Geochemical Evidence for 

Possible Concealed Mineral Deposits 

Near the Monticello Box 

Northern Sierra Cuchillo 

Socorro County, New Mexico 

Geochemical Evidence for 

Possible Concealed Mineral Deposits 

Near the Monticello Box 

Northern Sierra Cuchillo 

Socorro County, New Mexico 

By Wallace R. Griffitts and Henry V. Alminas 

GEOLOGICAL SURVEY CIRCULAR 600 

Washington J 968 
United States Department of the Interior 

STEWART L. UDALL, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
Abstract ------------------------------------------------------------------------

Introduction ----------------------------------------------------------------·--

Regional geology ---------------------------------------------------------- Geology of the Monticello Box area ________________________ _ 

General geology ------------------------------------------------·--

CONTENTS 

Page 

1 

1 

1 

2 

2 

Geology of the Monticello Box area-Continued 

Rock alteration and mineralization ________________ _ 

Geochemical investigations ........................... . 

Summary -------------------------------------------------------------------··-

References cited ---------------------------------------------------------

ILLUSTRATIONS 

FIGURE 1. Index map showing location of the area sampled and of precious-metal districts in southPage 

2 

2 

3 

5 

5 

Page 

western New Mexico -------------------------------------------- ---------------------------------------------------------····-.............. _ .. 6 

2. To.pographic map showing Monticello Box area and sample localities -------------------------------------·- 7 

3. Geochemical profile showing comparison of lead contents of nonmagne.tic concentrates and 

of minus 80-mesh fractions of alluvial samples taken from the first canyon south of 

Montoya Butte ----------------------------------------------------------------------------------------------------------.................... ·····-- 8 

4. Map showing collection localities for samples containing anomalous amounts of copper, zinc, 

molybdenum, lead, or barium and loca-tions of thick calcite veins and of area·s of altered rocks -------------------------------------·------------------------------------------------------------- ............... ·····----------- 9 

5-8. Maps showing content of lead, molybdenum, zinc, and copper in nonmagnetic concentrates 

from alluvium at sampled localities, Monticello Box area: 

5. Lead __ --------------------------------------------------------------------------------------------__________ ....... _ .......... _ ....... ----------------------- 10 

6. Molybdenum ----------------------------------------------------·-------------------------------- ------------------------------------------------------ 11 

7. Zinc -------------------------------------------------------------------------------"-------------------------------------------- ---------------------------- 12 

8. Cop per ________ -----------------------------------------------------_ -------------------------------------------------------------------------------------- 13 

Ill 

GEOCHEMICAL EVIDENCE FOR POSSIBLE CONCEALED MINERAL DEPOSITS NEAR 

THE MONTICELLO BOX, NORTHERN SIERRA CUCHILLO, SOCORRO COUNTY, 

NEW MEXICO 

By WALLACE R. GRIFFITTS 

ABSTRACT 

Ores of gold and silver have long been known in 

Tertiary volcanic rocks and in Paleozoic limestone 

along a north .. trending belt near the east edge of the 

volcanic field in southwestern New Mexico. Several 

areas of altered volcanic rock in the belt may be underlain by concealed mineral deposits in the sedimentary 

rocks. Recent geochemical surveys in altered areas 

showed that mineralization is associated with the al-

.tera.tion at the north end of the Sierra Cuchillo, near 

the Monticello Box. 

The volcanic rocks in the Monticello Box area consist of latite and andesite and overlying rhyolitic flows 

and tuffs. The volcanic rocks are cut by many faults, 

most having small displacement, and they have locally 

been subjected to argillic or chloritic alteration. Large 

calcite veins, containing little metal, cut the volcanic 

rocks. Below the lowest latite may be Paleozoic rocks, 

which are not exposed in that area. The volcanic 

rocks thus may be virtually barren caprocks .that were 

altered by .solutions escaping from the ore deposits in 

the underlying limestone. 

