Sevier-age Thrust Fault 

Structures Control the 

Location of Base- and 

Precious-Metal Mining 

Districts in the Oquirrh 

Mountains, Utah

by Edwin W. looker1 

Open-File Report 98-234 

1998

This report is preliminary and has not been reviewed for conformity with 

U.S. Geological Survey editorial standards or with the North American 

Stratigraphic Code. Any use of trade, firm, or product names is for 

descriptive purposes only and does not imply endorsement by the U.S. 

Government

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

Menlo Park, California
CONTENTS

Page 

Abstract............................................... ... 4

Introduction ..................................... ......... 5

Geologic Setting of North-Central Utah .......................... 7

Oquirrh Mountains Nappes .................................. ..11

Structural and Stratigraphic Characteristics of Mining Districts in

the Oquirrh Mountains ........................... ..14

Bingham (West Mountain) mining district ................ .14

Mercur (Camp Floyd) Mining District ..................... 20

Ophir Mining District.................................. .27

Stockton (Rush Valley) Mining District ................... 32

Barneys Canyon-Melco Mining Area ..................... 35

Conclusions ................................................ 39

Acknowledgments .......................................... .43

References Cited ............................................

.44

FIGURES

Figure Page

1. Location of the Oquirrh Mountains and its mining

districts in north-central Utah. ......................... 51

2. Foreland of the Sevier thrust belt, the trace of the

inferred Uinta trend basement lineament, and the location of 

figure 1 .... .......................................... 52

3. Location of nappes in the Oquirrh Mountains

and the distribution of igneous rocks. .................... 53

4. Inferred sequence and direction of movement of the nappes 

that constitute the present Oquirrh Mountains and the 

inferred location of a basement promontory along the Uinta 

trend. ................................................ 54

5. Principal structures in the thinned wedge-margin of a nappe

emplaced against a basement buttress ................... .55

6 Surface projections of disseminated-porphyry, vein and

replacement, skarn, and placer ore bodies in the Bingham 

mining district ........................................ .56

7. Columnar Stratigraphic sections of comparable parts of the

South Mountain and Bingham nappes in the Stockton 7 1/2- 

minute quadrangle. . .................................. .57

8. Principal fold and fault structures of the Bingham mining

district, Utah. ............ . ........................... 58
9. Locations of the Mercur, Ophir, and Stockton mining districts in

the southern Oquirrh Mountains. ........................ 59

10 Fold and fault structures in the Mercur mining district

area ................................................ 60

11. Fold and fault structures in the Ophir mining district ....... .61

12. Fold and fault structures in the Stockton mining district area. .62

13. Fold and fault structures in the Barneys Canyon-Melco mining

area ................................................. 63

TABLES

Table Page

1. Characteristic identifying features of Oquirrh Mountain

nappes ............................................... .64

2. Metal production from the Oquirrh Mountains mining districts

Utah ............................. ................ ... 65

3. Geologic types and ages of intrusive rocks in the mining district 

areas in the Oquirrh Mountains. ........................ 66
Sevier-age Thrust Fault Structures Control of the

Location of Base- and Precious-Metal Mining Districts

in the Oquirrh Mountains, Utah

By Edwin W. Tooker

ABSTRACT

The Oquirrh Mountains lie immediately west of Salt Lake City, 

Utah, and are part of a geologically complex Paleozoic foreland 

terrane of the north-northeast-trending Late Cretaceous Sevier 

thrust belt in central Utah. The range is the site of four historic 

base- and precious-metal mining districts and a newly recognized 

disseminated-gold mining area. The mineralized and intruded areas 

in the Oquirrh Mountains nappes overlie the Uinta trend, an easterly 

directed, intermittently active, locally uplifted fracture zone, which is 

inferred to overlie a basement tectonic lineament of regional extent. 

The mining districts are spatially associated with Tertiary igneous 

rocks intruded along the extension of the trend in the Oquirrh 

Mountains. Further, most of the mining districts seem to be located 

on or near the leading margins of folded, faulted, and thinned upperplate wedges of thrust faults that moved from different parts of the 

Sevier hinterland. They converged onto a buttress formed by an 

uplifted part of the Uinta trend underlying the Oquirrh Mountains 

area.

The porphyry copper, skarn, and vein and replacement 

deposits at Bingham Canyon, which comprise the largest mining 

district in the range, are located in the Bingham nappe at the leading 

edge of the sole Midas thrust fault. The disseminated gold deposits 

in the Mercur mining district are located near the leading edge of the 

broken upper plate of the Manning thrust, an imbricate thrust fault 

within the Bingham nappe. The base- and precious-metal deposits in 

the Ophir mining district occur in the leading edge of the Manning 

(imbricate) thrust fault. Base- and precious-metal deposits in the
Stockton district are located in the South Mountain nappe at the 

leading edge of the Stockton thrust, which overrode the Bingham 

nappe. The Barneys Canyon and Melco disseminated gold deposits, 

considered to be part of the Bingham mining district by the mine 

operators, occur in the Pass Canyon nappe.

Stratigraphically similar but structurally distinctive nappes 1 

composed of Paleozoic clastic carbonate, siliceous, and argillaceous 

sequences of sedimentary rocks, were deformed during their 

emplacement in the Oquirrh Mountains by differentially directed 

thrust faults produced by the Late Cretaceous Sevier orogeny. The 

sedimentary rocks composing the nappes were re-faulted and 

uplifted locally by later Tertiary Basin-and-Range extensional 

deformation. Subsequently they were intruded by Tertiary quartz 

monzonite, granodiorite, latite, and rhyolite stocks, plugs, sills, and 

dikes and overlain locally by Tertiary latite flows and breccias. 

There are no known pre-Tertiary igneous rocks exposed.

During the late stages of Tertiary intrusion, metal-rich 

hydrothermal solutions mixed with meteoric water locally altered 

and replaced the sedimentary and igneous host rocks. Ore minerals 

were deposited in the fractured intrusives, in sedimentary rocks 

along faults initiated by the Sevier-age thrusts, and as replacements 

of carbonate strata adjoining these faults. The magnitude and tenor 

of mining districts are believed to be a function of their structural 

position, the style of deformation within host nappes, their proximity 

to the Uinta trend, and their spatial association with intrusive rocks.

INTRODUCTION

The north trending Oquirrh Mountains rise at the south end of 

Great Salt Lake, about 25 km west of Salt Lake City, Utah. They 

include a series of coalescing peaks about 55 km long and from 10 to

1 Nappe as used here is a sheetlike allochthonous rock unit of sedimentary 

origin that is moved by thrust faults.
25 km wide that rise from 4,200 ft at the Great Salt Lake to more 

than 10,500 ft at Lowe Peak in the southern part of the range (fig. 1). 

The Oquirrh Mountains are a part of the foreland of the Sevier thrust 

belt (fig. 2), which extends from Alaska to Mexico (Hayes, 1976). The 

structural and stratigraphic characteristics of nappes composing the 

thrust belt in central Utah were delineated by Roberts and others

(1965), Morris (1983), and Tooker (1983). The Oquirrh Mountains 

nappes are presumed to overlie a cratonal basement terrane that 

contains the Uinta-Cortez axis or Uinta trend (fig. 2), an east-trending 

mobile structural zone that facilitated intrusion of igneous rocks and 

their associated hydrothermal ore-bearing solutions from depth 

(Erickson, 1976).

FIGURES 1 and 2, NEAR HERE.

The co-location of ore deposits on the upper plates of thrust 

faults, while known, has seldom been observed on a mountain-range 

scale. James (1982) identified a number of ore deposits containing 

substantial amounts of high-grade base- and precious-metal ores 

localized along thrust faults in the Wasatch Mountains. These are 

generally small ore bodies within individual mines. Regional geologic 

mapping in the Oquirrh Mountains disclosed the direct association of 

regional thrust-fault-related structures with several large mining 

districts (Tooker, 1999).

Descriptions of the geologic terranes developed in the range 

during the Late Cretaceous Sevier Orogeny are based on observations 

by Tooker (1983, 1999), and Tooker and Roberts, (1998). 

Characteristics of Tertiary-age ore deposits contained in the Oquirrh 

Mountains are best described by others. Those at Bingham and 

Barneys Canyon-Melco were from reports by Peters and others

(1966), Rubright and Hart (1968), Atkinson and Einaudi (1978), 

Babcock and others (1995), and Presnell and Parry (1996). The 

deposits at Mercur were reported by Kornze and others (1985). 

Deposits in the Ophir and Stockton districts were described by Gilluly 

(1932).
7

Many authors of the individual geologic reports cited herein 

may not concur in whole or in part with my regionally-focused 

interpretation of the origin of the Oquirrh Mountains ore deposits. 

For example, a recent alternative interpretation of the origin of the 

structures and ore deposits in the Oquirrh Mountains was based on 

geochemical and geochronologic data by Wilson and Parry (1995) at 

Mercur, and the geologic-geochemical-geochronologic data of Presnell 

and Parry (1996) at the Barneys Canyon and Melco deposits. These 

data lead to their conclusions that are at variance with the author's, 

and are discussed later in the report. Final resolution of the 

problem of origin undoubtedly will require additional information.

GEOLOGIC SETTING OF NORTH-CENTRAL UTAH

t 

Observed and inferred geologic features indicative of a

sequential evolution of north-central Utah and the Oquirrh 

Mountains summarized here are more fully documented by Tooker 

(1999). These include (1) recognition of a Uinta-trend lineament and 

its impact on the accumulation of Paleozoic sedimentary rocks in two 

adjoining miogeoclinal basins on a west-facing Precambrian craton 

shelf, (2) compression of the region by Late Cretaceous Sevier thrust 

faults producing the nappes, (3) Basin and Range extensional faulting 

and uplift, (4) introduction of Tertiary intrusive and extrusive rocks, 

and accompanying hydrothermal deposition of the ore-forming 

materials, and (5) unroofing by Quaternary uplift, glaciation, and 

erosion.

A Precambrian craton terrane underlying north-central Utah is 

exposed in the Wasatch Mountains, but mostly is concealed to the 

west. These cratonal rocks formed a north-trending, west-dipping 

shelf of the North American continent during the Paleozoic. 

Basement rocks lying north of a generally west-striking fault zone 

along the north flank of the Uinta Mountains, compose the Archean 

Wyoming shield (King, 1976; Bryant, 1979, and 1988). Those south 

of the fault zone are composed predominantly of Proterozoic rocks
(Sears and others, 1982). This fault zone is believed to have deep 

seated structural significance both westward and to the east, and is 

coincident here with what is known as the Uinta trend. The 

generalized trace of the trend (fig. 2), and its westward projection 

were described by Webb, (1958), Roberts, and others (1965), and 

Erickson (1976). The trend is defined permissively by (1) an 

alignment of Cenozoic intrusive and extrusive rocks (Stewart and 

others, 1977; Moore and McKee, 1983; and John, 1989), (2) evidence 

of periodic uplift along parts of the trend in western Utah and 

eastern Nevada (Brooks, 1956; Webb, 1958; Roberts and Tooker, 

1969; and Coats, 1987), and (3) geophysical data (Stewart, 1978; 

Mabey and others, 1978; Eaton and others, 1978; and Bankey and 

Campbell, 1989). Sims and others (1987) described a possible 

eastward extension of the Uinta trend or a comparable mineralized 

lineament in the midcontinent, which they attributed to the accretion 

of a Proterozoic terrane onto an Archean shield.

