Distribution of Gold 

• 

Ill Igneous Rocks 

By DAVID GOTTFRIED, JACK ]. ROWE, and ROBERT I. TILLING 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 727 

An investigation of the abundance and 

distribution of gold in plutonic and volcanic 

rocks of diverse magma types and tectonic settings 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1972 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

W. A. Radllnskl, Acting Director 

Library of Congress catalog-card No. 7o-184860 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 50 cents (paper cover) 

Stock Number 2401-2023 

{ 
CONTENTS 

Abstract -~---------------------------------------

Introduction -------------------------------------

Acknowledgments ------~------------------------­

Analytical procedure ------------------------------

Precision ------------------------------------

Accuracy ------------------------------------

Contamination effects -------------------------

Gold content in plutonic rocks ----------,-----------

Calc-alkalic provinces -------------------------

Alkalic provinces ----------------------------- Gold content in basaltic associations __ .;. ____________ _ 

Oceanic provinces ----------------------------

Hawaiian Islands ---~---------------------

Mid-Atlantic Ridge and East Pacific Rise ___ _ 

Continental provinces -------------------------

Plateau basalts and associated rocks, Oregon 

and VVashington ------------------------ Basalts of the Snake River Group and associated rhyolitic rocks, Idaho --------------

Greenstone Flow, Michigan ----------------

Hypabyssal (diabase) provinces ---------------

Triassic basin, Eastern United States _____ _ 

Precambrian diabase, southeastern Missouri_ 

Great Lake intrusion~ Tasmania -----------

Gold content in basalt-andesite-rhyolite associations __ 

Calc-alkalic provinces -------------------------

Cascade Range and adjacent areas, Oregon 

and California -------------------------

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Gold content in basalt-andesite-rhyolite associationsContinued 

Calc-alkalic provinces~Continued 

Jemez Mountains, N. MeX--------------'---

Yellowstone National Park, VVyo., and vicinity_ 

Precambrian metavolcanic rocks, central Arizona ---------------------------------- Beatty area, Nevada ---------------------

Challis Volcanics-, central Idaho -----------

Southern Appalachians, Virginia and North 

Carolina -------------------------------

Alkalic provinces ----------------------------- Big Bend National Park, Tex _____________ _ 

Boxelder and Shonkin Sag laccoliths, Montana_ 

Summary discussion of gold in volcanic associations __ 

Mode of occurrence of gold in igneous rocks --------

Abundance level in minerals ------------------

Distribution of gold between minerals in a rock_·_ 

Bearing of primary gold abundance on gold mineralization -------------------------------------

Boulder batholith region, Montana -------------

Dillsburg and Cornwall. districts, Pennsylvania __ 

J eronie district, central Arizona --------------- Bullfrog district, Nye County, Nev ____________ _ 

The Mother Lode, California ------------------

Thermal springs, Yellowstone National Park, VVyo _______________________________________ _ 

References ------------~--------------------------

ILLUSTRATIONS 

FIGURE 1. Schematic representation of tests of reproducibility of gold determinations of three rhyolites and one 

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quartz. monzonite --------------------------------------------------------------------------- 4 

2. Histograms of gold contents of some plutonic rocks of the VVestern United States _______ ..:._____________ 7 

3. Composite histograms of gold content of calc-alkalic and alkalic plutonic rocks; provenance not considered_ 8 

4. Histograms of gold content of rocks in some basaltic associations from oceanic provinces -------------- 10 

5. Histograms of gold conterit of rocks from some continental basaltic provinces of the United States______ 11 

6. Histograms of gold content of rocks _from some hypabyssal (diabase) provinces of the United States 

and Tasmania ------------------------------------------------------------------------------ 13 

7. Graphs showing· variation in gold and copper abundance with mafic index and depth of samples from the 

Great Lake shee~ Tasmania ---------------------------------------------------------------- 14 

8. Histograms of gold content of rocks from some calc-alkalic and basalt-andesite-rhyolite associations_____ 18 

9. Histograms of gold content of rocks· from some provinces ------------------------------------------ 20 

10. Graph showing variation of gold abundance with copper abundance of samples from four basaltic suites__ 22 

11. Graph showing variation of gold content with copper content in altered samples of Butte Quartz Mon12. 

zonite from underground workings, Butte district, Montana _____ :_ ________________________ _:_____ 26 

Graph showing positive correlation of secondary sericite with gold abundance for samples from two 

intrusions in Uzbekistan, U.S.S.R.------------------------------------------------------------ 27 

13. Triangular diagram showing normative plagioclase, orthoclase, quartz, and variation in gold content of 

Precambrian rhyolites and quartz porphyry of the Yavapai Series, central Arizona ---------------- 28 

III 
IV 

TABLES 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9-13. 

14. 

15. 

16. 

17. 

18-26. 

27. 

28. 

29. 

30. 

31. 

32. 

33. 

34-44. 

CONTENTS 

TABLES 

Replicate determinations of gold in selected igneous rocks ------------------------------------------

Reproducibility of gold determinations on splits and composites of selected igneous rocks --------------

Selected literature pertinent to the plutonic samples analyzed ---------------:------------------------

Summary of distribution of gold in various plutonic provinces --------------------------------------

Distribution of gold in calc-alkalic and alkalic plutonic rocks generalized according to rock type regardless of province ----------------------------------------------------------------------------- Summary of gold content in basaltic associations ---------------------------------------~---------­

Summary of gold content in basalt-andesite-rhyolite associations ------------------------------------

Average gold content in selected rocks representative of different volcanic associations ----------------

Distribution of gold in9. Minerals of some rocks from the Southern California batholith ------------------------------

10. Minerals of some rocks from the Boulder batholith, Montana -------------------------------

11. Minerals of some rocks from the Sierra Nevada batholith and Coast Range plutons, California __ 

12. Minerals of a sample of the Silver Plume Granite, Silver Plume, Colo ______________________ _ 

13. Different density fractions of some samples of Butte Quartz Monzonite from underground 

workings --------------------------------------------------------------------------- Distribution of gold and copper in a drill core in Butte Quartz Monzonite, Butte district, Silver Bow 

County, Mont--------------------------------------------------------------------------------

Distribution of gold and copper in some samples of Butte Quartz Monzonite from underground workings 

in the Butte district, Montana ---------------------------------------------------------------

Comparison of gold concentration in samples of host rocks from the Mother Lode district with samples 

from the Sierra Nevada batholith ------------------------------------------------------------

Ranges of gold content in rhyolite, thermal water·s, and precipitates from thermal waters, Yellowstone 

National Park, VVyo--------------------------------------------------------------------------

Distribution of gold in18. Rocks of the Southern California batholith _____ :._ _________________________________________ _ 

19. Rocks of the Sierra Nevada, Coast Range, and Transverse Ranges, Calif_ ____________________ _ 

20. Rocks of the Idaho batholith -------------------------------------------------------------

21. Rocks of the Boulder batholith, Montana -------------------------------------------------- 22. Rocks of the Tatoosh pluton, Mount Rainier National Park, VV ash __________________________ _ 

23. Four· plutonic rocks from the Rocky Mountains, Colo _______________________________________ _ 

24. Plutonic rocks of the White Mountain Plutonic Series, New Hampshire ----------------------

25. Some alkalic plutonic rocks from North Carolina and South Carolina ------------------------

26. Volcanic rocks from Hawaii -------------------------------------------------------------

Distribution of gold and copper in volcanic rocks from the Mid-Atlantic Ridge and East Pacific Rise ___ _ 

Distribution of gold in plateau basalts and other volcanic rocks, Oregon and Washington -----------

Distribution of gold in basalts of the Snake River Group and associated rhyolitic rocks, Idaho _________ _ 

Distribution of gold and copper in the Greenstone Flow of the Michigan copper district ----------------

Distribution of gold in basalt and diabase from the Triassic basin, Eastern United States ------------- Distribution of gold in Precambrian diabase intrusions, Iron County, Mo _____________________________ _ 

Distribution of gold and copper in the Great Lake intrusion, Tasmania ---~-------------------------­

Distribution of gold in34. Volcanic rocks of the VVestern Cascades, Oreg _____________________________________________ _ 

35. Volcanic rocks of the Southern High Cascades, Calif., and vicinity -------------------------- 36. Some rhyolites from Mono County, Calif_ ________________________________________________ _ 

37. ·Volcanic rocks of the Jemez Mountains, N. Mex ___________________________________________ _ 

38. Volcanic rocks from Yellowstone National Park, Wyo., and vicinity --------------------------

39. Metamorphosed Precambrian silicic volcanic rocks in central Arizona ------------------------

40. Volcanic rocks from the Beatty area, Nevada ------~---------------------------------------

41. Some samples of the Challis Volcanics, central Idaho --------------------------------------

42. Some calc-alkalic metavolcanic rocks from the southern Appalachians, North Carolina and 

Virginia ---------------------------------------------------------------------------- 43 .. Alkalic igneous rocks from Big Bend National Park, Tex __________________________________ _ 

44. Subsilicic alkalic rocks from central Montana --------------------------~-----------------

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DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

By DAVID GOTTFRIED, JACK J. ROWE, and ROBERT I. TILLING 

! ___ _ 

ABSTRACT 

New data on gold content are presented for abo~t 700 

igneous rocks from various petrographic provinces, which 

represent different magma types from widely different geographic areas and tectonic settings. The gold content was 

determined by neutron-activation analysis combined with 

fire assay for radiochemical separation of gold. The method 

yields results reproducible to ± 10 percent .in the range 

above 1 ppb (part per billion) gold; below 1 ppb the reproducibility drops to ± 30 percent. 

In the Mesozoic-lower Tertiary calc-alkalic batholiths 

from the Western United States (the Southern California, 

Sierra Nevada, Idaho, and Boulder batholiths), the highest 

gold content (as much as 10 ppb) occurs in some of the 

gabbroic and tonalitic rocks of the Southern California 

batholith. The felsic members of each of the batholiths 

generally contain from 0.5 to 1.5 ppb gold. Plutonic rocks, 

ranging from gabbro to granite in alkalic provinces of the 

Eastern United States (White Mountain Plutonic Series in 

New· Hampshire and Piedmont physiographic province in 

the southern Appalachians) are characterized by low gold 

content. Limited data on the gold content in some major 

and accessory minerals indicate that relatively higher gold 

concentration is associated with pyrite, magnetite, and 

mafic . silicates than with the felsic minerals. The apparent 

affinity of gold for early crystallizing minerals is consistent 

with the overall trend of progressive depletion of gold from 

mafic to silicic rocks. 

The suites of basaltic rocks studied include tholeiitic, lowK20-high-Ab03, and alkalic basalts from continental as well 

as oceanic environments. Alkalic basalts appear to have distinctly lower gold content ( ,_ 0.6 ppb) than most Hawaiian 

and continental basalts of the tholeiitic magma type (2-3.5 

ppb). Low-K20 basalts from the oceanic ridges o{ the Atlantic and Pacific Oceans have lower gold content (-- 0.6 ppb) 

than chemically similar basalts from North Carolina and 

northern California. In the Triassic province of the Eastern 

United States, samples from the diabase-granophyre suite 

from Dillsburg, Pa., contain three to four times more gold 

than undifferentiated basalts from elsewhere in the province and may be the result of remobilization or later introduction. 

A chalcophilic tendency for gold has been observed in a 

diabase-granophyre suite from Tasmania where the variation pattern of gold is closely parallel to that shown by 

copper. A gross correlation between gold and copper has 

also been noted in a few petrochemically distinct basaltic 

provinces. Basalts of alkalic affinities are characterized by 

significantly lower copper and gold content than most 

tholeiitic basalts; the relatively high concentration of gold 

in the Dillsburg suite is accompanied by a . high copper 

content. In unaltered diabase-granophyre suites, the variation trends for gold indicate that gold either reaches a 

maximum in the intermediate stage or remains uniform in 

abundance during magmatic differentiation. In the calcalkalic volcanic suites of rocks, gold content decreases on 

the average as rock composition grades from basalt and 

andesite to dacite and rhyolite. Basalts from the orogenic 

belt of the Western United States tend to have higher gold 

content than those of more stable regions of the continental 

interior or the primitive basalts of the Hawaiian Islands. 

Unaltered rhyolitic rocks of both the calc-alkalic and alkalic 

suites are generally uniform and low in gold content (0.1-

1.0 ppb) despite differences in geologic age, provenance, or 

petrochemical features. The subsilicic-alkalic series of comagmatic rocks (shonkinite-syenite association) from two 

laccoliths in central Montana have a higher gold content 

than other types of alkalic volcanic or plutonic provinces. 

The available data provide little support for the view that 

gold is concentrated in the residual liquids during magmatic 

differentiation in any of the calc-alkalic or alkalic provinces. 

The variation trends indicate that gold either remains relatively constant or decreases during differentiation processe;-s_. __ _ 

The gold content in suites of unaltered igneous rocks 

spatially associated with gold mineralization from selected 

areas-Boulder batholith region, Montana; Cornwall, Pa.; 

Jerome district, Arizona; Bullfrog district, Nevada; M.other 

Lode, California-is virtually the same as petrographically 

equivalent rocks from provinces devoid of mineralization. 

The relatively high concentration of gold that exceeds background levels for a given region inva~iably occurs .~nly 

l.Qcally ____ in altered rocks and may be asc:nbed to remobihzatj.Q.n_o:csecondary introduction. Geochemical abundance datD 

alone n~rovide unique criteria in identifying broad 

segments of the crust favorable for gold mi~eralization ~or 

specify processes that resulted in the economic concentration 

of gold. Thus, in any exploration program, geologic factors, 

· such as petrologic, structural, and tectonic setting, must be 

considered in conjunction with purely geochemical abundance factors. 

INTRODUCTION 

Because of analytical difficulties involved in the 

measurement of gold in parts per billion, quantitative data on the distribution of gold in igneous rocks 

from the United States (and elsewhere) are extremely limited. In connection with the U.S. Geo1 
2 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

logical Survey's study of heavy metals, we have 

investigated the occurrence and distribution of gold 

in igneous rocks and minerals representative of 

diverse magma types and tectonic associations. The 

sampled suites include: plutonic calc-alkalic rocks 

from the Mesozoic-lower Tertiary batholiths of the 

Western United States (the Southern California, 

Sierra Nevada, Idaho, and Boulder batholiths) ; calcalkalic volcanic rocks from Oregon, northern California, and New Mexico; alkalic basalt-trachyandesiteriebeckite rhyolite volcanic rocks from Texas; and 

tholeiitic, low-K20, and alkalic basalts from continental as well as oceanic environments. In addition 

to general chemical and mineralogic studies, nearly 

all these suites have been, or are currently being, 

analyzed for their content of lithophilic trace elements, such as thorium, uranium, niobium, and tantalum. For many of the samples, complete chemical 

analyses of the rock and selected minerals are also 

available. In all, some 700 samples were analyzed 

for gold by neutron-activation procedures, and the 

resultant data presented herein probably constitute 

the largest body of such data accumulated to date 

by any single laboratory. 

