to the bedding.

Under the microscope several varieties of hornfels

are recognized. The commonest variety is a dense

porcellaneous rock faintly banded parallel to the bedding with light gray and medium brown. The microscope shows the gray bands to consist of orthoclase,

in very minute serrate crystals, interlocking in a

mosaic of quartz, a little albite, and epidote. The

brownish layers are carbonaceous and carry fine grains

of epidote (pistacite), quartz, and chlorite. Gradations. occur in which orthoclase, epidote, quartz, chlorite, calcite, and carbonaceous matter are all finely

intergrown.

Thick beds of massive dense dark-brown hornfels

occur in this basal member of the Bowman. The microscope shows them to consist of a matted mass of

sericite without common orientation which contains

minute grains of orthoclase (locally forming an interlocking mosaic), quartz, and tourmaline and crystals

of rutile. The rutile is probably recrystallized sedimentary material, but the elongated needlelike tourmaline is undoubtedly of metamorphic origin. Another variety of hornfels is exceedingly fine grained

and consists of bands of quartz andfelclspar, probably

all of sedimentary origin, separated by bands composed of minute aggregates of sericite, orthoclase,

pyrite, and calcite. It is evident on inspection of

hand specimens that the principal development of

epidote has occurred at the junction of layers of carbonate and siltstone, and this is confirmed by study

of thin sections. Minute tourmaline needles are ubiquitous but appear to be more numerous in the darker,

more carbonaceous layers than in the lighter ones.

In more limy portions of the member the calcite has

been recrystallized. Epidote of a bright-green pleochroic variety is very commOiIl,and diopside, tremolite,

chlorite, and subordinate garnet (probably andradite)

occur. Pyrite is prominent in this facies as well as in

the more shaly variety. In all the metamorphic rocks

pyrite occurs both disseminated and in veinlets that

cut through the other minerals and are undoubtedly

somewhat younger than most o,f the silicate minerals.

Some parts of the basal member of the Bowman

limestone show fairly even, very thin banding of more

silty and more limy layers. The more silty layers have

altered to a mass of epidote, orthoclase, and quartz in

which calcite is developed in flat tables parallel to the

base. The texture resembles very closely that of the

reticulated calcite common to many Tertiary veins.23

It seems probable that under conditions permitting the

formation of adularia the form of calcite tabular paraIlel to the base is the more stable one.

Alteration similar to that olf the basal member has

occurred in higher shaly beds throughout the Bowman

limestone and, like that in the basal member, has been

progressively more intense near the Cliff fault.

The pure shales of the Ophir formation show evidence of igneous metamorphism only near the mineralized fissures, and here the sole effects are the development of a mat of sericite in random orientation and

a small amount of blue-green tourmaline. The purer

limestones and shales between which these altered

limy shales lie show little or no metamorphism except very close to the Cliff fault. It is evident, therefore, that the localization of metamorphism has been

governed mainly by the opportunity for intimate reaction between calcite and clay minerals, although the

development of tourmaline, iron-rich garnet, and pyrite in the basal member of the Bowman limestone

implies the introduction of a minor amount of material from a magmatic source. The chief function of

the magmatic emanations, to which the metamorphism

was doubtless due, was to furnish the temperature and

2' Lindgren, Waldemar, Mineral deposits, 3d ed., pp. 521-524, New

York, 1928.
possibly the reacting medium necessary for the reaction betwen the minerals already present in the rock.

It is evident that there can be no sharp line between

the metamorphism of a shale containing large quantities of lime and that of a limestone containing large

quantities of silt. The Ophir formation contains both

varieties, as well as the practically pure shale already

described, but for convenience of treatment both of the

lime-rich varieties are discussed below, in the section

on metamorphism of the limestones.

Metamorphism of the limestones in the Stockton

and Fairfield quadrangles has been localized in comparatively small areas. In general these are the areas

in which the mineral deposits occur. Thus metamorphosed limestones are present near Sunshine, Mercur, West Mercur, Lion Hill, Ophir Canyon,. Dry

Canyon, and Stockton-all localities in which ore

bodies have been worked. Some metamorphism has

also occurred near the igneous bodies of Soldier Creek,

Settlement Canyon, West Canyon, and Tickville

Gulch, where no commercial mineral deposits have

yet been developed.

In the northerly areas the metamorphosed limestones are closely and directly associated with exposed

igneous intrusive rocks, but from Bald Mountain

southward such an association is not marked, although

igneous rocks are found in small quantity in this part

of the range. It is noteworthy, however, that ore deposits and altered limestones in general are confined

to portions of the range where at least small bodies

of igneous rock occur and are absent where igneous

rocks are absent, although many igneous rock bodies

have been without significant effect on their inclosing

sediments, and many altered masses of limestone are

not in direct contact with visible intrusives.24

The limestone strata of the area vary notably in

susceptibility to alteration. Of the pre-Carboniferous

limestones only those of the Ophir formation have

been notably altered to lime-silicate masses and ore

minerals. The Hartmann limestone shows the sporadic development of tremolite crystals, but ore bodies

have not yet been found in any of its beds. The Bowman limestone carries a few small sulphide bodies near

the Cliff fault and on the Admiral Dewey claims, but

the chief metamorphism of this formation has been

confined to the shaly members, whose alteration has

already been described. It is true that the alteration

of these shaly beds has involved reactions with limestone contained in them, but there has been no significant alteration of the purer limestone beds of the rest

of the formation. The Lynch dolomite and Jefferson

•• Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof.

Paper 111, p. 372, 1920.

(?) dolomite have been metamorphosed only very

slightly. The striking susceptibility to alteration of

thelimestones of the Ophir formation is in remarkable

contrast to that of the higher beds whose superficial

aspect is almost identical. The same especial susceptibility of these rocks has been observed in the

East Tintic district, to the south, and in the Cottonwood district, in the Wasatch Range, where great Ol;e

bodies have been develc>pedin them.

Of the Carboniferous rocks, the basal few feet of the

Madison limestone is much more susceptible to alteration than most of the rest of the formation. Large

ore bodies have also been found, however, close to the

top as well. The Deseret limestone only locally shows

metamorphism, and the same is true of limestones

within the Humbug formation. Metamorphism and

accompanying ore deposition in the" Great Blue" limestone haw been confined chiefly to the portion belo.w

the Long Trail shale member, although in a few sIllall

areas alteration has occurred in the higher beds. A

. few of the thin limestone beds in the Manning Canyon

shale are locally metamorphosed in Soldier Canyon.

The susceptibility to alteration of the numerous limestones of the Oquirrh formation varies greatly. The

selective replacement of certain limestone beds by ore

minerals while adjacent beds bear none is very marked.

The following partial analyses of specimens from the

Honerine mine are given by Butler: 25

Partial analY8e8 of the" Honerine" lime8tone and the overlying

" dolomite"

Si0

2

_

CaO _

MgO . _

2.39

53.85

.53

42. 12

29.20

7.29

Unfortunately, the exact localities from which these

specimens were collected are not given, and although

it is obvious that the "Honerine" limestone is essentially pure, computation shows that the lime and magnesia of the "dolomite" can not all be combined with

carbon dioxide but must be in part in silicates. Accordingly, the" dolomite" analyzed is not an unaltered

rock but has already been somewhat metamorphosed.

It is probable that the rock is like the white metamorphosed sandstone described on page 94, but with a

lower content of sedimentary quartz. Much of the

magnesia and lime is probably present in the analyzed

rock as diopside, wollastonite, or garnet, which characterize the altered sandstones from the Honerine

mme. Nevertheless, the statement of Butler 26 that

2. Butler, B. S., The ore deposits of Utah: U. S. Geol. Survey Prof.

Paper 111, p. 174, 1920.

26 Idem, p. 174.
other than purely structural weakness or fissuring of

the rock, such as controls the emplacement of sills. It

is, however, quite certain that there is no relation between the distribution of the jasperoid and a supposed

sill of Eagle Hill rhyolite, as stated by Spurr.27 In

fact, of all the varieties of metamorphism recognized,

the alteration to jasperoid shows the least direct relations to the igneous bodies. Certain masses of jasperoid, however, particularly on Rover Hill, are associated with distinct fissures.

The contacts of the jasperoid masses against the

country rock are in all observed places distinct and

sharp, without transition. Two varieties of silicification associated with ore deposits have been recognized

Ly Irving 28-one in which the limestone is replaced

by the silica through the gradual increase in number

of sporadic isolated crystals of quartz and one in which

the silicification advances as a wave through the limestone, replacing all the rock as it progresses, thus leading to abrupt contact against the country rock. It is

this second and by far more widespread type of silicification that the jaspero~ds of the Stockton and Fairfield quadrangles represent.

All the jasperoid masses are characterized by jagged

brown-stained outcrops. The most casual examination

reveals their thoroughly brecciated character. It is

doubtful whether a single piece as large as a cubic foot

('ould be found free from slickensided surfaces or shear

planes. Some faint suggestions ocfbedding occur locally, but the fragments exhibiting them rarely if ever

conform in attitude to the bedding of the country rock.

On the contrary, the laminated fragments are jumbled

at all angles. Sporadic angular masses of limestone as

much as 3 or 4 feet on a 'side are embedded in the

jasperoid. Much of the jasperoid is broken into, angular fragments an inch or less in diameter, forming a

rubble that has been cemented into a firm rock. Otherwise massive portions of the rock show" drusy" cavities, invariably ('oated with white crystalline quartz

and commonly filled with coarse calcite. Locally,

smooth slickensides as much as 30 feet long cut through

the mass. There is no system to be found in these

slickensides, as they lie vertically, horizontally, and at

any angles between these limits. Many are curved

through an arc of nearly 90°. In addition to these

larger shear surfaces there are numerous shorter ones

which abut sharply against others and terminate.

None of these shear surfaces were observed to cut the

contact with the country rock, however.

Hand specimens of the jasperoid are light to dark

gray or even black and very fine grained to dense,

some resembling fine-grained quartzite and some

27 Spurr, J. E., Economic geology of the Mercur mining district,

Utah: U. S. Geol. Survey Sixteenth Ann. Rept., pt. 2, p. 383, 1895.

28 Irving, J. D., Replacement ore bodies and the criteria for th-'ir

recognition: Econ. Geology, vol. 6, PP. 555--559, 1911.

chert. The fracture is correspondingly hackly or conchoidal. Larger masses are chiefly breccias or, if not

hrecciattld, vuggy. The breccia fragments are cemented and veined hy white quartz with comb structure. This white quartz is commonly accompanied

by barite, either massive or as platy crystals. Many

i"pecimensshow rebrecciation of the rock and a third

generation of quartz that veins and replaces the

brecciated baritic jasperoid. Other specimens show

brecciation of the early quartz, with its fragments

coated by comb quartz and the interstices filled by

dark-brown calcite which bears euhedral barite plates.

Locally radiating masses of stibnite as much as 6

inches long occur. At other places the vugs of the

rock are lined with aragonite in long needles.

Under the microscope the jasperoid shows considerable diversity. Two varieties are most common.

One, illustrated in Plate 14, 0, D, is an aggregate of

anhedral quartz crystals, all very minute, usually less

than 0.03 millimeter in diameter, containing small

quantities of apatite and zircon and rather larger

quantities of blue-green, strongly pleochroic tourmaline, muscovite plates, and calcite crystals. Epidote,

in some specimens in beautiful euhedral crystals, is

also common. The quartz granules are all clear ex-

('ept where penetrated by the muscovite plates, and

the other minerals occur in general interstitially. This

variety is fully 95 per cent quartz.

A second variety (pI. 14, A, B) has the texture

known as the" typical jasperoid "texture. It consists

of intergrown quartz grains with a strong tendency

to euhedral forms, so that in thin section most of the

grains appear bounded by straight lines, and numer"

ous hexagonal and prismatic crystal outlines are present. In some sections the grains are outlined by carbon inclusions; in others they inclose zones of carbonate and epidote crystals. Some sections show secondary enlargement of quartz crystals outlined by

such inclusions. Of course, mutual interference of

these crystals prevents completely euhedral development. The borders due to secondary enlargement are

rarely in perfect crystalline continuity with the main

parts of the crystals but almost invariably show wavy

extinction. This is apparently due to slightly differing orientation of adjacent segments of the external

quartz. There is no reason to suppose, however, that

such phenomena are due to mechanical deformation.

Tourmaline, sericite, carbonate, carbon, epidote, apatite, and zircon were all recognized in this variety of

jasperoid as 'well as in the anhedral variety. These

euhedral quartz grains average probably 0.15 to 0.2

millimeter in diameter, although locally the average

grain may be about 0.5 to 0.7 millimeter.

In places these two varieties of jasperoid blend into

each other. 'Vhere this relation is observed there is
commonly a crude wavy streaking in the anhedral

facies, which roughly follows the boundary between

them. With oblique illumination there is a strong

suggestion of colloform banding subparallel to this

boundary. Both varieties carry scattered spherules

of chalcedony or of quartz outlined by brownish stains

which are visible with parallel light but which disappear completely or at least show no crystallographic

control when studied under crossed nicols. (See pIs.

15, 0, D and 17, B.)

Commonly the anhedral Yariety of jasperoid shows

a rough streaking, either curved or straight, along

which, either continuously or in small lenses, clear

quartz of coarser grain and wavy extinction is developed, in company with barite plates, as shown in

Plate 16. These barite plates have gross outlines

characteristic of the mineral, but their actual contacts

with the quartz are almost invariably serrate and determined by the penetration of minute clear quartz

grains into the barite. Here and there divergent

masses of stibnite are developed in this variety.

Both the anhedral and the euhedral jasperoid show

brecciation and veining by clear colorless quartz,

which has strong tendencies to form comblike linings

of vugs and veins. This is illustrated in Plate 17, A.

Barite plates similar to those just described commonly

occur in these veins and vugs. The quartz has the

divergent extinction characteristic of "flamboyant"

quartz.29 Some of the breccia interspaces are filled

with coarsely crystalline calcite.

In a few specimens the jasperoid veined with comb

quartz shows further brecciation and veining by

brown-stained fine-grained anhedral quartz similar to

that described first. This variety of quartz, carrying

tourmaline, apatite, carbonate, and zircon, shows in

oblique light a very clear banding parallel to the walls

of the cracks in which it is developed. The banding is

not visible with crossed nicols. This aggregate of

brownish quartz and accompanying minerals replaces

the older quartz, barite, and calcite masses, penetrating them in wormlike shapes and corroding the already brecciated barite plates very greatly. The flow

lines along cracks in barite which it is penetrating

and replacing are seen in Plate 18, A. They do not

appear with crossed nicols. (See pI. ]8, B.)

To summarize, the hypogene minerals detected in

the jasperoid include quartz, chalce/lony, barite, calcite, muscovite, tourmaline, apatite, zircon, stibnite,

chalcopyrite, epidote, chlorite, carbon, and probably

hematite. No silver, arsenic, or lead minerals were

detected, although they are closely associated, presumably contemporaneous in origin with the stibnite,

and furnish the basis for the commercial importance

of this variety of alteration.

llIl Lindgren, Waldemar, Mineral deposits, 3d ed., p. 192, New YOrk,

1928.

Part of the interpretation placed upon the jasperoid

characters described above has been, almost of necessity, implied in their description. However, there are

great difficulties involved in the interpretation of the

relations observed and the in.ference from them of a

satisfactorily established sequence of events in the

formation of the jasperoid masses. One of the most

serious difficulties in the way of such an interpretation

is presented by the later recrystallization of the original minerals of the rock. One variety of this recrystallization is comparatively simple to understand,

though its quantitative evaluation is difficult. This

is the recrystallization of spherules of chalcedony to

nonoriented anhedral quartz granules. There is no

question that this is a common phenomenon, for it has

been observed in 6 slides of the 45 examined, and fully

half the rest show, though not unequivocally, suggestions of the same process. Another variety of recrystallization offers a greater difficulty to interpretation.

It involves the retention of the external form of comparatively large euhedral quartz crystals by aggregates of small, diversely oriented quartz grains. (See

pI. 15, A, B.) This may represent the replacement

of the large crystal by the small ones, a process for

which no chemical or physical reason is discernible;

or the recrystallization of the large crystal into the

confused aggregate of small ones, which is equally

difficult to understand; or, finally, the solution of the

quartz of the original crystal and the subsequent filling of the resultant vug by the finer quartz mosaic,

which seems likewise unreasonable, as the matrix of

the original quartz crystal is also quartz and would

hardly be expected to retain the cast of the dissolved

crystal long enough to permit the change. No solution of the enigma has been reached, but the fact of

the retention of the form of seemingly un distorted

quartz crystals by mosaics of small diversely oriented

grains is apparent and must throw doubt on any interpretations of the origin based upon the present grain

of the rock. However, within the limitations just

discussed, the following hypothesis of the origin of

the jasperoid is advanced.

The first stage in the formation of the jasperoid was

the replacement of the limestone by colloidal silica.

Direct evidence for this is limited to the spherules of

chalcedony and the associated wavy color banding,

both of which are considered metacolloidal. Where

crystallization ensued immediately after deposition

of this colloidal precipitate, the anhedral fine-grained

quartz rock was formed, but where eonditions favored

a more leisurely crystallization, the euhedral quartz

crystals grew and to a large ext\lnt excluded from

themselves the impurities present in the mass, resulting in coarser-grained aggregates of clear quartz outlined by the impurities. This process would presumably lead to the convexity of the contact of the euhe-
dral quartz areas against the anhedral areas and the

wavy lines of excluded impurities along this contact.

During the gel stage the mass was largely hydrous,

soft, and yielding, and upon beginning of crystallization a considerable loss of.volume ensued. The shrinkage of the mass due. to this process opened cavities,

either analogous to miaroles or continuous fissures, and

as a result the mass was brecciated. Into the cavities

thus formed and along bands whose relations resemble

the well-known diffusion bands of Liesegang and

which may have originated in a manner controlled by

a somewhat analogous process fresh siliceous material

gained access to the rock, in company with considerable barite. These minerals filled the crevices in the

rock due to brecciation, and there is considerable evidence that the barite locally replaced the gel as well

as the fine-grained anhedral metacolloidal quartz.

The evidence for replacement of the gel by barite is

illustrated in the specimen shown in Plate 16, A,

where a brecciated crystal of barite is embedded in

fine anhedral quartz showing no brecciation. The

easily identifiable plate form of the barite is considered evidence, though not conclusive, of its replacement origin, although the serrate borders are interpreted as indicating that the final crystallization

of the gel in which it is embedded was delayed

beyond the time of emplacement of the barite. Similar phenomena are common through the specimens examined. In some places there may be doubt that the

fine quartz aggregate in which the barite breccia is

embedded is older than the barite, and indeed in many

places there is evidence of a still later quartz generation which replaces the barite· breccia as a whole.

This is shown by the occurrence of brecciated barite

in which fine-grained anhedral quartz is injected, as

indicated by flow lines visible in oblique light, as

illustrated in Plate 18. But in the examples previously described this possibility seems excluded by

the fact that the fine aggregate containing the brecciated barite is apparently continuous with a larger

mass that is definitely veined by the clear quartz and

accompanying barite.

Although in general the barite is euhedral against

the clear quartz accompanying it, there are places

where it is corroded by the quartz which is euhedral

against the barite, all within the same veinlet through

the jasperoid aggregate. No difference in age is discernible between the two minerals. Some of the quartz

of this second generation shows remarkable strain

twinning strongly resembling the twinning of microcline. (See pI. 19,A.) This twinning is found only in

a few grains lining open spaces in the breccia, and their

peculiarities are difficult to interpret. They seem to

be governed by slight shearing along prism faces and

the basal plane. They resemble some of the deformed

quartz illustrated by Holmquist,BOthough not identical

with any he describes. The explanation of their origin

preferred by the writer is that they resulted from the

crystallization of chalcedony which had been defoil'Illed

and whose fibers had been deoriented.

There is some doubt as to the age of the stibnite and

chalcopyrite aggregates relative to the several generations of silica, but it seems probable that they accompany the second generation of silica and the first oLf

barite. The calcite present in megascopically visible

amounts is later than the second generation of silica

and fills vugs co~ted by it. The calcite is in turn, however, penetrated and replaced by veinlets of quartz and

fine euhedral plates of barite. (See pI. 19, E.) The

second generation of quartz offers almost no evidence

within itself otfcolloidal origin, but in one place colloform banding was observed. Elsewhere the quartz is

clear and carries no tourmaline, sericite, apatite, or

zircon. Barite and a little calcite with probably the

stibnite and accompanying pyrite are the only impurities it contains.

However, after the cementation of the brecciated

quartz of the first generation by the clear quartz and

barite of the second generation, further brecciation

ensued, and a third generation of quartz, accompanied

by barite, tourmaline, sericite, apatite, and zircon,

penetrated all the older rock and replaced the mass

with blending contacts. This generation of material

exhibits the colloform banding so clearly that there

can be little doubt of its colloidal origin.

The following epitome of the origin of the jasperoid is suggested:

1. Replacement of the limestone along fissures and

bedding surfaces by colloidal silica, accompanied by

tourmaline, apatite, zircon, and calcite.

2. Partial crystallization of the colloidal mass leading to the formation of openings by shrinkage and to

brecciation.

3. Filling of these openings by a mass of perhaps

colloidal silica, barite, and stibnite. Partial replacement of this quartz and the gel of stage 1 by barite.

4. Continuing crystallization of the colloidal mass

of stages 1 and 3, inducing further fracturing of the

barite and the quartz of stage 3.

5. Introduction of calcite, filling vugs, and veining

of calcite by quartz.

6. Introduction of colloform silica accompanied by

tourmaline, apatite, sericite, zircon, and calcite.

7. Introduction of small amounts of muscovite and

considerable epidote, chiefly along fissures in the rock.

It is possible that the stage numbered 7 took place

earlier than indicated, and it is also possible that there

was a still later deposit of calcite lining the vugs and

soHolmquist, P. J., Zur Morphologie der Gesteinsquarz-II: Geol.

Fllren. FOrh., Band 48, Heft 3, pp. 410-428, 1926.
cavities of the jasperoid, but tliese questions have not

been decided. Also there is no information as to the

stage at which the carbon, which is so widespread in

these jasperoids, was introduced.

The suggestion advanced above of colloidal origin

of the silica deposit is similar to that offered by Lindgren 31 for the jasperoids of Tintic. However, the

evidence at Mercur and Lion Hill is not nearly so

clear as that at Tintic, as no large colloform masses of

silica are now observable. It is only in the residual

spherules of chalcedony and the faint banding of colloform shapes through the rock that evidence of the

postulated colloidal stage is discerned.

It might be considered very questionable whether

colloidal silica could be deposited at temperatures high

enough to permit the deposition of tourmaline.

Nevertheless, tourmaline occurs in close proximity to

apparently primary spherules of chalcedony in several slides. With caution urged by the undoubted

evidence. of recrystallization in the rock it can not

safely be stated that the tourmaline is contemporaneous with the chalcedony, but if it is later the recrystallization of the chalcedony during the tourmaline stage

has been incomplete, and the possibility that it is

older than the chalcedony is negatived by the widespread distribution of both minerals through a common matrix of quartz. Furthermore, the barite of

the second stage is locally invaded by tourmaline-bearing quartz which carries colloform evidences. This

throws some doubt on Lindgren's statement 32 that the

absence of chalcedony and other evidences of a metacolloidal origin of the jasperoid in the southern part

of the Tintic district is due to the high temperature

prevailing there at the time of ore deposition, for he

records no tourmaline or other high-temperature minerals from this portion of the jasperoid. It seems

probable that other factors than temperature are involved in determining the boundary between colloidal

and crystalline precipitation of silica.

Although the stages listed above have been traced

with a fair degree of confidence in the specimens

studied, it is highly improbable that they were synchronous throughout the deposits, or even that every

portion of the jasperoid underwent this history. On

the contrary, it is very likely that the crystallization

and brecciation of the early deposited gel was accompanied by constant renewal of the supplies of silica.

A closely connected or even continuous series of contributions of silica may appear as apparently distinct

contributions merely because of local changes in the

supply of material, probably influenced to a large degree by the brecciation due to' crystallization and

shrinkage of the gel. The only conclusionsas to varia81 Lindgren, Waldemar, Geology and ore deposits of the Tintic mining

district, Utah: U. S. Geol. Survey Prof. Paper 107, pp. 154-159, 1919.

•• 14em, p. 1-58.

tions in the supply of material which seem to be established are that barite and stibnite are not found in the

earliest silica except as presumable replacement products and that calcite is abundant only in the late

stages.

Small masses of lime silicates are widespread in the

Stockton and Fairfield quadrangles. They are found

at Mercur,' near Chloride Point, at Ophir, in Dry

Canyon, in Soldier Canyon, near Stockton, in Settlement Canyon, in Middle Canyon, and in Tickville

Gulch. They occur chiefly at the contact of igneous

intrusive rodks and their inclosing limestones but

locally occur isolated from any visible intrusive

masses.

Th!3re are considerable variations in the susceptibility of the different strata to metamorphism of this

type. Although inescapable evidence of the introduction of some extraneous material to the rocks during

the metamorphism has been found, there is no doubt

that the formation of lime silicates is governed chiefly

by the presence of impurities in the limestone. A

similar feature has already been remarked with respect to the metamorphism of the sandstones, quartzites, and shales. (See pp. 94-95.) It is probable that

the rather rigorously selective metamorphism of certain limestones to the neglect of their neighbors is

based chiefly upon such differences in composition.

Thus, large bodies of lime silicate rock have been

d6veloped in the limestone members of the Ophir formation at Ophir, but the olverlying Hartmann lim~-

stone remains essentially unaltered except along very

local fissures. Similarly at Stockton certain limestone

beds in the Oquirrh formation remain completely unaffected by metamorphic processes that have transformed their neighbors to solid lime silicate masses.

Despite this selective action, practically every limestone fOil'mationin the area has at some place been

metamorphosed to lime hornfels in greater or less

degree.

In addition to the stratigraphic control, this variety

of metamorphism is largely confined to fissured portions of the limestones. Thus, in massive limestones

the metamorphism is ordinarily limited to a zone only

a very few feet wide directly at the contact of the intrusive mass, but where the rock has been fissured,

affording paths of easier access for the solutions, the

metamorphism extends much more widely. In general,

the lime silicate masses directly associated with intrusive rocks are much lower in sulphide content than

those which are localized along fissures.

Lime hornfels masses directly along igneous contacts.- The limestones of the Oquirrh formation at the

contact of the hypersthene diorite porphyry mass in

Tickville Gulch have been altered through a zone a
few feet wide into dense green aphanitic porcellaneous

rocks which the microscope shows to consist chiefly o,f

diopside, quartz, and a little pistacite. The contact

zone is narrow.

The quartz diorite stock on the divide between Settlement and Middle Canyons has a similar narrow hornfels bo['der consisting chiefly of the grossularite garnet

(n=1.74) and vesuvianite.

The diorite stock in the east fork of Settlement Canyon has altered the country rock considerably and has

formed in it actinolite, pink orthoclase, quartz, analcite, and garnet (n about 1.85, hence near andradite).

The garnet occurs in veins that are bordered by

actinolite and orthoclase, and the analcite is later than

all these minerals.

The most prominent lime hornfels masses directly

bordering intrusive bodies in the area are those on

the north wall of Soldier Canyon. Inclusions of the

limestone near the border of the largest intrusive

here are considerably altered by reaction with the

magma, and fragments are strewn through the

igneous rock. These consist chiefly of diopside,

slightly altered to uralitic amphibole, pistacite, and

pyrite. The lime hornfels masses surrounding the

stock are about 150 feet in average width but locally

attain 300 feet. Outside the zone where the silicates

have been formed the limestones show some marmarization but to a much smaller distance. The width of

this contact aureole is very striking in view of the

small size of the exposed stock, which is in some

places hardly as wide as the combined contact zones.

It seems highly probable that the relatively great

width of the contact aureole is due to the widening of

the stock downward. Indeed, this is indicated by the

exposed contacts in the ravines. Most of the lime

silicate rocks are dense, porcellaneous, and light gray

with a slight greenish tinge. They are practically

aphanitic in hand specimens and break with hackly

or conchoidal fracture. Under the microscope the

average grain size of these rocks is seen to be about

0.02 millimeter. The dominant mineral is wollastonite, with diopside, orthoclase, quartz, and titanite as

subordinate but abundant constituents. Some pyrite

occurs locally, interstitial to the wollastonite. Where

d~opside is more plentiful the rock is more conspicuously green in color. Locally the hornfels is somewhat coarser grained, "'ith average grain size about

0.1 millimeter, and exceptional sporadic masses of

limestone carry large euhedral green grains of diopside as much as 3 millimeters long. Just at the border

of the igneous mass the hornfels consists largely of

diopside, pistacite, vesuvianite, and andradite. The

garnet and vesuvianite are chiefly localized along fissures and in vugs, a fact which suggests that their

formation was dependent upon the transfer of material to the rock from the intrusive.

The smaller sills near the large stock have similar

though very much smaller contact aureoles. The rocks

are as a rule exceedingly fine grained, and the minerals

are difficult of determination, but diopside, wollastonite, quartz, pyrite, and a little muscovite were

found, with considerable calcite remaining.

The smaller igneous masses south of Soldier Canyon

have very small contact zones in the limestones which

they cut. A little epidote is present along the lamprophyre dike on the Admiral Dewey claims, above Ophir,

and some garnet and diopside occur in the hanging

wall of one of the monzonite sills on the saddle east

of the Chloride Point mine. The Eagle Hill rhyolite

at Mercur has metamorphosed the limestone it intrudes and produced a rock containing garnet, fluorite,

sericite, and quartz for a few inches from the contact.

Some tourmaline has also been developed. The effect

of the Eagle Hill rhyolite has on the whole, however,

been very slight.

Hornfels masses not directly along igneous contacts.-The hornfels masses j~st described are significant scientifically as indicators of the metamorphosing

effect of the several intrusives but are of little or no

economic importance. Similar rocks, not in direct

contact with any igneous masses but localized along

faults and fissures, are, on the contrary, of great commercial importance, because of the very common association of deposits of lead, zinc, and other metals with

them. There are three principal areas within the

Stockton and Fairfield quadrangles where such lime

hornfels masses deposited along fissures are found.

These are the Stockton mining district, Dry Canyon,

and Ophir.

In the mining area near Stockton there are considerable bodies of lime silicate rocks, localized chiefly

along fissures but to a smaller extent along the larger

monzonite intrusives, such as the "Raddatz" porphyry in the Honerine mine. In the sections exhibited

by the crosscuts in the Honerine mine a very large

proportion of the limestones intersected have been

altered to silicate minerals.

Along the drain-tunnel level of the Honerine mine,

near the "Raddatz" porphyry, lime silicate rocks

occur. Typical specimens vary from chalky white to

greenish dense aphanitic rocks, veined with pyrite

and, less commonly, galena and sphalerite. Under the

microscope the rocks are seen to consist chiefly of

wollastonite, actinolite, diopside, quartz, calcite, and

garnet, "with apophyllite, orthoclase, apatite, zircon,

titanite, and muscovite as "less prominent components.

The garnet (n slightly higher than 1.90, probably indicating a titanium-bearing andradite) occurs chiefly

as veins through the wollastonite 'rock. Calcite occurs

both as a residual mineral poikilitically inclosing the

other minerals and in veins through them. Some veins

of antigorite and small veinlets of quartz penetrate
the rocks. Sulphides, where present, appear to be

definitely associated with fissures, commonly the same

ones as are followed by the garnet. Some few specimens carry a little plagioclase near the composition

Ab7oAnao• At the mouth of the St. Patrick crosscut

metacrysts of wollastonite fully 1 centimeter across

are common in this variety of hornfels.

Very similar rocks occur in the copper drift and the

Bullion crosscut of the Honerine mine. In the Bullion crosscut orthoclase-rich hornfels also was found,

and both epidote and fluorite occur in it. Sepiolite

and a clay mineral resembling beidellite occur as

alteration products of these rocks.

In the Knickerbocker crosscut of the Honerine mine

the "Honerine" limestone is a dark-gray, coarsely

crystalline, essentially pure carbonate rock, but the

limestone immediately overlying it has been metamorphosed into a diopside-wollastonite-zoisite rock with

some andradite, fluorite, orthoclase, and apatite. Some

quartz occurs in certain beds of the altered rock.

Other localities in the Honerine mine at which lime

silicate rocks were collected include the 1,600-foot level

in the hanging wall of the 1,640stope; the tunnel level

in the" Honerine " limestone east of the vVier crosscut;

the hanging wall of the Palace shoot, just above the

drain-tunnel level; and many places in the crosscut

to the Tip Top mine. As is evident on computation

of the analysis quoted on page 96, the rock from the

hanging wall of the "Honerine" limestone called

"dolomite" by Butler, is actually a silicate rock

similar to those just described. Similar rocks also

occur in the footwall of the" Galena King" limestone

of the Tip Top mine at the 700-foot level and in the

hanging wall at the portal of the Tip Top tunnel, as

well as near the Calumet and Muscatine mines, toward

the south end of the Stockton mining area.

In Dry Canyon lime silicate rocks are less conspicuous than they are near Stockton; nevertheless,

they are found at many places. In the lower tunnel

of the Mono mine, along the Corbon No. 1 fault, the

Deseret limestone has been altered to a rock consisting of coarsely crystalline calcite, actinolite, sericite,

and quartz, veined by seams carrying pyrite, chalcopyrite, sphalerite, and galena. In the fractures

cutting these sulphide veins later quartz and calcite

have been deposited.

Some diopside-wollastonite rock occurs in the Deseret incline, and considerable was found on both the

Dry Canyon and Ophir Canyon sides of the Hidden

Treasure and Cliff mines. Along the Cliff fault in

the lower tunnel of the Cliff mine the Lynch dolomite

has been metamorphosed to a diopside-tremolite rock

that carries a little residual calcite and is veined by

talc, which has been derived by alteration of the diopside and tremolite. Some wollastonite occurs here

also, but it is not prominent. A mineral resembling

marialite but too fine grained for certain determina~

tion is also present. Small veins of pyrite, sphalerite, and a little galena penetrate the rock.

Along the West Side stopes of the Hidden Treasure

mine considerable lime hornfels occurs. The rocks are

dark green, aphanitic, and impregnated by seams of

galena, sphalerite, and pyrite. The minerals composing the rock are diopside, actinolite (formed by alteration of the diopside), orthoclase, apatite, muscovite,

garnet (n about 1.85, near. andradite), chlorite (an

alteration product of diopside, garnet, and actinolite)

and sulphides. The sulphide veinlets also carry much

garnet. Calcite is residual and incloses most of the

other minerals where the silication has not proceeded

to completion.

On the Sovereign tunnel level at the second crosscut east of the Hidden Treasure incline chert nodules

in the limestone have furnished opportunity for metamorphism by reaction. The center of one chert nodule

that was studied is recrystallized into a quartz mosaic,

inclosing rosettes and aggregates of wollastonite and

diopside. This is surrounded by a confused aggregate

of wollastonite, then by radiate wollastonite fibers sev"'

eral millimeters in maximum length. The whole is set

in a coarse calcite matrix, containing little knots of

quartz and wollastonite scattered through it. Orthoclase and a very littlepistacite, together with carbon

\rhich is concentrated in wavy streaks subparallel to

the outline of the chert nodule, also occur. No sulphides are present here.

In a stope above the Sovereign tunnel level, in the

lower part of the Deseret limestone, several silicate

minerals occur. The limestone is rich in phosphates,

chiefly collophane, which has partly recrystallized to

apatite. Diopside (somewhat altered to actinolite),

quartz, orthoclase, epidote, sericite, andradite garnet,

and probably marialite also occur in this rock, which

superficially is apparently unaltered blue limestone

and effervesces freely in cold dilute acid.

The most conspicuous association of lime hornfels

with fissures and with sulphide ores in the Stockton

and Fairfield quadrangles occurs at Ophir, on the

north side of Ophir Canyon, in and around the Ophir

Hill Consolidated mine. The limestone beds in the

upper part of the Ophir formation have been altered

adjacent to the Cliff fault and a group of related

north-south fissures, and the ultimate product of the

metamorphism consists of the ore bodies worked in

the Ophir Hill mine. The surface exposures are not

good, but in conjunction with the east (7lh) drift on

the "Copper bed" at the drain-tunnel level in the

Ophir Hill mine they give a fairly good opportunity

to trace the alterations of the limestone into ore.

The unaltered limestone of the Ophir formation is

impure, discontinuous shaly bands running through

it and giving it a mottled appearance. vVhere fresh
the shaly layers are a darker brown than the purer

limestones, a contrast that is heightened by weathering. The microscope shows that the rock is made up

of calcite layers carrying a few flakes of muscovite,

with chlorite and carbon, together with silty layers

rich in muscovite, apatite, carbon, and a little pyrite.

An analysis of the rock is given in column 1 of the

first table on this page.

Toward the ore bodies the rock becomes more

coarsely crystalline and slightly more quartzose. An

analysis of such a rock is given in column 2 of the

table. At about 250 feet east of the No. 2 stope in

the " Copper vein" limestone the banding is still more

pronounced and the rock is somewhat lighter in color.

It is composed chiefly of calcite, but muscovite, quartz,

orthoclase, and chlorite are prominent constituents,

and epidote, rutile, tourmaline, and pyrrhotite occur.

An analysis of the rock is given in column 3 of the

table. It is evident that the rock shows decreasing

carbonate and calcium content and increasing silica,

alumina, and potassa. This is reflected in the quantitative mineral composition given in the table at the

bottom of this page.

About 25 feet east of No.2 stope on the draintunnel level of the Ophir Hill mine the "Copper

vein" limestone is strongly mottled with white, green,

and gray bands and lenses and is veined with pyrite

and pyrrhotite. Under the microscope the rock is

seen to be strikingly different from those above described. Calcite remains more abundant than any

other mineral but constitutes only about one-third of

the rock. Orthoclase, in very minute grains, averaging perhaps 0.02 millimeter in diameter, forms a

mosaic carrying quartz grains and rosettes of sericite

in considerable quantity. Epidote is an abundant constituent of the rock, being closely associated with the

calcite. Its crystals, many of them beautifully euhedral, reach 0.2 millimeter in length. Chlorite mats

are associated with them. Rutile, apatite, and pyrite

are subsidiary constituents. A hand specimen of this

variety of rock is illustrated in Plate 20,A. Its analysis is given in column 4 of the table.

Still closer to the fissure along which the stope is

localized the rock is altered to sulphide ore. Under

the microscope its nonsulphide constituents are seen

to be orthoclase in rhombic crystals (adularia), quartz

exhibiting a strong tendency to form euhedral crystals as much as 1 millimeter long, sericite, chlorite,

calcite, fluorite, zircon, rutile, and apatite in short

prismatic grains. The sulphides show a tendency to

be molded on the euhedral quartz crystals (see pI.

20, B) and to replace quartz and all the other minerals. The analysis of this ore is given in column 5

of the table.

The mineral composition of the rocks of .the series

just described, deduced from microscopic study in conjunction with the chemical analyses, is given in the

second table below. This table shows the increase in

silicates and sulphides and the decrease in carbonates

during the metamorphism.

Chemical analyses showing metamorphism of "Copper vein"

limestone of the Ophir formation, in the Ophir Hill Consolidated

mine .

[J. G. Fairchild, analyst)

1 2 3 4

1__

5

Specific gravity:

Particles _______ 2.760 2. 782 2. 762 2.724 3.841 Lump __________ 2. 760 2. 758 2. 758 2. 716 3.591

Porosity (calculated)_ 0:00 1. 00 O. 10 O. 20 6. 50

Si0

2

_______________ 1. 05 22. 67 32.73 37.08 19. 22

A1203_-- ________--- 1. 20 4. 96 11. 65 11. 14 7. 60

Fe203_____---- __--- .38 .97 1. 19 1. 35 .96 FeO _______________ 1. 96 2. 73 2. 73 1. 42 1. 80

MgO ______________ 4.31 2.17 4.16 1. 92 2. 26 CaO _______________ 48. 18 35.55 24. 57 21. 80 2.47

Na20_ -- ______-- _-- Trace. Trace. Trace. .15 .59 K2

0 _______________ .12 1. 59 3.92 7.00 3. 68

H20 - - - - - - - - - - - - - - .05 .00 .14 .06 .00

H20+ ------------- .05 1. 42 .70 .80 1. 62 Ti0

2

_______________ .00 .25 .50 .50 .20 CO2

_____________ -- 41. 66 27.30 17.12 14.75 1. 99

P2O.------ _________ .03 .26 .12 .25 .35 CI_. _______________ .03 .02 .11 . 03 Trace . F _________________ (a) (a) (a) (a) .25 S__________________ .05 .56 .33 .17 .80 MnO ______________ .25 .10 .10 .20 .35 FeS2_______________ .37 Trace? (a) 1. 50 26. 39 PbS _______________ (a) (a) (a) (a) 14.37 ZnS _______________ (a) (a) (a) (a) 15. 07 Cu ________________ (a) (a) (a) (a) .40 Ag________________ (a) (a) (a) (a) Trace?

99. 69 100.55 100. 07 100. 121100. 37

Less O=S or F _____ -------

.28 .17 .08 .51

99. 69 100. 27 99.90 100.041 99. 86

I

-Not found.

1. Practically unaltered limestone, about 400 feet ea:;t of

No.2 stope, 7% east drift.

2. Slightly altered limestone, about 300 feet east of No. 2

stope, 7% east drift.

3.Banded, more altered limestone, 250 feet east of No.2

stope.

4. Mottled green, white, and gray hornfels, 25 feet east of

fissure in No. 2 stope.

5. Ore in hornfels, 10 feet east of fissure, No.2 stope.

Mineral composition (percentage by weight) deduced from microscopic studies and chemical composition of the analyzed

rocks listed in preceding table

1

I

2 3 4 5 58

-- -- -- -- --- --

Calcite ___________ 74. 8 62. 5 38. 9 33. 5 ______

------ Dolomite _________ 20. 2 ______

------ ------ 4. 3 10.5

Muscovite ________ 8 13. 5 18. 3 6. 1 9. 6 23.6

Quartz ___________

------ 13.9 12. 0 9. 5 ______

------ Orthoclase ________

------ ------ 10. 0 26. 7 20. 2 49. 4

Epidote ___________ 2. 9 15. 1 2. 1 5. 1

Chlorite __________ 2.II 6. 7 17. 0 5. 4 3.0 7.3

Apatite ___________ 7 3 31. 0 2. 4

Rutile ____________ ------1 3 5 5 .2 .5

Pyrrhotite ________ .2, 1. 6 8 4 ______

------ Magnetite ________ 71 1. 4 ______

------ ------ Pyrite ____________ 41______

------

1. 5 25. 7 ______

Galena ___________

------ ------ ------ ------ 14.4 ------

~halerite:--- _____ ------ ------ ------ ------ 17. 3 ______

halcopynte ______ ------ ~----- ------ ------

1. 1 ------ Fluorite __________

------ ------ ------ ------ 6 1.4

-- -- ---

100. 1 100.6 100. 7 99. 0 99. 5 100. 2

-----._----------~._------
The computed mineral composition of the first four

of the rocks above represented agrees well with the

composition as estimated from study of thin sections.

No.5, however, appears from microscopic study to

carry considerably more free quartz than is permitted

by any possible combination of the chemical components of the rock found in the analysis. It also

carries more epidote than chlorite, which, if computed

from the chemical analysis, would cause a decided

deficiency in silica. Both of these discrepancies are

believed to be due primarily to the impossibility of

obtaining a representative sample of sulphide-silicate

rock and secondarily to difficulty in duplicating

samples of powder with such large differences in density as well as to inevitable errors in so complex an

analysis. Undoubtedly there is considerable quartz

in the rock, perhaps as much as 6 or 8 per cent. Chlorite is somewhat lower than the above computation

shows, and epidote somewhat higher. However, the

analysis undoubtedly reveals a continuation of the

.chemical transfers indicated in the earlier part of

the series, as is clearly seen in column 5a, which represents the composition of the nonsulphide portion of

No. 5 on the approximate assumptions of the mineral

composition shown in column 5.

Although the series of changes just described as

shown by the " Copper vein" limestone of the Ophir

Hill mine is believed to be representative of the rest

of the mine, it does not embrace all the rock 'varieties

found. Locally, the metamorphism leads to replacement of the original limestone by quartz, with orthoclase and sericite as practically the only silicate minerals. A trifling amount of tourmaline was found in

such a specimen.

At some places a banded and mottled hornfels oceurs which carries essentially pure andradite (refractive index 1.89± 0.01) in beautifully euhedral crystals

with orthoclase and epidote. Calcite is residual and

also occurs as veins cutting all the silicates. Pyrrhotite, pyrite, galena, and sphalerite occur interstitial

to the garnet and epidote and locally replace them.

(See pI. 23, B.) The sulphides have a decided tendency to favor certain layers, producing a lenticular

stratiform arrangement.

Diopside occurs in some of these garnet-bearing

rocks. It is everywhere euhedral against the calcite

in which it is embedded.

In some places near fissures tong'_lesof epidote and

white calcite rock, roughly parallel to the bedding,

penetrate apparently unaltered limestone. Such

tonguelike masses are usually accompanied by pyrite,

which is rather rigorously limited to them, being practically absent from the gray limestone. A little

.(}Ullrtz,in small part euhedral, is commonly associated

with such pyrite. In some specimens such tongues of

replacement minerals appear to have been guided by

carbonaceous layers in the limestone, for carbonaceous

seams occur in the middle of them. It is probable that

such seams afforded zones of greater permeability for

solutions penetrating the rock, though it is possible

that they furnished a chemical cause of localization.