Paleozoic sedimentary rocks were deposited on an irregular, 

broad, shallow, gradually subsiding craton shelf (Gordon and Duncan, 

1970; Stewart and Poole, 1974; and Peterson, 1977). The shelf was 

elongated generally north-south, and located an undetermined 

distance west of the autochthonous, nearer-shore, more slowlysubsiding part of the craton shelf presently exposed in the Wasatch 

Mountains (Baker and others, 1949; Crittenden and others, 1952; and 

Rose, 1967). Local intermittent uplifts along the Uinta trend in 

western Utah and eastern Nevada during the Paleozoic separated the 

deposition of shelf sediments into an Oquirrh basin on the south and 

the Sublette basin on the north (Peterson, 1977). Paleozoic 

sedimentary rocks exposed in the Oquirrh Mountains were deposited 

in different parts of these Sevier hinterland basins.

Studies in the hinterland area of northeastern Nevada and 

northwestern Utah by Camilleri and others (1994), Miller and Hoisch 

(1995), and Elison (1995), described relatively local igneous and 

metamorphic evidence for a Late Jurassic Elko orogeny. Jurassic 

orogenic activity was proposed as the source of illite clay mineral
dates in wall rocks adjoining the Mercur and Barneys Canyon-Melco 

disseminated gold deposits by Wilson and Parry (1995) and Presnell 

and Parry (1996). The author's conclusion of the limited significance 

of this orogeny with respect to the ore deposits in the Oquirrh 

Mountains is considered later in this report.

Five nappes composed of sedimentary rocks from these basins 

were thrust eastward in sequence and merged in the Oquirrh 

Mountains foreland (figs. 3 and 4) during the compressional phase of 

the Late Cretaceous Sevier orogeny (Price, 1989; Armstrong, 1968; 

Roberts and Crittenden, 1973; Tooker 1983; and Hamilton, 1988). 

Possible mechanisms for producing Sevier-age decollement thrust 

faults, whether by gravity slide proposed by Rubey and Hubbard 

(1959) or regional detachment driven by a heated magmatic arc in 

the hinterland and cooler foreland areas described by Allmendinger 

and Jordan (1981), are considered by Armstrong (1972), Roberts and 

Crittenden (1973), Hayes, 1976, Allmendinger and Jordan (1981), 

Allmendinger, and others (1983), and Hamilton (1988). The manner 

of thrust movement and the distance moved can not be determined 

in the Oquirrh Mountains. However, Crittenden (1961) estimated 

that some of the Utah nappes may have been transported eastward 

as much as 64 km.

FIGURES 3 and 4, NEAR HERE.

Sole and imbricate thrust faults and tear and conjugate normal 

faults observed on a thinned forward nappe margin were formed 

during its emplacement and folding. The sole thrust may have 

moved eastward an unknown but probably substantial distance. 

Through-going, symmetrical, broad, open, high-amplitude main folds 

were produced in the nappe. Generally wide-spaced conjugate 

normal, steep-dipping faults, which generally have only small 

displacement of stratigraphic units, also were formed (Tooker, 1999). 

At the same time, movement on imbricate thrusts within the nappe 

were of much less magnitude. Close-spaced secondary lowamplitude and discontinuous thrust-formed folds developed are
10

commonly cut off and offset modestly by steep-dipping short-length 

tear faults.

The structures observed in Oquirrh mining districts represent 

local variations in more highly-stressed parts of a main fold (fig. 5) 

at the thinned leading edge of the thrust. Local forward horizontal or 

vertical stretching, arching, and overturning of a main fold as the 

nappe rose and lapped obliquely over the Uinta trend buttress, 

resulted in formation of abundant local branching, close-spaced, 

nearly vertical tension faults normal to the fold axes. Tight, smallamplitude secondary folds formed along the frontal edges of thrust 

plates were separated by tear faults, and the broken upper part of 

the fold offset forward as a local imbricate thrust. Conjugate normal 

faults are also produced during the folding and subsequent uplift of 

that part of the nappe overlying the Uinta trend. Later, during 

Basin-and-Range extension, some of these tear and conjugate faults 

were displaced further as normal faults. The sequence of types of 

faults generated in the host sedimentary rocks overlying the Uinta 

trend is not always clear. Suffice to say, they provided the potential 

openings used subsequently in the introduction of magma and 

hydrothermal solutions (Field and Moore, 1971; Tooker and Roberts, 

1988, p. 7-8).

FIGURE 5, NEAR HERE.

During the Late Cenozoic, following the period of plate 

convergence and crustal compression of the Sevier orogeny, crustal 

extension produced Basin and Range block faulting, forming the easttilted Oquirrh Mountains (Stewart, 1978; Eaton, 1979; and Speed and 

others, 1988). Intrusion of sub volcanic quartz monzonitic porphyry 

stocks, sills, and dikes in faulted Oquirrh rock terranes in the 

Bingham (Lanier, and others, 1978), Ophir (Gilluly, 1932), and 

Stockton (Moore, 1973c) mining districts during the Eocene and 

Oligocene was followed by the extrusion of andesitic to latitic 

volcanic and volcaniclastic rocks mainly along the east side of the 

range (Smith, 1961; Moore, 1973a, and Swensen, 1975). Late-stage
11

hydrothermal solutions mixed with meteoric water containing baseand precious-metals were precipitated locally near the end of 

intrusive activity at Bingham (Moore, 1973c) in faults, in fractured 

and altered intrusions, and in structurally- and mineralogicallyprepared, stratigraphically-favorable sedimentary rocks adjoining 

the intrusions . Smaller and more sparsely distributed intrusive 

rhyolite, rhyolite porphyry, and granodiorite and monzonite 

porphyry stocks, dikes, or sills of similar Eocene and Oligocene ages 

(Gilluly, 1932; Moore and McKee, 1983) were emplaced locally into 

sedimentary rocks in the Mercur, Ophir, Stockton, and Barneys 

Canyon-Melco areas (fig. 3). Most of these intrusions also are 

spatially associated with ore deposits.

Finally, uplift, which raised the Uinta trend area, and 

Pleistocene glaciation both caused accellerated erosion, unroofed the 

mineralized areas in the Oquirrh Mountains and produced extensive 

alluvial fans and pediments along the range fronts. During the glacial 

interval, a very extensive freshwater lake formed in the valleys 

between ranges (Crittenden, 1963). The Lake Bonneville shorelines 

were sites for the formation of widespread, locally well-preserved 

bars, spits, and other coarse clastic shoreline deposits and erosional 

features. The most extensive examples of these surficial deposits are 

concentrated along the range front overlying the Uinta-trend zone; 

this distribution reinforces the observation that active, postmineralization uplift and erosion occurred along the Uinta trend.

OQUIRRH MOUNTAINS NAPPES

Five structurally and stratigraphically distinctive nappes 

located in the Oquirrh Mountains (fig. 3), include the Rogers Canyon, 

Pass Canyon, Bingham, South Mountain, and Fivemile Pass nappes. 

Base- and/or precious-metal ore deposits occur in some of the 

nappes (Tooker and Roberts, 1988, and 1998). The Rogers Canyon 

nappe lies at the north end of the range, in large part north of Nelson 

Peak; no mineral deposits are recognized in it. The Pass Canyon 

nappe, exposed across the central part of the range north and west of
12

the Bingham mine and south of Nelson Peak, contains the Barneys 

Canyon-Melco deposits. The Bingham nappe in the southern twothirds of the range, mostly south of the Bingham mine, is the site of 

the Bingham, Mercur, and Ophir mining districts. The South Mountain 

nappe is located mainly on South Mountain, west of the central part 

of the Oquirrh Mountains, but also includes the Stockton mining 

district area in the Oquirrh Mountains, immediately east of the town. 

The Fivemile Pass nappe is located north of Fivemile Pass at the very 

south end of the range and contains no base- or precious-metal 

deposits.

The identification and sequence of emplacement of the five 

Oquirrh Mountains nappes were based on permissive interpretation 

of stratigraphic, structural, and geophysical observations (Tooker, 

1983, and 1999). Although the ages and compositions of 

stratigraphic units in the nappes overlap or are similar, there are 

sufficient distinguishing features that, in combination with their 

structural attributes, permit recognition of them as individuals. 

Stratigraphic characteristics of the nappes and the relative directions 

and timing of thrust fault movements in the Oquirrh Mountains are 

summarized in table 1.

Table 1, NEAR HERE.

Subtle yet persistent differences in the stratigraphic 

composition of individual nappes, which varied from north to south 

along the craton shelf, are believed to be the result of sedimentation 

from different sources that bounded the Paleozoic sedimentary 

basins. These differences are most marked in Late Mississippian and 

Early Permian sedimentary rocks (Tooker and Roberts, 1988).

The Sevier decollement was broken into parts that moved 

eastward as individual nappes. The geometry of fold and fault 

structures in the Oquirrh Mountains nappes indicate that they 

travelled along separate paths into the foreland. The great diversity 

of these structures contrasts with more-regular less-disrupted nappe
13

structures to the north in the Wyoming salient (Oriel and Armstrong, 

1966) and to the south in the vicinity of Eureka, Utah (Morris, 1983). 

These nappes moved into topographic lows in the foreland whereas 

the Oquirrh Mountains nappes moved toward and onto a ridge or 

buttress in the craton platform overlying the Uinta trend. Here the 

nappes were diversely deflected (fig. 4), much as the lobes of a 

glacier are deflected when approaching an obstacle (looker, 1970). 

The different styles and magnitudes of the nappe fold structures 

observed in the 7-1/2-minute geologic quadrangle maps indicated 

the relative directions of plate movement (Tooker and Roberts, 1971, 

1988, 1992; Tooker, 1987, 1992). This assumes that the final 

direction of nappe movement was normal to the general trend of fold 

axes, and represents the approximate direction of tectonic transport.

The northern outcrops of the Pass Canyon nappe are 

intensively deformed and altered. It is presumed to have been the 

first east-directed lobe of the Sevier thrust belt to arrive in the 

Oquirrh Mountains (fig. 4). Its true thickness is undetermined here. 

The Permian sedimentary rocks of the nappe seem to be a muchdisturbed, thinner border facies resembling similar-age rocks in the 

Nebo-Charleston nappe in the Wasatch Mountains (Baker and others, 

1949, Tooker, 1983). On the basis of stratigraphic composition and 

structural complexity, the Pass Canyon nappe may be a split off from 

the Nebo-Charleston nappe. It is believed to be a part of that nappe 

intercepted on the north side of an unexposed tear fault and 

stranded on the Uinta-trend buttress.

The nearly 8,000 m-thick Bingham nappe, composed of 

lower and upper Paleozoic sedimentary rocks, arrived next and 

overlapped the Pass Canyon nappe from the west, forming a bold 

pattern of main and secondary folds and imbricate thrust faults. The 

Rogers Canyon nappe, composed of a nearly 4,000 m-thick section of 

Upper Paleozoic sedimentary rocks overrode both the Pass Canyon 

and Bingham nappes from the northwest. The arrival times are less 

certain for the 2,363 m-thick South Mountain and unmeasured but 

thinner Fivemile Pass nappes composed of Upper Paleozoic rocks,
14

which moved from the south-southwest. They apparently postdate 

the arrival of the Bingham nappe, which they overlap.