Nonmagnetic parts of concentrates panned from 

arroyo sediments southeast of Monticello Box contain 

as much as 2 ·.percent lead, at least 0.2 percent each 

of molY'bdenum, zinc, and copper, and anomalous 

amounts of barium and silver. Tellurium was found in 

the part of the original sample that passed through an 

80-mesh sieve, but this material was otherwise much 

less useful than the concentrates in outlining the anomalies. The sources of the metals in the sediments are 

areas of chloritized rock, the fillings of small fissures, 

and perhaps some northeast-trending mineralized fault 

zones. 

INTRODUCTION 

Deposits of precious metals have long been 

known in many places in the volcanic rocks and 

in the underlying sedimentary rocks in a northand HENRY V. ALMINAS 

1 

trending belt near the east edge of the volcanic 

field in southwestern New Mexico. Nevertheless, 

widespread areas of altered rocks appear to 

have been little prospected, as they contain few 

or no prospect pits or other evidence of investigation. Thus, there remains a good chance for 

discovery of either concealed or exposed ore 

deposits in previously neglected areas. We have 

carried out geochemical surveys around areas 

of altered rock in and near the Sierra Cuchillo, especially near the north end of the range, 

36 miles northwest of Truth or Consequences, 

N. Mex. (fig. 1). The work was done as part 

of the Heavy Metals program of the U.S. Geological Survey. 

In our fieldwork we bene.fited from the 

courtesy and efforts of many people. Sam and 

Jim Cox, Victor and Frank Sullivan, and Eunice 

T. Travis allowed us on their ranches. M. Howard Milligan, a consulting geologist from Albuquerque, N.Mex., and lessee of mineral rights 

under a part of the area, helped obtain access 

to it. Patrick D. Hilliard completed geologic 

mapping in 1967 of a 51f2-square-mile area near 

the Monticello Box at the north end of the 

Sierra Cuchillo. The area of his map includes 

much of the northernmost area which we sampled and which contains the strongest geochemical anomaly found in the range, the one 

which is the main subject of this report. 

REGIONAL GEOLOGY 

The volcanic field, which is about 200 miles 

across, contains various mafic to silicic extru-
sive and dike rocks of Tertiary age and, in its 

northern part, olivine basalts of Quaternary 

age. The volcanic rocks have not yet been 

studied or mapped in detail, but fortunately 

for present purposes we need only to distinguish between the Tertiary rocks, most of which 

predate mineralization, and the Quaternary basalts, which postdate all the known mineralization of the region. The late basalts apparently 

are not present in or near the Sierra Cuchillo. 

The volcanic rocks and the underlying sedimentary rocks are cut by many north-striking 

normal faults to form a series of eastwardtilted fault blocks in the Sierra Cuchillo. These 

faults, largely unmapped in the volcanic rocks, 

and the rather high relief of the prevolcanism 

unconformity prevent accurate estimation of 

the total thickness of volcanic rocks at most 

places. 

This region was selected for study because 

of three geologic features that are found near 

the eastern edge of the volcanic field. The most 

important of these, shown in figure 1, is a broad 

north-trending belt of precious-metals districts, 

which occur in part in windows through the 

volcanic rocks and in part in the volcanic rocks 

themselves. The ore metals of this belt differ 

markedly from those in a belt of nonsulfide deposits of manganese, barium, cerium, and fluorite to the east, across the Rio Grande. Second, metal deposits containing gold and (or) 

silver are reported from Paleozoic rocks in 

nearly all areas in which these rocks are exposed. 

Third, widespread but localized hydrothermal 

activity is indicated by hydrothermal alteration 

of the volcanic rocks. It seems plausible that 

this hydrothermal activity was in places accompanied by metallization and also that any 

resulting ore deposits would be similar in composition to those in other districts in the belt. 

The mineralization might well produce ore deposits in the sedi,mentary rocks with only traces 

of metal in overlying volcanic rocks that were 

altered by escaping, nearly spent solutions. 