The objectives of this reconnaissance study are 

manifold: 

1. To understand better the geochemical behavior 

of gold in magmatic processes, 

2. To establish so-called background levels of gold 

in unaltered igneous rocks, that is, levels 

presumably reflecting primary abundances 

undisturbed by secondary concentration or 

remobilization, for the possible definition and 

appraisal of broad regions or rock units as 

potential sources of low-grade ores, 

3. To relate, if possible, geochemical gold provinces 

to major metallogenic provinces, 

4. To recognize, if possible, the association of gold 

with other elements in various geochemical 

environments, 

5. To test sampling and analytical procedures, inasmuch as in this study we are concerned with 

gold abundance in parts per billion, and 

6. To outline areas for more detailed topical studies 

that will bear quantitatively on the geochemical behavior of gold during magmatism. 

Obviously, it is beyond the scope of this report to 

treat extensively samples from any given locality or 

to explore fully the ramifications of generalizations 

suggested by the data; rather, our purpose is to 

construct the overall framework into which such 

in-depth specialized studies must fit. 

A comprehensive bibliography of the geology and 

geochemistry of gold has been compiled by Cooper 

(1971). 

ACKNOWLEDGMENTS 

We are greatly indebted to Robert L. Smith and 

Paul C. Bateman for guidance and encouragement 

in the work presented here. We thank our numerous 

colleagues in the Geological Survey and others 

acknowledged in the report for contributing samples 

and pertinent geologic information. Margaret Cooper 

and Michael Fleischer kindly called to our attention 

and provided some of the Russian literature on the 

geochemistry of gold. We are grateful to Michael 

Fleischer and L. P. Greenland for their review of 

an early version of this report and suggestions for 

its improvement. 

ANALYTICAL PROCEDURE 

Neutron-activation analysis is particularly well 

suited to the study of the generally low concentration level of gold in igneous rocks because the 

method is highly sensitive and eliminates possible 

reagent contamination. A rapid, sensitive method 

of neutron-activation analysis was developed by 

Rowe and Simon (1968) for studying distribution 

of gold in geologic materials, and it is particularly 

useful in studies (such as this one) involving hundreds of samples. This method uses fire assay ·for 

the radiochemical separation of gold after irradiation and is summarized below. 

Sixteen 1-gram samples and four standards are 

irradiated together for 10 hours in a flux of 5 X 1012 

neutrons per square centimeter per second. Samples 

are allowed to cool for 10 days to permit the decay 

of most of the activity, primarily that of Na24, which 

·has a 15-hour half-life. They are then processed 

through fire assay., with gold carrier added, and the 

final gold bead is weighed to determine the yield. 

The beads are then counted in a Nai (Tl) well-type 

crystal coupled to a multichannel analyzer. The 

0.413 Mev peak for Au198 is used in calculating the 

amount of gold present. Counting is repeated after 

two days to verify the decay of 2.7-day Au198• The 

method of Covell ( 1959) is used for calculating the 

area under the peak. If a value of about 400 counts 

per minute per nanogram of gold is foun~ 10 days 

after irradiation, then there is a suitable sensitivity 

for the levels of gold concentration commonly found 

in igneous rocks. 

Two sets of 16 samples plus four monitors can be 

irradiated at one time by using two tubes of the 

reactor for 10 hours. After the cooling period, 40 
ANALYTICAL PROCEDURE . 3 

samples can be processed through fire assay in 1 

day. The counting is performed overnight by using 

automatic sample changers and two crystals simultaneously. Thus, under normal circumstances; it is 

possible to analyze as many as 80 samples per week. 

PRECISION 

To estimate the precision of the analytical procedure, several igneous rocks which differ in composition (basalt to granite), texture (glassy to coarsegrained), and concentration levels (a few tenths of 

a part per billion to 4 ppb gold) were chosen for 

detailed study (tables 1 and 2). Replicate determinations of gold from a given bottle (m~terial ground 

to pass 100-mesh sieve) indicate that precision, 

expressed as relative deviation, of analyses of the 

basaltic specimens 1s about 10 percent (table 1, 

samples TLW-67-17, HW-6, and HK 1955); in general replicate analyses of coarser grained rocks 

having comparable concentration levels yield somewhat lower precision, around 15 percent (table 1, 

samples G-1, W-1, and G-78). 

TABLE 1.-Replicate determinations of gold, in parts per billion, 

in selected igneous rocks 

[Data in the first five sample columns are neutron-activation analyses from Rowe and Simon ( 1968, table 2) ; data in the last column are from this report] 

Mean ______________________ _ 

Standard deviation---------- Relative deviation (percent)_ 

TLW-67-17 

Cone Crater, 

Hawaii, 

basalt 

4.3 

4.5 

4.1 

5.0 

4.2 

4.4 

4.2 

4.2 

4.3 

.27 

6.3 

HW-6 

Kilauea, 

Hawaii, 

basaltic 

glass · 

1.6 

1.7 

1.7 

1.6 

1.6 

1.2 

1.4 

1.5 

1.5 

.16 10.7 

HK 1955 Kilauea, 

Hawaii, 

basalt 

1.0 

.8 

1.0 

.9 

1.0 

.9 

.8 

1.0 

·.9 

.08 

8.9 

G-P 

Granite 

3.7 

2.7 

2.9 

2.7 

2.4 

3.0 

2.9 

2.9 

2.9 

.37 12.8 

G-78 Silver Plume Granite, Front Range, Colo., W-!2 quartz Diabase monzonite 

4.9 0.6 5.6 .6 4.6 .4 3.9 .7 3.7 .6 4.0 .6 4.9 .7 5.4 

4.6 

.69 15.0 

.6 

.10 16.7 

1 U.S. Geol. Survey standard granite from Westerly, R.I. 2 U.S. Geol. Survey standard diabase from Centerville, Va. 

TABLE 2.-Reproducibility of gold determinations, in parts per billion, 

on splits and composites of selected igneous rocks 

Split A --------------------------

B -------------------------- C -------------------------- D -------------------------- E -------------------------- F -------------------------- G -------------------------- H -------------------------- Composite (A, B, C. D) ----------

Grand mean ---------------------- Standard deviation -----~--------­

Relative deviation (percent) ------

Rhyolite 

obsidian1 

2 3 4 

0.3 0.4 .2 .2 .5 .5 

1.0 .4 

.4 .4 .3 .4 

.4 .4 .4 .4 

.4 

.11 27.5 

Rhyolite 

pumice2 

1 2 3 

0.4 0.8 0.7 .4 .3 .2 .3 .5 

.4 .4 .4 

.5 .9 .6 .5 

.5 

.19 38.0 

Rhyolite 

obsidian3 

1 2 3 

0.6 0.5 0.5 .5 .5 .5 

.6 .6 .7 .6 .7 .6 .4 .5 .8 .8 

.6 

.05 

8.3 

Quartz monzonite4 

1 2 

0.3 0.3 .3 .3 

.3 .4 .3 .2 .3 .3 .5 .3 

.2 .2 

.3 .5 

.3 

.09 30.0 

1 Sample 68-LGM, Little Glass Mountain. Medicine Lake Highland, Calif. Splits A, B, C, and D repre- sent chips broken from various parts of a single hand specimen. 2 Samples 68-GM, Glass Mountain, Medicine Lake Highland, Calif. Samples A, B, C, and D represent 

four separate pumice fragments from bulk collection. . a U.S. Geol. Survey standard RGM-1, Glass Mountain, Calif. (prepared by F. J. Flanagan, U.S. Geol. 

Survey). 4 Sample 6K-306, Butte Quartz Monzonite, Boulder batholith, Montana. A single hand specimen was sawed into eight chunks, which when ground gave the following weights: A, 127 g; B, 90 g; C, 60 g; D, 75 g; E. 100 g; F. 113 g; G, 84 g; and H, 95 g. 

Tests on four selected rocks whose range of gold 

content (0.3-0.6 ppb) is low and narrow suggest 

that the reproducibility of gold determinations differs little, regardless of differences in composition, 

texture, and grain size (rhyolite obsidian to coarsegrained quartz monzonite; see table 2 and fig. 1) . 

Analysis of variance (single variable of classification) suggests that differences in mean gold content of splits of obsidian samples are statistically 

significant at the 95-percent confidence level, whereas splits of pumice and quartz monzonite samples 

apparently have equal means. However, the separate 

chunks of pumice and the sawed pieces of the coarsegrained Butte Quartz Monzonite seem, from the 

analysis of variance, to have more homogeneous distribution of gold than do the obsidian samples (table 

2 and fig. 1) ; this fact is contrary to our (intuitive) 

expectations and implies that many factors affecting 

overall precision have not been considered in our 

simple statistical test. 
4 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

Rhyolite obsidian (68- LGM) 

I \ 

/

1 

sp~~r:~en \ I \ I \ 

I I \ 

/ I \ I I \ I I \ 8 ~ 8 rtJ Chips 

~' 

0.6 

0.5 

0.5 

0.3 '\ 0.2 I I 0.5 / 1.0 

0.4 \ 0.2 I 1

1 0.5 I 0.4 

/ 

>-

() 

z 

w 

10 

'\ I / 

'\ I I / 

'\ 1 I 1

1 

', I I 1 

' I I I ',I I 1

1 

~Composite 0.4 0.4 

0.4 0.4 

0.3 0.4 

0.4 0.4 

::::> 5 0 

w 

a:: 

1..1... 

/ 

/ 

0.5 1.0 

Au, IN PARTS PER BILLION 

/ 

/ / 

Rhyolite obsidian (RGM-1) 

/ 

/ / / 

USGS 

standard 

(bulk) ' ' ' ' I '\ ' 

II \ ', 

I I I \\ ', 

I I I \ ' 1 I I ' ' 0 GJ rrJ 0 Q]splits 

>-

() 

z 

w 

::::> 

0 

w 

a:: 

1..1... 

0.5 

0.5 

0.5 

10 

5 

Au, IN 

0.6 

0.6 

0.7 

0.5 

0.6 

0.7 

0.6 

PARTS PER 

0.4 0.8 

0.5 0.8 

1.0 

BILLION 

/ / / 

8 

0.3 

0.3 

Rhyolite pumice (68-GM) 

8 [I} 0 0 Spe~~~~!e 0.4 \ 0.4 1 1 0.3 1 0 _4 fragments 

0.8 \ 0.3 I ~ 0.5 I 0.4 

0. 7 \ 0.2 II I • / 0.4 

/ 

\ I I I 

\ I I I 

\ I I I \ I I 1 \ I I 1 

\ I I 1 \ I I 1 \ I I 1 \ I I 1 \ I I I 

\ \ II I 

\ I I I 

\ I I / \\I I \ II I 

\\1/ 

Composite~ 0.5 

>-

() 

z 

w 

10 

::::> 5 0 

w 

a:: 

1..1... 

0.9 

0.6 

0.5 

0 o 0.5 1.0 

Au, IN PARTS PER BILLION 

Quartz monzonite (6K-306) 

// 1', 

/ / 

Hand ' / ' ' / 

/ // specimen ' ' / / ' / / ' ' ' ' ' ' / / I \ ' ' / / / I \ ' ' ' / / I \ / ' ' / / I I \ \ ' ' / I I I ' / I I ' ' I \ / ' ' / ' ' I I I \ ' ' 0 0 0 GJ 8 m 8 Chunks 

0.3 0.3 0.3 0.3 0.5 0.2 0.3 

0.3 0.4 0.2 0.3 0.3 0.2 0.5 

10 

>-

() 

z 

w 

::::> 5 0 

w 

a:: 

1..1... 

1.0 

Au, IN PARTS PER BILLION 

FIGURE 1.-Schematic representation of tests of reproducibility of gold determinations of three rhyolites and one quartz 

monzonite. Data from table 2. 
" 

ANALYTICAL PROCEDURE 5 

The principal factors that must be considered in 

evaluating the overall precision of the analytical 

result are: 

1. Homogeneity of the sample, as it affects the 

sampling vagaries inherent in analyzing one 

or more 1 gram samples prepared from a 

much larger mass of rock. The problem of 

obtaining a representative sample which will 

contain an adequately representative amount 

of gold (in whatever form), or any other element of interest, has been treated by Wilson 

(1964) and Clifton, Hunter, Swanson, and 

Phillips ( 1969). However, in view of the lack 

of quantitative data regarding gold-particle 

size or specific mode of occurrence of gold in 

igneous rocks, it is not possible at this time 

to evaluate quantitatively the effect of variations in sample homogeneity on the observed 

overall precision. 1 · 

2. Analytical factors include errors in weighing, 

flux variation in the reactor (which may vary 

as much as 5 percent from the mean, when 

four monitors are used), and counting statistics (which may also vary as much as 5 

percent, depending on count rates). Other 

analytical factors that may contribute to the 

problem are variations of a mechanical or 

physical nature, such as failure to achieve 

adequate or uniform mixing during fusion of 

sample, failure of active and inactive carrier 

to exchange isotopes completely, mechanical 

losses during fusion, and variations in position 

of samples during counting when automatic 

sample changers are operating. 

Because of the large number of samples involved 

in this reconnaissance investigation, there obviously 

was not enough time to analyze each sample in replicate in an attempt to relate the relative contribution 

of sample homogeneity versus analytical error to the 

overall precision levels. However, we can place some 

conservative empirically derived limits on the "effective" or "working" precision of the data presented 

herein. Detailed studies on selected samples (tables 

1 and 2) show that, when concentration levels are 

less than 1 ppb gold, the standard deviation can be 

less than 0.1 ppb and differences of 0.2 ppb or 

greater between samples may be geochemically significant; for such small concentrations a low counting 

rate may have a significant effect. We have chosen 

intervals of 0.25 ppb in the presentation of our data 

1 For· example, the quartz monzonite ( 6K-306) in table 2 has a mean 

gold content of 0.3 ppb, but another sample from the same outcrop collected several years earlier contains 0.8 ppb gold (table 21). 

443-785 0 - 72 - 2 

in histogram form (fig. 1) , even though we realize 

that in the generally nonreplicate routine, processing 

of the many hundreds of samples, differing in homog.eneity, a more realistic .standard deviation for any 

Single determination is much greater than 0.1 ppb 

and differences as great as 0.5 ppb may not be 

geochemically or statistically significant. 

At levels of gold concentration greater than 1 ppb 

and for coarse-grained rocks which are likely to be 

more heterogeneous in gold distribution, we feel that 

differences of 20-25 percent probably represent geochemically significant variations. For reasonably 

homogeneous samples (for example, glassy or aph~ 

anitic rocks) which have been carefully processed 

a precision of 10 percent can be expected, and value~ that differ from one another by more than 10 percent of the value can, we suggest, be considered as 

representing actual differences in gold content. 