STRUCTURAL, STRATIGRAPHIC, AND ORE DEPOSIT 

CHARACTERISTICS OF MINING DISTRICTS IN THE OQUIRRH

MOUNTAINS

This brief regional geologic perspective for the development of 

Oquirrh Mountains nappes provides a setting for more detailed 

examination of the stratigraphic, structural, and intrusive features of 

mining districts in individual nappes. Descriptions of these features 

in the mining districts are the author's responsibility. Geologic data 

for individual ore deposits are derived from cited reports.

Bingham (West Mountain) Mining District

The Bingham (originally known as the West Mountain) mining 

district includes the largest deposits in the central part of the 

Oquirrh Mountains, and is located about 32 km southwest of Salt 

Lake City, Utah. The district is centered on the very large quartz 

monzonitic Bingham porphyry open-pit copper mine, underground 

copper skarn deposits, and peripheral base- and precious-metal vein 

and replacement deposits. The district is located geologically in a 

complexly folded, faulted, and thinned wedge-shaped leading edge of 

the Bingham nappe composed of Upper Paleozoic carbonate-quartzrich sedimentary rocks. The deposits are spatially associated with 

Tertiary intrusive and extrusive rocks (Bray and others, 1975, 

Tooker and Roberts, 1988; Tooker, 1990).

Early accounts of the discovery and development of lead-zinc 

and silver lodes and porphyry copper and gold deposits were 

described by Boutwell (1905). Recent mining activities in the district 

(fig, 6) are detailed by James (1978), Peters and others (1966), 

Atkinson and Einaudi (1978), Cameron and Garmoe (1983), and 

Babcock and others (1995). Production data from the Bingham 

mining district (Babcock, and others, 1995, and U.S.B.M. 1924-1993)
15

compiled in table 2 underscores the great magnitude of the open-pit 

and underground mine production of copper, molybdenum, and gold, 

and lesser amounts of silver, lead, and zinc from this world-class 

deposit. A number of minor metals are also produced.

FIGURE 6 and TABLE 2, NEAR HERE

Stratigraphy.--The, stratigraphic sequence of structurally 

competent sedimentary rocks at Bingham includes two Upper 

Pennsylvanian-age formational units of the Oquirrh Group (Tooker 

and Roberts, 1970), shown in part in the columnar section, figure 7. 

The Butterfield Peaks Formation at the base consists of cyclically 

interbedded calcareous quartzite, orthoquartzite, calcareous 

sandstone, and fossiliferous, arenaceous, cherty, argillaceous, and 

fine-grained dense limestones. The Clipper Ridge Member of the 

Bingham Mine Formation is composed predominantly of cyclically 

interbedded orthoquartzite, calcareous quartzite, and quartzose 

sandstones interbedded with several thick- to intermediate-thick 

limestones. The Jordan and Commercial limestone beds at the base 

of the member are the principal hosts of vein and replacement basemetal deposits. The Markham Peak Member (not shown in figure 7) 

contains interbedded orthoquartzite, calcareous quartzite, calcareous 

sandstone, and a few thin fusulinid-bearing arenaceous limestone 

units, which also are replaced locally near the intrusives.

FIGURE 7, NEAR HERE.

Structures.--Fold and fault surface structures in the Bingham 

mining district, shown in figure 8, are located on the forward margin 

of the thinned upper plate of the Midas thrust at the northern end of 

the Bingham nappe. The forward part of the Bingham nappe was 

thinned by shearing as the sole thrust rose against the Uinta trend 

buttress and cut across the stratigraphic section. Between Ophir and 

Bingham, in a distance of about 17 km, more than 4,000 m of the 

lower Paleozoic section as well as some of the lower parts of the 

Pennsylvanian Butterfield Peaks Formation were sheared out of the
16

upper plate of the nappe. The Midas thrust and complex folding at 

the base of the nappe are concealed at the surface by northweststriking, south-side-down, near-vertical cross faults that bring rocks 

of the Pass Canyon nappe into contact with those of the Bingham 

nappe. The location of the Midas thrust is inferred below tight to 

overturned folds observed in the North ore body (Tracy Shrier, 1988, 

oral commun.; Tooker, 1990, fig. E4; and Babcock and others, 1995, 

fig. 7). The "Midas thrust" mapped north of the open pit mine 

workings by James and others (1961), which they correctly 

considered to be of local extent, is one of the small thrust-fault 

imbrications above the sole thrust. This imbricate fault is 

comparable with those mapped on Markham Peak (Atkinson and 

Einaudi, 1978; Tooker and Roberts, 1988).

FIGURE 8, NEAR HERE

The Bingham syncline, the most prominent (main) fold in the 

district, is a tight, and locally overturned fold at the crest of the 

range on Markham Peak. The axial plane of the fold dips southwest 

and strikes southeastward toward the Bingham Canyon fault. 

Location of the syncline is obscured between the Bingham Canyon 

fault and a branch of the Main Hill fault, where (secondary) folds in 

the beds are very tightly folded and overturned. Southeastward 

across the northeast-trending Bingham Canyon fault, the Bingham 

syncline is offset as much as 0.2 km to the northeast and bends 

southeastward as a broad open fold with a near-vertical axial plane. 

In contrast, axial planes of folds in the Pass Canyon nappe strike 

northerly. The northeast-striking, steeply-dipping faults that offset 

the Bingham syncline are obscured by extensive mine dumps. 

Observation of the continuity of subparallel-trending dike intrusions 

that occur discontinuously along the faults is also limited by that 

cover.

The marked difference in style of folding across the northeast 

Bingham Canyon fault zone suggests that movement on its northwest 

side was impeded more than on its southeast side. This caused
17

tightening and overturning of the Bingham syncline and the 

production of imbricate thrusts such as those on Markham Peak. On 

the southeast side of the Bingham Canyon fault, the broad open-fold 

shape of the Bingham syncline indicates that nappe movement was 

less restricted. Even there, fault imbrications above the basal Midas 

thrust, such as the "Midas thrust" of James and others (1961) 

resulted.

Limited offset of bedding across clustered, steeply-dipping, 

northeast-trending, branching faults accompanied by local 

overturning of folds in the nappe imply the development of tension 

in the folds during early stages of emplacement. Bending of the fold 

from a tight, locally overturned west-northwest trend into a broad 

southeast-trend occurred as the Bingham nappe advanced 

tangentially onto the Uinta-trend buttress (Tooker and Roberts, 

1998). Somewhat farther along in the sequence of nappe 

emplacement onto the buttress, some of these faults locally 

developed into tear-faults, modestly offsetting secondary folds. 

During subsequent formation of the Basin and Range structures, 

many of the same vertical dipping faults seem to have been 

reactivated as normal faults. Open parts of the main northeaststriking faults ultimately became channelways for the movement 

and emplacement of Tertiary magma.

Intrusives.--rT}\Q Bingham and Last Chance stocks are located 

mainly on the southeastern side of the northeast-trending dike 

swarm emplaced along the faults in Bingham Canyon (fig 8). The 

more tightly-folded northwest side was not as open a structural site 

for monzonitic magma intrusions or for hydrothermal sulfide solution 

channelways. The Bingham stock is located mainly northeast of the 

Giant Chief fault (Lanier, 1978) in open parts of nappe folds that 

parallel the Bingham syncline. The Bingham and Last Chance stocks 

are separated by a block of locally overturned, tightly-folded, eaststriking sedimentary rocks (Galena Gulch folded zone) that also are 

cut by imbricate thrust faults and dike or sill intrusions. The folds in 

this block are truncated on the west by the Main Hill fault and on the
18

east by the Giant Chief fault. They lie at nearly right angles to the 

Bingham syncline and its adjoining folds. The Last Chance stock 

occurs south of the Galena Gulch block in an open-folded nappe 

terrane.

Sequential introduction of magma along northeast-trending 

faults probably was accompanied by continuing uplift and reopening 

of feeder faults overlying the Uinta trend. The compositional and age 

relations of intrusions listed in table 3 in the Bingham nappe 

aweremore fully detailed by Moore (1973b) and Warnaars and 

others (1978).

TABLE 3, NEAR HERE

The Bingham nappe folds and abundant intrusions do not 

project into the Pass Canyon nappe north of the A.J. and Midas faults, 

even though the steep northeast-striking faults extend across the 

plate contact. A few monzonite porphyry dikes similar in 

composition and age to the Bingham intrusive rocks crop out 

discontinuously in the Pass Canyon nappe (Babcock and others, 1995, 

and Tooker and Roberts, 1988).

Ore deposition The mineral-zoned Bingham mining district 

includes intrusive-centered and adjoining vein and replacement ore 

bodies. The central copper-molybdenum-gold ores in the altered 

Bingham stock and its associated dikes are mainly present along 

closely-spaced fractures in altered porphyritic quartz monzonite 

intrusion (Peters and others, 1966; and John, 1978). Less significant 

mineralization is located mainly along vein-faults in the adjoining 

less-fractured, mostly-unaltered Last Chance stock. The two stocks 

connect at depth (Babcock and others, 1995).

Highly saline hydrothermal fluids (400° to 600° C) that altered 

the host rocks and deposited metals are inferred from the chemical 

and isotopic compositions of fluid inclusions in the rocks (Field and 

Moore, 1971; Moore and Nash, 1974; and Bowman and others, 1987).
19

The temperature decreased to 300° C in the peripheral deposits 

(Roedder, 1971). Fluid inclusions and breccia pipes are evidence of 

shattering and boiling within the Bingham stock (Moore and Nash, 

1974). Nearly vertical unmineralized breccia pipes as much as 180 

m diameter occur along the south and east sides of the Bingham 

stock (Rubright and Hart, 1968).

Extensive vein and replacement base-and-precious metal 

deposits in the outer zone sedimentary rocks (Rubright and Hart, 

1968) surround the porphyry deposits (fig. 6). These outer zone ores 

occur along faults that provided access for hydrothermal solution 

movement into several of favorably reactive carbonate rocks in the 

Butterfield Peaks and Bingham Mine Formations (Tooker and 

Roberts, 1970). The base of the Clipper Ridge Member of the 

Bingham Mine Formation contains two thick beds, the Jordan and 

Commercial Limestones, which have been extensively replaced in the 

U.S., Lark, Utah Metals and Apex-Highland Boy mines. Several 

thinner carbonate beds in the predominantly calcareous quartzite 

and orthoquartzite, which compose the overlying Clipper Ridge and 

Markham Peak Members, also are mineralized where they cross 

northeast-trending fault systems in the district (Hunt, 1924; 

Rubright and Hart, 1968). Rubright and Hart also described the 

occurrence of fissure base-metal ores in the low-temperature outer 

zone southwest of the main Bingham porphyry deposits that contain 

siliceous gold-silver ores and rare native gold. The amount of gold in 

these veins generally increased toward the outer fringes and 

decreased with depth.

Close to the intrusion in lower parts of the mine, the Clipper 

Ridge carbonate rocks were metasomatized (Atkinson and Einaudi, 

(1978). Skarn alteration of the thick Commercial Limestone was 

divided into six mineralogic zones (from unaltered to contact with 

the intrusion) by Reid (1978): (1) marble, (2) wollastonite, (3) 

cristobalite, (4) garnet-clay, (5) garnet-quartz,, and (6), amphiboliteepidote. Atkinson and Einaudi (1978) described the association of 

sulfide ores within these skarn facies. An early copper-gold
20

deposition was followed by local high-grade gold mineralization 

(Cameron and Garmoe, 1983).