GEOLOGY OF THE MONTICELLO BOX AREA 

GENERAL GEOLOGY 

The Monticello Box area, as used here, is the 

area underlain by volcanic rocks that extends 

southeast for about 4 miles from the Monti2 

cello Box on Alamosa Creek (fig. 2). The area 

is bounded on the west by a gravel-filled basin 

and on the east and north by Alamosa Creek. 

Hilliard ( 1967) reported the following lithologic units (arranged in approximate order of 

increasing age): gravel, flow-banded rhyolite, 

massive rhyolite, rhyolite tuff, sedimentary 

rocks, andesite and latite flows, and latitic tuff 

and coarser pyroclastic rocks. 

The andesite and latite flows are the most 

widespread volcanic unit in the area. They are 

commonly dark greenish gray, and both color 

and luster depend upon the degree of alteration. 

The unit rests upon about 600 feet of latitic 

tuff and pyroclastic rocks which are exposed 

along the east side of the area. These two units 

resemble the "andesitic breccia" and overlying 

"andesitic and latitic lavas and tuffs" which 

Jahns ( 1944) found at the base of the volcanic 

sequence at Iron Mountain, about 7 miles to the 

southwest. Therefore, sedimentary rocks may 

not be far below the latitic tuff along Alamosa 

Creek. The andesite and latite flows are overlain by rhyolite tuffs and flows. An increase 

southward in the amount and contortion of 

layered rhyolite suggests that a volcanic vent 

lies in that direction. 

Hilliard found dikes of latite, porphyritic 

andesite, and basaltic andesite and of quartz 

latite equivalent to the rhyolite mapped by 

Jahns (1944) at Iron Mountain. One small 

plug of quartz monzonite is in the NW% sec. 8. 

Many faults and fractures, most having only 

small displacement, cut the volcanic rocks. Most 

faults trend northeast, some trend northwest, 

and a few trend in other directions~ Displacement of at least 700 feet along one northeaststriking fault accounts for the constriction of 

the Alamosa valley at the Monticello Box. Many 

of the faults predate mineralization, inasmuch 

as they contain veinlets of quartz, fluorite, or 

calcite. 

ROCK ALTERATION AND MINERALIZATION 

The most conspicuous result of minE}ralization 

in this area is the thorough argillization of the 

volcanic rocks near the northwestern edge of 

the area sampled. The sides of a draw there 

consist of chalky-white, brown, or red masses 

of clay. Kaolinite is the most widespread product of alteration, and Hilliard ( 1967) also 
found alunite and montmorillonite. Eastward 

and southward the alteration decreases in intensity and changes in character. The rocks 

remain firm and coherent but are stained red 

or brown with iron oxides and contain chlorite, 

a general type of alteration that is extensive in 

sec. 5 and decreases eastward and southward. 

Epidote was seen along fractures in outcrops 

near the western boundary of sec. 5, in the 

northeastern corner of sec. 7, and near the 

southern edge of sees. 16 and 17. All these 

localities are near the western or southern 

edges of the metal anomaly outlined in figure 2. 

Less conspicuous epidote in the interior of 

the anomaly-perhaps in a disseminated state 

-is attested to by its presence in many panned 

concentrates, even where it was not seen in the 

field. 

Only one metalliferous vein has been explored in this area, at the Taylor prospect in 

sec. 5 (fig. 4) where several tons of oxidized 

ore containing copper, lead, silver, and zinc are 

reported to have been recovered from a quartz 

vein that is a few hundred feet long and 5 feet 

in maximum width. Other veins of quartz and 

outcrops of lead-rich gossan which we examined 

in the area have not been disturbed. Fluorite 

and -barite are widespread in the strongly and 

moderately argillized rock south of Monticello 

Box and can be panned from wash sedim.ent in 

most places. Fluorite cubes were found in float 

in an area of moderately altered rock in sec. 8. 

The general pattern is one of widespread mineralization without evidence of a minable deposit at the surface. 