All the varieties of hornfels described above are

conspicuous and common in the Ophir Hill mine, but

the dominant variety is a conspicuously banded, very

strikingly mottled rock. The rock is green, white,

and brownish gray, with very systematic arrangement

of the bands. (See pI. 21, A.) The brownish-gray

layers are traceable directly into the mottled layers

of less altered shaly limestone, and it is clear that

the green bands similarly represent the alteration of

the limestone.

Under the microscope the brownish-gray layers are

seen to be composed almost wholly of minute muscovite plates, oriented for the most part parallel to tb,e

bedding of the rock, though some of them are arranged

in rosettes or transverse to the bedding. Few of these

mica plates reach a length of 0.03 millimeters. A

little orthoclase and epidote occur in these altered

shale layers, and a trifling amount of pyrite, which

may be of sedimentary origin, is also found. The

layers probably owe their brownish-gray color to the'

presence of minute carbonaceous flakes.

The clear-white layers that everywhere border these

shale layers are shown by the microscope to consist

almost wholly of minute grains of orthoclase, which

rarely attain 0.1 millimeter and average perhaps 0.01

millimeter in diameter. Muscovite, epidote, and some

carbonaceous material occur in the orthoclase layers

but in quantities so small that they can not be seen to

affect the white color of the layers. A little plagioclase, probably oligoclase, was seen in three or four

slides. The boundaries between the white orthoclase

layers and the brownish-gray muscovite layers are, in

general, parallel to the bedding, but closer study shows

that this is only an approximate parallelism-the contact is serrate in detail.

The green layers, which represent the alteration of

the purer limestone parts of the. rock, consist chiefly

of epidote, in crystals reaching 0.6 millimeter in length

but averaging perhaps 0.1 millimeter. Locally these

crystals constitute the entire layer but generally they

are set in a coarsely crystalline calcite matrix. A little

orthoclase and muscovite occur in these layers. Considerable quartz and chlorite also occur here and

there, but these are believed to be chiefly due to a still

later phase of metamorphism. Such quartz masses

commonly inclose euhedral crystals of epidote and

adularia. (See fig. 13.)

The' hornfelses described above have furnished the

country rock for ore of three different varieties-fissure fillings, impregnations, and massive sulphides,
There are two chief varieties of fissures along which

the sulphides occur. Those of one variety are clean

cut, are nearly vertical, and form the central fissures

of the ore shoots that have been mined. Several of

these fissure veins cut cleanly the massive replacement

ore that makes up the chief ore of the mine, but their

central positions in the stope are nevertheless convincing evidence of their genetic relations to the replacement ore. A hand specimen illustrating the clean

cutting of replacement ore by such a vein is illustrated

in Plate 21, B.

These central veins rarely exceed 2 inches in width

and for long distances may be individually less than

a quarter of an inch, though where they are so narrow

FIGURE 13.-Traeing of photomicrograph, showing euhedral orthoclase (adularia) crystals inclosed in quartz groundmass. Enlarged

260 diameters

there are usually several veins. They consist chiefly of

pyrite in a carbonate matrix, the whole veined with

galena, sphalerite, chalcopyrite, .and considerable tennantite. The paragenesis appears to be manganiferous

dolomite, pyrite, tennantite, pyrrhotite, galena and

sphalerite, chalcopyrite, sericite, with locally a late

generation of tBnnantite and, finally, a late generation

of slightly manganiferous dolomite. Exceptionally

the veins carry a little quartz and orthoclase as very

early minerals. The early dolomite has commonly

been almost completely replaced by sulphides. The

manganese content of the early dolomite, as indicated

by refractive indexes and by bead tests, amounts to

only a few per cent. A little manganiferous calcite

also occurs, but its relation to the other minerals is

uncertain.

In addition to these generally clean-cut major fissures there· are many small, anastomosing irregular

veinlets penetrating the hornfels in innumerable directions. At places where the alteration to hornfels

has been incomplete epidote is concentrated along

such veins, both as a veneer of the fracture surface and

replacing the country rock. Pyrite almost invariably

accompanies the epidote. Where the alteration to

hornfels has led to complete silication of the rock,

these veinlets are filled with pyrite, dolomite, chalcopyrite, a little pyrrhotite, galena, sphalerite, quartz,

and, less commonly, fluorite. In these stringers, as

well as in the larger fissures, the manganiferous

dolomite is commonly early and replaced by pyrite.

Galena, sphalerite, and chalcopyrite replace the pyrite, and fluorite, where present, replaces these sulphides. Locally there is a second generation of dolomite. Sericite is commonly a very late mineral. It

is interesting to note that pyrite commonly replaces

the rock along such fissures, and although the later

sulphides do so locally, they are much more closely

limited to the fissures themselves.

Close to these fissures the hornfels has been in

places decidedly sericitized. The residual calcite, epidote, orthoclase, and muscovite have been attacked

and replaced by fine mats of radiating sericite. The

sericite is commonly accompanied by pyrite and

quartz, but it has also attacked and embayed older

quartz and pyrite. In general, it may be said that the

sericitization was later than the epidote-orthoclase

formation and later than at least a part of the sulphide deposition. This is evident from the manner in

which the sericite rosettes are embaying and replacing

the pyrite-galena mass shown in Plate 22, A.

The sulphides, in addition to cutting through the

hornfels as veinlets, occur as impregnations through

it. Of these impregnating sulphides, pyrite is decidedly the most widespread. Pyrrhotite is common, together with sphalerite, galena, and chalcopyrite. The

galena contains sparse microscopic blebs of argentite.

All the sulphides show a marked preference for the

epidote rock as host, and it is rare, indeed, to find

galena or sphalerite in the muscovite or orthoclase

varieties, but pyrite and to a less extent pyrrhotite

and chalcopyrite are less rigorously confined to the

epidote layers. Fluorite and dolomite are occasionally found with the impregnating sulphides. The

impregnating pyrite is commonly euhedral and in individual crystals, but the other sulphides usually occur as rounded or lenticular aggregates. Locally this

lenticular habit of the sulphides leads to a decided

banding of the rock. (See pI. 22, B.) In places,

though by no means everywhere, this lenticular habit

can be referred to the replacement of carbonate lenses

in the hornfels. The carbonate itself is probably usually a replacement mineral, occurring chiefly in the

middle of the epidote layers but in places at the borders. Such a specimen showed, under the microscope,

replacement of the carbonate by euhedral quartz

prisms, with sulphides molded on the quartz and to

some extent replacing it as well as carbonate. Seri-
A, B. "TYPICAL JASPEROID" TEXTURED VARIETY OF JASPEHOlD

The illtcn~ticc8hctwccll:quurLz; erY8Lalsin this specimen, though not in nlOsL, are filled with carbon. At Crossed nicols; B, plain light. Elllargcd 36 diameters.

C D

C, D. ANHEDRAL VARIETY OF JASPEROID, VEINED WITH BARITE THAT CONTAINS EUHEDRAL QUARTZ CRYSTALS

C, Crossed nicoIs; D, plain light. q, Quartz; b, barite. Enlarged.Sl diameters.
cite is the latest mineral, replacing all the earlIer ones.

The paragenesis is carbonate, quartz, pyrite, galena

and sphalerite, sericite.

The replacement of the epidote bands by sulphides

was not confined to the calcite masses, however, but

proceeded throughout the layers. In· the ore bodies

themselves the sulphides have replaced the entire epidote layer, resulting in an ore consisting of sulphides

with remaining bands of muscovite and orthoclase running through it. (See pI. 23, A.)

Such ore is crudely banded parallel to the bedding,

as a result of variations in the amounts of the different sulphides. The sulphides ,vere nearly always accompanied or preceded by a small amount of carbonate. Pyrite is the earliest sulphide, being! veined

and replaced by galena, sphalerite, and chalcopyrite.

The pyrite has a strong tendency toward euhedral

form, but the other sulphides show very slight tendencies of this kind. Locally pyrrhotite, accompanied by

chalcopyrite, is the dominant sulphide replacing pyrite and is itself replaced by galena and sphalerite.

The sphalerite invariably contains minute blebs of

chalcopyrite. These are shown by reflected polarized

light to be composite, each bleb made up of several

diversely oriented grains. The blebs are arranged

along cleavage directions in the sphalerite and along

grain borders. Whether they are due to replacement

or to unmixing of solid solution of chalcopyrite and

sphalerite is unknown, though the constancy of the relationship seems to favor the latter hypothesis.

In some of these ore-bearing banded hornfels masses

the orthoclase bands show later replacement by calcite

,in plates developed parallel to the base. This crystal

form is very probably the form of calcite stable at

high temperatures. Its common association with

rhombic orthoclase has been pointed out by Kalb.33

In a few places the metamorphism of the limestones

in the Ophir Hill Consolidated mine has resulted i.n

the production of small vugs in which many beautifully euhedral crystals of various minerals were developed. Among the most remarkable of these vugs

are some in the wall of the 'Wild Delirium stope in

the "Copper vein" limestone. Euhedral pyrite furnishes support for some remarkable tetrahedrons of

tennantite fully 2 centimeters on an edge. Beautifully formed galena crystals, developed along the

octahedron, form blades 1 centimeter across and are

in part covered by clean-cut, brilliant twinned chalcopyrite crystals. Dolomite, in flat rhombohedrons and

rosettes, prismatic quartz, and very unusual acutely

scalenohedral calcite, as well as the common flat rhombohedral calcite, were found in such vugs. In one

••Kalb, Georg, Die Kristalltracbt des Kalkspates in minerogenetiscber

Betrachtung: Centralbl. Mineralogie, 1928, Abt. A, No. 10, pp. 337-

339,

specimen examined euhedral wurtzite coats tennantite,

along with dolomite and calcite. Large rhombs, 1

centimeter on an edge, are pseudomorphed by minute

rhombs of siderite which form a very porous mass.

Whether the original large rhombs were solid siderite

or some other carbonate is unknown.

ParraJgenesis durring hornfels metamorphism.-The

paragenetic relations of the minerals of the lime silicate rocks are not clear in detail. Recrystallization

has proceeded to such an extent close to the ore bodies

that it is not possible to determine whether the rock

has passed through the successive stages of mineralogic

change that are now indicated in proceeding from unaltered limestone to ore or whether the present relations are due to the temperature gradient away from

the central fissures. Thus the exterior zones of altered

rock are rich in muscovite and chlorite, while the interior zones are in general rich in orthoclase and epidote, but it is impossible to prove whether or not a

rock that is now composed of epidote, orthoclase,

quartz, and muscovite ever passed through a phase of

development during which it contained chlorite and

muscovite as its sole noncarbonate constituents. Thus

it can not be asserted that epidote was developed later

than chlorite but merely that it was more stable at

the higher temperatures prevailing during metamorphism. Epidote represents a higher ratio of ferric

to ferrous iron than chlorite.

On this basis, then, garnet, epidote, diopside, orthoclase, and quartz belong to an inner zone of higher

temperature. and greater material transfer, whereas

chlorite and muscovite, although found in the inner

zones, are characteristic of the border of alteration,

where less metamorphism has occurred and presumably lower temperatures prevailed. Some sericite is

definitely later than all other silicate minerals and

definitely replaces them as well as the sulphides in a

few localities close to the fissures. Probably this replacement occurred during a fall in temperature in a

late stage of the mineralization. Quartz is also a

late mineral in places.

'Whatever may be the age relations among the silicates, it is quite certain that in general the sulphides

and carbonates were deposited later than the silicates,

for they vein the garnet-epidote-orthoclase rocks in

every specimen examined and inclose and embay the

individual silicates in a way that is convincing of their

later formation. Among the sulphides, pyrite appears to be the earliest as well as to have traveled most

widely; pyrrhotite, galena, sphalerite, and chalcopyrite are later. The mutual relations of the three lastnamed minerals are not such as to prove any age

difference between them, except that locally the chalcopyrite veins galena and is thus later. There is also

a suggestion that sphalerite began to be deposited
are coated by greater or less quantities of pyrite and

galena, although some are barren. Where these fissures penetrate limestone beds of the Oquirrh formation they commonly are bordered by sulphide masses

in the limestone. Sulphide masses also occur along

stringers making out from these fissures into hornfels,

quartzite, porphyry, or unaltered limestone. There

has been little mineralization in the area that can not

be directly referred to visible fissures, and the probabilities appear overwhelming that if exposures were

sufficient all the sulphide bodies would be found to be

related to fissures or other especially permeable passageways.

Where the east-west limestones are cut by strike

faults and fissures, as they are in the Hampden stope

in the" St. Patrick" limestone and the PalHigher temperaturesCearly) -lower temperaturesClateJ

Garnet ace shoot above the 1,200-foot level in the

Epidote ------ " Honerine" limestone in the Honerine mine

Diopside and in the "Galena King" limestone in the

Orthoclase ----

Quartz Galena King and Tiptop mines, the stopes are

Chlorite especially large. However, no considerable

MuscoviteCsericiteJ ------------- ore body that is not related to the north-south

Pyrite --------- fissures has been found in this area, so that

Pyrrhotite ---- ? f . .. f

Galena ? strike aultmg m ltsel can hardly have sufficed

Argentite ---- for the localization of the ore bodies. PresumSphalerite ----- ably this is due to lack of persistence of the

Chalcopyrite ------- strike faults, which probably originated by

Tennalitite - ? -?

Calcite ? shearing during folding. The north-south

Dolomite ------------- ? fissures, standing essentially parallel to the

FIGURE 14.-Paragenetlc relations of minerals In hornfels ore at Ophir compressive forces, gaped open and furnished

However, although hornfelses and accompanying sul- continuous channels for the metamorphosing solutions.

phi des are widespread in the Stockton and Fairfield The fissure control in the localization of sulphide

quadrangles, the only mineral deposit of impOJ'tance bodies is not quite so conspicuous in the mines of Dry.

that is characterized by the dominance of lime silicate Canyon, doubtless in part because of greater oxidation

gangue is that of the Ophir Hill Consolidated mine, at and consequent obscuring of relations in the accessible

Ophir. The ore deposits of commercial value, with portions of the deposits. Even here, however, the

the exception of the jasperoid ores such as those of linear disposition of the ore bodies strongly suggests

Mercur, Sunshine, and Lion Hill and the lime silicate fissure control during ore deposition. Similar eviOJ'esof the Ophir Hill Consolidated mine, are charac- dence is found in the Hidden Treasure and Cliff mines

terized by the comparatively narrow zones of alteration :md in the Buffalo tunnel, on Lion Hill.

of their wall rocks. In addition to the fissure control of sulphide replaceThe principal localities where the metamorphism of ment there has been an apparent stratigraphic control.

limestone to sulphides has occurred are in the mining It is only exceptionally that the sandstone, quartzite,

area near Stockton, in Dry Canyon, and Ophir Can- and shale in the area are replaced by sulphide ores,

yon, and on Lion Hill. The local features that appear although this has occurred in the Kearsarge mine, in

to have exercised control in bringing about this meta- Dry Canyon, and in the Salvation-Hercules mine, in

morphism are fissuring of the rock and the presence Ben Harrison Gulch. Even among the limestone beds

of a susceptible limestone bed. there is great variability. Certain beds are very susThe remarkable localizing control exercised by the ceptible to replacement and others are not, although

fissures is very strikingly seen in the mining area near no chemical or physical differences between them are

Stockton. Here the country rock is sliced by a multi- readily discernible. Probably there are intrinsic diftude of essentially north-south fissures, most of which ferences in susceptibility between the different limedip steeply west. Many of these fissures are faults, stones, but the irregularity in the replacement seems

but others show no measurable displacement. Many more commonly to depend upon physical factors than

slightly earlier than galena. The minute argentite

blebs are apparently limited to the galena and are

probably contemporaneous with it. Tennantite is

present in very small quantities, some earlier than

galena and some apparently later. Carbonates preceded, accompanied, and followed the sulphides.

These paragenetic relations are summarized in Figure

14.

Replacement ol'e.-.A.s appears inevitable in the

classification of natural phenomena, there is no sharp

division between the alteration of limestone to hornfels and accompanying ore minerals and the alteration

of limestone to sulphides with few or no lime silicates.
upon chemical factors. The conspicuous shearing

along bedding planes in several of the larger ore

bodies gives rise to the suspicion that the varying susceptibility to replacement of the different limestone

beds may be due chiefly to variations in fracturing of

the beds. This can not be proved, howevor, and until

that is done it seems permissible in the discussion of

ore localization to distinguish between evident fissures

and differences in susceptibility of the limestone beds.

The "Honerine," "St. Patrick," "Galena King,"

"Ben Harrison," and "Black Bear" limestone beds

of the Oquirrh formation are conspicuously more susceptible to metamorphism than the other limestones in

this part of the stratigraphic section. In the Dry

·Canyon area the beds at the top of the Deseret limestone contain the ores of the Deseret and Queen of the

Hills mines, and the beds just below the Long Trail

shale member of the "Great Blue" limestone have

been the sites of sulphide replacement in the Mono

and Brooklyn mines, in Dry Canyon, and in the Buffalo tunnel, in Long Trail Gulch. Similarly the

beds at the top of the Madison limestone contain most

of the ore in the Jim Fisk mine, in Ophir Canyon, and

the Hidden Treasure mine, in Dry Canyon. The Cliff

mine, however, is developed in beds low in the Madison

limestone, and the Chicago ore shoot is very irregular

and is not limited to any particular limestone bed.

These ore-bearing limestones do not differ conspicuously from their neighbors, yet the markedly selective

replacement they have undergone certainly indicates

some distinctive feature about them, of fundamental

·economicimportance.

The replacement of these limestone beds by sulphide

,ores is localized along fissures and for the most part

within certain beds. The sulphide replacement bodies

are only rarely, however, of the full thickness of the

limestone host, but occur as podlike masses, usually

.exhibiting their maximum thickness along the fissures

and narrowing away from them. Commonly the termination of the replacement body is of smoothly

rounded outline, but veinlets of sulphides are occasionally seen which extend in stringers along the limestone beds away from the more massive bodies. Where

the replacement has been essentially complete to the

full extent away from the fissure, the stopes have been

-extended to its limits, but where the sulphide bodies

.terminate in replacement veinlets and stringers the

-economiclimitations on mining have resulted in leaving the small stringers in the stope walls. Commonly

the alteration of the wall rocks along these sulphide

bodies has been very slight, resulting merely in a

small amount of sericitization and silicification. Adjacent strata are locally altered to lime silicate hornfels (see p. 105), but only rarely does the bed that has

undergone sulphide replacement show also the horn-

:fels variety of metamorphism.

The size of these replacement masses is variable, although the variations within anyone mass .are not,

as a rule, vllry irregular. Some of the replacement

bodies exceed 100 feet in strike length, although this

length is exceptional and rarely maintained for any

great distance along the pitch of the body. The pitch

length of the replacement bodies is also variable, but

the Palace shoots in both the " Honerine" and " St.

Patrick" limestones have bllen followed to depths of

1,600feet, corresponding to pitch lengths of over 1,800

feet, and the pitch length of the Hidden Treasure

stope is over 1,600 feet. All gradations in size occur

down to and below the minable limit. It is noteworthy, however, that variations in cross section along

the pitch within any single body are generally

gradual.

The sulphide replacement bodies are commonly

massive and are composed chiefly of pyrite, galena,

and sphalerite, with subordinate amounts of chalcopyrite. The galena contains a very few microscopic

blebs of argentite. The sulphides rarely show banded

structure except where the replacement has terminated in stringers that are roughly parallel to the

bedding. Where replacement has been complete banding is generally inconspicuous. In some places there

is a crude tendency for the pyrite to form a shell

about a central core of galena. This arrangement is

visible in the Palace shoot in the "Honerine" limestone just above the drain tunnel of the Honerine

mine but is not a constant feature. The most striking feature of the sulphide replacement masses is

probably their variability in mineralogy, a single

shoot changing capriciously along its length from a

galena-rich to a sphalerite-ricb mass. There is, however, considerably more zinc than lead in the Dry

Canyon area and considerably less in the Stockton

area.

The mineralogy of the sulphide replacement is very

simple. Quartz, sericite, calcite, and locally a little

epidote are the only gangue minerals of consequence

in most of the deposits, and they are probably much

subordinate quantitatively to the sulphides. Fluorite

is a prominent constituent of the ore from the Buffalo

tunnel and the Queen of the Hills mine. Pyrite is

probably the most plentiful sulphide, because of its

widespread impregnation of the limestones in small

bunches, but in the more massive replacement bodies

galena and sphalerite predominate. Chalcopyrite is

locally plentiful but is absent from many shoots.

Arsenopyrite occurs in small quantities but is reported

to be locally plentiful. Tetrahedrite is reported by

Butler 34 as a minor constituent of the ore at Stockton

but was not found in the specimens studied by the

writer. It must be very subordinate.

••Butler, B. S., The ore deposits of Utah: U. S. GeoL Surve:y Prof.

Paper 111, p. 372, 1920
The paragenesis of the minerals in these sulphide

bodies is as follows: Quartz began to be deposited

earlier than the other minerals, followed by sericite.

Pyrite is in general the oldest sulphide but locally

replaces the others, proving its long-continued deposition. Chalcopyrite is ordinarily slightly later than

the first pyrite and commonly is associated in intimate

intergrowth with sphalerite but in some specimens

clearly cuts galena and sphalerite. Galena and

sphalerite are of essentially the same age, but in places

there is a suggestion that the galena is a little later

than the sphalerite. Elsewhere the sphalerite replaces

the galena. In the fluorite-bearing replacement bodies

fluorite is later than galena. Calcite is both earlier

and later than the sulphides, being, like quartz and

Quartz

Sericite

Epidote

Pyrite

Chalcopyrite

Sphalerite

Galena

Argentite

Fluorite

Calcite

Tetrahedrite ?

Arsenopyrite ?

FIGURE15.-Paragenesis of limestone replacement ore minerals

The fissure ores undoubtedly carry more gold than the

replacement ores, assays as high as $19 a ton having

been reported on ore from the Wier fissure, in the

Honerine mine. In the Salvation-Hercules and Kearsarge fissures even higher assays have been reported.

Locally this fissure ore is of sufficient value to be

mined, as in the Salvation-Hercules, Kearsarge, and

Jim Fisk mines, but practically all the economically

important deposits are of replacement origin.

In addition to the principal varieties of metamorphism of the limestones which have been described

above, a small amount of dolomitization has also been

effected by igneous emanations and is appropriately

considered here. The extensive dolomite

Later beds of the area, as stated on page 16, are attributed to alteration during or shortly after

deposition and not to igneous metamorphism.

Most of the small amount of dolomitization

considered below is confined to the Ophir Hill

Consolidated mine. At several places in this

mine, instead of the usual hornfels and sulphide products, the metamorphism has

altered the limestones of the Ophir formation

to dolomite. An effort was made to ascertain whether or not a zonal distribution of the

dolomite was discernible with reference to the sulphides and silicates associated with the fissures of the

mine, but its distribution appears to be sporadic.

Small lenses of brecciated, veined, and vuggy dolomite

occur along the borders of the stopes, but more commonly the stope walls are formed of lime silicate rocks.

The small masses of dolomite are mottled gray, buff,

and white. Close inspection shows that the gray

masses are residuals of the original limestone, now entirely replaced by pyrite and dolomite. The buff veinlets are chiefly sericite, and the white veins that pass

through the whole mass are all dolomite. The vugs

in these rocks are lined with dolomite. An analysis

of such a rock is given below:

sericite, a persistent mineral. These paragenetic relations are summarized in Figure 15.

Locally the ore shows postmineral brecciation. This

is especially conspicuous in ore from the Ben Harrison

mine, from the Connor stope of the Honerine mine,

and from the Maybell mine, all in the Stockton area.

It is not believed that such brecciation is due to strong

faulting, however.

Fissure ore.-Closely associated with the sulphide

ores that have just been described as due to replacement of the limestones are the sulphide ores that are

due not to replacement but merely to fissure filling.

Strictly speaking, these are not directly the products

of rock alteration, but because they represent the feeding fissures traversed by the solutions that metamorphosed the limestones to ore, they will be discussed

here.

These fissure ores are essentially identical in composition with the limestone replacement ores just described. They are essentially sulphide ores, containing chiefly pyrite, sphalerite, and galena, and low in

quartz and calcite (which is locally manganiferous).

Some of the mining men believe these fissure fillings

to be higher in tetrahedrite and arsenopyrite than the

replacement ores. The writer was unable definitely to

confirm this opinion, but inasmuch as the fissure ore

associated with the hornfels in the Ophir Hill Consolidated mine is higher in tennantite than the replacement ore, there seems to be some foundation for it.

AnalysiS of dolomite replacing limestone of Ophir formation,.

'Ph drift, No.2 stope, Ophfr Hill Consolidated mine

[J. G. l<'airchild, anal~'st]

Si02

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3. 97

A1203_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1. 56

Fe203 Not found.

FeO________________ 212

MgO_______________ 16.28

CaO ___________ _____ 30. 16

Na20_______________ .10

K20_ ______ _____ . 33

H20 - ______________ . 02

H20+-_____________ .16

Ti02________________ .00

CO2 -- -- -- ---

P205------------- _ Cl _

F _

S _

MnO _

FeS2 - _

42.48

.03

Trace.

.75

.03

.59

1. 57

100.51

.32

100.19

Specific gravity: Particles, 2.854; lump, 2.710. Porosity,

apprOXimately 5 per cent.
The mineral composition of this rock, as computed I

from the analysis and checked against the microscopic

study, is as follows:

Dolomite _

Calcite _

Muscovite _

Quartz _

Fluorite _

83. 6

7. 0

4. 0

2.2

1.6

Pyrite _ _ _____ ________ 1. 6

Pyrrhotite____________ .1

Apatite______________ .1

The dolomite is slightly ferriferous and manganiferous. The calcite is probably residual from the original

limestone.

In some specimens the dolomite is massive, veined,

and partly replaced by sulphides, orthoclase, and

quartz. (See pI. 24.)

THEORY OF IGNEOUS METAMORPHISM AKD ORE DEPOSITION

AGENTS OF IGNEOUS METAMORPHISM

The intrusion of an igneous mass introduces at least

two factors-heat and mineralizer-rich solutionswhich tend to alter the country rocks. Pressure conditions are also changed, in general, but this change

can hardly be very effective in metamorphism associted with near-surface intrusions, dominantly of

crosscutting character, although it is doubtless of primary importance in deep-seated intrusions, especially

with those of concordant type. The intrusions of the

Stockton and Fairfield quadrangles were emplaced at

rather moderate depths in the earth's crust. (See

p. 69.) It seems permissible, therefore, to neglect the

pressure effects of the magmatic movements as metamorphic factors, although it will be necessary to consider the vapor pressures developed during magmatic

differentiation.

In view of these considerations, the igneous metamorphism of the Stockton and Fairfield quadrangles

is attributed to the action of heat and of heated solutions of magmatic origin. Although it is possible that

the country rocks themselves supplied a considerable

amount of water to assist in the changes, in view of

the strong mineralogic evidence of magmatic affiliations of the solutions and the adequacy of the magma

as a source, it is believed unnecessary to consider the

contribution of water by the country rocks.

"Normal" contact metamorphism involves, by definition, no significant addition of materials to the country rock from the magma. The metamorphism is due

to heat and to the presence of solutions that serve as

reacting media for the materials already present in

the rock. The heat effect, however, can not be attributed solely to the conduction of heat through the

walls of the magma chamber, as is clearly evident

both in this area and in many others, because, if it

were, the width of the aureoles of "normal" contact

metamorphism would depend primarily upon the size

of the igneous masses, not upon such factors as the

inclination of the contacts, the structure, and the rock

texture. The field facts suffice to show that even

"normal" contact metamorphism rests, finally, upon

the transfer of heat by solutions.

The igneous masses exposed at the surface are not

believed to be the sources of more than minor amount.'l

of the heated solutions that effected the metamorphism. They have themselves also suffered considerable alteration, and in the Bingham area, just north of

these quadrangles, changes involving addition and

subtraction of materials on a great scale have been

effected within the related porphyry there exposed.35

The sporadic distribution of metamorphism and the

occurrence of isolated metamorphic rocks, such as those

at Ophir and Dry Canyon, which are not in contact

with any intrusives now exposed, lead to the same

conclusion.

These facts seem to require the reference of the

metamorphosing solutions and the nOw expo~(\d porphyries to a common source at somewhat deeper levels

in the crust than those now accessible to observation.

This larger igneous mass must be considered as having been emplaced at high temperature, in the conditiOn of mutual solution of silicate-forming constitllents with a moderate content of mineralizers. It is

theoretically necessary that in any system not com·

pletely closed (and in nature a completely closed syscem is unthinkable) such a liquid phase must be accompanied by a vapor phase tending toward equilibrium with it. The work ()f Morey 36 has given

grounds for the belief that the vapor prf'ssures during

high-temperature stages of magmatic history are

rather moderate, and losses of volatile constituents

from the magma would accordingly be moderate also

at any considerable depth in the crust. Obviously,

any movement of the magma body to higher levels in

the crust would, through reduction in the external

pressure acting on the magma, lead to increased loss

of the vapor phase. As has been emphasized by

Spencer,37 such loss of volatile constituents must result in higher concentration of silicate-forming

materials in the residual liquid phase. This in turn

would induce crystallization of these nonvolatile constituents, which by increasing the concentration of

volatiles in the liquid, would lead to further increase

in vapor pressure.3S Cooling, of course, would also

act in the same direction, the crystallization of silicates

soBoutwell, J. M., and Keith, Arthur, Economic geology of the

Bingham mining district. Utah: U. S. Geol. Survey Prof. Paper 38,

pp. 162-172, 1905.

36 Morey, G. W., The development of pressure in magmas as a result

of crystallization: Washington Acad. Scl. Jour., vol. 12, pp. 219-230,

1922.

37 Spencer, A. C., Geology aod ore deposits of Ely, Nev.: U. S. G~c].

Survey Prof. Paper 96, p. 61, 1917.

38Morey, G. W., op. cit., I'l- 223-230.
leading to progressive increase in the vapor pressure

at equilibrium with the liquid during a fall in

temperature.

There is evidence, summarized by Ross,39that critical phenomena are not involved in magmatic differentiation, and accordingly that gas-phase reactions are

not necessarily to be expected in deep-seated rocks,

although he does not question that they are expectable

in near-surface volcanism, under lower pressures.

Ross has also adduced evidence tending to minimize

the potentialities of gas phases in metamorphism, because of their low specific heats and the very low

concentrations of the nonvolatile magmatic constituents that, according to the work of Morey, may be

expected in them. The argument is a strong one and

seems to the writer to place the burden of proof on

one who attributes deep-seated metamorphism to gasphase reactions.

Nevertheless, the existence of gas phases among

volcanic phenomena is unquestionable, and their

ability to transfer material in large quantities has

also been. effectively demonstrated by the work of

Allen and Zies 40 and Lacroix,41 while Niggli 42 has

brought forth the theoretical reasons advanced above

for believing that intrusions at shallow depths will

lose a portion of their volatile constituents in the

gaseous form. This would also accord with the work

of Morey and has been appealed to by Ross 43 as a

source of pressure for expulsion of the hydrothermal

residue of the magma from the magma chamber. Ross

also concludes, however, that such gas phases are, compared to liquid phases, of relatively small importance

in the transfer of material~ For these reasons the

writer believes that although true gas phases are probably developed in the differentiation of an igneous

mass at shallow or intermediate depths and that some

of the mineral transformations in the Stockton and

Fairfield quadrangles are to be attributed to reactions

of the country rocks with gas phases, nevertheless the

larger part of the metamorphism is probably due to

l:'olutionsordinarily called hydrothermal.

In describing the metamorphism of the Stockton

and Fairfield quadrangles, it has been pointed out that

many of the new minerals formed could be easily explained as products of reconstitution of materials al-

•• Ross, C. S., Physico-chemical factors controlling magmatic differentiation and vein formation: Econ. Geology, vol. 23, pp. 869-886,

1928.

•• Allen, E. T., and Zies, E. G., A chemical study of the fumaroles of

the Katmai region: Nat. Geog. Soc. Katmai series, No.2, 1923. Zies,

E. G., The fumarolic action in the Valley of Ten ThOUSandSmokes:

Idem, No.3, 1924.

'" Lacroix, A., llltude minliralogique des produits silicates de l'~ruption

du V~suve: Mus. hist. nat. Nouv. arChives, 4th ser., vol. 9, fasc. 1, 1907.

•• Niggli, Paul, Die leichtfliichtigen Bestandteile im Magma, p. 52,

Leipzig, 1920.

••Ross, C. S., op. clt., pp. 879-881.

ready present in the rock. This is " normal" igneous

metamorphism and is perhaps exemplified by the less

intense metamorphic facies of the Bowman limestone,

some parts of the Ophir formation, and parts of the

Oquirrh formation at Stockton. To this process is

due, for example, the formation of wollastonite in limy

sandstone or sandy limestone, of orthoclase and epidote from muscovite-calcite-quartz rocks, and of tremolite and diopside from sandy dolomite or dolomitic

sandstone. The work of Winchell 44on the very similar hornfels of the near-by Bingham district suggests,

however, that this process has been almost negligible,

most of the silicate minerals being formed from reaction of silica of extraneous source with the carbonates

of the limestones.

In addition to the possible reconstitution of materials already present in the rocks in response to the

changed temperature and chemical environment in

which they were placed by the igneous intrusions,

there is unequivocal evidence of great transfer of material. Evidence of the process is present in the ore

bodies, in such hornfels masses as those of the Ophir

Hill Consolidated mine, and in the jasperoids.

The sulphide ore bodies that have clearly been

formed chiefly by replacement of the country rock

manifestly represent material added from without.

They can not possibly be residual concentrations

formed by leaching of a limestone matrix containing

:ocattered sulphides, for there are no evidences of the

tremendous loss of volume in the limestone that such a

process would entail.

The Ophir Hill Consolidated ore body is well exposed, with its inclosing rocks. The slightly silty

limestones of the Ophir formation have been replaced

by lime silicate hornfels and finally by sulphide ores

on a great scale. The evidence that the replacement

was essentially volume for volume (with some slight

exceptions to be discussed below) is very good. The

limestones can be traced from their essentially unaltered facies directly along the strike into the most

altered facies without any appreciable difference in

thickness, certainly with no evidence of collapse or

mere concentration of impurities. The assumption

that there has been essentially no change in volume

during metamorphism can not be far wrong. The

analyses given on page 104, wit4 the mineral changes

therein reflected, show the remarkable chemical transfers that have occurred between the limestones and

the magmatic solutions.

For the purpose of this discussion it is unnecessary

to refer to the intermediate facies of the limestone but

merely to consider the essentially unaltered limestone,

No.1, the most highly silicated rock, No.4, and the

•• Winchell, A. N., Petrographic stUdies of limestone alterations at

Bingham: Am. Inst. Min. and Met. Eng. Trans., vol. 70, pp. 888-890,

1924.
sulphide-silicate ore rock, No.5. The specific-gravity

determina,tions show that the porosity of the unaltered

limestone is negligible; that of the hornfels, No.4, is

approximately 0.2 per cent, which is also negligible.

There are sporadic vugs in many of the hornstones in

the mine, and it is assumed, for the purpose of study

of transfers of material, that No.4 has a porosity of

5 per cent and No.5, the ore, about 6 per cent. Except

for this vug space, the replacement has involved no

appreciable change in the volume of the rocks. On

these assumptions a comparison of the chemical composition of the three rocks gives a measure of the material transferred during the metamorphism. The

following table shows, for Nos. 1,4, and 5, the weight

of each of the constituents determined in the analyses,

also the amount of material transferred to or from

each rock to produce the next one.

Material transferred to produce are from unaltered lime,stone

[Grams in 1,000cubic centimeters .. Figures approximate]

Material I Material Material

transferr£d transferred transferred

No.1 to produce No.4 to produce No.5 to produce

No. 4 from No.5 from No. 5 from

No.1 No.4 No.1

-------------.

Si02

____ 29 +930 959 -270 690 +660

AhOs ___ 33 +262 295 -20 273 +240

Fe203 ___ 11 +24 35 --------- 35 +24 FeO ____ 54 -17 37 +28 65 +10

MgO ___ 119 -70 50 +31 81 -38

CaO ____1,334 -770 564 -475 89 -1,245

Na2O--T------- +4 4 +17 21 +21

K20____ 3 +177 181 -48 132 +100

H20- __1 1 ------------ 2 -2 -------

-1

H20+__ 1 ------------- 2 +56 58 +57

Ti02 ___ --------- +13 13 -5 7 + 7

CO2____i1,154 -772 382 -310 71 -1,082

P206 ____1 1 +6 7 +6 13 +12

CL----i1 1 --------- ------- -1 S ______ . 1 +3 4 +24 29 +27

MnO __-1 7 -2 5 +7 13 +5

Fes2----i 10 +29 . 39 +907 946 I +936 PbS _____________

--- --------- +515 515 +515 ZnS _____________

---------- +540 540 +540 Cu __. __'_________

-- ---------- +14 14 +14 F ______ 1 _________

----------- ------- +9 9 +9

12,759 {+1,450 }2, 580 {+2,150 }3,601 {+3,150

-1,600 -1,150 -2,350

These figures show that in the metamorphism of the

unaltered limestone represented by analysis 1 to the

hornfels represented by analysis 4 very remarkable

additions of silica, alumina, potassa, and iron sulphide have been made to the rock, with minor additions of soda, titania, and phosphorus. The rock has

at the same time lost magnesia and especially lime

and carbon dioxide in great quantities. It is not certain that any change in total iron combined as oxide

has occurred, though there appears to be a notable

oxidation of the ferrous iron to the ferric state, a

common feature of contact deposits.46 The loss of

manganese may be insignificant, and it seems that the

•• Butler, B. S., A suggested explanation of the high ferric oxide coutent of limestone contact zones: Econ. Geology, vol. 18, pp. 398-404.

1923.

changes shown in other constituents may be accidental

as well.

If it is inferred, as seems probable, that the orebearing rock represented by analysis 5 was derived

from hornfels represented by analysis 4, there has been

a notable loss in silica, alumina, lime, potassa, 'and

carbon dioxide, but a very striking introduction of

metallic sulphides and water with smaller additions

of soda; magnesia, manganese oxide, phosphorus, and

fluorine.

The remarkable total quantities of transferred material are worthy of emphasis. The production of the

ore represented by analysis 5 from the relatively unaltered limestones of analysis 1 involves the loss of

fully 85 per cent of the materials originally present in

the rock and their replacement by the addition of materials whose total weight is greater than the weight

of the original rock, the whole having occurred without significant change in the total volume occupied by

the rock mass.

The quantitative implications of these figures are

perhaps more easily visualized when the ore bodies are

compared to the other hornfelses exposed in the mine.

According to Mr. H. M. Hartmann, general manager

of the Ophir Hill Consolidated mine, fully 1,200,000

tons of ore has been produced from this property.

This means roughly 11,000,000cubic feet of ore. The

ore was on the average of somewhat lower grade than

the specimen analyzed, but if account is taken of noncommercial stringers it is probable that at least this

volume of rock has been altered from a composition

roughly that of specimen 1 to that of specimen 5. In

addition to this, there must be fully twice as much

hornfels, say 20,000,000cubic feet of composition approximating that of specimen 4, as well as a great

deal of less metamorphosed limestones such as are

represented by specimens 2 and 3. (See p. 104.) Even

if these rocks of lower degree of metamorphism are

neglected a simple computation shows that into the

area centering in the Ophir Hill Consolidated mine

and covering about 3,000,000square feet, in which the

limestones are about 60 feet thick, the following

amounts of material at the very least have been.

introduced:

Kilograms

Si02" 900,000,000

AhOs __________________________ 270, 000, 000

Na2° "___10, 000, 000

K20 160,000,000

H20 + . 22, 000, 000

Ti02. 11,000,000

P20Ii--------------------------- 9,000,000

S_____________________________ 12,000,000

FeS2 380,000,000

PbS 200,000,000

ZnS 200,000,000

Cu____________________________ 5,000,000

F_____________________________ 3,000,000

Equivalent

In tons

990,000

300,000

11,000

176,000

24,000

12,000

10,000

13,000

419,000

220,000

220,000

5, 50n

3,300

2,403,800
STOCKTON AND FAIRFIELD QUADRANGLES, UTAH

the field relations that fully 70 per cent of the silica is

introduced material. In fact, the assumption that 10

per cent of the silica is residual from the limestone is

probably highly excessive. If it is assumed that the

total jasperoid in the Mercur district can be represented by a plate 12,000 feet in strike length by 500

feet in dip length by 10 feet in thickness, which seem

to be very moderate estimates (see fig. 12), and that

70 per cent of the mass is introduced silica, a total of

34 000 000 , , tons of silica has been introduced into the

limestone in this area. Probably not less than 40,000,-

000 tons of calcite has been removed from the same

area. When the siliceous alteration of the rocks with

which the gold ores are associated is also considered,

these estimates of material transferred must be admitted to be exceedingly conservative. The fact that

(lnly the precipitated material contained in the solutions is available for estimate and that additional material must have been carried off tends to emphasize

still further the great volume of material transferred.

The following minimum quantities of material have

been removed:

]dgO _

CaO _

co2_ - - - - - - - - - - - c - - - - - - - - - - --

Kilograms

64,000,000

1,026,000,000

964, 000, 000

Equivalent

in tons

71,000

1,133,000

1,063,000

2,267,000

The increase in total iron is very great when addition as sulphide is taken into account. The iron combined with oxygen shows no significant change, but

there is an advance in the state of oxidation. The

carbon dioxide removed is about 10 per cent in excess

of the chemical equivalent of lime and magnesia, pos-

:3iblypermitting oxidation of the iron by CO2 set free

through replacement by silica, as suggested by Butler.

Among the most striking changes are those involving the introduction of what are ordinarily considered

minor constituents-titania, phosphorus, and fluorine--in great quantities, considering the fact that the

{'stimate above given may. be so conservative as to

represent less than a quarter of the actual total

brought into these areas.

The changes effected by the metamorphosing solutions that produced the hornfels type of alteration

and the accompanying sulphide deposits elsewhere in

the area were very similar to those at Ophir but were

less striking and are less easily susceptible of quantitative estimates. vVhen the total transfer of material is considered the amount must be tremendous.

The transfer of material involved in the jasperoid

-variety of metamorphism is also very great. Unfortunately, it is not susceptible of anywhere nearly as

dose quantitative estimation as the transfer involved

in the hornfels alteration at Ophir. However, the following analysis of oxidized jasperoid from Mercur

shows the marked alteration which has occurred in

order to produce this rock from an ordinary limestone. 40

Analysis oj the Sparrowhawk ore

[w. F. Hillebrand, analyst]

Si0281. 70 H20- ____________ O.29

Ti02_________________ .20 H20+ 2.16

A120g ________________ 3. 24 SOg _ _ _ _ _ ____________ 2. 97

Fe203 5.41 P205---______________ .05

FeO_________________ .28 Sb2051.02

CaO_________________ .44 As20

5

________________ .40

BaO _________________ . 43 ]do _ _ _ ________ Strong trace.

MgO________________ .16 Te___________ Do.

K20___ ___ ___ ____ _ 1. 10

NaaO________________ .12 99.97

Li20 __________ Strong trace.

There has unquestionably been a great loss in total

volume of the rock during the change of part of it

from limestone to jasperoid, but it seems certain from

-

The only available clues to the composition of the

metamorphosing solutions lie in the effects of the solutions upon the country rock and in the products deposited by them. The substances known from their

precipitation to have been present in the solutions

include silicon, aluminum, iron, potassium, sodium,

water titanium, phosphorus, sulphur, lead, zinc, cop- , .

per, fluorine, boron, antimony, arsenic, and barIUm.

From general principles it may be assumed that water

was probably the most abundant of these constituents, despite the fact that fully fourteen times as

much sulphur, seven times as much potassa, twelve

times as much alumina, and forty times as much silica

as water have been fixed in the altered rock. The removal of such great amounts of calcite from the country rocks suggests that the solutions were rich in carbon dioxide, a common constituent of volcanic emanations, but this is by no means a necessary condition.

It is obvious that the solutions did not remain

purely magmatic aIter reaching the country rock, for

the products of reaction with the country rock must

surely have added much material to them. Many

other substances may have been present in the

solutions but not in sufficient concentration to be

precipitated.

NothinO' definite is known of the chemical character '='

of the solutions. General theories of magmatic differentiation would suggest that they were alkaline, as

they were derived from solutions saturated with alkaline silicates. The great quantities of the very strong

base potash which they contained also suggest this

character. However, there is some evidence that silica

at high temperatures is a much stronger acid former
than at low temperatures, and the silica present, together with sulphur and possibly great quantities of

carbon dioxide, may have been sufficient to give the

solutions an original acid reaction. The limestone

would then have acted as a neutralizing agent. The

narrowly selective action of the limestones in localizing metamorphism appears, however, to throw doubt

on the possibility that the solutions were acid, for if

they had been it would seem that one limestone should

have brought about neutralization nearly as well as

any other. The fact that the solutions crossed considerable thicknesses of limestone by following fractures but not permeating the walls or precipitating

any great amount of material, except in one particular

bed, suggests that the solutions were not acid.