A number of much smaller vein and replacement deposits 

occur southwest of the Bingham mining district in Middle, 

Butterfield, and West Canyons. These deposits also are located on the 

bowed folded and faulted upper plates of the Middle-Butterfield and 

West Canyon imbricate thrusts, Commonly they are associated with 

dikes that seem to be compositionally similar but less abundant than 

those in the Bingham mining district. (Tooker, 1999, and Tooker and 

Roberts, 1998).

Conclusions.-The large zoned porphyry, skarn, and vein and 

replacement ore assemblages in the Bingham district are spatially 

associated with the largest and hottest intrusions and extrusions in 

the Oquirrh Mountains. The deposits was sited in structures 

prepared in locally-stressed parts of the Bingham nappe by the 

Sevier-age Midas thrust fault. The nappe was deformed as it ramped 

up onto the foreland buttress of the Uinta trend. Deformation 

produced folds and fractures in carbonate-rich, Upper Paleozoic host 

rocks in the frontal wedge-shaped, tightly folded and faulted edge of 

the nappe. The Uinta trend overlies a basement lineament that 

tapped sources of magmatic materials. The zone of local uplift 

structures along the trend provided fault access for magmatic 

materials into the overriding nappe. The intrusions pushed upward 

as stock, sill, and dike bodies along northeast-trending steep-dipping 

faults in the Bingham Canyon area. Late-stage hydrothermal 

solutions altered the igneous and sedimentary rock hosts. 

Temperature-sensitive base and precious metals were precipitated in 

concentric temperature-sensitive zones about the central intrusion.

Mercur (Camp Floyd) Mining District

The Mercur mining district, in the western side of the southern 

Oquirrh Mountains (fig. 1), contains disseminated gold deposits in 

mid-Paleozoic Upper Mississippian Great Blue Limestone. The
21

deposits are located in an eastward bow in the locally overturned 

Ophir anticline axis, a main fold on the upper plate of the imbricate 

Manning thrust (Tooker, 1987, and 1998). The regional stratigraphy 

of the rocks in the district were detailed by Tooker (1999) and 

Gordon and others (1999). Descriptions of the disseminated-gold ore 

deposits in the district are those by Kornze (1984), Kornze and others 

(1985), and Tafuri (1987).

The Mercur district was organized as a gold placer district in 

1870 (Gilluly, 1932). Silver ores were discovered in 1873, but the 

discovery of a cinnabar (mercury sulfide) vein in 1879 was the 

source of the district's name. Gold production became important in 

1892 and continued intermittently until World War II. Production of 

low-grade, very-fine-grained, disseminated gold by the Getty Mining 

Company began in 1983. The Barrick Mining Company bought the 

property in 1985 (Kornze and others, 1985, and Tafuri, 1987). 

Production data for the Mercur district are listed in table 2.

Production of gold, mercury, minor silver, and lead from the 

Mercur district, shown in table 2, is based mainly on information by 

Kornze and others (1985), Shrier (verbal commun. 1993), and the 

U.S. Bureau of Mines (1993). About 1.1 million ounces of gold and 

minor mercury and silver were produced in the district during the 

period 1871-1945, and 767 thousand ounces of gold and minor silver 

and mercury were produced in the period 1983-1990. Production 

data for byproduct silver are not readily available, but in 1983- 

1984, for example, Faddies and Kornze (written commun., 1985) 

reported that 118,037 oz of gold and 4,441 oz of silver were 

produced.

Stratigraphy.--The main Mercur district ores occur in the upper 

part of the 97 m-thick Silveropolis limestone lower member of the 

Great Blue Limestone (Gordon and others, 1999). The Silveropolis 

limestone is composed of interbedded thin-bedded argillaceous 

limestone and shale. It is brown weathering and generally 

abundantly fossiliferous. Except where faulted locally, the member
22

is overlain conformably by the Long Trail Shale Member of the Great 

Blue Limestone. The main productive stratigraphic horizons are in 

the upper part, in the "Mercur beds" of Kornze and others (1985). 

These beds include, in rising order, the silver chert jasperoid, 

magazine sandstone, a barren limestone, the Mercur bed, which 

contains the highest gold values and is composed of mudstone and 

grainstones rich in bryozoans, and finally, the upper limestone bed.

Structures.--The southern Oquirrh Mountains is composed of 

two adjoining through-going, southeast-striking main folds, a 

symmetrical (vertical axial plane) Pole Canyon syncline on the east 

side and the locally asymmetrical (axial plane locally tilted to the 

east) Ophir anticline on the west. The latter also has superimposed 

minor secondary folds, flexures, and small scale thrust imbrications 

along its western limb (Tooker, 1987). The stratigraphy and 

structures of these main folds differ markedly (fig. 9), and, east of 

Mercur, they are separated by the Manning (imbricate) thrust fault. 

The Pole Canyon syncline forms the higher, more rugged eastern side 

of the range and is composed of very competent, clastic, carbonate, 

and quartzitic rocks of the Butterfield Peaks Formation 

(Pennsylvanian) and underlying Manning Canyon Shale. 

(Pennsylvanian and Mississippian) The fold trends virtually 

uninterrupted to the southeastern end of the range (Tooker and 

Roberts, 1970). The faults in these rocks are generally wide-spaced, 

conjugate, steep-dipping normal faults with small displacement (figs. 

9 and 10). Rocks in the Pole Canyon syncline are not mineralized 

near Mercur, and no igneous rocks occur in them there.

FIGURES 9 and 10, NEAR HERE

In contrast, a sinuous, much faulted and bent Ophir anticline 

with a short, steep-dipping eastern limb and long, gentle-dipping 

west limb, forms a topographically lower and structurally more 

complex western half of the range south of the Lion Hill tear fault 

(Tooker, 1987, cross section BB1 ). It is composed of Lower Paleozoic 

carbonate-rich sedimentary rocks that range from the Cambrian
23

Tintic Quartzite to the Mississippian Great Blue Limestone (Tooker, 

1999). These rocks are broken by close-spaced, complexly-faulted, 

conjugate, steep-dipping faults. East of Mercur in Manning Canyon, 

an overturned fold in Great Blue Limestone in the upper plate of the 

Manning thrust laps onto younger, gently east-dipping Manning 

Canyon Shale, which is the basal exposure in the Pole Canyon 

syncline (Tooker, 1987). The amount of movement on the Manning 

thrust, which is steep and dips west, can not be determined, but is 

probably small to moderate in comparison with that of the sole 

Midas thrust.

South of the Lion Hill tear fault, which is about 1 km south of 

Ophir, Utah (fig. 9), the flat, broad, asymmetrical shape of the Ophir 

anticline is believed to result from less-constrained movement on the 

Manning thrust on the south side of the Uinta trend buttress. The 

trace of the Ophir anticline axis is flexed eastward at Mercur. Smallamplitude secondary folds and minor imbricate thrusts occur on the 

western flank of the anticline. Abundant shales and argillaceous 

limestones in Lower Paleozoic strata provided slip surfaces in the 

subsurface strata beneath the Ophir anticline that facilitated the 

Manning thrust's crossing formational units as it rose in Manning 

Canyon against the more competent Pole Canyon syncline structure 

(Tooker, 1987; fig. 10).

An irregular pattern of local close-spaced, conjugate, normal 

and tension faults having small stratigraphic displacement were 

formed in the Ophir anticline. Intersecting sets of northwest- and 

northeast-striking steep-dipping normal faults in Mississippian-age 

carbonate rocks locally have a crackled map pattern. The northwest 

set gradually becomes nearly west-northwest striking as the Mercur 

district is approached from the north. Most of these are more closely 

spaced faults than those to the northwest or southeast along the fold. 

This may be due to the additional tensional stresses caused by 

bending the fold locally where it is arched and overturned on the 

Manning thrust east of Mercur. Tension and tear faults also were
24

produced, and later local dilation was caused by the introduction of 

Tertiary intrusions.

Several small collapse structures also occur in the ore zone 

(Tooker, 1987). They strike nearly normal to the Ophir anticline, 

probably in response to increased tensional structures in that part of 

the fold, and are associated spatially with breccia pipes, one of which 

is mineralized (T.B. Faddies, verbal commun., 1988). The largest of 

these structures, the "Lulu syncline," probably was formed by a 

phreatic explosion and collapse during a late stage in the intrusion of 

the rhyolite porphyry sill. The local occurrence of intrusives and 

collapse structures normal to the bend in the Ophir anticline at 

Mercur are added evidence of the tensional fractures in sedimentary 

rocks in a thrust-thinned part of the upper plate of the Manning 

thrust fault.

Intrusives. --The Ophir anticline is cut by small sill and dike 

intrusions composed of finely crystalline rhyolite and rhyolite 

porphyry. They trend westward across the Ophir anticline to the 

range front and the West Mercur mining area. Recurrent exposures 

of these dikes trend northward to the Ophir mining district along 

imbricate thrusts and bedding faults.

There seems to be a close spatial association of the rhyolite 

sills, dikes, and plugs with mineralized sedimentary rock, but at 

present no evidence of mineralization in the rhyolite has been 

observed or of resetting of illite K/Ar (average) age of 152 +/- 4 Ma 

for the gold-bearing hydrothermal event (Wilson and Parry, 1995).

Regional geologic studies of intrusives and their host rocks in 

western Utah may provide more definitive data. Based on 

conclusions of Camilleri and others, (1994), Miller and Hoisch (1995), 

and Elison (1995), the impact of the Elko orogeny was localized well 

west of Mercur. Allmendinger and Jordan (1981) suggest that the 

Jurassic intrusions and metamorphism provided a source of heat that 

initiated later Sevier thrust. It seems likely that the Sevier thrust
25

produced the significant regional main folds observed in the Oquirrh 

Mountains. There are no known Jurassic intrusions in the vicinity of 

the Oquirrh Mountains. All of the mining districts in the Oquirrh 

Mountains are located in a continuous Sevier-age foreland thrust 

belt, but at variable distances from the Uinta trend, which is a 

potential crustal source structure for admitting Tertiary intrusions. 

Mercur is located farthest from the trend, its igneous rocks are 

younger than those overlying the trend at Ophir or Bingham (table 

3), and the minerals associated in the deposits are formed at lower 

temperatures. The rhyolite dikes and stocks in the Ophir mining 

district connect with those at Mercur, thus providing a linkage with 

the higher-temperature Ophir deposits, which are closer to the Uinta 

trend.

Ore deposits.--Gold, silver, and mercury ores occur as bedded 

and irregular replacements, veins, fine-grained disseminations, and 

fissure deposits (Kornze and others, 1985). Alteration of the 

carbonate rocks initially was decalcification and introduction of 

quartz followed by development of kaolinite and sericite. Oxidized 

ores near the surface grade into hypogene sulfide ores in the deeper 

parts of mines. Gold mineralization conforms to bedding, but not to 

any particular bed (Kornze and others, 1985). The distribution of 

metals seems to be the result of variations in porosity, fracture 

density, and chemical composition in the beds, and a location near 

feeder faults.

