Geochemical, Halos in the 

Silver City Mining Region 

and Adjacent Areas, 

Grant County, 

New Mexico 

GEOLOGICAL SURVEY BULLETIN 15.34 

ERRATA 

U.S. GEOLOGICAL SURVEY BULLETIN 1534 

Geochemical Halos in the Silver City 

Mining Region and Adjacent Areas, 

Grant County, New Mexico 

The map on p. 56, now labeled figure 15, actually 

shows the distribution of gold (nonmagnetic fraction) 

not silver (magnetic fraction). The map on p. 58, now 

labeled figure 16, actually shows the distribution of 

silver (magnetic fraction) not gold (nonmagnetic fraction). The figure captions, text references to the figures, and the table of contents are correct; only the 

corresponding maps have been reversed. 

Geochemical Halos in the 

Silver City Mining Region 

and Adjacent Areas, 

Grant County, 

New Mexico 

By KENNETH C. WATTS, JERRY R. HASSEMER, and DAVID F. SIEMS 

GEOLOGICAL SURVEY BULLETIN 1534 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1984 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress cataloging in Publication Data 

Watts, K. C. 

Geochemical halos in the Silver City mining region and adjacent areas, Grant County, New Mexico. 

(Geological Survey Bulletin 1534) 

Bibliography: 85 p. 

Supt. of Docs. no.: I 19.3:1534 

1. Geochemistry-New Mexico-Grant County. 2. Ore deposits-New Mexico-Grant County. 

I. Hassemer, Jerry R. II. Siems, David F. III. Title. IV. Series. 

QE75.B9 no. 1534 

[QE515] 

557.3s [553.4'09789'692] 81-607560 

ACR2 

For sale by the Branch of Distribution, U.S. Geological Survey 

604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Geologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Geochemical investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Sample medium and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Analytical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Data reduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Geochemical halos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Lead, copper, and zinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

Bismuth and tungsten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Molybdenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Silver and gold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Barium and manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Tin.......................................................... 21 

Vanadium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Selection and description of window areas. . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Comparison of heavy-mineral fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Comparison of geochemical halos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Relative exposure level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 

Conclusions.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

ILLUSTRATIONS 

[Figures 3-22 follow text] 

Page 

FIGURE 1. Index map showing location of study area . . . . . . . . . . . . . . . . . . 3 

2. Generalized geologic map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3-22. Geochemical maps showing distribution of: 

3. Lead, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . 32 

4. Lead, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

5. Copper, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . . 36 

6. Copper, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . . 38 

7. Zinc, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . 40 

8. Zinc, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 

9. Bismuth, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . 44 

10. Tungsten, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . 46 

11. Tungsten, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . 48 

,III 
IV CONTENTS 

FIGURES 3-22. Geochemical maps showing distribution of: Page 

12. Molybdenum, nonmagnetic fraction . . . . . . . . . . . . . . . . 50 

13. Molybdenum, magnetic fraction . . . . . . . . . . . . . . . . . . . 52 

14. Silver, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . 54 

15. Silver, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . . 56 

16. Gold, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . . 58 

17. Barium, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . 60 

18. Barium, magnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . 62 

19. Manganese, nonmagnetic fraction .. •. . . . . . . . . . . . . . . . 64 

20. Manganese, magnetic fraction . . . . . . . . . . . . . . . . . . . . . 66 

21. Tin, nonmagnetic fraction . . . . . . . . . . . . . . . . . . . . . . . . 68 

22. Vanadium, nonmagnetic fraction . . . . . . . . . . . . . . . . . . 70 

TABLES 

[Tables follow text] 

Page 

TABLE 1. Location and description of window areas . . . . . . . . . . . . . . . . . . . 72 

2. Ratio of fraction magnitudes for selected metals. . . . . . . . . . . . . . 73 

3. Comparison of element magnitudes for selected metals . . . . . . . . 7 4 

4. Additive ratios of element magnitudes. . . . . . . . . . . . . . . . . . . . . . 85 
GEOCHEMICAL HALOS IN THE SILVER CITY 

MINING REGION AND ADJACENT AREAS, 

GRANT COUNTY, NEW MEXICO 

By KENNETH C. WATTS, jERRY R. HASSEMER, and DAVID F. SIEMS 

ABSTRACT 

An alluvial heavy-mineral survey of the Silver City mining region and adjacent 

areas, Grant County, N. Mex., was completed in 1976. Geochemical data resulting 

from this survey show areas of anomalous metals that conform to geologic control. 

Anomaly patterns indicate that some of these areas may contain additional economic 

mineral deposits; other areas probably constitute zones of subeconomic, dispersed 

concentrations of metals that nevertheless record the regional pathways along which 

mineralizing solutions were channeled and ore metals and gangue mineral products of 

hostrock alteration were deposited. 

The geochemical maps suggest some new exploration targets, one of the most pro· 

mising of which is the area surrounding Fleming Camp, an old silver district of 

modest production history. Geochemical evidence at Fleming Camp suggests the 

presence of a buried intrusive cupola that has caused skarn development and perhaps 

controlled associated metallization of which the silver deposits are a part. This inference is based on comparison of the geochemical anomalies at Fleming Camp with 

those in the Pinos Altos district where large tonnages of skarn-associated replacement deposits are known. Similarities in metals present, in anomaly strength, and in 

areal extent indicate that deposits of similar genetic origin to those at Pinos Altos 

may exist at depth near Fleming Camp. 

The geochermcal characteristics of 11 areas were compared using U.S. Geological 

Survey STA TPAC computer programs. The relative effects of weathering, and 

amounts of pyrite as reflected by amounts of supergene dispersion, and the extent to 

which the chalcophilic elements are fixed by secondary iron-manganese oxides were 

compared between areas by using a ratio of fraction magnitude of the iron and 

manganese oxide rich, heavy-mineral magnetic component to that of the iron and 

manganese oxide poor nonmagnetic component, which is usually more rich in primary 

and secondary ore minerals. The ratio provides an index that allows the areas to be 

compared and ranked relative to the importance of supergene processes. 

Possible levels of erosion relative to inner metal zones were assessed in several areas 

by using an element magnitude (EM) measurement (element intensity x size halo 

area), which provided an index of the importance of the supraore (usually peripheral 

metals in a zonation sequence) in each area in relation to the importance of subore 

(usually inner metal zone) metals based on the additive ratio of the EM values: (Pb + 

Ag + Ba)/(Cu + Mo + Bi), in the mechanic-ally dispersed ore mineral (nonmagnetic) 

fraction. The ranking derived from using these ratios placed the erosion levels of the 

Georgetown and Fleming Camp districts above those of the inner, possibly main ore 

zones, on the basis of the large supraore component, and placed the erosion levels at 

the Fierro-Hanover district near the roots of the inner ore zone of its metal system, as 

suggested by a dominant subore component (low ratio). All other windows were in sequence between these extremes. 

1 
2 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

INTRODUCTION 

The numerous geochemical anomalies detected in the Silver City 

mining region and adjacent areas, Grant County, N. Mex., are 

discussed in this report, and the possible significance of the 

anomalies is evaluated. The anomalies (also called "halos"; see 

description following) were noted in 1976 during a geochemical study 

in eight contiguous 7Y2-minute quadrangles near Silver City. A 

statistical summary and listing of the analytical data from this 

sampling program are contained in Open-File Report 78-801 by 

Watts, Hassemer, Siems, and Nishi (1978b). 

A halo is defined in this report as an anomalous geochemical pattern of variable symmetry that relates to either an economic mineral 

deposit or to epigenetically dispersed metals in subeconomic but 

anomalous concentrations. Many of the halos discussed in this report 

are asymmetrical or linear in shape because they often reflect metals 

localized by linear, structural weaknesses in the rocks, such as faults, 

dikes, and fractures. Sometimes the linearity and asymmetry are not 

attributable to observable features on the surface, indicating the 

presence of causative geologic features in the subsurface. Common 

practice reserves the use of the word halo to those geochemical 

anomalies associated with economic mineral deposits and has implied 

that halos of this type are at least nearly symmetrically disposed 

about the deposits. A metal dispersion halo according to common 

usage can be of several types: It may be called ''primary,'' if it formed 

at the time of hypogene metallization; "leakage," if it developed in 

overlying rocks during or shortly after a mineral deposit is formed; or 

"secondary," if it resulted from the supergene destruction of a 

mineral deposit (Beus and Gregorian, 1977; Hawkes and Webb, 1962; 

Levinson, 1974). All these types occur in the Silver City area, and 

many of them probably conform and overlap with each other; but 

because additional factors contribute to the formation of an economic 

mineral deposit, beyond the introduction of metals by mineralizing 

solutions, all halos need not be related to deposits of ore grade. The 

halos described in this report show only that many metals were 

epigenetically introduced over broad areas and were made available 

for economic accumulation, whether or not favorable environments 

were present. 

The area of study, which is between lat 32°45'00" N. and 33°00'00" 

N. and long 108 °00 '00 II W. and 108 °30 '00 II W. in Grant County, N. 

Mex. (fig. 1), is in general subdivisible into two geologic and 

physiographic areas. Portions north of about lat 32 °52 '30 11 N ., which 

are relatively high in elevation, are underlain by middle Tertiary 

volcanic rocks. Areas south of this latitude are referred to as the 
INTRODUCTION 3 

10 20 30 40 50 KILOMETERS 

10 20 30 MILES -

FIGURE I.-Index map showing location of study area. 

Silver City mining region; here, erosion has removed the middle Tertiary volcanic cover and has exposed rocks ranging in age from 

Precambrian to early Tertiary. The Silver City mining region, which 

is highly mineralized, contains several exposed, economically signifi-
4 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

cant metal-producing districts. They include (1) the disseminated and 

replacement copper deposits at Santa Rita, (2) the iron-zinc skarnreplacement deposits at and between Fierro and Hanover, (3) the vein 

and vein-replacement zinc-lead-copper-silver deposits at Central, (4) 

the vein-replacement silver deposits at Georgetown, (5) the goldsilver vein and skarn-replacement zinc-copper-lead deposits of Pinos 

Altos, (6) the vein-replacement silver deposits at Chloride Flat, (7) the 

vein-replacement manganese-iron deposits at Boston Hill, and (8) the 

vein-replacement silver deposits at Fleming Camp. 

In the terrain north of the Silver City mining region, the middle 

Tertiary volcanic cover obscures whatever Laramide mineral 

deposits may exist in the older rocks below, though younger, midTertiary deposits may occur within or below the volcanic pile. It is 

also possible that the imprints of waning stages of Laramide 

metallization may be present. The volcanic terrane afforded an opportunity to test methods of exploring with geochemistry for covered 

mineral deposits beneath and within a volcanic pile adjacent to a major mineralized region of similar history but with a deeper exposure. 

There may have been some success. 

A particularly striking characteristic of the geochemical anomaly 

patterns both within the mining region and the volcanic terrane is 

their continuity, in the case of some metals, transecting all lithologic 

boundaries, and the erosional boundary between the two contrasting 

terranes. Geochemical patterns in the Silver City mining region suggest that epigenetic metallization took place in a vast, interrelated 

network controlled by zones of faults and perhaps closely spaced fractures, the dominant trends of which are north, northeast, and northwest. The fact that linear anomaly patterns are more numerous than 

known faults, but similarly oriented, indicates that they may provide 

a more complete representation of the hydrothermal conduit system 

than does the mapped geology. Dispersed metallization is defined by 

Beus and Grigorian (1978, p. 281) as noneconomic concentrations of 

elements and minerals that are formed as a result of ore-fluid effects 

on enclosing rocks. Many of the geochemical patterns in the study 

area probably reflect dispersed metallization, but they nevertheless 

appear to record solution pathways, which in itself can be a useful exploration tool. Where these dispersed metallizations encounter 

favorable environments, however, economic concentrations can 

develop. Empirical observations indicate that some of the most 

favorable environments are found where the geochemical anomaly 

patterns intersect, which in many cases also corresponds with areas 

of known deposits. The intersections of geochemical patterns probably record zones within the network of conduits where regional dilational forces allowed more efficient mineral deposition. 
GEOCHEMICAL INVESTIGATIONS 5 

The variety of plutonic rocks, many with associated ore deposits, 

and a rather well-defined structural pattern that seems to have controlled ore deposition make the study region ideally suited for comparing selected areas on the basis of geochemical characteristics; the 

purpose being that comparisons can be used to investigate methods 

of assigning sequential exploration priorities to geochemical 

anomalies, using as criteria types of deposits potentially present and 

erosion levels that probably exist relative to inner or main ore zones. 

ACKNOWLEDGMENTS 

Several members of the U.S. Geological Survey contributed to this 

study in both the field and the laboratory. In particular, the efforts of 

James Nishi, who performed some of the spectrographic analyses, 

Richard Babcock, and Dwight Rhiner, who assisted in laboratory and 

field, are greatly appreciated. We also gratefully acknowledge the 

friendly cooperation extended by numerous landowners in the area. 

Special acknowledgment is made to D. H. Richter and G. B. Gott 

whose very helpful comments and constructive criticism improved 

this report considerably during the review process. 

GEOLOGIC SETTING 

The older rocks exposed south of lat 32°52 "30" N. consist of Proterozoic Y granite, Paleozoic carbonate rocks and shale, and Mesozoic 

shale, mudstone, and volcanic rocks (fig. 2). These rocks are exposed 

on a broad northwest-trending syncline that is cut by numerous, 

chiefly normal faults, and is intruded by a complex sequence of maficfelsic dikes, sills, and stocks of Cretaceous to middle Tertiary age. 

The stocks are important loci for mineral deposits and include such 

bodies as: (1) the Santa Rita granodiorite porphyry stock, (2) the 

Fierro-Hanover granodiorite-quartz diorite pluton, (3) the Pinos 

Altos quartz monzonite stock, and (4) the Silver City granodiorite 

stock (Trauger, 1972; Cunningham, 1974; Jones and others, 1967; 

Hernon and others, 1953; Jones and others, 1970). 

The Tertiary volcanic rocks north of about lat 32 °52 '30 " N. are 

composed mostly of ash-flow tuff units of Oligocene age (Finnell, 

1976a, b; Trauger, 1972; Moore, 1953), which are intruded by dikes 

and by shallow, irregular bodies of felsic composition. Normal 

faulting cuts the volcanic units into a series of northwest-trending 

horsts and grabens. 
6 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
0 5 10 15 20 25 KILOMETERS 

0 5 10 15 MILES 

EXPLANATION 

OTg GRAVEL, SAND, SILT, AND CLAY (QUATERNARY AND 

TERTIARY)-Mainly alluvium on stream terraces, fan aprons, 

and pediments; colluvium on hill slopes; and lacustrine and 

eolian deposits in basins 

EJ ·. 'l CONGLOMERATE AND VOLCANIC ROCKS (TERTIARY)-

Mainly coarse conglomerate with intercalated mafic to intermediate flows and tuff 

INTERMEDIATE TO MAFIC VOLCANIC ROCKS (TERTIAR'!)-

Mainly flows, scoria cones, domes, and small intrusions. 