Other evidence pointing toward an alkaline character of the solutions at the time of sulphide deposition, whatever the character at the time of leaving the

magma may have been, is summarized by Spencer.47

The theory that there is a general zonal arrangement of the metals introduced during mineralization

of an area is very attractive, and much evidence tending to support it has been presented. It is too much to

say that the facts observed in the Stockton and Fairfield quadrangles are opposed to such a theory, at least

in its simplest form, but it is most improbable that

the theory would ever have been originated in this

area.

Thus copper is usually considered to form in a zone

nearer the intrusive mass than lead and zinc. Although the lead-zinc deposits low in copper of the

Stockton mining district occur in very close association with igneous masses, copper is much more prominent at the Ophir Hill Consolidated mine than at any

other in the quadrangles, yet no igneous rock is exposed there. It is true that the metamorphism in the

Ophir Hill mine is of a type generally considered

more intense than that common near Stockton, but

the association of the richer copper mineralization

with the more intense metamorphism seems to the

writer a physico-chemical environmental association

governed by factors other than mere proximity to a

parent magma.

So far as surface exposures are concerned, there is

more evidence of close association between the jasperoid alteration in the Mercur-Lion Hill area and

igneous rocks than there is between the Ophir Hill

silicate-sulphide alteration and igneous rocks. The

evidence from innumerable localities about the world

however, is overwhelming that the temperature re-

•• Spencer, A. C., Geology and ore deposits of Ely, Nev.: U. S. Geol.

Snrvey Prof. Paper 96, pp. 64-68, 1917.

quired for the hornfels variety of alteration is notably

higher than that ordinarily prevailing during the formation of j asperoid. Despite the presence of some

tourmaline in the Mercur jasperoid it must still be

considered that the Ophir Hill deposit is a highertemperature facies than the jasperoid.

To the writer it appears probable that the essential

factors governing mineral deposition are temperature,

pressure, and concentration and relative solubilities of

the different components in the solutions. It is not

surprising that a general parallelism should ,exist in

the mineral sequences derived from similar magmas,

and that such sequences may be commonly zonal is in

accordance with observations made in many parts of

the world. However, changes in environment may be

occasioned by variations in facility of transfer of solution, by variations in thermal gradients due to fluctuations in igneous activity and variability of country

rock, and especially by variations in relative concentration of minerals due to local differences in magmatic evolution. These changes are, it seems, of preponderant effect over mere thermal control governed

by spatial relations. In other words, the factors involved in mineralization are such that zoning is to be

eommonly expected. They are also such as to demand

deviations from purely spatial zoning, and the record

from many parts of the world, including the area of

this survey, seems in accord with this statement.

It seems certain that any zoning which may be present in the mineral deposits is not so well marked that

any specific variety of mineralized rock will be found

beneath or in a given direction from any other specific

variety. The theory can hardly be applied as a guide

to prospecting.

The weathering of the nonmetamorphic rocks of

the Stockton and Fairfield quadrangles was not studied

in detail. The sandstones disintegrate chiefly by solution of the carbonate cement and by frost action, the

quartzites by frost action alone. The limestones generally weather to white, porous, earthy masses, composed chiefly of clay substance, presumably entirely

residual. The few shales disintegrate to clayey soils.

Both products are so readily eroded that they are

found only in sheltered areas.

Igneous rocks respond to weathering by alteration of

their feldspars to clay substance and of their mafic

constituents to "limonite" and presumably clay and

by freeing their quartz. It is probable that some silica, freed by disintegration of the silicates near the surface, is carried below and leads to some silicification,

especially of the volcanic rocks.
WEATHERING OF THE METAMORPHOSED ROCKS

lASPEROID

Alteration of the jasperoid rocks by meteoric agents

results chiefly in mechanical disintegration. However,

the sulphide, silicate, and carbonate constituents of

the jasperoid are attacked. chemically, and the result

is a wide diversity of minerals. In :fact, several elements found in the oxidized jasperoid have notbeen

recognized in hypogene minerals.

At Mercur orpiment, realgar, and scorodite occur in

oxidiz~ jasperoid, but realgar is the only hypogene

arsenic mineral observed. The scorodite occurs both

in crystalline and coUoform masses. Desiccation

cracks are evident in the colloform scorodite. The

crystalline scorodite is too fine grained for accurate

determination, but it clearly has a high birefringence,

with all indexes greater than 1.69 and less than 1.72.

The colloform variety has an index less than 1.70.

Malachite, azurite, aurichalcite, melaconite, and

crysocolla are the copper-bearing minerals of the

weathered jasperoid. No hypogene copper mineral

was observed in any of the unaltered jasperoid. Similarly, cerargyrite and argentojarosite occur in the

weathered jasperoid, though their parent silver mineral was not observed.

The stibnite alters to stibiconite and sulphur, which

occupy the space of the parent mineral.

Plumbojarosite is common in the oxidized jasperoid

of Lion Hill, and the lead recovered from these ores

was probably chiefly present in the form of this mineral. Some of it coats fractures in the j asperoid, and

~everal nodules of the rich horn silver formerly mined

In the Chloride Point mine, kindly supplied by

George St. Clair, are coated thickly with plumbojarosite. It is probable that this association is merely

fortuitous and that there is no genetic relation between the horn silver and the plumbojarosite.

Several potash-bearing clays occur as weathering

products of the jasperoid. They resemble kaolinite

in mean index but have a much higher birefringence

than kaolinite.

Gypsum, calcite as travertine or "onyx marble"

and in flat rhombs, and aragonite in long feathery

needles are common in the oxidized ore. In a specimen of oxidized jasperoid found on the dump of the

Mercur mine at Mercur aragonite needles have grown

into vugs in the jasperoid and inclose, toward the

center of the vug, radiating crystals of a milk-white

mineral which resembles but is not identical with

messelite.

Of course, "limonite" is common through all the

oxidized jasperoid. Discrimination of the actual mineral composition of this material was not attempted.

LIME SILIOATE AND SULPHIDE BODIES

The weathering of the lime silicate and sulphide

bodies involves the alteration of the silicates to clays

(chiefly potash-bearing), montmorillonite, calcite,

quartz, opal, chalcedony, gypsum, and possibly dahllite. The ferromagnesian minerals alter to clays and

"limonite." The manganiferous carbonates alter to

wad and psilomelane, less commonly to pyrolusite.

This is the source of the manganese mined by the

Ophir Hill Co. just south of the Canyon fault, north

of Ophir.

The alteration of the sulphides is fully as complicated. Pyrite alters to jarosite, " limonite," melanterite, and probably nontronite, as well as to sulphur,

locally. Galena alters first to anglesite, then to ceru-

!site where carbonates are in excess in the solutions.

However, where the solutions are high in sulphate the

alteration proceeds to plumbojarosite. In a few places

galena has been attacked by supergene solutions, which

have deposited thin films of chalcocite or covellite.

Locally the galena alters to pyromorphite, beudantite,

or mimetite, as in the gossan zone of the Honerine

mine. The arsenic for the beudantite and mimetite

is doubtless derived from arsenopyrite, as is that for

the rare scorodite.

Sphalerite oxidizes to produce the most diverse minerals of all the sulphides. The oxidized zinc ores of

the Hidden Treasure mine, the best example in the district, have been described and their genesis discussed

by Loughlin/8 who summarizes his conclusions in part

as follows:

The principal processes active in the deposition of the zinc

and copper carbonate deposits at Ophir may be summarized

as follows:

1. Ferruginous zinc blende was removed by oxidation from

mixed sulphide ore bodies, and the resulting zinc sulphate

solution migrated downward into the adjacent limestone, which

became replaced by smithsonite.

2. The replacement was accompanied by a considerable

shrinkage in volume, expressed by the open lamellar structure

of the smithsonite.

3. The lamellar structure bears a direct relation to fractures or other openings along which the zinc solutions invaded

the limestone. The lamellae tend to parallel these openings or

to lie concave to the more open parts of fractures. Where the

openings were far apart the lamellae present simple forms, but

where there was a network of fractures and the permeability

of the limestone was not uniform the forms of the lamellae are

very complicated.

4. The expression of shrinkage in lamellae rather than ip a

honeycomb structure is attributed to a rythmic order of replacement, similar to the process proposed by Liesegang to

account for diffusion banding-a process referred to in the

last few years by several investigators to account for banded

structure in numerous ore bodies.

5. The contrast between the large amount of shrinkage that

accompanied replacement at Ophir and the small amount that

took place in other districts studied by the writer is attributed

to difference in geologic conditions. In the other districts

there is reason to believe that the waters that cause the replacement had already taken in considerable carbon dioxide

before replacement of the limestone or related carbonate rock

48 Loughlin, G. F.. ZInc carbonate and related copper carbonate ores

at Ophir, Utah: II. S. Heol. Survey Bull. 690, pp. 12-14. 1919.
began and tbat more zinc carbonate could tberefore be deposited tban would bave resulted from simple reaction between zinc sulpbate and carbonate rock; furtbermore, fuat

replacement took place near and even below fue general or

local ground-water level, wbere tbe rock could become tborougbly permeated witb tbe zinc solution. At Opbir the opportunity for descending water to obtain carbon dioxide in

considerable quantity before depositing zinc carbonate was

relatively small, and there is no evidence tbat downward circulation of tbe water was impeded at tbe level of the smithsonite

deposits. Sucb conditions permitted direct molecular reaction

between zinc sulpbate and limestone, but fuey were not favor·

able to replacement volume for volume.

6. A small amount of ferruginous smitbsonite was changed

under oxidizing conditions into limonite and drusy smifusonite

low or lacking in iron. Psilomelane and associated drusy

smitbsonite had an analogous origin.

7. The scarcity of calamine and zinc-bearing clay at Ophir

is attributed to tbe fact that no volcanic rock formerly overlay tbe limestone in the vicinity of the zinc carbonate deposits.

It is believed that in districts where calamine is abundant the

silica of the calamine was derived from the decomposition or

alteration of igneous rocks (or other silicate rocks) above the

ore horizons. The fact that in the Ophir district calamine is

of later origin than bofu varieties of smithsonite shows that

silica does not combine with zinc to form hydrous silicate until

the carbon dioxide in solution has been reduced to a very

small quantity.

8. Oxidation of chalcopyrite, or cupriferous pyrite, did not

take place extensively until after the smithsonite bodies bad

been formed. The resulting copper sulphate solution migrated

downward and doubtless replaced in part smithsonite and in

Part limestone. The replacement of limestone, which received

no special study, was doubtless effected by reactions similar

to those involved in the replacement of smithsonite, summarized in the next paragraph. Where replacement was complete

copper carbonate ore was formed. This graded downward into

smithsonite ore or limestone.

9. Whether smithsonite is replaced by malachite or azurite

is thought to depend on the relative amount of carbon dioxide

in the SUlphate solution. If little is present, replacement by

malachite occurs until the carbon dioxide resulting from this

reaction is sufficient to cause the deposition of azurite. If

much carbon dioxide is originally present in the attacking so--

lution, fue smithsonite is replaced at once by azurite, no malachite being formed. Malachite was the principal mineral that

replaced smifusonite at Ophir.

10. Where the copper carbonate minerals were deposited in

openings carbon dioxide was also the determining factor.

Where it was relatively abundant azurite was deposited first,

followed, when the supply decreased beyond a certain undetermined point, by malachite. If zinc was present, derived

through the replacement of smithsonite, deposition of malachite would continue only until a certain copper-zinc ratio was

reached, beyond which the double basic carbonate aurichalcite

would be deposited. This ideal order, represented in several of

the Ophir specimens, may vary according to variations in the

solutions at different times and to other changes in the zone of

oxidation.

From the processes of deposition here described it is to be

expected that bodies of lamellar zinc carbonate like those of

Ophir will prove to be of high grade, owing to the complete

removal of limestone, but of small dimensions and confined to

the immediate vicinity of fractures and open bedding planes.

Such small bodies are not likely to lead to larger bodies of

massive ore, unless they lie near to ground-water level or to

some impervious stratum or fault fuat impounded fue waters

containing the oxidized compounds of zinc.

Owing to the invariable association of minute blebs

of chalcopyrite with all the sphalerite of the area, the

oxidation products of sphalerite always carry subordinate amounts of copper minerals. Smithsonite (commonly ferruginous), calamine (very common in the

Queen of the Hills mine), aurichalcite, hydrozincite,

and a zinc-bearing clay are the chief products of the

weathering of sphalerite and the attack of the supergene solutions on the underlying rocks. These are

commonly accompanied by malachite, azurite, and

chrysocolla, derived from: the associated chalcopyrite.

Some chalcanthite of similar origin occurs in the

Ophir Hill and Honerine mines. Sooty chalcocite

commonly coats chalcopyrite in small amounts.

MINING HISTORY AND PRODUCTION

The mining history and production of all the districts within the Stockton and Fairfield quadrangles

have been carefully summarized up to 1917 by

Heikes.49 The following account is almost wholly

quoted from him, with the addition of production data

and minor historical details covering the period since

1917.

The Rush Valley and Ophir districts, in Tooele County,

were formed June 12, 1864, and August 6, 1870, respectively.

These districts were originally part of the West Mountain

(Bingham) district. In 1863 they comprised the mining sec·

tions now known as Camp Floyd (Mercur), East and Dry

Canyon, Tintic, and Tooele districts. A narrow-gage railroad,

the Utah & Nevada Railway, was constructed in tIle seventies

from Salt Lake City to Stockton, and in 1905 this was made

broad gage and became a part of the Los Angeles & Salt Lake

Railroad. In 1912 a branch of this railroad was completed

from St. John to Ophir, doing away with a wagon haul of

about 16 miles.

RUSH VALLEY (STOCKTON) DISTRICT

Rush Lake, from which Rush Valley takes its name, is a

remnant of Lake Bonneville." In 1855 it was included in a

military reservation laid out by Lieut. E. J. Steptoe for the

purpose of securing to the military post at Camp Floyd the

meadow and pasturage about the lake shore. Gilbert says:

"The land surveys in the valley in 1856 did not include the

military reservation but showed the existence upon it of a

lake. According to Gen. P. E. Connor, who succeeded Colonel

Steptoe in 1862, there was then only a small pond, the remainder of the lake bed being occupied by meadowland. In

1865 the water began to increase, the greatest height being attained in 1876 or 1877, since which time it has subsided. Tbe

rise of the water submerged the meadowland and rendered

the reservation useless for its original purpose. It was therefore officially relinquished by tbe War Department in 1869.

In 1872, the water being near its highest stage, tbe lake was

surveyed in connection with the surrounding country by one

of the parties of the Wheeler survey, and the length was de·

., Heikes, Y. c., in Butler, B. S., The ore deposits of Utah: U. S.

Geol. Survey Prof. Paper 111, pp. 362-370, 382-387, 1920.

50 Gilbert, G. K., Lake Bonneville: U. S. Geol. Survey Mon. 1, p,

228, 1890.
termined to be 414 miles. In 1880, when the lake was visited

by the writer, it was said by residents to have shrunken to

half its maximum size."

The reservation 51 for the military post was sold by the

Government in 1861 and was repurchased in 1864 by General

Conner, who occupied it with a portion of the California and

Nevada Volunteers then stationed at Camp Douglas, near Salt

Lake. The town of Stockton was surveyed and organized in

March, 1864, and made a military post known as Camp Relief.

The Rush Valley deposits were discovered 02 in April, 1864,

by some members of Company L, Second Cavalry, California

Volunteers, who were guarding stock on the reservation. Assays from the first ledges discovered proved to be rich in

silver, and a mining district was organized. The first house

was built in Stockton during July, 1864, and in 1866 the town

had 40 families and 400 inhabitants.

Soon after the organization of the district Lieut. James

Finnerty erected a small trial furnace to test ore, and about

the same time a large one was built by the Rush Valley Furnace & Smelting Co. Both were only partly successful owing

to the imperfect quality of the fire brick used. Subsequently

Lieutenant Finnerty built a second furnace and ran it with

good results for a number of weeks, turning out a quantity

of metal from surface ore. Attempts to separate the gold and

silver from lead by means of the "Lyon process," which was

used to smelt the ores of the Perigo mine,"" in Gilpin County,

Colo., were made by the Knickerbocker & Argenta Mining &

Smelting Co. but were not successful, and the mines were

abandoned in the later part of 1865. The Monheim & Johnson

Co.'" completed a blast furnace in 1866 to treat ores from the

Delmonte and Great Basin ledges; J. W. Gibson in the same

year erected and put in operation a smelter with a capacity of

600 pounds a day. The Union Vedette says:

"Nine runs have been made of a hundred pounds each, and

300 pounds of metal was obtained, some of which has been

brought to this city and assayed by Bohm & Molitor and gives

$228 in silver per ton. The remainder is nearly pure lead.

* * *."

Soon after the close of the Civil War the volunteers at Camp

Douglas were disbanded, being relieved by regular troops from

the East. Most of those who had mining prospects, after meeting and amending the by-laws so as to make claims perpetually

valid which had but little work done on them, left the Territory to seek employment elsewhere. This action, which prevented all subsequent relocation of the same ground, greatly retarded and in fact prevented for some years the development

of the Rush Valley district.'"

The mining claims of the district center in the foothills 1 to

2 miles due east of Stockton and extend about 2 miles north

Hnd a like distance south.

The early conditions of mining, reviewed in brief detail by

Sloan 06 in 1873, are of interest. Sloan says in part:

"About midway the district and 1 mile from Stockton is a

heavy outcrop of a belt of blue limestone running east and

west. Dipping under this is a well-defined vein,3 feet in

width, carrying argentiferous galena, mixed with iron ocher.

The following mines are in this belt, whleh extends about a

mile in length. On the east end is the first discovery in the

district, called the Lincoln, now known as the Argent; de51 Union Vedette, published at Camp Douglas, Salt Lake City, Apr.

22, 1864.

52 Idem, Apr. 2, 1866.

53 Lyon process and Perigo mines, Colo,: UnIon Vedette, .Jan. 27

and July 18, 1866.

54 Union Vedette, Apr. 2, 1866.

65 Whitney's History of Utah, Salt Lake City, Utah, vol. 2, pp. 271-

275, 1893.

06 Sloan, E. L., Salt Lake City Directory, 1874, pp. 148-151.

veloped by shaft 100 feet in depth and one 50 feet; ore 50

per cent lead and 40 ounces silver to the ton, though one lot

yielded 60 per cent lead and 20 ounces silver. * * *

"Adjoining west is the Tucson * * *. One lot of ore

~'ielded 60 per cent lead and 87 ounces silver to the ton.

"The formation is somewhat broken west of the Tucson,

but it is evident the Bolivia is on the same vein; it is opened

by a shaft over 100 feet in depth, and there is much ore on

the dump * * *.

"West from the Bolivia is ilie Silver King, from which was

shipped the first carload of galena ore sent from Utah;

* * *. Average of ore in value about 50 per cent lead and

40 ounces silver to the ton.

"Toward the north part of the district is the Southport;

quartzite vein carrying galena and carbonates in large quantities; course of vein, north and south; • * • vein about

3 feet in width * * *. The St. Patrick, opened by an

incline of 100 feet. This mine at one time yielded a large

amount of ore.

"Up Quandary Gulch, one-fourth of a mile from Silver

Spring, is the Quandary lode, developed by a shaft over 100

feet in depth, with levels run therefrom.

" Opposite the gulch from the Quandary is the Great Basin

lode, opened by tunnel 100 feet and shaft 150 feet; has

produced high-grade ore.

"A short distance above the Quandary up the gulch is the

first extension north of the Great Central lode, a well-defined,

'true fissure vein, in quartzite, running north and south; ore

about 50 per cent lead and $150 per ton of silver.

"North from the Quandary, on the top of the hill, is the

mine Our Fritz, with shaft 100 feet in ore all the way, which

assays about 60 per cent lead and $94 in silver to the

ton; * * *.

"The First National (formerly Flora 'l'emple) is a welldeveloped mine with a shaft over 100 feet; strong vein amI

good body of ore."

Many of these claims, which were worked as individual properties in the early days, now form parts

of groups controlled by the Combined Metals, Galena

King, and Stockton Lead.

The Great Basin claim, which later became the

property of the Honerine, also known as the National, was included in the group of 77 patented mining claims and fractions transferred to the Bullion

Coalition Mines Co. in 1910. In 1924 it was taken

over, with additional claims, including the New Stockton (formerly the Ben Harrison) by the Combined

Metals Reduction Co. At the time of this survey in

1926 and 1927 part of this property was being operated by the company and part by lessees.

The property is opened by an adit 13,000 feet long. The

total output of the Honerine and its predecessors is reported'"

to have been 80,000 tons of ore valued at $1,250,000 to the

end of 1889. At that time there were 11,500 feet of openings,

and the greatest depth was 660 feet. A large concentrator

was in operation and has been worked intermittently up to

the end of 1913. Between 1890 and 1901 there appears to

have been very little ore produced from the Honerine mines;

at least, the United States Geological Survey is not in possession of the records.

Since the Honerine property has been operated by

the Combined Metals Reduction Co. the milling ores
have been treated by selective flotation in the plant at

Bauer. Considerable ore is shipped as mined, however.

The Jacobs smelter, built at Stockton in 1872, consisted of

three vertical blast furnaces and used ores from the Fourth of

July and Kearsarge mines, near Ophir. Th~ Fourth of July

was owned by Lilly, Leisenring & Co., of Philadelphia, who

were owners of the Jacobs works. In 1879 the Great Basin

concentrator, consisting of jigs, was installed in an extension

building covering the Jacobs furnaces, and in 18806

• was milling 100 tons of ore a day, producing 20 tons of concentrate.

One stack of the Jacobs smelter was in operation at the same

time, reducing about 25 tons of ore a day and turning out

about 5% tons of bullion assaying 100 ounces of silver per ton.

The Chicago smelter,"· long ago dismantled, was built on

the east shore of Rush Lake near Stockton, in August, 1873.

Its last operation was recorded in 1880. Huntley 60 says:

"The Chicago smelter is at Slagtown, on the eastern shore

of Rush Lake, about 2 miles south of Stockton. It was built

in 1873 by the Chicago Silver Mining Co., an English company,

which once owned the Chicago and the Queen of the Hills

mines, in Dry Canyon. It ran qUite steadily until 1877. It

was then idle until leased in 1879 to Mr. Brooks, who ran it

until the autumn of 1880,when it was shut down."

The Carson & Buzzo smelting works, about half a mile

south of the Chicago, erected two vertical blast furnaces in

March, 1873, and commenced operations shortly afterwards.

58 Rept. Director of Mint upon production of precious metals, 1880,

p. 130.

6. Cameron, J. E., jr., l\l. E., Mines aud furnaces of Ophir, Dry

Canyon, and Rush Valley districts: Utah Mining Gazette, June 6, 1874.

60 Precious metals: Tenth Census U. S., vol. 13, p. 450, 1885.

The ores used were obtained chiefly from the Utah-Queen

mine, owned by the same interests. Later Carson & Buzzo

rrected extensive reduction works at West Jordan.

The Waterman smelting works were the most important

and were operated at a later date (1886) than any in the

vicinity. Huntley 61 says:

"The first furnace in the territory, an unsuccessful reverberatory, was erected here in 1864 by General Connor and his

officers. It was bought in 1871 or 1872 by Mr. 1. S. Waterman. "' * * This smelter ran quite steadily for several

years on Hidden Treasure ore and some custom rock, but not

profitably. * * * During the four years ending April 1,

1878, 26,270 tons of ore were smelted and yielded 8,312 tons

of base bullion, which sold for $109.64 per ton, or $911,350.

During this time 3,300 tons of flue dust were caught, which

assa~'ed from 36 to 57 per cent lead and from 13 to 35 ounces

silver."

The production of the Rush Valley district during

its early activity is hard to ascertain. No complete

records are available, and estimates from the district

have been combined with those collected for the Ophir

district for the years preceding 1901. The figures in

the following table are those given by Heikes up to

1917; for the following years the figures were assembled from the annual volumes of Mineral Resources

of the United States, compiled by V. C. Heikes and

C. N. Gerry under the United States Geological Survey for 1918-1923, under the United States Bureau of

Mines for 1924 and later years.

I

Gold Silver

I

Copper I Lead I Recoverable zinc

Year Ore (short ------------ Total value tons)

Fine ounces I

I \

Fine ounces Value Value Pounds Value Pounds Value Pounds Value

i

"~.- ---

90L_ a4001--~ 54 $714 6,618

1

$3, 971 --------- ------- a 200,000 $8,600 ________J__ $13, 285

902 __ 496 64.00 1,323 7,479 3,964 --------- ------- 250, 651 10,271 --------- ------- 15,558

903__ 142 4.69 97 1,211 654 --------- ------- 27,009 1,134 --------- ------- 1,885

904 __ b 44, 145 292.99 6,056 176,510 101,052 5,248 $656 11,978,448 524,057 --------- 631,821

905__ b 40,431 322. 00 6,656 56,025 33,839 413 65 3,499,020 155,419

=========1=======

195,979

906__ b c 37,409 398. 88 8, 246 95, 861 64,2271 3,858 745 4,982,872 284, 024 357,242

907__ b 48,318 324.43 6,707 130,487 86, 121

1

318 63 6,622,042 350,968 443,859

908 __ b 2,6021 14.70 304 31,386 16,635 5,779 763 1,676,217 70,401 --------- ------- 88,103

909 __ b 5,627 21. 48 444 24,0961 12,530 1,781 232 1,213,266 52,170 --------- ------- 65,376

910__ b 1,981\ 27.32 565 15,888 8,580 10,354 1,315 965, 146 42,466 --------- ------- 52,926

91L_ 10,107 477. 38 9,868 102,863 54,517 12,689 1,586 4,969, 476 223, 626 --------- ------- 289,597

912__ d 45,453 I,141.31 23,593 261,588 160,877 319,859 52, 777 lOr 971,278 493, 708 --------- 730, 955

913__ b • 14,897 585. 09 12,094 128,675 77,720 29,521 4,576 4,619,259 203, 247 9,019 $505 298,142

914 __ 19,332 420.18 8,686 - 108,979 60,265 21,680 2,883 3,791,497 147,868 69,582 3,549 223, 251

915 __ 19,780 298. 15 8,230 90,666 45, 968 37,899 6,633 4, 151, 151 195,104 99,034 12,280 268,215

916__ 24,710 439. 31 9,081 108, 841 71,617 118,943 29,260 5,413,042 373, 500 136,615 28,306 501, 764

917__ 10,713 708.53 14,647 79,797 65,753 43,335 11,830 3,315,077 285,097 56,490 5,762 383,089

918__1 8,031 432. 43 8,939 78,247

1

78,247 26,991 6,667 3,776,351 268, 121 23,089 2,101 364, 075

019 __ 4,913 276. 38 5,713 50,033 56,037 24,598 4,575 2,676,501 141,855 70,698 5,160 213, 340

920 __. 3, 103 189.96 3,927 26,978 29,406 13,259 2,440 1,553,273 124, 262 25,143 2,037 162,072

92L_ 1,731 63.06 1,303 16,357 16,357 1,203 155 1,213,759 54,619 --------- ------- 72,434

922__ 1,754 70.89 1,465 17,175 17,175 3,962 535 1,172,502 ~4,488 19,012 1,084 84,747

923__ 3,865 141.50 2,925 32,367 26,541 14,758 2,169 2,567,672 179,737 --------- 211,372

924__ 4,549 172.91 3,575 26,519 17,768 10,198 1,336 1,851, 687 148,135 16,254 1,063 171,877

925__ f 19,859 637.75 13,184 97,739 67,831 90,459 12,845 4,929,432 428,861 901, 458 68,510 591, 231

926__ • 36,584 1,311. 99 27, 119 174,667 108,992 126,081 17,651 10,044,955 803, 596 1,962, 198 147,165 1,104,523

927-_ 66,573 2,949.10 60, 963 271,325 153,841 201,781 26,433 14,692,776 925, 645 3,634,134 232, 585 1,399,467

477,505 11,920.95 246,424 2,218,37711,440,485 1,124,967 188, 190 I 113, 124,359 7,022,826 500, 107 8,936,185

1

6, 560, 979

• Esthnated.

• Partly milling ore, concentrates produced.

• Mostly old tailings.

d Includes 27,647tons of old slag from early smelting operations.

• Includes 2,049tons of old tailings and slag.

I Includes 6,021tons of milling ore of which 500tons was old tailings.

• Includes 14,787tons of milling ore.
The ores in the Ophir district were discovered in 1865."

Treasure Hill, in East Canyon (now Ophir Canyon), had long

been a sacred spot whither the Indians repaired each year to

hold councils and to obtain metal for bullets. Soldiers of

General Connor's command, attracted by these legends, located a cropping of lead ore at the St. Louis lode, now known

as the Hidden Treasure mine. Other locations soon followed,

among which were the Pocatello, made near where the Velocipede was afterward located on Silver Shield Hill, and the

famous Wild Delirium (now part of the Ophir Hill Consolidated group), at the foot of Ophir Hill.

Very little work was done on the location until 1870, when

the excitement caused by the rich developments in the Little

Cottonwood district stimulated prospecting. In the summer

of 1870 A. W. Moore laid out the town of Ophir, and a new

mining district was organized. In August, 1870, horn silver

was found on Silverado Hill, perhaps by W. T. Barbee," and

the Silveropolis, Chloride Point, Shamrock, and other claims

were located. A few days after the discovery of the Silveropolis lode, the Mountain Lion, Silver Chief, Mountain Tiger,

Rockwell, and other locations were made on Lion Hill.

The nearest railroad point to Ophir in 1872 was the Utah

Southern Railroad, which terminated at Lehi and was reached

via Lewiston (near the site of Mercur) and Fairfield. In

1872 the Pioneer mill, belonging to Walker Bros., was treating

25 to 30 tons of ore a day, using a Blake crusher, fifteen 750-

pound stamps, an Aikin furnace, six Wheeler pans, and three

settlers. There were three smelting plants in the vicinity."

Huntley" says:

" The Ophir district * * * includes several canyons and

ridges on the western slope of the Oquirrh Range, the principal

of which are Ophir or East Canyon and Dry Canyon, containing the mining camps of Ophir City and Jacob City, resper

tively. There was much excitement in 1872, 1873, and 1874,

since which time the camp has gradually declined. At the

period under review there were not 50 persons where formerly

there were 1,000. The records showed about 2,500 locations,

on not over 150 of which was assessment work kept up. * * *

"Much of the ore of the district has been very rich, the

assays sometimes averaging among the hundreds and even

thousands. In East Canyon the ore was usually a very siliceous or milling ore, but that from Dry Canyon contained much

lead and was smelted. This. district has produced many million dollars-how many can never be known, as the mine

owners of the early days are scattered over the Pacific Coast.

••Wells, Spicer, Utah Mining Gazette, Jan. 7, 1874.

•• Huntley, D. B., Precious metals: Tenth Census U. S., vol. 13, p.

477, 1885.

•• Wheeler, G. M., U. S. Geog. Surveys W. 100th Mer. Prog. Rept.,

pp. 14-26, 1872.

•• Op. clt., pp. 450-454.

Many local attempts to treat the. ores were made in East

Canyon but were for the most part failures. The works remaining at the period under review were the buildings of the

Pioneer and the Baltic mills and the Cleveland and the New

Jersey arrastres.

"The Pioneer mill was built in 1871 by Walker Bros., of

Salt Lake City, to work ore from the ZelIa group and other

mines on Lion Hill. It was a 20-stamp dry-crushing silver

mill with an Aiken furnace and cost about $75,000. Many

hundred thousand dollars in bullion were extracted. The machinery was moved to Butte, Mont., several years ago. The

Baltic mill was a small 5-stamp mill, with two pans and a

settler, and was run by a turbine water wheel. It was not

worked regularly. The arrastres * * * were fairly successful, owing to the high grade and free nature of the ore.

Latterly ore has been shipped to Salt Lake City or to the

Stockton smelters. * * *

" The following works were built in early times but had been

moved away or were in ruins: Pioneer smelter, built in 1871;

probably produced 125 tons of bullion. Ophir smelter, built in

1872; produced but little. Faucett smelter, built in 1872; small

product. Brevoort mill, built in 1872; two st.amps. Enterprise

mill, built in 1873; five stamps. One mill (name unknown),

built in 1874; five stamps. Also several small arrastres run by

water wheels.

"The ZelIa group (East Canyon and vicinity) comprises the

ZelIa, Mountain Tiger, Silver Chief, and Rockwell, patented,

and several others unpatented. It is situated on the western

side and near the summit of Lion Hill. The mines were discovered in the autumn of 1870 and sold to Walker Bros. in

1871, who worked them until 1876, since which time they have

been leased. The ore outcropped in two places, the croppings

assaying $200 per ton. Three large bodies and several smaller

ones were found about 20 feet below the surface. * * *

The total product of this group was estimated at $750,000.

"The principal work (on the Monarch group) was done in

1875 and 1876. Since then the property has been leased.

* * * It is said that the ore averages 130 ounces silver per

ton with from nothing to $8 in gold, and from nothing to 12

per cent of lead. Much of it, however, would assay upward of

$500. * * * The total product to the close of the census

year was $117,500.

"The Douglas mine was located in 1871 and was worked

principally in 1875, 1876, and 1877. It has been idle or leased

since. It is situated near the western summit of Lion Hill,

about a mile southeast of Ophir City. It is near the Monarch

group, which it greatly resembles in gangue and ore. * * *

The total product is said to be at least 1,000 tons of l00-ounce

ore .

"The Trace group was located in August, 1878, and worked

in a small way since by the owners. * * * The total product to the end of the cenSRSyear was $11,565.

"The other mines of East Canyon and vicinity are:

Total length

ofopenings Total product

(feet)

Exchange and Sunnyside_______________ 1,000 $80,000

Lion_________________________________ 1,000 120,000

Chloride Point and others on Silveropolis _

Hill.

Miner' B Delight group _________________ a 300 _

Bonanza _

Cleveland Mining Co__________________ 1,430 100,000

• Incline;also other cuttInllS.

Several hundred feet of cuttings; produced many thousands in

early days.

Ore assays 19 ounces silver and 11 to 14 per cent lead; sells for

$7 per ton; total product, many thousand tons; 1,200 tons

extracted in census year.

Has produced considerable ore.

Ore assays $150 to $1,000 per ton .
Total length

Mines of openings 'Total product Remarks

(feet)

San Joaquin __________________________ 750 $35,000 Ore assays $100 to $400 per ton. Poorman _____________________________

b 500 Small. Little ore ever shipped. Buckhorn ____________________"________

a 300 ----------Ore assays 20 ounces silver, 35 per cent lead; much ore formerly

Mountain Gem and Antelope ___________

produced.

1,000 ----------

Surface ore assays 20 ounces silver, 30 per cent lead; several

thousand tons shipped in 1877 and 1878. California ____________________________

---------- ---------- Ore assays 25 ounces silver, 55 per cent lead.

-

"The Hidden Treasure mine [Dry Canyon] is situated on

a steep hillside above and three-quarters of a mile southeast

of Jacob City. It was located in 1865 as the St. Louis lodE:

by General Connor's soldiers, who had been told by Indians

of the outcropping boulders of galena. Little work was done

until April, 1870, when it was relocated as the Hidden

Treasure. The mine has been extensively but irregularly

worked since 1872. '" '" '" The ore assays from 15 to 40

ounces silver and 20 to 50 per cent lead. * '" '" During the

four years ending April 1, 1878, 28,400 tons were mined. Most

of this was smelted at the Waterman smelter, at Stockton.

The cash received for this amount of ore, whether sold as ore

or as bullion, was $988,700. Several thousand tons of ore

were produced prior to 1874.

"The Chicago mine was located in 1871 and sold to an

English company soon afterward. The mine was worked vigorously for several years but has been idle since 1876. * '" '"

The mine produced considerably over 12,000 tons of ore. This

company owns the Chicago smelter and when the mine failed

bought the Queen of the Hills, Flavilla, and Mahogany locations. They were located in 1870-71 and were worked extensively between 1873 and 1877 but very little since. Shortly

after the purchase the Chicago company carne to the fault

and failed. '" '" '" The product of these mines '" '" '" was

probably over $1,000,000.

"The Mono mine is situated half a mile north of Jacob

City. It was discovered in the autumn of 1871 and was owned

in the early days by Gisborn, Embody, Heaton & M.iller. It

was worked vigorously by them until 1875, when Gisborn

bought the remaining two-thirds interest for $400,000, mortgaging the whole to eastern capitalists for the money. About

three months after the sale a fault was found, or the ore

shoot 'pinched,' and only a small prospecting force was employed until June, 1879, since which time it has been idle.

'" '" '" The total product was not known, even by the

original owners, as they divided the proceeds after the sale

of each lot. By one it was placed somewhat over and by

another somewhat under $1,000,000.

"The Mono tunnel site is in the ravine 800 feet below the

Mono mine. Work was begun in 1872 or 1873. The tunnel

is about 1,100 feet in length. '" '" '"

"The Kearsarge mine, located half a mile west of Jacob

City, was discovered in 1871. •• '" '" The total product was

unknown, perhaps $1,000,000. '" '" '" A few hundred tons

of 40-ounce ore were produced.

"The Deseret group * * '" were located in 1870-71.

Work on them was begun in 1874 and discontinued January 1,

1879 '" * * The total production of the group was estimated at $30,000.

" The other mines of Dry Canyon are:

Total length

Mines of opening Total product Remarks

(feet)

Wandering Jew _______________________ 4,200 ---------- A few hundred tons of 30-ounce silver and 35 per cent lead ore

extracted. Utah Queen __________________________

, 900 ---------- Large amount of ore extracted. Sacramento ___________________________ 800 ---------- Considerable ore taken out formerly.

Mount Savage and 1. X. L _____________ 1,090 a 2, 100 Ore assays 40 ounces silver and 25 per cent lead. Emporia _____________________________ I, 600 $30,000 Fourth of July ________________________ b 440 al,OOO Ore assays 30 ounces silver and 35 per cent lead. Evening Star _________________________ 350 ---------- Some good grade ore shipped. Magnolia _____________________________

---------- ---------- Several hundred feet of incline and drifts; much money spent,