Calcite forms veins 5-15 feet thick near the 

western edge of sec. 5 and near the middle of 

sec. 7 (fig. 4). In most veins the mineral grains 

do not exceed one-half inch in diameter, but 

a vein that crops out about one-half mile south 

of Allison well in sec. 7 is much coarser, having grains several inches across. These large 

calcite veins contain only traces of base metals 

and silver. East of the above-mentioned veins 

calcite is less conspicuous and forms thin veinlets, usually accompanied by quartz, that are 

a fraction of an inch to a few inches in thickness. The size and number of calcite veins increase at the southern edge of the anomaly, 

and calcite-quartz and calcite-chalcedony veins 

are conspicuous in the southernmost canyon 

3 

sampled. Calcite and epidote are thus similar 

in distribution, both minerals occurring most 

conspicuously near the southern and western 

edges of the anomaly. 

Calcite is, of course, a common component of 

hydrothermal veins, both metalliferous and barren. Hence, the many minor veins in the interior of the anomaly are perhaps of little sig .. 

nificance. The massive ve,ins along the western 

margin of the anomaly are different in texture 

and presumably in origin. They are in the 

most intensely mineralized parts of the area, 

between the intensely argillized rocks to the 

west and an area to the southeast that is par .. 

ticularly high in copper (fig. 4). The calcite 

n1ay represent a waste product of mineralization of limestone below the volcanic rocks. 

A deposit of an entirely different type, perhaps not related genetically to the base-metal 

mineralization, was found by M. Howard Milligan in 1961 about one-half mile south of Monticello Box. In this deposit, bertrandite (a hydrated beryllium silicate) has been introduced 

into faulted volcanic rocks. Beryllium was detected in substantial amounts in samples of 

alluvium derived from the area of Milligan's 

prospect but was not found elsewhere in the 

Monticello Box area. 

GEOCHEMICAL INVESTIGATIONS 

The objectives of the geochemical survey 

were to determine if there is evidence of metallization associated with the hydrothermally altered volcanic rocks and then, if such evidence 

was found, to determine the extent of the affected area. The most rapid and economical 

method appeared to be a moderately detailed 

sampling of the sediment from the canyons and 

arroyos, all of which are usually dry. A sample was taken at the mouth of each canyon at 

its junction with Alamosa Creek or with the 

draw in argillized rock south of Monticello Box. 

This reconnaissance was followed by the sampling of each tributary of each .canyon that contained anomalous metal. As is evident in figure 

2, some tributaries are nearly a mile long and 

collect alluvial material from large areas, 

whereas others are no more than small depressions in the walls of the canyons. 

Two samples were taken at each location. The 

first sample, consisting of about 1lb (pound) of 
sediment, was sieved to minus 80-mesh and analyzed by spectrographic and other methods. 

The second sample, consisting of about 10 

lb of sediment, was panned and the concentrate 

was cleaned with bromoform. Ilmenite and 

magnetite were· removed and the remaining material was split with a Frantz Isodynamic Separator at a 1-ampere setting. Visual examination of the nonmagnetic fraction prior to spectrographic analysis showed its prominent components to be limonite, fluorite, barite, zircon, 

rutile, sphene, and several unidentified lightcolored minerals. Wulfenite (PbMoQ,) and 

lead-bearing limonite are the only minerals we 

found that are rich in ore metals. Cerussite 

and molybdenum-bearing limonite were sought 

but not found. 

Each portion of the samples was analyzed by 

semiquantitative s p e c t r o g r a phic methods 

(Ward and others, 1963). Supplementary determinations for gold, tellurium, mercury, antimony, and acid-soluble lead were made on selected samples. 

These analyses were made by our colleagues 

Arnold Farley, Jr., Elwin Mosier, J. M. Nishi, 

John Watterson, Thelma Harms, R. L. Turner, 

E. P. Welsch, Eliz,abeth Martinez, Jerry Motooka, K. C. Watts, R. F. Hansen, M. S. Richard, W. L. Campbell, R. L. Miller, and T. A. 

Roemer. 