Locally includes small units of felsic volcanic rocks and volcaniclastic rocks 

I Tf FELSIC VOLCANIC ROCKS (TERTIARY)-Mainly flows, 

domes, and pyroclastic deposits. Locally includes small units of 

mafic volcanic rocks and volcaniclastic rocks 

INTRUSIVE ROCKS (TERTIARY)-Includes granitic rocks in 

plutons and aphanitic and porphyritic rocks in plugs and dikes 

INTRUSIVE ROCKS (TERTIARY AND CRETACEOUS)-

Includes granitic rocks (commonly porphyritic) in plutons and 

porphyritic rocks and breccias in dikes, plugs, and small stocks 

ANDESmC ROCKS (TERTIARY AND CRETACEOUS)-

Fiows and small intrusions. Locally includes beds of sedimentary rocks 

SEDIMENTARY AND VOLCANIC ROCKS (MESOZOIC)-

Mainly shale, siltstone, sandstone, and conglomerate; includes 

some limestone and felsic to intermediate volcanic rocks. 

Mainly Bisbee Group to the southwest and Colorado Formation 

to the northeast, both of Cretaceous age 

SEDIMENTARY ROCKS, UPPER PART (PERMIAN AND 

PENNSYLVANIAN)-Mainly limestone; includes some dolo-

~ 

mite and sandstone. Chiefly Naco Group 

SEDIMENTARY ROCKS, LOWER PART (MISSISSIPPIAN 

AND CAMBRIAN)-Mainly limestone, dolomite, shale, quartz-

,' ' ~ '· "j [ ' ~.,'· Y'f ( ' 

ite, and sandstone; includes some conglomerate and arkose 

INTRUSIVE ROCKS (PROTEROZOIC Y) -Granitic rocks, 

commonly porphyritic or porphyroblastic, in plutons 

METASEDIMENTARY AND METAIGNEOUS ROCKS 

(PROTEROZOIC X)-lncludes Pinal Schist, gneisses 

CONTACT 

NORMAL FAULT-Dotted where concealed 

DIKE (TERTIARY AND CRETACEOUS)-Mafic porphyry, 

dominantly quartz diorite 

FIGURE 2.-Generalized geologic map of the Silver City mining region and adjacent areas, Grarft County, N. M. Modified from 

map compiled by Silver City 1 o x 2° quadrangle, conterminous United States Mineral Appraisal Program team, unpublished 

mapping 1980. 

0 

trj 

?5 

::t: 

trj 

~ ..... 

n 

> t"" 

trj 

~ r:n 

t-3 

0 

~ 

0 

z 

r:n 

-.l 
8 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

GEOCHEMICAL INVESTIGATIONS 

SAMPLE MEDIUM AND METHODS 

This study used panned heavy minerals derived from active 

alluvium as the basic sample medium. The alluvium was derived 

nearly exclusively from unbranched stream tributaries within areas 

of bedrock outcrop. This sampling approach has been somewhat effective in other parts of the southwestern United States for both 

regional and relatively detailed district studies. Two factors are 

responsible for the effectiveness of the geochemical sample medium: 

First, the metals released during destruction of the mineral deposits 

are more commonly dispersed mechanically than chemically in the 

semiarid environment; and second, most mechanically dispersed, orerelated metals occur in minerals and limonitic aggregates of specific 

gravity greater than 2.8, which makes them amenable to collection 

into a heavy-mineral concentrate. 

The samples were collected from 921 localities, from ephemeral 

streams that were short in length and small in drainage area (often <3 

km2 ). Small drainage basins were selected because mechanicaldispersion trains rarely exceed 2.5 km in arid or semiarid regions 

(Beus and Grigorian, 1977, p. 198), because contamination from mining and milling, which is cumulative in drainage systems, is more 

likely to be a problem in large drainage basins, and because the 

details of the metal dispersion can be gained by the relatively detailed 

sampling small drainages offer. 

Each sample was collected at oblique angles to the active drainage 

channel and as near to underlying bedrock as possible. Composite 

samples were collected randomly across the full width of wide active 

channels where such channels were present. Occasionally, extensive 

boulder and cobble rubble required compositing of sediment from 

various accumulations behind rocks and in potholes. ·rhese bulk 

samples, which weighed from 4 to 5 kg, were then gold panned on 

site if water was available, or otherwise they were carried away from 

the site to be panned later. Panning was done to the point where the 

sample reduced to heavy minerals and to a light-mineral diluent content of about 30 percent; the size of the heavy-mineral sample after 

removal of diluent-when uniform amounts of sediment are initially 

collected-is determined mostly by the geology of the basin area and 

therefore is highly variable. Samples from Fort Bayard quadrangle 

were consistently larger than average because of the abundant, 

clastic ferromagnesium minerals derived from the numerous mafic 

dikes in the area. 
GEOCHEMICAL INVESTIGATIONS 9 

Further processing of the sample after panning consisted of drying, 

magnetite removal, bromoform separation to remove the lightmineral diluent, magnetic separation at 1.0 A (25 degree forward, 15 

degree side-slope, using a Frantz Isodynamic Separator1

) into two 

fractions, and then pulverization to a fine powder. These methods 

have been described in more detail by Watts, Hassemer, Siems, and 

Nishi (1978b). 

Magnetic separation of the heavy minerals provides interpretational advantages. The magnetic field intensities and slope settings 

nearly separate the sample into components of light- and darkcolored minerals. The nonmagnetic (at 1.0 A) component contains 

light-colored rock-accessory minerals and most ore-related primary 

and secondary minerals; whereas, the magnetic (at 1.0 A) component 

contains chiefly mafic rock-forming minerals and several types of 

secondary iron and manganese oxide minerals and amorphous mixtures, often referred to by the field term 'limonite." Differences in 

analytical values between the two fractions are mostly due to the 

mineralogical differences between them-though in some cases, 

minerals and metal values span the two fractions. Geochemical 

anomalies usually contain metal concentrations that result from both 

primary and secondary processes; these two fractions are valuable to 

understanding the contribution of each dispersion process. The 

primary ore-metal suite is usually represented in the nonmagnetic 

fraction because in metallized areas this fraction frequently contains 

heavy primary- and secondary-ore minerals. On the other hand, where 

there are deeply weathered, relict-hypogene (gossan) situations or 

where secondary metal dispersion has resulted in metal fixation by 

hydrous iron oxides (limonite) and manganese oxides of various types 

and origins, the metal suite deposited by or interacting with oxidizing solutions are selectively, though not exclusively, concentrated in 

the magnetic fraction. 

ANALYTICAL METHODS 

The prepared samples were analyzed by semiquantitative emission 

spectrography for 30 elements (Grimes and Marranzino, 1968). These 

spectrographic data are reported in parts per million on a scale with 

approximate geometric midpoints, such as 1,000, 700, 500, 300, 200, 

150, and 100. The precision of these data is within one adjoining 

'Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Geological 

Survey. 
10 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

reporting interval 83 percent of the time and within two adjoining 

reporting intervals 96 percent of the time for all elements sought and 

for all materials tested (Motooka and Grimes, 1976). Only selected 

metals among the 30 scanned are discussed in this report. Some of 

the elements have low variation, were seldom detected, or have no obvious bearing on studies of metal deposits in the region, and therefore 

are not treated here. Analytical and statistical analyses for all of the 

elements have been reported earlier (Watts and others, 1978b). 

DATA REDUCTION 

All data were entered into the U.S. Geological Survey (USGS) computer data storage system entitled RASS (Rock Analysis Storage 

System). The data were then retrieved and analyzed statistically using USGS STATPAC programs (VanTrump and Miesch, 1977; 

Alminas and VanTrump, 1978; VanTrump and Alminas, 1978). Summary statistics derived from graphical analyses of log-transformed 

data were reported by Watts, Hassemer, Siems, and Nishi (1978b). 

Programs used here for data reduction and analysis include computer 

contouring (STPMAP), relative element magnitude (REM), and 

relative fraction magnitude (RFM). 

The geochemical maps for each metal of interest (figs. 3-22) were 

computer plotted using the contour program STPMAP (Van Trump 

and Miesch, 1977). This program generated cell-averaged maps with 

intervals chosen within the anomalous population, thereby excluding 

areas considered background from within the contours. The contouring was based on a square grid 1.1 km on a side which required 42 

cells in the east-west direction and 25 cells north-south in order to fit 

the unequal dimensions of the map area. With the dense sample-site 

distribution, the cell dimensions resulted in relatively unsmoothed 

contours, often with rather sharp curvatures that closely resemble 

contours based on the raw data. 

After the cell size was established by computation, a circle of an appropriate search radius (1. 7 km) calculated by the program was 

centered at each grid intersection. Then, the metal values within each 

circle were averaged and posted at the intersection. In order to 

achieve continuity of contour lines empty cells within sampled areas 

were assigned a default value. Finally, the parameters for these contour values were written on a plotting tape, which was used to 

generate mylar contour maps at a scale of 1:250,000 using a flatbed 

plotter. Large areas where no sampling was done were not contoured 

though inherent weaknesses in the gridding program have caused a 

slight shifting of contours into these areas. 
GEOCHEMICAL INVESTIGATIONS 11 

GEOCHEMICAL HALOS 

The most defined geochemical anomalies, both areally and in terms 

of anomaly to background contrast, are associated with eight general 

areas: Central mining district, Fierro-Hanover districts, Georgetown 

district, Pinos Altos district, Fleming Camp area, Chloride 

Flat-Boston Hill district, Juniper Hill area, and the adjacent 

vicinities to the north within Turkey Creek Canyon, Sycamore Creek, 

and Bear Creek. Of these eight areas, seven contain known mineral 

deposits, but the geochemical anomalies are not exclusively attributable to these sources. The Circle Mesa area may become a site 

of new mineral discoveries as with the other areas, but no deposits 

are presently known as opposed to the other areas. 

There are other geochemically anomalous parts of the study area, 

but the anomalies are not as specifically localized nor in most cases, 

as intense; rather, they are generally pervasive occurrences of such 

lithophilic2 elements as barium, manganese, and zinc (zinc is both 

lithophilic and chalcophilic), or scattered occurrences of such 

chalcophilic3 metals as silver, copper, and lead. The anomalies north 

of lat 32°52'30"N and west of long 108°16'00"W in the volcanic terrane are of particular interest in this respect. The broadly blanketed 

enrichments of lithophilic elements are presumably fixed within the 

various amorphous and crystalline oxides of manganese and iron 

(magnetic fraction). 

In order to account for this widespread enrichment of these 

elements, causative factors common to all the areas must be invoked. 

All the elements comprising this anomalous suite (chiefly Mn, Ph, Zn, 

and Ba) are readily available within the feldspars and mafic rockforming minerals present in igneous host rocks. Because volcanism is 

a common denominator, it is here proposed as the dominant factor. 

The metals have probably been extracted from rock-forming minerals 

by alteration. Heated meteoric water of slightly acidic composition 

either convecting within a water-saturated volcanic pile or associated 

with plumes above subvolcanic intrusions could provide the 

mechanism of transportation; one which could be expected to be a 

common, if not a prevalent, characteristic of the volcanism. The solutions moreover would be oxidizing and would be capable of providing 

pervasive invasion of volcanic caprock and deposition of metals 

within oxide phases. 

'Lithophilic elements form in the lithosphere or upper Earth's crust where they enter the lattice of silicate 

minerals. 

•Chalcophilic elements have a strong affinity for sulfur and include a large number of the metals that form 

metallic ore deposits. 
12 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 

Where the chalcophilic elements are geochemically enriched within 

the volcanic terrane, mobilization and redistribution of metals from 

sulfide protore or Laramide ore deposits may have occurred. Metals 

may have also been introduced from magmatic emanations 

associated with subvolcanic intrusives. Anomalies of both 

chalcophilic and lithophilic elements of the felsic rock suite (Sn, Be, 

Nb, and Mo) could have these origins. Subvolcanic intrusives may 

also have caused local metal depletions as well as introductions, 

resulting in some of the geochemical lows seen on the maps. 

Faults either provided conduits or exerted a control over the 

emplacement of intrusives in the volcanic terrane because there are 

close spatial associations between many of the geochemical trends 

and mapped faults (Finnell, 1976a, b; Moore, 1953). 

The metal groupings used in the following discussion are based on 

geochemical similarities and on coextensive areal distributions as 

shown on the geochemical maps (figs. 3-22). 

LEAD, COPPER, AND ZINC 

Lead shows the broadest and best defined anomaly patterns (fig. 3). 

The anomalies are limited for the most part to the southern half of 

the study area where erosion reaches deeper stratigraphic levels. The 

nonmagnetic lead anomalies, being largely due to detrital ore 

minerals, indicate areas where primary mineral deposits are near the 

surface but may have undergone lateral mechanical transport for 

short distances. Because of the surface stability of most ore minerals 

of lead, the lead anomaly trends probably conform closely to 

pathways followed by primary, metalliferous solutions as viewed on 

the regional or district scale. The trends are rectilinear with 

dominantly northwest and northeast orientations. Known mineral 

deposits are at the intersections of several of these linear patterns; in 

such areas, the intersections are characterized by a broadening and 

intensification of the anomaly. 

The areal distributions of lead associated with iron and manganese 

oxide phases (fig. 4) are less widespread than those related to the ore 

minerals (nonmagnetic fraction) because conditions favorable to 

these accumulations are more restricted. Controlling factors to the 

development of strong anomalies in the magnetic fraction include ( 1) 

high permeability of host rock to descending, oxidizing meteoric solutions, (2) chemical reactivity of host rock, and (3) abundance of pyrite. 

The conditions favorable to oxide-related lead anomalies prevail near 

the Mimbres and Barringer faults, and within the Groundhog fault 

trend, within areas parallel to the Silver City fault and near the north-
GEOCHEMICAL INVESTIGATIONS 13 

trending range front fault west of Juniper Hill. (See fig. 2.) 

Copper is distributed over a much smaller area than is lead (fig. 5). 

The copper-dispersion patterns are similar in areal distribution to 

each other in both fractions, although they are somewhat displaced 

from each other locally (fig. 6). The nonmagnetic fraction contains 

most of the copper-ore minerals, where present, but certain copperore minerals are magnetic at 1.0 A; therefore, ore minerals can accumulate in either component. The Central and Pinos Altos districts 

contain most significant copper enrichments. The anomaly patterns 

in the Central district conform to the geologic structure and the 

trends of the known veins; whereas, those at Pinos Altos broadly 

replicate the shape of the intrusive stock. The anomaly patterns on 

the northwest side of the Fierro-Hanover stock show the influence of 

the Barringer fault-whether as a localizer or displacer of mineral 

deposits cannot be determined from the geochemical pattern conclusively. In the Georgetown silver district, copper and molybdenum 

(figs. 12, 13) are sufficiently enriched to suggest that economic concentrations of these metals may occur at depth below the silver 

zones. On the basis of the geochemistry, the Fleming Camp area 

would appear to have little copper at the surface. This may, however, 

be an effect of metal zonation in the vertical plane of the type shown 

at Pinos Altos (Hernon, 1953) rather than a measure of the amount 

introduced by metallization or removed by leaching. If base metal 

orebodies exist at depth as geochemical evidence suggests, copper 

content may increase with depth as it does at Pinos Altos (Hernon, 

1953). 

Zinc-producing districts are well outlined by the zinc geochemical 

patterns (fig. 7). The zinc-lead replacement deposits at Shingle 

Canyon are shown by the geochemical map to occur at the intersection of linear-shaped zinc contours that parallel the Mimbres and Barringer faults. In a similar manner, zinc geochemical patterns coincide 

with the Groundhog zone of faults, dikes, and zinc-producing mines. 

A well-developed northwest-trending zinc halo extends through the 

northern parts of the Pinos Altos stock and connects with an altered 

zone north -of Juniper Hill and may well reflect a co genetic relationship between the two areas. The zinc halo at Pinos Altos is similar in 

shape to the outcrop pattern of the stock, as it is with several other 

metals. This close spatial relationship indicates the closeness of 

genetic ties. 