little received.

~~~:~~:~~:::~~~::~~::~:~~~~:::~:i::~~~-:~~~ ---------- Few hundred feet of work done.

---------- Do.

----------

----------

Since 1917, the last year covered by Heikes's

summary, the production of both the Rush Valley

and Ophir districts has been practically limited

to lead-zinc-silver ore and zinc ores, with almost

no siliceous or copper ores. The most consistent

producers have been the Ophir Hill Consolidated,

Bullion Coalition, Hidden Treasure-Cliff, Galena

King, Buffalo Consolidated, Cyclone-Tiptop (Stockton Lead Co.) and Ben Harrison. Smaller producers within the decade ending in 1927 include

the Kearsarge, Thad Stevens, Mono, Utah Queen,

Brooklyn, Surprise Tunnel, Chloride Point, Argent,

Twin Magnolia, Lion Hill, Ophir , Northern Light,

Queen of the Hills, Three Metals, Jim Fisk,
Lakes of Killarney, Calumet, Lookout, Muerbrook,

Southport, Salvation-Hercules, Virginia, and Legal

Tendel'.

The metal production of the Ophir district from

the beginning of operations to 1927 is shown in the

following table:

. Ore (short I

Gold ! Silver I Copper Lead Recoverable zinc

I

I Total Year I

tons) Fine I Fine I

value

Value I Value Pounds Value Pounds Value Pounds Value ounces

I

ounces I

$3,9891

---

9OL ______________________ ·29,600 192.97 312, 292 $187.375 1,199,476 $200,312 4,357,818 $187,386 ------------ ----- ..---- $579,062

902 _______________________ 34,115 164.33 3,397 252.326 133,733 913,622 111,462 3,358,535 137,706 ..----------- ------ ........ 386,298

903_______________________ 36,096 182.28 3,768 260,627 140,739 966291 132,382 2,557.142 107,400 ------------ ------- ..-- 384,289

904_______________________

• 37,571 186.02 3,846 240, 8~7 137,908 1,018,577 127,322 2,461,937 107,710 ------------ ----------

376,786

905 _______________________

• 39,172 208.00 4,300 265,531 160,381 1,092.784 170,474 3,306,794 164,454 ------------ ----------

499,609

906_______________________

• 40,848 249.00 5.147 257,175 172,307 1,566,831 I 302,398 7,408,228 422, 269 -..---..---..-- ----------

902,121

907 _______________________

• 50,241 395.20 8,169 I 335,376 221,348 I 739,203 147,841 5,913,148 313.397 ------------ ----------

690,755

908_______________________ • 53,002 221.64 4.582 . 328.606 174,161 1.053,359 139,043 6,000,168 252,007 ------------ ----- ..-..-- 569,793

909 _______________________

• 48,354 279.73 5,782 242, 340 126,017 736,518 95,747 5,941,455 255.483 ------------ ----------

483,029

910 _______________________

• 18,266 230.57 4,767 158.257 85,459 297.253 37,751 6,943,846 305,529 ------------ ----------

433,506

91L ______________________ 15.666 242.57 5,014 163.278 86,537 276,640 34,580 4,436,566 199,646 333,876 $19,031 344,808

912 _______________________ 54,523 276.97 5,725 269.887 165,980 745,525 123,011 6,279.109 282,560 373,870 25.797 603,073

913 _______________________

• 74,761 236.96 4,898 448,673 270,999 1.462,552 226,695 9,435,529 415,163 769,143 43,072 960,827

914 _______________________ 76.114 281.14 5.812 432,673 239,268 1,255,335 166,960 8,819,935 343,978 662,785 33,802 789,820

~~::: ::::::::::::::::::::: I 91.572 337.58 6978 637,643 323,285 2,212,377 387,166 12,232.549 574.930 1.099,138 136,293 1,428,65294,453 359.99 7,442 724,275 476.573 2,702,165 664,733 12,862,347 887,502 640,251 85.794 2,122,044

m:::::::::::::::::::::::1

80,944 277. 92 5,745 538,745 443,926 2,233,687 609,797' 9,581,712 824,027 573,528 58,500 1,941.995

, 73,444 207.45 4,288 512,702 512,702 1,669.363 412,333 9,135.999 648.656 38,586 3,512 1,581,491

d 66. 567 260.66 5,388 412, 292 461.767 1,290,464 240,026 8,387,451 444,535 ------------ --------- .. 1,151,716

920 _______________________1

• 61, 119 224.86 4,648 380,077 414,284 1.095,282 201.532 7,637,362 610,989 52.794 4,276 1,235,729

~:::-::: I 1,061 69.57 1,438 40,194 40,194 90,895 11,726 960,050 43,202 -----_ .._---- ----------

96,560

• 55,218 125.59 2,596 320,470 320,470 767,426 103,602 5,841,343 321,274 17,684 1,008 748.950

• 60,585 140.15 2,897 387,528 317,773 943,476 138,691 6,886,989 482.089 96,965 6,594 948,044

, 52,998 142.52 2,946 154,755 103,686 387,842 50,807 2,828,812 226,305 ------------ ---------- 383,744

925_______________________1

; 40, 358 305.85 6,322 302,742 210,103 886,271 125,851 5,890,562 512,479 212,159 16,124 870,879 926 _____________________..I 1,437 25.06 518 13,802 8,612 38.553 5,397 434,006 34,721 369,664 27,725 76,973

927 ..______________________1 1,271 26.84 555 10,791 6,119 24,440 3,202 314,019 19,783 392,02.3 25,090 C4 7411

,

---- ---

! 1,292,356 5,851. 42 120.957 8,403.944 5,941.706 27,666,207 4.970,841 160,313, 411 9,125,180 5,632,466 486, 618120, 645, 302

I

• Partly estimated

• Includes some lead and copper-lead concentrate.

, Includes 25,765 tons of shipping are and 3,921 tons of old tailings.

d Includes 21,362 tons of shipping are and some old tailings.

• Includes 17,322 tons of shipping are.

I Includes 1,571 tons of shipping ore.

• Includes 590 tons of shipping are.

h Includes 769 tons of shipping ore.

, Includes 502 tons of shipping are and about 8,000 tons of old tailings.

j Includes 1,433 tons of shipping are and 6,351 tons of old tailings .

The combined production of the Ophir and Rush Valley districts from the beginning of operations to 1927

IS given in the following table:

Gold Silver Copper Lead Recoverable zinc

Period Total

Fine ouncesj

I

\ value

Fine ounces Value Value Pounds Value Pounds Value Pounds Value

12,436.25 $257,080 3, 885, 9381 $4, 789, 719 I

- -------------------------- ------------,------------ 77,580,430 $4,335,597 -.---------- $9,382,396 ----------

-_.------------------------ 2,548.99 52,713 1,502,643 1,499, 742 ------------ I_.-.-.-.---- 10,377,100 447,930 -----.-.-.-- -.-.-.---- 2,000,385

--------------------------- 3,411. 06 iO,513 1,575,538 1,114,951 1,942,682 $253,315 17,358,239 657,364 -.---------- -.-------- 2,095,143

:::::::::::::::::::::::::::1 3,814.77 78,859 3, 198, 9781 1,871,001 9,611,665 1,468,571 79,663,742 3,752,851 ---.-.-.---. -----.---- 7,171,2827,774.82 160,716 5,556,912 4,095,728 15,592,164 3,190,060 134, 045, 464 7,688,374 5,033,641 $459,777 15,594,655

7__ .-------- -- --- _------- ___I 6,182.78 127,806 1,866,431 1,415,462 3,587,345 500,400 59,628,564 4,244,934 7,621,651 526,948 6,815,550

I

30, 733, 8661

----

36,168.67 747,687 17, 586, 440 114, 786, 603 5,412,346 378, 653, 539 21,127,050 12,655,292 986,725 43,060,411

1870-1880

1881-1890

1891-1900

1901-1910

1911-1920

1921-192

CAMP FLOYD (MERCUR) DISTRICT

The history of the Camp Floyd or Mercur district

has been summarized to 1917 by Heikes, and no activity has been reported in the district since his

summary was written.

The Camp Floyd district is about 55 miles south of Salt

'Lake City, in Tooele County, adjoining the Ophir mining distriCt. It contains three distinct camps-Mercur, the most important, in Lewiston Canyon; Sunshine, about 4 miles south

of Mercur in Sunshine Canyon; and West Dip (on the west

dip of the anticline), about 2 miles west of Mercur near the

western part of the range. The Salt Lake & Mercur Railroad,

which was dismantled in 1914, connected with the Los An·

geles & Salt Lake Railroad at Fairfield junction and furnished

transportation for the district. The district was first organized at the beginning of a silver excitement on April 16, 1870,
and later was practically abandoned until the discovery of

gold ore, which was successfully treated by cyanidation in

1891. On June 24, 1894, it was reorganized.

The early history of the district is reviewed by Huntle~',"

who says:

" The Camp Floyd district is south of the Ophir district and

is on the saIlle range. It is an irregular rectangle, from 7 to !)

miles on a side, the mines themselves, however, being included within an area of a square mile. * * * The Carrie Steele mine * * * was discovered in 1873 by Leandro

Steele; was worked from 1876 to July, 1879, when it was

sold to the Carrie Steele' Mining Co., of New York. * * *

One large body of antimonial ore 20 feet thick and 60 by 70

feet in extreme width and length was found at the surface.

The richest ore averaged $700 and occurred in a seam from 8

to 10 inches wide next to the roof. * * * The mill * * *

was built by an English company in 1872-73 to work the ores

of the Sparrowhawk mine. * * * It was purchased by

the Carrie Steele Mining Co. in 1879 and ran from May 10 to

August 15, 1880. * * *

"The other mines of the Camp Floyd district are:

Total

length of Total

openings product

(feet)

Sparrow Hawk _____ 6, 000 $300, 000 Ore similar to that

of Carrie Steele.

Star of the West. ___ 500 None. No ore shipped.

Silver Circle ___..____ 1,000 Small. In 1873 many thousand dollars spent

in prospecting.

Silver Cloud ________ 800 ------ - - Formerly shipped a

few hundred tons

of $30 ore.

Mormon Chief. _____ I, 000 --------- Little done since 1875. Elkhorn ___________ 500 50, 000

The production of the district from 1871 to 1881 is estimated

by Spurr 61 at 46,000 ounces of silver; the ores then worked

contained no lead, copper, nor gold. The gold production .of

the Camp Floyd district, which became important in 1892,

amounted in that and the succeeding year to about 19,000

ounces.

Gemmell os gives the following history of the district up to

1897:

"When the district was organized on April 16, 1870, ,it

naturally was called the Camp Floyd mining district. The

first location. in the district was a placer claim, located by L.

Greeley on April 20, 1870. Other and similar locations followed, but placer diggings could not possibly be made to pay,

for two very good reasons--Iack of gold that could be panned

and lack of water. The Sparrow Hawk, Last Chance, and

Marion claims were among the first lode claims located. Some

very rich silver ore was discovered on them (some of it going

$4,000 or $5,000 to the ton), and they were soon sold to an

English syndicate. The ore proved to be very' pockety,' and

after building a mill, spending about $700,000 and clearing

only about $100,000,the company suspended operations.

"Soon after the Sparrow Hawk discovery a rich strike was

made in the Carrie Steele. It is said that from this pocket a

few men took out about $83,000in three months. Other .strikes

"Tenth Census U. S., vol. 13. pp. 454-455, 1885.

'" Spurr, J. E., Economic geology of the Mercur minIng dIstrict;

U. S. Goo!. Survey Sixteenth Ann. Rept.• pt. 2, p. 355, 1895.

•• Gemmell, R. C., Eng. and Min. Jour., AprU 24, 1897.

67463-32-9

followed, and in 1872 and 1873 the hills were swarming with

prospectors. The town of Lewiston was built on the present

site of Mercur and was soon a full-fiedged mining camp.

* * * But no steady producing mines were found; the excitement began to die away, and Lewiston, which had grown

to a town of some 1,500 people by 1880, had dwindled down

to one house and to one inhabitant, Moses Manning, who remained to work out his own and others' assessments. It is

estimated that dUring this excitement about $350,000 were

taken out and that many times that amount was expended.

Machinery, supplies, and labor were all so high that it required

$60 ore to pay.

"On April 30, 1879, a German named Arie Pinedo located

the Mercur lode, believing he had discovered a valuable vein

of cinnabar and naming the claim after the German word for

mercury-Mercur. Some cinnabar was found, but not in paying quantities, and Pinedo soon abandoned the claim and left

the country. Other prospectors drifted in, and about 1883 the

gold ledge was discovered. The assay returns showed the

yellow metal to be present in paying quantities, but after

numerous attempts at panning with never a color, the prospectors gave it up.

"In March, 1889, Capt. Joseph Smith * * * put up a

mill on the Marion ground for the purpose of working the

silver ore and tailing dump. * * * After spending $9,000

or $10.000with no substantial result, Captain Smith was forced

to abandon the idea of making the silver ores pay. He remembered the stories of cinnabar and gold being found in the Mercur ore, sampled the vein in the summer of 1889, and got good

returns in gold. All thought of mining for silver or cinnabar

vanished, and during the winter of 1889--90 some work was

done on the Mercur lode. A 5-ton lot of the ore was brought

across the canyon to the Marion mill and treated with apparent success.

"Messrs. G. S. Peyton and H. W. Brown associated themselves with Captain Smith in March, 1890, and incorporated

the Mercur Gold Mining & Milling Co. * * * Twenty-five

thousand dollars were spent under the direction of Captain

Smith in building a mill near a spring at what is now called

Manning, about halfway between Mercur and Fairfield station.

This was an amalgamating mill, like the one previously built

on the Marion ground. * * * Five thousand dollars were

spent in developing the mine and fixing up the wagon road

from the mine to the mill. The attempt to treat the ore by

amalgamation proved a failure, however, and once again the

hopes of getting any money out of the ores of Camp Floyd

district were blasted. About 1,500 tons were put through the

mill that by careful sampling had averaged about $18 per ton.

Assays of the tailings showed an extraction of about 80 per

cent, but the clean-up, instead of amounting to about $21,000,

proved to be less than $5,000. Cyanide of potassium had been

used for cleaning the quicksilver, and subsequent experiments

proved that the gold had been dissolved and carried off by the

cyanide.

"About this time the successful treatment of gold ores by

the cyanide process became generally known, and * * * a

carload of ore was shipped to Denver for .a practical test. An

extraction of ahout 80 per cent was obtained by this test, and

in the summer of 1890 the mill at Manning was remodeled and

turned into a cyanide plant, by which the ore was successfUlly

treated. Oaptain Smith, having severed his connection with

the Mercur mine, turned his attention to the development of

the gold ledge in the Marion group of claims. He remodeled

and added to the amalgamating mill previously built, and by

June, 1893, started up the second cyanide plant in Mercur."

The successful treatment of the gold ores being assured, prospectors again swarmed in. Arthur Murphy and C. L. Preble
located two claims on the old site of Lewiston, staked them

out into town lots, and saw a new town (Mercur) grow to be

about the same size as Lewiston in its palmy days--about

1,500 inhabitants. By 1897 Mercur had become a regularly

organized municipality, with a water system and fire department. In 1900 the population reached 2,351, but dwindled in

the next decade to 1,047 inhabitants, and in 1913 [the town]

was almost entirely abandoned on the closing of operations by

the Consolidated Mercur Mines Co.

The following table shows the metal output from the Camp

Floyd district from the beginning of operations to the close

of 1917:

Metals produced in Camp Floyd district, by period a

[No production has been made since 1917J

i i Gold Silver

Period lOre (short tons) 1- -

Total gross

I

Fine ounces I

value recovered ! . Fine ounces i

Value Value

-_._--" ---,----- ! ------1

b !

---------.----------------- __ - __ 1- _____ ------ ------------- ------------- 46, 000

I

$55, 936 $55,936 _________________________________ I 1, 929, 993 382,790.00 $7, 912, 973 <7,912,973

____ ______________ _______________ 3, 653, 990 538,052.87 11,122,539 2, 760 I

1,576 d 11, 124, 115

I

5, 583, 983 920,842.87 19,035,512 48, 760 I 57,512 19,093,024

I

1871-1881

1890-1900

1901-1927

a From 1903 to 1907. 3,338 flasks of quicksilver were produced from the Sacramento mine.

b Spurr, J. E., Economic geologyof the Mercur mining district, Utah: U. S. Geol. Survey, Sixteenth Ann. Rept., pt. 2, p. 354, 1895.

'Average recovery, $4.10per ton.

d Average recovery, $3.04per ton.

From 1890 to the close of 1917 there were produced in the

Camp Floyd district by the Mercur, Delamar, Geyser-Marion,

Sacramento, Sunshine, Overland, Daisy, and La Cigale prop.-

erties 5,583,513 tons of ore valued at $19,034,984. All had

mills, and all except the La Cigale were successful in extracting fair values from the ores The first five properties paid

$3,881,323 in dividends to stockholders-the total amount

paid during the greatest activity in the district. The old

Mercur Gold Mining & Milling Co. paid dividends of $1,481,000,

and the Delamar Mercur Mines Co. dividends of $689,812.99 to

August 1, 1900.69 These two companies '0 had mined up to that

time 1,045,136 tons of ore at a profit of $2,181,401, or about

$2.09 per ton. From August 1, 1900, to 1913, inClusive, the

Consolidated Mercur Mine", Co. produced gold in precipitates

and bullion valued at $10,549,377, recovered from 3,291,485

tons of ore (including some tailings), or an average recovery

value of $3.20 per ton of material treated at a total cost of

$2.82 per ton." Dividends paid aggregated $1,374,500 to July

31, 1913. The Mercur & Brickyard-Golden Gate (Delamar)

property yielded 4,336,621 tons of ore, from which $16,419,541

was recovered, an average of $378 per ton. Dividends paid

during the life of the combined properties amounted to

$3,445,312.

After'the first test was made on Marion and Mercur gold

ore by amalgamation at the Marion mill in Lewiston Canyon,

the mill erected at Manning, in Fairfield Canyon, for the treatment of the ore in 1890 was similarly equipped, using pan

amalgamation.

In a personal communication 7' G. S. Peyton, discoverer of the

process that made Mercur famous, gives the early history of

the Mercur mill as follows:

" The Mercur mill was built under the advice and supervision

.of Joseph Smith, superintendent, at Manning in the years

1890-91 by the Mercur Gold Mining Co., organized in May,

1890. '" '" '" The amount of gold first saved by this process

of amalgamation was $3,060, representing about 15 per ceni

of the value of the ore. In July, 1891, a car of the $17 ore

•• Consolidated Mercur Gold Mines Co.'s annual report for the year

ending June 30, 1901.

76 Idem, p. 13.

71 Howard, L. 0., and Maguire, D., Cyanidation in the Mercur district of Utah: Pamphlet pUblished by Salt Lake Min. Rev., p. 20, 1913.

7. Letter from G. S. Peyton to V. C. Heikes, dated November 23,

1914. Mr. Peyton was then living at Rackerby, Calif.

was shipped to Denver for trial by the cyanide process, which

successfUlly extracted 92 per cent of the values. The amalgamation equipment and concentrators were then discarded,

and the cyanide plant completed and started in February,

1892, on ore averaging $12 per ton in gold, of which 86 per cent

was saved."

As experience was gained in the handling of the ores by the

new cyanide process the mill was enlarged. '" '" '" In 1896

the mill was treating 225 tons of ore daily, or altogether 63,480

tons for the year, averaging in value about $12 per ton in gold,

of which about 80 per cent was saved. The average cost of

mining and milling was about $2.80 per ton. The total amount

paid in dividends up to January 1, 1897, was $600,000. •

During 1897 and 1898 the Golden Gate mill was built at Mercur, and in 1900 the Delamar-Mercur Mines Co. and the Mercur

Gold Mining & Milling Co. were combined and thereafter call1~d

the Consolidated Mercur Mines Co. All of the ore from the

Mercur and Delamar mines was afterwards treated in the

Golden Gate mill, the Manning mill being used intermittently

by the company and lessees for the re-treatment of tailings.

The original capacity of the Golden Gate mill was 500 tom,

but by 1900 it was increased to 1,000 tons of ore daily.'·

A summary of the production and costs of operations is given

in the table on page 125.

The character of the oxidized and base ores of the Golden

Gate claims in the Camp Floyd district are discussed by D. C.

Jackling," who says:

"Locally, the ores are classified into three varieties, according to their mode of treatment:

"First, 'oxidized ores,' consisting of a mixture in which

the calcareous and siliceous varieties predominate and in

which the proportion of clay and talc is insufficient to interfere with percolation. This class of ore contains only an insignificant quantity of compounds of base elements, showing

only very small fractional percentages of mercury, as cinnabar and arsenic oxidized compounds.

"Second, 'talcy ores,' which are almost entirely clay and

talc and soft, decomposed porphyry. These ores, like the class

73 For a full description of the <>riginal plant on the Delamar property see Director of Mint Rept. upon production of precious metals for

1899, pp. 181-187, 1900.

•• Director of Mint Rept. on production of precious metals for 1899,

pp. 181-182, 1900.
I

--

Dividends

Year ending Tons base Tons \ Average Tailings Value Mining Milling Profit Per

Gross production Other income Total tons daily Recovery Total cost ext June3(}- ore oxidized ore tonnage loss per ton cost cost per ton Per cent tio Amount of gross

--

1901 b ______ $1, 493, 993. 80 ----------- --------- --------- 288, 295 875 $5.19 $0. 95 $6.14 -I-i- ______________ $3.18 $2.01 $235, 000 15.73 82 1902_______ 1, 457, 064. 47 $1,712.50 --------- --------- 321, 626 895 4. 53 1. 19 5.72 $1. 41 $2. 09 3. 50 1. 03 465, 000 31. 91 79

1903_______ 1,321,009.63 9,277.50 --------- --------- 335, 163 931 3.84 1. 21 5.05 1. 30 1. 58 2. 88 .96 330, 000 24.98 76 1904_______ 648,516.48 8,432.68 --------- --------- 266,701 630 2.86 1. 03 3.89 1. 40 1. 60 3. 00 .04 ---------- ------- 7

1905_______ 742,291. 76 12,385.15 79, 703 165,323 245,026 671 2.97 .985 3.95 1. 51 1.12 2.63 .34 25,000 3. 37 7

1906_______ 870, 887. 14 9,494. 77 126, 538 176,268 302,806 830 2. 80 .956 3. 76 1. 41 1. 07 2.48 .32 100,000 11. 48 7

1907_______ 642,843.90 14,445.10 110,069 135, 100 245, 169 672 2.62 .98 3. 60 1. 45 1. 18 2.63 .01 50,000 7.78 7

1908_______ 644,353.91 15,587.25 87,492 138, 737 226, 229 625 2. 85 .92 3. 77 1. 65 1. 26 2.91 .06 ---------- --- ---- 7

1909_______ 761,235.66 13,182.10 107,607 175,262 282,269 773 2. 70 .88 3. 58 1. 53 1. 09 2.62 .08 ---------- ------- 7

1910_______ 613,148. 92 12, 741. 12 99,447 132,190 231,631 638 2.65 .94 3.59 1.48 1.15 2.63 .02 ---------- ------- 7

191L ______ 550,695.70 7,933.49 78,897 131,622 0239,190 659 2.32 .88 3.20 1. 29 1. 04 2. 33 .01 ---------- ------- 7

1912_______ d 494, 133. 65 3, 970. 98 67,816 119,776 '201,652 560 2.45 .82 3.27 1. 32 1. 10 2.42 .03 30,000 6.01 7

1/10, 240, 175.02 109, 162.64 - - --- - - - -1- -- - -- - -- 3,145,757 731 3. 26 .99 4.255 I 1. 43 I I 1. 33 2.82 .455 1,235,000 12.54 7

-

I 1~

Oxide ore teated tons __ 1 175,262

Base ore treated do____ 107,607

Slime plant: Sand do_ ___ 34, 470

Oxidized do____ 34,470

Base do _

Slime do_ ___ 27, 523

Oxidized do____ 27,523

Base do _

Oxidized leached per cenL_ 84. 3

Base leached do_ ___ 100. 0

Total ore leached do____ 90.2

132, 190

99,447

82, 763

51,532

31,231

39,362

28,953

10,409

78.1

89.5

83.0

1911 I

I

131,622 I

78, 897

128, 031

74, 600

53,431

56,482

38,621

17,861

70. 7

77. 4

73. 2

. 1~ 1 1910 I

Ore and taIls leached per cent 1' 1

Oxidized classified do____ 64.7 60.9

Base classified do____ .0 41. 9 I

Total ore classified do____ 21. 9 52. 7

Ore :;Lndtails classified do _

Oxidized filtered do____ 15.7 21. 9

Base filtered ~ do____ .0 10.5

Total ore filtered do____ 9.8 17.0

Ore and tails filtered do _

In sand tails cents per ton__ 72 84

In slime tails do____ 54 83

75. 5

79.4

94. 8

85.0

79. 0

27.7

23. 8

26.3

24.5

119,776

67,816

110,126

61,854

48,172

49,377

33, 243

16,134

72.3

76.2

73. 7

76.4

86.0

90.2

87.6

77.1

29. 3

22. 6

26.8

23. 6

84

100

• Cyanidation in the Mecur district, Utah, pamphlet published by Salt Lake Min. Rev., 1913.

• For 11months.

• Includes 28,671tons of tailings.

d Corrected figures from company report.

• Includes 14,060tons of tailings.

f For 11years.

cent

raen

.8

.2

.0

3.5

5.3

4.5

2.8

5. 6

5.4

3.8

2.3

4. 9

6. 7
above are almost free from base-element compounds but

impos~ible of percolation, for the reason that on contact with

water they disintegrate and settle to an almost impervious

mass.

"Third, 'base ores,' consisting of a mixture of the above

classes, with the calcareous and talcose varieties predominating, and containing large quantities of base-metal sulphides.

Arsenic is the chief of these, occurring as realgar, orpiment,

and mispickel, in quantities sometimes as high as 50 per cent

but averaging not to exceed 2 per cent. Realgar is by far the

most plentiful of the arsenic-bearing minerals, fully threefourths of the arsenic appearing in this way. Antimony is

present as stibnite. Occasional small quantities of galena

occur.

"Considerable quantities of iron pyrites are frequently eucountered in minute crystals. Mercury is invariably present

but in less quantities than in the oxidized ores. Various

hydrous sulphates of iron are present, as well as oxidization

products of arsenic, both simple and in combination with lime

and magnesia. Some of the rare elements, most notably tellurium, are also present, in traces only. The clays of this class

of ore are invariably dark gray or black in color, due to a

considerable quantity of carbon, frequently as much as 4 per

cent, and in these are sometimes found organic compoundlS

which decompose potassium cyanide very rapidly. Silver is

very sparingly distributed in all classes of ore, rarely exceeding 1 ounce of silver to 10 ounces of gold. No metallic gold is

visible in any of the ores until after they have been roasted,

when occasional minute, irregular particles may be discovered

under the microscope. All the clean, base minerals are invariably poorer in gold than the gangue with which they are

associated. The clear crystals of realgar and orpimentcarry

none at all, or only traces, showing that the increased values

of the base ore are not directly due to these base-metal minerals. The gold in whatever ore found dissolves very rapidly

and completely in solutions of potassium cyanide, indicating

that it is very finely divided in whatever condition it occurs,

and these various facts have led me to the conclusion that the

gold in these ores is present in a finely divided amorphous

metallic state, having tile black or brown color characteristic

of the metal wilen in this condition, and consequently being

unrecognizable under the microscope in its naturally occurring

state."

The Marion was the first mill to be built in the Mercur area.

It was part of the old Sparrow Hawk works erected for the

treatment of silver ores in 1872-73, operated again on silver

ores in 1880, and again, for the last time in March, 1889, when

it treated 12 tons of ore daily by pan amalgamation with poor

success. In 1893 it was changed to a cyanide plant, the second

in the district, and was equipped for a capacity of about 50

tons of ore daily.

In 1893 the Camp Floyd district produced between 14,000

and 15,000 ounces of gold from the Mercur and Marion mines.

The scarcity of water was a decided obstacle to milling in

Lewiston Canyon until a pipe line was run from the Qphir district in 1893. Ore from the Marion was crushed to a size that

would pass through a %-inch mesh screen. The average cost

of mining and milling was said to be about $2 per ton.

The next summer (1894) the Geyser Co., whose claim adjoins the Marion, commenced work on a cyanide plant with a

capacity of about 100 tons of ore daily but finished it too

late in the year to permit much production. The ore took 90

hours to leach, as it was not put through screens but was

simply crushed in a Gates gyratory crusher. The amount of

cyanide consumed was about three-eighths of a pound per ton

of ore treated, and the cost of mining and milling was said to

be about $1.60 per ton.

In 1897 the Geyser-Marion interests were combined, and the

Marion equipment added to the Geyser mill. The yield in

gold from this property was reported to be $120,000 in 1899.

The property was last operated under its old name in 1900.

It was sold at sheriff's sale shortly after and worked with

little success by a new company until put into the hands of

a lessee, who barely succeeded in making the property pay

expenses. The dividend record shows nearly $100,000 was

paid to stockholders, and it is estimated that close to $500,000

in gold was recovered between 1893 and 1913.

A fourth cyanide plant was built on the Sacramento propeortyin 1895. Succe'ss was poor at first, owing to the baseness

of the ores, and thereafter only oxidized material was handled.

Roasting furnaces were added to an enlarged mill in 1901

and slime tanks the following year. The ore treated at the

mill averaged $4.60 in gold per ton in the beginning and as

low as $3 per ton at the end of operations in 1907. The costs

of mining and milling are said to have been about $1.50 per

ton, and the loss in the tailings averaged about $1 per ton.

The total value of the gold recovered during the life of the

mine is estimated at $1,500,000, and $308,000 was paid in

dividends. In addition, the Sacramento mine was for several

years the most important producer of mercury in Utah.

A few years after the first gold discoveries were made in

the Camp ]j'loyd district the Sunshine and Overland mills were

built at Sunshine, 4 miles south of MereuI', to treat gold ores

similar to those of Mercur. The Sunshine property was the

first to be equipped with a cyanide mill, which operated from

December, 1895, until October, 1896, milling about 9,000 tons

of $3 to $4 gold ore and obtaining about $7,000 in gold at the

expenditure of several times as much. In 1898--99, according

to Charles Butters," another unsuccessful effort was made to

treat the ore. In 1002 the mill was again started but was

closed at the end of the year after producing about $70,000

in gold bullion. In 1908 the mill was overhauled by the

Boston Sunshine Gold Mining Co., which treated 125 to 150

tons of ore daily, beginning in May, 1900. By July, 1910, thp

ore supply of the Sunshine mine was exhausted after slightly

over 50,000' tons had been treated with an average recovery

of $2.81, or a total of $141,532, extracted at a milling cost, it

is reported,'" of 88 cents per ton, with only 20 to 40 cents left

in the tailings. Dividends from these last operations aggregated $27,261. In all the Sunshine mine is believed to have

~'ielded about $221,000 in gold.

The Overland Co. erected the second mill in the camp, starting operations in November, 1898, on ore from its property.

It was the first mill in the district to use electric power. Development i.\1the upper levels of the mine was by an incline

shaft and in the lower by a vertical shaft that cut the ore bed

at 1,600 feet on the dip. The first ores treated ranged. from

$6 to $8 per ton in gold but decreased to about $2.30 a ton at

the last, yielding all but 40 cents of its gold, Which remained

in the tailings. The mill was closed for alterations in 1899

and was started again in 1901, having been enlarged to treat

500 tons of ore daily. It is reported that the cost of mining

was 85 cents and milling 25 cents per ton. The last work on

the property was done under a receiver in 1904--5. No dividends were ever reported, although the property had a record

of producing $219,646 in gold from about 156,000 tons of ore.

West Dip [West Mercur] is 4% miles northwest of Mercur

and was so named from the fact that the rocks at that point

dip about 45° W., in contrast with the east dip in the MereuI'

camp, on the opposite side of the anticline.

7. Personal communication.

7. Cyanidation in the Mercur district of Utah, pamphlet pubiished

by the Salt Lake Min. Rev., 1913.
Mining began in 1897, and in July, 1898,the Daisy mill, with

a capacity of 112 tons a day, was erected. It is said to have

produced $75,000 in gold precipitates up to the end of 1899.

In July, 1900, the Daisy mine and mill went into the hands of

a receiver. The Daisy property is opened by an incline shaft

to the 700-foot level and had ore assaying from $4 to $8 per

ton. The total cost of mining and milling amounted to $3 per

ton. Equipped about 1910 with modern machinery consisting

of classifiers, mixers, and filter presses, the mill was the first

to make a success of the West Dip ores. It was completely

destroyed by fire in 1917.

In December, 1898, a mill was started on the La Cigale property, which is developed by several shafts, the deepest in 1897

being 410 feet sunk on an incline of 45°. The ore is difficult

to treat, and at the end of 1899 work was abandoned. No

other attempts have been reported.

The minerals that have been reported from this

area or recognized in the course of this survey are

listed below in accordance with the classification of

Dana, with brief notes as to their occurrence.

Native gold has never been observed in any of the

ores, either of Mercur, primarily a gold camp, or of

any of the other mining districts. It is known only

from assays.

Native silver was not seen during this survey but is

reported to have occurred in small quantity in the oxidized ore of the Jim Fisk mine, in Ophir Canyon.

Native sulphur occurs as a product of oxidation of

metallic sulphides at Sunshine, in the jasperoid of

Lion Hill, and at the Mayflower mine.

Carbon, in some form, impregnates some of the

quartz of the MereuI' jasperoid and probably is a

minor constituent of some of the Ophir hornfels.

SULPHIDES AND ARSENIDES

Realgar (AsS) occurs at MereuI' in massive replacement deposits in limestone and' disseminated in

jasperoid.

Orpiment (As2Sa) occurs in the Mercur district,

both in limestone and disseminated in the jasperoid,

probably chiefly as an oxidation product of realgar.

Stibnite (Sb2Sa) is present as needlelike crystals replacing quartz in the jasperoid at MereuI' and Lion

Hill.

Galena (PbS) occurs in all the mines at Ophir, Dry

Canyon, and Stockton and in the Mayflower mine, in

West Canyon. It is both massive and intermixed with

silicates and other sulphides. Some galena from vugs

in the Ophir Hill mine has large octahedral faces

almost to the exclusion of the common cube form.

Argentite (Ag2S) was observed only in microscopic

blebs in galena from all the mines where galena is

found.

Chalcocite (Cu2S) forms sooty coatings on chalcopyrite along the Cliff fault in the Ophir Hill Consolidated mine.

Sphalerite (ZnS) is the common'hypogene zinc mineral and is present in all the sulphide mines from Lion

Hill to the Stockton district. It also occurs locally as

a "contact" mineral in the hornfels of the Soldier

Canyon stock.

Cinnabar (HgS) is disseminated in the altered limestones at Mercur. It was found in commercial quantities only in the Sacramento mine.

Covellite (CuS) occurs in the Kearsarge mine and

probably in a few other localities as a supergene sulphide, replacing chalcopyrite.

Wurtzite (ZnS) the hexagonal zinc sulphide, was

found in barrel-shaped crystals as much as 2 millimeters long coating chalcopyrite in vugs in the Ophir

Hill mine. No evidence was discovered bearing on

the question of hypogene or supergene origin.

Pyrrhotite (Fe"Sn+l) occurs in the Ophir Hill Consolidated mine, impregnating both the hornfels and

filling fissures. It is also present sporadically in the

Settlement Canyon contact rocks.

Bornite (Cu5FeS4) is rare, occurring only as a

supergene mineral along the Cliff fault in the Ophir

Hill mine.

Chalcopyrite (CuFeS2) is the common hypogene

copper mineral. It was found in the Lion Hill jasperoid, in the Ophir Canyon, Dry Canyon, and Stockton mines, replacing hornfels and limestone.

Pyrite (FeS2) is the most abundant and widespread

sulphide in the region. It occurs in all the mineralized

areas and as sporadic crystals in hornfels, rhyolite,

and monzonite, remote from other sulphides.

Arsenopyrite (FeAsS) was found in small amounts

in the Honerine and Ben Harrison mines.

SULPHARSENITES AND SULPHANTIMONITES

Boulangerite (5PbS.2Sb2Sa) occurs in considerable

quantity at the Mayflower mine, in West Canyon. It

was identified by M. N. Short.

Tetrahedrite (4Cu2S,Sb2Sa) was reported by Butler

as an uncommon mineral in the Honerine mine. It

was not found during this survey.

Tennantite (4C'u2S.As2Sa), the arsenic analogue of

tetrahedrite, was found in the Ophir HilI Consolidated

mine both as a vein mineral and as massive deposits

replacing hornfels. Qualitative tests by M. N. Short

showed a very low content of isomorphous tetrahedrite.

HALOIDS

Cerargyrite (AgCl), horn silver, forms waxy masses

in the mines of Lion Hill. It is confined to the zone

of oxidation, in which it was very richly concentrated.

Most of it has long since been mined.
Fluorite (CaF2) is a hypogene mineral in the mines

of Lion Hill, Ophir, Dry Canyon, and Stockton. It

is widespread but not abundant. It also occurs in

small quantities in some of the contact zones in Soldier and Settlement Canyons and the Stockton district.

OXIDES

Quartz (Si02) is the dominant mineral in the many

quartzite beds, as well as in most of the igneous rocks

and in the jasperoid and hornfels associated with the

ore deposits.

Chalcedony (Si02), a fibrous modification of silica,

occurs in the jasperoids and in the oxidized parts of

some of the ore bodies as a very subordinate mineral.

Tridymite (8i02), a hexagonal modification of

silica, is doubtfully present in some of the volcanic

rocks in the Fairfield quadrangle, as microscopic

rosettes in amygdules.

Opal (Si02.nH20) occurs as a supergene mineral in

some of the ore bodies and in some of the lavas.

Stibiconite (H2Sb205) forms an oxidation product

of stibnite in the jasperoids .of Lion Hill and Mercur.

It is uncommon.

Cuprite (Cu20) is present in minute amounts in the

oxidized ores of Dry Canyon.

Melaconite (CuO), the black, earthy variety of

tenorite, is a rare mineral of the oxidation zone 111 the

Lion Hill jasperoid.

Hematite (Fe20s) was identified in the contact zone

of the Soldier Creek stock as crystals of the specularite variety, as much as 0.5 millimeter in size. It probably also occurs, though not identified, in the gossan

zones of some of the ore bodies.

Magnetite (FeS04) is an accessory constituent of

most of the igneous rocks of the quadrangles, but was

not identified elsewhere.

Rutile (Ti02) is an accessory constituent of many

of the igneous rocks of the area. It is also present in

minor quantities in the Mercur jasperoid and in the

Ophir Hill hornfels.

Pyrolusite (Mn02) occurs along the Cliff fault in

the Cliff mine, in the limestone mass south of the

Canyon fault north of Ophir, and elsewhere, as a film

on quartzite. It is an oxidation product.

Goethite (Fe20s.H20) is probably the commonest

constituent of the gossan of the ore deposits. No distinction was attempted between this mineral, lepidocrocite, and amorphous "limonite." All are grouped

together in this report as "limonite."

Psilomelane, a hydrous manganese manganate, occurs as an oxidation product of manganiferous calcite

and dolomite at Ophir and Stockton.

Wad, a mineral resembling impure psilomelane, is

very common in small amounts in the oxidized zone

of the ore deposits.

CARBONATES

Calcite (CaCOs) occurs in the limestones, in the

hornfels, and in veins associated with sulphides. In

the hornfels it is commonly developed as platy crystals

parallel to the base but assumes scalenohedral forms

in vugs. Some white to pink calcite from the Ophir

Hill mine is manganiferous.

Dolomite (CaCOs.MgCOs) is very common both as

the dominant constituent of several sedimentary formations and as a gangue mineral of the ore deposits,

where it both replaces limestone and occurs as veins.

Some of the dolomite is slightly ferriferous and manganiferous, approaching ankerite in composition, but

no true ankerite was identified.

Siderite (FeCOs) is present in very small amount

as euhedral crystals, coating vugs in the hornfels of

the Ophir Hill mine. It contains a very small amount

of manganese.

Smithsonite (ZnCOs), mostly of the ferriferous variety, is a very common mineral in the mines of Dry

Canyon, from which large tonnages have been shipped

as zinc ore. It is also present in small amounts in the

Lion Hill and Stockton mines.

Aragonite (CaCOs), the orthorhombic modification

of calcium carbonate, is a rare mineral in this area. It

has been identified as a supergene coating in the vugs

of jasperoid from Mercur, along with an unknown

phosphate, described below (p. 130), and is also present as a supergene mineral in the Bullion stope of the

Honerine mine.

Cerusite (PbCOs), the common oxidation product

of galena, is very plentiful in the oxidized parts of the

ore bodies of Dry Canyon and the Stockton area.

Malachite (CuCOs.CU(OH)2)' the common basic

carbonate of copper, is rather plentiful at the mines of

Dry Canyon but is present only in very small amount

in Lion Hill, at Mercur, and at Stockton.

Azurite (2CuCOs.Cu(OH)2) is an uncommon oxidation product of chalcopyrite but was noted in small

amounts on Lion Hill, at Ophir, and at Stockton. It

is much more common in Dry Canyon.

Aurichalcite (2(Zn,Cu)COs.3(Zn,Cu) (OH)2) is a

common mineral, in small quantities, in the oxidized

ores of Lion Hill, Mercur, Dry Canyon, and Stockton.

Hydrozincite (ZnCOs.2Zn(OH)2) has been doubtfully identified by G. F. Loughlin from the Hidden

Treasure mine.

SILICATES

Adularia. See Orthoclase.

Orthoclase (K20.A120s.6Si02) is one of the component minerals of the monzonites of the area. The

soda-bearing variety, sanidine, is present in many of

the rhyolites and some latites; the variety adularia or

valencianite is very prominent in many of the hornfelses.
Microcline (K20.AI20a.6Si02) the triclinic potash

feldspar, is present in some of the monzonite stocks

but is not common.

Plagioclase feldspars, chiefly of the more sodic

varieties, are common minerals in nearly all the igne-

(JUs rocks of the area. Essentially pure albite

(NaAlSiaOs) is found in one or two of the rhyolite

dikes and in very small amount in the hornfels of the

Ophir Hill mine.

Hypersthene «Fe,Mg)O.Si02) is very common in

the volcanic rocks and also occurs in one of the monzonitic stocks in Tickville Gulch, where it is thought

to be an indication of contamination of the magma by

inclusions.

Diopside (CaO.MgO.2Si02) is a very common constituent of the hornfels of the area and is found at

Ophir, Dry Canyon, Soldier Canyon, Stockton, and

Settlement Canyon.

Hedenbergite (CaO.FeO.2Si02) has not been identified as a pure mineral but occurs in isomorphous

mixture with diopside in pyroxene from the Hidden

Treasure mine, as determined by its optical properties.

Augite, the aluminous pyroxene, is common in the

monzonitic and volcanic rocks of the quadrangles. In

some of the latite flows it is titanium bearing.

Wollastonite (CaO.Si02) is among the commonest

of the hornfels minerals. It is very abundant in the

Stockton and Soldier Canyon areas and in Dry

Canyon.

Tremolite (H~O.2CaO.5MgO.8Si02) is present in

small quantities in the hornfels at Ophir, is very abundant along the Cliff fault in the Cliff mine, and is a

subordinate" contact" mineral elsewhere in the quadrangles.

Actinolite (H20.2CaO.5(Mg,Fe)O.8Si02), the ironbearing tremolite, is common in the Hidden Treasure

mine and in Settlement Canyon.

Common hornblende is present in many of the volcanic rocks and in the monzonitic intrusives.

Nephelite (Na20.AI20s.2Si02) occurs in the nephelite basalt flow east of Sheep Ridge and in the sills

on South Mountain.

Grossularite (3CaO.AI20a.3Si02) occurs in the contact rocks of Settlement and Soldier Canyons.

Andradite (3CaO.Fe20a.3Si02) is the common garnet in association with the ore deposits in hornfels, at

Ophir and in the Honerine mine. Some segments of

the crystals are uniaxial negative and show a birefringence as great as 0.01. An andradite from the

Hidden Treasure mine is titaniferous.

Olivine (2(Mg,Fe)O.Si02) occurs in the lamprophyre dikes, in the olivine basalt flow, and in the nephelite basalt sills. No forsterite was found in any of

the hornfelses near igneous contacts.

Scapolite, of the variety near marialite (3Na20.

2NaC1.3AI20a.18Si02), has been doubtfully identified,

in very small amount, in a hornfels found in the

Hidden Treasure mine.

Vesuvianite, a basic calcium-aluminum silicate, has

been identified from the Soldier Canyon contact zone

and from the Honerine mine.

Zircon (Zl'02.Si02) occurs in microscopic crystals

in many of the igneous rocks of the quadrangles, as

well as in the hornfels of the Ophir Hill Consolidated

mine and in the Mercur jasperoid.

Topaz «AIF)2Si04) has been found in hornfels

from the Hidden Treasure mine but is very rare.

Zoisite (H20ACaO.3AI20a.6Si02) has been identified optically from a hornfels specimen collected at

the Calumet mine. It is a rare mineral in this area.

Clinozoisite, intermediate in composition between

zoisite and epidote, has been identified in microscopic

crystals in the hornfels of the Ophir Hill and Honerine mines. It, too, is uncommon.

Epidote, of the variety pistacite, rich in iron, of the

general formula H20ACaO.3 (Al,Fe) 20a.6Si02, is

very common in the hornfels zones at Ophir, Dry Canyon, Settlement Canyon, Soldier Canyon, and Stockton. It also occurs in the hydrothermally altered mon~

zonites, and some is found in the lavas.

Calamine (H20.2ZnO.Si02) forms microscopic rosettes in the oxidized ores of Lion Hill, Dry Canyon,

and the Bullion stope of the Honerine mine and in

the Galena King gouge in the Argent mine. It is an

uncommon mineral in this area.

Tourmaline, a complex borosilicate of aluminum

and other bases, commonly containing also hydroxyl,

fluorine, and alkalies, occurs in the contact zones at

Mercur, in the jasperoid at Mercur and Lion Hill, in

the Ophir Hill hornfels, and in the altered basal shale

of the Bowman limestone. It is a widespread mineral, but nowhere is it present in any large quantity.

Apophyllite (K20.8CaO.16Si02.16H20) has been

found in only one locality in the quadrangles. It occurs as very minute microscopic crystals in a veinlet in

a hornfels from the drain-tunnel level of the Honerine

mine.

Phillipsite «K2,Ca) O.AI20aASi02.4lhH20) is a

common zeolite in the latite flows of the Fairfield

quadrangle.

Analcite (Na20.AI20aASi02.2H20) occurs as a

common mineral in nephelite basalt and other volcanic

rocks and in veinlets through the Settlement Canyon

diorite stock.

Natrolite (Na20.AI20a.3Si02.2H20) is a zeolite in

the volcanic rocks of the Fairfield quadrangle. It is

not common.

Thomsonite ( (Na2,Ca)O.AI20a.2Si02.2lhH20) is

present in veinlets in the Settlement Canyon stock of
diorite and also in the lavas of the Fairfield quadrangle.

Epidesmine «Na2,Ca)O.AI20s.6Si02.6H20) coats

the joint planes in quartzite in the contact aureole of

of the Soldier Creek stock.

Muscovite (2H20.K20.3AI20s.6Si02) is a constituent of the Ophir formation and presumably other

shaly rocks and, in the fine scaly variety sericite, occurs as a hydrothermal mineral in hornfels, jasperoid,

and igneous rocks. It also occurs as a gouge clay

along faults, possibly in small part due to dynamic

metamorphism.

Biotite ( (H,K) 20.2 (Mg,Fe) O.AI20s.3Si02), the

common dark mica, occurs in the rhyolite, lamprophyre, monzonitic, and latitic rocks of the area.

No effort was made during the preparation of this

report to distinguish between the various members of

the chlorite group that may have been encountered.

All are hydrous magnesium-aluminum silicates with

usually some ferrous iron. Chlorites occur in the

hornfels of the Ophir Hill mine, and as alteration

products of biotite in many of the igneous rocks.

Serpentine, like chlorite, is a group name, including

many varieties. The composition is close to 3MgO.

2Si02.2H20, with a little ferrous iron. Antigorite,

the thin lamellar variety, replaces diopside in the

hornfels of the Honerine mine. Common serpentine

and bastite replace the pyroxene in several of the

igneous rocks.

Paligorskite, or mountain leather, a rather poorly

defined hydrous magnesium-aluminum silicate, occurs

along a fault in the Deseret mine, in Dry Canyon.

Iddingsite (MgO.Fe20s.3Si02AH20, with MgO

partly replaced by CaO in the ratio of 4: 177) is found

aEpseudomorphs after olivine in the volcanic rocks of

Step Mountain, in the Fairfield quadrangle. It is not

a common mineral.

Talc (H20.3MgOASi02) forms an alteration product of diopside and tremolite in the Lynch dolomite at

the Cliff mine. It is not a common mineral.

Sepiolite (2H20.2MgO.3Si02) occurs rarely as an

alteration product of diopside in the hornfels of the

Honerine mine.

The following clay minerals were identified during

this survey, but no attempt was made at an exhaustive

study of their occurrence.

Kaolinite (2H20.AI20s.2Si02) has formed as a result of hydrothermal alteration of the Tickville rhyolite and probably of the monzonites as well. It is

probably not a common clay mineral in this area.

Halloysite (3H20.AI20s.2Si02) occurs in many of

the igneous rocks as an alteration product of the feld.

spars.

.,.,Ross, C. S., and Shannon, E. V., The origin, occurrence, composi.

tlon, and physical properties of the mineral iddingsite: U. S. Nat.

Mus. Proc., No. 2579 (vol. 67, art. 7), pp. 1-19, 1925.

Montmorillonite (Mg, Ca)O.AI20s.5Si02.nH20)

has been tentatively determined by its optical properties as an oxidation product of the Ophir Hill hornfels.

Beidellite (AI20s.si02.nH20) was found in gouge

clays encountered in the Bullion crosscut of the Honerlne mIne.

Chrysocolla (CuO.Si02.2H20) was identified in

small quantities in the Lion Hill jasperoid and at the

Ophir Hill mine.

Nontronite (Fe20s.3Si02.5H20) was identified

from the Bullion stope of the Honerine mine and was

doubtfully determined from the Galena King gouge

and in the Argent mine.

Two unidentified potash-bearing clays were found

in oxidized jasperoid from Lion Hill, and Loughlin 78

reports a zinc-bearing clay, which came from the

Hidden Treasure mine, but these were not further

investigated.

Titanite (CaO.Ti02.Si02) occurs in most of the

monzonitic rocks of the quadrangles and is also present in many of the hornfelses, especially that in the

Ophir Hill Consolidated mine.

PHOSPHATES, ARSENATES, VANADATES, ETC.

Apatite (9CaO.3P205.Ca(F,CI)2) is present in practically all the igneous rocks of the quadrangles, in

the jasperoids, and in the hornfelses.

Dahllite, a carbonated calcium phosphate. was

doubtfully identified optically in a gouge clay from

the Muscatine mine, near Stockton.

Pyromorphite (9PbO.3P205.PbCI2) is found as a

mineral of the oxidation zone only. It occurs in many

of the gossan zones at Stockton and was found in the

Bullion stope of the Honerine mine, but nowhere in

more than minute amounts.

Mimetite (9PbO.3As20s.PbCI2) was identified as an

oxidation product from the gossan zone of the

Honerine mine, but in small amounts only.

Collophanite (3CaO.P205.nH20) occurs as metacolloidal masses in the basal shale of the Deseret limestone and in the upper part of the Madison limestone,

into which it has probably been carried by ground

water. In some parts of the Hidden Treasure mine