ACCURACY 

The accuracy of an analytical method is more 

difficult to evaluate. It is generally evaluated by 

cross-comparison with results obtained independently by other investigators using different ana-

. lytical techniques. Because few methods, other 

o-than radioactivation, are suitable for gold determinations at low concentrati9ns, we can only com-. 

pare our data with other data mainly obtained by 

neutron-activation procedures. Rowe and Simon 

(1968, table 3) have shown the good agreement 

between data obtained on U.S. Geological Survey 

standard rocks by the method we used in this 

study and those obtained by other investigators. 

CONTAMINATION EFFECTS 

At low levels of gold concentration, the effects 

of contamination during sample preparation and 

handling can be significant. To study the magnitude 

of contamination effects, an experiment was performed. Z. S. Altschuler, U.S. Geological Survey, 

using careful splitting techniques, prepared four 

splits of a powdered sample of tonalite from the 

San Jacinto Mountains, Calif. From previous analysis it. was known that this sample contained about 

2 ppb gold. Two of the four splits were fingered, 

after first rubbing the fingers on a gold watch. The 

other two splits were analyzed directly without 

handling. The two "gold-fingered" splits gave 

results of 537 and 608 ppb as compared with 

1.0-1.9 ppb for the unhandled samples. This indicates the need for extreme care in handling samples 

when analyzing for trace elements in parts per 

billion. 
6 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

A major advantage of activation analysis is that 

it minimizes possible reagent and other contamination; contamination can only take place ·during 

sample collection, preparation, and weighing. After 

a sample has been sealed in its irradiation vial, it 

is free from nearly all ·possible contamination, aside 

from a sample mixup. 

GOLD CONTENT IN PLUTONIC ROCKS 

The spatial and (or) temporal association of gold 

mineralization and plutons has been noted in many 

parts of the United States and the world. (See, for 

example, Emmons, 1937; Koschmann and Bergendahl, 1968.) However, only relatively recently have 

there been attempts (for example, Voskresenskaya 

and Zvereva, 1968; Shcherbakov and Perezhogin, 

1964; Shcherbakov, 1968; Shilin, 1968; Mantei and 

Brownlow, 1967; Mantei and others, 1970) to obtain 

precise measurements of gold in plutonic rocks 

known or supposed to be unaffected by postcrystallization alteration or metamorphism. In this study, 

we have analyzed about 160 samples representative 

of the dominant rocks of the major (MesozoicTertiary) batholiths of the Western United States, 

as well as of other smaller plutonic masses. These 

batholiths underlie vast areas (approximately~ 

100,000 square miles) and are fairly typical of 

igneous rocks exposed in the earth's crust. Thus, 

the data obtained on these batholithic rocks are 

important for establishing the crustal abundance of 

gold. 

The geologic settings of the batholiths and plutons 

we have sampled are, in general, well known and 

have been described copiously in the literature; 

table 3 summarizes some key references to literature 

pertinent to the samples analyzed. We shall make 

no attempt to discuss each of the plutonic provinces 

in detail, principally because gold content in all but 

a very few plutonic rocks varies only slightly from 

province to province. For convenience, our data on 

plutonic rocks are discussed in terms of two broad 

categories, calc-alkalic and alkalic. 2 

CALC-ALKALIC PROVINCES 

Calc-alk~lic plutonic rocks, such as those making 

up the major batholiths of the Western United 

States, vary little in gold content; the overwhelming 

majority of samples have 3 ppb or less of gold 

(tables 4, 18-23 ; figs. 2 and 3) . From our data, 

the only noteworthy exception to this generalization 

is represented by the Southern California· batholith, 

2 These terms are used in this paper in a general petrologic sense, not 

in the specific nominal sense of Peacock ( 1931). 

TABLE 3.-Selected literature pertinent to the plutonic 

samples analyzed 

Suite or location References 

Southern California batholith_ Larsen (1948). 

Larsen and Gottfried ( 1961) . 

Taylor and Epstein 

Sierra Nevada batholith, 

California. 

(1962a,b). 

Bateman, Clark, Huber, 

Moore, and Rinehart 

(1963). . 

Bateman and Eaton (1967). 

Dodge, Smith, and Mays 

(1969). 

Coast and Transverse Ranges, Page ( 1966) . 

Calif. 

Idaho batholith, Idaho _______ _ 

Boulder batholith, Montana __ _ 

Dodge and Ross ( 1971) . 

Larsen and Schmidt (1958). 

McDowell and Kulp ( 1969). 

Tilling, Klepper and 

Obradovich (1968). 

Doe, Tilling, Hedge, and 

Klepper ( 1968). 

.Knopf (1957). 

Tatoosh pluton, Washington __ Fiske, Hopson, and Waters 

(1963). 

Rocky Mountains, Colo ______ _ Wright (1964). 

Lovering and Goddard 

(1950). 

White Mountains Plutonic 

Series, New Hampshire 

(formerly named the White 

Mountains Plutonic-Volcanic 

Series). 

Chapman and Williams 

(1935). 

Billings (1928). 

TABLE 4.-Summary of distribution of gold in various plutonic 

provinces 

Suite or location 

Southern California batholith. 

Sierra Nevada batholith, California. 

Coast and Transverse Ranges, Calif. 

Idaho batholith -------

Boulder batholith, Montana. 

Tatoosh pluton, 

Washington. 

Rocky Mountains, Colo. 

White Mountain Plutonic Series, New Hampshire. 

North Carolina -------

[Data from tables 18-25] 

Number of Range Rock type samples (ppb) 

Calc-alkalic provinces 

Gabbro ------------ 6 Tonalite ----------- 9 Granodiorite 12 Quartz monzonite to 3 aplite. 

Quartz diorite ------ 1 Granodiorite 11 Quartz monzonite to 5 alaskite. 

Quartz diorite ------ 1 

Granodiorite ------- 3 Quartz monzonite ___ 1 

Diorite and quartz 7 diorite. 

Granodiorite ------- 16 Quartz monzonite ___ 6 

Granite to aplite____ 6 

Syenogabbro ------- 1 Granodiorite ------- 3 Quartz monzonite to 2 5 to alaskite. 

Granodiorite ------- 15 

Quartz diorite to 4 granite. 

Alkalic provinces 

Gabbro to monzodio- 2 rite. 

Syenite ------------ 4 Granite ------------ 21 

Gabbro ------------ 1 Syenite ------------ l Albite quartz monzo- 12 nite to granite. 

0.7-11.6 

.5-11.8 

.2- 1.2 1.8- 1.9 

.4- 5.2 .3- 1.8 

.2- .7 

.2- 6.0 

.1- 5.2 .4- 2.7 .2- .8 

1.0- 8.4 .5- .8 

.3- 4.2 

.4- .6 

0.8- 0.8 

.8- .4 .2- 1.6 

.2- 2.3 

1 The altered granite (5.6 ppb) is excluded. 

Average 

gold 

content 

(ppb) 

4.4 

8.7 

.4 

.9 

1.4 

1.5 

.8 

.5 

.5 

2.1 

2.2 

1.7 

1.1 

.5 

.6 

2.1 

.6 

1.3 

.5 

0.8 

.3 

.6 

.7 

.z 

.9 

2 One of the quartz monzonite samples is represented by the average value for 19 samples from a 4,000-foot borehole (table 14). 
' 

GOLD CONTENT IN PLUTONIC ROCKS 7 

8 

6 

Southern California batholith 

4 

2 

0 2 3 4 5 6 7 8 9 10 11 12 

6 EXPLANATION 

4 Sierra Nevada batholith 

~ Gabbro 

2 

·~ 

o~~~~~-~r~~~~~r~::~~ Diorite and tonalite 

0 2 3 4 5 6 [ill] 

[:) 6 

z 

LiJ 5 4 LiJ 

0:: 

LL. 

6 

4 

2 

6 

4 

2 

0 

0 

0 

Idaho batholith 

2 3 4 5 

Average and range of 19 samples from drill hole 

2 3 4 5 

2 3 4 5 

Granodiorite 

D 

Quartz monzonite to granite 

6 8 9 10 11 12 

Boulder batholith 

6 7 8 9 io 11 12 

Tatoosh pluton 

6 7 8 9 10 11 12 

GOLD, IN PARTS PER BILLION 

FIGURE 2.-Histograms of gold content of some plutonic rocks of the Western United States. 

Data from tables 18-22. 

some gabbroic phases of which, relative to other 

plutonic rocks studied, can have a comparatively 

high gold content, as great as almost 12 ppb (fig. 2; 

table 4). 

Taken individually, plutonic suites (such as the 

Southern California, Idaho, Sierra Nevada and, 

perhaps, the Boulder batholiths) commonly exhibit 

a gross systematic variation of gold content with 

rock type (table 4) . This tendency for the more 

mafic members in a given plutonic series to be 

higher in gold than the felsic members supports 

our earlier suggestion (Gottfried and others, 1969), 

based on fewer data, that gold apparently is not 

concentrated in residual liquids during magmatic 

differentiation. Table 5 shows the average gold content of some plutonic rocks, calculated according to 

rock type regardless of provenance; our data rather 

convincingly reinforce the pattern of increasing gold 
8 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

25 EXPLANATION 

20 D 

Quartz monzonite to granite 

15 

Composite alkalic rocks lii1I1 

Syenite 

10 

~ 5 Gabbro to monzonite 

0 

0 2 3 4 5 6 7 8 9 10 11 12 

>-

(.) 

z 

UJ 

::> 

0' 

UJ EXPLANATION 0::: 

1.1.. 30 D 

Quartz monzonite to granite 

25 [ill] .20 Composite calc-alkalic rocks Granodiorite 

15 ~ Diorite and tonalite 

10 ~ Gabbro 

5 

0 

0 2 3 4 5 6 7 8 9 10 11 12 

GOLD, IN PARTS PER BILLION 

FIGURE 3.-Composite histograms of gold content of calc-alkalic and alkalic plutonic rocks; provenance not considered. 

Data from tables 18-25. 

content with increasing content of mafic minerals, 

as suggested by data for individual suites. On the 

whole, our data are in good accord with the summaries of Phan (1965, table 1.4.1) and Jones (1969, 

table 5) ; their summaries are based on values in 

the literature, principally Russian (for example, 

Shcherbakov and Perezhogin, 1963, 1964). ·The 

question of the mode of occurrence of gold in some 

calc-alkalic plutonic rocks studied is taken up later. 

TABLE 5.-Distribution of gold in calc-alkalic and alkalic 

plutonic rocks geneTalized according to rock type regardless 

of province 

[Summarized from data of tables 18-25] 

Number 

of 

samples 

Gabbro ------------------------------ 7 Diorite and tonalite ------------------- 19 

Granodiorite ------------------------- 60 

Quartz monzonite to granite ----------- 1 29 

Alkalic plutonic rocks 

Gabbro to monzodiorite ---------------

Syenite ------------------------------ Quartz monzonite to granite -----------

3 

5 

33 

Range 

(ppb) 

0.6-11.6 

.2-11.3 

.1- 5.2 1.1- 2.7 

0.3- 0.7 .2- .4 .2- 2.3 

3.9 

2.7 

1.2 

.8 

0.4 

.3 

.7 

1 The value for altered granite (5.6 ppb) from the Southern California 

batholith is excluded. 

ALKALIC PROVINCES 

Our sampling of alkalic plutonic rocks is limited 

to some rocks from New Hampshire, North Carolina, and South Carolina (table 24 and 25) . Nonetheless, the data suggest that gold content for the 

alkalic rocks studied occurs within a lower and 

even narrower range than for the calc-alkalic rocks 

studied and rarely exceeds 1.5 ppb (table 5 and 

fig. 3). This apparent relationship is also observed 

for volcanic rocks ( p. 19). Our data for alkalic 

plutonic rocks are insufficient to establish any statistically significant figures on the systematic variation of gold content with rock type, as could be 

demonstrated for the calc-alkalic rocks. 

HAW AllAN ISLANDS 

Gold content was determined in 33 samples of volcanic rocks representing some of the major petrographic provinces of the Hawaiian Islands (table 6 

and fig. 4). Petrochemical characteristics and geologic setting of these suites are well known. (See, 
GOLD CONTENT IN BASALTIC ASSOCIATIONS 

TABLE 6.-Summary of gold content in basaltic associations 

[Data from tables 26-33] 

Suite or location 

Hawaii: 

Kilauea --------------------------

Mauna Loa ---------------------- Haleakala ------------------------

Honolulu Volcanic Series ---------- Koolau Volcanic Series ----------- Ridge and rise systems: 

Mid-Atlantic Ridge ---------------

East Pacific Rise -----------------

Rock type 

Oceanic provinces 

Number of 

samples 

Prehistoric tholeiite ------------ 2 

Historic summit tholeiite ------- 5 

1955 flank lavas ---------------- 8 

Tholeiite ---------------------- 10 

Alkalic basalt ---------------- 1 

Andesite ---------------------- 5 

Nepheline melilite basalt ------- 1 

Tholeiite ---------------------- 1 

Low-K20 tholeiite ------------- 3 ____ do_________________________ 39 

Alkalic basalt ----------------- 10 

Continental basaltic provinces 

Plateau basalts, Oregon and Washington: 

Columbia River Group: 

Picture Gorge Basalt --------- Yakima Basalt --------------- Pliocene-Quaternary basalt ------- Basalts of the Snake River Group and 

associated rhyolitic rocks, Idaho. 