Zinc associated with oxides of manganese and iron and probably 

some marmatite (Fe-Mn-rich sphalerite) (fig. 8) is similar in 

geographic distribution to the nonmagnetic fraction within the 

mineral districts. Beyond the mining districts, though, similarities 

end. Areal distribution of magnetic-fraction anomalies is far more ex-
14 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

tensive. The anomalies continue beyond the perimeters of known 

deposits, particularly northward into the volcanic terrane. There is 

little disruption of these geochemical patterns even though they 

transect varying rock types and levels of stratigraphic exposure. One 

of the more prominent contour patterns broadly parallels the 

northwest-trending Mimbres fault, which past studies (Watts and 

others, 1978a) have shown is paralleled by coextensive anomalies of 

both zinc and manganese for a distance of about 29 km to the 

southeast from near Shingle Canyon. Apparently, zinc-manganese 

anomalies along significant structures peripheral to mining districts 

are common. Olade and Fletcher (1976) noted similar zinc-manganese 

concentrations within a fault zone adjacent to a major metalproducing district in British Columbia. The zinc-manganese 

enrichments were found in that case to be localized within the fault 

zone itself. They considered these metal concentrations to be mobilized and peripherally redistributed products of hydrothermally leached 

mafic minerals from within zones of intense alteration in the main 

mining district. Anomalies of zinc and manganese (figs. 8, 20) in the 

volcanics may be related to and mark the positioning of rock alteration 

and leaching at depth, or perhaps even the remobilization of deepseated protore. If so, they are clues to deep exploration targets. The 

low area in the north-central part of the map area of figure 8 (shown 

by hachure) may be an area of zinc depletion, as it apparently is 

of manganese depletion also (fig. 20). This zone may indicate the position of a large, centered high-heat source--perhaps a buried intrusive 

body that has been instrumental in the mobilization and removal of 

metals. Another, less auspicious interpretation may be that the ashflow tuff in the area has covered the zinc-manganese enriched zones 

subsequent to their deposition. These postulates require further investigation. 

BISMUTH AND TUNGSTEN 

Bismuth probably associated with bismuth sulphosalts and 

tungsten related to scheelite (figs. 9, 10) prominently characterize the 

areas of. Pinos Altos and Fleming Camp. There is also bismuth at 

similar levels of concentration near the Barringer fault and on the 

contact-metamorphic margins of the Fierro-Hanover stock. The 

distribution of zinc in these same areas indicates that it may belong 

to, but is not restricted to this metal suite. The association bismuthtungsten-zinc from empirical observations can be a guide to skarnreplacement mineralization in the Silver City region. At Pinos Altos, 

large tonnages of skarn-replacement zinc-copper-lead ore are present 

in the host rocks surrounding the Pinos Altos quartz monzonite 
GEOCHEMICAL INVESTIGATIONS 15 

stock (McKnight and Fellows, 1978). At Fleming Camp, intrusive 

rock has not been mapped, yet the bismuth-tungsten-zinc anomalies 

are similar in intensity and in areal extent to those at Pinos Altos. 

The levels of concentration of the metals tungsten and bismuth indicate that they are dominant constituents of discrete mineral 

phases. Nonmagnetic, anomalous tungsten can be attributed to 

scheelite, which was identified in samples from both Fleming Camp 

and Pinos Altos. The minerals bismuthinite (Bi2S3), matildite 

(AgBiS2), cosalite (Pb2Bi2Ss), and emplectite (CuBiS2) were identified 

in veins at Pinos Altos (McKnight and Fellows, 1978). These minerals 

are typical of skarns and of high-temperature veins (Palache and 

others, 1952). Though these minerals were not observed in samples, 

either these or similar heavy minerals are believed to be present in 

alluvium derived from the Pinos Altos, Fleming Camp, and FierroHanover districts. 

Tungsten, as opposed to bismuth in any significant amounts, also 

occurs in the magnetic fraction. Although this component can contain wolframite-series minerals, they were not noted in the 

mineralogic scans; whereas, abundant limonite and hydrous 

manganese oxides were noted. Nearly all tungsten anomalies in the 

magnetic fraction occur at Fleming Camp and near Circle Mesa (fig. 

11), which, perhaps of genetic significance, are also the only two areas 

where more than sparse amounts of detrital fluorite have been identified (Watts and Hassemer, 1980). The anomaly at Circle Mesa 

(northwest anomaly), which occurs in volcanic host rock, is 

associated with a zone of felsite intrusives, and minor base-metal 

anomalies, as well as the fluorite. The tungsten is thought to reside in 

manganese oxide minerals (possibly psilomelane), which are abundant in the area. (See fig. 20.) Tungsten is known to associate with 

certain types of manganiferous hot-spring deposits, such as those at 

Golconda, Nev. (Kerr, 1940). Kerr concluded that veins of hypogene 

tungsten minerals (presumably scheelite or wolframite-series 

minerals) are present in the subsurface somewhere along the circulation pathways followed by the heated meteoric water, and he concluded that tungsten was solubilized and extracted from these veins, 

transported upward, and coprecipitated with the oxide phases of 

manganese. 

Scheelite is known to occur at Fleming Camp but not Circle Mesa. 

Some of the scheelite at Fleming Camp may be secondary in origin 

because, according to Rankama and Sahama (1950, p. 629), hydrated 

tungstic oxide is the usual stable phase in the weathering zone above 

primary tungsten ores, but if carbonate rocks are present, and 

calcium is available, tungstic oxide may go into solution as an alkalic 

tungstate and precipitate as secondary scheelite. The apparent 
16 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

absence of scheelite at Circle Mesa may be related to the availability 

of calcium. Where calcium is unavailable to form scheelite during 

primary metallization, tungstic oxide may be fixed in hypogene 

manganese oxide minerals (Hewett and Fleischer, 1960, p. 25-28), 

which could be the origin of the anomalies at Circle Mesa. This does 

not rule out the possibility that scheelite may be encountered at 

depth at Circle Mesa. 

Thus, tungsten occurrences at Circle Mesa and at Fleming Camp, 

in the magnetic fraction, can be attributed to a number of controlling 

factors. Weathering is probably a more significant contributor to the 

origin of the anomalies at Fleming Camp than at Circle Mesa, if the 

manganese oxides at Circle Mesa are hypogene in origin. 

MOLYBDENUM 

Molybdenum (fig. 12) is associated with lead, zinc, and copper and 

is most prominent at Fleming Camp, in the Central district, and at 

Georgetown. Strong molybdenum signatures occur where secondary 

base-metal-molybdenum deposits are present, because the 

associated minerals in these deposits are both heavy and surface 

stable. A large variety of vanadate, molybdate, and arsenate 

minerals can be expected in heavy-mineral samples within the mining 

region. Secondary, detrital ore minerals, such as wulfenite, account 

for most molybdenum anomalies with the highest anomaly to 

background contrast, which is for the most part an indication that 

the source deposits are highly oxidized, likely small, and near surface. 

The strong geochemical contrast shown by molybdenum and its excellent correlation with equally strong lead values near the southwest 

end of the Groundhog trend of faults, dikes, and mines in the Central 

district is probably related to the presence of wulfenite (PbMo04), 

which has been reported there by Lasky (1936, p. 78-79). 

Molybdenum-lead correlations elsewhere in the Silver City region 

indicate similar occurrences. The Georgetown district and areas 

southward along the Mimbres fault, and an area on the east-central 

margin of the map (east of Santa Rita copper deposit), are other examples. 

In an oxidizing environment, molybdenum is mobilized as several 

molybdenum species in the acidic ore zone and then can be fixed in 

alkaline soil in the presence of coprecipitating iron hydroxides 

(Titley, 1964). Molybdenum concentrations in the magnetic fraction 

at Boston Hill probably result from the fixation of molybdenum in 

secondary iron-manganese oxide materials which in that area occur in 

abundance (fig. 13). Molybdenum fixed in this manner, in significant-
GEOCHEMICAL INVESTIGATIONS 17 

ly high concentrations, has not been encountered extensively in the 

study area as a whole, though the Tertiary volcanic rocks contain 

lesser, marginally anomalous amounts in places (particularly north of 

Pinos Altos). Molybdenum at these levels of concentration was 

eliminated by the computer averaging technique used in this study. 

The marginally anomalous data can be found in Watts, Hassemer, 

Siems, and Nishi (1978b). 

SILVER AND GOLD 

Silver and gold are somewhat similar in distribution on the anomaly maps (figs. 14, 15, 16), though silver is by far the most widespread, 

often occurring in association with such metals as lead and 

molybdenum, to the exclusion of gold. However, because of 

geochemical similarities between the metals, they are discussed 

together. 

Surface-stable silver-bearing minerals of chiefly secondary origin 

account for most occurrences of anomalous silver in the nonmagnetic 

fraction. These heavy minerals are relatively immobile chemically in 

the near-surface environment, and they constitute the chief source of 

silver production (Hernon, 1953). Where these minerals are encrusted 

by transported limonite or are contained in the hydrous ironmanganese oxides within the weathered zone, lesser amounts of 

anomalous silver may be found in the magnetic fraction, which accounts for the similarities in geographic distributions of silver in the 

two fractions and for the far more limited extent of magnetic silver 

(fig. 15). The magnetic silver may be more concentrated in zones 

where associated primary minerals have a high iron content or in 

areas of high permeability, as may occur along the fault zones (for example, the Mimbres fault) because of more efficient weathering and 

oxidation. 

Not unexpectedly, the principal areas outlined by gold contours are 

in the Pinos Altos district and at the known gold placer deposits near 

Bayard, N. Mex., in the Central mining district (Lasky, 1936). The 

Pinos Altos district contains the most prominent dispersion halo of 

gold, mostly within drainage areas within the stock itself. This gold 

is in the native state as detrital grains in the alluvium derived from 

the Pinos Altos stock. 

The gold anomalies indicate the amount of gold detected by emission spectrography, which is an imprecise method for analyzing gold. 

In some cases, the analyses do not show areas where gold was visually identified in concentrated sediments. The anomalies reflect the 

amount of gold detected where 4-5 kg of bulk samples were reduced 
18 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

by panning and other processing to nearly one-thousandth of its 

original size. Because this gold is both particulate and malleable, it 

was sometimes missed by the analyses. Therefore, when coherent 

anomaly patterns can be produced from the analyses, gold must be 

very abundant in the associated drainage basins, because sparse, 

scattered detrital grains would produce scattered, erratic 

geochemical anomalies. 

In addition, the geochemical method cannot be used to evaluate 

grade and tonnage of particulate gold; this evaluation requires 

special techniques of placer study in which the volume of alluvial 

material containing a given quantity of gold is estimated. The 

geochemical method only locates the gold occurrences and identifies 

areas where gold is most abundant. 

Gold may also be used as a pathfinder to other types of deposits. 

Gold is a characteristic metal of the mineralization at Pinos Altos 

(fig. 16). Because of geochemical similarities between Pinos Altos and 

Fleming Camp, it was earlier postulated that copper content at Fleming Camp may increase with depth as it does at Pinos Altos (Hernon, 

1953); as a corollary, gold content may also increase with depth. 

BARIUM AND MANGANESE 

N euerburg, Barton, Watterson, and Welsch (1978) have observed 

that the lithophilic elements barium and manganese, in addition to 

iron, silica, and zinc, are redistributed during the alteration of rocks 

and are ultimately deposited in the gangue minerals and on the 

periphery of metalliferous deposits. Olade and Fletcher (1976) have 

made similar observations, which they attributed to acidhydrothermalleaching along an advancing replacement front as envisioned by Korzhinskii (1968). These observations suggest that 

manganese and barium can provide important clues to patterns of 

alteration brought about during regional metallization. The similarity of zinc contours to those of manganese has been discussed; the 

geochemical maps show that these distributions are similar for 

barium as well. 

The barium map of the nonmagnetic fraction (fig. 17) is also a 

barite map because, at high concentrations, the metal content is due 

to the presence of that mineral. Barite is the most common mineral of 

barium; it is a gangue mineral in metal deposits and an additive 

alteration product, and it is the least soluble and most common 

alkaline-earth sulfate associated with hydrothermal systems (Neuerburg and others, 1978; Holland and Malinin, 1979, p. 495). During 

hydrothermal leaching, barium can be derived from potassium-
GEOCHEMICAL INVESTIGATIONS 19 

feldspar within the host rocks. Because of the prograde 

characteristics of barium in solution, Holland and Malinin (1979, p. 

498, 499) believed that simple cooling is sufficient to account for the 

precipitation of barite from solution, although other factors must 

still be considered. These conditions presumably can exist in highly 

fractured areas and near the surface. Because barite forms around 

and above metal deposits, knowledge of the positioning of these 

barite halos can be useful in locating covered deposits. The northnortheast-trending contours indicate barite-enrichment zones that 

may be either peripheral to or coextensive with the surface trace of 

ore-solution conduits. Interpretations of the significance of the barite 

halos can be complicated by considerations of the erosion level. For 

example, the continuous, north-northeast-trending contour patterns 

link some of the mineral districts to e~ch other, and because erosion 

is rather deep within the mining districts (south of lat 32 °52 '30" N .), 

these barite halos may be on the lateral periphery of potential zones 

of mineral deposition or of alteration because preexisting overlying 

halos may be eroded away. In volcanic terrane north of lat 32°52 '30" 

N., however, the halos may be vertically above altered zones or solution conduits on account of erosional stripping being much less. 

Most barium in the magnetic component (fig. 18) is probably 

associated with several types of hydrous manganese oxides in which 

barium is held as a coprecipitated or adsorbed constituent (Levinson, 

197 4); or in the case of crystalline minerals, it is part of the structure 

(for example, the case of the mineral hollandite). This association is 

well documented in the literature and can be seen here by comparing 

the manganese and barium geochemical maps (figs. 18, 20). The 

usefulness of barium-rich, secondary manganese oxides in exploration is yet to be determined, but hydrothermal alteration and 

mineralization may cause these concentrations of barium in association with hydrous manganese oxides at the lateral or vertical 

periphery of metal deposits. Surface weathering of preexisting rockforming minerals can also cause these concentrations as well, which 

suggests that any interpretations of manganese-barium anomalies 

should also consider the intensity of the weathering environment. 

The manganese distribution in figure 19 shows where nonmagnetic, 

generally primary manganese minerals, such as manganiferous carbonates, are most concentrated. Because most primary gangue 

minerals are deposited in veins during the metallization events, 

though mostly on the vertical or lateral periphery of the main 

chalcophilic orebodies, the distribution of minerals of this kind can be 

of interest in exploration. Where weathered, most of these minerals 

convert to secondary hydrous manganese oxides, which are ultimately surface stable; in the Chloride Flat-Boston Hill district 
20 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

manganiferous mesitite (FeMgC03) was considered to be the primary 

progenitor of the secondary manganiferous iron-ore deposits (Entwhistle, 1944). Figure 20 shows extensive areas within the mineralized districts where minerals of this type are presumably in abundance. 

Outside the known metallized areas, as for example, near Circle Mesa 

and several kilometers north of Fierro near Skate Canyon (both 

within volcanic terrane), extensive areas with anomalous nonmagnetic manganese have been detected in the sampling. 

Presumably, these zones reflect the presence of primary, nonmagnetic vein minerals of manganese (probably carbonates). These 

occurrences may indicate the replacement and mobilization of carbonate from Paleozoic rocks beneath the volcanics. Replacement of 

the Paleozoic rocks may have also involved metallization. 