the collophanite and apatite are so associated as to

suggest that the collophanite has recrystallized into

apatite through the agency of the hydrothermal solutions which effected the ore deposition.

An unknown phosphate associated with aragonite

was found in a vug in jasperoid from Mercur. It

was impossible to separate enough of the material for

an analysis,. but phosphate was proved to be present

'18 Loughlin, G. F., Zinc carbonate and related copper carbonate ores

at Ophir, Utah: U. S. Geol. Survey Bull. 690, p. 7, 1919.
qualitatively. The mineral is white, with two cleavages, one nearly perfect, the other good. No crystal

faces are developed because of the intimate intergrowth with aragonite. The mineral has the following

optical properties: a 1.628, f3 1.651,y 1.678, all ± 0.003.

It is optically positive, with medium 2 V and an extinction angle of 27° between a and the best cleavage.

The acute bisectrix appears in the edge of the microscope field when the mineral lies on the better cleavage.

These properties are somewhat like those of messelite,

but comparison of material from the National Museum collections, kindly furnished by Dr. W. F. Foshag, shows that this has the a index much lower than

that of messelite and hence is probably a distinct

mineral.

The following rare phosphates, most of which are

new to science, have been recently described by Larsen

and Shannon 79 from a locality in Clay Canyon, Fairfield quadrangle. They were not found during this

survey. They occur as nodules in limestone.

Variscite (AI203.P,O,AH,O).

Wardite (CaO.2'(Na,K),0.6AI,OaAP20,.17H20).

Pseudowavellite (5CaO.6AI20aAP,O,.18H20).

Deltaite (SCaO.5AI,03.4P,O,.14H,O).

Dennisonite (6CaO.AI,03.2P,O •.5H20).

Dehrnite (14CaO.2(Na,K),OAP,O'.3H,O).

Lewistonite (15CaO. (Na,K) ,O,4P,O,.8H,O).

Englishite (4CaO. (Na,K),O,4AI20aAP20 •.14H20).

Millisite (2CaO. (Na,K)20.6AI,03.4P20 •.17H.0).

Lehiite (5CaO. (N a,K) .OAAI,03.4P.0 •.12H.0).

Gordonite MgO.AI.03.P.0 •.9H,O.

Scorodite (Fe20a.As205.4H20) forms a greenish

coating on jasperoid from Mercur. It is closely associated with pharmacosiderite, both being presumably

derived from oxidizing arsenopyrite.

Pharmacosiderite (3Fe20a.2As20s.13H20) occurs in

very small quantity on oxidized jasperoid from

Mercur.

Beudantite (2PbO.3Fe20a.2S0a.As20s.6H20) was

found in small quantities as a buff powder associated

with plumbojarosite in material from the gossan zone

(Ofthe Honerine mine, at Stockton.

SULPHATES

Barite (BaS04) in characteristic radiating blades

and plates is present in the jasperoid of Mercur and

Lion Hill. It is an uncommon mineral in the ore

bodies of the Honerine mine.

Anglesite (PbS04) almost invariably forms microscopic films around grains of galena which are altering to cerusite, but nowhere was any large quantity of

anglesite seen.

Gypsum (CaS04.2H20) is widespread in small

quantities as a product of the action of acid waters

,. Larsen, E. S., and Shannon, E. V., The minerals of the phosphate

nodules from near Fairfield, Utah: Am. Mineralogist, vol. 15, pp. 307-

337, 1930.

67463-32--10

derived from the oxidation of sulphides on limestone.

It occurs in all the mining areas.

Melanterite (FeS04.7H20) is found in the oxidizing ores of Mercur and Ophir and as long greenishwhite needles along the Cliff fault in the old workings

of the Ophir Hill mine.

Chalcanthite (CuS04.5H20) is a rare mineral in

this area, being found only in a few specimens from

the Ophir Hill mine.

Jarosite (K20.3Fe20a.4S0a.6H20) is a very widespread oxidation product of pyrite and chalcopyrite,

being found in the gossan zones of all the mines.

Some specimens carry a little lead.

A mineral intermediate between jarosite and alunite

was found in a specimen from the old Sparrowhawk

mine at Mercur. It occurs in minute hexagonal yellowish brown plates with the following optical properties: a 1.675 ±0.005, f3 and y 1.742 ±0.OO3,optically

negative, with 2 V =12°± 3°, the acute bisectrix nearly

normal to the plates. The birefringence is about

0.067. The pleochroism scheme is Z= Y>X. An

analysis by E. P. Henderson gave the following

results:

Insoluble _

Fe

2

03 _

AI203--- --- 80

3

_

K

2

0 _

Na20_ ---- -- -- __-- H

2

0 _

1. 43

40. 22

4.01

33.15

9.16

.90

11. 25

100. 12

0: 5~~~}2. 83 or 3 X O. 94

.4139 4.02 or 4X 1. 00

.0972} .0145 1. 08 or lXI. 08

. 6250 6. 07 or 6 X!. 01

This corresponds fairly well with the formula

K20.3R20a.4S0a.6H20. Combining the alumina and

the soda shows about 11 per cent of natroalunite present in isomorphous mixture. The ratio of Fe20a:

Al20a is 6.4: 1 and that of K20: Na20 is 6.7: 1.

Plumbojarosite (PbO.3Fe20a.4S0a.6H20) forms

dark-brown ocherous masses that consist of minute

hexagonal crystals. Most of it probably contains a

slight quantity of potassium jarosite isomorphously

mixed with it, as the highest refractive index is slightly

lower than 1.875, the w value given by Larsen 80 for

plumbbjarosite. It has formed indirectly from galena,

the process of alteration proceeding through the stages

galena~anglesite~cerusite~plumbojarosite. On one

specimen mimetite has formed from the cerusite,

yielding beudantite as an end product. The plumbojarosite is widely distributed and occurs in considerable quantity on Lion Hill, in Dry Canyon, and in the

Stockton area.

soLarsen, E. s., The microscopic determination of the nonopaque

minerals: U. S. Geol. Survey Bull. 679, p. 272, 1921.
Argentojarosite (Ag20.3Fe20g.4S0g.6H20), the silver analogue of plumbojarosite, was found on one

specimen from the Chloride Point mine on Lion Hill.

It is undoubtedly a rare mineral.

ORE DEPOSITS

CLASSIFICATION

Although a genetic classification is the most fundamental for a general study of mineral deposits, a clas~

sification based primarily upon metal contents and secondarily upon forms of the deposits is the most practical for this report. Although oxidized ores have contributed considerably to the mineral output, they are

so closely associated with the original sulphide ores

that the two are most conveniently described together.

The major divisions of the classification are based

solely on contained metals, and the subdivisions of

these classes are based upon the forms of the deposits.

The classification is as follows:

Gold and gOld-mercury deposits:

Bedded replacement deposits.

Veins and fissure' deposits.

Silver and silver-lead deposits: Bedded replacement

deposits.

Lead-silver-zinc-copper deposits:

Bedded replacement deposits.

Irregular replacement deposits.

Veins and fissure deposits.

BEDDEDREPLACEMENT DEPOSITS

The bedded replacement deposits of gold and of

gold and mercury are all in the southern part of the

area, near the now abandoned towns of Mercur, Sunshine, and West Mercur (West Dip).

At Mercur the ores are confined to beds within the

portion of the "Great Blue" limestone below the

Long Trail shale member, but at Sunshine they occur

in part just above the shale as well as in the lower

beds, and at West Mercur they are in strata well

above the Long Trail shale.

At the time of this survey none of the mines were

accessible except for small portions of the near-surface workings, and the following descriptions are

based almost entirely on the literature descriptive of

the deposits.S! Of these papers, the report of Butler

81 Hllls, R. c., Ore deposits of the Camp Floyd mining district,

Tooele County, Utah: Colorado Scl. Soc. Proc., Aug. 6, 1894; vol. 5,

Pp. 54-65, 1898. Spurr. J. E., Economic geology of the Mercur min·

Ing district, Utah, with introduction by S. F. Emmons: U. S. Geol.

Survey Sixteenth Ann. Rept., pt. 2. pp. 395-455, 1896. Gemmell,

R. C., The Camp Floyd mining district and the Mercur mines, Utah:

Eng. and Min. Jour., vol. 63, pp. 403-404, 1897. Dern, G. H., The

geology of Mercur: Mines and Minerals, vol. 24, pp. 543-545, 1904.

Palmer, L. A., Milling practices at the Consolldated Mercur: Salt Lake

Min. Rev., vol. 10, p. 16, 1909. Allen, R. H., Mines and mills of the

Consolldated Mercur Mines Co,.: Eng. and Min. Jour., vol. 89, pp.

1273-1277, 1910. Maguire, Don, and Howard, L. 0., The romance of

a famous gold mine: Salt Lake Min. Rev., June 15, 1913, pp. 13-15;

June 30, 1913, pp. 13-17; July 15, 1913, pp. 10-15. Butler, B. S.,

The ore deposits of Utah: U. S. Geol. Survey Prof. Paper Ill, PP.

388-395. 1920.

is the latest and summarizes all the previously published papers as well as the information placed at his

disposal by the officials of the Consolidated Mercur

Mines Co. Butler's discussion S2is given in the present summary, with slight modifications:

The accompanying generalized section (fig. 16) through the

ore-bearing formation of the Mercur district was furnished

by the Consolidated Mercur Co. It does not represent the

thickness of the different formations at any given point but

is an approximate average of their thickness as they have

been encountered in the mine workings.

The names given for the strata in the general section of the

ore-bearing formation of the Mercur area are those in common

use and do not necessarily represent the character of the material-in fact, some of the beds called I, porphyry" contain

fossils and are generally recognized to be sedimentary.

At the base of the ore series is a massive blue limestone with

beds of shaly material. These are unmineralized and practically unaltered. Overlying this is the "silver ledge," •• which

is a .cherty, rather porous mass resulting from the silicification of limestone. It carries silver and in places is a commercial ore. Locally, notably in the anticlinal body in the Brickyard and in the Geyser mines, gold ore has been mined from

the silver vein.

Overlying the silver ledge is the Magazine vein. The lower

part, known as the Hard Magazine, is a cherty material resulting from the silicification of limestone and in many places

closely resembles the silver vein; commonly, however, it is

more massive and does not possess the same porous character.

The upper part, known as the Soft Magazine vein, is a shaly

material, light colored and banded where oxidized and black

where unoxidized. The Hard Magazine is about 20 feet thick

and the Soft about 7 feet. Both carry gold and have been

mined.

Overlying the Magazine vein and about 30 feet of cherty

material (altered limestone) that carries little gold .is the

shaly Apex vein, which is about 8 feet thick and carries gold.

It is overlain by about 4 feet of cherty material that is not ore

and by 60 feet of relatively unaltered limestone.

The Mercur vein, which lies next above, is 20 to 25 feet

thick. Its upper 4 feet is known as the Mercur vein "porphyry." Its lower 20 feet is separated into two parts by the

Mercur vein footwall, a thin persistent layer of shaly material. The upper 12 feet is known as the Mercur vein and the

lower 6 feet as the Lower Half. The Mercur vein is characterized by nodular cherty masses, which are present where

the limestone is little altered and appear to be original in the

limestone rather than a result of mineralization. In many

places the Mercur vein has been altered to a cherty mass very

similar to the silver ledge and the Magazine vein. The Mercur vein" porphyry," where seen in the mine, is commonly a

rather massive gray rock that is soft and easily penetrated

by the pick. It is of rather shaly texture and appears to be

an altered sedimentary rock.

Above the Mercur vein " porphyry" is about 36 feet of lime

stone followed by about 6 feet of shaly fossiliferous material,

gray where oxidized and black where base. This is known as

the middle streak and is gold bearing. Next above is 20 feet

of limestone, above which lies the highest mineralized zoneabout 40 feet of shaly and siliceous material, as follows:

82 Butler, B. S., op. cit., pp. 392-395.

•• The silver ledge is jasperoid and has been described on pp. 97-101.

It is properly called, from its topographic expression, a ledge, but the

name ledge Is hardly applicable to the gold-bearing ore beds, as they

are not at all conspicuous in the topography.-J. G.
Upper vein footwall, 5 feet; upper vein, 8 feet; upper vein

porphyry, 20 feet.; shale, 8 feet. Overlying this is the massive

blue limestone.

Upper vein

Upper vein footwall

IfII

Shale

~

~

=

= =

= =

= =

Cherty

formation

+++++

+ + + +

+ + + + +

+ + + +

FIGURE 16.-Generalized section of the ore beds in the

Mercur district. After Butler

The beds are cut by a series of fissures striking east of north

and dipping very steeply west. The ore shoots follow approximately the intersectiop of the fissures with the ore beds. The

relation between ore bodies and fissures is, however, less striking in this district than in the Ophir and Stockton districts.

Spurr believed that both the gold and silver" ledges"

were localized along sills of Eagle Hill rhyolite and

indicated the outcrops of the supposed sills on his map.

The detailed mapping of the surface geology during

this survey has failed to confirm the presence of these

sills, and, in the opinion of the writer, the rocks mapped

by Spurr as porphyry are, except near the Sacramento

mine, not igneous but merely weathered limestone, perhaps in part hydrothermally altered as well.

Butler says: 84

There has been much mmmg development in the district

since the time of Spurr's investigation, and exposures in the

ore zone are far more extensive, giving a correspondingly favorable opportunity for observation. The writer was informed

by the management of the Consolidated MereuI' Mines Co.

that developments had failed to show the presence of thin

porphyry sheets in connection with the ore zones, and an

examination of some of the best exposures in the mine failed

to disclose them. Most of the rocks are much altered, and a

sheet of altered porphyry might well be mistaken for an altered sediment, but it was possible to trace several supposed

porphyry beds along the strike into unmistakable sedimentary

rock. Moreover, several shale beds, commonly called "porphyry," carry abundant fossIls that leave no doubt of their

sedimentary origin.

The writer did not spend sufficient time in the district to

follow out the supposed porphyry horizons in detail. At several points he was unable to recognize any porphyry and believes that porphyry at these horizons does not form continuous sheets extending out from the main masses. * • *

A.lteration.-".rhe alteration of the rocks is largely dependent

on their original character. Many of the limestone beds are

silicified to a cherty quartz (jasperoid) with small amounts

of sericite. The shaly beds appear to have suffered less

alteration, though they have probably gained silica anti

possibly some potassium, which have formed sericite. The

potassium, however, may have been originally present in the

shale. Most of the ore contains also considerable barite amI

secondary calcite. The principal metallic minerals are pyrite,

realgar with some orpiment, and cinnabar.

The following analysis" is of sulphide ore from the Grasshopper shaft of the Golden Gate mine:

Per cent

Silicon dioxide (Si02) 66.42

Titanium dioxide (TiO.)_________________ .85

Aluminum sesquioxide (AI.O.) 14.85

Iron sesqui~xide (FOe.)O.)----------------} .31

Iron protoxIde (Fe _

Iron disulphide (FeS.)___________________ 6.60

Calcium oxide (CaO) . 35

Barium oxide (BaO)____________________ .19

Magnesium oxide (MgO) .83

Potassium oxide (K.O) 2.73

Sodium oxide (Na.O)____________________ .13

Lithium oxide (LkO) Very strong trace.

Water below 110° C______________________ .53

•• Butler, B. S., op. cit., pp. 390, 393-395.

8li Spurr, J. E., op. ·cit., p. 424.
relation between ore bodies and fissures is, however, less striking in this district than in the Ophir and Stockton districts.

Spurr believed that both the gold and silver" ledges"

were localized along sills of Eagle Hill rhyolite and

indicated the outcrops of the supposed sills on his map.

The detailed mapping of the surface geology during

this survey has failed to confirm the presence of these

sills, and, in the opinion of the writer, the rocks mapped

by Spurr as porphyry are, except near the Sacramento

mine, not igneous but merely weathered limestone, perhaps in part hydrothermally altered as well.

Butler says: 84

There has been much mmmg development in the district

since the time of Spurr's investigation, and exposures in the

ore zone are far more extensive, giving a correspondingly favorable opportunity for observation. The writer was informed

by the management of the Consolidated Mercur Mines Co.

that developments had failed to show the presence of thin

porphyry sheets in connection with the ore zones, and an

examination of some of the best exposures in the mine failed

to disclose them. Most of the rocks are much altered, and a

sheet of altered porphyry might well be mistaken for an altered sediment, but it was possible to trace several supposed

porphyry beds along the strike into unmistakable sedimentary

rock. Moreover, several shale beds, commonly called "porphyry," carry abundant fossils that leave no doubt of their

sedimentary origin.

The writer did not spend sufficient time in the district to

follow out the supposed porphyry horizons in detail. At several points he was unable to recognize any porphyry and believes that porphyry at these horizons does not form continuous sheets extending out from the main masses. * * *

Alteration.-The alteration of the rocks is largely dependent

on their original character. Many of the limestone beds are

silicified to a cherty quartz (jasperoid) with small amounts

of sericite. The shaly beds appear to have suffered less

alteration, though they have probably gained silica and

possibly some potassium, which have formed sericite. The

potassium, however, may have been originally present in the

shale. Most of the ore contains also considerable barite amI

secondary calcite. The principal metallic minerals are pyrite,

realgar with some orpiment, and cinnabar.

The following analysis" is of sulphide ore from the Grasshopper shaft of the Golden Gate mine:

Upper vein footwall, 5 feet; upper vein, 8 feet; upper vein

porphyry, 20 feet.; shale, 8 feet. Overlying this is the massive

blue limestone.

Upper vein

Upper vein footwall

-Shale

~

~

=

= =

= =

= =

Cherty

formation

1J+~+~+~+:q+ ~++++

+ + + + +

+ + + +

FIGURE 16.-Generalized section of the ore beds in the

Mercur district. After Butler

Per cent

Silicon dioxide (SiO,) 66.42

Titanium dioxide (TiO,)_________________ .85

Aluminum sesquioxide (AhO.) 14.85

Iron SeSqUi~xdideF(Foe,)Oa)----------------} .31 Iron protoxl e (e _

Iron disulphide (FeS2) 6.60

Calcium oxide (CaO) . 35

Barium oxide (BaO) .19

Magnesium oxide (MgO) .83

Potassium oxide (K20) 2.73

Sodium oxide (Na.O)____________________ .13

Lithium oxide (LkO) Very strong trace.

Water below 110° C______________________ .53 The beds are cut by a series of fissures striking east of north

and dipping very steeply west. The ore shoots follow approximately the intersectio~ of the fissures with the ore beds. The

•• Butler, B. S., op. cit .• pp. 390, 393-395.

•• Spurr, J. E., op. ·cit., p. 424.
Per cent

VVater above 110· C 3.65

Sulphur trioxide (SO.) .31

Phosphorus pent oxide (P.O.) .04

Arsenic pentoxide (As.O.) .41

Arsenic disulphide (As.S.)_______________ 1.75

Tellurium (Te) aTrace (1)

• In the opinion of Doctor Hillebrand there was tellurium in the

sample analyzed, although on account of the small quantity obtained

he was unable to submit it to a special test, and therefore thought best

to Indicate this lack of certainty by the interrogation marh

The alterat:on of the rock and the addition of gangue minerals in the ore shoots have not been sufficient to permit a

reliable estimate of the value of the ore from its appearance.

Much good ore does not perceptibly differ from waste, and it is

necessary to sample and assay to determine its value. Realgar

or cinnabar usually indicates good ore, but their absence is no

proof of barrenness.

There is commonly a considerable difference in appearance

between the oxidized and unoxidized (base) ore. The oxidized

ore is generally light colored and more friable than the unoxidized; it lacks sulphides and contains sulphates, including

scorodite, melanterite, jarosite, and gypsum.

The following is an analysis of oxidized gold ore from the

stope of the Apex tunnel in the Mercur mine.86

Per cent

Silicon dioxide (Si02) 89. 24

Titanium dioxide (TiO.) .38

Aluminum sesquioxide (Al.O.) 2.02

Iron sesquioxide (Fe.O.) 1. 45

Iron protoxide (FeO)___________________ .62

Calcium oxide (CaO) .95

Barium oxide (BaO)___________________ .72

Magnesium oxide (MgO) .23

Potassium oxide (K.O) .47

Sodium oxide (Na.O)___________________ .08

Lithium oxide (LiO) Strong trace.

VVater below 110' C____________________ .56

VVater above 110· C____________________ 1. 16

Sulphur trioxide (SO.) .44

Phosphorus pentoxide (P.O.) .08

Arsenic pentoxide (As.O.) 1. 60

Molybdenum (Mo) (1)

Tellurium (Te) (1)

Occurrence at the gola.-Gold is never visible in either the

oxidized or un oxidized ores of the district, and the form in

which it is present has never been positively determined,

though Spurr thinks it is present as the telluride in the base

ore and as free gold, though probably in some special condition, in the oxidized ore. It has been suggested by Spurr and

others that the gold of the MereuI' district occurs in an allotropic form that will not readily amalgamate with mercury

put is attacked by chlorine and potassium cyanide. Unfortunately gold has never been found in the oxidized ores of the

MereuI' district in sufficient concentration to make a careful

chemical examination of its condition possible.

Experiments carried on for the Consolidated MereuI' Mines

Co. indicate an association of the carbon of the ore with the

gold. The following are the carbon content and the insoluble

gold in different types of ore examined:

Association of carbon and insoluble gold in Mercur ores

Oxidized ore _

Raw base (arsenic) - -_

Pyritic base _

$0. 40

.90

All but trace .

0.105

.358

. 450

The insoluble gold given is an average of a number of tests

made on raw ore after lime oxidation by agitation of 5 pounds

of ore, ground to pass 200-mesh, by air in a 2-pound cyanide

solution with 25 pounds of lime. The different ores were

boiled for a week, the carbon scum being skimmed repeatedly.

The oxidized ore gave almost no carbon, but the pyritic base

gave a large amount. An analysis of the scum gave 10.3 per

cent free carbon and $9.10 gold; after agitation in potassium

aurocyanide (KAuCY2) solution and washing it assayed $90.60

per ton.

There is considerable concentration of gold in the carbon

content of the ore, as shown by head assay after boiling: Raw

pyrite base, $3.31; after boiling, $2.27.

It is of course well known that carbon will precipitate gold

from SOlution, though no general agreement has been reached

as to the cause of such precipitation; and it has also been

shown f1t that in gold-silver cyanide solutions carbon precipitates gold more readily than silver and that little silver precipitates while gold remains in solution. Spurr has shown

that the gold is not partiCUlarly associated with the sulphides,

and the data at hand point to its association with the carbon

of the rocks.

Down the dip the character of the ore does not change notably after the SUlphide ore has been reached, but the gold content decreases in a short distance from good ore to material

too low in gold for commercial treatment.

The maximum distance from the outcrop to which ore has

been developed is about 1,500 feet. The great bulk of the ore,

however, has come from within a few hundred feet of the outcrop.

The decrease in the gold content of the ore with increasing

distance from the surface suggests enrichment by surface solutions. On the other hand, the ores at or very near the surface are as rich as at any greater depth, and in the absence of

an overlying leached zone it is not easy to find a source for

such enrichment.

The grade of the ore is low. In 1902 it averaged $5.72 per

ton, of which $1.19 was lost in the tailings. From that time

the average of the ore treated has decreased till in years just

previous to 1912 it was as low as $3.50 per ton, with 80 to 90

cents lost in tailings.

The average grade of the ore mined was, of course, dependent

on the cost of extraction and treatment, for as low-grade rock

was taken as could be profitably -handled.

Although mercury occurs in nearly all the Mercur

ores and has given its name to the camp, the Sacraf1t Cowles, R. K., Precipitation of gold and silver by carbon: Min.

and Scl. Pres8, vol. 105, p. 730, 1912.
mento is the only mine in the district from which it

has been produced in commercial quantities, and this

mine was inaccessible when the writer visited the district. Boutwell 88has described the deposit as follows:

The ore is earthy cinnabar with a siliceous gangue and

yields 6 per cent on an average imd 80 per cent in picked

samples. It occurs in bands in an altered cherty limestone

adjacent to a dike and to a fracture zone. In general the portion of this limestone which bears quicksilver constitutes a

lenticular shoot measuring about 10 feet in thickness, 50 feet

along the strike and 140 feet on the dip. This lens is coincident with the bedding of the limestone along the middle and

major portion of its dip, but at its upper edge it bends and cuts

abruptly across the bedding, while at its lower edge, on approaching the dike and fracture on its dip, it drops sharply

down across the bedding, pinching out at both its upper and

lower terminations to thin edges.

The ore deposits of the Sunshine district, about 3

miles south of Mercur, are apparently very similar in

all respects to those of Mercur, though their stratigraphic rplations are not identical. The mines are

practically inaccessible, and no new information regarding them was obtained during this survey.

'l'he shoots of the Mercur gold and gold-mercury

ores are distributed along definite fissures, and there

were a few places in which the wall rocks of the fissures were minable for some feet below the ore horizons. Fissure filling, however, was negligible, essentially all the ore being formed by impregnation or replacement of the country rock. Nevertheless these fissures were of fundamental importance in localizing

the deposits, as was shown by Spurr.89

The writer could obtain no information relative to

the extent of fissuring in the deposits at Sunshine.

At West Dip the localization of the mines along the

West Mercur fault for about 2 miles seems to indicate

a definite control of mineralization by this fault. No

adequate descriptions of the ore bodies of these mines

were obtained, and the mines are all inaccessible except for a few tens of feet along their inclined shafts.

Nevertheless, the fact that a considerable difference

exists in the stratigraphic position of the rocks along

the footwall of this fault within the mineralized area

seems to indicate that the mineralization was related

to the fault rather than to any particularly favorable

strata. Presumably, from the scant descriptions the

writer was able to obtain, the ore was, like that at

Mercur, formed by impregnation and possibly replacement of the wall rocks. The much closer dependence

of the deposits upon the fissuring along the fault here

than at Mercur is a matter of inference only.

88 Boutwell, J. M., Quick8llver: U. S. GeoI. Survey Mineral Resources,

1906, p. 494, 1907.

soSpurr, J. E., op. clt., pp. 435-437.

SILVER AND SILVER-LEAD DEPOSITS

BEDDED REPLACEMENT DEPOSITS

Bedded replacement deposits of silver and of silver

and lead occur near Mercur, in a narrow zone extending to the north end of Lion Hill, and at the Lakes

of Killarney mine, in the foothill belt between Ophir

and Dry Canyons. In all these localities the ore

minerals are localized within or beneath bodies of j asperoid which crudely parallel the stratification.

The distribution and stratigraphic relations of the

jasperoid bodies in the area between Mercur and Lion

Hill are described on pages 97-98. At both Eagle Hill

on the south and Lion Hill on the north the jasperoid

appears to be closely associated with porphyry bodies,

but between these points no such association is evident.

The silver mineralization of the jasperoid was essen~

tially coextensive with this widespread type of alteration, according to assays reported by Spurr,90 but

the areas in which it was sufficiently concentrated to

furnish minable ores are very small. A factor of

probably great importance in bringing about this

yariability was the long continuing brecciation of the

jasperoid during crystallization from the colloidal

phase (pp. 97-101), which developed constantly changing passages for the mineralizing solutions during

ore deposition. Thus some parts of the jasperoid were

closed to free circulation of ore solutions, while other

parts were especially favored. It is probable that

more remote changes in the course of circulating solutions also operated to the same end.

Whatever the control may ha.ve been, it is certain

that the important mineralization was very sporadic.

Despite the great richness of the oxidized ores of such

mines as the old Carrie Steele and Sparrowhawk, at

Mercur, and the Lion, Rockwell, Tiger, Chloride

Point, and ZelIa, on Lion Hill, nearly all the masses

of jasperoid are of so very low value as to be quite

unworkable.

The ores are characteristically silver ores, with some

gold, arsenic, antimony, lead, zinc, and manganese.

The principal gangue mineral is the silica of the jasperoid, but ore also occurs in the otherwise unaltered

limestone beneath. The ores range in tenor from very

high grade, carrying thousands of ounces to the ton,

to low-grade milling ores.

The minerals other than silica that occur in significant quantities in the jasperoid are few. Of hypogene minerals barite, calcite, sericite (muscovite),

tourmaline, chalcopyrite, stibnite, chlorite, carbon, and

probably hematite are the only conspicuous ones, and
they ape quantitatively very subordinate. Spurr 91 reports pyrite in addition, and it is probably very widespread in very fine grains. No primary silver minerals were observed either at MereuI' or on Lion Hill.

None of these jasperoid ore bodies have been worked

below the zone of oxidation, and the silver is present

as cerargyrite and in some places as argentojarositc.

It is accompanied by the oxidation products of the

other minerals in jasperoid-jarosite, malachite, azurite, and "limonite." At MereuI' scorodite also is

found, but according to Spurr this mineral is probably

derived by leaching from realgar of the overlying

" gold ledge." Butler reports arsenic in some oxidized

ore from Lion Hill. On Lion Hill plumbojarosite,

cerusite, and aurichalcite also occur. The absence of

any lead minerals accompanying the silver at MereuI'

is very remarkable, in view of the usual association of

lead and silver and especially their occurrence together

in otherwise very similar deposits on Lion Hill.

The ore bodies have in general blanket shapes, following the jasperoid or the limestone immediately beneath the silica masses, but they also have tendencies

to run parallel to fissures. This feature is very evid.ent in most of the old workings, both at MereuI' and

on Lion Hill, and is clearly seen on the mine map of

the Chloride Point area in Plate 25. These workings

are almost entirely inaccessible now, but their trends

:are generally north-south, parallel to notable fissuring

in the limestones.

Most of the ore bodies that have been worked have

been developed within a few tens of feet of the surface. ·Well-marked fissures are reported by Spurr to

extend below the jasperoid, but they are not ore bearing, although locally filled with calcite.

FOOTHILL AREA BETWEEN OPHIR AND DRY CANYONS

Small bodies of j asperoid occur in the area of the

Lakes of Killarney mine, replacing two beds of limestone close to the top of the " Great Blue" limestone,

just beneath the Manning Canyon shale. The ore occurs in jasperoid and is especially rich along fissureE

that trend nea,rly north and dip steeply east. Silver

very little gold, and traces of copper and zinc occur

in the ore. Assays as high as 600 ounces of silver to

the ton have been reported, according to James Quinn,

superintendent.

LEAD-SIL VER·ZINC-COPPER DEPOSITS

Most of the mines (other than gold) in these quadrangles have exploited bedded replacement deposits

~ither in hornfels or in limestone. These deposits are

as a rule sharply limited to certain particularly favorable limestone strata, though a few less regular

bodies transgress into the beds that normally form the

foot or hanging wall. In addition to the localization

within certain beds, nearly all the deposits are controlled by fissures. (See pI. 32.) Thus the typical

body is a mass with its longest axis along the intersection of a fissure and a bed, a secondary axis in the

plane of the bed, and its shortest dimension normal to

the bed. Some of the replacement masses reach

lengths of over 2,000 feet in the Ophir Hill Consolidated mine and over 1,600 feet in the Honerine. The

larger bodies extend along the bedding normal to the

fissures for distances exceeding 100 feet in these mines

also, but these dimensions are unusual, 30 feet being

a more ordinary width. The greatest thickness known

is 40 feet, in the" Big vein" of the Ophir Hill Consolidated mine, but 6 to 10 feet is much more common.

Variations in the size of the ore bodies along the

central fissures are usually gradual, but away from

the fissures the ore bodies are far less regular. In

some bodies the replacement has been complete within

the favorable limestone up to a nearly straight side

wall; elsewhere the mineralization became sporadic

away from the fissure, so that the ore bodies fray out

at the edges, especially in the hornfels. Most of the

ore bodies fray out along their pitch length as well,

but the changes in this direction are generally far

more gradual than in the others.

The most abundant hypogene sulphide minerals in

the bedded replacement bodies are galena, sphalerite,

chalcopyrite, microscopic argentite, tennantite, pyrite, and pyrrhotite, of which the tennantite and

pyrrhotite are confined, in the writer's experience, to

the Ophir Hill Consolidated mine. Cerusite, plumbojarosite, anglesite, jarosite, "limonite," aurichalcite,

smithsonite, calamine, hydrozincite, malachite, azurite,

pyrolite, psilomelane, and wad occur as oxidation

minerals, and probably cerargyrite also, although none

was found associated with these deposits during this

survey.

So far as could be determined, there was very little

migration of the metals during the oxidation of the

sulphide ores. In view of the high calcite content of

the wall rocks this slight migration is all that would

be expected. It is probable that near the surface impoverishment in copper and zinc of all the mixed sulphide bodies with concomitant enrichment in lead and

silver was a characteristic feature, but the surficial

oxidized ores hava long ago been mined and are not

available for study.

The tenor of these ores is in general low, but this

is compensated by the ,persistence of the shoots. The

oxidized ores mined in the early days were commonly

of very high grade, running 50 to 60 per cent of lead

and from 20 to 90 ounces of silver to the ton in the

Rush Valley (Stockton) mines, and occasionally shoots
~-------------- -

of sulphide ores are still found that approach this

grade. More usual ore from Stockton runs 6 to 20

per cent of lead, 2 to 12 per cent of zinc, and 2 to 8

ounces of silver and 20 to 60 cents in gold to the ton.

The smaller ore bodies in the Buffalo tunnel on Lion

Hill run 40 to 50 per cent of lead with about 1 ounce

of silver to 1 per cent of lead, and occasional carload

lots carry $3.50 to the ton in gold. The great ore

bodies of the Ophir Hill Consolidated mine averaged,

over a period of years, about 6 per cent of lead, 5.5

ounces of silver to the ton, 4 per cent of zinc, and 1.3

per cent of copper, with negligible gold.

IRREGULAR REPLACEMENT DEPOSITS

In addition to the regular replacement deposits, each

of which is essentially confined to a single limestone

bed, there are a few deposits, of which the old Chicago

and Hidden Treasure mines are the chief examples,

that have a pipelike form and crosscut the bedding.

These deposits are in the upper part of the Madison

limestone, beneath the shale and phosphate beds that

form the base of the Deseret formation. Instead of

being limited to a small part of the limestone, however,

the ore bodies are pipelike masses, controJled apparently by openings along north-south fissures and extending through a stratigraphic interval of 200 feet.

The Hidden Treasure ore was found chiefly within

75 to 100 feet of the shale, and at some places the

stopes were that high and reached a maximum width of

50 feet, the ore in such places being governed by a

group of fissures. The ore body dropped lower in the

strata as it was followed north. In the Sacramento indine the ore body is at least 300 feet stratigraphically

beneath the shale that forms the back of the stopes

near the surface.

The Chicago shoots were entirely pipelike, apparently not being controlled in the least by the bedding.

On the outcrop the shoots were on the same fissures as

the Hidden Treasure and about 200 feet lower stratigraphically. Toward the north, however, they rose

and finally joined the Hidden Treasure shoots. These

Chicago ore bodies were smaller, being on an average

only 2 or 3 feet in diameter. Similar pipelike masses

()ccurred in the Kearsarge mine.

In the Eureka-Ophir mine, just north of the Hidden

Treasure, the ore body, according to Mr. D. W. Lynch,

was a very irregular replacement deposit occurring

along generally north-south fissures in a brecciatec

mass of porphyry and limestone above the shale at the

base of the Deseret limestone. The mine was almost

wholly inaccessible at the time of this survey, so that

the details of form and relations of the deposit could

not be ascertained.

The mineralogy of these deposits is essentially the

.sameas that of the bedded replacement deposits. The

principal difference is that these deposits, through the

accident of their topographic position, are almost entirely oxidized, although sulphides are found in small

amount near the surface and increase in quantity with

depth. .

In the Hidden Treasure mine there seems to have

been some migration of the zinc and copper oxidation

products into the walls of the sulphide ore bodies, but,

while leading to the separation of these metals into

sheaths around the remaining lead carbonates, the migration appears to have been very slight. The Hidden Treasure oxidized ore runs about 20 per cent of

lead (maximum 40 per cent), 18 ounces of silver to

the ton, and 4 to 6 per cent of zinc. The copper carbonate ores run as high as 22 per cent of copper. The

zinc carbonate ores run about 40 p~r cent of zinc, perhaps 1 per cent of copper, and only 2 ounces of silver

to the ton. The sulphide ores run about 30 per cent of

zinc, 14 per cent of lead, and 8 to 10 ounces of silver

to the ton. The gold tenor rarely exceeds 50 cents to

the ton.

The ores occurring as clear-cut fissure fillings are

of small value, although they are present in many

areas. Replacement veins are richer, and some very

high grade ores have been recovered from them.

These deposits are in the form of tabular replacement

masses parallel to and including the fissures. Examples are found in the Jim Fisk, Salvation-Hercules,

Katherine, Mono, Cliff, and Kearsarge mines. Although some of these ore bodies were very rich they

were all small, rarely exceeding a foot or two in width,

a few tens of feet in height, and 300 or 400 feet in

length. Similar deposits have been mined in the

Honerine mine.

The mineralogy of these deposits is very similar to

that of the bedded ores, except that as a rule these

deposits carry greater quantities of gold.

The Consolidated Mercur mines were located at

Mercur, the principal workings on the south side of

Mercur Canyon but other workings on the north side.

The company owned about 944 acres of mining claims,

of which about 400 acres was in the principal mineralized belt of the camp. The mines, when active, were

served by the Salt Lake & Mercur Railroad, which connected by way of Manning Canyon with the Los Angeles & Salt Lake Railroad at Fairfield Junction. The

railrQad was dismantled in 1914.
Developl1U3ntsand production.- The mines of the

Mercur area were all caved and inaccessible at the time

of this survey in 1926, having been abandoned in 1913.

No accurate maps of the developments of the property were available, but it is known that the workings

were very extensive and ran to many thousands of feet.

The total output of the Consolidated Mercur Mines

Co. and its predecessors, the Delamar Mercur Co. and

the Mercur Gold Mining & Milling Co., was 4,336,621

tons of ore, yielding about $16,500,000 in gold. Dividends amounted to $3,445,312.

Geology.-The Consolidated Mercur mines are all

in the " Great Blue" limestone below the Long Trail

shale member. The ore was the result of replacement and impregnation of limestone beds, associated

with the jasperoid type of alteration. Six beds wero

locally ore bearing, but the principal output was obtained from the upper three of these-the "Mercur

vein," the "Middle Streak," and the "Upper vein."

The beds dip 10°-30° E., averaging perhaps 25° in the

mines. They strike a few degrees west of north as a

rule, though there are some "bedding rolls." They

form a part of the eastern limb of the Ophir anticline.

Owing to the impossibility of access to the mines,

the writer can add no detailed mine description to the

discussion of the mineralization at Mercur quoted from

Butler on page 132.

ThEl Geyser-Marion mine (Franklin lease) is just

north of the Mercur town site. It is one of the oldest

mines in the district. The Marion mill was the first

in tne district, operating on silver ores in 1872~73,

1880, and 1889. In 1893 it was changed to a cyanide

plant equipped to treat 50 tons of gold ore a day. The

adjoining Geyser mine was combined with the Marion

in 1897, but the property did not prosper and was sold

at sheriff's sale shortly after 1900. It was later operated as the Franklin lease up to 1913 but was not a

success. The total production of gold was probably

about $500,000.

Like the other mines at Mercur,the Geyser-Marion

was caved and inaccessible at the time of this survey

in 1926, so that no new information was obtained regarding it. No map of the workings was obtainable,

but they were rather extensive. The mine is known

to be in the same stratigraphic horizons as the ConsoJidated Mercur mines, and its ore was also very like

that of the Consolidated Mercur.

The Sacramento mine is about three-quarters of a

mile southwest of Mercul', in the gulch draining the

north slope of Sunrise Hill. The mine began commercial operations in 1895. It operated for about 12

years, during which about $1,500,000 in gold and over

3,000 flasks of mercury, were produced. It was the

only mine of the district from which mercury was

obtained commercially. The workings are inaccessible, but the accompanying map (pI. 26), kindly supplied by former officials of the mine, shows that they

were rather exten~ive. About 600,000 tons of ore was

extracted. ._

The mine i$ ~nthe lower part of the " Great Blue"

limestone, at the same stratigraphic horizons as the

Consolidated Mercur mines. The beds dip about 30°

E., on the east limb of the Ophir anticline. The

porphyry intrusion of Sunrise Hill cuts through the

western part of the mine; The ore is reported to have

resembled that of the Consolidated Mercur mines but

carried a considerably greater proportion of mercury,

some assays running 8 per cent.

SUNSHINE AREA

OVERLAND

"The Overland mine is about half a mile northeast of

the Sunshine, on the east side of Overland Gulch. It

was operated at intervals from 1898 to 1905, in the last

years under a receiver. The production is estimated

at $219,646, from 156,000 tons of ore.

The mine is developed on the upper levels by an inclined shaft and on the lower levels by a vertical

shaft which cut the ore bed at 1,600 feet on the dip.

The mine is in the "Great Blue" limestone beneath

the Long Trail shale member, on the east flank of the

Ophir anticline, where the dip is about 35°-40° E.

The workings were inaccessible in 1926, and no description of them can be given. The ore is described

as practically identical with that at Merour.

The Sunshine mine is just south of the town of Sunshine, a little more than 3 miles south of Mercur. It

operated from December, 1895, to October, 1896, for a

short time in 1898-99, in 1902, and in 1909-10, when it

was closed, the ore supply being considered exhausted.

The total production is believed to have been about

$221,000 in gold.

The mine is just below the Long Trail shale member of the" Great Blue" limestone and was developed

by an incline trending N. 75° E. and having a slope

of 32°, with the bedding, which dips east, on the east

limb of the Ophir anticline. The mine was. badly

caved at the time of this survey, in 1926, and but little

of it was accessible. The ore appears to have occurred

at two horizons, approximately 150 feet apart strati..:

graphically, each immediately beneath a carbonaceous

shale bed. Some fissures trending N. 41>°W. were followed by drifts. Presumably the ore was associated

with these fissures, but this is not known to be true.
~._~~-~~---

I . I~

I N I

--- -+- j

I ------ -.--,

I

I

I

i"""'."".

'~

.~.

--------'-----------~--~---_ ..-

EXPLANATION

Feet

-----

----- Level No.1 east 1085

West drift No.1 1050

5mith's level IOt.9

0, +_.,.;.:~.:;: __::. Blue level 1038

---------. ~---~----- No.4 north level 1037

_.-_ ..-

-"-"- Gus drift 1020

------ ....•........•...• --....,......•..• Main level 1000

Mill tunnel and Mill 970

level west drift

::::::::::',','.:::::::: 900 level 900

Assumed elevation 1000' for this map IS

approxirnate(y 7150'above sea level
· The ore greatly resembled that at Mercur but was

in beds lying somewhat higher in the stratigraphic

column.

WEST MERCUR OR WEST DIP AREA

DAISY (NORMA)

The Daisy mine, later renamed the Norma, is just

south of the abandoned site of West Mercur. It was

discovered shortly after the first successful gold mining in the Mercur district, and construction of a mill

was begun in 1897. It was the first mine at West

Mercur to ship cyanide precipitates, but little success

was attained and in .February, 1900, the mine was

handed over to the miners for them to earn their back

wages from it.92 In July, 1900,it went into the hands

of.a receiver. It wa::;overhauled at various times in

later years, and the company was finally reorganized

as the Norma Gold Mining Co. Operations were renewed in 1913,but the mine has been abandoned since

the complete destruction of the mill by fire in 1917.

The mine was developed by two inclined shafts,

each about 700 feet deep, with numerous drifts connecting them. The shafts were sunk along the West

Mercur fault (see fig. 9) with the" Great Blue" limestone as the footwall and Quaternary alluvium as the

hanging wall, at least for the few score feet of the

shafts that are now accessible. The mine is caved almost to the surface, and no new information regarding

its geology was obtained during this survey. The ore

is described by former employees of the mine as

strongly resembling that of Mercur. It occurred

along the West Mercur fault, presumably associated

with this fault rather than any particularly favorahle

bed.

The ore ran between $4 and $8 to the ton. It was

difficult to treat. The production of the mine was

somewhat more than $75,000.

The La Cigale mine is about a mile north of the

abandoned site of West Mercur and about 4 miles west

of Mercur. It was first developed in 1897 by three

inclined shafts along the West Mercur fault, with

levels at 100 and 260 feet below the surface. It is not

known what additional development work was done

in the two years following, but the mine was abandoned at the end of 1899. In 1926 it was so badly

caved that the workings were inaccessible. The workings have been described 93 as localized along a shear

zone, and certainly the shafts expose and follow the

West Mercur fault (see fig. 10), so that presumably

the ore was related to this major fault. The fault dips

west and as far down the incline as can be seen, about

92 Howard, L. 0., Cyanidation in the Mercur district of Utah: Salt

Lake Min. Rev., October, 1913.

9. Thompson, R. V., oral communication.

150 feet, exposes only alluvium in the hanging wall.

The long strike distance through which the fault zone

was assayed and found to be mineralized leads to the

conclusions that the fault was probably of premineral

age and that the mineralization was not confined to

certain beds as at Mercur but extended to the breccia

zone along the fault. However, the" Great Blue"

limestone, which forms the footwall of the fault, dips

essentially parallel to it, so that the localization of the

ore along the fault may possibly have been fortuitous.

and due merely to accidental coincidence with a susceptible limestone bed. The horizon in the "Great

Blue" limestone just below the fault is much higher

than that of the productive strata at Mercur, being

several hundred feet above the Long Trail shale member instead of below it.

The ore is described as essentially the same as that

of Mercur, and assay values averaging over $6 a ton

were reported by the company. In view of the success of the Mercur mines with ore of this grade, it is

probable that such assays were not truly representative of the ore as mined, for if they were the venture·

should have prospered better than it did.

LION HILL AREA

BUFFALO

The Buffalo mine is on the southeast side of Lion

Hill and has been worked through two adits near the

upper end of Long Trail Gulch. It is reached by

wagon road up Long Trail Gulch from Ophir, a distance of somewhat less than 2 miles.

Development and production.- The mine is de·

veloped through two adits about 280 feet vertically

apart, connected by means of an inclined raise and

drifts. The total workings probably exceed 6,000 feet

in length, but much of the older part of the mine is

caved and inaccessible. The principal workings dat~

from the early days of mining in the district, and as.

in most of the mines whose principal production was

made in those days, the total output can only be guessed

at. It is known to exceed $150,000 and may be very

much greater. For a number of years before the time

of this survey, the mine had been under lease to George

St. Clair.

Geology.-The Buffalo mine (see pI. 25) i~ situated

in the lower part of the "Great Blue" limestone,

below the Long Trail shale member. Two sills of

" Birdseye" porphyry are cut by the lower tunnel,

but the ore seems to bear no relation to them. The