Greenstone Flow, Michigan -----------

Tholeiite ---------------------- 5 ____ do_________________________ 6 

Olivine basalt ----------------- 4 ____ do_________________________ 19 

Rhyolite ----------------------- 6 Basalt ------------------------- 7 Pegmatite --------------------- 2 

Granophyre ------------------- 1 

Hypabyssal (diabase) provinces 

Triassic basin, Eastern United States: 

Connecticut ---------------------- New Jersey ---------------------- Pennsylvania --------------------

Dillsburg --------------------

Cornwall ---------------------

Virginia -------------------------

North Carolina ------------------

South Carolina ------------------- Precambrian diabase, 

southeastern Missouri: 

Shepherd Mountain --------------

160-foot sill ----------------------

Great Lake intrusion, Tasmania -------

Basalt-diabase ----------------- 16 

Basalt ------------------------ 23 

Diabase dikes ------------------ 9 

Diabase sheet: 

Diabase ;..------------------ 2 

Pegmatitic facies ---------- 1 

Granophyre --------------- 3 

Diabase sheet: 

Chilled margin (altered?) __ 1 

Normal diabase ------------ 5 Altered diabase ___________ :_ 1 

Pegmatitic diabase --------- 2 

Granophyre --------------- 2 

Diabase dike, chilled margin_____ 1 

Diabase ----------------------- 7 Granophyric diabase ----------- 5 

Granophyre ------------------- 4 

Low K20 diabase dikes --------- 6 Diabase dike ------------------- 1 ----dO------------------------ 4 

Diabase-gabbro ---------------- 12 

Altered diabase ---------------- 1 

Diabase ----------------------- 7 Altered diabase ---------------- 5 

Chilled margin (altered) ------- 1 

Lower zone -------------------- 7 Central zone ------------------- 9 

Granophyre ------------------- 2 

1 One sample was omitted that contained 14.4 ppb gold. 2 One sample was omitted that contained 23.1 ppb gold. 

Range 

(ppb) 

4.3- 4.6 

1.8- 2.7 

.5- 5.2 

1.7- 6.6 

.5- 3.9 

.5- 1.6 

.1- 4.6 

.2- 1.8 

0.5- 3.2 

.8-11.0 

.4- 1.8 

.1- 1.3 

.2- 1.2 1 1.4- 7.0 

3.5- 7.6 

1.0- 4.3 2 2.7- 9.6 

1.7- 7.2 

8.5-22.6 

9.0-19.6 

1.8- 2.8 

2.0- 5.5 

.7- 2.0 

.3- 3.7 

2.2- 6.5 

1.1- 3.8 

2.7- 7.9 

2.2- 3.2 

1.2- 5.7 

.7- 7.4 

.5- 3.2 

2.4- 5.2 

1.2-12.0 

1.0- 1.4 

Average 

gold 

content 

(ppb) 

4.5 

2.2 

1.7 

2.5 

.2 

1.5 

1.4 

1.4 

.9 

.6 

.8 

2.3 

4.8 

.9 

.5 

.6 1 3.7 

5.5 

8.5 

2.6 2 4.7 

3.3 

15.5 

12.2 

14.1 

8.1 

2.1 

.4 

3.7 

1.3 

1.6 

2.3 

3.2 

2.0 

4.8 

3.8 

2.5 

2.2 

.5 

2.9 

1.6 

7.3 

3.6 

6.5 

1.2 

9 

for example, Powers, 1955; Macdonald, 1949; Macdonald and Powers, 1946; Macdonald and Eaton, 

1964; Tilley and Scoon, 1961.) Most of our an;;tlyses 

are on glassy silica-saturated basalts of Kilauea and 

Mauna Loa which are believed to be fairly representative of magmas that formed the lavas of the 

primitive shield of each of these volcanoes. 

a value of 2.6 ppb on a single sample. The moderately fractionated 1955 lavas of the east rift zone 

and those of the alkalic Haleakala suite appear to 

have a gold content slightly lower than those of 

typical Hawaiian tholeiites (table 26). 

Samples of the tholeiite that erupted from the 

summits of Kilauea and Mauna Loa (table 26) are 

quite uniform in gold content and average 2.2 and 

2.5 ppb, respectively. The values for Mauna Loa 

basalts agree reasonably well with those obtained 

by Ehmann, Baedecker, and McKown (1970), who 

reported an average of 4.2 ppb for three samples, 

and by Vincent and Crocket ( 1960b), who obtained 

MID-ATLANTIC RIDGE AND EAST PACIFIC RISE 

The worldwide ridge-and-rise system is one of 

the prominent features of the ocean floor. Basalt, 

commonly referred to as oceanic tholeiite, is by far 

the predominant rock type of this feature. Oceanic 

tholeiitic basalts are readily distinguished from 

most continental basalts by their lower potassium 

content ( < 0.3 percent), unusually low abundances 

of large ions, such as thorium, uranium, niobium, 
10 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

8 

6 

4 

2 

0 

0 2 3 

18 

>- 16 

(.) ..... z ~ .... I.J..J 

:::> 14 0 

I.J..J 

a:: 

Li.. 12 

10 

6 

0 2 3 

Hawaiian Islands 

4 5 6 

Ridge and rise systems 

4 5 6 

EXPLANATION 

• [{2 m 

Honolulu-Koolau Kilauea-Mauna Loa 1955 flank, 

Volcanic Series summits Kilauea and Haleakala 

7 8 9 

EXPLANATION 

r::::::l 

L:::.J 

Low- K20 tholeiite 

~ Alkalic basalt 

8 9 

10 11 

10 11 

12 

12 

GOLD, IN PARTS PER BILLION 

FIGURE 4.-Histograms of gold content of rocks in some basaltic associations from oceanic provinces. 

Data from tables 26 and 27. 

rubidium, barium, and cesium, and high potassiumrubidium and potassium-cesium ratios (Engel and 

others, 1965; Tatsumoto and others, 1965; Gast, 

1965; Gottfried and others, 1968). Alkalic basalts, 

which make up less than 1 percent of oceanic. volcanic rocks, occur on the flanks of the oceanic 

ridges, on the tops of submarine volcanoes, and on 

the islands located on the ridge-and-rise system. 

Among the 52 samples (table 27) we analyzed are 

some previously . studied by Engel, Engel, and 

Havens (1965) from widely separated regions as 

well as a larger number of samples (35) from a 

restricted segment (Juan de Fuca ridg~Blanco 

fracture zone) of the East Pacific Rise. Gold content of tholeiitic rocks is rather uniform and averages slightly less than 1 ppb; contrary to expectation, the alkalic basalts, which average 0.8 ppb 

(table 6), have virtually the same gold content as 

tholeiites. 

Previously published values for gold in oceanic 

tholeiites are few and contradictory. DeGrazia and 

Haskin (1964) reported 6.3-14 ppb gold for three 

samples from the Mid-Atlantic Ridge, whereas 

Ehmann, Baedecker, and McKown ( 1970) obtained 

only 0.2-0.3 ppb for the same three samples. and 0.4 

ppb for a sample from the East Pacific Rise. Our 

more extensive data, though still far from adequate 

considering the vast areas underlain by oceanic 

ridges, suggest that oceanic tholeiites are characterized by lower gold content than typical tholeiitic 

basalts from Hawaii or continental regions. 

CONTINENTAL PROVINCES 

PLATEAU BASALTS AND ASSOCIATED ROCKS, 

OREGON AND WASHINGTON 

W~ters · (1961) ·subdivided the basalts of the 

Columbia River Group (Miocene and Pliocene) 

into two types (there do not seem to be any transitional varieties) : ( 1) Picture Gorge type-older, 

silica content 47-50 percent, approximately 5 percent olivine and (2) Yakima type-younger, silica 

content 53-54 percent, higher K20 and Ti02, little 

or no olivine. However, gold content observed for 

these rocks (table 28) does not reflect their differences in chemistry and mineralogy. Because of the 

limited. number of samples analyzed and the wide 

variation in range of gold values, the differences in 

average gold content between the Picture Gorge 
< 

GOLD CONTENT IN. BASALTIC ASSOCIATIONS 11 

6 

4 

2 

0 

0 2 

10 

8 

>-

u 

z 6 w 

::::l 

0' 

w 

0::: 

1.1.. 

0 

0 2 

Plateau basalt and other rocks, 

Oregon and Washington 

3 4 5 

Snake River Group, Idaho 

3 4 5 

6 

6 

EXPLANATION 

E3 

Clarno and John Day Formations 

~ Basalt of the Columbia River Group 

§ 

Pliocene-Quaternary olivine basalt 

7 8 9 10 11 12 

EXPLANATION 

~ Rhyolite 

[ill . 