Manganese displays pervasive and complex patterns of distribution in the magnetic component. These patterns are not unexpected 

because figure 20 depicts the distribution of hydrous manganese oxides, which are exceedingly widespread and may have several origins, 

and are selectively fractionated into the magnetic heavy-mineral 

component. The oxides of manganese present within the mineral 

districts are probably derived from the supergene weathering of 

preexisting primary manganiferous minerals, particularly vein and 

replacement deposits of manganiferous carbonate. Two prominent 

areas where this may be the case are at Boston Hill where 

manganese-iron deposits are now being mined, and along the Barringer fault where, as reported by Hernon, Jones, and Moore (1953), 

manganese replacement deposits are found in adjacent wallrock. 

The apparently pervasive distribution of manganese oxides within 

the areas covered by middle Tertiary volcanics suggests that 

volcanism may have contributed to these concentrations. Heated 

meteoric water within a water-saturated, tuffaceous volcanic pile 

could have provided the mechanism that allowed manganese to be 

leached from the host rocks within the pile at depth and to be 

transported upward to sites of deposition. In fact, hot-spring and 

apron deposits of primary manganese oxide minerals are rather common occurrences in volcanic areas (Hewett and Fleischer, 1960). 

Because the anomaly trends of manganese and the geologic trends 

coincide somewhat and because the anomaly patterns transect the 

minor climatic differences that exist between the northern and 

southern parts of the area (Trauger, 1972), weathering alone probably 

is not the most significant determining factor leading to enrichment 

in the bedrock of these manganese oxides. On the other hand, when 

the manganese anomaly map and the geology are compared, faults 

appear to be a controlling influence on the concentrations-either in 

the localization of the primary minerals during deposition or in the 
GEOCHEMICAL INVESTIGATIONS 21 

promotion of their later oxidation, and thus strong residual concentration, or both. 

TIN 

Tin (fig. 21) appears to have been introduced during metallization 

in the Silver City mining region. Anomalies of nonmagnetic tin occur 

at Fleming Camp, Pinos Altos, Central district, Georgetown, Circle 

Mesa, and near the Silver City stock. Heretofore, tin has not been 

recognized as a metal component of these ores; although present, it is 

unlikely to be in economic amounts. The mineralogic source of the tin 

has not been determined, though elsewhere in the region anomalies of 

about 700 parts per million or more can be attributed to the presence 

of cassiterite (Sn02). 

VANADIUM 

Vanadium values in the nonmagnetic component at high levels of 

concentration are a result of discrete, vanadium-bearing ore minerals, 

chiefly secondary in origin, that occur in the supergene zone of oxidizing lead-zinc vein deposits. V anadinite (lead vanadate) is the most 

common mineral of this type. Figure 22 shows the distribution of 

these secondary vanadium-bearing ore minerals. V anadinite has been 

identified at Georgetown (Lasky and Wooten, 1933, p. 57), and an 

arsenic-rich variety of similar appearance, endlichite Pb5(V,As04hCl 

in association with cuprodescloizite (mottramite) 

((Pb,Zn,Cu)3(V04) 2 •(Pb,Zn,Cu)(OHh), was identified at the Lucky Bill 

mine in the Central district (Lasky, 1936, p. 84). Areas where the 

geochemical maps suggest the presence of these minerals are (I) 

about 4-5 km east of Santa Rita porphyry copper deposit, (2) near the 

Mimbres fault and at Georgetown, (3) west of Pinos Altos, and (4) the 

Central district. 

INTERPRETATION 

SELECTION AND DESCRIPTION OF WINDOW AREAS 

The characteristics of the geochemical anomalies were compared 

quantitatively between several geographic areas that were selected 

on the basis of anomaly clustering (figs. 3-22). The boundaries of each 

anomaly cluster were blocked off geographically on the basis of maximum spread of a discrete cluster of anomalous values, though 
22 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

somewhat arbitrarily, and held constant. The anomaly 

characteristics were calculated on metal values in the anomalous 

range, and the assumed threshold values remained the same for both 

fractions and in all window areas. Locations and descriptions of the 

selected window areas are shown in table 1. 

COMPARISON OF HEAVY-MINERAL FRACTIONS 

The U.S. Geological Survey ST A TP AC program relative fraction 

magnitude (RFM) (Alminas and VanTrump, 1978) was used to compare anomalous metal contents between heavy-mineral fractions in 

each of the areas. The fractions are compared on the basis of two factors: halo intensity and halo size. The product of these two factors is 

the fraction magnitude (FM), which is calculated for each of the 

selected metals separately within each window area. The information 

from these comparisons can be used to assess the relative influence of 

weathering, and perhaps resultant supergene dispersion in each area 

on any selected metal, .but it mainly applies to those metals considered to be chalcophilic. This is a method of determining the degree 

to which the chalcophilic elements are retained by fixation within 

hydrous iron-manganese oxides through such mechanisms as adsorption and coprecipitation. The ratio FM (magnetic)IFM (nonmagnetic) 

provides an index that can be used for this purpose. Values for this 

ratio within each of the window areas are shown in table 2. 

Table 2 shows that the degree to which the chalcophilic elements 

are associated with secondary iron-manganese oxides is in the 

decreasing sequence Zn-Cu-Pb-Bi-Mo-Ag. This sequence is obtained 

by summing the ratios shown in table 2 for each chalcophilic element; 

the lowest ratio sums occur for those elements on the right side of the 

sequence. This is also the sequence, excluding a close but reverse 

positioning of bismuth-molybdenum, of decreasing crustal abun-

~ance-zinc is the most abundant metal of the group in the crust, and 

silver is the least abundant (Krauskopf, 1967, p. 639-640). However, 

as stated by Rankama and Sahama (1950, p. 13), the nature of the 

products formed in hypogene and supergene reactions is dependent 

upon elemental abundance and is ultimately controlled by the law of 

mass action, which is also dependent on rate of dissolution. 

Therefore, concentrations of metal available and rate of dissolution of 

primary mineral species may account for the sequence. The sequence 

that developed from the ratios can be interpreted in the following 

manner: Elements such as bismuth and silver, which appear on the 

right or decreasing end of the sequence, occur in the most surfacestable, secondary- or primary-ore minerals and are weakly mobile in 
GEOCHEMICAL INVESTIGATIONS 23 

supergene solutions-assuming iron and manganese are present and 

secondary iron or manganese minerals or amorphous aggregates are 

allowed to form. Where only a nonmagnetic component appears, the 

primary progenitors may have been iron-free sulfides and sulfosalts. 

The sums of FM ratios for the chalcophilic elements silver, 

bismuth, copper, molybdenum+, lead, and zinc were compared between window areas, and a sequence of the areas was derived. This sequence indicates a decreasing association of the selected metals with 

the secondary iron and manganese oxides, and, indirectly perhaps, 

with oxidizing, primary or secondary solutions. The sequence is (1) 

Skate Canyon (Sheep Corral Canyon), (2) Circle Mesa, (3) Chloride 

Flat-Boston Hill district, (4) Fleming Camp area, (5) Pinos Altos 

district, (6) Shingle Canyon district, (7) Fierro-Hanover district, (8) 

Juniper Hill district, (9) Georgetown district, and (10) Central 

district. Interpretations of this sequence are complicated by the fact 

that Skate Canyon, Sheep Corral Canyon, and Circle Mesa may contain anomalies derived from ascending, heated, oxidizing meteoric 

waters; whereas, the others may result from cooled, descending 

(supergene) waters. Given the type of data used in this report, a 

definite distinction is not possible. 

COMPARISON OF GEOCHEMICAL HALOS 

The computer program element magnitude (EM) (VanTrump and 

Alminas, 1978) was used to compare halo characteristics between the 

anomalous areas (table 3). The values calculated by this program are 

similar in most respects to the linear productivity measurement 

(Beus and Grigorian, 1977, p. 94). The linear productivity is a 

measure of the size and intensity of the primary metal halo surrounding an orebody at a given vertical level. This measurement, which is 

expressed in meter-percent, is the product of the average anomalous 

value and the maximum lateral distance from the orebody. Compared 

at different vertical levels, the measurement provides both an index 

of metal zonation in the vertical plane and a quantitative method of 

comparing different metal deposits as to type and relative relationship to the surface on the basis of vertical metal zoning. The nonmagnetic heavy-mineral fraction contains the ore minerals that 

•Molybdenum is considered lithophilic in the upper lithosphere, but it also has a strong affinity for sulfur 

(Rankama and Sahama, 1950, p. 626-627). It is here considered with the chalcophilic elements because it forms the 

sulfide very readily. 
24 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

characterize the metallization at or near the level of erosion 

represented by the present land surface. This sample medium differs 

from metal values obtained through partial (enhanced) metal extractions from rock samples derived from surface· outcrops, which is the 

more common method of studying metal halos around mineral 

deposits (Beus and Grigorian, 1977, p. 78-90), only in that the orerelated metals contained in an alluvial heavy-mineral concentrate 

have been transported short distances as part of the mechanical 

stream-sediment load. This potential shortcoming in the method is 

mitigated somewhat by the fact that in most areas, particularly 

where known deposits or alteration exists, small drainage systems 

were sampled and the distances from the source outcrop are short. 

The heavy-mineral technique employed in this report should work 

well as a sensitive indicator of metal zonation because the enhancement of the ratio of anomaly to background contrast, as achieved by 

the heavy-mineral method, can increase the depth range to which 

covered mineral deposits can be detected by as much as 1.5 times 

(Beus and Grigorian, 1977, p. 154), in addition to broadening the 

target area. This increased sensitivity to metalized areas makes it 

possible to investigate subtleties of metal dispersion and in some 

cases to study metals that due to low analytical sensitivity would be 

inaccessible to studies of metal zoning. 

The EM measurement is a product of the element intensity, which 

is the ratio of anomaly mean to threshold and the areal size of the 

anomaly at constant threshold or lower limit of anomalous values. 

The theory and use of the method are further described in Van Trump 

and Alminas (1978). The method was conceived by H. V. Alminas of 

the U.S. Geological Survey. The EM measurement involves an areal 

measurement rather than a linear one, which is an advantage when 

ore-deposit centers are not known and drill data are not available. 

The area (shown in table 3) is a percentage value, proportional to the 

number of anomalous samples relative to those that are in 

background concentrations within the blocked-out window. Assuming a relatively uniform sample density, areal size (in m2 or km2) can 

be estimated by the product of sample density (m2 or km2/sample) and 

percentage value in table 3. Because sample density was not 

everywhere uniform, the areal size would not be realistic in the present study. The percentage value allows relative comparisons between areas without regard to sample density, assuming it is sufficient to characterize each area. 

Table 3 shows the EM values for the windows, which are ranked in 

a decreasing sequence based on the product areal size and anomaly to 

background contrast (intensity). 
GEOCHEMICAL INVESTIGATIONS 25 

RELATIVE EXPOSURE LEVEL 

In areas of variable erosion, mineralized zones may be exposed 

through a wide vertical range. Within the Silver City mining region 

there are probably some metal deposits which are exposed near their 

roots that consist of minable deposits that crop out but do not continue at depth; other deposits may be exposed near the midpoint of 

the productive ore zone and consist of minable deposits that may extend to moderate depth. Still other deposits may be only peripherally 

exposed and will be characterized by metal anomalies of the supraore 

(peripheral) metal suite which in some cases may even be related to 

small ore deposits of these metals. The peripheral metal suite would 

include such metals as lead, silver, barium, antimony, and others. In 

extreme instances, metal deposits may be buried to such a great 

depth that they are beyond the depth range or distal detection limit 

of the geochemical method. We attempted to assess these erosional 

factors within the study area. 

The comparisons made here are based on a simple model of metal 

zonation, which based on characteristics of the known mines, the 

geology and distribution patterns of the geochemical anomalies, 

seems to fit the Silver City mining region. In most metalliferous 

deposits that contain the metals lead, barium, and silver within a 

primary halo, dispersion patterns characteristically expand laterally 

and rise vertically above main orebody level; whereas, the primary 

dispersion patterns for the metals copper, molybdenum, and bismuth 

expand laterally at and below vertical level of the orebody until the 

roots are reached, at which point all metals wedge out. The metal 

suites characterizing these positions in the vertical zoning of metal 

dispersion are termed supraore and subore, respectively, in the usage 

of Beus and Grigorian (1977). Where the dispersed metals are also the 

ore metals sought, maximum halo size (lateral distance) and greatest 

metal enrichment are usually at the orebody level (Beus and 

Grigorian, 1977, p. 155). For example, at several stockwork 

molybdenum deposits, certain metals form typical enveloping halos, 

and the metal dispersion is zoned about the main ore zones (Wallace 

and others, 1978; Sharp, 1978). Sharp ( 1978, p. 373-376) showed drilled 

cross sections at a breccia pipe complex in Redwell Basin, Colo., in 

which a broad, primary lead halo at the surface wedges out 300-500 m 

above the main molybdenum orebody; a broad, primary zinc aureole 

occurs at the surface and terminates above the molybdenum orebody, 

and a tungsten halo occurs immediately above and overlaps the 

molybdenum orebody where maximum molybdenum dispersion occurs. Metal zonation is a common feature of most economic mineral 
26 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

deposits; it is not characteristic of dispersed subeconomic metal 

anomalies (Beus and Grigorian, 1977, p. 134-147). 

The amount of erosional exposure relative to several known or 

potential inner ore zones was assessed using element magnitude (EM) 

calculations for selected metals within the window areas. Calculations are based on the assumption that those halos dominated by the 

supraore metal suite are peripheral to or above the center of the metal 

zonation sequence; whereas, the subore suite is closer to the center of 

the metal system. The metal system model is simple and general but 

should embrace a variety of large deposit types, mostly related to igneous activity. The metals assumed to be peripherally dispersed 

(supraore) are lead, silver, and barium, and those assumed to be near 

to or within the inner metal zone are copper, molybdenum, and 

bismuth. The selection of metals was based on descriptions of the 

known deposits in the region and the documented behavior of these 

metals in an environment of hydrothermal mineralization and alteration elsewhere in the world. (See for example Beus and Grigorian, 

1977.) The additive element magnitudes (EM) of the peripherally 

dispersed metals (supraore) were then ratioed to the subore suite as 

shown in table 4. 

Table 4 shows a sequence whereby the window areas are ranked in 

order of decreasing ratio sum, which is believed to indicate an order 

of increasing depth of surface exposure due to erosion of the known or 

postulated inner metal zone (center of the metal system) within each 

of the areas. From the table, the least exposed deposits are in the 

Georgetown district and at Fleming Camp, which suggests that ore 

of the subore suite may be discovered at depth in these areas and that 

the silver produced in these two districts is supraore or peripheral. 

The calculations indicate also that the Fierro-Hanover district is 

eroded to a level of exposure that may be close to the roots of the 

main, inner metal zone, but the erosional level is not as deep in a 

southwestward direction toward the Central district, possibly 

because of a southwestward plunge of the ore zones. To check the 

validity of these experimental conclusions requires further assessment through more detailed investigations, including physical exploration, particularly at depth within the areas indicated to have 

high ratios. 

CONCLUSIONS 

The geochemical maps show that several relatively unexplored 

targets still exist within the Silver City mining region. Possibly 

foremost among these targets is that near Fleming Camp. Because 
GEOCHEMICAL INVESTIGATIONS 27 

the geochemical signature at Fleming Camp is similar to that of the 

skarn metalization at Pinos Altos, an intrusive body or cupola may 

be beneath the area at shallow depth. 