beds in the mine have generally an even inclination,

striking N. 25° E. and dipping about 25° SE.

The ore occurs in pipes and in bedded deposits that

replace the limestone. In the upper workings the ore

shoots connected with those of the Chloride Point
mine, and large stopes were developed in connection

with the jasperoid wall rock, but on the lower levels

there is little jasperoid. The principal fissures in the

lower workings of the mine are those followed by the

McClellan and St. Clair inclines. The McClellan incline trends N. 70° E., the St. Clair S. 65° E. The

Clark incline, just west of the McClellan, extends up

from the lower or Buffalo tunnel level as a continuation of the drift from the St. Clair incline and "COnnects, on a level 200 feet higher, with the East Side

tunnel. The connection is very narrow and tortuous

and was not surveyed, so is not shown in Plate 25.

The ore followed fissures and locally extended along

the bedding for 6 or 8 feet from the fissures. A shoot

on the St. Clair fissure was 2 feet wide and 12 feet

high, of solid galena, but pinched out when followed.

On the upper levels the ore was all oxidized, but in

the lower part of the mine it is chiefly sulphide ore,

although some oxidized material is found even 011 the

lowest levels. Galena, chalcopyrite, and pyrite are the

common sulphides, in a gangue of calcite, fluorite, and

some quartz. Oxidation products are plumbojarosite,

eerusite, cerargyrite, jarosite, malachite, wad, and

" limonite."

The ore shipped in years just prior to the time of

this survey averaged between 40 and 50 per cent of

lead, with about 1 ounce of silver to 1 per cent of lead.

Some carloads assayed as much as $3.50 a ton in gold,

but in others the gold was insignificant. A few carloads carried paying quantities of copper, but there

were no true copper ores.

The Chloride Point mine is on the southeast flank of

Silveropolis Hill at an elevation of about 8,150 feet.

The mine is reached by wagon road from Ophir by

way of Long Trail Gulch, a distance of about 2 miles.

The road is very steep and tortuous.

Developments and plf'odwotion.-The mine is developed by means of two subparallel tunnels, following

the ore. (See pI. 25.) The ore bodies are confined to

shallow depths, and no deep winzes or inclines were

necessary. The total development work probably does

not exceed 5,000 feet.

The mine was one of the first discovered on Lion

Hill, being located in August, 1870. The production

of the mine was nearly all made in the early days,

when bonanza lead-silver ores were found. In recent

years lessees have produced a considerable quantity of

ore but probably not approaching the output of the

early miners. Under the circumstances an estimate of

the total production is a mere guess, but certainly it

exceeds $200,000 and may exceed $1,000,000.

Geology.-The mine is just east of the axis of the

Ophir anticline, in the lower beds of the" Great Blue"

limestone, a short distance beneath the Long Trail

shale member. The limestone beds strike slightly

west of north and dip 25°-35° E. They are little disturbed by faults in the neighborhood of the Chloride

Point mine but are cut by north-south fissures, which

doubtless governed the localization of the ore to a

great extent. Two fissures about 20 feet apart have

been followed for over 600 feet north from the portal,

and very rich ore was found along them. Another

fissure about 250 feet west of these was picked up and

. followed along its strike, about N. 10° E., for over 600

feet. Crosscuts about 350 feet northwest of the Gladstone shaft intersected the Gladstone fissure, which

strikes N. 40° E. and dips about 80° NW. An incline

175 feet north of the Gladstone shaft follows one of

the intermediate fissures down to the north and connects with the workings at the Buffalo mine, about 80

feet lower than the main tunnel of the Chloride Point

mine.

Ore bodies.-The ore bodies of the mine were chiefly

blanket and pipe deposits along the intersection of the

fissures and just below or in the lower part of the

jasperoid bodies. Presumably the ore was originally

deposited in the jasperoid and owes its transfer to the

beds immediately below to slight migration during

oxidation. Some of the stopes were as much as 80

feet wide, but more commonly they were 10 or 15 feet

wide and 3 to 8 feet high.

The ore is practically all oxidized and consists of

cerusite, plumbojarosite, cerargyrite, malachite, jarosite, and "limonite." Silica, barite, and calcite are

common gangue minerals. Subordinate minerals in

this mine include aurichalcite, stibnite, stibiconite, and

argentoj arosite.

The tenor of the ores in recent years has averaged

about 70 ounces of silver and $2 in gold to the ton,

8 per cent of lead, and a little copper. This is much

lower than the tenor of the old bonanza ore, in which

assays of hundreds of ounces of silver to the ton were

common.

EAST SIDE, JoIONARCH, IRON, EJoIPIRE, NORTHERN LIGHT, AND

WOODRUFF

The East Side, Monarch, Iron, Empire, Northern

Light, and Woodruff mines, all of which were located

and worked intensively in the early days of the district, are on the northeast and east sides of Lion Hill,

near the crest of the hill. They are reached by wagon

road from Ophir by way of Long Trail Gulch. Several thousand feet of development work was done,

chiefly within 100 feet of the surface. The production

was practically all made in the early days of the camp

and ran to many thousands of dollars, but the total

is unknown.

Geology.-The mines are all in the lower part of the

"Great Blue" limestone, below the Long Trail shale

member. The strata here are just east of the axis of
the Ophir anticline and dip at low angles to the east,

with a generally north-south strike. The ore deposits,

like those of the Chloride Point mine, occur in or

closely associated with jasperoid. In part but not all

of the workings the jasperoid lies immediately beneath a sill of "Birdseye" porphyry. Most of the

old workings are now inaccessible, but the ore is known

to h.ave followed very irregular, generally northeasterly fissures in the jasperoid. It was chiefly in the

form of pipes, but in the East Side tunnel and the

Monarch group some large bedded replacement bodies

were found. The workings are shown in Plate 25.

The ore was practically entirely oxidized and, if

specimens examined on the old dumps are typical, consisted chiefly of cerusite, plumbojarosite, jarosite, cerargyrite, and wad. Butler 94 reports a yellow leadarsenic mineral of undetermined composition from

this group, but it was not noted during the present

survey. A beautiful specimen of cerargyrite from the

East Side tunnel was given to the writer by Mr.

George St. Clair as typical of a large mass there

found. It was of such purity that it could be sawed

with an ordinary saw. According to Mr. St. Clair,

assays as high as 6,000 ounces of silver and 3 ounces

of gold to the ton were reported on the richest ore

and large masses ran as much as 300 ounces of silver

and $6 to $8 in gold to the ton. Assays showing as

much as 35 per cent of lead were common.

At the time of this survey the Iron tunnel was under lease to James, William, and Patrick Kelly, who

reported that the hand-picked ore they were producing in small lots ran from 60 to 100 ounces of silver

and $1.50 to $3 in gold to the ton and from 14 to 20

per cent of lead.

The Lion, ZelIa, Douglas, and adjacent mines are

on the western and northern slopes of Lion Hill near

the crest. They were vigorously worked in the early

days of mining in the district but had been practically

inactive for many years prior to the time of this survey, 1926 and 1927. The production of the group

probably exceeded $1,000,000.

All these mines are in the lower part of the " Great

Blue" limestone, where it dips gently westward on

the western flank of the Ophir anticline. The ores are

intimately associated with jasperoid. The workings

of all these mines are now caved and inaccessible,

and little can be added to the following description

by Huntley: 95

'l'he ZelIa group comprises the ZelIa, Mountain Tiger, Silver Chief, and Rockwell, patented, and several others unpatented. It is situated on the western side and near the summit

••Butler, B. S., The ore deposits of Utah: U. S. GeoI. Survey Prof.

Paper 111, p. 381, 1920.

•• Huntley, D. B., Tenth Census U. S., vol. 13, p. 451, 1885.

of Lion Hill. * * * The ore outcropped in two places, the

croppings assaying $200 per ton. Three large bodies and

several smaller ones were found about 20 feet below the surface. The ore is a soft yellow siliceous chloride assaying

several hundred dollars per ton. * * * The mines are

opened by several shafts and tunnels, in all over 6,500 feet.

The actual working development on the stratum containing ore

does not, however, extend over 125 feet vertically and 800 feet

horizontally. * * * The total product of this group was

estimated at $750,000.

The Douglas mine * * * is situated near the western

summit of Lion Hill. * * * It is near the Monarch group,

which it greatly resembles in gangue and ore. The country

rock is stratified limestone. Whether the quartzite gouge of

the Monarch is an inter stratified quartzite bed or a local mass

of quartzite can not be determined from the developments.

[This "quartzite" is undoubtedly jasperoid, derived from

limestone by silicification during ore deposition.] This stratum is 30 feet thick and is known to extend 250 by 350 feet.

Two bodies have been found of about the same size 50 feet

apart. One is 150 feet long, from 2 to 12 feet thick, and from

4 to 15 feet wide. The mine * * * is worked over 150

feet from the surface and has about 600 feet of cuttings. The

total product is said to be Oatleast 1,000 tons of 100-ounce ore.

The Lion mine is on the southwest slopes of Lion

Hill alonD'a northward-trending fissure dipping west.

, b •

The ore is associated with jasperoid. Huntley est.]·

mated the production as $120,000.

A fault trending N. 45° W. was observed at the

ZelIa mine and considerable work had been done

along the c~ntact of a lamprophyre dike, trending due

north.

All these mines were dry and worked oxidized ores,

presumably identical with those of the Chloride Point

mine. The gangue was siliceous and sericitic, with

barite and calcite. The ore was composed of cerargyrite, plumbojarosite, cerusite, and jarosite.

The Three Metals tunnel, owned by the Ophir Metal

Co., is in Long Trail Gulch, at an altitude of about

7,300 feet. It is reached by wagon road from Ophir,

about a mile and a quarter away. The tunnel extends

under Lion Hill a distance of nearly 2,000 feet. A

:few score tons of lead-silver ore was extracted, and

the total production was only a few thousand dollars.

The ore ran about $3 in gold and 90 ounces of silver to

the ton, 11 per cent of lead, and a little copper.

The geology of the mine is simple, the tunnel being

a crosscut, penetrating the lower part of the "Great

Blue" limestone and the upper part of the Humbug

formation. The beds strike generally N. 15°_50° W.

and dip 12°-40° E., flattening toward the face of the

tunnel as they approach the axis of the Ophir anticline.

The fissures intersected in the tunnel all strike northeast. Most o:f th"m dip west, but one sheeted zone

along which the tunnel is driven for about 300 feet

near the portal, has a southward dip. (See fig. 17.)

The attempt was made in this tunnel to prospect be-
neath the formerly productive "chloride" mines of

Lion Hill, and for this reason, presumably, the course

of the tunnel as a whole is about S. 40° W. The face

of the tunnel is probably about vertically beneath the

old Monarch workings.

FOOTHILL AREA

LAKES OF KILLARNEY

The Lakes of Killarney mine is in the western foothills of the Oquirrh Mountains, about a quarter of a

Blue" limestone just below the Manning Canyon shale.

There is a 3-foot shale overlying the upper bed and a

somewhat thinner one abovethe lower. The old stopes

are cut off on the west by a fault trending N. 30° W.

and dipping 55° SW., parallel to the great Lakes of

Killarney fault, 100 yards or so to the east.

The ore occurs in jasperoid breccia which replaces

these limestone beds along fissures trending N. 10°_

15° W., N. 20° W., and N. 50° W., all with steep east

dips. Most of the workings are in the upper of th~

mile south of the mouth of Dry Canyon. It is reached

by wagon road from the loading station at the Bates

ranch, on Ophir Creek, a distance of about Ph miles.

The mine was worked in the early days and is locally

credited with a production approaching $250,000,but

nothing is known to confirm or refute this report.

'WIthin the 20 years preceding the present survey only

a few tons of silver ore were mined. Active prospecting was going forward at the time of this survey in 1927.

The principal developments of the mine are in two

beds of limestone about 40 feet apart in the "Great

two beds. Considerable sericite and calcite occur ill

the jasperoid, but no ore minerals other than a littlemalachite were discernible.

According to James Quinn, superintendent, assays

as high as 600 ounces of silver to the ton have been

reported on the ore, but this is of course much higher

than the mine run. The small amount of ore shipped

in recent years averages just under 50 ounces of silver

to the ton, with a little gold. Traces of lead and

copper also occur but in far less than commercial

limits.
OPHIR HILL AREA

ADMIRAL DEWEY

The Admiral Dewey prospect is in Hartmann Gulch

about half a mile north of the town of Ophir. The

only developments at the property are a tunnel a few

score feet long, an incline, and some surface trenches.

The tunnel follows the contact of a 4-foot lamprophyre

dike, which cuts the Bowman limestone a short distance above the base. An incline a short distance up

the hill from the tunnel follows the intersection of a

fissure and the bedding for about 150 feet. The fissure trends N. 15° E. and dips 70° NW. It contains

a narrow vein of galena, with oxidation minerals including "limonite," jarosite, gypsum, and cerusite.

A few sacks of high-grade ore have been produced

from this prospect, but no development into a mine

has been attempted.

Location.- The Cliff mine is on the north slope of

Ophir Canyon about a mile northwest of Ophir and

about 1,000 feet lower than the Dry Canyon divide.

The mine is reached by a wagon road from Ophir.

An aerial tramway, built about 1905, connects the

mine with the railroad at Ophir. Before 1912 the

ore was hauled from the foot of this tramway to St.

.John Station by tractor.

Develop11umt and production.-The mine· was

worked in the early days of the district but was dormant or only moderately active for a long period till

1905,when it was again actively worked for about 15

years. Since the "Vorld War there has been little

production from the Cliff mine, but statistics of production since 1918 are combined with those of the

Hidden Treasure mine, which is under the same ownership, so that definite information is not available.

This property was for several years the largest producer in the district. The total production is unknown but is probably between $2,000,000and $3)000,-

000. The property consists of several claims, of which

the Buckhorn, Eighth of January, Trafalgar, Tomahawk, and Corning contain most of the workings.

The mine is developed by three tunnels along the

Cliff fault, at altitudes of about 7,840,8,060,and 8,260

feet. These tunnels are respectively 2,100, 1,450, and

800 feet long. From all of them main drifts have been

run westward in the footwall of the Cliff fault-on the

lower level about 700 feet, on the middle level about

1,600 feet, and on the upper level about 1,400 feet.

With the minor drifts and crosscuts and the numerous

winzes and raises, both in the Cliff fault and in the

Madison limestone, the total openings of the mine

amount to at least 12,000feet. The mine is connected

on the middle level with the Hidden Treasure mine

and has been worked as a unit with that mine since

1918. At the time of the survey in 1926 and 1927the

property was under lease, as it had been for many

years, to D. W. Lynch, of Salt Lake City.

Geology.-The workings of the Cliff mine are in the

Lynch dolomite, the Jefferson (?) dolomite, and the

lower beds of the Madison limestone, as well as in the

Cliff fault between walls of these formations. (See

pI. 27.) The lower adits penetrate the Lynch dolomite

in the footwall of the Cliff fault. Practically all the

replacement ore was confined to the Madison limestone, although locally the ore made down into the

upper part of the Jefferson (?) dolomite. Most of the

production within the Madison limestone has been derived from two beds, one at the base, the other about

40 feet higher. The lower part of the Madison limestone, including these beds, is locally called "Buckhorn" limestone. It is possible that some of the ore

which was supposed to occur in the upper part of the

Jefferson (?) dolomite (locally called the "Gray

lime") was actually in the Madison, occupying sink

holes in the upper surface of the Jefferson (?) dolomite, such as are illustrated in Figure 4.

The structure of the mine is relatively simple. The

workings are practically confined to the footwall

(northwest) side of the Cliff fault, which has here a

total displacement of about 400 feet. Exact measurement is very difficult underground, owing to the multiple slicing along the fault, so that it is rarely certain

that all branches of the fault have been penetrated

in a given crosscut of the fault. The beds on both sides

of the fault strike N. 50°-85° W. and dip about

20°-50° NE. The beds form a part of the eastern limb

of the Ophir anticline.

The Cliff fault trends about N. 35°-40° E. and dips

600

-65°SE. It has been mined for 550 feet below the

lowest level of the mine in some places and practically

to the surface elsewhere, through a vertical distance

of fully 1,100 feet. On the middle tunnel level the

drift extending along the contact between Jefferson

( ?) dolomite and Madison limestone passes into the

dolomite for several hundred feet (see pI. 27) and then

penetrates a breccia mass consisting of mixed rhyolite

porphyry fragments and dolomite and limestone.

This breccia forms the hanging wall of a fault with

probable downthrow of about 60 feet on the wests

which strikes N. 45° E. and dips 60° W. at the drift

but curves to a nearly east-west strike within about

300 feet to the northeast. This contact as well as

the overlying porphyry-limestone breccia has been

mineralized, and stopes of rather large dimensions

have been opened above and below this level. A winze

has been sunk on the fault about 80 feet south of the

drift. The hanging wall of this porphyry breccia

has been explo~ed in the Hidden Treasure workings

but without success. The same prophyry is cut by the
drift from the upper adit of the mine. The drift

penetrates the porphyry, which is about 75 feet thick,

and a crosscut is carried south into the dolomite footwall for about 100 feet.

Ore bodies.-The principal ore bodies of the mine

were replacement masses along fissures in the Madison

limestone and replacement and fissure ores in the Cliff

fault. The ores in the limestone footwall of the Cliff

fault were localized along rather inconspicuous fissures, of which the four largest strike N. 40°-55° E.

and most dip very steeply east. On the upper tunnel

level these four fissures are cut by the drift along the

basal Madison beds at 50, 250, 400, and 650 feet west

of the Cliff fault. The fissures are rather irregular,

and minor fissures run out from them in many directions. The ore bodies were not very large. Some exceeded 100 feet in strike length along the bedding, but

few were more than 1 or 2 feet thick. More common

dimensions were 12 feet wide by 6 feet high. Their

continuation in depth was irregular, only two shoots

continuing to the lower tunnel level. Several stopes

were about 60 to 100 feet long. The limestone walls

of the stopes are very vuggy and open and show strong

oxidation stains even on the lower tunnel level.

The ore bodies in the Cliff fault'zone were largely

tabular deposits replacing dolomite and limestone

blocks between the several branches of the fault, although there was undoubtedly some fissure filling also.

On the level of the middle tunnel the Cliff fault is

composed, near the portal, of three principal branches

forming a fault zone about 60 feet wide, which nar·

rows as the three branches unite, about 1,000 feet in.

On the lower level the zone is about 40 feet wide, and

on the upper level there are several branches which

unite and separate as they are followed in strike.

Similar branching and reunion of the faults occur in

dip as well. The ore is localized along these faults

and replaces the sliced rock between them. Apparently the dolomite and limestone were equally susceptible to this replacement, as some large ore bodies

occur well below any limestone slices. Some of the

ore bodies were 60 to 80 feet long and 12 feet wide.

The largest stopes appear to have been in the faults

to the east of the principal (footwall) fault of the

,Cliff zone. Large masses of carbonate occur in these

faults, some lining caves. Despite the free circulation

of water along these fissures much of the fault zone

ore was unoxidized, even on the upper level.

The ores.-The bedded replacement ores of the Cliff

mine were largely oxidized ores of lead and silver,

carrying paying quantities of copper and gold as

subordinate constituents. Oxidation occurred to the

deepest levels explored, but sulphide residua were

common almost to the surface. The principal hypogene minerals were pyrite, galena, sphalerite, and

chalcopyrite. On oxidation, cerusite, plumbojarosite,

smithsonite, malachite, aurichalcite, and azurite were

the common products, with jarosite and various oxides

of iron. Only a small quantity of oxidized zinc ore

was mined from the Cliff property, although such ores

were conspicuous in the Hidden Treasure mine. The

only conspicuous gangue mineral is manganiferous

calcite, but very small quantities of silicates and

quartz also occur.

The ore from the Cliff fault zone was much less

thoroughly oxidized than the bedded replacement ore.

It was composed of the same hypogene minerals but

was accompanied by considerable silicate gangue,

chiefly diopside, andradite, epidote, and tremolite. It

is quite evident that the Cliff fault was one of the

principal channels through which the mineralizing

solutions gained access to the rocks.

The tenor of the ore was such that it was all

shipped direct to the smelter without milling. The

average tenor for several years before the World War

was lead about 13 to 15 per cent, copper a little less

than 1 per cent, silver about 8 ounces to the ton, and

gold about 25 cents to the ton. A little zinc ore was

also shipped about this time, but its tenor is unknown.

Looation and acCX3ssibility.-The Hidden Treasure,

Chicago, and Sacramento are three of the most famous mines of the early days of Utah mining. They

are on the Ophir side of the divide, between Dry and

Ophir Canyons, just below the crest. In the early

days they were worked through inclines from the outcrop on the divide and were reached by a circuitous

road from Dry Canyon, but since the driving of the

Sovereign adit tunnel, from the bed of Dry Canyon,

which intersects the workings of all three at depth,

they have been worked through this adit. The ore

from the Cliff mine is also shipped through the

Sovereign tunnel. The mine is reached by wagon

road up Dry Canyon from the Bates ranch. The ore

is hauled by team to a siding at the Bates ranch, a

distance of 3% miles.

In the early days the mines were independent properties, but after the rich bonanzas had been extracted

they were combined into one holding, which since

1918has included the Cliff mine. All are now worked

as a unit. Living quarters for the miners are maintained at the Cliff portal. The principal claims included in the property are the Hidden Treasure

amended, Columbia, Chicago No.2, Sacramento, Red

Pine, Anna, Summit, and Hercules. For many years

the property has been under lease to D. W. Lynch.

formerly with associates. .

Development and production.-The mines were developed in the early days by sinking inclines either in
the ore shoots or closely alongside them. These inclines are now largely caved near the surface, but at

least five are known to have extended for fully 1,800

feet in dip length. The Granite tunnel was driven

from the hillside south of Dry Canyon at an altitud~

about 220 feet below the portal of the old Hidden

Treasure incline, and from it an incline was sunk between the two main ore shoots. This is known as the

Hidden Treasure main incline and was the chief haulageway of the mine for many years. The Sovereign

tunnel, 450 feet lower than the Granite tunnel, was

connected with all the workings and has since been

the main working entry. .Including all the tunnels

and inclines, the development work in the mines probably exceeds 15,000 feet. (See pI. 27.)

The mines have been among the largest producers

in the district. In the early days they were wholly

lead-silver mines and found very rich bonanza ore at

the surface. Long after this easily accessible ore was

exhausted, the presence of oxidized zinc ores occurring

as sheaths about the old stopes was recognized, and the

mine yielded largely in zinc. The production data for

the early days are very uncertain, but it is probably

safe to attribute to these mines a total production of

over $3,000,000 in lead, silver, zinc, copper, and gold.

Geology.- The Chicago, Hidden Treasure, and Sacramento mines are all in the Madison limestone. The

Hidden Treasure ore shoots were, in general, in the

upper beds of the Madison, but the ore only exceptionally occurred in the very topmost beds, just beneath

the basal phosphatic shale member of the Deseret

limestone. A foot or two of barren limestone intervened along most of the length of the ore bodies. The

Chicago and Sacramento ore bodies showed practically no tendency to be limited to a single stratigraphic

horizon but passed up and down through the section

as they were follow,ed,although both were in the Madison limestone throughout.

These mines are close to the axis of the Ophir anticline, where the strata strike N. 70°-80° E. and dil=

30°-35° N. The attitude of the beds is surprisingly

regular, being broken only by very insignificant faults

and slightly exaggerated dips.

• Only three noteworthy faults were observed in the

workings. A steeply northward-dipping fault trending N. 60° E. along the tenth level of the Hidden

Treasure mine has a displacement of 15 or 20 feet

down on the north. A fault striking N. 40° E. and

dipping steeply southeast cuts the Hidden Treasure

incline about 80 feet south of the Sovereign drift and

is also a normal fault of about 30 feet displacement.

A fault striking N. 15° W. and dipping 75° SW. just

east of the porphyry breccia mass which separates the

Hidden Treasure group from the Cliff workings on

the Sovereign level probably has no great displacement, as no notable offset is to be seen on the surface,

and the relations of the Madison limestone and Jefferson ( ~) dolomite on the Sovereign level hardly permit appreciable displacement.

The structural features that have had an important

effect on the ore deposit:;,are the fissures. These all

stand essentially vertical and although irregular in

detail, form rather well-marked zones which trend

generally within 5° or 10° of north. They show little or no displacement. The ore bodies of the mines

are all localized along these fissures.

Ore botlies.-The upper workings of the mines are

aU caved and inaccessible. According to Mr. Lynch,

who has long been familiar with the mines, there were

five principal ore shoots-the Hidden Treasure east

side and west side shoots, the Chicago east side and

west side stopes, and the Sacramento.

The ore bodies forming the Hidden Treasure shoots

cropped out together, just beneath the basal shale of

the Deseret limestone. Almost immediately below the

surface the ore shoot split in two parts, which diverged northward until they were about 300 feet

apart. These are known as the east side and west

side stopes. The ore made along these fissure systems, chiefly within less than 100 feet stratigraphically

below the basal phosphatic shale of the Deseret limestone. The ore bodies were in some places fully 100

feet high and as much as 50 feet wide. Where they

were as wide as this they were generally due to several subparallel fissures rather than to a single one.

The ore bodies formed pipes rather than blanket replacement deposits, not being confined to a single bed

or even a single group of beds. Toward the north the

shoots dropped stratigraphically lower, though nowhere as far in the Hidden Treasure mine as in the

Sacramento.

The fissures are in large part enlarged into open

caves as much as 100 feet high, lined with crystalline

calcite. The west side stopes were not so large as the

east side. Where the west side stopes trend easterly,

about halfway between the Granite tunnel and the

Sovereign tunnel, a number of short branching fissures pass out into the northwest wall of the ore body

but pinch out in a short distance.

The Chicago, ore was entirely in pipes, following

fissures without regard to any particular bed. At the

outcrop the main ore shoot was about 200 feet stratigraphically below the Hidden Treasure, on the same

fissures. Like the Hidden Treasure this shoot split

down the dip into an east branch and a west branch, of

which the east one was the larger, as in the Hidden

Treasure. These branches at first pitched into lower

beds but farther north were deflected upward and

finally joined the Hidden Treasure shoots. The Chicago ore shoots were as much as 10 to 15 feet high
and 8 to 10 feet wide. Locally there were two or more

pipelike masses, one above another on the same fissure.

Such shoots branched and rejoined as they followed

the fissures but showed no regard for any stratigraphic

horizon.

The Sacramento shoot cropped out about 600 feet

<:astof the Hidden Treasure, close to the contact of a

prominent rhyoJite porphyry dike and the upper beds

of the Madison limestone. The ore body was pipelike

in shape and followed fissures that trend slightly west

of north and do not appear to have any regular relation

to the rhyolite intrusion. When followed northward

the ore shoot was found to descend stratigraphically

until it was fully 300 feet below the top of the Madison

limestone, although at the surface it was immediately

below the basal shale of the Deseret limestone. The

Sacrilmento shoot has been followed to a depth of 400

feet below the Sovereign tunnel level, a vertical

distance of about 1,100feet.

The ores.-The dominant ore of these mines has

from the first been oxidized lead-silver ore, even to the

greatest depths attained. Pockets of unoxidized

galena and sphalerite were found almost at the surface, however, and are the chief constituents of the ore

for as much as 400 feet above the Sovereign tunnel

h'vel on the few tight fissures. At nOItime have

sulphide ores been the principal product of the mines.

The hypogene ore consisted essentially of pyrite,

galena (carrying a·rgentite), sphalerite, and chalcopyrite, the minerals varying greatly in relative quantity

from place to place. On the whole, galena was the

dominant sulphide, but locally sphalerite predominated. These minerals were deposited with a gangue

of silicates, of which wollastonite, sericite, epidote,

actinolite, adularia, diopside, and a little chlorite,

tremolite, and andradite were most abundant. Quartz

also accompanied the ore, and probably some topaz

and marialite were present as well. The chert nodules

that are so prominent in the upper part of the Madison limestone commonly show alteration to radiating

masses of wollastonite and quartz. Considerable apatite also occurs in the ore, but in view of the large

amount of accompanying collophane it is possibly due

to recrystallization of material derived from the overlying phosphatic shale bed at the base of the Deseret

limestone.

Despite the large number of silicates found in the

gangue, the limestone appears megascopically to be but

little altered and effervesces freely with dilute add.

Microscopic examination is required to showthe extent

of metamorphism it has undergone. Much residual

calcite, of course, remains, and the metamorphism has

been not nearly so intense as that in the Ophir Hill

mine, for example.

The hypogene sulphides have been oxidized, with

the production of cerusite, plumbojarosite, horn silver,

malachite, azurite, cuprite, aurichalcite, smithsonite,

hydrozincite, calamine, zinc-bearing clay, limonite, and

wad. The zinc carbonate ores have been described by

Loughlin.96 Of the oxidized minerals cerusite and

plumbojarosite were the most abundant. Ferruginous

smithsonite was the chief zinc mineral, and malachite

Rndazurite the chief copper minerals. Lead carbonate

formed the mass of the stopes. Locally this was

partly surrounded by a thin casing of malachitell;zuriteore. The lead and copper shoots were in general partly inclosed by a layer of smithsonite, chiefly

in the footwalls of the stopes. This smithsonite layer

was only exceptionally over 6 inches thick, but owing

to its high grade and the ease of its extraction from the

old lead stopes, in which at first it had not been recognized, it was very profitable.

The ore mined in the early days ran from 15 to 40

ounces of silver to the ton and 20 to 50 per cent of

lead. According to Mr. Lynch, in the period just preceding this survey, the lead carbonate ore which has

been the chief ore of the mine averaged 21 to 22 per

cent of lead, with a maximum of 40 per cent. Silver

averaged 18 or 19 ounces to the ton, zinc 4 to 6 per cent

after sorting out, and iron 22 per cent. The zinc carbonate ores ran 40 per cent of zinc on an average,

with a maximum of 44 per cent in carload lots. This

zinc ore carries an average of 1 per cent of copper and

about 2 ounces of silver to the ton. The copper carbonate ores ran about 22 per cent of copper.

The sulphides, which have been mined only in recent years, average about 30 per cent of zinc, 14 per

cent of lead, and 8 or 10 ounces of silver to the ton.

As much as 50 cents in gold to the ton may occur in

any of the ores, but it is not consistent.

The Jim Fisk mine is in Jim Fisk Gulch, a small

gulch on the north wall of Ophir Canyon, about half

a mile northeast of Ophir, at an altitude of about

7,200 feet. The site of the old Baltic miil, which

served this mine in the early days, is at the junction

of Jim Fisk Gulch and Ophir Canyon, about 600 feet.

lower than the lower tunnel of the old mine.

The mine is developed by two principal drifts, 900

and 300 feet long, with some smaller drifts and inclines and raises connecting them, both lower and

higher than the principal drifts. Mining has been

carried out through a vertical distance of over 600

feet, how extensively the writer is unable to say, because much of the mine was inaccessible at the time

••Loughlin, G. F.• Zinc carbonate and related ores at Ophir, Utah:

U. S. Geol. Survey Bull. 690, pp. 1-14, 1919.
of the survey, in 1927. A map of the workings kindly

furnished by Mr. J. Fewson Smith, of the United

States Smelting, Refining & Mining Co., is reproduced in Figure 18.

The mine was opened in the early days and was

vigorously exploited at that time. It has been operated at intervals since, chiefly by lessees; the last work

prior to this survey was done by J. F. Worthing in

1923. After the field work on this report was completed, in 1928, work was renewed on the Jim Fisk,

I nearly vertical. Just south of this fault fissure the

beds strike N. 35° W.; just north of it they strike due

north. The ore of the mine was found chiefly along

the Green Eyed Monster and three of the N.10°-30° E.

fissures-the Gem, Jim Fisk, and San Joaquin. Some

of the ore was fissure filling, but most of it had reo

placed the limestone, both above and below the basal

shale of the Deseret limestone. Stopes 6 feet high and

4 feet wide along the Jim Fisk fissure were opened on

the upper tunnel level. This fissure was mined for

but no information has been obtained as to the nature

of this development Orits results. The total output of

the mine is unknown. It is estimated locally at about

$500,000, but this is probably excessive, and $200,000

would probably be nearer the correct total.

Geology.-The workings of the Jim Fisk mine are

in the uppermost beds of the Madison limestone and

the lowest beds of the Deseret limestone. The beds

dip 45°-50° E. on the east flank of the Ophir anticline.

The general strike is about N. 35°-40° W.

The beds are cut by a number of fissures that strike

N. 10°-30° E. and dip steeply northwest and by the

Green Eyed Monster fissure, a fault fissure of slight

displacement, which strikes N. 75° E. and stands

about 250 feet. The. stopes along the Green Eyed

Monster fissure were both· above and below the shale

and are about 30 feet high where the mine was accessible. They plunge parallel to the dip of the beds.

They were mined for a width of 8 feet in places and

averaged perhaps 5 feet.

No ore samples could be obtained at the time of the

visit to the mine in 1927, but according to Mr. George

St. Clair, who was connected with the mine when it

was in operation, the ore consisted of native silver,

ruby silver, "antimonial silver," horn silver, a little

lead carbonate, and probably argentite. The ore was

oxidized, as is evident from this list of minerals. .The

ore ran as much as several hundred 'ounces of silver
to the ton and carried a little copper and lead as well

as a few cents in gold to the ton.

The Ophir Coalition group is on the north wall of

Ophir Canyon, about. half a mile north of Ophir, just

west of the workings of the Ophir Hill Consolidated

mine. The group consists of about 12 claims, of which

the Lost Boy, Teller, and Montana have thus far

proved the most productive.

The mine is developed by means of a vertical shaft

about 500 feet deep, with inclines in the limestones of

the Ophir formation. Litigation with the Ophir Hill

Consolidated Mining Co. resulted in a decision in

favor of that company, to which the more productive

part of the workings, developed through the Montana

shaft, were awarded. These workings formed the

Clark stope of the Ophir Hill. The geology of the

Montana mine is like that of the Ophir Hill Consolidated and requires no discussion, as there has been no

development other than that in the Ophir formation.

Looation.-The Ophir Hill Consolidated mine is

about a quarter of a mile northwest of Ophir, and the

working adit and drain tunnel are in the north wall

of Ophir Canyon just west of the town.

Development and production.-The properties of

the Ophir Hill Consolidated mine include a consolidation of many claims, of which the Wild Delirium,

Miner's Delight, Bartlett, Northern Light, Bannock,

Burnett, Cooley, Severe, Maud S., Our Boy's, and

First Northerly Extension of the Miner's Delight have

so far proved most valuable.

The development of the mine was first carried out

by inclined shafts in the ore, but in 1911 a drain tunnel about 2,400 feet long was driven, with an alti~ude

at the portal of 6,502 feet. Considerable drifting was

done on the drain-tunnel level and on the 200 and 400

foot levels below it. All together more than 10,000

feet of drifts and tunnels have been driven, with many

raises and a few winzes, and the stope workings must

be of even greater length. The water in the mine

stands at the level of the drain tunnel. No information was obtained as to its natural level before the

completion of this drain.

The production of the mine began about 1870. The

mine was idle for many years in the period between

1880 and 1897, but work was resumed then and continued until 1926, when the mine was abandoned, being considered exhausted. During this period over

1,200,000tons of ore was produced, and the value of

the output must have exceeded $15,000,000and may

have approached $20,000,000. The ownership of the

stock has been so closely held that no information as

to dividend payments is available, but it is known that

the mine has been very profitable, especially from a

time shortly after 1900 to the cessation of operations

while under the ownership of the ·W. A. Clark

interests.

Geology.-The productive workings of the Ophir

Hill Consolidated mi~ are all confined to the Ophir

formation and almost entirely to a few limestone beds

of the formation. (See pI. 28.) The most consistently

mineralized limestone is that known as the "Copper

vein" limestone. It is about 8 feet thick and is about

110 feet above the base of the formation. Just below

the "Copper vein" limestone and separated from it

only by llh to 2 feet of shale is the" Blue vein" limestone, about 6 feet thick. This is also consistently ore

bearing and is commonly mined in one stope with the

"Copper vein." About 25 feet above the" Copper

vein" limestone and separated from it by barren shale

is a 10 to 14 foot limestone known as the" Middle

vein" limestone. This in turn is separated by 25 feet

of shale from the" Big vein" limestone, which ranges

from 20 to 40 feet in thickness. A 2-foot shale partir..g divides the" Big vein" limestone from the" Top

vein" limestone. Still higher, at the top of the formation, is a 5 to 8 foot limestone to which no name

has been given. This bed is also locally altered to ore.

The "Copper vein" limestone, with its close associate the "Blue vein" limestone, is most widely replaced and has furnished the largest ore bodies of the

mine. The" Middle vein" and" Big vein" limestones

are less consistently ore bearing, and ore bodies in the

" Top vein" limestone are only sporadic.

Almost all the workable ores of the mine occurred

in the block of ground in the angle between the Cliff

fault and the Canyon fault. Considerable exploratory

work was done on the northwest side of the Cliff fault

but was rewarded by only very meager discoveries. It

seems very probable that the localization of the ore

was due primarily to the shattering of this wedgeshaped block during the faulting.

In this wedge-shaped block the strata strike N. 60°-

75° W. and dip 15°-25° NE., forming part of the

northeast limb of the Ophir anticline. The attitude

of the rocks is very regular except close to the Cliff

fault, where there is a great deal of drag and much

slicing of the rock into horses of large and small size.

There are few faults of any consequence except the

Cliff fault and its branches. A nearly vertical fault

called the Big fault, with a downthrow to the north

of 40 feet, cuts the" Copper vein" about 300 feet down

the dip from the outcrop in the Wild Delirium stope.

This fault curves from a course about N. 70° E. to

about N. 55° E. and also cuts the Miner's Delight

stopes at about 300 feet down the dip from the outcrop. A number of steep faults having throws as great
as 5 feet also occur in the mine. They strike generally

east, and all but one also show downthrows to the

north, like the Big fault. The ore bodies cropped out

a short distance north of the Canyon fault. The ore

occurred in blanketlike replacement masses along a

series of roughly northward-trending fissures, following the intersection of the fissures with the several

favorable limestone beds. There were also very large

stopes in the sliced rocks in the Cliff fault zone and

in the hanging wall of the Cliff fault.

The stopes along the Cliff fault extend for over

2,000 feet, though not continuously mined for this distance. The very rich Clark stope was developed at the

west end of this zone in the "Copper vein" in the

. hanging wall of the Cliff fault. A large ore body

was found in the "Middle vein" above and west of

the Clark stope, and a smaller stope was developed

in the "Big vein."

Along the Cliff fault to the northeast the Senator

stope was developed in a horse of the" Big vein," and

from this point a practically continuous series of stopes

were developed to the northeast along the plunging

intersection of the limestones of the Ophir formation

and the Cliff fault. Many of these ore bodies were in

horses in the fault zone, and their proper description

would require a detailed map, permission to publish

which was not received.

Of the ore bodies localized along fissures, the most

westerly was the West stope. This was developed,

with some small interruptions, for over 500 feet from

the intersection of the "Copper vein" with the Cliff

fault. It trends from due north to N. 75° W. The

principal stope was in the "Copper vein" and was

locally 50 feet wide but probably averaged less than

15 feet. The" Middle vein " stopes were not so per-.

sistent nor so wide, and the "Big vein" was mined

for only about 200 feet along the fissure. None of the

ore bodies along this fissure system extended to the

surface. A branch of the West stope fissure system

trends easterly, and the stope along it in the" Copper

vein" connected with the " Copper vein" stope along

the Miner's Delight fissure system, some 150 to 200

feet east. Two other small ore bodies were found

along fissures between the West stope and the Miner's

Delight.

The Miner's Delight fissure system trends almost

due north and has been mined for a pitch length of

1,450 feet from the outcrop, practically to the intersection of the "Copper vein" with the Cliff fault.

Ore bodies in all the beds were very good, the " Copper vein" stopes averaging about 40 feet in width, the

"Middle vein" about 10 feet, the "Big vein" about

40 feet, and the " Top vein" being more continuously

productive along this fissure system than anywhere

else in the mine, some of the stopes in it being 80 feet

wide. .

A few small ore bodies occur along minor fissure

systems 100 to 150 feet east of the Miner's Delight

system, but they were not continuous, although one

stope over 300 feet long was developed in the " Copper vein" south of the Cliff fault.

The next major fissure system east of the Miner's

Delight was the Wild Delirium, which extends in a

course about 300 feet east of and subparallel with the

Miner's Delight fissure system. It controlled the

largest and most valuable deposits in the mine. The

ore bodies extended from the outcrop to the Cliff

fault in the " Copper vein," about 1,500 feet in pitch

length, and were only slightly less continuous in the

"Middle vein" and "Big vein" limestones. Except

near the outcrop no valuable ore bodies were found

in the "Top vein" limestone. The ore body in the

"Copper vein" limestone was 90 feet wide for several hundred feet along its pitch, but near the surface, owing to a branching of the fissures, it attained

a width of 120 feet. These brunching fissures near

the outcrop showed some continuation down the dip

about 200 feet east of the Wild Delirium fissures

proper, producing the ore body mined in the Peterson

stope, a continuation of the very rich Bonanza stope

just below the outcrop. Caving had rendered this

portion of the mine inaccessible at the time of this

survey, so that the mutual relations of the fissures

could not be ascertained.

In the "Middle vein" and "Big vein" limestones

the stopes along the Wild Delirium fissure system

were very wide near the surface, exceeding 100 feet

for short distances, but were very much narrower

down the dip to the north, averaging 20 to 30 and

10 feet, respectively, in width.

The 7112drift was run in the " Copper vein" limestone east from the Wild Delirium stopes at the draintunnel level and revealed ore bodies along two fissure systems. One fissure about 250 feet east of the

Wild Delirium localized ore bodies that were minable

for about 500 feet in the "Copper vein" and for

about 100 feet in the" Middle vein" limestone. The

other system, about 120 feet farther east, localized ore

bodies that were mined for over 600 feet in the

"Copper vein" and nearly as far in the "Middle

vein" and "Big vein." None of these ore bodies

cropped out.

A few smaller ore bodies were found east of the

Wild Delirium system, practically along the Cliff

fault at and below the 200-foot level below the drain

tunnel.

Extensive explorations were made on the northwest

side of the Cliff fault, chiefly in the "Copper vein,"

which was followed for about 800 feet on the draintunnel level, about 300 feet on the 200-foot level, and

over 1,700 feet on the 400-foot level, but only two very

small ore bodies were found. The" Big vein" was
~---

I

I

i

explored on the 200-foot level for about 1,200 feet of

strike length northwest of the Cliff fault without success and on the drain-tunnel level for a short distance, where a small ore body was found. Explorations in the lower beds of the Hartmann limestone

northwest of the Cliff fault on the tunnel level were

fruitless.

Essentially aU the fissures along which the ore

bodies were localized are nearly vertical, with perhaps slight westward inclinations. They are surprisingly inconspicuous, considering the great size of

some of the ore bodies. Commonly the fissures are 2

to 3 inches wide, but locally they attain about 4 inches

and elsewhere shrink to mere knife-edges. As a rule

there are several such fissures in a zone as much as 4

feet wide, within which they are found to join and

separate continually when followed along the stope

roof. Despite their narrow width and the additional

facts that they sharply cut the replacement ore that

made most o'f the ore bodies of the mine, and furthermore, although almost without galena or sphalerite,

carry much more pyrrhotite, chalcopyrite, and tennantite than the replacement me, their central positions in the stopes and their never-failing presence

are conclusive evidence of their genetic relations to

the replacement ore. They are traceable in the shale

between the ore bodies as well as in the shale and

quartzite below the "Blue vein" limestone where the

workings have extended.

On reaching the conclusion that the Ophir Hill Consolidated mine on the north side of the Canyon fault

was exhausted, the company began search for another

ore body south of this fault. If the Canyon fault had

been postmineral, they would have been practically assured of success, but the evidence of a premineral age

of this fault is almost conclusive, rendering the results

of exploration by deep shaft south of the fault much

more uncertain. After diamond drilling had revealed

some pyrite in limestone of the Ophir formation

south of the Canyon fault, a winze from the end of a

3OO-footunnel in the south wall of Ophir Canyon was

begun in 1926 and carried to a depth of about 1,400

feet. Drifts were run in the Tintic quartzite in search

of fissures and also in the" Copper" vein limestone of

the Ophir formation, but without result. The work

was abandoned in 1928.