It is uncertain whether the ores are the result of hydrothermal 

activity associated in some manner with the adjacent rhyolite 

intrusives, or their source at depth (Morris and Tooker, 1996), or 

whether, as suggested by Wilson and Parry, (1990, 1996), that the 

gold ores were mobilized from adjacent shales at depth in western 

Utah or eastern Nevada during the Late Jurassic orogeny in advance 

of very extensive regional Sevier-age thrusts and Tertiary intrusions 

in the Oquirrh Mountains.
26

Conclusions.--The formation of gold ores in the Mercur mining 

district is based on the following factors. First, the structural and 

stratigraphic configurations of folds and thrust faults in the range 

(Tooker and Roberts, 1998) are most compatible with development 

during the Late Cretaceous Sevier orogeny. They are regionally 

extensive foreland structures, both north and south of the Mercur 

district. Second, ore deposits are spatially associated with a locallystressed part of the Ophir anticline on the upper plate of the 

Manning thrust. Third, Tertiary-age hydrothermal ores are trapped 

in variably porous, fractured, and overturned beds of the lower 

member of the host Great Blue Limestone at the bent, leading edge of 

the Manning thrust. The Great Blue Limestone also hosts ores in 

similar strata and structures in other mining districts or areas in the 

range. Fourth, there are breccia pipes, and evidence of phreatic 

activity in the Mercur area, which supposes hydrothermal activity.

A tentative hypothesis, which will require further field data in 

the region, is that the argillaceous lower Paleozoic rocks, and 

particularly those of the Great Blue Limestone, were metamorphosed 

at depth in the Utah-Nevada border hinterland during the Jurassic 

Elko orogeny. They were moved eastward and raised to their 

present foreland Bingham nappe site in the Oquirrh Mountains on 

the sole Midas and imbricate Manning thrusts. The tension 

structures developed in folds locally in the nappe at Mercur are 

comparable with those developed in other mining districts in the 

range. Because of the distance from the heat source underlying the 

Uinta trend, the Jurassic ages of clay-minerals in the Great Blue 

Limestone at Mercur apparently were not reset by the lowtemperatures that accompanied introduction of the Mercur rhyolites. 

Sedimentary host rocks were not altered to high-temperature 

mineral assemblages by hydrothermal solutions. Low temperature 

gold, cinnabar, silver, and base metal deposits produced were 

concentrated in the Silveropolis member. Similar assemblages also 

occur in the cooler peripheral hydrothermal deposits at Bingham 

(Rubright and Hart, 1968). Thus the possibility exists that Mercur
27

gold and associated sulfide ores also may be of Tertiary-age 

hydrothermal origin.

Ophir Mining District

The Ophir mining district is located in Ophir Canyon on the 

western side of the southern Oquirrh Mountains about 6.0 km north 

of Mercur (fig. 1). The base-and precious metal deposits occur in 

replaceable carbonate-rich beds in Lower Paleozoic formations along 

the northern part of the Ophir anticline, mostly north of the Lion Hill 

tear fault, in the upper plate of the Manning thrust fault. The district 

was subdivided geographically by Gilluly (1932) into three parts: 

The main Ophir Hill area is on the north side of Ophir Canyon, the 

Lion Hill area is located on the south side of Ophir Canyon, and the 

Dry Canyon area lies northwest of Ophir Hill on the ridge above Ophir 

Canyon (fig. 11) at the head of Dry Canyon.

FIGURE 11, NEAR HERE.

The Ophir deposits were discovered in 1865 by soldiers 

stationed nearby, but surface outcrops of lead minerals in the 

Treasure Hill area in Ophir Canyon were known earlier by the Native 

American Indians (Gilluly, 1932). The town of Ophir was established 

in 1870, a district formed, and mining of oxidized lead-bearing 

surface lodes began. Production was from lead, silver, copper, and 

zinc bedded replacement, irregular replacement, and pipe, vein, and 

fissure ore bodies (table 2). Skarn ores occur in the deeper parts of 

the Ophir Hill mines and include lead, zinc, and silver sulfides and 

minor gold (Weintraub, 1957). Main development of most of the 

mines occurred in the mid- and late 1870s, and Gilluly (1932) relied 

mainly on oral and mining company reports because most of the 

mines were inactive or closed. According to Rubright (1978) most of 

the mines in the Dry Canyon and Lion Hill areas were exhausted in 

the late 1870s and early 1880s. The district was intermittently 

active in the deeper parts of the Ophir Hill area until 1970, and was 

finally shut down in 1971 (Rubright, 1978).
28

The main production from the Ophir Canyon area was from the 

Hidden Treasure and Ophir Hill mines (Gilluly, 1932). Records of 

early mining activity (1870-1901), which included some high-grade 

ores, are incomplete and existing records suggest that production 

may have been in the range of a few million dollars (Gilluly, 1932). 

Production from Ophir mining district in those years was combined 

with production from the Stockton mining district. Data from U.S.G.S. 

and U.S.B.M. records between 1902 and 1972 (table 2) indicate that 

lead was the principal metal recovered in the lower parts of the 

Ophir Hill area. Zinc, silver, gold, and copper were minor constituents 

of these ores. Potential ore reserves persisted below the lowest 

mined level at 1980 m in the Ophir Hill area (Rubright, 1978).

Stratigraphy.--The main sites of ore deposits are in replaceable 

shaly limestone and limestone horizons adjoining veins and in vein 

intersections of near-vertical, northeast-striking fissures. Favorable 

formations include the Cambrian-age Ophir Formation and Lynch 

Dolomite, the undivided Devonian-age Fitchville Formation and 

Pinyon Peak Limestone, the Mississippian-age Gardison Limestone 

(probably the most extensively replaced formation), Deseret 

Limestone, Humbug Formation, and Great Blue Limestone (Gilluly, 

1932). Most recent mining activity was from veins and adjoining 

Lower Cambrian Ophir Formation skarns (Weintraub, 1957; Rubright, 

1978).

Structures.--The Ophir anticline, the Manning and overlying 

imbricate thrusts, and a deep-reaching northeast-trending fracture 

system are the main host rock structures in the Bingham nappe at 

Ophir. North of the Lion Hill tear fault, the Manning thrust is offset 

northeastward and exposed in a side canyon opposite the mouth of 

the South Fork of Ophir Canyon. Here the Manning thrust also 

separates the faulted terrane in the overlying Ophir anticline from 

the competent Pole Canyon syncline.
29

The Ophir anticline was lifted upward by the Manning thrust as 

it glanced steeply up and was stretched and draped over the Uinta 

trend buttress. The fold axis was bent downward as it plunged to 

the northwest. Its nearly symmetrical anticlinal form was preserved 

unlike its asymmetrically-shaped counterpart at Mercur (Tooker, 

1987, cross sections AA' and BB'). Imbricate thrusts were formed on 

its western flank. Bending the anticlinal axis across the Uinta trend 

zone at Ophir produced deep-reaching, northeast-trending, branching 

tension faults normal to the Ophir axis. Beds cut by the faults were 

not greatly offset laterally (Gilluly, 1932). Several of these tension 

fault structures intersected the Lower Paleozoic section, reaching 

more than 2,800 m down from surface exposures of the Great Blue 

Limestone to to an unknown depth below the Tintic Quartzite 

(Gilluly, 1932; and Tooker and Roberts, 1992).

The Lion Hill area is located in the upper plate of the imbricate 

Long Trail thrust fault, a local imbrication above the Manning thrust 

that lies east of the crest of the Ophir anticline, and immediately 

south of the Lion Hill tear fault. The location of the deposits was 

controlled mainly by northeast-striking branching fissures that were 

formed by tension in the Silveropolis member during the local 

bending of the fold axis. The deposits occurred in irregular pipelike 

bodies that formed along fault intersections in the Silveropolis 

limestone, and as blanket replacements of the limestone (Gilluly, 

1932).

The Dry Canyon area, west of Bald Mountain, is on the thinned 

and arched upper plate of one of several imbricate thrusts on the 

western limb of the Ophir anticline in the upper plate of the Manning 

thrust. The thrust(s) bring lower Mississippian-age limestone over 

the Great Blue Limestone. Steep-dipping tear and normal faults 

segment the near-bedding thrust and provided channelways for the 

upward migration of ore-forming solutions into Mississippian 

sedimentary rocks.
30

Intrusives.--The ore deposits in all areas in the Ophir mining 

district are closely associated with granodiorite or rhyolite intrusives 

(table 3). These igneous rocks gained entrance into the region along 

faults that seem to tap a Uinta-trend source. Granodiorite plugs, 

dikes, and sills occur spatially with deposits in the Lion Hill area. 

Monzonite-type dikes trend discontinuously along the faults 

overlying the Uinta trend between Bingham and Ophir (Tooker and 

Roberts, 1998).

Younger rhyolite and rhyolite porphyry intrusives are traced 

intermittently from Mercur to Ophir Hill and Dry Canyon. They are 

undated here, but presumed to be of ages comparable with their 

counterparts at Mercur (table 3). The dikes intersect northeaststriking, steep normal or tension faults in the Ophir Hill area, and 

then extend discontinuously into the Dry Canyon area along bedding 

and overlying imbricate thrust and normal faults. The Bald 

Mountain stock is the northern terminus of the rhyolite bodies. 

Weintraub (1957) believed that intrusion of the rhyolite/rhyolite 

porphyry dike and rhyolite breccias that cross the district postdate 

silication and predated the deposition of scheelite at Ophir Hill.

Ore deposits. --Oxidized base- and precious-metal ores in the 

upper parts of the Ophir Hill and adjacent mines occurred in pipes 

and vein fissures and as bedded or irregular replacements adjacent 

to through-going deep-reaching fissures. Ores in the deepest part of 

the Ophir Hill mine included galena, sphalerite, chalcopyrite, and 

pyrrhotite as the main ores minerals in the fissures, and as 

disseminations and replacements in adjoining limestones and skarns 

along bedding planes (Weintraub, 1957). Scheelite and wolframite, 

and bismuth and cadmium also occurred in fissures as 

disseminations in skarn ores in the Ophir Formation in the lower part 

of the Ophir Hill mines (Rubright, 1978). Skarns in the lower parts of 

the Ophir Hill mine are evidence of temperatures at depth nearly 

comparable with those occurring at Bingham (Weintraub, 1957; and 

Rubright, 1978) .
31

Vein and replacement deposits at Lion Hill occurred in the 

upper part of the Mississippian Silveropolis limestone member of the 

Great Blue Limestone, immediately below the Long Trail Shale 

Member (Gilluly, 1932; Gordon and others, 1998; and Tooker, 1999). 

These deposits are closely associated with porphyritic granodiorite

sills and dikes.

<

The vein and replacement deposits in the Dry Canyon area 

occur in Mississippian Gardison Limestone, Deseret Limestone, 

Humbug Formation, and the Silveropolis limestone member of the 

Great Blue Limestone, and Long Trail Shale Member of the Great Blue 

Limestone (Gillully, 1932 and Tooker, 1999). These deposits are 

spatially associated with rhyolite dikes and sills. Neither the Lion 

Hill or Dry Canyon area deposits were mined at depth. One presumes 

that exploration failed to find deeper extensions below the imbricate 

thrust faults that underlie the mines.