Basalt 

7 ·8 9 10 11 12 

:J 

Greenstone Flow, Michigan 

~~~f0~~s:~~~~;t~~~·~~;~q~~~~~~P~~~~~~~P~~~~~~~~~~;~~~~~\v~~q~~ 

0 2 3 4 5 6 7 8 9 14 15 

GOLD, IN PARTS PER BILLION 

FIGURE 5.-Histograms of gold content of rocks from some continental basaltic provinces of the United States. 

Data from tables 28-30. · 

( 2.3 ppb) and Yakima ( 4.8 ppb) types may not be 

statistically significant. 

The Pliocene-Quaternary basalts differ from the 

Columbia River basalts in having more plagioclase 

and olivine and a diktytaxitic texture. Our limited 

data suggest that gold content in these rocks is 

lower than that in most Columbia River basalts and 

comparable to that in the andesites and in the more 

silicic rocks of the Clarno and John Day.Formations 

(tables 6 and 28; fig. 5). 

BASALTS OF THE SNAKE RIVER GROUP AND 

ASSOCIATED RHYOLITIC ROCKS, IDAHO 

Powers (1960a) has shown that the Snake River 

basalts of southern Idaho are lower in Si02 and 

richer in FeO, Ti02, and P 205 than basalts of the 

Columbia Plateau or Cascade Range. The occurrence 

of strongly alkaline mafic lavas· (Powers, 1960b) 

and alkalic rhyolites and tuffs indicates that Snake 

River basalts have alkalic affinities. An unusual 

chemical feature of these rocks is the decrease of 

the iron-magnesium ratio with an increase in silica, 

a trend opposite to that for tholeiitic suites. Intermediate rocks such as andesites and dacites are 

extremely rare in the Snake River Plain, regarded 

by Hamilton (1965) as a province of bimodal volcanism of olivine basalt and rhyolite. 

Of the 19 basalts analyzed, only two exceed 1 ppb 

in gold (table 29) ; the rhyolites and basalts have 

about the same range and mean in gold content 

(table 6 and fig. 5). 

GREENSTONE FLOW, .MICHIGAN 

Because the Greenstone Flow is the thickest and 

most differentiated of the Keweenawan flows in the 

Michigan copper district, it has been studied in 

considerable detail by Broderick ( 1935) and by 

Cornwall (1951a, b, c). The flow is composed of 

ophitic olivine basalt that contains pegmatitic layers 

and small granophyre dikes in its upper half. Because of the close spatial relationship of the basaltic 

flows and copper deposits, the abundance and distribution of copper in the Greenstone and other 

·flows have been well documented by much geologic 
12 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

and analytical data (Broderick, 1935; Broderick 

and Hohl, 1935; Sandell and Goldich, 1943; Cornwall and Rose, 1957). These data suggest that, during magmatic differentiation, copper was concentrated in the pegmatitic facies of the Greenstone 

Flow. 

Gold abundance of the same specimens (table 

30) used by Cornwall and Rose (1957) in their 

spectrographic study shows no close systematic variation with stratigraphic position or copper content 

but nonetheless fits the gross positive correlation 

with copper, a chalcophilic element (see fig. 10). 

Despite some variability probably in part ascribable 

to varying degrees of alteration (noted by Cornwall, 1951a), gold content of the Greenstone· Flow 

averages 3. 7 ppb, which is similar to the mean gold 

abundance of most other basaltic provinces (table 6) . 

HYPABYSSAL (DIABASE) PROVINCES 

In certain continental areas, rocks of basaltic 

composition occur predominantly as gently dipping 

or fiat, intrusive diabase sheets, though they are 

also commonly associated with subordinate basaltic 

flows, plugs,· and dikes. We have arbitrarily treated 

these basaltic or diabase sheets as another manifestation of basaltic volcanism, mainly because the 

undifferentiated (chilled) magma of these sheets is 

tholeiitic. Some sheets, especially those which have 

associated granophyres, are of particular geochemical and petrologic interest in that they provide unequivocal examples of differentiation in place of a 

given increment of basaltic magma. 

TRIASSIC BASIN, EASTERN UNITED- STATES 

Basaltic rocks of Late Triassic age near the eastern margin of the United States and Canada occur 

as flows, small dikes, and thick intrusive sheets in 

down-faulted basins from Nova Scotia to South 

Carolina; these rocks underlie approximately 6,000 

square miles. Early petrologic studies on samples 

from the northern part of the province (New J ersey and Pennsylvania) show that the undifferentiated magma (chilled margin) is of the tholeiitic 

magma type and fairly typical of continental tholeiitic provinces the world over (Walker, 1940; 

Hotz, 1953). However, recent petrochemical investigations (Ragland and others, 1968) of chilled 

margins of dikes in North Carolina indicate that, 

with few exceptions, these rocks more closely resemble oceanic tholeiites. Thus, at least two chemically different basaltic magmas may be represented 

by the Triassic mafic rocks. · 

Although the basalt-diabase samples we analyzed 

range fairly widely in texture and composition, the 

concentrated level and mean gold content ( 1.3 ...... 4. 7 

ppb) for the various suites show relatively little 

variation, if the Dillsburg suite and the altered diabase from Cornwall are excluded (table 6 and :fig; 

6). For example, dike rocks from the North Carolina Piedmont (except for sample JY -1) are low 

in Si02 ( 47-49 percent) and K20 (nearly equal to 

0.2 percent), are high in Ab03 (-- 16.9 percent), 

and average 4.8 ppb gold; sample JY-1, though 

higher in Si02 (52 percent) and K20 (0.5 percent), 

is not significantly different in its gold content 

(3.8 ppb). Chemical data are not available for dike 

samples from South Carolina, which average 2.5 

ppb gold. Within the Carolinas province, then, the 

mean gold content varies only within a factor of 

two, despite much greater differences in chemistry 

of the magmas. In contrast, and perhaps significantly, gold content i'n low-K20 diabase dikes of 

North Carolina is about five times that in nearly 

chemically identical tholeiitic basalts of the oceanic 

ridge system. 

Relative to the other basalt-diabase suites analyzed, the Dillsburg suite (Pennsylvania) is considerably higher in gold content, which ranges from 

8.5 to 22.6 ppb and shows no apparent variation 

with bulk chemistry or stratigraphic position. It 

should be mentioned, however, that these samples 

are restricted to about the upper third of the sheet 

which is believed to be at least 1,000 feet thick; 

thus, in using the present data, we do not know if 

the entire sheet is characterized by a high gold 

content. Nevertheless, the average gold content in 

12 samples (table 31) from the Cornwall district, 

Pennsylvania, located only approximately 30 miles 

to the east of Dillsburg in a similar geologic setting, 

is significantly lower (0.4-8.1 ppb). The maximum 

gold content of 8.1 ppb for the Cornwall samples is 

observed for a sample of the chilled margin, which 

contains very small sulfide veinlets ; the presence of 

veinlets suggests that this one high value may reflect 

later introduction, rather than the original amount 

in the magma. In brief, the gold content in the Cornwall samples is significantly lower than those in 

petrographically equivalent rocks from the Dillsburg intrusion but is comparable to "background 

levels" typified by basalts· ~nd smaller dikes elsewhere in the Triassic hypabyssal basalt-diabase 

province. 

For comparison with the differentiated diabase 

· sheets at Cornwall and Dillsburg, Pa., gold analyses 

were made on 16 samples representative of the 
GOLD CONTENT IN BASALTIC ASSOCIATIONS 13 

10 EXPLANATION 

8 

6 

Triassic basin, 

Eastern United States 

0 

Connecticut, New Jersey, North Carolina 

South Carolina, Virginia, and Cornwall, Pennsylvania 

4 m 

Dillsburg, Pennsylvania 

2 

o-r~~~F=~~=r~T=~r=~~~==~~~L4===r~4=~~~~~=L~~~~~~~--~--~1 --4~~~1 

>-

u 

z 

L.LJ 6 :::> 

0' 

L.LJ 

E 4 

2 

6 

0 2 

0 2 

3 4 5 6 8 9 12 13 14 

Southeastern Missouri 

3 4 5 6 

Great Lake intrusion, Tasmania 

4 

0 2 3 4 5 6 8 9 10 11 12 

GOLD, IN PARTS PER BILLION 

FIGURE 6.-Histograms of gold content of rocks from some hypabyssal (diabase) provinces of the United States and Tasmania. The diagrams for the Triassic basin, United States, does not show a sample from New Jersey, which has 23.1 

ppb gold, and two samples from Dillsburg, Pa., which have 19.6 and 22.6 ppb gold. Data from tables 31-33. 

diabase-granophyre intrusions in Fairfax County, 

Va. Here, mineralization is lacking, and, hence, 

conditions are probably more favorable for establishing the primary gold content of diabasic rocks. 

Although widely ranging in mineralogic composition, the various phases of the diabase-granophyre 

association are strikingly uniform in gold content, 

and the means range only between 2.0 and 3.2 ppb 

(table 6) ; chemical data are not available for these 

rocks. Such· uniformity suggests that differentiation 

processes have affected gold content in these samples only minimally and such that the values observed may well be close to those of the parent 

magma. Vincent and Crocket (1960a) also noted 

the general constancy of gold content in rocks of 

the strongly fractionated Skaergaard intrusion in 

east Greenland. 

The close similarity in gold content between the 

Virginia samples and fresh samples from the dikes 

and differentiated diabase sheet at Cornwall, Pa., 

provide indirect evidence that the anomalously high 

gold content observed for the Dillsburg intrusion 

443-785 0 - 72 - 3 

reflect postcrystallization alteration rather than primary features. Moreover, inasmuch as both the 

Cornwall and the Dillsb.urg intrusions are associated with mineralization, both these areas will be 

discussed in some detail in connection with the possible effects of alteration on primary gold distribution ( p. 27) . 

PRECAMBRIAN DIABASE, SOUTHEASTERN MISSOURI 

Borehole samples from two small differentiated 

mafic bodies in southeastern Missouri (table 32) 

have· a gold content typical of other continental 

basalt-diabase samples; unaltered specimens have a 

mean gold content of 2.2-2.9 ppb (table 6). The 

geologic setting and petrologic studies of the specimens we analyzed have been described by Desborough (1963, 1967) ; the least differentiated rock of 

these bodies is an olivine diabase and is presumed 

to represent the parent magma. In both the Shepherd Mountain intrusion and the 160-foot sill, the 

altered rocks seem to have a lower gold content than 

the fresh (table 32), a tendency suggesting the pos-
14 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

A B 180 180 

170 .. 170 

160 I EXPLANATION 160 z .. .. z 150 0 .. 150 0 

:::::i :::::i Copper from Greenland and __J 

140 ::::! 140 ·~ 

130 ~ Lovering (1966) 130 a:: a:: • LiJ 

120 ~ 120 0.. 

110 (f) 

Gold from Rowe (1969) (f) 

110 t- t- a:: 100 ~ 100 <( 

.. 190 0.. 0.. 

~ 90 ~ 

A 80 .& 80 ci ci \ 70 LiJ LiJ 70 0.. 0.. 0.. 13 /· 60 0.. '. 0 0 60 (.) 

12 50 (.) 12 50 z .. "-• .. ___.. 0 11 40 z 11 

--.. / 40 :::::i 0 __J 10 :::::i 10 iii __J 

9 iii 9 a:: 

LiJ a:: 8 0.. LiJ 

(f) 0.. 

t- (f) 

a:: 6 t- <( a:: 6 • 

~/ 0.. 5 

-~. <( 

0.. 5 

~ 4 ~ 4 ci • ci __J 3 0 __J 

" 0 2 ·-· " 0 0 40 50 60 70 80 90 100 100 400 700 1000 1300 1600 

MAFIC INDEX, FeO+Fe203 xlOO DEPTH, IN FEET 

FeO+ Fe203+ MgO 

FIGURE 7.-Variation in gold and copper abundance with mafic index (A) and depth (B) of samples from the Great Lake 

sheet, Tasmania. Data from Greenland and Lovering (1966) and Rowe (1969). 

sibility that some gold may have been removed during alteration; in view of the limited number of 

altered samples (six), this suggestion obviously 

needs to be tested by much additional data. Despite 

the fivefold increase in the amount of sulfides with 

differentiation (Desborough, 1967), our abundance 

data on gold show no such corresponding variation 

with total sulfides. From the findings of Vincent 

and Crocket (1960a) that gabbros rich in copper 

sulfides have a relatively high content of gold, we 

anticipated closer correlation between gold and sulfide abundance. 

GREAT LAKE INTRUSION, TASMANIA 

On the basis of comparative detailed petrologic, 

chemical, and mineralogic studies, McDougall 

(1964) considered the Great Lake intrusion to be 

an excellent representative of the Tasmanian tholeiitic province, which is Jurassic in age and underlies an area of some 6,000 square miles. In addition 

to McDougall's comprehensive work, abundant subsequent isotopic and trace-element investigations 

have been carried out on this intrusion; these studies make it perhaps one of the most extensively 

documented diabase-granophyre bodies (Heier and 

others, 1965; Greenland and Lovering, 1966; Gottfried and others, 1968). 

Analyses for gold (Rowe, 1969) and copper 

(Greenland and Lovering, 1966) of 19 borehole 

specimens from the Great Lake sheet, in contrast 

to previously discussed differentiated diabasic intrusions, demonstrate a remarkably close correlation 

between gold and copper over the entire range of 

crystallization (table 33; fig. 7). The maximum gold 

content ( 12 ppb) is in the lower part of the central 

zone, and the minimum gold content ( 1.2 ppb) is in 

the granophyre. The gold content of the lower 

chilled margin is higher ( 7.3 ppb) than the average. 

for the intrusion and is probably due to hydrothermal introduction. Significantly, McDougall and 

Lovering (1963) and McDougall (1962) reported 

the c~ystallization of chalcopyrite during the middle stage of crystallization ·(central zone), which 

resulted in a strong depletion of copper in the later 

differentiates (granophyres). This· close parallelism 

of gold and copper variation patterns may in large 

part reflect the abundance and composition of 

copper-rich sulfides, for example, chalcopyrite. Pre-
GOLD CONTENT IN BASALT-ANDESITE-RHYOLITE ASSOCIATIONS 15 

liminary experimental data of P. B. Barton (in 

U.S. Geological Survey, 1969, p. A108) indicate 

that at 650°C chalcopyrite can accommodate more 

than 1.6 weight percent of gold, whereas amounts 

soluble in pyrite, pyrrhotite, and arsenopyrite are 

considerably less than 0.1 weight percent. However, 

Barton stressed that much of the gold is exsolved 

upon cooling. 

The Great Lake sheet may be somewhat unusual 

(but ideal for study) in that virtually all variation 

trends of trace elements plot very smooth curves, 

including the trend for cesium, a highly mobile 

constituent that responds readily to the s!ightest 

postcrystallization disturbance (Gottfried and others, 1968). Moreover, the potassium-cesium ratio 

and content of volatiles (fluorine and chlorine) also 

vary systematically with differentiation (Greenland 

and Lovering, 1966). Collectively, these studies provide convincing evidence that any alteration in the 

Great Lake intrusion is local, that the degree of 

alteration is small, and that the observed variation 

patterns at major and minor elements record responses to changes in the primary crystallization 

regime. Thus, it is probably not at all fortuitous 

that the least disturbed diabase-granophyre system 

should demonstrate such a well-defined copper-gold 

relationship after undergoing magmatic differentiation. 

GOLD CONTENT IN 

BASALT -ANDESITE-RHYOLITE ASSOCIATIONS 

CALC-ALKALIC PROVINCES 

CASCADE RANGE AND ADJACENT AREAS, OREGON AND 

CALIFORNIA 

Volcanic rocks in the Cascade Range, which extends from southern British Columbia to northern 

California, are generally grouped into two major 

sequences : ( 1) a sequence (Miocene or older) 

which underlies the Western Cascade Range and 

consists of folded and locally altered flows and 

pyroclastic material and (2) a younger sequence 

(Pliocene to Holocene) which underlies the High 

Cascades arid consists chiefly of undeformed, fresh 

basaltic and andesitic flows. 

Samples from the Western Cascades (Oregon) 

studied by Peck, Griggs, Schlicker, Wells, and Dole 

(1964) have an average gold content ranging from 

0.9 to 7.2 ppb; there is a strong tendency for the 

basalts and andesites to be higher in gold than the 

dacites and rhyodacites (table 34). As representatives of the High Cascades and vicinity ( California), 26 samples from the Mount Shasta, Lassen, 

and Medicine Lake regions have been analyzed 

(table 35). Chemical, mineralogic, and strontiumisotope data on most of these samples have been 

reported recently (Smith and Carmichael, 1968; 

Peterman and others, 1970). In general, the range 

in gold abundance and the mean gold content observed for samples from the Mount Shasta and 

Lassen regions are greater than the range and mean 

for samples from the Medicine Lake Highland region (table 7 and fig. 8) . 

Basalts analyzed from the Medicine Lake Highland range in age from the Pliocene Warner Basalt 

of Russell ( 1928) to the very recently erupted 

Modoc and Ha,t Creek Basalts of Powers (1932) 

and Anderson (1940, 1941). The Warner Basalt, 

which is also readily distinguishable from the Modoc 

Basalt by its significantly lower potassium content, 

averages slightly higher in gold than the Modoc 

Basalt, 3.5 ppb as compared with 1.2 ppb; both 

these basalts, however, have more gold than rhyolites ( 0.5 ppb) from the same region (table 7). 

Though not from the Cascade volcanic province 

proper, rhyolitic rocks from Mono County, Calif., 