The most informative determinations were 

those made by spectrographic analysis and by 

visual examination of the nonm,agnetic concentrates. Tellurium determinations made on 

minus 80-mesh sample material effe·ctively distinguished mineralized from unmineralized terranes, but other determinations on the s~ame 

material were of much less ~alue. The anomaly 

at Monticello Box might even have escaped 

notice if the only data available were of metal 

contents of minus 80-mesh material. The 

marked enhancement of contrast between areas 

with anomalous and background metal contents 

which we obtained by analyzing concentrates 

is illustrated in figure 3. 

Figure 4, a general compilation of ~available 

geochemical data on copper, ~inc, molybdenum, 

lead, and barium, shows that the anomaly as a 

whole is not delimited by a single element. In 

most places where one of the five elements is 

present in anomalous amounts, at least one 

4 

other element also occurs in anomalous 

amounts. 

The background values for copper, zinc, molybdenum, lead, and barium used in compiling 

figure 4 were set high enough to minimize the 

effect of erratic variations that result from the 

widely varied litho logy of the volc'anic rocks. 

Each lithologic type naturally has its own local 

background value for each metal and we have, 

in effect, taken the highest of these local background values as the area background. Less 

conservative-lower-background values can be 

determined from figures 5 through 8 if a more 

complete distribution pattern is desired. 

A comparison of the maps for each element, 

figures 5 through 8, shows that anomalous copper values extend farther north than south of 

the main concentrations in the northern parts 

of sees. 8 and 9, that anomalous zinc and lead 

values extend farther south than north, and 

that molybdenum is somewhat less widely dispersed than lead and copper. The apparent 

immobility of molybdenum and the association 

of this metal with lead result at least partly 

from its presence in the soils as molybdate at 

a time when cations which form insoluble molybdates are also present. 

The high metal values in alluvium are not 

closely related spatially to faults, although a 

few northeast-trending faults have been found 

in drainage basins containing metal-rich allu- · 

vium. Slightly to moderately altered rock seems 

more consistently to yield metalliferous debris 

than do faults of any trend. 

Tellurium was found in many samples in the 

northwestern part of the anomaly, generally in 

amounts of tenths of parts per million. Silver 

was found in many lead-rich samples. Gold, 

on the other hand, was detected in only a few 

samples and its concentration was less than. 

0.02 ppm (part per million) in most samples. 

Acid-soluble lead content of concentrates of 

minus 80-mesh material varies sympathetically 

in a general way with molybdenum and thus 

provides a rough measure of the molybdenum 

content. The other nonspectrographic determinations were less useful. Antimony was not 

detected in any sample; mercury was found 

only in very low concentrations, and the range 

in values was too slight to be useful. Visual examinations of heavy-mineral concentrates can 
be used to guide sampling and to help interpret 

or explain the geochemical data. 

SUMMARY 

Anomalous amounts of lead, zinc, copper, molybdenum, and barium have been found in altered volcanic rocks in the Monticello Box area. 

The geochemical anomaly combined with other 

regional and local geologic features suggests 

that concealed mineral deposits may be present 

in underlying Paleozoic carbonate rocks. The 

regional features of most significance are the 

presence of gold or silver in most known deposits in a broad belt that encompasses the 

Monticello Box area and the very widespread 

distribution of ore in limestones of Paleozoic 

age--ore has been found in most places where 

the limestones are exposed in windows through 

the volcanic rocks. Calcite was removed during 

replacement of the limestone by ore and gangue 

minerals. Presumably it was transported upward, through the volcanic rocks, by the oreforming solutions after they had been depleted 

of most of the metal ions. The volcanic rocks 

undoubtedly were hydrated during the process. 

On a local scale we found several features 

that correspond to those seen or inferred in 

neighboring districts. The volcanic rocks are 

extensively and locally intensely altered; ore 

5 

metals are in minor fractures and dispersed in 

altered rock. Thick calcite veins in the most 

strongly mineralized part of the area suggest 

replacement in the underlying limestones. We 

infer that the total thickness of the volcanic 

rocks may be only a few hundred feet. The 

weak lateral zoning of metals at the surface 

could then be explained best as a reflection of 

zoning in the underlying formations. 