Other targets of interest include the following: (1) The Georgetown 

district, where molybdenum and copper halos are strong enough to 

suggest the presence of these metals at depth, especially because 

these subore metals, though enriched at surface level, are subordinate in enrichment to metals of the supraore suite. (2) The Pinos 

Altos district, where the surrounding metalized zone appears more 

extensive than was previously realized. Additional deposits may exist at a greater distance from the contact zone, particularly to the 

northwest and southeast. (3) The vicinity of Circle Mesa, where a 

deep exploration target, similar perhaps to the one at Fleming Camp, 

may exist. The presence of tungsten ~uggests that intrusive-related 

skarn or stockwork deposits may be present at depth. Intrusive 

bodies occur within the volcanic tuff units of this area, possibly these 

are cupolas of a larger intrusive body at depth. The geochemical 

signature suggests that heated meteoric water may have caused the 

anomalies. (4) Along both the Barringer and Mimbres fault zones, 

where metalization appears extensive and suggests the possibility of 

deposits at depth in association with these loci. (5) The Juniper Hill 

area, which contains geochemical anomalies of unknown significance. 

The lead and zinc distributions indicate that metallization may be 

closely related to the mineralized areas at Pinos Altos and may in 

fact be a weakly mineralized extension. If mineral deposits do exist, 

the exposure-level calculations indicate that erosion has not reached 

root levels. The altered sills in the area may have entrapped ore 

beneath them. (6) The Sheep Corral Canyon anomaly, the significance 

of which is unknown. The presence of sparse amounts of bismuth and 

other metals is encouraging, but more data are required to prove this 

area to be a deep exploration target. A large quartz vein was noted 

near the head of a drainage within the center of the area. This quartz 

vein may be the result of the remobilization of silica from depth as a 

consequence of host-rock alteration or replacement. (7) Skate Canyon, 

where the geochemical anomalies suggest past hot-spring activity 

and mobilization of carbonate from depth, possibly as a result of 

host-rock replacement. Though not shown on a map, but indicated in 

table 3, the area contains strong magnesium anomalies as well, which 

strengthens the case for replacement of Paleozoic rocks at depth, particularly if they happen to be dolomitic. 

The regional distribution of barium, zinc, and manganese 

presumably as hydrothermal halos is of particular interest because of 

the peripheral positioning of these metals to mineral districts and the 

possible usefulness of this relationship in exploration. The pro-
28 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

minence of these halos in the volcanic terrane suggests a genetic relationship to the volcanism. The distribution of barium (barite) in the 

nonmagnetic fraction may indicate the lateral periphery of metallized 

zones and ore-solution conduits in the more eroded terrane of the 

Silver City region and the top of the vertical metal zonation in the 

middle Tertiary volcanic terrane. The area north of Fierro and 

Georgetown contains a barium (barite) halo interpreted to be a product of mobilization and redeposition from hydrothermal alteration 

at depth. 

The erosion-level interpretations are experimental and are subject 

to numerous unseen factors that could affect conclusions. Although 

the results compare favorably with known geologic relationships, the 

actual metal concentrations and zonal relationships at depth are obviously unknown. Comparison of metal zonation between different 

areas may be a method whereby the most promising targets in a 

group of several regional- or district-scale geochemical anomalies can 

be selected for further investigation, according to sequential 

priorities. Some asf:lumptions may not be valid for all deposits in the 

region and there have out of necessity been simplifications, but the 

purpose is to glean the maximum information from geochemical data 

where there is no knowledge of the subsurface or where a geochemical 

anomaly does in fact indicate a buried deposit. Analogy is one way of 

approaching the interpretation. 

REFERENCES CITED 

Alminas, H. V., and VanTrump, George, Jr., 1978, Relative fraction magnitude pro· 

gram explanation and computer program listing: U.S. Geological Survey Open· 

File Report 78-1013, 23 p. 

Beus, A. A., and Grigorian, S. V., 1977, Geochemical exploration methods for mineral 

deposits: Willmette, Ill., Applied Publishing Ltd., 287 p. 

Cunningham, J. E., 1974, Geologic map and sections of the Silver City quadrangle, 

New Mexico: New Mexico Bureau of Mines and Mineral Resources Geologic Map 

30, scale 1:24,000. 

Entwhistle, L. P., 1944, Manganiferous iron-ore deposits near Silver City, New Mexico: New Mexico Bureau of Mines and Mineral Resources Bulletin 19, 72 p. 

Finnell, T. L., 1976a, Geologic map of the Twin Sisters quadrangle, Grant County, 

New Mexico: U.S. Geological Survey Miscellaneous Field Studies Map MF-779, 

scale 1:24,000. 

__ 1976b, Geologic map of the Reading Mountain quadrangle, Grant County, 

New Mexico: U.S. Geological Survey Miscellaneous Field Studies Map MF-800, 

scale 1:24,000. 

Grimes, D. J., and Marranzino, A. P., 1968, Direct-current arc and alternating-current 

spark emission spectrographic field methods for the semiquantitative analysis of 

geologic materials: U.S. Geological Survey Circular 591, 6 p. 
REFERENCES CITED 29 

Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in mineral exploration: New 

York, Harper and Row, 415 p. 

Hernon, R. M., 1953, Summary of smaller mining districts in the Silver City region, 

New Mexico, in New Mexico Geological Society Guidebook, 4th Field Conference, 

Southwestern New Mexico, p. 138-140. 

Hernon, R. M., Jones, W. R., and Moore, S. L., 1953, Some geological features of the 

Santa Rita quadrangle, New Mexico, in New Mexico Geological Society 

Guidebook, 4th Field Conference, Southwestern New Mexico, p. 117-130. 

Hewett, D. F., and Fleischer, Michael, 1960, Deposits of the manganese oxides: 

Economic Geology, v. 55, no. 1, 55 p. 

Holland, Heinrich D., and Malinin, Sergey D., 1979, The solubility and occurrence of 

non-ore minerals, in H. L. Barnes, ed., Geochemistry of hydrothermal ore deposits 

[2d ed.]: New York, John Wiley and Sons, p. 495-500. 

Jones, W. R., and Hernon, R. M., 1973, Ore deposits and rock alteration of the Santa 

Rita quadrangle, Grant County, New Mexico: National Technical Information 

Service Report PB-214-371, 102 p. 

Jones, W. R., Hernon, R. M., and Moore, S. L., 1967, General geology of the Santa 

Rita quadrangle, Grant County, New Mexico: U.S. Geological Survey Professional Paper 555, 144 p. 

Jones, W. R., Hernon, R. M., and Pratt, W. P., 1961, Geologic events culminating in 

primary metallization in the Central mining district, Grant County, New Mexico: 

U.S. Geological Survey Professional Paper 424-C, p. 11-16. 

Jones, W. R., Moore, S. L., and Pratt, W. P., 1970, Geologic map of the Fort Bayard 

quadrangle, Grant County, New Mexico: U.S. Geological Survey Geologic 

Quadrangle Map 865, scale 1:24,000. 

Kelly, W. C., 1958, Topical study of lead-zinc gossans: New Mexico Bureau of Mines 

and Mineral Resources Bulletin 46, 80 p. 

Kerr, P. F., 1940, Tungsten-bearing manganese deposit at Golconda, Nevada: 

Geological Society of America Bulletin, v. 51, p. 1359-1389. 

Korzhinskii, D. S., 1968, The theory of metasomatic zoning: Mineralium Deposita, v. 

3, p. 222-231. 

Krauskopf, Konrad B., 1967, Introduction to geochemistry: New York, McGraw-Hill, 

721 p. 

Lasky, S. G., and Wooten, T. P., 1933, The metal resources of New Mexico and their 

economic features: New Mexico Bureau of Mines and Mineral Resources Bulletin 

7,178p. 

Lasky, S. G., 1936, Geology and ore deposits of the Bayard area, Central mining 

district, New Mexico: U.S. Geological Survey Bulletin 870, 144 p. 

Levinson, A. A., 1974, Introduction to exploration geochemistry: Calgary, Alberta, 

Canada, Applied Publishing Company, Ltd., 612 p. 

McKnight, J. F., and Fellows, M. L., 1978, Silicate mineral assemblage and their relationship to sulfide mineralization, Pinos Altos mineral deposit, New Mexico: 

Arizona Geological Society Digest, v. 1, p. 1-8. 

Moore, S. L., 1953, Preliminary geologic map of the Allie Canyon quadrangle, Grant 

County, New Mexico: U.S. Geological Survey Open-File Report, 2 sheets, scale 

1:24,000. 

Motooka, J. M., and Grimes, D. J., 1976, Analytical precision of one-sixth order 

semiquantitative spectrographic analysis: U.S. Geological Survey Circular 738, 

25 p. 

Neuerburg, G. J., Barton, H. N., Watterson, J. R., and Welsch, E. P., 1978, A comparison of rock and soil samples for geochemical mapping of two porphyry metal 

systems in Colorado: U.S. Geological Survey Open-File Report 78-383, 26 p. 
30 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 

Olade, M.A., and Fletcher, W. K., 1976, Trace-element geochemistry of the Highland 

Valley and Guichon Creek batholith in relation to porphyry copper mineralization: Economic Geology, v. 71, no. 4, p. 733-748. 

Paige, Sidney, 1916, Description of the Silver City quadrangle, New Mexico: U.S. 

Geological Survey Atlas, Folio 199, 19 p. 

Palache, Charles, Bermon, Harry, and Frondel, Clifford, 1952, Dana's system of 

mineralogy [7th ed.]: New York, John Wiley and Sons, p. 275, 429-445. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry [1st ed.]: Chicago and 

London, University of Chicago Press, p. 13, 68, 626, 627, 629. 

Schmitt, H. A., 1939, The Pewabic Mine: Geological Society of America Bulletin v. 50, 

no. 5, p. 777-818. 

Sharp, J. E., 1978, A molybdenum mineralized breccia pipe complex, Redwell Basin, 

Colorado: Economic Geology, v. 73, no. 3, p. 373-376. 

Titley, S. R., 1964, Some behavioral aspects of molybdenum in the supergene environ· 

ment: American Institute of Mining and Metallurgical Petroleum Engineers 

Transactions, v. 299, p. 199-204. 

Trauger, F. D., 1972, Water resources and general geology of Grant County, New 

Mexico: New Mexico Bureau of Mines and Mineral Resources Hydrologic Report 

2, 211 p. 

VanTrump, George, Jr., and Alminas, H. V., 1978, Relative Element Magnitude program explanation and computer program listing: U.S. Geological Survey OpenFile Report 78-1014, 23 p. 

VanTrump, George, Jr., and Miesch, A. T., 1977, The U.S. Geological Survey RASSST A TP AC system for management and statistical reduction of geochemical data, 

in Computers in Geoscience, v. 3: Oxford, Pergamon Press, p. 475-488. 

Wallace, S. R., Mackenzie, W. B., Blair, R. G., and Muncaster, N. K., 1978, Geology of 

the Urad and Henderson molybdenite deposits, Clear Creek County, Colorado, 

with a section on a comparison of these deposits with those of Climax, Colorado: 

Economic Geology, v. 73, no. 3, p. 325-367. 

Watts, K. C., and Hassemer, J. R., 1980, Distribution and abundance of fluorite in 

stream-sediment concentrates, Silver City 1 ° x 2 ° quadrangle, New Mexico and 

Arizona, U.S. Geological Survey Miscellaneous Field Studies Map MF-1183C, 

scale 1:250,000. 

Watts, K. C., Hassemer, J. R., and Nishi, J. M., 1978a, Eastern Santa Rita 

quadrangle and western margin of Mimbres Valley, New Mexico: Journal of 

Geochemical Exploration, v. 9, no. 2/3, p. 175-186. 

Watts, K. C., Hassemer, J. R., Siems, D. F., and Nishi, J. M., 1978b, A statistical sum· 

mary and listing of the spectrographic analyses of heavy-mineral concentrates 

and conventional, sieved stream-sediment samples, Silver City area, New Mexico: 

U.S. Geological Survey Open-File Report 78-801, 247 p. 
FIGURES 3-22, 

TABLES 1-4 
32 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

t. >·: I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY-CRETACEOUS INTRUSIVF-5 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4 . Skate Canyon area 

5. Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 3.-Distribution of lead in the nonmagnetic fraction. Contours drawn at 1,000, 

2,000, 5,000, 7,000, and 10,000 parts per 

million; hachures indicate closed areas of 

lower values. In some places, contours are 

shifted as much as 1.1 km (one grid cell) from 

sample localities due to computer averaging 

technique. 

~ ~ 

0 

c: 

~ 00 

~ 

r::., 

J~ 

~ ttl 

~ 

t_xj 

00 

1--' 

J,.. 

C\j 

C\j 
34 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

[<u I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY-CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 4.-Distribution of lead in the magnetic 

fraction. Contours drawn at 500, 1,000, 2,000, 

5,000, 7,000, and 10,000 parts per million. In 

some places, contours are shifted as much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

Jo%j 

0 

c 

~ rn 

"" ~ 

~t:-.:) 

~ t:x:l 

~ rn 

...... 

~ 

Clj 

01 
36 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPLANATION 

1: i·: .. J QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY-CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMAUES 

1. Shingle Canyon district 

2 Georgetown district 

3. Fierro-Hanover district 

4. Skate Canyon area 

5. Central district 

6 . Sheep Corral Canyon area 

7. .Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 5.-Distribution of copper in the nonmagnetic fraction. Contours drawn at 100, 

200, 500, 1,000, 2,000, and 5,000 parts per 

million; hachures indicate closed areas of 

lower values. In some places contours are 

shifted as much as 1.1 km (one grid cell) from 

sample localities due to computer averaging 

technique. 

l'%j 

1-4 

0 

c:: 

~ 00 

co 

...::, 

~~ 

~ trl 

~ 00 

...... 

;... 

CAj 

-4 
38 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPLANATION 

I<_ ... :: \I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMAUES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat- Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 6.-Distribution of copper in the magnetic 

fraction. Contours drawn at 100, 200, 500, 

1,000, 2,000, and 5,000 parts per million; 

hachures indicate closed areas of lower 

values. In some places, contours are shifted 

as much as 1.1 km (one grid cell) from sample 

localities due to computer averaging technique. 

1-.rj 

0 

c 

~ 

t:r.:l 

C/1 

C.:> 

~ 

J~ 

~ txl 

~ C/1 

....... 

J:,.. 

00 

co 
40 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPlANATION 

!<< .. :·.: .. ~ QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TER~Y VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY-CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5. Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 7.-Distribution of zinc in the nonmagnetic fraction. Contours drawn at 700, 

1,000, 2,000, 5,000 and 10,000 parts per 

million; hachures indicate closed areas of 

lower values. In some places, contours are 

shifted as much as 1.1 km (one grid cell) from 

sample localities due to computer averaging 

technique. 

"'%j 

0 

c: 

~ r:n 

OJ 

~ 

.t-.:~ 

~ ttl 

~ r:n 

1-' 

.;,.. 

~ 

~ 
42 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPLANATION 

t . . > j QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY -CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT -Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE B.-Distribution of zinc in the magnetic 

fraction. Contours drawn at 700, 1,000, 2,000 

and 5,000 parts per million; hachures indicate 

closed areas of lower values; query within 

hachure indicates area of inadequate data. In 

some places, contours are shifted as much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

~ 

0 

c::: 

~ 

trl 

rn 

C.:l 

~ J-:l 

~ ttl 

~ rn 

..... 

J,. 

.,j::l.. 