Evidence of the premineral age of the f!llultingmay

be summarized as follows: First, the practical absence

of ore northwest of the Cliff fault would hardly be expected were this fault postmineral. Second, the fraying out into northeastward-bending "horsetails" of

almost all the mineralized fissures just south of the

Cliff fault suggests that the fault was earlier than the

fissures. Third, the mineralized limestones in the

Cliff fault zone show no evidence of drag. Fourth, I

the Cliff fault has clearly localized metamorphism on

the hillside between the Ophir Hill and Cliff mines

and hence is premineral. Fifth, vugs in the Cliff

fault zone contain anhedral pyrite and galena, which

also occur in the fault gouge, although no broken crystals are seen there. The Cliff fault appears to be a

branch of the Canyon fault. (See p. 75.) Sixth, the

mineralized fissures show no offsets where they cross

the small faults that are parallel to the Canyon fault,

and these small faults are mineralized well away from

any limestone beds, proving their premineral age~

Their parallelism to the Canyon fault suggests that

they are of the same age as the Canyon fault, which

hence is also premineral. Seventh, the Canyon fault

carries quartz-pyrite filling locally, as above the Ophir'

Hill mill. Eighth, the rhyolite dike that crosses the

Canyon and Cliff faults without offset and is clearly

later than these faults has been mineralized in the

Hidden Treasure mine. Ninth, the manganese mine

of the Ophir Hill Consolidated Co. follows a fissure

system that is parallel to and only a few score feet

from the Canyon fault. The manganese (introduced

as manganiferous calcite) was almost surely formed

at the same time as the lead and zinc minerals, which

were hence la·ter than the Canyon fault.

Some of the evidences above enumerated are not

strong, but others are nearly conclusive in themselves,

and all suggest the same conclusion-namely, that the

Cliff and Canyon faults are both premineral. Accordingly this conclusion carries considerably greater

weight than it would have from any single line of

evidence.

The conclusion drawn from the evidence just cited

is directly contrary to that of Olmstead 97and Wichman,98neither of whom states the reasons for his conclusion. The exploratoiI'y work carried out by the

Ophir Hill Consolidated Co. south of the Canyon fault

apparently confirms the evidence that the mineralizatIon occurred later than the faulting.

Twelve carloads of manganese ore was mined during the World War by the Ophir Hill Consolidated

Co. from the Bowman limestone, just south of the

Canyon fault on the spur between Hartmann Gulch

and the gulch in which the easterly outcrop of Tintic

quartzite occurs. The ore was all oxidized, consisting

of pyrolusite, psilomelane, and wad, undoubtedly

secondary after manganiferous calcite. The ore was

localized in the hanging wall and alOlIlgbranches of a

fissure that trends due east and dips 80° N. The limestone has been replaced through a vertical distance of

about 60 feet and locally to distances of 6 to 8 feet to

the side of the fissures. Certain limestone beds appear

fl7 Olmstead, S. G., Economic geology of the Ophir mining district:

Econ. Geology, vol. 16, p. 447, 1921.

os Wichman, F. M., The Ophir mining district, Utah: Eng. and Min.

Jour, vol, 110, p. 562, 1920. .
to have been selectively replaced, leaving nodular limestone residua convex toward the fissures, but on the

whole the irregular minor fractures that abound in the

rock have guided the replacement. Mining was done

by the room and pillar method.

The ores.-The ore of the main Ophir Hill mine

was composed of mixed pyrite, galena, sphalerite, and

chalcopyrite, with some argentite occurring in the

galena and some tennantite and pyrrhotite as minor

constituents. The gangue was extremely. variable,

rl1nging from nearly all silicate to fairly pure limestone with only a small percentage of insoluble matter.

The insoluble matter in the ore ranged from 13 to 92

per cent. This made selective flotation very difficult,

owing to the variable effects of the changes in lime

content of the mill heads.

The metal contents did not vary systematically from

one bed to another nor from one fissure to another,

although there were considerable fluctuations in the

relative proportions of the several metallic minerals

within any given ore body.

The tenor was rather low except near the outcrop of

the Miner's Delight and Wild Delirium fissure systems, where oxidation had produced very rich lead

carbonate and silver ore. This did not extend more

than 75 feet down the dip, according to Mr. E. S.

Bowman, of the Ophir Hill Consolidated Mining Co.

Along the Cliff fault oxidation occurred to much

greater depth, supergene chalcocite being found on the

Miner's Delight level, about 2·5feet above the ·drlli~

tunnel. The average of the ore mined in the latel

years of activity ran about 1.3 per cent of copper, 5.5

to 6 per cent of lead, 6 to 7 ounces of silver to the ton,

4 to 8 per cent of zinc, 12 per cent of iron, and 42 per

cent of insoluble material. The gold content was insigllificant. The lime content of mill heads averaged

about 8 per cent. Most of the ore was milling ore, but

some ran 12 to 15 per cent of lead, 2 per cent of copper,

and 15 ounces of silver to the ton and was shipped as

mined. A little copper ore, running 4 to 5 percent of

copper, 3 per cent of lead, and 15 ounces of silver to

the ton, was also shipped. In general, high copper was

accompanied by high silver content and very low lead.

The maximum contents reported on carload lots were

15 ounces of silver to the ton, 15 per cent of lead, 10

per cent of zinc, and 30 per cent of iron. The small

amount of manganese mined ran 47 to 48 per cent of

manganese and 1ounce of silver to the ton.

Until 1921 the ore was milled by straight gravity

concentration with jigs and tables, but in that year

the jigs and fine tables were eliminated and replaced

by flotation. In 1924 the tables were also eliminated

and flotation was used alone, with about 30 per cent

better recovery of copper and about 10 per cent better

recovery of lead and silver. The tailings losses were

copper 0.096 per cent, lead 0.5 per cent, silver 0.6 ounce

to the ton. The extraction, according to R. V. Thompson, mill superintendent, was about 90 per cent of the

copper, 91 per cent of the silver, 93 per cent of the

lead, 55 per cent of the iron, 67 per cent of the zinc,

8 per cent of the silica, and 8 per cent of the lime contained in the mill heads. The concentration was about

2.5 to 1, and the concentrates ran, when the process

was standardized, about 20 to 30 per cent of lead, 4

per cent of copper, 30 to 40 ounces of silver to the ton,

and 7 or 8 per cent of iron.

The Ophir Queen prospect is in Hartmann Gulch

a few hundred feet north of the Ophir schoolhouse,

just north of the northern branch of the Canyon fault.

Brooklyn portal

a 100 Feet

, f ,

FIGURE 19.-Map of the accessible workings of the Brook·

lyn mine, Dry Canyon

A shaft was sunk here about 250 feet, and a small

amount of drifting was done in the limestone of the

Ophir formation. No production was ever reported,

and the shaft was abandoned at the time of the survey

in 1926.

The Brooklyn mine is in Dry Canyon about a quarter of a mile north of the Kearsarge. It was discovered in the early days of the district, and most of the

work was done at that time. No data on the early

production are available. Less than 1,000 tons of ore

was extracted at about the time of the World War,

but the mine was inactive at the time of the writer's

visit, and most of the workings were caved and inaccessible. The accessible portions, amounting to

about 1,000 feet, are shown on Figure 19. From the

small amount of workings visible it is difficu~tto say
what conditions governed the ore bodies. They appear, however, to have been chiefly replacement pods

and masses in the limestone of the" Great Blue," just

above the Long Trail shale member~ Many faults and

fissures cut the beds and confuse the structure somewhat, but in general the beds strike N. 35° W. and dip

20°-25° NE., in conformity with their position on the

east flank of the Ophir anticline. There appear to

have been at least two beds that were productive, one

about 130 to 140 feet stratigraphically higher than the

other. In some places fissures seem to have localized

the ore, but other stopes reveal no fissuring.

The ore was apparently all oxidized and contained

lead, silver, and copper. The average tenor of the

ore mined since 1910 would be about 11 per cent of

lead, 4 per cent of copper, and 6 ounces of silver, and

about $1.30 in gold to the ton.

The Commodore mine is on the southeast flank of

Bald Mountain, northeast of the Brooklyn mine, in

Dry Canyon. It is in the "Great Blue" limestone

above the Long Trail shale member. As the workings

were caved and inaccessible at the time of this survey

in 1927, nothing is known of the geology of the ore

bodies. A small amount of ore was mined in the

decade preceding 1918, but the total production was

probably less than $10,000, chiefly in lead and silver

ore, with a little copper and gold.

The Deseret mine is on the north wall of Dry

Canyon on the spur below the Kearsarge mine. It

was worked in the early days, but has long been idle.

Its total production has been only a few thousa·nd

dollars.

The mine is developed by an incline parallel to the

bedding and about 750 feet deep, with a few short

drifts and some small stopes parallel to the incline.

Altogether about 1,500 feet of workings have been

opened.

The mine is in the Deseret limestone, near the top.

The beds here strike almost due east and dip about 35°

N. at the surface, but flatten to 15° at lower levels.

The limestone in which most of the workings of the

mine were driven is considerably altered to hornfels,

especially along the fissures, which trend generally

north through the mine. It is overlain by a quartzite

that is similarly altered, with the development of diopside. The ore is reported by Huntley 1 to have occurred as a chimney deposit, following the beddmg.

It assayed 70 ounces of silver and a trace of gold to the

ton.

The Eureka-Ophir mine is in Dry.Canyon just east

of the portal of the Sovereign tunnel of the Hidden

Treasure mine. It was worked sporadically from

about 1913 to 1921 and at the time of the writer's visit

was under lease, but little was being done. Nothing

is known of its earlier history.

The mine is opened by an inclined shaft about 300

feet deep, which was badly caved at the time of the

visit. The mine is in a brecciated mass of Deseret

limestone and rhyolite porphyry, chiefly above the

basal shale of the Deseret. The workings that penetrate below this shale give no evidence of having ever

been productive, despite the fact that all the production of the adjacent Hidden Treasure mine came from

beds below this shale. There is much fissuring of the

breccia above the shale, but very little below. The ore

apparently made along these fissures, which trend generally north. The ore was oxidized throughout. It

averaged about 6 per cent of lead, 6 per cent of copper,

and 9 ounces of silver and 25.cents in gold to the ton.

The Kearsarge mine is in Dry Canyon on the spur

east of the old Mono incline, about 150 feet above the

road to the Granite tunnel of the Hidden Treasure

mine. It is reached by wagon road from Stockton,

about 7 miles.

The mine is developed by an incline subparallel to

the bedding and about 1,300 feet long, and at the time

of the writer's visit a tunnel about 450 feet long and

about 200 feet below the main adit was under way to

prospect the ground beneath the Callahan stope.

With the few short levels in the mine, the total development work is probably about 3~000feet.

Despite the small amount of workings in the mine

it has proved very productive. It was first located in

1871, and its output to 1880 was reported as probably

about $1,000,000.2 Since that time work has been

very sporadic and done chiefly by lessees operating on

a small scale. A small production has been reported

up to the present time, but the total output since 1911

probably does not exceed 1,000 tons of ore.

The workings of the mine (see fig. 20) are somewhat above the middle of the Humbug formation.

The beds here form a part of the east limb of the

Ophir anticline but locally strike a little north of

east and dip about 30°-35° N. The beds are cut by a

number of fissures trending N. 30°-60° E., most of

which dip steeply east without marked offset of the

beds, although they are accompanied by considerable

brecciation. A small northwest fault is cut by the

incline about 700 feet down, and a few small northeast

faults also occur in the workings.
The ore occurred as fissure fillings and replacement

masses in the brecciated quartzite and limestone olfthe

Humbug formation. Some alteration to hornfels has

occurred along the limestones, but there has been little

replacement of them by ore. The richest ore body Was

in the Callahan stope between quartzite wans. The

ore bodies were not confined to any particular stratigraphic horizon, although there is a crude tendency

for them to be subparallel to the bedding. The ore

was chiefly oxidized ore, although some sulphides were

found in the Callahan stolpe and at lower levels.

rUNNeL ==

~

The mine is in the" Great Blue" limestone just below the Long Trail shale member, in beds apparently

equivalent to those in which the Mono mine was developed. The writer was denied access to the property, so that nothing can be stated regarding the shape

and size of the ore bodies. It is known, however, that

little ore has been so far developed.

The Mono mine, a part of the Ophir-Mono coalition' is on the north side of Dry Canyon about half

SECTION

FIGURE20.-Map and section of the Kearsarge mine workings, Dry Canyon

Jarosite, smithsonite, azurite, malachite, aurichalcite,

plumbojarosite, and" limonite" were seen in the mine

llnd on the dumps, with a little galena.

The tenor of the ore mined in the early days was

very high, some assays reaching $10,000a ton in silver.

The ore mined by lessees in recent years has been, of

course, much poorer. It averages about 7 per cent o~

lead, 2 per cent of copper, and 18 ounces of silver and

about $1.25 in gold to the ton.

The Magnolia mine is on the north wall of Dry Canyon a few hundred feet west of the upper portal of the

Mono mine. A tunnel is driven beneath the upper

workings from a point about 300 feet lower. A great

deal of exploratory work was done here in the early

days, but the total production is reported by Huntley

to have been small. Within the last decade a few

score tons of ore has been extracted.

a mile from Gisborn post office. It is reached by the

Gisborn road from Stockton, about 6 miles distant.

Developments arrul prodwction.-The Mono mine is

developed by means of an incline whose mouth is at

an altitude of about 8,450 feet and which follows the

dip of the strata for several hundred feet. This incline was worked in the early days but was largely

caved at the time of this survey in 1927, and its depth

is not known. A short tunnel, about 650 feet long,

was driven at an altitude about 150 feet lower, and a

longer one at about 450 feet below the collar of the

incline, beginning just above the bed of Dry Canyon. It was extended over 1,100 feet before 1880, but

soon afterward work was abandoned, and except for

a few lessees little work was done until 1927. Under

the direction of M. C. Godbe work was resumed under

the name Ophir-Mono Coalition, which includes the

properties known as the Surprise tunnel, Queen of the

Hills, and several others as well. The Mono lower
tunnel was being rapidly extended at the time of the

writer's visit to the mine, and there were at least

3,200 feet of workings on the lower tunnel level.

The production of the mine was very great in the

early days, close to $1,000,000being produced in the

years between 1871 and 1875. Since then work has

been done only sporadically, and the production has

probably not exceeded $100,000.

Geology.-The Mono mine is in the Deseret limestone, Humbug formation, and "Great Blue" limestone, but essentially all the productive workings are

in a 3 or 4 foot limestone bed in the "Great Blue"

limestone about 190 feet beneath the Long Trail shale

member, according to the detailed work of H. G.

Mitchell, superintendent. It thus roughly corresponds

in stratigraphic position with the Lion Hill and Mercur mines.

The mine is in a downfaulted block, bounded on the

east by the Corbon fault and on the west by the GarberMark Antony fault. The Corbon fault is well exposed

in the lower tunnel of the mine, the portal of which

is in the footwall of the fault. The principal fault

surface where it is cut by the tunnel about 150 feet

from the portal (see pI. 29) strikes N. 25° E. and dips

30° NW. The tunnel passes into the hanging wall of

the fault for some distance but swings back and again

intersects the fault about.2,000 feet from the portal.

Here the fault strikes N. 20° E. and dips 48° NW.

The Corbon fault where followed southwest from

the portal curves westward and then turns northwest,

becoming one with the Garber-Mark Antony fault.

(See pI. 11.) The wedge-shaped block between them

includes the Mono mine. These faults are described

in detail on pages 78-80. Their apparent displacement is about 650 feet and 750 feet, respectively.

Within the block defined by these faults the strata dip

generally about 30°-40° NE. and strike N. 30°_55°W.,

forming part of the east limb of the Ophir anticline.

They are cut by many northeastward-trending faults,

chiefly of small displacement, though of great economic importance, as the bonanza shoot of the old

Mono incline is reported to have been cut off by such

a fault.

The upper Mono incline of the mine follows down

the intersection of a fissure that trends N. 5° E. and a

limestone bed that strikes about N. 50° W. and dips

28° NE. The ore made out into the limestone as

replacement masses as much as 30 feet wide and 3 or

4 feet thick. About 350 feet down the incline this ore

shoot was cut off by a fault trending N. 45° E. with a

steep dip to the northwest. The fault is apparently

normal and has a throw approaching 200 feet, for a

black shale that is almost surely the Long Trail shale

member of the "Great Blue" limestone is dropped

opposite the ore-bearing bed. These relations are

exhibited by the workings accessiblethrough the upper

tunnel of the mine.

The upper tunnel penetrates for nearly 200 feet

I from the portal a mass of rhyolite porphyry, which

is much pyritized. The porphyry mass is then cut off

by a fault trending N. 15° E. and dipping 75° NW.

Beyond this the tunnel cuts across the strike of the

"Great Blue" limestone at a low angle for several

hundred feet, finally passing under the incline. Apparently no attempt was made to prospect the favorable limestone of the are shoot along its strike.

The lower tunnel passes through a breccia zone of

Deseret limestone for about 150 feet, then through

the Corbon No.1 fault, into what is probably the uppermost part of the Deseret limestone in the hanging

wall of the fault. These beds it penetrates at a low

angle with the strike for a little over 200 feet and,

then cuts a fault, of probably slight displacement,

trending N. 30° E. and dipping 80° NW. The Humbug formation, striking N. 40° W. and dipping 27°

NE., is encountered in the hanging wall of this fault

and is penetrated, through slightly broken country,

for a little over 600 feet. Here the tunnel forks, one

branch extending on north-northeastward through the

Humbug formation and finally intersecting the Corban No. 1 fault again. Along this tunnel a few small

are bodies following narrow fissures were stoped. The

largest of these was a peculiar curving' body dipping

at a flat angle northward just south of a steep fault.

Apparently this branch of the tunnel fails to reach

the " Great Blue" limestone, although it must be very

nearly through the Humbug where it strikes the Corbon fault for the second time. This fault is penetrated, and stapes are developed in a steeply dipping

fault zone in its footwall. This footwall fault zone,

which strikes N. 40° E. and dips 45° SE., has been

mined for 60 or 80 feet below the tunnel level along

about 200 feet in strike. The ore body was apparently about 3 to 5 feet wide.

The northwest branch of the tunnel was being actively advanced at the time of this survey. From the

fork of the tunnel it follows the strike of the Humbug

formation for about 150 feet, then a small northwardtrending fault for a short distance, then the strike

again. About 350 feet from the fork it penetrates a

N. 60° E. fault dipping 60° NW., and a short distance

ffirther on a very strong fault with parallel strike but

somewhat flatter dip (46°). North of this flat fault

the drift is in the" Great Blue" limestone and at the

time of this survey was being extended southwestward

to intersect the limestone bed that was so productive

in the upper workings.

The ore in the upper workings of the Mono mine

was oxidized, consisting of lead carbonate, horn silver,

malachite, jarosite, azurite, and" limonite." On the

lower tunnel level it was chiefly sphalerite, galena,

pyrite, and chalcopyrite in a gangue of lime silicate

rocks. There was little alteration in the upper workings away from the ore bodies proper.

The tenor of ore in the early days must have been

very high, but no data are available. The oxe shipped

since 1910 averaged about 17 per cent of lead, 3.6 per

cent of copper, and 16 ounces of silver and $1 in gold

to the ton.

The Queen of the Hills mine is in Dry Canyon, in

the southward-facing spur at whose crest is mineral

monument No.5. It is about a quarter of a mile from

Gisborn and is reached by wagon road from Stockton,

about 61;2miles away. The mine was located in 1870

and vigorously worked till 1877,but since that time a

little desultory work by lessees has been the sole activity. In 1915 and 1916 considerable zinc ore was

shipped. The mine is now owned by the Ophir-Mono

Coalition. The production of the mine in the early

days probably exceeded $1,000,000,but it is doubtful

whether more than $30,000 has been recovered in the

last 20 years.

The mine is in the Deseret limestone, about 100 feet

below the base of the Humbug formation, although

there is a quartzite immediately overlying the productive limestone of the mine which might be considered

the basal member of the Humbug. The ore made

along the intersection of three fissures with the bedding of the limestone. The limestone strikes almost

due east and dips about 20°-25° N. The fissures trend

about N. 20°-35° W. and are reported to have been

cut off in depth by two faults, one of which is supposed to be a branch of the Mark Antony fault, the

other a northeastward-trending fault. The ore shoots

were not found on the north side of these faults.

Huntley 3 says:

The dip of the chimneys is N. 30° W., being oblique to the dip

of the strata. The distance between them is about 80 feet and

150 feet. Two faults were found, one along the line of the

Mahogany chimney, northeast and southwest, and the other

nearly at right angles to it, faulting all the ore shoots and

dipping a little northeast. * * * The first chimney was 350

feet long (before being cut by the fault) and was from 25 to

40 feet wide, having a thickness of from 18 inches to 2 feet

of ocherous ore containing but little copper and said to assay

from 20 to 25 ounces silver and 50 per cent lead. The second

chimney was 1,000 feet long, from 60 to 70 feet wide, and also

had from 18 inches to 2 feet of ore, generally upon the hanging

wall, assaying about 40 ounces silver and 30 per cent lead.

The third chimney was about the same size as the second, but

the ore contained some tetrahedrite, much malachite, and a

little lead and assayed about 60 ounces silver. The claims are

opened by two main inclines 1,000 and 1,400 feet long and 6

feet square, which branch near the surface like the letter Y.

The horizontal development is 1,200 feet. It is claimed that

• Huntley, D. B., Tenth Census U. S., vol. 13, p. 453, .1885.

67463-32--11

there are 8 miles of openings, but if the stopes were not counted

there would probably be not over 12,000 feet.

The stopes of the mine were reported by Mr. A. J.

May to be practically all caved, although the haulageways are still partly accessible. The purpose of the

Surprise tunnel (see below) is in part to explore for

the faulted continuation of the ore shoots of the Queen

of the Hills.

The ore shipped in recent years has averaged about

19 per cent of zinc, 6 per cent of lead, 1.4 per cent of

copper, and 7 ounces of silver and 30 cents in gold to

the ton.

The Surprise tunnel, now a part of the Ophir-Mono

coalition workings, is at Gisborn post office, on the

west flank of the southwest spur of Bald Mountain.

It is reached by wagon road from Stockton, about 6

miles distant. There has been a great deal of work

done through the Surprise tunnel, including at the

time of the survey, in 1927, about 4,200 feet of tunnel

and over 500 feet of raises, but very little ore had been

developed. The production has been only a few score

tons, shipped in 1916, 1918, and 1920, the total value

probably not reaching $10,000.

The tunnel is in the upper part of the Deseret lime-

. stone and in the Humbug formation. The beds form

a part of the west limb of the Ophir anticline and,

near the portal, strike about N. 50° E. and dip about

25°-40° NW. The tunnel begins as a crosscut trending S. 70° E. Three drifts have been driven to the

northeast, one at 200 feet from the portal, a second at

550 feet, and the third at 720 feet. (See pI. 29.) The

drift that leaves the crosscut at 720 feet from the portal is short and somewhat tortuous, subparallel to the

strike of the Deseret limestone. No evidence of mineralization was observed along it, although a northwest fault that intersects the crosscut at the mouth of

the drift has been prospected for a short distance and

carries small quantities of sulphides. The drift that

leaves.the crosscut at 550 feet from the portal trends

N. 50° E. along the strike of a bed in the Deseret

limestone, locally called the "Garber" limestone.

The drift is about 450 feet long and intersects two

mineralized fissures, both nearly vertical. The first

has been followed by a raise about 80 feet long along.

the intersection with the "Garber" bed, which here

dips about 40° NW. The second has been prospected

by a winze about 100 feet below the tunnel and a raise

about 400 feet long above it. The small amount of

ore yet produced by the tunnel was obtained from this

raIse.

The principal prospecting work from this tunnel

was carried out along the drift that leaves the adit

crosscut at 200 feet from the portal. This has been

driven northeast for about 1,700feet at about the same

.~

__._~_~__.~~.~_.J
stratigraphic horizon. The limestone followed by

this drift is considered by the men in charge to be

probably the same as the one in which the Queen of

the Hills mine was developed. Like the Queen of the

Hills bed, it has a quartzite overlying it, but talus

rrevents verifying by surface tracing the probable

correlation of the beds. Both beds are cOlIl.sideredby

the writer part of the Deseret limestone, despite the

presence of the quartzite, which might be included in

the Humbug formation. The base of the Humbug is

a purely arbitrary boundary, but as the quartzite here

considered is several scores of feet lower than the principal group of sandrocks it is included as part Otfthe

Deseret limestone of the present report.

Open fissures, "watercourses," both parallel and

crosscutting this drift, are encountered for much of

its length. These are not mineralized. About 1,700

feet from the adit crosscut this drift intersects the

Mark Antony fault, a strong fault trending about N.

45° W. and dipping 70°_'75°NE. The fault relations

are those of a normal fault, with the Humbug formation in the hanging wall brought down against the

Deseret limestone. The Mark Antony and Garber

faults are subparallel and really are the dominant surfaces of movement on a sheer zone about 200 feet wide

on this tunnel level. After penetrating the Mark Antony fault the tunnel turns southeast, in the hanging

wall, which is formed by the Humbug formation. A

second fault of the zone is penetrated about 250 feet

farther on, and the tunnel is again in the Deseret

formation for a short distance. It then turns back

southward to the main Mark Antony fault, which it

follows for over 400 feet, with Deseret limestone on

both hanging wall and footwall. A branch of this

tunnel leaves the fault and passes into the footwall for

over 200 feet, where drifts were being run both east

and west in a limestone bed that must be low in the

Deseret formation. A second drift leaves the fault

and trends northeast till it penetrates the Garber

fault, which it follows for several hundred feet, with

-the Humbug formation on the hanging wall and the

Deseret limestone on the footwall. The Big Four

raise was extended vertically up from a crosscut in the

footwall, cutting the fault about 90 feet above the tun-

•nel. A drift was being run from this raise at 115 feet

above the tunnel at the time of the writer's visit. No

evidence of mineralization was found in any of these

workings.

The ores that were obtained from the small bodies

in the Garber raise were chalcopyrite-galena ores with

a little gold and considerable silver. The average

tenor was 13 per cent of lead, 4 per cent of copper,

and 28 ounces of silver and about 30 cents in gold to

the ton.

The Thad Stevens mine is in Dry Canyon just above

the creek bottom northeast of the Eureka-Ophir mine

and southeast of the Deseret. It is in one of a group

Df overlapping claims, which also includes the Deseret

mine.

The mine was worked in the 1870'sbut had been operated in only a desultory way in the 20 years preceding 1927. The total production in the early days was

estimated by Huntley 4 at less than $30,000; since

1910it has surely not exceeded $10,000additional.

The mine is in the Deseret limestone, which here

strikes about N. 60° W. and dips about 25° N. The

mine was caved and the workings inaccessible at the

time of this survey, in 1927, so that details of the

geology can not be given. Huntley described the

mine in 1880 as having a 380-foot incline and about

250 feet of drifts. The ore was in chimney form,

averaging about a foot in width, and averaged 35 per

cent of lead and 30 ounces of silver to the ton. The

ore produced in recent years assays about 10 per cent

of lead, 4 per cent of copper, and 13 ounces of silver

and 40 cents in gold to the ton.

The Utah Queen mine is on the north wall of Dry

Canyon on the first spur west of the Mono mine. It

was located and worked vigorously in the early days,

and a large amount of ore was extracted, but the value

of the output is unknown. In the 20-year period preceding this survey the mine was worked in only a

desultory fashion, with the extraction of about 200

tons of ore, probably not exceeding $6,000 in value.

I

The ore averaged about 11 per cent of lead, 2 per cent

of copper, and 20 ounces of silver and 60 cents in gold

to the ton.

The mine is in the Humbug formation, near the

upper contact. The workings were caved and inaccessible at the time of this survey, and the mode of occurrence of the ore can not be stated. Presumably the

mine resembled the Kearsarge, which is located in

similar beds. Huntley 5 reports about 900 feet of workings in the mine in 1880.

STOCKTON AREA

ARGENT

The Argent mine is the most easterly in the Rush

Valley district, being situated in sec. 20, T. 4 S., R. 4

W., about half a mile east of the Galena King mine.

The Argent is one of the oldest mines in the district

and was actively worked in the early days, but except

• Huntley, D. R, op. ctt., p. 454.

• Idem., p. 454.
for occasional activity by lessees in a small way, it

has been abandoned for many years. The mine is

developed by a shaft reported to be 850 feet deep,

but owing to the destruction of ladders below 300

feet the lower works were not accessibleto the writer.

Little drifting appears to have been done on the upper

levels.

The mine is in the "Galena King" limestone, in

the Oquirrh formation. The beds strike about N. 65°

1V.and dip about 70° NE. The ore appears to have

occurred in two shoots along the Galena King gouge.

These shoots pitch to the northwest, with the intersection of the limestone and two fissures of the northsouth system. The stopes appear to have been rather

large, having lengths as great as 60 feet.

The ore was apparently nearly all oxidized, but a

few remnants of pyrite and galena were seen. The

oxidized ores carried jarosite, plumbojarosite, cerusite, and" limonite." Nothing is known of the tenor

of the ore.

The Ben Harrison mine is in the northeastern part

of the Rush Valley district, high in the gulch to

which it has given its name. It is reached by a very

steep wagon road from Stockton, a distance of about

3 miles. The mine was located in the early days of

the camp and has been operated rather steadily for

a long time, first as the Ben Harrison, then as the

New Stockton. At the time of this survey it was

being operated by lessees under the Combined Metals

Reduction Co.

The mine is developed by means of a vertical shaft

1,000 feet deep, from which levels are turned at 200,

500,700,850, and 1,000feet. (See fig. 21.) Drifts are

run on all these levels and long crosscuts on the 500

and 700 levels. All together the development worki.ngs of the mine aggregate over 9,000 feet. Statistics

of the early production of the mine are not available,

but it probably produced at least $500,000in the two

decades preceding this survey, in 1927.

The mine is in the Oquirrh formation about 7,500

to 8,000 feet·above the base. This part of the formation consists of quartzite and subordinate limestone

beds. Twol limestone beds constitute the principal

sources of ore. These are the " Ben Harrison" limestone, about 40 feet thick, and the "Black Bear"

limestone, about 80 feet thick. They are separated by

approximately 190 feet of quartzite in the normal

sequence, but owing to the gradational contact at the

top of the" Ben Harrison" limestone, which ranges

from limestone to quartzite through an interval of

limy sandstone, as well as to the possible presence of

some strike faults, the measurement is uncertain.

The beds strike about N. 80° E. and are essentially

vertical or even overturned with south dips of 70°.

There has been considerable strike faulting, probably

during the folding, so that the apparent stratigraphic

interval between the "Ben Harrison" and "Black

Bear" limestones in the mine ranges from only 120

feet to nearly 200 feet. Besides the strike faults there

are a number of north-south faults and fissures. Most

of these dip very steeply west, but there are a few

eastward-dipping fissures. Two prominent monzonite

porphyry dikes were encountered in the mine. Both

strike almost due north and dip about 60° W. The

cast dike ranges in thickness from 30 to 60 feet and

on the 200-foot level is split in two. The west dike

is less than 30 feet thick where intersected by mine

workings. These dikes are considerably sheared by

later faulting, and in many places their contacts are

fault surfaces, but the regularity of their positions in

the mine seems to indicate that these faults are chiefly

subparallel to, the dike walls and occasion but slight

offset of them. In addition to the north-south fissures

there are a number of fissures trending between N.

20° E. and N. 50° E. These show little displacement

but are mineralized.

The ore bodies in the mine were confined chiefly to

the "Ben Harrison" and "Black Bear" limestones,

but there were some bodies along fissures in the quartzite, notably above the 700-foot level about 200 feet

south of the "Ben Harrison" limestone drift. The

ore bodies are localized by the fissures and as a rule

dip steeply west, with the intersection of the fissures

and the limestones. The fissure which has localized

the largest ore bodies is the one called the Katherine,

because it is supposed to be the northward continuation of the fissure known by that name in the Honerine mine. It is impossible, however, to verify the

continuity of the fissure from the Honerine, which is

over half a mile to the south. This fissure lies paralreI to the east poryphyry dike, for the most part in

the hanging wall, but where ore occurs in the footwall

it, too, is referred to the Katherine fissure. It is probable that the brecciation along the dike has facilitated mineralization in both walls. There are two

fissures west of the Katherine which also carry ore.

These have received no names. The more important

ore bodies are along the one which lies about 100 feet

west of the shaft on the 700-foot level and is almost

vertical below that but flattens slightly above and is

only about 15 feet west of the shaft on the 200-foot

level.

The ore bodies of the mine have not been very large.

They are only locally as much as 30 feet long in the

plane of the bedding and 10 feet wide. Their pitch

length is variable, some exceeding 600 feet and others

reaching only a few feet or scores of feet.

The hypogene ore consisted chiefly of galena,

pyrite, sphalerite, and chalcopyrite in a gangue of
100m Monzonite porphyry

~

Quartzite

B Limestone

[2J

Mineral fissure

ofault

Surface

200-fool level

500-foot level

..•..•...•.....-+- -+- ...•.. 700-foot level

-------- 8S0-foot level

• ----- lOCo-foot level
manganiferous calcite and quartz. A little arsenopyrite also occurs. Oxidation has been rather thorough to about 800 feet, although a few residual sulphides are found much higher, and there was some

oxidation even at the bottom of the mine. The minerals present in the oxidized ore include plumbojarosite, cerusite, jarosite, malachite, gypsum, and

" limonite."

There is no necessity for pumping, as the mine is

practically dry even at the 1,000-foot level.

The tenor of the ore mined in recent years averages about 22 per cent of lead and 13 ounces of silver

and $1.30in gold to the ton, with a little copper. A

rich shoot of gold ore above the 700-foot level in the

footwall of the east porphyry dike averaged $17 in

gold to the ton, but this is decidedly exceptional.

The mine formerly operated a concentrating mill,

but this had been dismantled for some years at the

time of this survey, in 1927. The low-grade ores were

sorted by hand to bring them to shipping grade.

The Calumet mine is in the NE. ~ sec. 30, T. 4 S.,

R. 4 W.,. in the foothills of the Oquirrh Mountains.

It is reached by wagon road from Stockton, which is

about 1112miles due west. The mine was operated in

the early days and is reported to have been a rather

large producer, but no exact information as to its output is available. During the World War it was reopened after long idleness, and somewhat more than

$60,000was produced to 1920. Since that time it has

been idle. The mine is reported to be opened by a

shaft 600 feet deep, but the workings are full of water

and inaccessible.

The mine is in the Oquirrh formation, about 4,000

feet above the base. The ore is reported to have occurred on the intersection of a fissure that trends N.

20° W. and dips 85° E. with a limestone bed that

strikes N. 70° W. and dips 70° N. Specimens on the

dump indicate that the ore was highly pyritic and

quartzose. Galena, sphalerite, and chalcopyrite were

observed as primary sulphides, and sulphur, malachite, and "copper pitch" as oxidation products.

The average tenor of the ore mined during the

World War was 18 per cent of lead, 0.25 per cent of

copper, and 12 ounces of silver and $2.50 in gold to

the ton. This gold average is considerably higher

than that of any other mine in the district.

Location, prodll,otion, amd development.-The Galena King mine is in the foothills of the Oquirrh

Mountains, about 1112miles northeast of Stockton,

from which it is reached by a wagon road. The property, which has long been one of the most valuable in

the Rush Valley district, consists of the Galena King,

Silver King, Silver King No.2, Silver King West Extension, First Extension West of Silver King No.2,

Theresa, and other claims. The claims were mostly

located in 1865,and the first galena ore shipped from

Utah was produced from this mine. The mine was

only sporadically operated in the period between 1880

and 1900 but had been active from about 1908 to the

time of this survey, in 1927,when it was under lease to

F. A. Dederich and associates.

The mine has been a steady producer, llilthough not

a very large one. Probably the total output somewhat

exceeds $1,000,000,although this is an estimate only,

as nothing is precisely known of its production in the

early days.

The mine is developed (see pIs. 30 and 32) by means

of two inclined shafts, one 500 feet deep, the other

1,000 feet deep. Levels have been driven at 300, 400,

500, 600, 650, 800, 900, and 1,000 feet, llindtwo long

crosscuts on the 300-foot level. Fully 8,000 feet of

development work has been done in the mine.

Geology.-The productive workings of the Galena

King mine have been practically confined to a 20 to

40 foot limestone bed in the Oquirrh formation. This

bed, locally known as the "Galena King" limestone,

is 1,100 feet stratigraphically higher than the" Honerine " limestone. It has been the productive bed in

the Argent, No You Don't, and Tiptop mines, and

problliblyin the Bullion mine also.

The beds of the Oquirrh formation strike almost

due east and dip about 65° N. in the Galena King

mine, in conformity ~ith the general structure on the

northeast limb of the Ophir anticline. The strata are

cut by a number of northward-trending, chiefly westward-dipping fissures with a few faults. Two monzonite porphyry dikes occur in the mine, striking and

dipping conformably with these fissures. The" Galena King" limestone is notable for the presence of the

"Galena King gouge" which almost invariably accompanies it. This gouge is " limonitic" sericitic material with some jarosite, ranging in thickness from an

inch or so up to over a foot. In places it is near or at

the footwall of the limestone, but elsewhere it occurs

at a higher horizon, though rarely above the middle.

This gouge is considered by the operators an index

feature of the ore bodies, and in exploration by drifts

it is followed as the most favorable part of the limestone. The gouge is probably due chiefly to shearing

within the limestone when the strong folding of the

beds occurred but owes its present mineralogy to oxidation of the probably hydrothermally altered gouge

material.

Only a few small faults occur in the mine. Probably the largest is the one known as the 45° fault, from

the fact that that is its approximate dip. This fault
is cut by the east drift on the 300-foot level about 400

feet east of the shaft, where the displacement is rather

small, almost surely not over 20 feet. On the 500-foot

level the fault is penetrated about 180 feet east of the

shaft and on the 800-foot level about 50 feet east.

Here it shifts the west side northward about 70 feet

referred to the east side and is marked by a thick

breccia zone. Presumably the shaft passes through

this fault between the 800 and 1,000 foot levels, but

this part of the mine was inaccessible at the time of

this survey.

Another fault is seen on the 800-foot level about 200

feet west of the shaft. It strikes about N. 20° W.

instead of due north, like most of the others, and

shifts the west side north about 40 feet. The fault is

not recognizable at higher levels, however. A small

scissors fault occurs at the west end of the 300 stope

on the 300-foot level of the mine. This has a steep

east dip of about 70° and on the 300-foot level offsets

the west block north about 35 feet, but on the surface

the displacement is about 30 feet in the opposite sense.

The ore bodies of the mine occur as blanket and

chimney deposits, replacing the "Galena King" limestone along the gouge zone. The large stope west of

the shaft which extended from the 300-foot level

almost to the surface showed no control of the ore

body by north-south fissures. The ore formed a

blanket deposit about 300 feet long and wide and from

1 to 6 feet thick. A chimney deposit about 35 feet

wide connected with this st0pe and continued· to the

800-foot level and, somewhat less strongly, even to the

1,000-foot level. A number of stopes east of the shaft

occur along the intersection of the north-south faults

and fissures and the" Galena King" limestone.

The ore of the mine was largely oxidized to a depth

just above the 800-foot level, although galena was

found in quantities almost to the surface. Between

the 800 and 1,000 foot levels the ore was made up

chiefly of galena with a little sphalerite, chalcopyrite,

and pyrite; above this level it was chiefly cerusite,

jarosite, malachite, plumbojarosite, and "limonite."

Little evidence of alteration is seen in the limestone

except the presence of the sulphide minerals, although

locally there is a small development of hornfels.

The ore mined in the early days consisted of both

oxidized and sulphide ore. The sulphide ore is reported to have averaged 50 per cent of lead and 40

ounces of silver to the ton. In recent years the ore has

shown an average tenor of about 30 per cent of lead,

8 ounces of silver to the ton, and a little copper and

gold. Some zinc ore was also shipped, but its tenor is

unknown.

Location, develo'fYl1Wnt,and production.-The Honerine mine is by far the largest in the Rush Valley district. It is in the foothills of the Oquirrh Mountains

about a mile northeast of Stockton. It is operated

through a long adit tunnel from Bauer, about 1%

miles north of Stockton, at the south end of Tooele

Valley.

The Honerine is one of the oldest claims in the district and was located by General Conno,r in 1865.

Consolidation of the claims into larger units has gone

on for a long time, and in 1910 the Bullion Coalition,

consisting of 77 patetlted claims and fractions, was

formed. In 1924 this property was taken over on

option by the Combined Metals Reduction Co., which

had :for some time maintained a selective flotation

plant at Bauer. Through aII these changes and consolidations the mine is still known locally as the

Honerine.

The property was first wo['ked by means of inclines,

following down the intersection of the productive

limestones and the fissures. After this period, when

each claim had its oWh shaft, a drain tunnel was

driven about 600 feet lower than the mouth of the

Honerine incline, and several ore bodies were mined

through it. This adit, now called the 600 level, was

driven from the bottom of the gulch in sec. 19, T. 4 S.,

R. 4 W., and is reached by the wagon road that also

serves the Galena King mine. After the Bullion

Coalition was formed the present drain tunnel and

haulage level, called the 1,200 level, was driven from

Bauer. This tunnel is over 13,000feet long and effectively drains the country to a depth of about 1,200

feet below the portal of the old Honerine incline.

Winzes were sunk to a depth of 400 feet below this

level, and the lower levels are now being worked

through them at considerable expense for pumping.

The tunnel discharges about 1,500 to 1,900 gallons of

water a minute, which sufficesfor the needs of the mill

and in addition is used to irrigate 160 acres of orchard

and 200 acres of alfalfa land. AII together the development workings in the property aggregate over

50,000 feet, exclusive of stopes.

The production in the mine has been large. In the

early days the mine was vigorously worked, and the

production to 1890 has been estimated at $1,250,000,

from 80,000tons of ore. Between 1890 and 1901there

appears to have been very little production, but activity was renewed soon afterward. The production

of the mine from 1901 to 1927 may be estimated at

about $6,000,000. From 1912 to 1927 the mine was

operated in part by lessees and in part by the owners.

Geology.-The workings of the Honerine mine (see

pI. 31) are all in the Oquirrh formation, which consists of a great series of interbedded quartzites and

limestones. The mine is about 5,000 feet above the

base of the formation.

The stratigraphy of this part of the Oquirrh formation has been carefully investigated in the mine,

and the following section, kindly furnished by W. A.
Young, geologist of the company, with some slight

changes based on work of the writer, represents the

sequence there determined.

Section of part of the Oquirrh formaiUon in the H onerine

mVne

[With names of the productive limestone beds In local use by the

miners I

Quartzite. Feet

••Galena King" limestone______________________________ 20

Siliceous limestone and sandstone_______________________ 20

••Little" limestone_____________________________________ 3

Quartzite______________________________________________ 20

Limestone ~__________________________ 10

Quartzi te __- ____________ ___ _ _ 160

••Rambler formation" (siliceous thin-bedded limestone) __ 180

••Rambler" limestone (rather pure limestone) 4

Quartzite_ __ _______ ____ 90

" Hercules" limestone -:_______________ 2

Quartzite_ ____ _ ____ _ ___ 150

••St. Patrick" limestone_______________________________ 14

Quartzite______________________________________________ 140

"North Ada" limestone________________________________ 3

Quartzite___ _ _ ___ ____ ___ 18

•• South Ada" limestone________________________________ 8

Quartzite and hornfels (the lower 100 feet chiefly hornfels) ~ 230

"Maverick" limestone (only locally present)____________ 5

Quartzite and hornfels_________________________________ 40

" Honerine" limestone 8

Quartzite and hornfels ._ 10

"Little Honerine" limestone___________________________ ]

Quartzite and hornfels.

The thicknesses given in this section are only approximate, and there ,is considerable variability in the

beds. For instance, the "Honerine" limestone is

locally as much as 12 feet thick; the" Galena King,"

45 feet. Considerable strike faulting has occurred

along many of these limestone beds, seemingly because

during the folding they offered less resistance to she8ir

than the quartzite. This may be the cause of some of

the variations in apparent thickness of the beds. For

example, the" Hercules" limestone ranges in thickness

from 4 feet down to a knife-edge and for some distance on the drain-tunnel level is represented merely

by a shear zone with sporadic horses of limestone.

The attitude of the beds in the Honerine mine is

very regular. They strike almost uniformly N. 70°-

75° W. 8ind dip about 60°-75° NE. They are, however, sliced by a multitude of faults and fissures,

locally called" crossings." These faults and fissures

strike between N. 40° W. and N. 40° E., but by far the