Neither the thickness of the volcanic rocks 

nor the exact distribution and nature of mineralization in the underlying sedimentary rocks 

could be determined from surface studies, and 

further investigation of these subjects and of 

the potential for concealed ore bodies should 

include geophysical studies and exploratory 

drilling. 

REFERENCES CITED 

Hilliard, P. D., 1967, General geology and beryllium 

mineralization near Apache Warm Springs, Socorro County, New Mexico: Socorro, New Mexico 

Inst. Mining and Technology, M.S. thesis, 58 p. 

Jahns, R. H., 1944, Beryllium and tungsten deposits of 

the Iron Mountain District, Sierra and Socorro 

Counties, New Mexico: U.S. Geol. Survey Bull. 

945-C, p. 45-79. 

Ward, F. N., Lakin, H. W., Canney, F. C., and others, 

1963, Analytical methods used in geochemical exploration by the U.S. Geological Survey: U.S. Geol. 

Survey Bull. 1152, 100 p. 
I 

--

X 

Gc, X rX 

~ 

I 1 

I 

ANA 

I 

I j .xl U N A 

I X I 

*'""'"*"""- ~ _L HIDALGO XL--~---·--- --

x : 

I ' 25 0 25 50 MILES i : ~' ~~~~~~'------~'------~' 

AREA 

~ OF THIS 

MAP 

_______ _j 

FIGURE 1.-Index map showing location of the area sampled and of precious-metal districts (X) in southwestern New Mexico. 

6 
APPROXIMATE MEAN 

DECLINATION, 1968 

FIGURE 2.-Map showing Monticello Box area and sample localities. Heavy dashed line is approximate limit 

of geochemical anomaly. Base from U.S. Geological Survey map of Montoya Butte quadrangle, 1964. 

7 
WEST EAST 

~o.ooor-~~~~~~,~~~----~.-~--+----4----~----+---~----~----+---~ 

2o,ooor----+-r_,~----~---+----4-~~~---+----4-----~---+----~ 

\ 

1

\ i\ V\o 00 4000 FEET 

I I I 

I I I /L-1\ I _ ___.,JI __ ........_ __ J...._ '----~' 

I I I 10,000 r----+---i-+--+---.....;~~-+-!---l----:/f--+-----~,r----+----4-----+------+---~ 

~ / \ 

"-..V \. 

I \ 

5000~--1-~-1----+--~+---~----~-~\~--~---4----4---~ I \ 4000r----+--~-+----1~~-+----+-----~--~----+-----~---+----~ 

\ ~ 300or----+~H-4---~~-+-+----4-----~---+~~\~----~----+---~ 

2000r----+-+-r4----+~~-+----4-----~---+--~4-----~---+----~ 

\ \&---~-& z \ ~ 

§ 10001~--_,-r--~---r+---~~4-----~---+----~----~---+----~~~--~ ...J 

~ 

\ ~ \ ~ I 

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~ 50r--,_---+---~--4--\~+-~'--~'~~~~~4---+---~-~ ...J \ i \ 7 

:::====:====:====:====:==:\:::i;~==:=:\:\j::v:===:====:====:====: \ I ,/ 20~--~----~----L---~----~~~--~----~--~----~----~--~ 

200 

100 

90 

80 

70 

60 

50 

40 

30 

j 

l 

7 

j 

7 

l7 

" { \ 

\ 

\.1\ 

.A 

I \ 1\ 

/ \ \ 

v 

NONMAGNETIC CONCENTRATES 

V' I-t ---- ~, 

/ I ~ L>( 1\ 

/ rt ! f\. 

/ I \ I '· _A v / \ 1/ '\ ' 

r-,; I \ ' ~ '\. 

\~/ /' L/ \.l 

\ I " \V 

MINUS 80-MESH PART OF ALLUVIUM 

FIGURE 3-Comparison of lead contents of nonmagnetic concentrates and of minus 80-mesh fractions of alluvial 

samples taken from the first canyon south of Montoya Butte. Solid line connects values for samples taken 

from the main canyon. Dashed line connects values for samples taken from tributaries to the main 

canyon. 8 
R. 7 W. 