are also low in gold; excluding the sample containing 1.9 ppb gold, the remaining seven samples have 

0.5 ppb or less gold (table 36). 

Quartz basalts of the Lassen region have been 

considered as hybrid products resulting from the 

contamination of basaltic magma by felsic xenoliths 

and xenocrysts of dacitic origin (Finch and Anderson, 1930). The gold content of these rocks tends 

to be relatively high, an average of 11.9 ppb (table 

7). Because our data indicate that gold content in 

felsic volcanic rocks is lower than in mafic volcanic 

rocks in the Cascade province, the initial gold concentration in the host basaltic magma prior to contamination must have been even higher. 

JEMEZ MOUNTAINS, N.MEX. 

The Jemez Mountains of north-central New Mexico are composed of a complex volcanic pile that 

underlies an area of about 1,500 square miles and 

consists chiefly of lower to upper Pliocene basaltic, 

andesitic, dacitic, and rhyolitic rocks. The youngest 

volcanic rocks in the region are Pleistocene rhyolitic ash flows, which preceded caldera collapse, and 

postcaldera rhyolitic pyroclastics, flows, and domes 

(Ross and others, 1961; Smith and Bailey, 1968; 

Smith and others, 1970). Analysis of 46 samples 

. shows the basalts to have distinctly higher gold 

content (averaging 2.5 ppb) than rhyolitic rocks, 

which, with very few exceptions, contain only a few 

tenths part per billion (table 37). 

Samples of air-fall pumice and associated ashflow tuffs representing the Bandelier Tuff provide 
16 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE 7.-Summary of gold content in basalt-andesite-rhyolite associations 

[Data from tables 34-44] 

Suite or location 

Western Cascades, Oreg.: Little Butte Volcanic Series ______ _ 

Sardine Formation --------------- Southern High Cascades, Calif., and vicinity: 

Mount Shasta --------------------

Lassen area ----------------------

Medicine Lake Highland ----------

Mono County, Calif_ __________________ _ 

Jemez Mountains, N. Mex.: 

Precaldera volcanics -------------

Bandelier Tuff: 

Tshirege Member ------------

Otowi Member --------------- Postcaldera silicic volcanics ------- Jerome, central Ariz.: 

Yavapai Series: 

Ash Creek Group ------------- Alder Group -----------------

Quartz porphyry ------------- Beatty area, Nevada: 

Bullfrog Hills caldera sequence ----

Yucca Mountains caldera sequence __ 

Yellowstone National Park, Wyo., and vicinity. Challis Volcanics, central Idaho ______ _ 

Southern Appalachians Denton quadrangle, North Carolina. Mount Rogers Formation, Va _________ _ 

Big Bend National Park, Tex _________ _ 

Bearpaw and Highwood Mountains, central Mont.: 

Boxelder laccolith ----------------

Shonkin Sag laccolith ____ _: _______ _ 

Rock type 

Calc-alkalic provinces 

Number of samples 

Olivine basalt ------------------ 5 Andesite ---------------------- 2 

Dacite ------------------------ 3 

Rhyodacite -------------------- 4 

Andesite ---------------------- 7 

Olivine basalt ------------------ 1 Andesite ---------------------- 4 Olivine basalt ------------------ 1 

Quartz basalt ------------------ 4 

Andesite ---------------------- 1 

Warner Basalt ----------------- 7 Olivine basalt ------------------ 3 

Andesite ---------------------- 1 

Rhyolite ----------------------- 4 Rhyolite ----------------------- 8 

Basalt ------------------------- 12 Quartz latite to rhyolite -------- 4 

Rhyolite ----------------------- 8 

Rhyolite ----------------------- 8 

Quartz latite to rhyolite -------- 14 

Altered rhyolite ---------------- 6 Less altered rhyolite ----------- 7 Altered rhyolite ---------------- 2 ____ do_________________________ 5 

Less altered rhyolite ----------- 5 Altered rhyolite ---------------- 3 

Latite ------------------------- 1 Basalt ------------------------- 1 Altered rhyolite ---------------- 6 Rhyodacite -------------------- 1 Recent basalt ------------------ 1 Rhyolite ----------------------- 15 Basalt ------------------------ 3 Andesite ---------------------- 3 Dacite ------------------------ 1 Latite ------------------------- 2 Rhyolite ----------------------- 5 Andesite ---------------------- 3 Rhyolite ---------------------- 4 Rhyolite ------------------------ 9 

Alkalic provinces 

Alkali basalt-syenogabbro ------ 10 Trachyandesite-syenodiorite ---- 4 

Syenite-trachyte --------------- 6 Rhyolite-granite --------------- 7 

Shonkinite -------------------- 5 Syenite ------------------------ 4 Aplitic dike ---,---------------- 1 Pegmatitic patch -------------- 1 

Mafic phonolite ---------------- 2 Shonkinite -------------------- 4 Transition rock --------------- 3 Syenite ------------------------ 3 Minette ----------------------- 1 Aplitic syenite ----------------- 1 

Range 

(ppb) 

2.8- 5.3 3.8-10.7 

.6- 1.1 .8- 1.4 .6·-11.0 

4.3-12.0 

1.5-19.4 

1.9- 6.2 .6- 2.2 

.4- .5 .1- 1.9 

1.3- 6.1 .1- .3 

.5- 1.6 .4- .7 .2- .7 

.4-12.4 

.. 2- .9 3.4- 8.3 .5- 7.4 

.2- .9 2.0-22.0 

.3- 3.9 

.1- 1.5 .2- .2 .3- 1.0 

.9- 1.0 .3- 1.7 .5- 1.9 

.4- .9 .1- 2.8 

0.3- 4.3 .4- 1.0 .2- 1.9 .2- 1.2 

2.4- 6.1 .4- 2.9 

1.6-10.4 

.5- 6.7 .7- 2.3 2.8- 5.1 

Average 

gold 

content 

(ppb) 

4.2 

7.2 

.9 

1.0 

3.3 

11.6 

8.0 

4.6 

11.9 

7.0 

3.5 

1.2 

4.7 

.5 

.4 

2.5 

.2 

.9 

.6 

.4 

5.4 

.3 

5.8 

2.9 

.4 16.6 .5 

1.8 

1.9 

.8 

1.7 

.5 

.2 

.6 

.5 

1.0 

.8 

1.1 

.6 

.5 

o:9 

.6 

.7 

.5 

4.0 

1.8 

1.4 

1.4 

6.0 

4.1 

1.2 

3.7 

2.0 

3.8 

excellent material for tracing the behavior of gold 

during the course of differentiation of rhyolitic 

magma. This unit has been divided by Bailey, Smith, 

and Ross (1969) into two members, the Otowi and 

Tshirege, which have been dated as 1.4 m.y. (million years) and 1.0 m.y., respectively (Doell and 

others, 1968). Available data on mineralogy and on 

major and minor elements for successive flows of 

each member exhibit systematic variation trends 

which reflect corresponding physicochemical changes 

in their respective magma chambe-rs (Smith and 

Bailey, 1966). The striking uniformity of gold content within each member of the Bandelier Tuff suggests that, within the limits of analytical uncertainty, processes which produced wide variations in 

the lithophilic trace elements do not affect gold distribution. For the same samples, data on niobium, 

tantalum, thorium, uranium, rubidium, and cesium 

content (Smith and Bailey, 1966 ; Gottfried and 

others, unpub. data) shows a threefold to fourfold 

decrease from the first (most silicic) to the last 

(most mafic) erupted material, whereas gold content remains virtually constant (table 7 and fig. 8) ; 

similarly, the, postcaldera rhyolites are uniformly 
GOLD CONTENT IN BASALT-ANDESITE-RHYOLITE ASSOCIATIONS 17 

low in gold content and exhibit no correlation with 

eruptive sequence or petrochemical features (table 

37). 

YELLOWSTONE NATIONAL PARK, WYO., AND VICINITY 

Rhyolites of Pliocene and Quaternary age of the 

Yellowstone plateau underlie some 2,000 square 

miles in Yellowstone National Park (Boyd, 1961) 

and extend into adjacent parts of Montana and 

Idaho. They tend to occur as voluminous ash-flow 

sheets associated with calderas and lava flows 

(R. L. Christiansen and H. R. Blank, Jr., in U.S. 

Geological Survey, 1969, p. A37). Hamilton (1959, 

1963) noted that these rhyolites, in terms of major 

element chemistry, are restricted to a very narrow 

range and, in general, are distinctly more alkalic 

than those of the orogenic basalt-andesite-rhyolite 

associations. 

Gold content of randomly collected rhyolites 

(tuffs and flows) from the Yell ow stone plateau is 

characteristically low; it ranges from 0.1 ppb to 

1.3 ppb and averages 0.5 ppb (table 38). The three 

samples of basalt, whose abundance is greatly subordinate to rhyolite in the region, have a relatively 

low gold content ( 0.2 ppb, table 38) and, in this 

respect, are similar to those of the Snake River 

Plain (table 6), even though the Snake River 

basalts are more alkalic (Hamilton, 1965) . 

PRECAMBRIAN METAVOLCANIC ROCKS, CENTRAL 

ARIZONA 

Dacites, rhyolites, and quartz porphyries composing about one-third of the Yavapai Series (Precambrian) have been metamorphosed to the greenschist 

facies and then subsequently hydrothermally altered 

(Anderson, 1968). Analysis of 20 samples of these 

rocks, for which chemical, petrographic, and geologic data have been given by Anderson ( 1968), 

indicate gold content of rhyolites in the Ash Creek 

Group tends to be more variable ( 0.4-12.4 ppb) and 

higher (averaging 5.4 ppb) than in most rhyolites 

of the Alder Group (table· 7). On the whole, the 

Alder rocks are less altered than the Ash Creek rocks 

and, with the exception of two strongly altered samples (nos. 18 and 19, table 39), have a gold content 

( 0.2-0.9 ppb) typical of unaltered rhyolites from 

other provinces of the Western United States (table 

7 and fig. 8). Similarly, the quartz porphyry tends 

to be more altered and have a relatively higher gold 

abundance (0.5-7.4 ppb) than samples of the Alder 

Group. 

Differences in gold content of the samples analyzed can be related to chemical variations of major 

elements arising from alteration effects. This aspect 

is treated in more detail in connection with primary 

gold abundance and its bearing on gold mineraliz3;-

tion (p. 28). 

BEATTY AREA, NEVADA 

Rhyolitic ash flows, tuffs, and lavas near Beatty, 

Nye County, Nev., are divided into two sequences: 

an ·older suite of probable Miocene age and a 

younger suite of probable Pliocene age (Cornwall, 

1962). Ash flows of the older and younger suites 

are compositionally similar and believed to have 

been derived from two calderas, the Bullfrog Hills 

and Yucca Mountains calderas, respectively; volumetrically smaller flows of latite, rhyodacite, and 

basalt are associated with both calderas. Very few,. 

if any, of the rhyolitic rocks are entirely unaltered, 

and some are locally intensely altered. Data on major and minor elements and geologic setting of the 

samples we analyzed for gold are given by Cornwall 

(1962) and Cornwall and Kleinhampl (1964). 

The largest concentration of gold (2.0-22 ppb) is 

in highly altered samples of the Bullfrog Hills caldera; the values of the less altered rhyolites are 

lower in gold and range from 0.2 to 0.9 ppb (table 

40). However, altered rhyolites of the Yucca Mountains caldera suite are only slightly enriched in gold 

(0.3-3.9 ppb), as compared with values typically 

observed for fresh rhyolite, that is, less than 1 ppb 

(table 7). Two samples of basalt from the Beatty 

area, which have somewhat alkalic tendencies, contain 1. 7 and 1.8 ppb gold. 

CHALLIS VOLCANICS, CENTRAL IDAHO 

Recent studies by B. F. Leonard (in U.S. Geological Survey, 1968, p. A27) suggest that, even 

within a small area (Thunder Mountain caldera), 

the age of the Challis Volcanics can vary from 

Eocene to latest Oligocene or earliest Miocene, the 

same time span (Eocene? to Miocene?) generally 

accepted for the Challis on a regional scale. Limited. 

sampling and· analysis (table 41) indicate that rhyolite, dacite, latite, and andesite of the Challis Volcanics have a relatively low gold content ( 0.3-1. 7 

ppb) that is typical of unaltered felsic and intermediate volcanic rocks of the Western United States 

(table 7 and fig. 8). 

SOUTHERN APPALACHIANS, VIRGINIA AND 

NORTH CAROLINA 

Lower Paleozoic calc-alkalic volcanic rocks, which 

range in composition from basalt to rhyolite and 

underlie a large part of the Carolina slate belt, have 
18 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

been metamorphosed to the lower greenschist facies 

(Butler and Ragland, 1969; Stromquist and Sundelius, 1969). Gold deposits in various parts of the 

southern Piedmont are spatially associated with felsic volcanic rocks (Pardee and Park, 1948), and 

recent studies by Bell ( 1969) indicate that the 

mineralization is related to early Paleozoic volcanism. Gold content of some samples from the area 

mapped by Stromquist (1966) in North Carolina is 

less than 1 ppb except for one sample of andesite 

(table 42). These volcanic rocks have a gold con6 

tent mu.ch like that of plutonic rocks from the same 

general region (table 25) . 

Rhyolitic rocks of the Mount Rogers Formation 

are part of the Blue Ridge belt of the southern 

Appalachians. Uranium-lead isotopic ages on zircons from a few of these rhyolites indicate they are 

of late Precambrian age (Rankin and others, 1969). 

Gold abundance of petrographically diverse rhyolites from the Mount Rogers Formation, the geologic setting of which was given by Rankin ( 1970), 

is 0.5 ppb or less, except for one sample (table 42). 

EXPLANATION 

4 Western Cascades, Oregon 

2 

Q Dacite and rhyodacite} Oligocene 

and II Basalt and andesite Miocene 

• A d .t (Middle and n es1 e upper Miocene) 

4 

2 

0 

>-. 

(.) 

4 

~ 2 ::> 

0' 

0 

0 

2 3 4 5 6 8 9 10 11 12 

EXPLANATION 

Southern High Cascades and vicinity, California 

Mount Shasta Lassen region Medicine • Lake 

Highland 

2 3 4 5 6 7 8 9 10 11 12 

Rhyolite, Mono County, California 

~ o~~~~----~~--~--~--.---.--.---.--~--.---.---.--.---.---.--.---.---.--.---.---.--. u.. 0 2 3 4 5 6 8 9 10 11 12 

16 

14 EXPLANATION 

12 Jemez Mountains, New Mexico ~ Rhyolite 

10 lillJ 

Basalt 

8 

6 

4 

0 2 3 4 5 6 7 8 9 11 12 

GOLD, IN PARTS PER BILLION 

FIGURE B.-Histograms of gold content of rocks from some calc-alkalic and basalt-andesite-rhyolite associations. The 

histogram for the southern High Cascades, Calif., does not show two samples from the Lassen region which have 

14.1 and 19.4 ppb gold. Data from tables 34-42. 
GOLD CONTENT IN BASALT-ANDESITE-RHYOLITE ASSOCIATIONS 19 

The gold content (table 42) in these Paleozoic and 

Precambrian felsic volcanic rocks from the southern Appalachians supports our previous generalization (Gottfried and others, 1969), based on fewer 

data, that the gold content of unaltered rhyolitic 

rocks, regardless of differences in composition, age, 

or provenance, is characterized by a very narrow 

and low range. 

ALKALIC PROVINCES 

BIG BEND NATIONAL PARK, TEX. 

Igneous rocks from the Big Bend National Park 

area, which range from alkalic basalt to extremely 

CaO-poor riebeckite rhyolite and granite, represent 

8 

6 

4 

2 

0 

0 

6 

4 

2 

>- 0 

u 0 z 

w 

::> 

0' 

w 

0:: 

u.. 2 

0 

0 

:~ 0 

4 

2 

0 

0 

2 

2 

2 

rm I 

2 

3 

3 

3 

I 

3 

3 

Yellowstone National Park 

4 5 

Jerome, Arizona 

4 5 

Beatty area, Nevada 

4 

I 

4 

4 

5 

I 

5 

5 

one of several alkalic subprovinces extending from 

Montana to Texas along the front of the Rocky 

Mountains. The Big Bend suite consists of highly 

alkaline extrusive and hypabyssal rocks, and sodium 

is slightly dominant relative to potassium. The 

petrology and geologic setting of these rocks have 

been given in abstracts by Lonsdale and Maxwell 

(1949) and Maxwell and Lonsdale (1949); partial 

chemical data on the rocks we analyzed for gold 

have been published elsewhere (Gottfried and others, 1962). 

Despite the wide diversity of petrographic types, 

the ranges and averages of gold content are very 

nearly the same (table 43 and fig. 9) for all rocks 

6 

6 

6 

I 

6 

6 

EXPLANATION 

[] . Basalt 

~ Rhyolite 

8 9 10 

EXPLANATION 

~ Alder Group Ash Creek • Group 

tJ 7 8 10 

EXPLANATION 

7 

I 

7 

7' 

8 9 

Challis Volcanics, Idaho 

I 

8 

I 

9 

Southern Appalachians 

8 9 

~ I 

11 

10 

I 

10 

10 

11 

D 

Quartz porphyry 

'V 

I ~ 12 

~ 22 

I 

11 

11 

12 

I 

13 

I 

23 

I 

12 

12 

GOLD, IN PARTS PER BILLION 

FIGURE B.-Continued 
20 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

10 

EXPLANATION 

8 

Big Bend National Park, Texas 1m 6 Alkali basalt-syenogabbro 

[] 4 Trachyandesite-syenodiorite 

to rhyolite-granite 

2 

>- u 0 

z 2 3 4 5 6 w 7 8 9 10 11 12 

:::::> 

0 

w 

0::: 

u. 10 

EXPLANATION 

8 Bearpaw and Highwood Mountains, Montana D 6 Shonkin Sag laccolith 

~ 4 Boxelder laccolith 

2 

0 

0 3 4 5 6 7 8 9 10 11 12 

GOLD, IN PARTS PER BILLION 

FIGURE 9.-Histograms of gold content of rocks from some alkalic provinces. Data from tables 43 and 44. 

in the park. Except for three out of 27 samples, the 

rocks contain 1 ppb or less gold and hence are similar in gold abundance to corresponding rock types 

of the moderately alkalic White Mountain Plutonic 

Series (table 24) . 

BOXELDER AND SHONKIN SAG LACCOLITHS, MONTANA 

The differentiated Boxelder and Shonkin Sag 

laccoliths in the Bearpaw and Highwood Mountains, respectively, contain nearly the entire range 

of rock types found in the subsilicic-alkalic subprovince of central Montana described by Larsen 

(1940). The Boxelder laccolith (Pecora, 1941) is 

larger and grossly similar to the Shonkin Sag laccolith (Hurlbut, 1939), except that in the Boxelder 

the shonkinite and syenite contain plagioclase. Most 

of the rocks in both these bodies represent in place 

differentiation of shonkinitic magma to yield syenitic rocks. Chemically, these rocks are unusually 

high in K2 0 ( 4-9 percent) for rocks low in Si02 

(45-50 percent) and rich in CaO (2-11 percent). 

Analyses for gold (table 44 and fig. 9) show that 

nearly all the shonkinitic rocks of both laccoliths 