Cr.:) 
44 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPlANATION 

!<.:.-;::·:.. ] QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 9.-Distribution of bismuth in the nonmagnetic fraction. Contours drawn at 50, 100, 

200, 500, and 700 parts per million. In some 

places, contours are shifted as much as 1.1 km 

(one grid cell) from sample localities due to 

computer averaging technique. 

"'%j 

0 

c 

~ en 

~ 

~ 

.!'=> 

~ ttl 

~ en 

t-' 

~ 

~ 

Ol 
46 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

I: .• ' I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 10.-Distribution of tungsten in the nonmagnetic fraction. Contours drawn at 150, 

200, 500, 1,000 and 2,000 parts per million. In 

some places, contours are shifted as much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

"%j 

C5 

c::: 

~ 

trl 

en 

~ 

.;, 

~t-.:) 

~ t:D 

~ en 

~ 

~ 

~ 

-.l 
48 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPLANATION 

t : .. ~ QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY-CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMAUES 

1. Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4 . Skate Canyon area 

5. Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE H.-Distribution of tungsten in the 

magnetic fraction. Contours drawn at 150, 

200, and 500 parts per million. In some places, 

contours are shifted as much as 1.1 kni lone 

grid cell) from sample localities due to computer averaging technique. 

~ 

s 

c:: 

~ r::n 

C.:> 

~ 

J~ 

~ t:C 

~ r::n 

...... 

~ 

~ 

co 
50 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

:~ .. :, -~ ~ QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY -CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5. Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 12.-Distribution of molybdenum in the 

non-magnetic fraction. Contours drawn at 50, 

100, 200, 500, and 700 parts per million. In 

some places, contours are shifted as much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

"%j 

8 

c: 

~ 00 

(J.J 

~ 

.t-:> 

~ t::C 

~ 00 

~ 

~ 

01 

1--' 
52 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPlANATION 

t >.:·: ~ QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 13.-Distribution of molybdenum in the 

magnetic fraction. Contours drawn at 50 and 

100 parts per million. In some places, contours are shifted as much as 1.1 km (one grid 

cell) from sample localities due to computer 

averaging technique. 

~ 

8 

c::: 

~ 

t.:rj 

en 

C;;) 

~ J-:l 

~ ttl 

~ en 

~ 

J.. 

c:.n 

c.o 
54 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPLANATION 

!: .. (: .. I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 14.-Distribution of silver in the nonmagnetic fraction. Contours drawn at 5, 15, 

50, 150, 500, and 1,500 parts per million. In 

some places, contours are shifted as much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

'":rj 

a 

c 

~ r:n 

C;.:l 

.;., 

J':> 

~ t::lj 

~ r:n 

....... 

J.. 

01 

01 
56 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPLANATION 

1-<·:_:.,j QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 15.-Distribution of silver in the magnetic 

fraction. Contours drawn at 5, 15, and 50 

parts per million. In some places, contours are 

shifted as much as 1.1 km (one grid cell) from 

sample localities due to computer averaging 

technique. 

"%j 

0 

c::: 

~ 00 

"" 

~ 

~1:-:1 

~ t::Jj 

t"" 

trj 

00 

1-' 

J,. 

01 

-;J 
58 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPLANATION 

t .. <:· J QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Orcle Mesa area 

FIGURE 16.-Distribution of gold in the nonmagnetic fraction. Contours drawn at 30, 50, 

and 70 parts per million. In some places, contours are shifted as much as 1.1 km (one grid 

cell) from sample localities due to computer 

averaging technique. 

"'%j 

1-4 

0 

e 

~ 

tr_j 

rn 

CoAj 

.;, 

J...:l 

~ ttl 

~ rn 

~ 

~ 

01 

~ 
60 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPlANATION 

t .: ._:j QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY-CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9 . Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 17.-Distribution of barium in the nonmagnetic fraction. Contours drawn at 2,000, 

3,000, 5,000 and 7,000 parts per million. In 

some places, contours are shifted as.much as 

1.1 km (one grid cell) from sample localities 

due to computer averaging technique. 

"'%j 

0 

c:: 

~ 

tr:l 

00 

"' ~ 

J'.:l 

~ to 

~ 00 

~ 

~ 

m 

....... 
62 GEOCHEMICAL HALOS, SILVER CITY MINING REG ION, NEW MEXICO 
EXPlANATION 

I u I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY -CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT - Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2 . Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5, Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE lB.-Distribution of barium in the 

magnetic fraction. Contours drawn at 2,000, 

3,000, and 5,000 parts per million. In some 

places, contours are shifted as much as 1.1 km 

(one grid cell) from sample localities due to 

computer averaging technique. 

l'%j 

8 

c 

~ en 

c.:> 

~ 

J-.:> 

~ tc 

~ en 

~ 

J,.. 

m 

~ 
64 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

t . .J QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

L Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4 . Skate Canyon area 

5. Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 19.-Distribution of manganese in the 

nonmagnetic fraction. Contours drawn at 

1,000, 1,500, 2,000, and 3,000 parts per 

million; hachures indicate closed areas of 

lower values. In some places, contours are 

shifted as much as 1.1 km (one grid cell) from 

sample localities due to computer averaging 

technique. 

lo%j 

0 

c::: 

~ 

trl 

UJ 

C&j 

~ 

~~'.:) 

~ ttl 

~ UJ 

...... 

~ 

m 

01 
66 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPLANATION 

I: :>: I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSIVES 

TERTIARY -CRETACEOUS INTRUSIVES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3 . Fierro-Hanover district 

4 . Skate Canyon area 

5 . Central district 

6 . Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districtc; 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 20.-Distribution of manganese in the 

magnetic fraction. Contours drawn at 5,000 

and 7,000 parts per million; hachures indicate 

areas of lower values; query within hachure indicates area of inadequate data. In some 

places, contours are shifted as much as 1.1 km 

(one grid cell) from sample localities due to 

computer averaging technique. 

~ 

0 

c:: 

~ 

trJ 

r::n 

CJ.:) 

~ 

J~..:> 

~ ttl 

~ 

trJ 

r::n 

1-' 

~ 

~ 

-.l 
68 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPLANATION 

!d. I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID-TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY-CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2 . Georgetown district 

3 . Fierro-Hanover district 

4. Skate Canyon area 

5 . Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat- Boston Hill districts 

8 . Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11 . Circle Mesa area 

FIGURE 21.-Distribution of tin in the nonmagnetic fraction. Contours drawn at 100, 

200, 500, and 1,000 parts per million. In some 

places, contours are shifted as much as 1.1 km 

(one grid cell) from sample localities due to 

computer averaging technique. 

l'%j 

8 

c 

~ rn 

<:.¢ 

~ 

~t-:> 

~ ttl 

~ rn 

~ 

~ 

m 

~ 
70 GEOCHEMICAL HALOS, SILVER CITY MINING REGION, NEW MEXICO 
EXPlANATION 

[>. >. I QUATERNARY-TERTIARY BASIN-FILL SEDIMENTS AND 

3 

PEDIMENT GRAVELS 

MID- TERTIARY VOLCANICS 

MID-TERTIARY INTRUSNES 

TERTIARY -CRETACEOUS INTRUSNES 

MESOZOIC-PALEOZOIC ROCKS-Includes small areas of 

Precambrian rocks 

CONTACT 

NORMAL FAULT-Dotted where concealed 

SAMPLE SITE 

MINING DISTRICTS AND OTHER GEOCHEMICAL ANOMALIES 

1. Shingle Canyon district 

2. Georgetown district 

3. Fierro-Hanover district 

4. Skate Canyon area 

5. Central district 

6. Sheep Corral Canyon area 

7. Chloride Flat-Boston Hill districts 

8. Fleming Camp area 

9. Pinos Altos district 

10. Juniper Hill area 

11. Circle Mesa area 

FIGURE 22.-Distribution of vanadium in the non- , 

magnetic fraction. Contours drawn at 500, 

1,000, and 2,000 parts per million. In some 

places contours are shifted as much as 1.1 km 

(one grid cell) from sample localities due to 

computer averaging technique. 

"rj 

8 

c 

~ 

tlj 

r.n 

~ 

~ J•.:> 

~ t:C 

~ r.n 

~ 

~ 

-::J 

........ 
Window area Geographic boundaries 

aeq mln s aea mln s 

Sh in gle Canyon district-------- 32 52 00 32 54 00 

108 03 00 108 04 30 

Georgetown district------------ 32 49 00 32 52 00 

108 00 00 108 03 00 

Fi erro -Hanover district-------- 32 49 00 32 51 00 

108 04 00 108 07 30 

Skate Canyon ------------------- 32 56 on 32 58 00 

108 06 00 108 09 30 

Central district--------------- 32 45 00 32 llQ 00 

108 05 00 108 11 00 

Sheep Corral Canyon------------ 32 56 30 33 00 00 

108 10 00 108 16 00 

Chloride Flat and Boston Hill 32 45 00 32 48 00 

districts. 108 15 00 108 18 00 

Fl eminq Camp-- ------------- ------ 32 46 00 32 51 00 

108 19 00 lOR 25 00 

Pinos Altos district------------- 32 47 30 32 54 00 

lOR 10 00 108 17 30 

Juniper Hill district------------ 32 52 00 32 56 00 

108 17 30 108 22 30 

Circle Mesa --------------------- 32 50 00 32 53 00 

108 26 30 108 29 00 

TABLE !.-Location and description of window areas 

Geo loa ic env ironment 

Ore localized in Pennsylvanian limestone 

beneath Perman and Pennsylvanian shales. 

Localized at intersection of Barrinqer 

and Mimbres faults. 

Ore localized in Silurian Fusselman 

Dolomite beneath Devonian Percha Shale. 

Near intersect ion Mimbres fault and 

northeast dike and fault trend extending 

outward from Santa Rita (Chino). 

Ore localized chiefly wi thin contact 

metamorphic zone (skarn) surroundina 

Laramide quartz d i or i te-qranod i or ite 

stock. 

Tertiary 

Ore localized hy faults dikes anrl 

fissures in Paleozoic carbonate 

rocks and shales. Trend of faults 

mainly northeast referred to as 

Groundhog Trend. 

Tert i ary volcanics cut by northwesttrendina block faults, intruded by 

rhyolite dikes and irreqular bodies. 

Ore localized by faults and fissures 

in Paleozo i c shales and carbonate 

rocks. Aq veins localized in 

Silurian Fusselman Dolomite beneath 

Devonian Percha shale. 

Ore localized as pods in Cretaceous 

Beartooth Quartz it e . 

Ore localized within Laramide quartz 

monzonite stock and within skarns 

deve l oped in Paleozoic carbonate s 

and shales and Cretaceous 

sandstones, shales, and andesite. 

Prospects on faults and fractures---

Tertiary tuffs and flows intruded by 

felsic plugs and dikes. 

Oepos it tyoe 

Replacement Zn-Pb-------------

Fissure vei ns and 

replacement Aq-Pb lodes. 

Restricted to oxide zone. 

Contact metamorphic 

Fe-Zn anrl skarn 

replacement Zn-Cu- Ph. 

None known --------------------

Vein deposits of Zn -

Cu-Pb-Aq and minor Au 

placers. 

None known-- ------------------

Weathered and leached Mn-Fe 

deposits at Boston Hill. Aq 

halide vein and replacement bodies 

at Chlor i de Flat. Restricted 

to ox i de zone. 

Aq halide replacement deposits. 

Restr i cted to oxide zone. 

Vein deposits Au-Aa-Cu-Pb-Zn 

within stock. Skarn-replacement 

Zn-Cu-Pb-Aa in surroundinq host 

rocks amd qold olacers. 

None known- -------------------

None known--------------------

Re f erences 

Ke ll y, lQSfl, p. 33 - 3fi; 

Jones and others, 1967. 

Lasky and Wooten, 1933, p. 5fi-57; 

Hernon, 1953, p. l3R- 140; 

Jones and others, 1% 1, l%7; 

Jones anrl Hernon, 1973. 

Lasky and Wooten, 1933, p . 52-53; 

Schmitt, 1Q39; 

Hernon anrl others, 1953; 

Jones anrl Hernon, 197 3 . 

Moore, 1953. 

Lasky and Wooten, 1Q.13, o. 51-5?; 

Lasky, 193fi; 

Jones anrl others, 19fi1, 19fi7; 

Jo nes and Hernon, 1Q73. 

Finnell, 197fia. 

Lasky and Wooten, 1933, o. 5?, 65 -fi6; 

Entwhistle, 1944; 

Hernon, 1953; 

Cunninqham, 1974. 

Lasky and Wooten, 1933, p . 56; 

Hernon, 1953, p. 138. 

Pa iae, l91fi; Lasky and Wooten, 

1933, p. 58-59; Hernon, 1951, 

p. 140; McKniqht anrl 

Fellows, 1Q7fl. 

None available. 

Trauqer, 1972. 

-:J 

~ 

0 

t_:l:j 

?5 

::X:: 

t_:l:j 

~ ~ 

0 

> t"'l 

::X:: 

~ 0 

sn 

00 

t_:l:j 

~ 

:;:tJ 

0 

~ ~ 

z 

z 

0 

~ 0 

~ 

0 

~ 

z 

t_:l:j 

~ 

~ t_:l:j 

~ ~ 

0 

0 
TABLE 2.-Ratio of fraction magnitudes for selected metals within the window areas 

[FM ratio= Anomaly intensity X area {M-lamp fraction) where Intensity= Anomaly mean; for the chalcophilic elements Aq, Bi, Cu, Mo, Pb, and Zn, this ratio may indicate, 

Anomaly 1ntens1ty X area (NM-iamp fract1on) lhreshold 

particularly in the mininq districts, the deqree to which sulfides and other ore minerals are weathered, sometimes redistributed and then fixed in the seconday oxirles of 

iron and manganese within the superqene zone. Hiqh ratios indicate a larqe factor for seconrlary processes; low ratio indicates a laroe factor for epiqenetic oreminerals and their secondary ore-mineral products; for 11 ithophile elements Mn, Ba, Be, Sn, and W, ratio is hiqh where element is predominately associated with various 

oxides of manganese and iron or magnetic primary minerals and low where discrete nonmaqnetic primary minerals of that metal are present in abundance. Threshold values 

are as in table 3. NM, indicates anomalous in nonmaqnetic fraction only and therefore may be equated with a value of 0; M, anomalous in maqnetic fraction only and 

therefore may be equated to an infinitely large number. ---,no anomaly; >, qreater than value shown] 

Window area 

Skate Can von-----------------------------

Circle Mesa------------------------------

Chloride Flat-Boston Hill district-------

Fleming Camp area------------------------

Pinos Altos district---------------------

Shingle Canyon district------------------

Fierro-Hanover district·-----------------

Mn Aq 

4.03 

8.50 

2.26 

13.57 

6 .2fi 

2.86 

8.00 

0.25 

0.005 

0.23 

NM 

NM 

Sheep Corral Canyon---------------------- 24.19 

Juniper Hill 

Georgetown district----------------------

Central district-------------------------

Ratio s umL-------------------------------

1chalcophil ic elements only; sinqle area. 

2sinqle element; all areas. 