Conclusions.--The principal ore deposits in the Ophir mining 

district at Ophir Hill occurred in or adjacent to faults overlying the 

axis of the locally-stressed thrust-induced Ophir fold on the upper 

plate of the Manning thrust. The Ophir anticlinal axis was bent to the 

northwest as it moved east-northeast up against and draped over the 

Uinta trend buttress. Its northern part plunged to the northwest, 

and was overridden by several secondary thrusts. Tension across 

the stressed fold normal to its axis (across the Uinta trend buttress 

produced a northeast-trending, steep-dipping, deep-reaching, 

complex-branching fault zone. Sedimentary units across the faults 

have only moderate displacements. The thoroughgoing faults 

intersect a number of very replaceable, widely age-ranging lower 

Paleozoic carbonate horizons.

Magmatic materials moved up into fault openings in 

sedimentary rocks of the nappe at Ophir Hill, forming intrusions and 

accompanying hydrothermally altered host rocks and precipitation of 

the ores. The temperatures of solutions producing skarn ores in the 

deepest Cambrian formations appear to be comparable with those at
32

Bingham. This places the Ophir Hill deposits near the center of the 

Uinta trend, overlying its heat source.

Smaller deposits or prospects occur in the Great Blue Limestone 

at the thinned leading edge of the Manning thrust also. These 

deposits occur in the peripheral Lion Hill and Dry Canyon areas of the 

Ophir mining district. They overlie small imbricate thrusts in the 

upper plate of the Manning thrust. These deposits also are spatially 

related to intrusive rocks

Stockton (Rush Valley) Mining District

Base- and precious-metal ores at Stockton (originally called the 

Rush Valley mining district), are located in the eastern part of the 

South Mountain nappe, east of the town of Stockton, Utah. These 

deposits occur in the folded and faulted upper plate of the Stockton 

thrust (figs. 3 and 12), which overlaps the Bingham nappe (Tooker 

and Roberts, 1992, and unpublished data). The South Mountain 

nappe is, in turn, overlapped from the west by the Tintic Valley 

thrust, which underlies the Stansbury Mountains (Tooker, 1983). 

Rush Valley deposits were discovered in 1864 by soldiers who were 

guarding stock on a government reservation in the area (Gilluly, 

1932). Assays proved to be rich in silver, and a mining district was 

organized. Several local smelters treated the ores intermittently 

until 1880, after which ores were taken to smelters in the Salt Lake 

Valley. The geology of the district is reported by Mitchell (1908), 

Gilluly (1932), Tooker and Roberts (1992) and Tooker 1999). 

Geochemical studies are by Moore and others (1966) and geophysical 

data are reported by Mabey and others (1964).

FIGURE 12, NEAR HERE

Production data for metals recovered at Stockton during its 

early period were combined with data from the Ophir mining district 

(Table 2). Data from the district's later production, 1902-1970, are 

shown separately. Moore and others (1966) reported an
33

unpublished communication (from E. H. Snyder, 1965) that since 

1864, the district produced more than $30 million from about 

1,200,000 short tons of ore. Proportions of production values 

reported through 1927 include: Lead 75 percent; silver, 16 percent; 

zinc, 5 percent; gold 3 percent; and copper 1 percent.

Stratigraphy. --The limestone host rocks in the South Mountain 

nappe are nearly comparable in age, and, in a general way, are of 

similar composition but much thinner than those in the Bingham 

nappe in the Bingham mining district (fig. 7). The ores at Stockton 

occur in the Pennsylvanian Rush Lake and Salvation units of Tooker 

and Roberts (1992), which are composed mainly of calcareous 

quartzite and orthoquartzite with subordinate medium-bedded (6 to 

24 m thick) limestones. The Salvation unit stratigraphy is correlated 

agewise with the Jordan and Commercial limestones in the lower part 

of the Pennsylvanian-age Clipper Ridge Member of the Bingham 

Mine Formation (Tooker and Roberts, 1970). However, the 

sedimentary rock units at Stockton do not include thick, cyclically 

repeated argillaceous, fossiliferous, arenaceous, and cherty 

limestones that typify the Butterfield Peaks Formation or the thick 

limestone beds that occur at the base of the Clipper Ridge Member 

(fig. 7, and Tooker and Roberts, 1992). Most ores occur in altered 

and replaced limestone beds adjacent to faults rather than in faults 

(Gilluly, 1932).

Structures.--The mining district is located in the eastern part of 

the nappe on the thinned upper plate wedge of the Stockton thrust in 

tightly folded, locally overturned, low-amplitude secondary folds. 

Emplacement of the nappe resulted in the formation of a broad arc, 

bending the folds, and creating a system of prominent, close-spaced, 

steep-dipping, branching, north-striking tension faults and bedding 

faults. Horizontal displacements of bedding across faults rarely 

exceeded 30 m.

The western and more massive thicker part of the nappe on 

South Mountain, which exposes a single main west-northwest
34

directed anticline, overlies the T.A.D. imbricate thrust (shown on fig. 

3, and by Tooker and Roberts, 1998). The western part of the nappe 

is separated from the eastern part by the northeast-trending Rush 

Valley tear fault. Several warm springs occur along the trace of this 

fault. The anticline is bent west, becomes slightly overturned, and 

plunges beneath the Tintic Valley thrust. The fold is not as fractured 

as are those in the Stockton mining district and only a few 

unconnected intrusions occur along the faults.

Intrusive s.--The ore-bearing structures in the Stockton mining 

district are spatially coextensive with intrusive porphyritic quartz 

monzonite and quartz monzonite pluton, dike, and sill bodies (table 

2). Monzonite dikes, small plutons, and sills occur irregularly and 

discontinuously across the range from the Bingham district into the 

Stockton district (Tooker and Roberts, 1988, 1992; Tooker 1992) 

along northeast-trending faults. The largest body, the Stockton stock 

(Lufkin, 1965), lies at the edge of the Bingham nappe, but 

geophysical data imply that it is connected in the subsurface with 

smaller plugs or stocks in the Stockton district. These intrusive rocks 

lie along the projected trace of the Uinta trend. Formation 

temperatures of hydrothermal ore minerals at Stockton were lower 

than those at Bingham or Ophir Hill. Warm springs along the trace of 

the Rush Valley fault indicate that a heat source still exists along the 

trend.

Ore Deposits.--Ores are localized in vein deposits along the 

contacts of steep, northeast-trending fissures that cut favorable 

carbonate rocks, and as replacements in limestone horizons adjacent 

to the feeder faults (Gilluly, 1932 and Tooker and Roberts, 1992). 

Ores near the surface were mostly oxidized with local residual sulfide 

zones, but below 240 m., the ores were mostly sulfides of lead, zinc, 

copper, and silver and some gold. Apparently minable ore deposits 

do not persist much below the basal Stockton thrust. The last 

working mine, the Ben Harrison (New Sockton) mine, was closed in 

1972. Although the district currently is inactive, it has been the site 

of recent exploration for Mercur-type disseminated gold.
35

Conclusions.--The, South Mountain nappe is separated from the 

Bingham nappe by the Soldier Creek (tear) fault (Tooker, 1999). The 

thrust fault-induced fold and tensional fault structures in the 

Stockton mining district, in the eastern part of the South Mountain 

nappe, are similar to those in districts elsewhere in the Oquirrh 

Mountains. The nappe consists of a thinned wedge that rode 

obliquely onto a buttress formed by the Bingham nappe and 

underlying Uinta trend. The nappe is folded, locally overturned, and 

stretched where the fold axes are bent. Tension faults formed in 

stretched parts of fold became the locus for intrusives and alteration 

by hydrothermal solutions. Limestone beds intersected by these 

faults were altered, and locally replaced by sulfides. Ore deposits 

were not deep-reaching and seem to be restricted to the upper plate 

of the Stockton thrust. They are comparable in composition with 

base metal deposits that occur in the upper reaches of the Ophir 

mining district. No high-temperature skarns are found.

The western part of the nappe consists of a main fold on the 

imbricate T.A.D. thrust. It was not thinned, greatly stretched, or 

much faulted as it overran the unexposed eastern part of the South 

Mountain nappe on the Stockton thrust. Igneous rock intrusions and 

hydrothermal alteration were restricted in the western part of the 

nappe. No ore deposits formed here.

Barneys Canyon and Melco Mining Areas

The Barneys Canyon-Melco deposits are located 8 km north of 

the Bingham Canyon mine on the east side of the Oquirrh Mountains 

(figs. 3 and 13). The sediment-hosted disseminated gold deposits, 

which occur in the Flood Canyon unit of Tooker and Roberts (1988), 

contain minor silver, and were recognized and developed by 

Kennecott (Babcock and others, (1995) after completion of the 

author's field studies. However, this was a known mineralized area, 

based on numerous small adits, shafts, and prospect pits (Tooker, 

1999).
36

Gold production at Barneys Canyon began in 1989. Babcock 

and others, (1995) and Presnell and Parry (1995) considered that the 

disseminated gold deposits are part of the Bingham mining district. 

U.S.G.S/U.S.B.M. production data are shown in Table 2. Gunter and 

others (1990) estimated that the deposit contained 8.5 million metric 

tons averaging 1.6 g/t gold. Babcock and others (1995) reported that 

503,000 oz were produced by 1993, with a reserve of 392,000 oz. 

The Melco deposit is considered to contain an additional 196,000 oz. 

reserve (Gunter and others, 1990).

Stratigraphy.--The upper part of the Barneys Canyon deposit 

was discovered in an altered down-dropped klippen cap of 

fossiliferous Grandeur Member of the Park City Formation of 

Permian age, a part of the Rogers Canyon nappe emplaced over the 

Pass Canyon nappe (Tooker and Roberts, 1970, 1971). However, the 

main part of the Barneys Canyon deposit lies in the underlying 

Permian Flood Canyon unit of Tooker and Roberts (1988). [These 

host formations were designated by Presnell and Parry (1996) as the 

Grandeur Member of the Park City Formation and Kirkman-Diamond 

Creek Sandstone.] The deposit host rocks consist of interbedded 

fossiliferous, arenaceous, and dolomitic limestones, dolomite, shale, 

phosphorite, and chert in the folded, upper part of the Pass Canyon 

nappe. Gunter and others (1990), Babcock and others (1995), and 

Presnell and Parry (1996) provide more detailed geologic 

information about the Barneys Canyon and nearby Melco deposits.

FIGURE 13, NEAR HERE.

Structures. --Regional mapping indicates two formational units 

in the Pass Canyon nappe, both of which are separated by thrust 

faults. The folded lower Permian Dry Fork unit of Tooker and 

Roberts (1988) overlies an unexposed sole thrust fault. The Flood 

Canyon unit of Tooker and Roberts (1988), which hosts the Barneys 

Canyon and Melco deposits, is characterized on the northwest by 

tightly bent, close-spaced, low-amplitude, overturned folds on the
37

upper plate of an imbricate thrust fault. Numerous local thrust 

imbrications with small displacements occur between tear faults. 

Local alteration of the Permian-age carbonate rocks is present in 

these displaced units. Refolding of tight isoclinal folds is attributed 

to later overriding nappe plates (Tooker, 1998). Structures in the 

eastern part of the nappe, are farther away from the highest 

westernmost part of the buttress west of Nelson Peak. In the deposit 

occurrence area, the folds are less fragmented and altered, but 

locally are overturned and their northeast-trending axial planes dip 

southeast (fig. 13). The leading edge of the thrust fault against the 

Uinta trend buttress is concealed by a northeast-trending, steep 

normal fault that drops the Erda Formation in the Rogers Canyon 

nappe into contact with the Flood Canyon unit. The southern margin 

of the Pass Canyon nappe is concealed beneath the Bingham nappe 

(Tooker and Roberts, 1998).