are distinctly higher in gold than are the alkalic 

basalts from other petrographic provinces (compare tables 44 and 7). In the Boxelder laccolith, 

gold content decreases systematically from an average of 3.5 ppb for the shonkinitic rocks to 1.4 ppb 

for the late aplitic and pegmatitic phases (table 44), 

an indication of progressive depletion of gold in the 

magma as differentiation proceeded. In contrast, 

gold variation in the Shonkin Sag laccolith is more 

irregular. The basal mafic phonolite, which should 

represent the initial gold content of the magma, has 

a higher gold content (10.4 ppb) than any rock in 

the laccolith. Replicate analyses on this sample rule 

out the possibility that this anomalously high value 

stems from analytical error. Another mafic phonolite is unusually low in gold (1.6 ppb). Hurlbut 

(1939) noted the presence of carbonate and zeolites in these mafic phonolites as well as in some 

other rocks of the laccolith, and it is possible that 

these rather extreme variations in gold content may 

to some extent reflect postcrystallization alteration 

processes. 

SUMMARY DISCUSSION OF GOLD IN 

VOLCANIC ASSOCIATIONS 

From the preceding discussions of gold in volcanic series from region to region (tables 26-44 and 

figs. 4-9), several. important generalizations emerge 

and are summarized briefly below : 

1. Excluding all samples known, or suspected, to 

have undergone postmagmatic alteration, 

grand averages, calculated from group aver-
·~ 

SUMMARY DISCUSSION OF GOLD IN VOLCANIC ASSOCIATIONS 21 

ages for some 400 samples from diverse regions show the general tendency for mafic volcanic rocks to be higher in gold than felsic 

varieties (table 8) . This tendency is also noted 

for the plutonic rocks we analyzed (see table 

5). Our summary of mean gold abundances 

for volcanic rocks is in general accord with 

summaries of previous workers (for example, Phan, 1965; Shcherbakov and Perezhogin, 

1964), there being one notable exception. The 

summary by Jones (1969, table 5), based on 

scanty data, gives the average gold content 

for rhyolite as 12 ppb, which is. larger than 

our value of 0. 7 ppb by almost a factor of 20. 

We believe that the apparent relationship 

noted by Jones (1969)-gold content is inversely proportional to rock basicity in volcanic rocks but directly proportional in plutonic rocks-is not supported by the vastly 

increased volume of data now available and 

probably is a result of "selective sampling," 

as he had suggested. 

TABLE 8.-A verage gold content in selected rocks representative of different volcanic associations 

Rock type 

Basalt: 

[Based on data from tables 6 and 7] 

Average 

gold 

Number of content samples (ppb) 

Hawaiian tholeiite ----------------------------- 26 2.3 Oceanic tholeiite ___ :.,___________________________ 42 .6 

Continental tholeiite --------------------------- 149 3.3 

Circumpacific basalt ---------------------------- 21 6.4 

Alkalic basalt ---------------------------------- 31 .6 Andesite: 

Calc-alkalic associations ------------------------ 21 4.6 

Alkalic associations ---------------------------- 5 1.6 

Dacite to rhyodacite -------------------------------- 9 .8 

Quartz latite to rhyolite ---------------------------- 77 .7 Trachyandesite to trachyte ------------------------- 10 .6 Shonkinite-phonolite to syenite --------------------- 21 3.2 

2. For those undifferentiated samples generally believed to represent parent magmas, the data 

indicate a strikingly limited range of gold 

content, even though a nearly complete spectrum of basaltic magma types in diverse geologic settings is represented. When the samples that show evidence of alteration are omit-

. ted, this range is from about 0.5 to 5.0 ppb 

gold, that is, a factor of only 10. However, 

within this range, differences in gold content 

on ~ provincial or regional scale are discernible and can sometimes be related to bulk 

chemical composition and perhaps tectonic 

setting. While gold content tends to decrease 

in abundance from tholeiitic to alkalic basalts 

in the Hawaiian province, it is significantly 

lower in the low-K20 tholeiitic basalts of the 

ridge-and-rise system than in the chemically 

equivalent (except for Ti02) diabase dikes in 

the Triassic basin in the Piedmont of North 

Carolina. The recent study of MacGregor 

( 1969) suggested that the geographic distinction between oceanic island basalts and circumoceanic basalts more likely reflects "tectonic setting" than "regional geochemical 

variations." That the oceanic tholeiites and 

alkalic basalts, which represent the opposite 

extremes in terms of abunda.nce of lithophilic 

major and trace elements, have virtually the 

same gold content also clearly indicates that 

chemical data on major elements alone provide no universal guides in predicting gold 

content. 

3. In differentiated diabase-granophyre sheets from 

regions devoid of mineralization and alteration, gold either is distributed uniformly over 

the range of rock types analyzed. (for example, 

the suite from Virginia, table 31) or increases 

to a maximum in rocks representing the intermediate stages of differentiation (for example, 

the Great Lake sheet, Tasmania, table 33). 

The first pattern is similar to that for the 

Skaergaard intrusion in east Greenland (Vincent and Crocket, 1960a) ; the second, to that 

for the Anakita intrusion in the Siberian platform (Shcherbakov and Perezhogin, 1964). 

Thus, in none of the differentiated suites studied to date is there any evidence that gold 

becomes highly concentrated in the final products of magmatic crystallization. 

4. Gold shows chalcophilic tendencies. Data for a 

single suite from the Great Lake intrusion unequivocably demonstrate . this tendency ( p. 

14), which is also expressed by the gross 

positive correlation between gold and copper· 

content .in extrusive and hypabyssal rocks of 

several petrochemically distinct suites taken 

collectively (fig. 10). The greater. scatter of 

gold and copper content observed for the Dillsburg intrusion and the Greenstone Flow is 

due to alteration effects (p. 11, 12). Moreover, the general tendency for gold abundance 

to decrease from tholeiite to alkalic basalt in 

the Hawaiian province is matched by a decrease in copper content (data of Herliska in 

Macdonald, 1969) in corresponding rocks in 

the Hawaiian province.· Finally, in the Apollo 

11 lunar basalts, the surprisingly low gold 

content, averaging 0.04 ppb, is accompanied 

by low copper content, averaging 7.5 ppm 

(Keays and others, 1970). 
22 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

z 

0 

::::i 

_J 

iii 

a:: 

UJ 

a.. 

en 

1-

a:: 

<( 

a.. 

~ 10 

ci 

_J 

0 

<.!) 

5 

+ 

+ 

EXPLANATION 

+ Dillsburg, 

Pennsylvania 

• Greenstone Flow, 

Michigan 

• Oceanic tholeiites 

o Alkalic basalts, 

East Pacific Rise 

COPPER, IN PARTS PER MILLION 

FIGURE 10.-Variation of gold abundance with copper abundance in samples from four basaltic suites. Data from 

tables 27, 30, and 31. 

5. The highest gold content generally occurs in the. 

basaltic and andesitic members of the calcalkalic associations of the circum pacific (orogenic) belt; this association occurs along the 

margin of the Western United States as well 

as in the continental interior (Rocky Mountain province) . The mafic rocks of the orogenic 

belts tend to be somewhat higher in gold content than those of the more stable cratonic 

regions or the primitive basalts of the Hawaiian Islands (table 7). Rhyolitl.c rocks of 

calc-alkalic series as well as those of alkalic 

affinities are uniformly low in gold, rega:rdless 

of geologic setting. Our data, however, do not 

preclude the possible existence of regional or 

provincial variations in gold content in the 

rhyolite& because the overall uncertainty of 

the analytical determinations ( p. 3) may 

mask statistically significant differences in 

the concentration range of 0.1-1.0 ppb. 

6. In alkalic provinces all rock types, regardless of 

composition, are low in gold. An example of 

such rocks, characterized by a low-CaO and 

relatively high sodium content, is the suite 

from the Big Bend. area "(table 43 and p. 19). 

However, the subsilicic-alkalic rocks from central Montana (table 44), characterized by unusually high potassium but also high CaO 

content, have a distinctly higher gold content 

than low-CaO alkalic rocks. Moreover, the 

progressive decrease in gold content from 

mafic shonkinite to late syenitic differentiates in samples from the Boxelder laccolith, 

Bea:rpaw Mountains, Mont., suggests that gold 

decreases with magmatic differentiation a fact 

observed for many of the plutonic suites we 

studied (p. 6). 

MODE OF OCCURRENCE OF GOLD IN 

IGNEOUS ROCKS 

Gold-abundance data on igneous rocks suggest at 

least the gross correlation that the more mafic the 

rock, the more likely it is to have a relatively higher 

gold content. This, of course, implies some sort of 

mineralogic (hence, chemical) control and raises 

the question: How is gold distributed in a rock or, 

for that matter, in its constituent minerals? Unfortunately, only few quantitative data can be marshaled to ·attempt to answer this question and others 

related to the mode of occurrence of gold in unaltered igneous rocks (at the parts-per-billion level). 

Reliable determinations of gold l.n minerals common 

in igneous rocks are few indeed and have been summarized by Phan ( 1965) and more recently by Jones 

and Fleischer ( 1969). Most of the published values 

of gold in minerals relate to samples outside the 

United States; only the data of Mantei and Brownlow (1967) and, to a much lesser extent, of Vincent 

and Crocket (1960b) pertain to samples within the 

United States. 

To interpret our rock data better and in hopes of 

gaining some insight into the distribution of gold 

in rocks, we selected several rocks representative of 

several batholiths for detailed study. The principal 

minerals from these rocks were separated by a combination of heavy-liquid and magnetic techniques 

and analyzed for gold. All mineral separates examined optically and (or) by X-ray are estimated to 

be 98 percent or better in purity. 

ABUNDANCE LEVEL IN MINERALS 

Gold content of the minerals we analyzed (tables 

9-13) appears to be lower than published values by 

Phan ( 1965) and Jones ( 1969) for comparable 

mineral groups. The apparent levels are even more 

striking if we compare our results with those of 

Mantei and· Brownlow (1967), who studied samples from the Marysville stocks ; this igneous body 

is a satellitic pluton of the Boulder batholith, Mon-
MODE OF OCCURRENCE OF GOLD IN IGNEOUS ROCKS 23 

tana, and the host rock for several important gold 

mines (Barrell, 1907; Knopf, 1913, 1950). The 

reasons for the apparent gross differences between 

our data and available published data are not 

known, but certainly the possibilities of· analytical 

error and variations in sample purity must be considered. Nonetheless, despite these differences in 

absolute concentration levels, our data on minerals 

exhibit the general relative relationship noted by 

previous workers: sulfides tend to be highest in 

gold whereas mafic silicates and iron and titanium 

oxides tend to be relatively higher in gold than are 

such salic minerals as feldspar and quartz. These 

observations, together with the positive correlation 

of gold abundance and abundance of mafic minerals 

in a rock, led us to suggest previously (Gottfried 

and others, 1969) that gold becomes depleted in the 

residual melt as magmatic differentiation proceeds. 

This generalization appears to be valid for most 

calc-alkalic suites but not necessarily for suites of 

other petrochemical affinities. 

DISTRIBUTION OF GOLD BETWEEN MINERALS 

IN A ROCK 

In order to assess the contribution of each principal mineral to the overall gold budget and at the 

same time check the analytical consistency of rock 

and mineral data, we calculated material balances 

for several samples (tables 9-13). Several features 

of these calculations are noteworthy: 

1. The agreement between total gold in a rock by 

the sum of minerals and that actually measured is fairly good, considering the analytical 

and sampling uncertainties discussed earlier 

( p. 3). For plutonic rocks we consider the 

agreement to be acceptable if the measured and summed values are within a factor 

of two. Furthermore, these calculations suggest an internally consistent data set and the 

lack of systematic bias in the precision of the 

determinations. 

2. Although the mafic _minerals, on the average, 

tend to be higher in gold than the salic minerals, in many of the samples the salic minerals contribute as much or more gold to the 

total rock values than do the mafic minerals. 

This is shown particularly well by highly felsic 

rocks (for example, sample 62K-OO, table 10, 

and sample El 38-167, table 9), in which the 

quartz-plus-feldspar fraction contributes more 

than 90 percent of the measured rock gold. 

3. Except for sample 6K-306 in table 10, the calculations show that either the material halances are in virtual agreement (by factor of 

two) or the total gold by the sum of minerals 

is lower than gold measured directly in rock ; 

in some samples, (BP-1 and Mo-le, table 11) 

the total gold is considerably lower. Low-total 

gold by sum of minerals may be the result of 

any (or a combination) of the following factors: 

(a) Not all the material that contributes. 

to the total rock gold has been considered 

in the material-balance computations. In~ 

asmuch as the mineral separates we ana~ 

lyzed were prepared from crushed rock 

coarser than 200 mesh, a strong possibility exists that the fraction of the rock .. 

finer than 200-mesh may contain a finite 

amount of gold, be it associated with some 

minor mineral phase or even present in 

the native state. 

(b) The final mineral separates analyzed 

may be "over-purified" for materialbalance calculations for gold. Most of the 

mineral separates were prepared originally in connection with other petrologic 

and geochemical studies, which required 

that separates be free of inclusions (generally oxides and sulfides). However, the 

. "impure" (inclusion-rich) mineral fractions that were not analyzed might have 

contributed significantly to the total gold 

budget. 

(c) Systematic analytical bias may exist 

between rock and mineral values. This 

possibility, though it is not in the least 

suggested by the data and we feel it is 

probably remote, nonetheless cannot be 

dismissed entirely. 

Because we wanted another test of material balance and, at the same time, wanted to minimize the 

possible effects of the previously listed factors, we 

analyzed f·our samples of the Butte Quartz Monzonite from underground workings (table 13). These 

samples are hydrothermally altered to varying degrees. Sample 733 is the least altered and shows 

only a small degree of sericitization of feldspar, 

slight alteration of mafic silicates, and trace amounts 

of pyrite and other sulfides; sample 731 is the most 

altered and contains the greatest amounts of sulfides. To minimize possible bias related to sampl~ 

preparation, the samples were disaggregated, but 

not sized, and separated into three density fractions 

by heavy-liquid separation techniques. The data on 
24 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE 9.-Distribution of gold in minerals of some rocks firom the Southern California batholith 

' [Abundance: Calculated from volume-percent mode assuming appropriate density for constituent mineral. Gold in rock, by mineral: Abundance of mineral, expressed in weight percent divided by 100, multiplied 

by amount of gold in mineral (ppb). ND, no data] 

Mineral 

K-feldspar ----------------

Quartz -------------------- Plagioclase ---------------- Biotite -------------------- Hornblende ----------------

Sphene -------------------- Magnetite -----------------

Other ---------------------

Total gold (by sum of 

minerals) --------- Total gold in bulk rock 

(measured) -------

El 88-167 Quartz monzonite 

Abundance 

(weight 

percent) 

32.0 

32.0 

33.0 

2.0 

1.0 

.5 

Gold 

(ppb) 

1.0. 

.6 

3.4 

5.3 

.2 

49.3 

Gold in rock, by mineral 

(ppb) 

0.32 

.20} 

1.12 

.11 

.00 

.25 

2.0 

1.9 

Abundance 

(weight 

percent) 

77.0 

13.0 

7.0 

3.0 

60-2 

Gold 

(ppb) 

0.2 

1.2 

1.3 

ND 

Tonalite 

Gold in rock, by mineral 

(ppb) 

0.15 

.16 

.09 

.4 

2.5 

66 GSC-18 

Abundance 

(weight 

percent) 

77.7 

5.3 

16.4 .2 

.4 

Gold 

(ppb) 

0.3 

.1 

.2 

.5 

ND 

Gold in rock, by mineral 

(ppb) 

0.23 

.00 

.03 

.00 

.3 

.7 

TABLE 10.-Distribution of gold in minerals of some rocks from the Boulder batholith, Montana 

[Abundance: Calculated from volume-percent mode assuming appropriate density for constituent mineral. Gold in rock, by mineral: Abundance of mineral, expressed in weight percent divided by 100, multiplied 

by amount of gold in mineral (ppb). ND, no data; Tr., trace] 

Alaskite 62K-OO Quartz monzonite 6K-306 Granodiorite 2T-1065 

Mineral 

K-feldspar ---------------- Quartz and plagioclase ____ _ 

Biotite -------------------

Hornblende --------------- Magnetite ----------------