13.49 

14.14 

5.91 

103.21 

0.02 

0.01 

0.03 

0.54 

Ba 

27 .no 

1. 98 

1.20 

0.67 

0.21 

NM 

NM 

0.14 

0.67 

NM 

0.12 

31.99 

Element 

Be Bi Cu 

NM --- 1.09 

1.33 --- 5.34 

3. 78 0.32 2.50 

0.47 n.o1 l.R3 

NM 0.18 1.77 

NM 0.50 0.59 

NM l.RO 

NM NM 2. 75 

4.22 NM 0.97 

M NM 0.31 

0.10 0.28 0.31 

>9 .90 1.29 1 9.2fi 

Ratio sum1 

Mo Pb Sn w Zn 

NM N"'1 --- 35 .Rn ~fi .R9 

NM NM M 29.Sl s .sn 10.84 

n.4R 0.3S M M ? .'i4 fi ,411 

0.1 g 0.77 n.3R 0.32 l.'iR 4.38 

n.ns 0.11 n .n3 n.n1 1. 22 3.5fi 

0.04 0.10 NM --- 2.22 3.45 

n.o1 n.n11 NM n. 7'> 1.15 3 .on 

NM NM NM --- M >2. 75 

0.22 0.;>2 NM 1.9'i 1.19 ? .fi2 

0.17 0. 39 0.40 --- 1.62 2.50 

0.02 0.16 NM NM 0.77 1.57 

1.18 2.14 >0 .81 >3~. 54 >53.S9 256.54 

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~ 

> t:C 

t'"' 

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00 

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CA:l 
TABLE 3.-Comparison of magnitudes for selected metals -l 

~ 

0 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maqnitude (EM) REM tr::l 

0 Element fraction value samples anoma 1 ous anomalous anomalous (mean/ (percent (Intensity (cumulative 0 

samples values value threshold) anomalous) X Area) percent ::I: 

maqnitude) tr::l 

a:: 

Georgetown district -

0 

> t:-t 

::I: 

Ag- ------ NM 5.0 35 21 24,015 1,144 228.71 60.00 13 '722 79 > 

Cu------- NM 100 35 26 25,100 965 9.65 74.29 717 4.1 

Pb------- NM 500 35 15 95,000 6,333 12.67 42.86 543 3.1 s 

sn Zn------- M 500 35 31 85,600 2,761 5.52 88.57 489 2.8 en Zn------- NM 500 35 13 52,800 4,062 8.12 37.14 302 1.7 -t:-t 

Co------- M 30 35 32 2,700 84 2.81 91.43 257 1.5 < 

tr::l IV!o------- NM 50 35 7 4,020 574 11.49 20.00 230 1.3 ~ Cu------- M 100 35 26 7,700 296 2.96 74.29 220 1.3 0 

Pb-------

V-------- NM 

M 500 

500 

35 

35 

14 

18 

36,700 

37,000 2,056 

2,621 

4.11 

5.24 40.00 

51.43 

210 

211 1.2 

1.2 -

~ Mn------- M 2,000 35 21 99,000 4, 714 2.36 60.00 141 0.8 a:: 

Ag------- M 5.0 35 9 242 27 5.38 25.71 138 0.8 -z 

N-------- M 500 35 20 12,100 605 1.21 '17.14 69 0.4 -z Mo------- M 50 35 9 690 76 1.53 25.71 39 0.2 0 Sn------- NM 100 35 7 1,250 179 1. 79 20.00 36 0.2 ~ 

Ba------- NM 2,000 35 4 20,000 5,000 2.50 11.43 29 0.2 tr::l 

0 

Bi-------

Sn-------

NM 

M 100 

50 

35 

35 

1 

3 

500 

350 

500 

117 2.33 

5 .on 

8.57 

2.86 14 

20 0.1 

0.1 -0 

Co------- NM 30 35 4 140 35 1.17 11.43 13 0.1 ~z 

Mg------- M 1.5 35 4 6.5 1.6 1.08 11.43 12 0.1 z 

tr::l 

Mq------- NM 1.5 35 3 6.5 2.2 1.44 8.57 12 () .1 ~ 

Mn------- MN 2,000 35 2 7,000 3500 1. 75 5. 71 10 0.1 a:: 

Be------- NM 15 35 1 15 15 1,000.0 2.86 3 0.0 tr::l 

>< -

0 Total Magnitude (EM)_ __________________ 17,438 0 
Fleminq Camp area 

Ag------- NM 5 83 18 19,292 1,072 214.36 21.69 4649 52 

Pb------- NM 500 83 38 277,200 7,295 14.59 45.78 fi!i8 7.4 

W-------- NM 100 83 30 43,700 1,457 14.57 36.14 527 5. 9 

Pb------- M 500 83 39 213,700 5,479 10.96 4fi.99 515 5.7 

Mo------- NM 50 83 25 15,990 640 12.79 30.12 385 4.3 

Bi------- NM 50 83 24 11,820 492 9.85 28.92 285 3.2 

Co------- M 30 83 79 6,830 86 2.88 95.18 274 1.1 

Mn------- M 2,000 83 66 380,000 5,758 2.88 79.52 229 2 .fi 

Zn------- M 500 83 52 77,000 1,481 2.96 62.65 186 2.1 

W-------- M 100 83 29 14,200 490 4.90 34.94 171 1.9 ~ ~ 

Mg- ------ MN 1.5 83 40 198 4.96 3.31 48.19 159 1.8 0 

Mg------- M 1.5 83 43 163 3. 79 2.53 51.81 131 1.5 ~ 

Zn------- NM 500 83 26 48,600 1,869 3.74 31.33 117 1.3 ~ 

t_::rj V-------- M 500 83 48 35,500 740 1.48 57.83 86 1.0 rn 

Ba------- NM 2,000 83 24 132,000 5,500 2.75 28.92 80 0.9 C.:l 

~ 

Mo------- M 50 83 29 2,980 103 2.06 34.94 72 0.8 _t-:1 

Cu------- M 100 83 35 5,400 154 1.54 42.17 65 0.7 

Be------- NM 15 83 22 770 35 2.33 21.51 fi2 0. 7 ~ Sn------- NM 100 83 15 5,000 333 3.33 18.07 60 0. 7 tJ:I 

t'-4 Ba- ------ M 2,000 83 21 88,000 4,190 2.10 25.30 53 O.fi t_::rj 

rn 

V-------- NM 500 83 13 15,900 1,223 2.45 15.66 38 0.4 ~ 

Cu------- NM 100 83 15 2,950 197 1.97 18.07 36 0.4 ~ 

Be------- M 15 83 17 365 21 1.43 20.48 29 0.3 

Ag------- M 5 83 6 104 17 3.47 7.23 25 0.3 

Au------- NM 20 83 7 390 S6 2. 79 8.43 23 0.3 

Sn------- M 100 83 4 1,900 475 4. 75 4.82 23 0.3 

Mn------- NM 2,000 83 11 28,110 2,545 1. 27 13.25 17 0.2 

Bi------- M 50 83 1 150 150 3.00 1.20 3.6 o.o 

Co------- NM 30 73 3 90 30 1.00 . 3.61 3.6 0.0 

Total Maqnitude (EM) __________________ 8,972 

-.;J 

01 
TABLE 3.-Comparison of magnitudes for selected metals-Continued 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maqn it ude (EM) REM -l Element fraction value samples anomalous anomalous anomalous (mean/ (percent (Intensity ( cumulative ~ 

samples values value threshold) anomalous) X Area) percent 0 maqnitude) t%j 

0 

{'") 

Central district ::c: 

t%j 

a:: 

~ 

Pb-------- NM 500 46 29 364,500 12,569 25.14 63.04 1585 24 {'") 

Cu-------- NM 100 46 32 46,550 1,455 14.55 69.S7 1012 lfi > Mo- ------- NM 50 46 14 14,550 1,039 20.79 30.43 633 9. 7 t"'4 

Ag-------- NM 5 46 15 1,377 92 18.36 32.fi1 599 9.2 ::c: Zn-------- NM 500 46 25 125,200 5,008 10.02 54.3S 544 fl. 3 > t"'4 

Zn-------- M 500 46 39 96,910 2,485 

0 

4.97 84.78 ll?l fi.4 sn Cu-------- M 100 46 33 14,350 435 4.35 71.74 312 4.8 r::n Co-------- M 30 46 45 4,160 92 3 .OR 97.83 301 4.fi ~ 

Pb-------- M 500 46 22 60,100 2,732 5.46 47.83 261 4.0 ~ Mn-------- M 2,000 46 34 195,000 5 ,73'1 2.87 73.91 212 3.2 t%j 

~ 

Sn-------- NlvJ 100 46 8 5,750 719 7.19 17.39 12"1 1.9 {'") 

Mg------ -- M 15 46 15 62 4 2. 78 32.fi1 91 1.4 ~ 

V--------- NM 500 46 12 20,200 1,683 3. 37 26.09 88 1.3 ~ Co-------- NM 30 46 14 1,150 82 2.74 30.43 83 1.3 a:: Ba-------- NM 2,000 46 13 68,000 5, 231 2.62 28.26 74 1.1 ~ 

z 

~ V--------- M 500 46 21 12,400 590 1.18 45.65 54 0.8 z Mn-------- NM 2,000 46 12 33,000 2,750 1.38 26.09 36 0.5 0 Be-------- NM 15 46 7 145 21 1.38 15.22 21 0.3 

Ag- ------- M 5 46 3 42 14 2.80 6. 52 13 0.3 ~ Ba-------- NM 50 46 3 350 117 2.33 6.52 15 0.2 0 

~ 

0 Mo- ------- M 50 46 3 270 90 1.80 6.52 12 0.2 ?! Mg-------- NM 1.5 46 4 6 1.5 1.00 8. 70 8. 7 0.1 z Ba-------- M 2,000 46 4 8,000 2,000 1.00 8. 70 8. 7 0.1 t%j 

Au-------- M 20 46 1 70 70 3.50 2.17 7.6 () .1 

Au-------- NM 20 46 2 40 20 1.00 4.35 4.4 0.1 ~ 

a:: Bi-------- M 50 46 1 100 100 2.00 2.17 4.4 0.1 t%j 

W--------- >< NM 100 46 1 150 150 1. 50 2.17 3. 3 0.0 ~ 

Be-------- M 15 46 1 15 1'i 1.00 2.17 2.2 0.0 0 

0 

Total Maqnitude ( EMl------------------- 6,536 
Pinos Altos district 

Cu-------- M 100 182 103 233,550 2,267 22.67 56.59 1,283 21 

Pb-------- NM 500 182 73 781,300 10,703 21.41 40.11 859 14 

Cu-------- NM 100 182 63 131 '900 2,094 20.94 34.62 725 12 

Ag-------- NM 5 182 53 6,290 119 23.74 29.12 691 11 

Mg- ------- M 1.5 182 179 1' 123 6.3 4.88 98.35 411 6.8 

W--------- NM 100 182 25 68,250 2,730 27.30 13.74 375 6.2 

Co-------- M 30 182 173 15,290 88 2. 95 95.05 280 4.6 

Bi -------- NM 50 182 40 21,740 543 10.87 21.98 239 ~.9 

Mn-------- M 2,000 182 158 676,000 4,278 2.14 86.81 Hlfi 3.1 

Ag- ------- M 5 182 24 1,428 59 11.90 13.19 157 2.6 "'%j 

Zn-------- NM 500 182 50 124,100 2,482 4. 96 27.47 136 2. 2 

-

0 

c:: Zn-------- M 500 182 37 101,900 2 '754 5.51 20.33 112 1.8 ~ V--------- M 500 182 139 91,900 661 1.32 76.37 101 1.7 t;rj 

Pb-------- M 500 182 30 86,700 2,890 5.78 16.48 95 1.6 00 

Mo- ------- NM 50 179 27 7,690 285 5. 70 15.08 86 1.4 Cr.:) 

~ ~ V--------- NM 500 182 26 60,100 2,312 4.62 14.29 1)6 1.1 ~ 

Au--------

Sn-------- NM 

NM 100 

20 182 

182 

12 

20 10,600 

1,760 147 

531 5.30 

7.33 

10.99 

6.59 48 

58 

0.8 

1.0 ~ t:C Bi-------- M 50 182 14 3,860 276 5.51 7.69 42 0.7 t-t 

Co-------- NM 30 182 26 2,110 81 2.71 14.29 39 0.6 t;rj 

00 

Mn-------- NM 2,000 182 30 108,000 3,600 1.80 16.48 30 0.5 ~ 

Ba-------- NM 2,000 182 32 108,000 3,375 1.69 17.58 30 0.5 J,.. 

Mg-- ------ NM 1.5 182 18 41 2.3 1.52 9.89 15 0.2 

Ba-------- M 2,000 182 7 23,000 3,286 1.64 3.85 6.3 0.1 

Mo-------- M 50 182 7 420 60 1.20 3.85 4.6 0.1 

W--------- M 100 182 5 600 120 1.20 2. 75 3.3 0.1 

Be-------- NM 15 182 4 65 16 1.08 2.20 2.4 0.0 

Sn-------- M 100 182 3 350 117 1.17 1.65 1.9 0.0 

Total Magnitude (EMl------------------~-6,083 

'I 

'I 
TABLE 3.-Comparison of magnitudes for selected metals-Continued -:J 

00 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maonitude (EM) REM 0 

Element fraction value samples anomalous anomalous anomalous (mean/ (percent (Intensity ( cumulative t%j 

samples values value threshold) anomalous) X Area) percent 0 

maqnitude) 0 

::I: 

t%j 

Chloride Flat-Boston Hill district =::: 

~ 

0 

> NM 500 17 15 109,700 7,313 14.63 88.24 1291 22 t-t Pb------- ::I: Ag------- NM 5 17 9 992 110 22.04 52.94 1167 20 > Pb------- M 500 18 14 41,000 2,929 5.86 77.78 456 7. 9 t-t Zn------- M 500 18 15 39,600 2,640 5.28 83.33 440 7.7 0 

Sn- ------ NM 100 17 6 6,350 1,058 10.58 35.29 374 6. 5 sn 

rn Co------- M 30 18 17 1,960 115 3.84 94.44 3fi3 11.3 ~ 

Ag- ------ M 5 18 8 264 33 6.60 44.44 293 'i.1 ~ Cu------- NM 100 18 14 4,500 321 3. 21 77.78 2'i0 4.4 t%j 

Zn------- Ni~ 500 17 7 14,700 2,100 4.20 41.18 173 3.0 ~ 

Mo------- NM 50 17 6 1,090 182 3.63 35.29 128 ? . 2 0 

~ 

Mn------- M 2,000 18 8 43,000 5,375 2.fi9 44.44 119 2.1 ~ Cu------- NM 100 17 5 1,700 340 3.40 29.41 100 1. 7 =::: Ba------- M 2,000 18 10 2,800 2,800 1.40 55.5fi 78 1.4 ~ 

z Mq------- NM 1.5 17 5 19 3.8 2.53 29.41 75 1.3 ~ 

V-------- M 500 18 9 5,900 656 1.31 50.00 66 1.1 z 

0 

Ba------- NM 2,000 17 5 22,000 4,400 2.20 29.41 65 1.1 ;; Mg- ------ M 1.5 18 8 16 2.1 1. 38 44.44 111 1.1 

Mo------- 0 M 50 18 8 550 68.8 1.38 44.44 61 1.1 ~ 

Mn------- NM 2,000 17 5 18,000 3,600 l.RO 29.41 53 0.9 0 

Au------- NM 20 17 2 100 so 2.50 11.76 29 0.5 ~ 

z 

W- ------- NM 100 17 2 400 200 2.00 11. 7fi 24 0.4 t%j 

Be------- M 15 18 4 60 15 1.00 22.22 22 0.4 ~ Bi------- NM 50 17 1 150 150 3.00 5.88 18 0.3 =::: V-------- NM 500 17 2 1,500 750 1.50 11.76 18 0.1 t%j 