.. Q 

·.·.·~-

.. ,~ 

...... J ~ . ··:,:::. \ ...... 

'\.~)7 • 

18 

~ • 

. . . • 

0 

0 ©> 

@@:J 0 

v 5 

... ·::::· Taylor • ·.:.::::.:.:'>!- ·. prospect 

. .... ::::•.:: ::::::. . .. :.:::-::::>f;\ ····.·.~~· ............. &··· ~ .... 

©>\ 

\ 

17~-

~ .... :-~·. ·o ······•· .... • .......... • ','.'."!', 

9 

·•··· :::::a··:· .. 

. . 

0 

" \ 

\ 

\ 

' ~ I 

@ I 

I 

. \ 

\ 

\ . \ 

• ·• 

0 

v v 

3 

10 

0 

0 (li 0 

r-----------------~------------~--+--~v~------------ + v 19 

0 

20 

1 MILE 

0 

At least 100 ppm copper 

0 

At least 200 ppm zinc 

0 

At least 5 ppm molybdenum 

• 

At least 200 ppm lead 

No anomalous metal 

. . 0 . 21 .. 22 .. 

vy 

Thick calcite vein 

Line shows strike, where known 

Boundary of area in which most 

samples contain at least 5000 

ppm barium 

········· ·········· ········· Altered rocks 

In part from Hilliard (1967) 

T. 

8 

s. 

I T. I 9 

I s. 

I 

I 

I 

I 

I 

I 

I 

I 

I 

33° 

3·2' 

I 30" 

I 

I 

I 

FIGURE 4.-Collootion localities for samples containing anomalous amounts of copper, zinc, molybdenum, lead, 

or barium and locations of thick calcite veins and of areas of altered rocks. All metal values were determined on nonmagnetic heavy concentrates. 

9 
X 

fJ-.. 

107°35' R 7 W 

I I 

X 

32 . X 0 33 

X 

X -A< XX X 

0 =X . X • ~ 0 

~~00~ + 

•X X 

X X 

X X 0 

X c9 0 

x

0 0 fio 0 Ox 0 

~ ' 5 0 o4 

X 0 

J (D o o Oo 

6 • ~ . .~ 

0 0 

xo ~ 

0 0 

0 7 

~ 

Oo 

X 

Q9 

18 

19 

APPROXIMATE MEAN 

DECLINATION, 1968 

X 

0 

• 

~ 

~~ 

"" -w 

0 

t ~ 

i 

X 

- v 

0 

~~ '" 00 

0 

c9J8 8 9 

0 

• 0 & ~. ~ I LQ ~ • u 

0 0 

xO 

17 16 

X 

X 

X 

X 6~ 0 o. + 

20 21 ox 

I 

Lead, in parts per million 

• 10,000-> 20,000 

~ 1000-7000 

0 200-700 

0 100-150 

X 10-100 

< 10 

107"32'30" 

~ I 

I 

I 

I 

I 

·-·-·-·-·-·r 

0 I 

0 I 

~ 3 I 

I 

I 

I + ; 

oo 0 I 

I 

0 I 

• 10 

~ X I 

I 

I tiP 0 I 

~ . X ~ 0 

Q15 X 

0 X 0 X 

~ 

-+ 

X 

~X X . X 22 

I 

2 MILES 

FIGURE 5.-Lead content of nonmagnetic concentrates from alluvium, Monticello Box area. 

10 

T. 

8 

s. 

T. 

9 

s. 

33° 

32' 

30" 
! I 

X 

32 

R 7 W 

I 

I 

I 

I I X 0 I 

I 

I 

I 

I 

33 

. . 

! 

I 

I 

107"32'30" 

I 

T. 