Ore Deposits.--The gold ores, as described by Presnell and 

Parry (1996), are sediment-hosted disseminated deposits that occur 

mainly in carbonates and sandstones in the Flood Canyon unit. 

Hydrothermal alteration of the host rocks included decalcification, 

silicification, and argillization. Gold was accompanied by pyrite, 

marcasite, minor arsenic sulfides and the trace elements, As, Sb, Hg, 

Ba, and Tl. Fluid inclusions in quartz and barite and a lack of 

pyrophyllite indicated a maximum pressure of 700 bars and a 

temperature of 278° C. The main ore body in the Barneys Canyon 

deposit was nearly stratabound, occurring along the contact zone 

between dolomite and sandstone, and seems to be concentrated along 

a northeast-trending fault zone (Gunter, and others, 1990, Babcock 

and others, 1995, and Presnell and Parry, 1995).

Intrusives. --Igneous intrusives are not found in the Barneys 

Canyon or Melco deposits; however, an altered porphyritic monzonite 

dike occurs in the vicinity, west of the Melco deposit

Conclusions.--Geologic evidence from a summary map of the 

Oquirrh Mountains (Tooker and Roberts, 1998), and the regional
38

geologic setting, (Tooker, 1999), leads to the belief that the folded and 

faulted nappe structures were formed over the Uinta trend basement 

buttress during the Severe orogeny. The Permian stratigraphy is 

unique to the Pass Canyon nappe. It most resembles that in the 

Timpanogos nappe in the Wasatch Mountains and may be detached, 

thinner distal part of that nappe stranded in the Oquirrh Mountains 

by the Uinta trend buttress. The spatial association, if any, of ore 

deposits with sparse scattered Tertiary intrusive rocks in the nappe 

is not clear. The Barneys Canyon-Melco deposits lie on the northern 

periphery of the Uinta trend, and, like the deposits at Mercur, lie 

some distance away from the main Bingham intrusions and mineral 

deposition centered over the Uinta trend.

The production of folded thrust structures in the Barneys 

Canyon deposit was attributed by Babcock and others, (1995), Wilson 

and Parry, (1995), and Presnell and Parry, (1995) to the Jurassic-age 

(Elko) orogeny, based on their observations of K-Ar ages of illite in 

fault clays. And, as at Mercur, they believed that gold mineralization 

at Barneys Canyon was derived from Middle and Late Jurassic 

plutonism and contact metamorphism of adjacent sedimentary rocks 

resulting from a compressional event in eastern Nevada and 

northwestern Utah. However, Camilleri and others (1994), Elison 

(1995), and Miller and Horsch (1995) report only local thrusting 

resulting from this Jurassic event. Thus, the attribution of extensive 

thrust-fault folds of Jurassic age in the Oquirrh Mountains seems 

problematical in terms of regional geologic relations noted earlier.

The author's hypothesis for the thrust-fault localization of ore 

deposits is less clearly demonstrated here than in other parts of the 

Oquirrh Mountains because structures resulting from later-formed 

overlapping nappes conceal critical contacts. However, the geologic 

structures elsewhere in the Oquirrh Mountains are a direct link in an 

extensive Sevier-age fold terrane stretching from Alaska to Mexico. 

The author believes that insertion of Jurassic thrust structures in the 

Oquirrh Mountains in the midst of an otherwise regionally extensive 

Sevier thrust terrane is not a tenable conclusion. It does seem
39

possible that regional metamorphism produced Jurassic-age illites in 

the hinterland during deep burial and coincident with the intrusion 

of Jurassic-age plutons prior to the movement of the nappes 

eastward as part of Sevier-age thrusts. This Jurassic geochemical 

imprint is preserved only in the rocks at a distance from the main 

Tertiary intrusions along the Uinta trend, which destroyed the record 

of the earlier metamorphism. Until this problem is satisfactorily 

resolved, the uncertainty of origin for the Barneys Canyon-Melco 

(and Mercur) ore deposits remains. In the meantime, the author's 

tentative conclusions seem to be most reasonable possibilities for the 

origin of ore deposits in the Oquirrh Mountains.

CONCLUSIONS

The occurrences of base- and precious-metal mining districts in 

Oquirrh Mountains nappes are considered in the context of their 

regional geologic setting. Their occurrence is believed to depend on 

the conjunction of interacting geologic events over a period from the 

Precambrian to Quaternary. (1) An active basement Uinta trend 

fault-zone lineament were formed in the Precambrian craton. (2) 

Reactive carbonate Paleozoic sedimentary rocks resulting from 

erosion of the craton or Antler highland were deposited in the main 

hinterland areas. (3) Low temperature metamorphism of deeply 

buried clay-bearing sediments in the hinterland imprinted a Jurassic 

age in illite in clay-rich (Mississippian) sedimentary rocks. (4) Late 

Cretaceous thrust faults moved nappes composed of Paleozoic 

sedimentary rocks from the hinterland into foreland areas such as 

the Oquirrh Mountains. Fault structure openings were formed locally 

in the folded sedimentary rocks. (5) Tertiary igneous bodies moved 

up from the Uinta trend basement zone into faulted and fractured 

structures. Hydrothermal alteration followed in and peripheral to 

the intrusives, and ore minerals were precipitated. (6) Finally, 

Quaternary uplift and erosion unroofed the deposits.

Late Cretaceous-age thrust faults of the Sevier orogeny brought 

five nappes eastward to their Oquirrh Mountains foreland sites
40

against an uplifted Uinta trend basement buttress. Mining districts 

are clustered in three of the nappes that overlie or are on the 

periphery of the Uinta trend craton zone. The principal common 

thrust-related structures that typify the mining districts include 

bent, arc-stressed, asymmetric-shaped, locally-overturned folds, and 

steep-dipping, branching tension and tear faults developed normal to 

the fold axes by sole and/or imbricate thrust faults on the thinned, 

leading edges of nappe wedges rising against the basement Uinta 

trend buttress.

These conclusions are based on the following observations and 

interpretations of regional and Oquirrh Mountains geology:

(1) A mobile, east-west-trending basement lineament in the 

craton, the Uinta trend, separated the Paleozoic depositional area into 

two parts, the Oquirrh and Sublette basins. Contrasts are observed 

between the sedimentary strata formed in the Sublette basin and 

those formed in the Oquirrh basin. Clean, well-sorted clastic and 

precipitated quartz- and carbonate-rich craton-derived sedimentary 

materials from the east characterize Oquirrh basin rocks. The 

Sublette basin sedimentary rocks commonly consist of unsorted 

sedimentary materials and volcanic debris derived from a western 

Antler highland oceanic source area, mixed with well-sorted 

sedimentary materials typical of a cratonal source area. Occasional 

local uplift along the Uinta trend produced coarse clastic debris in 

some of the sedimentary rocks in the Pass Canyon nappe, which 

seems to represent an intermediate deposition site between the two 

main basins.

(2) A thick sequence of Paleozoic-age sedimentary rocks 

accumulated in the hinterland as the basins subsided. Subsequent 

regional metamorphism in the area occurred during the Late Jurassic 

Elko orogeny imprinting a Jurassic age on contained clay minerals.

(3) Decollement during the Late Cretaceous Sevier orogeny 

moved five sedimentary rock nappes on sole thrust faults from
41

different parts of the hinterland basins eastward to their foreland 

sites, forming the present Oquirrh Mountains

(4) The site of the Oquirrh Mountains lay over an uplifted part 

of the Uinta trend, forming a buttress over which the nappes were 

individually draped and structurally deformed in sequence. The five 

nappes are recognized by unique fold patterns and their 

stratigraphic characteristics.

(5) The nappes were folded as they piled up against the Uinta 

trend buttress. Tensional, normal, and tear faults as well as 

imbricate thrusts were developed locally along the thinned, leading 

margin of the thrust where folds are arched or bent. Some of the 

folds locally were overturned along the front edges of the rising 

nappe.

(6) The mobile Uinta trend structure tapped crustal sources of 

magma, directing them up into the structurally-prepared host rocks 

in the nappes directly overlying the trend. Fault openings developed 

in most-stressed, tightly-folded and faulted parts of thrust terranes 

provided conduits for the upward movement of Tertiary intrusives 

and subsequent hydrothermal ore-bearing solutions.

(7) Ore deposits developed locally at unusually stressed sites 

in thinned, tight, arc-folded, well-faulted hanging wall portions of the 

lead edges of thrust faults that underlie (or are imbricate thrust 

faults within) individual nappes.

(8) Ore deposits in the Oquirrh Mountains nappes are zoned in 

terms of their compositions, and sized by their locations in respective 

nappes. A large concentration of zoned porphyry copper and baseand precious-metal deposits in the Bingham mining district is colocated in and about the largest altered intrusive porphyry stocks 

and dikes in the range. The intrusive magma moved directly from 

its Uinta trend source into locally-stressed, open structures in 

favorable stratigraphic units and fractured intrusives in the Bingham
42

nappe. Elsewhere in the range, smaller, mostly lower-temperature, 

geochemically less complex base- and precious-metal ore deposits, 

which are spatially co-located with smaller intrusive dike and sill 

bodies, occur in thrust-fault stressed structural and stratigraphic 

sites in nappes. These nappes overlap the thick stratigraphic 

Bingham nappe. The intrusives and hydrothermal solutions were 

unable to produce complex Bingham-size types of deposits. They 

dissapated their chemical and thermal energies by having to work up 

through the thicker, structurally less-favorable parts of the Bingham 

nappe that separated them from the Uinta trend on the western side 

of the Oquirrh Mountains. Late-stage vein and native gold ores occur 

in the cooler peripheral zone of the greater Bingham mining district. 

Disseminated ores of gold and silver also are located farther from the 

Uinta trend in the Mercur and Barneys Canyon areas.

(9) The puzzling Jurassic age of altered clay minerals in 

Paleozoic carbonate rocks found in Cretaceous-age Sevier structures 

in the Barneys Canyon and Mercur mining districts, well away from 

the Uinta trend, seems to be best explained as preservation in a 

lower-temperature environment of Tertiary intrusions and 

hydrothermal solutions. These were unable to reset the Jurassic ages 

of the clays.

(10) Alteration of carbonate rocks along veins and in replaced 

carbonate rocks in the upper levels of mines overlying the Uinta 

trend includes silicification and marblization. The deeper ores 

directly overlying the Uinta trend at Bingham and Ophir are 

associated with skarn and hornfels alteration and the replacement of 

carbonates and shales.

(11) At Bingham, copper-molybdenum ores occur mainly in 

fractures in and adjacent to the Bingham and Last Chance stocks. 

Base- and precious-metal ores occur in peripheral zones in veins and 

replacements in adjoining carbonate sedimentary rocks. 