Be------- NM 15 17 1 15 15 1.00 5.88 5. 9 0.1 >< Bi------- M 50 18 1 50 50 1.00 5.56 5 .fi 0.1 ~ 

0 

0 

Total Magnitude (EM) ___________________ 5,736 
Cu------- M 100 13 11 

Cu------- NM 100 13 11 

Mo------- NM 50 13 5 

Pb------- NM 500 13 8 

Bi------- NM 50 13 3 

Mn------- M 2,000 13 13 

Co------- M 50 13 13 

Ag------- NM 5 13 4 

Zn------- M 500 13 7 

Zn------- NM 500 13 3 

Sn------- Nt~ 100 13 4 

Au------- NM 20 13 1 

Mg------- NM 1.5 13 5 

Mg------- M 1.5 13 6 

Co------- NM 30 13 5 

Ba------- NM 2,000 1J 2 

Mn------- NM 2,000 13 3 

Pb------- M 500 13 3 

V-------- M 500 13 2 

W-------- NM 100 13 2 

W- ------- M 100 13 1 

Mo------- M 50 13 1 

Hanover-Fierro district 

15,900 1,445 14.45 84.62 122~ 

8,850 805 8.05 84.62 fi81 

3,700 740 14.80 38.46 569 

35,200 4,400 8.80 61.54 542 

2,250 750 15.00 23.08 346 

72,000 5,538 2.77 100.00 277 

940 72 2.41 100.00 241 

145 3fi 7.25 30.77 223 

10,900 1, 557 3.11 53.85 lfi8 

9,500 3,167 6.33 23.08 146 

1,650 412 4.13 30.77 121 

200 210 10.00 7.69 77 

14 2.8 1.87 38.46 72 

13 2.2 1.50 46.15 fi9 

230 46 1. 53 38.46 1)9 

12,000 6,000 3.00 15.38 46 

9,000 3,000 1.50 23.08 35 

1,500 SOO 1.00 ;:>3.08 23 

1,200 600 1.20 15.38 18 

200 100 1.00 15.38 15 

150 150 1.50 7.69 12 

50 50 1.00 7.69 7. 7 

Total Maqnitude (EM) ___________________ 4,971 

24 .fi 

13.7 

11.4 

10.9 

7.0 

5 .fi 

4.8 

4. s 

3.4 

2. 9 

2.6 

l.S 

1.4 

1.4 

1.2 

0.9 

0. 7 

0.5 

0.4 

0.1 

0. 2 

0.2 

~ -

0 

c::: 

~ 

t;rj 

00 

c.:l 

~ 

~ 

~ 

~ t:Jj 

~ 00 

...... 

J,.. 

-.:J 

co 
TABLE 3.-Comparison of magnitudes for selected metals-Continued 00 

0 

0 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maqnitude (EM) REM t_:rj 

0 Element fraction value samples anomalous anomalous anomalous (mean/ (percent (Intensity (cumulative a 

samples values value threshold) anornal ous) X Area) percent ::I: 

maqnitude) t_:rj 

a:: 

Shinqle Canyon district -

a 

> t"" 

::I: 

Pb------- NM 500 17 11 86,000 7,818 15.64 64.71 1,012 25 > 

Co------- M 30 17 17 2,970 175 5.82 100.00 582 15 t"" 

Zn------- M 500 17 15 31,100 2,073 4.15 88.24 366 9.2 0 

Cu------- NM 100 17 12 6,150 512 5.13 70.59 362 9.1 sn Mn------- M 2,000 17 13 80,000 6,154 3.08 7n.47 235 5. g r:n 

-t"" 

Cu------- M 100 17 13 3,650 281 2.81 76.47 215 'i.4 < t_:rj V-------- NM 500 17 9 18,200 2,022 4.04 52.94 214 5.4 ~ Mg------- M 1.5 17 6 45 7.5 5.00 35.29 176 4.4 a 

Mo-------

Zn-------

NM 

NM 500 

50 17 

17 

3 

9 14,000 

1,270 

1,556 

423 8.47 

3.11 

17.65 

52.94 165 

149 

4.1 

3.8 -

~ Ag- ------ NM 5.0 17 4 90 22 4.50 23.53 105 2. 7 a:: 

Pb------- M 500 17 7 8,700 1,243 2.49 41.18 102 2.6 -

z Mn-------

Co-------

NM 2,000 17 8 28,000 3,500 1. 75 47.06 82 2.1 -z NM 30 17 5 350 70 2.33 29.41 69 1.7 0 V-------- M 500 17 7 4,600 657 1.31 41.18 54 1.4 ~ 

Mg------- NM 1.5 17 1 5 

t_:rj 

5.0 3.33 5.88 20 O.'i 0 

Ba-------

Sn-------

NM 

NM 

2,000 

100 

17 

17 

1 

1 

5,000 

300 

5,000 

300 3.00 

2.50 5.88 

5.88 

15 

18 

0.4 

0.4 -0 

Bi------- NM 50 17 1 100 100 2.00 5.88 12 0.3 ~ 

Be------- NM 15 17 1 15 15 1.00 5.08 5.9 0.1 z 

t_:rj 

Bi ------- M 50 17 1 50 50 1.00 5.88 5. 9 0.1 ~ Mo------- M 50 17 1 50 50 1.00 5.88 5.9 0.1 a:: 

t_:rj 

>< 

Total Magnitude (EM)_ ____________________ 3,971 -

a 

0 
Juniper Hill district 

Ag- ------ NM 5 77 12 2,270 189 37.8~ 15.58 li90 2~ 

Pb------- NM 500 77 14 147,500 10,536 21.07 18.18 3R3 15 

Co------- M 30 79 69 1),420 79 2.62 87.34 229 9.0 

Mg------- M 1.5 79 50 261 5.2 3.49 63.29 221 R. 7 

Mn------- M 2,000 79 60 346,000 5,767 2.88 75.91i 219 lUi 

Mg------- NM 1.5 77 23 190 8.3 5.51 29.87 1Fi4 fi.5 

V-------- M 500 79 58 45,900 791 1. 58 73.42 116 4.fi 

Zn-- ----- M 500 79 46 42,800 930 1.86 58.23 108 4.3 

Zn------- NM 500 77 11 35,000 3,819 6. 36 14.29 91 3.fi 

Mo---- --- NM 50 75 7 3,240 463 9.26 9.33 Rfi 3.4 "'%j -0 

Pb- ------ M 500 79 17 33,200 1, 953 3.91 21.52 84 3.3 c::: Ba------- NM 2,000 77 18 86,000 4,778 2.39 23.38 56 2.2 :;:c 

Ba------- M 2,000 79 19 59,000 3 105 1.55 24.05 37 1.5 t_%j 

r:n V-------- NM 500 77 11 11,900 1 082 2.16 14.29 31 1.2 c.., 

Mo- ------ M 50 79 8 740 92 1.85 10.13 19 0.7 ~ 

~~ 

Mn------- NM 2,000 77 8 25,000 3,125 1.56 10.39 16 O.fi t-3 Cu------- NM 100 77 7 1,250 179 1. 79 9.09 16 0.6 > Cu------- M 100 79 9 1,250 139 1.39 11.39 16 0.6 t:C 

Ag------- M 5 79 7 53 7.6 1.51 8.8fi 13 0.5 t"" 

t_%j 

Be------- M 15 79 7 130 18.6 1.24 8.86 11 0.4 r:n 

W- ------- M 100 79 3 600 200 2.00 3.80 7.6 0.3 

-

J,... 

Au------- NM 20 77 2 80 40 2.00 2.60 5.2 0.2 

Bi------- NM 50 77 2 200 100 2.00 2.60 5.2 0.2 

W-------- NM 100 77 3 300 100 1.00 3.90 3.9 0.2 

Be------- NM 15 77 2 30 15 1.00 2.60 2 .fi 0.1 

Co------- NM 30 77 2 60 30 1.00 2.60 2.6 0.1 

Sn------- NM 100 77 1 100 100 1.00 1.30 1.3 0.1 

Total Maqnitude (EM) ____________________ 2,534 

00 

1-' 
00 

t...:> 

0 

tz:j 

0 

C".) 

TABLE 3.-Comparison of magnitudes for selected metals-Continued ::t: 

tz:j 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maqnitude (EM) REM 0 == Element fraction value samples anomalous anomalous anomalous (mean/ (percent (Intensity (cumulative > 

samples values value threshold) anomalous) X Area) percent t:"' 

maqnitude) ::t: 

> 

Skate Canyon s 

sn 

en 

~ 

Co M 30 25 25 4,870 195 6.49 100.00 fi49 29 t:"' 

<! Mg M 1.5 25 25 146 5.8 3.89 100.00 381 18 .tz::l 

Mn M 2,000 25 16 129,000 8,063 4.03 64.00 258 12 ~ 

v M 500 25 24 23,000 958 1.92 96.00 184 8.4 C".) 

Zn M 500 25 19 17' 900 942 1.88 76.00 143 6.5 ~ 

~ Mg NM 1.5 25 10 40 4.0 2. 70 40.00 108 ll.9 

== Ba M 2,000 25 7 54,000 7' 714 3.86 28.00 108 4.9 ~ 

Sn NM 100 25 3 1,900 633 6.33 12.00 76 3.5 z 

Mn NM 2,000 25 11 32,000 2,909 1.45 44.00 fi4 2.9 -

z 

Co NM 30 25 3 380 127 4.22 12.00 ~1 ? .3 0 

~ 

Cu M 100 25 6 1,250 208 2.08 24.00 50 2.3 tz:j 

Cu NM 100 25 4 1,150 287 2.88 16.00 46 2.1 0 

~ Pb NM 500 25 2 3,000 1,500 3.00 8.00 24 1.1 0 

v NM 500 25 4 2,700 675 1.35 16.00 22 1.0 ~z Be NM 15 25 4 70 17 1.17 16.00 19 0.8 z 

2,000 1 1.00 

tz:j 

Ba NM 25 2,000 2,000 4.00 4.0 0.2 ~ Zn NM 500 25 1 500 500 1.00 4.00 4.0 0.2 

== tz:j 

Total Magnitude (EMl---------------------2,199 >< 

~ 

C".) 

0 
Mg------ M 1.5 41 38 

Co------ M 30 41 41 

Mn------ M 2,000 41 36 

Sn------ NM 100 41 7 

Zn------ M 500 41 22 

V------- M 500 41 31 

Mg------ NM 1.5 41 7 

Bi------ NM 50 41 2 

Cu------ M 100 41 16 

Ba------ NM 2,000 41 12 

Co------ NM 30 41 5 

Cu------ NM 100 41 5 

Pb------ NM 500 41 5 

Mn------ NM 2,000 41 2 

Ba------ M 2,000 41 1 

Mo------ NM 50 41 1 

V------- NM 500 41 1 

Be------ NM 15 41 1 

Sheep Corral Canyon 

310 8.2 5.45 92.68 505 

4,570 111 3.72 100.00 372 

242,000 6,722 3.36 87.80 295 

5,600 800 8.00 17.07 137 

23,000 1,045 2.09 53.66 112 

22,300 719 1.44 75.61 109 

57 8.1 5.43 17.07 Q3 

1,800 900 18.00 4.88 88 

2,750 172 1. 72 39.02 67 

36,000 3 000 1.50 29.27 44 

430 86 2.87 12.20 35 

1,000 200 2.00 12.20 24 

4,400 880 1. 76 12.20 21 

10,000 5,000 2.50 4.88 12 

5,000 5,000 2.50 2.44 6.1 

70 70 1.40 2.44 3.4 

700 700 1.40 2.44 3.4 

15 15 1.00 2.44 2.4 

Total Maqnitude (EM)--------------------- 1,929 

26 

19 

15.3 

7.1 

5.8 

5.fi 

4.8 

4.6 

3.5 

2.3 

1.8 

1.3 

1.1 

0.6 

0.3 

0.2 

0.2 

0.1 

~ 

-0 

c:: 

~ 

tz::l 

en 

c,., 

~ ~ 

-

~ l:rl 

t-t 

tz::l 

en 

~ 

~ 

00 

c.., 
00 

~ 

0 

tr:l 

0 

0 

::r: 

tr:l 

Concentrate Threshold Number of Number of Sum of Mean Intensity Area Maqnitude (EM) REM ~ Element fraction value samples anomalous anomalous anomalous (mean/ (percent (Intensity ( cumulative -

0 samples values value threshold) anomalous) X Area) percent 

maqnitude) > t-t 

::r: 

> Circle Mesa t-t 

0 

sn 

Co------- M 30.0 21 21 1,610 77 2.56 100.00 2'16 19 00 

Ba-------

Mn-------

M 

M 

2,000. 

2,000. 

21 

21 

16 

10 

79,000 

68,000 

4,937 

6,800 3.40 

2.47 76.19 

47.62 

188 

162 

14 

12 -

~ W- ------- M 100. 21 12 2,9SO 246 2.46 57.14 140 10 tr:l 

Sn------- NM 100. 21 6 2,700 450 4.50 28.57 129 9.5 ~ 

0 

V--------

Ba-------

NM 

NM 2,000. 

500. 21 

21 

21 

5 

11,600 

40,000 8,000 

553 

4.00 

1.10 100.00 

23.81 

110 

95 

8.2 

7.0 

-

~ Zn------- M 500. 21 17 9,400 552 1.11 80.95 90 fi.6 ~ 

Pb------- M 500. 21 10 8,100 810 1.62 47.62 77 5. 7 -z Cu------- M 100. 21 7 800 114 1.14 33.33 38 2.8 -z l~n------- NM 2,000. 21 3 8,000 2,667 1.33 14.29 19 1.4 0 

Cu-------

Zn------- NM 

NM 

500. 

100. 

21 

21 

3 

1 

1,700 

150 

567 

150 

1.13 

1.50 

14.29 

4.76 

16 

7.1 

1.2 

0.5 ~ 0 Be------- M 15. 21 1 20 20 1.33 4.76 6.4 0.5 

Be------- NM 15. 21 1 15 15 1.00 4.76 4.8 0.4 -

0 

~ Mo------- NM 50. 21 1 50 50.000 1.00 4.76 4.8 0.4 

V-------- NM 500. 21 1 500 500.000 1.00 4.76 4.8 0.4 ~ W-------- NM 100. 21 1 100 100.000 1.00 4.76 4.8 0.4 ~ 

~ 

tr:l 

Total Maqnitude (EM)---------------------1,348 ~ 0 

0 
FIGURES 3-22, TABLES 1-4 

TABLE 4.-Additive ratios of element 

magnitudes (EM) 

[EM = Intensity X halo size (area). Leaders (-) 

indicate no value calculated] 

Area 

1

Pb + Ag + Ba 

Cu + Mo + Bi 

Georgetown district ......... . 

Fleming Camp area ......... . 

Chloride Flat-Boston Hill 

district ................... . 

Juniper Hill district ......... . 

Circle Mesa ................ . 

Shingle Canyon district ...... . 

Central district . . . . . . . . . .... . 

Pinos Altos district . . . . . . ... . 

Fierro· Hanover district ...... . 

Skate Canyon2 ••••••••••.••• 

Sheep Corral Canyon2 •••••••• 

'Nonmagnetic component. 

14.78 

12.82 

10.26 

9.54 

8.00 

3.89 

1.54 

1.50 

0.51 

'Statistically nonsignificant due to insufficient number of 

values. 

-tr U. S. GOVERNMENT PRINTING OFFICE: 1984-776-041/4021 REGION NO. 8 

85