8 

s. • X i~---L·~.~--------~~~-------· 

t---··_·_· ·-__,..~r--·~_r: X." 5 ~ ~ X 0 8 0• ~40---,.-X---J'_X _____ 3 ______ r 

6 

. . . * • . . . . . . I ~ ~ • • I 

X ~~ 11 I r---~------~~~---------------~1L--------------+ : 

o. o· I 

I 

0 X I 

7 

. 

. 9 

X 

~.· 33° i 32' 

30" 

10 

. . . I I 

I • • • 0 <:]< • 0 

~-------·~·~·--~~:--+----o~~~~~-~8~~~~.---·~~--~6=--~o_·~-----------------,· 

18 

19 

J:~~~·l ~ ~ 0 "' z () .., ;:: 

::> "' 

1-"' (!) "' 

; APPROXIMATE MEAN 

DECLINATION, 1968 

X 

17 

20 

l 

Molybdenum, in parts per million 

• 300-2000 

~ 100-200 

0 50-70 

0 10-30 

X 5-7 

< 5 

0 

X 0 0 

FIGURE 6.-Molybdenum content of nonmagnetic concentrates from alluvium, Monticello Box area. 

11 
107"35' R. 7 W. 107"32'30" 

I I ! I I I I 

~ I 

I • 33 I I 

I . . I . I I 

I . .. 

. .. I 0 ~l I • • ~ ae • 0 . • .. . . -+ • . 0 • . .. .. . . r-------------T 

• . . . • • . • I • . . . . I . • .. • • • • . . . • . • 5 • . . .4 -4 . . 3 . . I 

• . • . I 

. I . • 

6 ' 0 •• . I 

. . . • . I . • . ·o. ~ . . • a i + V" : 

• . I . . 0 . . . eo .ocg 00 I 

. 0 0 . I . . . It . . 7 8 . 9 10 ~ • ~ . . . .. . . f I • . I 

. . . 

' . • I . . . •• • 0 . - ••• . 0 . I• . - • •• I 

. . ~ • c . . 0 . 

18 cP .15 17 16 . • . 0 . . • . . . . • • • . . . . . a + + • . . . 

. . . 19 20 21 .. . 22 

I I 

13• 0 1 2 MILES 

~· ~ g Zinc, in parts per million 0 

z 

.. 

:> 

" • 1.000-2000 .... 

APPROXIMATE MEAN 

DECLINATION, !968 0 500-700 

0 200-300 

<200 

FIGURE 7 .-Zinc content of nonmagnetic concentrates from alluvium, Monticello Box area. 

12 

T . 

8 

s . 

T . 

9 

s . 

33" 

32' 

30" 
oo 

0 X 

X 

6 

7 

0 

0 

107°35' 

I! I 

0 

0 

~~ 0 

0 

32 

X 

0 

X 0 

0 0 • X 

R 7 W 

33 

0 

0 

• 0 0 • 

9 

0 

X 

107°32'30" 

I 

T. 

8 

s. --------------T T. 

I 9 

0 

3 

X 

0 

0 10 

• 

I 

I 

I 

I 

I 

I 

i 

: 

I 

I 

I 

s. 

~.· 33° i32' 

30" 

I 

I 

0 I 0 O 0 X £l 0 

r-------~QP~~~~v~~------------~o~~~~~~x~ft~~O~---~~~----------------~· ~X 0 ~ 

X 

0 0 

X 0 

18 17 16 x15 X 

X 0 X 

0 

X 0 

0 XO X 

r---------------~------------~·L--t--~~-----------+-----------------H 

19 

f/

1~·-l: 

J: ,_ 

z 

~ ~ 

"' :::l 

0: 

... ... 

APPROXIMATE MEAN 

OECLINATION, 1968 

0 

20 21 ox 

I 

1 

Copper, in parts per million 

• 500-2000 

0 100-300 

0 50-70 

X 5-30 

<5 

x\ 0 . X 

2· MILES 

FIGURE 8.-Copper content of nonmagnetic concentrates from alluvium, Monticello Box area. 

GP 0 865·485 

13 

22 

I