greater number are more rigorously confined to trends

of N. 10°_30° E. Nearly all dip westward at angles

between 45° and the vertical, mostly between 60° and

75°. Many of these fissures show little or no displa<lement of the rocks, but others have offset the beds several scores of feet. The intersections of the faults and

fissures with the limestone beds have been the sites of

the chief ore bodies of the district, and the more productive of them have received names. In order from

east to west, the productive crossings are called the

Chico, Weir, Katherine, Basin, Kimberley, Shewee,

Buhl, Palace, Glory' Hole, and Legal Tender. The

Knickerbocker fault west of the Legal Tender crossing

is apparently unmineralized.

The displacement on these fractures is commonly

rotational. The Knickerbocker fault displaces the

west block 10 or 15 feet to the north on the 1,200-foot

level, but on the 600-foot level the displacement is

about 120 feet, the west block having moved relatively

south. Similarly, the Palace crossing shows a displacement of 60 feet on the 600-foot level, the west

block having moved relatively south, but on the 1,200-

foot level the displacement is negligible .

The fault which according to the interpretation independently reached by Mr. W. A. Young and the

writer is much the largest in the district is that which

on the surface passes just east of the Black Diamond

shaft. This appears to have a horizontal displacement of about 800 feet, the west side having moved

relatively south. A thin-bedded cherty limestone of

which about 60 feet is exposed crops out at the Black

Diamond shaft. This limestone is very similar lithologically to the "Paisley" limestone, whose normal

position is about 550 feet above the "Galena King"

limestone. A similar limestone is intersected by the

drain tunnel about 250 feet northwest of the Bullion

crosscut, at about the position to be expected from the

observed attitude of the beds. If the identification of

this bed as the " Paisley" is correct, then the Bullion

workings are in the "Galena King" limestone, for

the stratigraphic interval between them is about equal

to the int~rval measured on the surface between these

bed!:!. The fault can be traced north on the surface,

passing a short distance west of the Southport mine

and about 300 feet west of the Muerbrook mine. At

the Muerbrook locality there is a strong drag, the

" Larsen" limestone having been bent at least 75 feet

out of strike toward the south, in the sense required

by a strong movement of the west block southward

along the fault. Other beds than the "Paisley" and

"Galena King" limestones have not been identified

west of this fault, the exposures being very poorl

so the

interpretation just made must be considered unproved

though very probable.

Besides these fractures, several monzonite porphyry

dikes penetrate the strata. These bodies range in

thickness from a foot or two to over 300 feet, the

thickness of the body locally known as the" Raddatz

porphyry." Like the fractures, the dikes generally

trend north and dip west, though they are rather irregular in outline. They are commonly associated

with and subparallel to the faults and fissures, which

are therefore thought to have controlled them at least

in part.
The ore bodies of the Honerine mine are characteristically pipelike or tabular replacement bodies in

limestone, following the intersections of the fissures

with the limestone beds. As a rule the ore bodies are

the full width of the limestone at the fissure, tapering

in cross section away from it. The bodies are locally

100 feet in strike length but more commonly the dimensions are only 10 feet or so. In pitch length some

of the ore bodies, notably the Palace shoot and Basin

shoot on the "Honerine" limestone, have been followed for over 1,800 feet, from the surface to the

1,600-foot level, where they still persist. Many of

the shoots are not persistent, however, for more than a

few scores of feet.

Ore has not been formed at every intersection of a

fissure with the limestones, certain beds being much

more favorable than others. The" Honerine " limestone is the most favorable bed, or at least the largest

ore bodies yet developed have been found in it. The

" St. Patrick" limestone is also a very productive bed.

The "North Ada," "South Ada," "Hercules," and

" Rambler" limestones are less mineralized. The

crossings differ similarly. The Weir, Katherine,

Basin, Buhl, and Palace are the most consistently

productive fissures, the Basin and Palace being perhaps the best.

Some of the ore bodies, of which that in the Hamp

den stope in the "St. Patrick" limestone is typicall

do not appear to be particularly associated with any

north-south crossings. In the Hampden stope, although it is close to the projected position of the Palace crossing and may be connected with it, there is a

closer association with a gently arcuate fault, which

is subparallel to the bedding. In the opinion of Mr.

Hampden, who was in charge of the development

here, the association with the east-west fault was the

controlling feature of the ore shoot. Similar widening of shoots in places where east-west faulting has

been strong is observable in the Palace ore shoot in

the "Honerine" limestone, both in the drain-tunnel

level and on the 1,600-foot level.

There have been at least five periods of faulting in

the Honerine mine. Early east-west faulting occurred

along many of the limestones. Both hanging wall and

footwall of the "Honerine" limestone are formed by

strike faults on the 1,600-foot level for some distance,

and the "St. Patrick" and Hercules" limestones also

show the same thing. This east-west faulting was followed by the north-south faulting that produced the

crossings and then by the porphyry intrusions. The

porphyry was later faulted by both east-west and

north-south faults of slight displacement (a few feet

as maxima). Mineralization then occurred along fissures of all these periods, and locally, as in the Connor

stope just above the 1,600-foot level, there has been

some postmineral east-west faulting.

The hypogene ore of the mine consists of mixed suI·

phides, pyrite, galena, sphalerite, and a little chalcopyrite and arsenopyrite being most abundant. Tetrahedrite has also been reported but was not determined

in this survey. The relative abundance of the different sulphides varies greatly from place to place in a

given shoot. In some places galena is concentrated,

elsewhere sphalerite, and elsewhere pyrite, without

apparent system. Gold also occurs locally in quantities as great as $19 a ton, although this is decidedly

unusual.

Few gangue minerals have been developed in the

productive limestones alongside the sulphides. Quartz

is almost the only one that is at all abundant, although

wollastonite, diopside, epidote, fluorite, dolomite, and

chlorite have been developed in the limy sandstones

and in the porphyries near the ore bodies.

Oxidation has altered the hypogene sulphides to a

mixed ore, composed of cerusite, plumbojarosite, jarosite, malachite, smithsonite, aurichalcite, pyromorphite, and "limonite." Small amounts of anglesite,

mimetite, beudantite, and wad also occur. The

depth of oxidation is variable through the mine. A

certain amount of oxidatioo has occurred to the greatest depths yet attained, but as a rule a transition zone

between oxidized and sulphide ore occurs about 400

feet above the drain-tunnel level. This zone rises

somewhat to the east and varies somewhat from one

limestone to another. The" Galena King" limestone

was apparently more permeable to the ground water

than the other limestones, and accordingly ore bodies

in it are more deeply oxidized.

The tenor of the ore is variable. The average lead

shipping ore runs about 18 per cent of lead (maximum

33 per cent), with 6lh ounces of silver to the ton

(maximum 12 ounces), 3 per cent of zinc (maximum 6

per cent), 18 per cent of iron (maximum 25 per cent),

0.25 per cent of copper (maximum 1.5 per cent), and

70 cents in gold to the ton (maximum $5) on carload

lots. The milling ore averages about 8 per cent of

lead, 10 per cent of zinc, and 3 ounces of silver, and

50 cents in goJd to the ton. The line between ship.

ping and milling ore is dependent primarily upon the

zinc content but also upon the amount of oxidation of

the ore. The milling ore is handled by selective flotation in a modern well-equipped mill with a daily

capacity of about 450 tons.

The Muerbrook, mine is in the foothills of the

Oquirrh Range in the extreme southwest corner of

sec. 18, T. 4 S., R. 4 W. It is reached by wagon road

from Stockton, a distance of about llh miles. The

mine was located in the early days but has never been

a very large producer. It has been idle since 1922,

and many of the workings were caved at the time of
r

~

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•

~

I

l

<;

~

f, I

r

.,.

~

l.~.'

,.

~~

<

: I

I;[,

11

ii,

~ Limestone

~

.:::;::,.:::

::::':'.:.:.::::Quartzite

............

• Monzonite porphyry

• Shale

I~Olfault

t::<l Mineral fissure

['-(7~Sthke, and dip

Geo/0!5Y shown on 300, 500,

dnd 800 Toof levels onlY

M_·_...--------------------------------
I

I

I

~~UTHP'

I~R,.o,.~:/~~N::~M

EXPLANATION

~

Dikes of monzonite porphyry

~

Stope

E3 'Mineralized fault

E3

Fault, not mineralized

100 0 400 Feet

!, I!! t I

/ ARGENT SHAFT
this survey, in 1927. Its total production is unknown

but perhaps about $200,000, of which about half was

produced within the 10 years preceding 1922. The

mine is developed by means of an incline about 420

feet deep at an angle of 44°. From this incline four

short levels are turned 100, 130, 170, and 290 feet below

the collar. Probably the total workings of the mine

do not exceed 2,000 feet.

The mine is in the Oquirrh formation about 2,500

feet stratigraphically higher than the" Galena King"

limestone, hence about 7,500 feet above t.he base of the

formation. Many of the workings are in a limestone

about 15 feet thick called the "Larsen" limestone.

This bed strikes almost due east and dips 50°-70° N.

There is an irregular dike of porphyry in the mine,

trending almost east-west. It is considerably sliced by

faults, along with the inclosing sediments, so that its

normal attitude is uncertain, but its general dip is

steeply north. The country rock in the vicinity of this

dike is much shattered, and the principal breccia zones

trend east and about N. 30° E.

The ore bodies of the mine were appa·rently tabular

replacement deposits in the shattered footwall of the

dike, raking steeply to the east in depth. Both quartzite and limestone were mineralized, but the principal

sheets appear to have been in the limestone. Locally

the ore made against the footwall of the porphyry, but

it was in general ll; few feet below it. The ore bodies

were small, only locally exceeding 3 feet in thickness

and 15 feet in width. More commonly the pipes were

only 3 or 4 feet in width. Apparently none of the

stopes were more than 100 feet in pitch length.

The ore was oxidized to the lowest level of the mine,

although a few residual sulphides occurred almost to

the surface. The hypogene ore minerals recognized in

these residua are pyrite, chalcopyrite, galena, and

sphalerite in a gangue of calcite and quartz with a

little dolomite. Oxidation products, constituting the

ore as mined, include jarosite, plumbojarosite, cerusite,

malachite, anglesite, "limonite," and some gypsum

and melanterite.

The average tenor of the ore was about 38 per cent

of lead, 0.5 per cent of copper, and 13 ounces of silver

and about 70 cents in gold to the ton.

The Muscatine mine is in the NE. 74 sec. 30, T. 4 S.,

R. 4 W., in the gulch below the Calumet workings.

The mine was worked in the early days to a depth of

about 300 or 400 feet but had long been abandoned at

the time of this survey. Nothing is definitely known

of its production, but it was probably slight.

The mine is opened by several inclines, of which

the longest is about 350 feet long. It is situated in

the Oquirrh formation about 4,000 feet above the base.

The beds here strike N. 70° E. and dip 40°-45° N.

The ore apparently occurred in a partly marmarized

and silicified limestone, in association with several small masses of porphyry. The ore seems to

have occurred in northwestward-pitching shoots, in

some stopes above 30 feet wide, in others only 10 feet

wide. These shoots were commonly connected along

the strike by thin leads of mineralization. Jasperoid

and hornfels occur abundantly in the mine, and both

these varieties of rock are mineralized as well as the

marble. The limestone is much fractured and carries

stringers of sulphides; so also do the hornfels and

jasperoid. About 350 feet down the dip the stopes

cut off against a northwestward-trending fault, and

no prospecting appears to have been done farther

northeast.

The mine is somewhat different from the larger

number of mines in the district in the more conspicuous development of hO,rnfels with the ore. Pyrite,

sphalerite, and galena seem to be the dominant hypogene sulphides, and jarosite, cerusite, plumbojarosite,

and "limonite" are the common oxidation products.

The Salvation-Hercules mine is in the northeastern

part of the Rush Valley district, in the gulch above

the Ben Harrison mine, at an altitude of about 6,300

feet. It is reached by wagon road from Stockton,

about 3 miles away. The mine was located in the

early days of mining in the district, and little is

known of the production. It was probably small,

however, as the workings are not extensive and the

visible stopes are not large. At the time of this survey the mine was being operated in a small way by

lessees.

The mine is developed (see fig. 22) by means of an

adit about 1,200 feet long, from which a few winzes

and raises are turned. The mine is in the Oquirrh

formation, about 8,000 feet above the base. The beds

stand vertical or are overturned a few degrees to the

south. The strike is essentially east. The beds are

cut by a northeastward-trending porphyry dike along

which the first 50 feet of the adit is driven. The adit

then turns' west into the hanging wall of the dike

and follows a strong fissure and breccia zone, locally

called the Katherine fissure, for practically all its

length. Toward the face of the tunnel about 1 foot

of sheared porphyry occurs in the fissure. Thi~ fissure and breccia zone trends about N. 10° E. and dips

about 70° W. A few short winzes and raises follow

this zone below and above the adit level. About 500

feet from the portal the crosscut intersects a limestone bed along which a prospecting drift has been

run a short distance.

The ore bodies of the mine occurred as breccia fillings and replacement deposits in the quartzite walls

of the Katherine fissure. The stopes were small-
about 4 or 5 feet wide, a few tens of feet high, and

about 200 feet long. The ore was chiefly oxidized

and as mined consisted of cerusite, plumbojarosite,

cerargyrite, malachite, jarosite, and limonite, with

residual fragments of the hypogene pyrite, galena, and

chalcopyrite that were originally deposited.

~

Limestone

Sandy limestone

-~

Quartzite

:~;~lt;~

Brecciated quartzite

1:~~~r;51~1

Porphyrj

--r

Dip of overturned bed

f

Fault.

FIGURE22.-Map of the Salvation-Her·

cules mine, Stockton district

The tenor of the ore mined in recent years is about

16 per cent of lead, 20 ounces of silver and 30 cents

in gold to the ton, and a little copper.

SOUTHPORT

The Southport mine is in the NW. % sec. 19, T. 4

S., R. 4 W., about a qli'arter of a mile north of the

portal of the 600-foot level of the Honerine mine. It

is reached by wagon road from Stockton and has been

connected on the drain-tunnel level with the main

Honerine workings. The mine was developed in the

early days of the district and made a small production at that time. Since then it had been worked in

only a sporadic manner until the World War. It was

then active until 1920, but since then no production

had been reported to the end of 1927. At the time

of this survey the property was dismantled. Its total

production was probably less than $30,000.

The shaft collar of the mine is on the outcrop of

the" Paisley" limestone, and presumably the workings are chiefly in this member, but as they were inaccessible at the time of this survey no definite statement c"anbe made.

The ore mined during the most recent activity of

the mine averaged about 15.5 per cent of lead, 0.7 per

cent of copper, and 5 ounces of silver and 40 cents in

gold to the ton.

The Tiptop mine is just northeast of the Honerine

air shaft, near the middle of sec. 19, T. 4 S., R. 4 W.

The Cyc.lone and Tiptop claims are included in the

property. It is reached bya wagon road from Stockton, a distance of about 11jz miles, but was being

worked at the time of this survey through the drain

tunnel of the Honerine mine, with which it is connected by a crosscut about 400 feet long. The mine

was not actively worked until recent years, although

it had been prospected in a small way for some time.

At the time of this survey it was being energetically

developed under the ownership of the Stockton Lead

Co. The period of notable production of the mine

dates only from 1924. Probably somewhat over

$300,000had been produced to the end of 1927.

The mine is developed by a few short drifts and a

winze about 900 feet deep, which extends to a depth

11 bout 120 feet below the drain-tunnel level of the

Honerine mine. Probably the total development

workings of the mine do not exceed 2,000feet, exclusive

of the stopes. (See pI. 32.)

The mine is almost entirely in the "Galena King"

limestone in the Oquirrh formation, which at the surface dips about 600 N. and strikes about east. In

depth, however, a prominent "bedding roll" occurs,

so that on the drain-tunnel level the beds strike almost

due north. The principal ore shoot of the mine occurs

on this bedding roll, in association with a fissure. The

ore body at the drain-tunnel level is over 100 feet long

and 8 or 10 feet high. The shoot continues at least to

the 700-foot level and pos8ibly to the surface, as does

the one about 250 feet east which was followed by the

winze from the surface. At the time of this survey

active work was being carried on in a drift 120 feet

below the drain-tunnel level on the "Galena King"

limestone west of the winze.
The ore of the Tiptop mine is like that of the stratigraphically lower beds mined in the Honerine and consists of galena, sphalerite, pyrite, and chalcopyrite as

primary minerals. Oxidation has occurred about to

the 700-foot level.

The average tenor of the ore mined is about 12 per

cent of lead, 0.25 per cent of copper, and 4 ounces of

~ilver and 80 cents in gold to the ton. Owing to the

persistence of the ore shoots and the fact that the

mine is drained by the Honerine tunnel, so that there

are no pumping costs, the property was regarded at

the time of this survey as unusually profitable. Neither

of the ore shoots had been bottomed at 900 feet below

the surface.

The Marjorie prospect, the property of the Soldier

Danyon Lead-Silver Mining Co., is in the north side

of Soldier Canyon about a quarter of a mile from the

mouth. At the time of this survey, in 1927, the

developments consisted of a prospecting tunnel about

420 feet long, driven in a N. 10° W. direction from a

point about 100 feet above the creek. Throughout its

length the tunnel is in the Manning Canyon shale,

which strikes N. '/00 W. and dips 45° NE. No evidence of mineralization was observed in the tunnel,

although, according to John Dorius, secretary of the

company, good assays have been reported on samples

from the surface.

WEST CANYON AREA

MAYFLOWER

The Mayflower mine is in West Canyon, just above

the mouth of Fox Hollow. It is reported to have

produced a small amount of ore in the early days of

mining in the State, but no record of such production

is available.

The old mine was largely caved and full of water at

the time of this survey, and the accessible workings

I consisted only of a few score feet of rather tortuous

drifts in the altered limestone of the lower part of the

Oquirrh formatioo. The limestone, which is only a

few hundred feet above the base of the Oquirrh formation, has been partly altered to lime hornfels, silicified, and impregnated with pyrite, a little galena,

sphalerite, and boulangerite. The sulphides are

chiefly distributed along narrow veinlets in the hornfels. The tenor of the ore in sight at the time of this

survey was not high, but precise information is not

available.
Ackno~ledglllents _

Actinolite, occurrence oL _

Adllliral De~ey lIline, description oL _

Adularia. See Orthoclase.

Albite, occurrence oL_____________________________________ 12\1

AIluviulll, occurrence o!-___________________________________ 40

Altitude of the area______________________________________ 3

Analcite, occurrence o!- 129

Analyses of rocks and ore 45-48,66-68,96,104,110,114,133-134

Andesite, analyses oL 46,47,66,67-68

Andesite or latite, occurrence and character o!- 41-42,

43-44, 61-62, pI. 8

Andradite, occurrence oL__________________________________ 129

Angleslte, occurrence of ~_________ 131

Anna clailll, location o!-___________________________________ 144

Antelope and Mountain Gelll IIllnes, production oL____________ 121

Antigorite, occurrence oL__________________________________ 130

Antllllony, occurrence and character of ores contalnlng________ 135

Apatite, occurrence ot_____________________________________ 130

Apophyllite, occurrence oL________________________________ 129

Aragonite, occurrence oL__________________________________ 128

Argent lIline, description o!- 156-157

Argentite, occurrence of___________________________________ 127

Argentojarosite, occurrence oL_____________________________ 132

Arsenates, occurrence o!-_________________________________ 130

Arsenic, occurrence and character of ores containing__________ 135

Arsenides, occurrence oL__________________________________ 127

Arsenopyrite, occurrence o!-__ 127

Augite, occurrence o!- ~__________ 129

Aurichalclte, occurrence oL_______________________________ 128

Azurite, occurrence o!-____________________________________ 128

B

Baltic 1IllII, location oL___________________________________ 146

Bannock clallll, location of________________________________ 148

Barite, lIlicrophotographs showing pIs. 16, 18, 19, B

occurrence of ~______ 131

Bartlett clallll, location of________________________________ 148

Basalt, character and distribution oL_______________________ 48

Basin Range fault systelll, age o!- 85-86

cause of_____________________________________________ 86-88

features of 81-85

Beeson, J. J., quoted______________________________________ 72

Beidellite, occurrence oL ----------------- 130

Ben Harrison IIllne, description and lIlap oL 157-159

Beudantite, occurrence oL_________________________________ 131

Bibliography ___ ____ _ ___ _______ ___ 4-6

Binghalll syncline, features oL 70-71

Biotite, occurrence o!-____________________________________ 130

•• Bird's-eye" porphyry, lIletalllorphislll oL__________________ 93

occurrence and character of 49-50

Block faulting, features oL 86-88

Bluebird type of dololllite, correlation oL 16,17

specllllen of pI. 6, B

Bonneville, Lake, deposits oL______________________________ 3,40

relic oL 40,117

Bornite, occurrence oL____________________________________ 127

Boulangerite, occnrrence of________________________________ 127

Bowlllan lilllestone, age and correlation oL__________________ 15

character and distribution oL__________________________ 14-15

lIletalllorphism oL 95-96, pI. 5, B

section of, on Lynch Ridge 14-15

specllllens of pI. 5

Breccias, of South Mountain, features of 41-42, pl. 8, A, B

of Traverse MoiIntains 43-45, pI. 9, A

Brooklyn lIline, description and lIlap of 151-152

Buckhorn lIline, location and features oL 121, 143

Buffalo lIline, description oL 139-140

Burnett clailll, location oL________________________________ 148

Butler, B. S., quoted -'__ 132-134

Butterfield Canyon, rocks oL_______________________________ 57

Page

4

129

143

Page

Calallline, occurrence oL__________________________________ 129

Calcite, occurrence oL ~_'-_'_______ 128

Caliche, occurrence oL____________________________________ 40

California lIline, ore oL___________________________________ 121

Calumet lIline, description oL______________________________ 159

Call1brian systelll, character and distribution oL_____________ 7-17

fossils in rocks o!- 11-12, 13, 15, 17

general relations of, in western Utah 18, 19

Calllp Floyd (Mercur) district, history and production oL 122-127 lIlines of 137-139

Canyon fault, description oL 74-75

Carbon, association with gold In Mercur ores________________ 134

general occurrence oL_________________________________ 127

photolllicrograph showing quartz crystal outlined by pI. 15, A

Carbonates, occurrence o!-_________________________________ 128

Carboniferous systelll, character and distribution oL 22-38

correlation of, in western Utah 38-39, pI. 7

fossils In rocks oL 23-24,26,28,30-31,33-34,36-37

Cedar Valley, alluvial deposits oL__________________________ 40

Cerargyrite, occurrence oL________________________________ 127

Cerusite, occurrence oL___________________________________ 128

Chalcanthite, occurrence o!-_______________________________ 131

Chalcedony, colloforlll structures in, lIlicrophotograph showlng_ pI. 17, B

occurrence ot_________________________________________ 128

Chalcocite, occurrence oL__________________________________ 127

Chalcopyrite, occurrence 01-_______________________________ 127

Chicago lIline, description oL 144-146

lIlap of workings oL pI. 27

Chloride Point mine, description oL________________________ 140 map of workings of p1.25

Chlorite, occurrence oL___________________________________ 130

Chrysocolla, occurrence oL_________________________________ 130

Cinnabar, occurrence of 127,134-135

Cirque lakes, occurrence oL________________________________ 40

Cliff fault, geologic relations oL 75, 77-78, 148-151

Cliff lIline, description of 143-144

lIlap of workings of___________________________________ pI. 27

Clilllate of the area_______________________________________ 3

Clinozoisite, occurrence o!-________________________________ 129

Colloidal silica, occurrence oL 99-101

Collophanlte, occurrence oL________________________________ 130

Columbia clailll, location oL_______________________________ 144

COllllllodore lIline, location of_______________________________ 152

Conglolllerate, Tertiary 39-40

Consolidated Mercur lIlines, description oL 137-138

ore of, analysis oL___________________________________ 134

sUllllllary of ore and tailings treated aL_______________ 125

Cooley clailll, location oL__________________________________ 148

Copper, occurrence and character of ores contalning 136-137

Corbon fault, relations oL 78-81, 153-154, pI. 11

Corning claim, location o!-_________________________________ 143

CovelIite, occurrence oL___________________________________ 127

Cuprite, occurrence oL____________________________________ 128

Cyclone clailll, location o!-_________________________________ 164

Dacite, analyses oL 47,48,68

DahlIite, occurrence oL___________________________________ 130

Daisy lIline, description oL________________________________ 139

Deseret lilllestone, age, correlation, and fossils oL____________ 26

character and distribution oL_________________________ 25

section of, on north side of Ophir Creek_________________ 25

Deseret lIline, description oL_______________________________ 152

Devonian sy~telll, character and distribution oL 20-22

fossils In rocks oL___________________________________ 21

unconformity below 18

Dike of Step Mountain 61-62,pl.10

Diopslde, occurrence oL___________________________________ 129

Diorite, analyses oL 67-68

167
Page

Dolomite, alteration of limestone to ~------------ 110-111

analyses of 96, 110

JeO'erson (1), description oL 20-22

Lynch, description oL 16-17

mineralogic relations oL______________________________ 128

specimen oL pI. 24

Douglas mine, location and features oL______________________ 141

Drainage of the area_____________________________________ 2-3

Dry Canyon area, faulting in 78-81, 83-84

geologic map oL_____________________________________ pI. 13

mines 01 121, 151-156

views in pIs. 1,2

Eagle Hlll rhyolite, description oL 58-59

East Canyon, Dlines of 120-121

East Side mine, location and features oL 140-141

Eighth of January claim, location oL______________________ 143

Empire Dline, location and features oL 140-141

Dlap of workings oL .___________________________ pI. 25

EDlporia mine, production oL______________________________ 121

Epidesmine, occurrence oL________________________________ 130

Epidote, occurrence oL____________________________________ 129

Eureka-Ophir Dline, description oL_________________________ 152

JiJxchange and Sunnyside mines, production oL_______________ 120

•• Eye bed" of J eO'erson (1) dolomite, characteristics oL_ 20, pl. 6, A

F

Fanglomerate, occurrence oL_______________________________ 40

Faults in the area, age of 77-78,80,85-86,88, 89-90

causes of 78,80-81,86-88

features of 6,74-90

Field work in the area ~____________ 4

Fissure deposits, occurrence and character oL_ 102-107, 110, 135, 137

Fluorite, occurrence oL___________________________________ 128

Folding in the area, date oL______________________________ 73

features of 6,69-71

regional relations oL 71-73

Foothill area, mine~ oL___________________________________ 142

Fourth of July mine, production oL_________________________ 121

Franklln lease. See Geyser-Marion Dline.

G

Galena, occurrence of_____________________________________ 127

Galena King Dllne, description oL 159-160

maps and sections oL pIs. 30-32

Garber fault, relations of 78-80, 154, pI. 11

Gem fissure, location oL___________________________________ 147

Geologic history of the area, sumDlary oL 90-92

Geologic map and sections of the StocktOn and Fairfield quadrangles______________________________________ pI. 12

Geyser-Marion mine, description oL________________________ - 138

Girty, G. H., fossils identified by 23-24,26,28,30-31,33-34,36-3'

Glaciation, evidences oL 40-41

Goethite, occurrence oL___________________________________ 128

Gold, location and character of deposits oL 127, 132-135

Golden Gate Ore, analysis oL 133-134

Granite, analysis oL 67~8

Granodiorite, analyses oL 67-68

Great Basin claim, early history 01'_________________________ 118

"Great Blue" liDlestone, age, correlation, and fossils oL 30-31

character and distribution oL ---- 29

faUlting of, sections showing___________________________ 82

jasperoid In 97-101

metamorphism_ _______ _ __________ __ ___ _ _ 96

Green Eyed Monster fissnre, location oL____________________ 147

Grossularlte, occurrence oL________________________________ 129

Gypsum, occurrence of____________________________________ 131

H

Halloysite, occurrence oL_________________________________ 130

Haloids, occurrence oL 127-128

Hartmann liDlestone, age and correlation oL 13-14

character and distribution oL 12-13

metaDlorphisDl In_____________________________________ 96

section of, near Wild DeliriuDl Dllne____________________ 13

specimens oL pI. 4

Hedenbergite, occurrence oL_______________________________ 129

Heikes, V. C., quoted 117-127

HeDlatlte, occurrence oL__________________________________ 128

Hercules claiDl, location oL_______________________________ 144

Hidden Treasure mine, description oL 144-146

map of workings oL pI. 27

ores of 116-117

Page

" Honerine" liDlestone, analysis oL________________________ 96

metamorphism in_____________________________________ 94

Honerine Dllne, description oL 118-119, 160-162

map of workings oL pl. 31

Hornblende, occurrence oL________________________________ 129

Hornblende-hypersthene andesite or latlte breccia of South

~ountain 41-42,pI.8,A,B

Horn~els, occurrence and character oL 95, 101-107

paragenesis during metaDlorphism 107-108

speciDlens oL pIs. 20-23

HUDlbug formation, age, correlation, and fossils oL__________ 28

character and distribution oL 26-28

deposition oL 28-29

section of, on north wall of Ophir Canyon 27-28

Huntley, D. R, quoted 141,155

Hydrozincite, occurrence oL_______________________________ 128

Hypersthene, OCCurrence oL_______________________________ 129

I. X. L. and ~ount Savage mines, production oL____________ 121

Iddingsite, occurrence oL_________________________________ 130

Igneous rocks, age oL 64~6

general character and distribution oL 41-48

geologic relations oL 64~6

petrologic relations oL 66-67

regional relations oL 67~9

sumDlary of history oL_______________________________ 69

Indians, Dletal obtained by_________________________________ 120

Industries of the area_____________________________________ 3

Intrusive rocks, age oL 64-66

character and distribution oL 48-64

deforDlation of country rock by_________________________ 54

structural relations oL 54, 57-58

Iron mIne, location and features oL 140-141

Jarosite, occurrence oL___________________________________ 131

Jasperoid, character oL___________________________________ 98

distribution and general relations oL 97-98

hypogene minerals detected In__________________________ 99

microphotographs of specimens oL pIs. 14-19

origin oL .: 99-101

JeO'erson (1) dolomite, age and correlation oL 21-22

character and distribution oL__________________________ 20

section of, on spur east of CllO' mlne___________________ 20

specimen oL pI. 6, A

Jim Fisk mine, de8criptlon and map of 146-148

Kaolinite, occurrence oL__________________________________ 130

Kearsarge mine, description, plan, and section oL 152-153

Kersantite, occurrence oL 63~4

Kirk, Edwin, fossils identified by 21

La Cigale mine, description oL____________________________ 139

Lacustrine deposit., occurrence oL_________________________ 40

Lake Bonneville, deposits oL_______________________________ 3,40

relic of 40,117

Lakes of KlIlarney fault, description oL_____________________ 83

Lakes of Killarney Dllne, description and plan oL___________ 142

ore bodies of_________________________________________ 136

Lampl'ophyre dikes. occurrence and character oL 63-64

Latite, analyses oL 45,46,47,66,68

occurrence and character oL 45-46, 61~2, pl. 9, A

See also Andesite or latlte; Quartz latite.

Lead, occurrence and character of ores of 135-137

Lime silicates, occurrence oL - 101-108

Limestones, alteration to dolomite 110-111

alteration to llme silicates and accoDlpanylng sUlphldes __ 101-108

alteration to sulphide ores and accompanying gangue 108-110

analyses showing metamorphism In 104, 113

BowDlan, description oL 14-15

Deseret, description oL 25-26

•• Great Blue," description oL 29-31

Hartmann, description oL 12-14

Madison, description oL 22-25

DlarDlarizatlon oL____________________________________ 97

of Humbug forDlatlon 27-29

of Oquirrh formation 34-38

sillcification oL 97-101
Page

Lion Hill, ore deposits oL 135-136

rocks of ~ 49-50

strncture in pl.3,B

Lion Hill area, mines oL 139-142

mines of, map of workings oL_________________________ pI. 25

Lion HllI fault, description oL 75-76

Lion mine, location and features oL________________________ 141

Liparite, analyses oL 47,48

Location of the area______________________________________ 1-2

Long Ridge anticllne, features oL 70, pI. 3, ALong Trail shale member of ••Great Blue" limestone 29-30

Lost Boy claim, location oL_______________________________ 148

Loughlln, G. F., quoted 116-117

Lynch dolomite, age and correlation oL______________________ 17

character and distribution oL 16-17

section of, east o~ Cliff mine 16-17

specimens oL pI. 6, B, C

23-25

22-23

23-24

23

132

128

153

128

135

150

32-34

31-32

33-34

32

Madison limestone, age and correlation oL ~ _

character and distribution oL _

fossils oL _

section of, east of Buckhorn mine _

Magazine vein, features oL _

Magnetite, occurrence oL _

Magnolia mine, description oL _

Malachite, occurrence oL ~ _

Manganese, occurrence and character of ores containing _

produced during the World Wal'- _

Manning Canyon shale, age and correlation oL _

character and distribution oL _

fossils oL _

section of, in Soldier Canyon _

Marion mine. See Geyser-Marion mine.

Marjorie prospect, description oL__________________________ 165

Mark Antony fault, relations oL 78-80, 154, pI. 11

Marmarization of limestone '-__________ 97

Maud S. claim, location oL________________________________ 148

Maytlower mine, description oL____________________________ 165

Melaconite, occurrence oL_________________________________ 128

Melanterite, occurrence oL________________________________ 131

Mercur area, mines oL 137-138

mining history oL 122-127

ore deposits in 135-136

Mercur Canyon, fault south oL____________________________ 81

Mercur mine. See Consolidated Mercur mines.

Mercur vein, features oL__________________________________ 132

Mercury, occurrence oL 134-135

production oL_______________________________________ 138

Metals, production oL 119, 122, 124

Metamorphism, dynamic___________________________________ 92

igneous 93-115

agents of 111-112

solutions effecting 114-115

theory of 111-115

transfer of material during - 112-114

of tne limestones 96-111

of the quartzites, sandstones, and shales 94-96

paragenesis durlng 107-108, 109-110

susceptibility of rocks to 97-98, 101, 108-109

Microcline, occurrence oL_________________________________ 129

Middle Canyon, rocks of 54-55

Mimetite, occnrrence oL___________________________________ 130

Mineralization, zonal theory oL____________________________ 115

Minerals, alteration and replacement of, during metamorphism,

general features oL 93,97, 100, 109

alteration and replacement of, during weathering______ 116-117

found in the area, llst oL 127-132

paragenetlc relations of, in hornfels ~__ 107-108

in SUlphide ores 108-110

transfer of, during metamorphism of limestone 112-114

Miner's Delight claim, location and features oL 120,148-149

Mines, lists oL 120,121, 123, pi: 12

Mining, history oL 117-127

Mississippian and Pennsylvanian series, character and distribu- tion of 31-34

Mississippian series, character and distribution oL 22-31

correlation of________________________________________ pI. 7

unconformity llelow___________________________________ 22

Monarch mine, location and features oL 140-141

map of workings oL__________________________________ pI. 25

Mono fault block, description oL 78-80

diagram oL__________________________________________ pl. 11

Page

Mono mine, description oL 153-155

map of workings oL__________________________________ pI. 29

Montana mine, location oL________________________________ 148

Montmorillonite, occurrence oL____________________________ 130

Monzonite, analyses oL -.: 66,67-68

Monzonite and related rocks, character and distribution oL 49-58

Moraines, occurrence oL___________________________________ 41

Mount Savage and 1. X. L. mines, production oL_____________ 121

Mountain Gem and Antelope mines, production oL____________ 121

Mountain Tiger claim, location and features of______________ 141

Muerbrook fault, relations oL 84,85,89

Muerbrook mine, description of "- 162-163

Muscatine limestone, description oL ~___________________ 163

Muscovite, occurrence of 130

129

129

48

62-63

Natrolite, occurrence oL _

Nephelite, occurrence oL _

Nephellte basalt, tlow of _

sills of _

New Stockton mine. See Ben Harrison mine.

Nontronite, occurrence oL _

Norma mine. See Daisy mine.

Northern Light mine (Lion Hill area), location oL 140-141

map of workings oL__________________________________ pI. 25

Northern Light mine (Ophir HIlI Consolidated), location of___ 148

Oak Spring Canyon, view at head oL pI. 9, AObsidian, character and distribution oL 47-48

Olivine, occurrence oL____________________________________ 129

Olivine basalt, character and distribution oL ~ 44, 48

Opal, occurrence oL ~___________________________ 128

Ophir anticline, features oL 69-70, pI. 3, B

Ophir Coalition mine, description oL_______________________ 148

Ophir district, geologic map oL___________________________ pI. 13

history and production of 120-122

IIllnes of___________________________________________ 139-156

Ophir formation, age, correlation, and fossils oL 11-12

character and distribution oL_________________________ 9-10

metamorphism in 95-96

section of, at Ophi"-__________________________________ 10

Ophir Hill, view oL______________________________________ pI. 2

Ophir Hill area, mines oL 143-151

Ophir HIlI Consolidated mine, description oL 148-151

stope map and sections of ore bodies oL pl. 28

Ophir Queen prospect, location oL_________________________ 151

Ophir-Silverado fault area, features oL 74--78

Oquirrh formation, age and correlation oL 36-38

character and distribution oL 34-36

deposition of_________________________________________ 38

~ossils of 36-37

metamorphism In 94, 96, 101-102

sections oL 35, 161

Oquirrh Mountains, location and general features oL 2-3,6

views in pis. 1-3

Ore deposits, bedded 132-137

classltlcatlon oL_____________________________________ 132

descriptions oL 132-137

tlssure 102-107, 110, 135, 137

gold and gOld-mercury 132-135

lead-sllver-zinc-copper 136-137

origin of, through igneous metamorphism 111-115

through weatherlng 115-117

replacemenL 108-110, 132-137

section of, in the Mercur district_______________________ 133

silver and silver-Iead 135-136

zonal theory of mlneralization_________________________ 115

Ores, analyses of 144, 133-134

treated at Consolidated Mercur Mines Coo's mill, 1901-12__ 125

Orpiment, occurrence oL__________________________________ 127

Orthoclase, occurrence oL_________________________________ 129

Our Boy's claim, location oL______________________________ 148

Overland mines, description oL____________________________ 138

Oxides, occurrence oL____________________________________ 128

Palace fault, displacement oL _

Pallgorskite, occurrence oL _

Pennsylvanian series, character and distribution oL_--------

correia tion oL - -- - -- - - -- - - -- -- ---

Pharmacoslderlte, occurrence oL _

89

130

34--38

pI. 7

131
PhlIIipsite, occurrence oL _

Phosphates, occurrence oL _

Physical features of the area _

Plagioclase feldspars, occurrence oL _

Plumbojarosite, occurrence oL _

Pole Canyon syncline, features oL _

Poorman mine, location of _

Porphyry Knob, rocks oL _

Precipitation in the area _

Psilomelane, occurrence oL _

Pyrite, occurrence oL _

Pyrolusite, occurrence oL _

Pyromorphite, occurrence of _

Pyrrhotite, occurrence oL _

Page

129

130

2-3

129

131

70

121

49-50

3

128

127

128

130

127

,'st

Quartz, general occurrence oL_____________________________ _ ~8

in jasperoid 97-101

microphotographs showing pis. 14-19

Quartz latite, character and distribution oL 46-47

Quartz monzonite, character and distribution oL 50,53

Quartzites, metamorphism oL______________________________ 94

of Humbug formation, description oL 27-29

of Oquirrh formation, description oL 34-38

Tintic, description oL_________________________________ 7-9

Quaternary system, features oL 40-41

Queen of the Hills mine, description oL_____________________ 155

R

••Raddatz" porphyry 52,53

Realgar, occurrence oL____________________________________ 127

Red Pine claim, location oL ---------- 144

Replacement deposits, occurrence and character oL_ 108--110,132-137

Resser, C. E., fossils identified by 11, 13, 15, 17

RhYOlite, analysis oL_____________________________________ 68

character and distribution oL 58-61

Rhyolite obsidian, character and distribution oL 47-48

Rocks, alteration of, by dynamic metamorphism-------------- 92-93

alteration of, by igneous metamorphism 93-115

by weathering 115-117

analyses of 45-48, 66-68,96,104,110

R.)ckwell claim, location and features oL____________________ 141

Rush Lake, history oL 117-118

Rush Valley, alluvial deposits oL__________________________ 40

Rush Valley (Stockton) district, history oL 117-119

mines of 156-165

organization of_______________________________________ 118

production from______________________________________ 119

Rutile, occurrence oL_____________________________________ 128

Sacramento mine (Mercur area), description oL_____________ 138

map of workings oL__________________________________ pI. 26

Sacramento mine (Ophir district), description oL 144-146

map of workings oL__________________________________ pI. 27

••St. Patrick" limestone, metamorphism in__________________ 94

Salvation-Hercules mine, description and map oL 163-164

Sandstones, metamorphism oL_____________________________ 94

of Humbug formation, description oL 27-29

of Oquirrh formation, description oL 34-38

San Joaquin mine, location and features oL 121, 147

Scapolite, occurrence oL__________________________________ 129

Scorodite, occurrence oL__________________________________ 131

Sedimentary rocks, general section oL______________________ 6-7

Sepiolite, occurrence oL___________________________________ 130

Serpentine, occurrence oL ~_________ 130

Settlement Canyon, rocks oL 54-55

Severe claim, location oL__________________________________ 148

Shaggy Peak rhyolite, description oL 59-60

Shales, in ••Great Blue" limestone, features oL 29-30

Manning Canyon, description of 31-34

metamorphism of 94-96

of Ophir formation, description oL_____________________ 9-12

Sharp Mountain, faults on '-_________ 80

Siderite, occurrence oL___________________________________ 128

Silica, colloidal, occurrence of 99-101

Silicates, occurrence oL 128--130

Silication of llmestonc- 101-108

Silicification of limestone 97-101

Silver, occurrence and character of ores oL 127, 135-137

Silver Chief claim, location and features oL_________________ 141

Silver King claim, location oL____________________________ 159

Page

"Silver ledge," location and features oL ---_________ 132

Smithsonite, occurrence oL________________________________ 128

Soldier Canyon, rocks oL 50-52

Soldier Canyon area, mines oL____________________________ 165

Soldier Canyon fault, description oL_______________________ 84

South Mountain, volcanic rocks oL 41-42, pI. 8, .Ii.

Southport mine, description oL '- 164

Sparrow hawk mine, analysis of ore oL______________________ 114

Sphalerite, occurrence oL__________________________________ 127

Step Mountain, rocks oL 61-62, pI. 10

Stiblconite, occurrence oL_________________________________ 128

Stibnlte, occurrence oL____________________________________ 127

Stockton area, faulting in 88-90

mines of 156-165

mining history oL 117-119

rocks of_____________________________________________ 52-54

Structure in the area 69-90

Sulphantimonites, occurrence oL___________________________ 127

Sulpharsenites, occurrence oL______________________________ 127

Sulphates, occurrence oL________________________________ 131-132

Sulphides, list oL________________________________________ 127

occurrence of 101-110

specimens of rock containing pIs. 21-24

Sulphur, occurrence of____________________________________ 127

Summit claim, location oL________________________________ 144

Sunnyside and Exchange mines, production oL_______________ 120

Sunshine area, deposits oL________________________________ 135

lltines of 138-139

Sunshine mine, description oL 138--139

Surprise tunnel, description oL 155-156

map of______________________________________________ pI. 29

Talc, occurrence oL_______________________________________ 130

Talus deposits, occurrence oL 40, pI. 3, B, 0

Teller claim, location oL__________________________________ 148

Tennantite, occurrence oL________________________________ 127

Tertiary system, features oL 39-40

Tetrahedrite, occurrence oL_______________________________ 127

Thad Stevens mine, description oL_________________________ 156

Theresa claim, location oL________________________________ 159

Thomsonite, occurrence____________________________________ 129

Three Metals mine, description oL 141-142

Tlckville Gulch, rocks oL 47-48,55-57

Tickville rhyolite, description oL 60-61

Tintic quartzite, character and distribution of_______________ 7-9

correlation oL________________________________________ 8-9

Tiptop mine, description oL 164-165

projection of workings oL_____________________________ pI. 32

Titanite, occurrence oL___________________________________ 130

Titanosilicate, occurrence oL_______________________________ 130

Tomahawk claim, location of_______________________________ 143

'L'ooele Valley, alluvial deposits oL_________________________ 40

Topaz, occurrence of '- 129

Topography of the area 2-3,pls.1-3,9, 10

Tourmaline, occurrence oL________________________________ 129

Trachyte, analyses of______________________________________ 45

in the Traverse ~fountains 41,44

Trafalgar claim, location oL_______________________________ 143

~'ransportation in the area_________________________________ 2

Traverse Mountains, general field relations of 42-43

petrologic features oL________________________________ 43

Tremolite, occurrence oL__________________________________ 129

Tridymite, occurrence oL__________________________________ 128

Tuffs, occurrence and character oL 41, 45, pI. 8, B, 0

Uinta axis, supposed extension of, through Bingham _

Unconformities, pre-Middle Devonian _

pre·Mississippian - - - _

Utah Queen mine, description oL _

71-73

18-20

22

156

Vanadates, occurrence oL__________________________________ 130

Vegetation of the area_____________________________________ 3

Vesuvianlte, occurrenCe oL________________________________ 129

Volcanic plug at Step Mountain 61-62, pI. 10

Volcanic rocks, age oL 64-66

character and distribution oL 41-48

source of____________________________________________ 65
Page

Wad, occurrence oL_______________________________________ 128

Walcott, C. D., clted______________________________________ I I

Wandering Jew mine, features oL__________________________ 121

Weathering, of the jasperold_______________________________ 116

of the lime sl11cate and sulphide bodles 116-117

of the nonmetamorphlc rocks___________________________ 115

West Canyon, basalt fiow In_______________________________ 48

West Canyon area, mines oL_______________________________ 165

West Dip area, mines of__________________________________ 139

West Mercur area, mines oL______________________________ 139

Wl'st Mercur fault, description and diagrams oL 81-83

view of scarp oL pl. 9, B

Page

West Mountain district, mines oL_________________________ 165

Wild Delirium claim, location and· features oL 148-149

Wollastonite, occurrence oL_______________________________ 129

Woodruff mine, location and features oL 140-141

Wurtzlte, occurrence of____________________________________ 127

"Zebra rOCk," occurrence oL 10-11

ZelIa mine, location and features oL________________________ 141

Zeolites, occurrence oL ._____________________ 93

Zinc, occurrence and character of ores containlng 135-137

Zircon, occurrence oL_____________________________________ 129

Zolsite, occurrence oL_____________________________________ 129