Disseminated gold ores at Mercur occur in fractures and as 

replacements in the folded lower member of the Great Blue
43

Limestone. The base- and precious-metal vein and replacement ores 

in the Ophir Hill area seem to be peripheral to central, deep-reaching, 

thrust-related tensional faults in veins and replacements in 

numerous carbonate horizons in lower Paleozoic formations. Deposits 

in the Lion Hill and Dry Canyon areas are located on the folded and 

faulted Mississippian carbonate formations in the upper plates of 

imbricate thrusts. Apparently their ores do not persist at depth. The 

deposits at Stockton, are fault controlled in Pennsylvanian 

sedimentary rocks above the Stockton thrust and are co-located with 

dikes and plugs; they overlie a large unexplored stock.

(12) The trace of the Uinta trend zone in the Oquirrh 

Mountains is also the site of continued uplift during the Tertiary and 

Quaternary. Erosion unroofed the deposits and resulted in providing 

large concentrations of coarse clastic debris along the margins of the 

Oquirrh Mountains that overlay the Uinta trend. That was the source 

of detrital materials redistributed locally to form the Lake Bonneville 

shore-line deposits.

ACKNOWLEDGMENTS

I am most indebted to Ralph J. Roberts who conceived and 

developed the U.S.G.S. Bingham project and invited me to join it. He 

was called away to help develop a U.S. G.S. gold program before our 

field mapping was finished, entrusting me to complete studies in the 

Oquirrh Mountains. Numerous other Survey colleagues and company 

geologists cited herein have contributed greatly to the stratigraphic, 

structural, and geologic understanding of ore occurrences in the 

Oquirrh Mountains, and to the continuing growth of genesis concepts. 

I am also grateful to many investigators who preceded us in earlier 

days, also cited here, who made very important contributions to a 

growing body of knowledge about the geologic occurrence and origin 

of the Oquirrh Mountains mining districts.
44

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47

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48

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49

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50

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n. _, p. 479-481.
-40? 30'

112° 30'

Figure 1. Location of the Oquirrh Mountains and its mining districts 

in north-central Utah. Location in Utah shown in Figure 2.
52

112 C

\#

110'

Uinta Mountains .

L40 C

r

;- 38C

100 _i

Kilometers

Figure 2--ForeIand of the Sevier thrust belt (shaded), the trace of 

the inferred Uinta trend basement lineament, and the 

location of Figure 1, which includes the Oquirrh Mountains.
53

Rogers Canyon 

nappe

0°45'

- 40°30'

- 40°15'

Figure 3--Location of the Oquirrh Mountains' nappes and the

distribution of igneous rocks. Shaded nappe areas assist in 

differentiating the five nappes. Open thrust symbol 

indicates a concealed down-dropped thrust.

Qa--unconsolidated sediments, undivided. Tv--volcanic 

rocks, undivided, Ti--intrusive rocks, undivided, and 

PaI--Paleozoic sedimentary rocks,, undivided.
Farnsworth Peak Quadrangle (Tooker and -Roberts, 1971) 

Bingham Canyon Quadrangle (Tooker and Roberts, 1988- 

Stockton Quadrangle (Tooker and Roberts, 1992) 

^owe Peak Quadrangle (Tooker, 1992) 

Ophir and Mercur Quadrangles '.(Tooker, 1987)

Tooe/e

StocktonX X

Ophir

1 Pass Canyon nappe

2 Bingham nappe

3 Rogers Canyon nappe

4 South Mountain nappe

5 Fivemile Pass nappe

1 2 Kilometers

54

40°30'

40°22'30'

40°I5'

II2°22f 30 H

H2°07'30"

Figure 4 Inferred sequence and direction of movement of the

nappes that constitute the present Oquirrh Mountains, and 

the inferred location of a basement promontory (screened) 

of the Uinta trend.
55

Figure 5.--Sketch showing proposed spatial relations between a 

Cretaceous-age sole thrust fault ramping tangentally onto a basement 

buttress, the thinning of the stratigraphic section at the leading edge 

of the nappe, development of main and secondary folds, formation of 

imbricate thrusts and tension faults, and the locations of Tertiary-age 

stock, dikes, and fractured porphyry ore zone.
10

112° 07' 30"

(Inferred location of 

North ore body)

U.S. mine 

Qombincd Metals mine

Placer 

EXPLANATION 

gold deposits

Projection of vein and r

base- and precious -met

.Generalized projection o

copper deposits

Porphyritic quartz monz

core of the Bingham sto

Boundary of central cha

dispersed ore zone

.- "" . Boundary separating an 

 ' '.... .- ' from the outer sllver-lea

K

~f~ Boundary of Utah.Copp

open pit mine

Projected and existing 

"x-- stream courses

-4 f^- Anticline, locally overtu

 r Syncline, locally overtur

« I Fault, ball-bar on downt

 T T" 'thrust fault

figure 6--Surface projections of porphyry, vein and replacement, 

skar.n, and placer ore deposits in the Bingham ; nappe, 

Bingham mining district, Utah (from Tooker, 1990).
South Mountain 

nappe

Bingham nappe

57

Figure 7--Columnar stratigraphic sections of comparable parts 

of the South Mountain nappe in the Stockton 7-1/2-minute 

quadrangle (Tooker and Roberts, 1992) and Bingham nappe 

in the Bingham Canyon quadrangle (Tooker and Roberts, 

1970, 1988).
40°30'

58

40°32'30"

KILOMETERS '

Figure 8--PrincipaI fold and fault structures of the

Bingham nappe in the Bingham mining district, Utah 

(from Tookcr and Roberts, 1988).

Tertiary stocks, shaded, and Tertiary dikes solid. 

Pass Canyon nappe (stippled) includes the Dry Fork 

unit of Tooker and Roberts (1988). Bingham nappe 

includes the undivided Markham Peak and Clipper 

Ridge Members of the Bingham Mine Formation, and 

the Butterfield Peaks Formation (Tcroker and Roberts, 

1970). Open thrust symbols indicates the thrust is 

concealed by a normal fault.
g s?
112*10' 

0 .5 1 2. KILOMETERS

Figure 10 GeneraIized fold and fault structures of the Bingham 

nappe in the Mercur mining district area, after Tooker 

1997).

Qa--unconsolidated deposits, undivided. Pol includes 

Butterfield. Peaks Formation and West Canyon Limestone 

of the Oquirrh Group, undivided (Tooker and Roberts, 

1970). MI--Lovver Paleozoic, includes the Manning 

Canyon Shale, Great Blue Limestone, Humbug Formation 

and Deseret Limestone, undivided (Gilluly, 1932).
Figure ll--Generalized fold and fault structures of the Bingham

nappe in the Ophir mining district area, after Tooker, 1987). 

Qa--unconsolidated deposits, undivided. IP ol--includcs 

Butterfield Peaks Formation and West Canyon 

Limestone of the Oquirrh Group, undivided (Tooker and 

Roberts, 1970). MI--Lower Paleozoic Manning Canyon 

Shale, Great Blue Limestone, Humbug Formation, 

Deseret Limestone, and Gardison Limestone, undivided. 

 C--incIudes Lynch Dolomite, Bowman Limestone, 

Hartman Limestone, Ophir Formation and Tintic 

Quartzite.(GiIIuly, 1932)
62

.0 - XILOMETERS

Figure 12.-Generalized fold and fault structures in the eastern half 

of the South Mountain nappe, the Stockton mining district area, and 

the adjoining Bingham nappe (after looker and Roberts, 1997)

Qa--Unconsolidated deposits, undivided. DPmo-Includes Rush Lake and 

Salvation units of looker and Roberts (1992). undivided. Formations of 

looker and Roberts ''1970) in the adjoining Bingham nappe (shaded; 

include PoI-Butterfield Peaks Formation and West Canyon Limestone of 

[he Oquirrh Group, undivided. MI includes Manning Canvon Shale, and 

Great Blue Limestone, undivided.
112°07'30"

63

40°35'

(from Tookcr and Roberts

C. n ,.n ..M .,c.

Can5'On

formationa! units (shaded' Pn g r" " Park Tifv IT (-s " aded ) ; PP9--Grandcur

F« «'«"

Park 

and
64

TABLE 1. Characteristics identifying features of Oquirrh Mountains nappes

NAPPES SEQUENCE OF DIRECTION OF ENTRY AGES OF FORMATION 

EMPLACEMENT TO FORELAND

Pass Canyon First East-northeast to eastsoutheast

Permian 

(Tooker, 1998)

Bingham Second

Rogers Canyon Third

Mostly due east in 

southern part; eastnortheast across the 

buttress at north end

South-southeast

Cambrian through 

Pennsylvanian (Gilluly, 

1932; and Tooker and 

Roberts, 1970)

Mississippian through 

Permian (Tooker and 

Roberts, 1970)

South Mountain Fourth (?) Northeast Pennsylvanian and 

Permian (Tooker and 

Roberts, 1992)

Fivemile Pass Last one North-northeast Mississippian 

(Tooker, 1998)
65

TABLE 2. METAL PRODUCTION FROM THE OQUIRRH MOUNTAINS MINING DISTRICTS, UTAH

cu

(000 t)

BINGHAM

1863-1972 1 11,900

1973-1981 2 1,670

1982-1990 3 551

1991-1992 2 579

1993-19962 1,217

Total 15,917

MERCUR

1871-1950 6 0.2

1983-1990 7

1991-19922

1994-1995 2

Total

OPHIR and

STOCKTON

1870-1901 2" 101.5

OPHIR

1902-1972 2 " 4.8

STOCKTON

1902-1970 285 2.9

BARNEYS CANYON

1989-19902

1991-1992 2

19932

TOTAL PROD. 14,833.50

MC AL AC PE Zh

(000 t) (000 oz) (000 oz) (000 t) (000 t)

360 13,253 244, 4134 2.400 4 1004 4

'. 3,639 ? ". ?

27 616 811

973 7,679

>51 >8,600

>387 18,997 261,503 2,400 1,000

1,100 223 1.8 0.7

766.6

248.5

210.1

2,325

12 50 329 17

10.6 14 172 46

74 1 1 245 86

157

238

395

>387 21,087.70 253,201 3,147.80 1,149.70

HG

Flasks

3,338

?

?

>3,338

>3,338

'James (1978)

2 USGS (1883-1923, 1995-1996) and USBM (1924-1994)

3British Petroleum Co. (1986) and USBM (*1924-1993)

'The UV Industries closed the Lark and U.S. Mines underground workings in 1970, ending

the main production of silver, lead, and zinc ores (Tooker, 1990) 

5Stowe (1975) 

6Kornze and others (1985) 

7Shrier, American Barrick (1993, verbal commun.)
66

Table 3. Geologic ages of intrusive rocks in mining district areas in the Oquirrh Mountains, Utah

Bingham mining district

Shaggy Peak rhyolite 

Quartz latite porphyry 

Porphry copper mineralization 

Quartz monzonite porphyry 

Monzonite (Last Chance and 

Bingham stocks)

35.0-32.8 my 

38.8 +.0.3 (avr) 

39.8 - 38.8 

38.8

40.8 + 0.4

Warnaars and others (1978 

do 

do

Moore (1973b)

Rhyolite and rhyolite porphyry

(Eagle Hill rhyolite) 

Granodiorite porphyry

Quartz monzonite porphyry 

Monzonite porphyry

Mercur mining district 

32.4 ±0.9 

36.7 ±0.5

Stockton mining district 

38.1 

38.0 +1.1 my

Moore (1973c)

Moore and McKee (1983)

Moore (1973c)

Moore and McKee.(1983)

Moore (1973b, 1973c) dates recalculated using updated decay constant. Other dates as reported.