~~~=~e _:::::::::::::::::::} 

Total gold (by sum of 

minerals) -------- Total gold in bulk rock 

(measured) ------

Abundance (weight 

percent) 

42.6 

58.4 

1.7 

1.0 

1.3 

Gold 

(ppb) 

1.4 

.2 

2.2 

13.5 

ND 

Gold in rock, by mineral 

(ppb) 

0.60 

.11 

.04 

.14 

.9 

.7 

Abundance (weight 

percent) 

21.2 

60.9 

8.5 

5.8 

1.9 

{ .8 

Tr. 

Gold 

(ppb) 

0.1 

.3 15.8 

1 .2 

8.6 

34.6 

1 Another determination on the hornblende gave a spurious value of 131.7 ppb. 

Gold in rock, by mineral 

(ppb) 

0.02 

.18 

1.34 

.01 

.16 

.10 

1.8 

.8 

Abundance 

(weight Gold percent) (ppb) 

17.0 0.5 67.8 .2 5.3 .8 6.7 .9 2.7 5.1 

.5 ND 

Gold in rock, by mineral 

(ppb) 

0.09 

.14 

.04 

.06 

.14 

.6 

1.0 

TABLE H.-Distribution of gold in minerals of some rocks from the Sierra Nevada batholith and Coast Range plutons, California 

[Abundance: Calculated from volume-percent mode assuming appropriate density for constituent mineral. Gold in rock, by mineral: Abundance of mineral, 

expressed in weight percent divided by 100, multiplied by amount of gold in mineral (ppb). ND, no data; Tr., trace] 

Mineral 

K.-feldspar --------- Quartz and plagioclase ------------- Biotite ------------- Hornblende --------- Hypersthene --------

Magnetite ----------

Other --------------

Total gold (by sum of minerals) ------ Total gold in bulk rock (measured)--

16.8 

63.2 

9.2 

8.8 

1.3 

.7 

MG-1 

0.1 

.1 

.8 

.4 

.4 

ND 

0.02 

.06 

.07 

.04 

.006 

.2 

.6 

62.8 

8.8 

21.3 

10.0 

2.6 

Sierra Nevada batholith 

CL-1 

0.1 

ND 

.3 

.3 

ND 

0.06 

.06 

.03 

.2 

1.6 

13.1 

66.3 

13.7 

5.3 

.4 

1.2 

SL-18 

0.1 

.1 

.6 

.4 

.6 ND 

0.01 

.07 

.08 

.02 

.002 

.2 

.9 

15.9 

64.2 

4.9 

10.7 

2.6 

1.7 

BP-1 

0.2 

.2 

.5 

1.2 

.5 ND 

0.03 

.13 

.02 

.13 

~~~~} 

.8 

6.0 

Tr. 

69 

15 

16 

Tr. 

Coast Range plutons 

Dr-610 

ND 

0.1 

.9 

.5 

ND 

0.07 

.14 

.08 

.s 

.8 

18 

76 

6 

Tr. 

Mo-le 

:c. 

p. 

p. 

.02 

.1 

.4 

ND 

0.04 

.08 

.02 

.1 

6.0 
BEARING OF PRIMARY GOLD ABUNDANCE ON GOLD MINERALIZATION 25 

these fractions clearly indicate that the material balance is better than most observed for those samples 

sized for mineral separation (tables 9-12). Moreover, the sulfide-predominant fraction (specific 

gravity >3.3 is clearly the principal contributor of 

gold. It should be noted the balances are good over 

a wide range ( 1.5-65 ppb) of rock gold abundance. 

As might be expected, the sample for which the 

heaviest (sulfide-bearing) fraction was inadvertently lost shows the worst material balance. 

TABLE 12.-Distribution of gold in minerals of a sample of the 

Silver Plume Granite (G-78), Silver Plume, Colo. 

[Abundance: Calculated from volume-percent mode assuming appropriate 

density for constituent mineral. Gold in rock, by mineral: Abundance of 

mineral, expressed in weight percent divided by 100, multiplied by amount of gold in mineral (ppb). ND, no data] 

Mineral 

Quartz and feldspar ------------

Biotite ------------------------- Muscovite ---------------------- Magnetite ---------------------- Pyrite --------------------------

Other --------------------------

Total gold (by sum of 

minerals) -------------- Total gold in bulk rock 

(measured) ------------

Abundance 

(weight 

percent) 

83.0 

9.0 

5.0 

.5 

.1 

2.4 

Gold 

(ppb) 

0.3 

.3 ND 

1.2 

70 

ND 

Gold in rock, 

by mineral 

(ppb) 

0.25 

.03 

.01 

.07 

-------------------------- .4 

.6 

In summary, our material balances indicate that, 

in most igneous rocks, even the very freshest, the 

gold measured in the rock tends to be greater than 

that indicated by the summation of gold contribution from the principal rock-forming minerals. This 

implies that some of the gold may reside elsewhere 

in the rock, possibly in phases volumetrically small 

but comparatively rich in gold (for example, sulfides) or even as intergranular native gold. To the 

best of our knowledge, the nature of the form or 

forms taken by gold in rocks and minerals is still 

unknown. Questions of the extent to which gold is 

isomorphously taken into mineral structures, the 

proportion of gold fixed in minerals (either isomorphously or simply as included materia:!) to that in 

interstices of the rock, the amount and mode of 

transport of gold, and so on, are beyond the scope 

of the present study. 

REARING OF PRIMARY GOLD ABUNDANCE 

ON GOLD MINERALIZATION 

Abundance data clearly establish the generally 

low concentration levels of gold in unaltered igneous 

rocks ("background levels") of widely differing 

composition and geologic setting. Of more direct 

economic importance, however, is the crucial question : how do these "background levels" of gold relate, if at all, to gold mineralization? Some previous 

investigators (for example, Mantei and Brownlow, 

1967; Voskresenskaya and Zvereva, 1968) have 

linked gold mineralization to a high gold content in 

the magma forming the host rock. Such an association or its antithesis (that is, a low metal content 

in the host rock because of the mineralization) has 

commonly been invoked by economic geologists to 

account for the concentration of metals. This vexing 

problem and contradictory answers to it have been 

discussed and evaluated by Krauskopf (1967). As 

stated at the outset, it is not our purpose to treat 

any region of gold mineralization in detail; nonetheless, in order to support some generalizations 

and to show how our data bear on the relationship 

between primary gold abundance of host rock and 

gold mineralization, we shall make reference to a 

few selected examples. 

BOULDER BATHOLITH REGION, MONTANA 

The Butte Quartz Monzonite and related rocks, 

which form about 70 percent of the exposed Boulder 

batholith, contain nearly all the metallic deposits 

of any economic consequence in the region ; comparatively, the other plutons of the batholith are 

virtually barren in terms of metallic mineralization. 

TABLE 13.-Distributions of gold in different density fractions of some samples of Butte Quartz Monzonite 

from underground workings 

[Rock samples provided by E. C. Robertson, U.S. Geol. Survey. Abundance: Calculated from volume-percent mode assuming appropriate density for con- stituent mineral. Gold in rock, by mineral: Abundance of mineral, expressed in weight percent divided by 100, multiplied by amount of gold in 

mineral (ppb)] 

Sample 731 Sample 733 

Gold in 

Abundance rock, by Abundance 

Density (weight Gold mineral (weight Gold 

fraction percent) (ppb) (ppb) percent) (ppb) 

Sp gr <2.8 ------------ 85 24 20 97.5 0.7 

Sp gr >2.8<3.3 -------- 10 113 11 1.3 5.4 

Sp gr >3.3 ------------- 5 707 35 1.2 22 

Total gold (by sum 

of fractions) --- Total gold in bulk 66 

rock (measured) 65 3 (42) 

1 Material lost during fire assay. 2 Contribution of only those fractions whose specific gravity was less 

than 3.3. 8 Different hand specimen from bulk collection analyzed (data of table 15) 

Sample 725 Sample 720 

Gold in Gold in Gold in 

rock, by Abundance rock, by Abundance rock, by 

mineral (weight Gold mineral (weight Gold mineral 

(ppb) percent) (ppb) (ppb) percent) (ppb) (ppb) 

0.7 86 8.9 7.6 91.0 16 14.6 

.1 9 63.0 5.7 6.7 60 4.0 

.3 5 (1) 2.3 152 3.5 

1.1 2 13 22 

1.5 36 20 3 (.9) 3 (36) 8 (20) 

6 months previous to the experiment to determine gold concentration 

according to density fractions. The agreement is good, in view of the 

heterogeneous nature of these samples. 
26 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

Perhaps the Butte Quartz Monzonite is best known 

as the host rock for the rich copper deposits in the 

Butte district, which have yielded 2,506,253 ounces 

of gold as a byproduct through 1964 (Meyer and 

others, 1968, p. 1376). 

Fresh samples of Butte Quartz Monzonite collected very near mineralized zones are no higher in 

gold (typically less than 1 ppb and averaging 0.6 

ppb) than fresh samples collected from exposure 

areas nearly devoid of mineralized zones (table 21). 

For example, fresh samples from a 4,000-foot borehole in the midst of the Butte district proper and 

within tens of feet of intensely mineralized zones 

have no more than 2.5 ppb gold; values equal to or 

greater than 0. 7 ppb, except for sample 2650, are 

associated with a copper· content four times higher 

than the average for the entire core and reflect the 

presence of a few thin sulfide veinlets ( 0.5-1.5 mm 

in width) (table 14). Furthermore, a gold content 

in excess of 5 ppb is observed only for strongly 

hydrothermally altered samples of Butte Quartz 

Monzonite from underground workings (table 15). 

TABLE 14.-Distribution of gold and copper 

in a drill core (DDH-B-3) in Butte Quartz 

Monzonite, Butte district, Silver Bow 

County, Mont. 

[Samples provided by David D. Blackwell, Southern 

Methodist Univ. and E. C. Robertson, U.S. Geol. 

Survey. Spectrographic analyses for copper by Sol 

Berman, U.S. Geol. Survey) 

Depth (feet) Au (ppb) Cu (ppm) 

850 0.6 32 

950 .3 19 

1,050 .3 87 

1,150 .2 52 

1,350 .3 20 

1.850 .5 67 

2,150 .3 91 

2,250 .1 13 

2,430 .7 350 

2,550 .5 59 

2,650 1.3 24 

2,750 .3 16 

2,850 .4 17 

2,950 .6 20 

3,050 2.4 320 

1,050 0.6 32 

3,160 .5 32 

3,500 .5 11 

3,550 .6 7 

3,995 1.2 380 

Average .6 85 

TABLE 15.-Distribution of gold and copper in some samples of Butte Quartz Monzonite from underground workings in 

the Butte district, Montana 

(Samples collected by E. C. Robertson, U.S. Geol. ~urvey. The samples vary considerably in degree of hydrothermal alteration and sulfide content. Spectrographic analysis of copper by Sol Berman, U.S. Geol. Survey] 

Sample No. Mine Depth (feet) Au (ppb) Cu (ppm) 

720----------· Stewart ______ . 3,400 19.8 4,600 

733----------· ____ do ________ 3,800 .9 78 

725----------· ____ do ________ 3,900 36.5 1.900 

726-L-------· ____ do ________ 4,000 21.0 4,100 727~2 _________ ____ do ________ 4,000 5.1 1.700 

717-B--------· ____ do-------- 4,100 10.3 2,700 

. 718----------- ____ do ________ 4,100 1.6 370 

732----------· ----dO-------- 4,200 4.8 740 

731----------· ____ do ________ 4,400 42.2 800 

723-L-------· Mt. Con. ______ 4,200 11.0 2,400 

722-2--------- ____ do ________ 5,000 .2 92 _g _________ ____ do ________ 5,000 1.9 52 

729----------- Leonard ___ :_ __ . 2,000 4.5 580 8oo ___________ Kelly---------· 4,600 4.3 2,300 

This apparent relation between higher than average gold content and degree of alteration as qualitatively indicated by copper concentration is well 

demonstrated in figure 11, which shows the very 

restricted field occupied by fresh samples in contrast to the large scatter and high gold and copper values found for the altered samples. 

Thus, we conclude that the primary abundance of 

gold in the Butte Quartz Monzonite was low and 

typical of the "background levels" for unaltered 

igneous rocks. We infer further that the concentration of gold to exploitable levels is because of postcrystallization (secondary) introduction and has no 

direct, simple connection to the abundance of gold 

initially present in the magma which formed the 

Butte Quartz Monzonite. Paley, Murovtsev, and 

B.orozenets (1967) reached a similar conclusion 

regarding gold abundance in two intrusions in 

Uzbekistan-that is, high gold abundances reflect 

secondary alteration and remobilization, not primary magmatic concentrations; in particular, a 

plot of amount of secondary sericite against gold 

content shows a well-defined positive correlation 

(fig. 12). 

!Data presented in this report bear on the conclusions reached by Mantei and Brownlow ( 1967) 

with reference to gold mineralization in the Marysville stock, a satellitic pluton of the Boulder batho45 

• 

40 

35 

z 

0 

::i 

....1 30 

iD 

a:: 

w 25 a. 

en 

Ia:: 20 <( • a. 

~ 

c:5 

....1 

0 

<.:) 

•• 

0.05 0.1 0.2 0.5 

COPPER, IN WEIGHT PERCENT 

FIGURE 11.-Variation of gold content with copper content 

in altered samples of Butte Quartz Monzonite from underground workings, Butte district, Montana (table 15). 

The patterned area represents unaltered samples of 

Butte Quartz Monzonite within the Butte district and 

elsewhere (tables 14 and 21). 
BEARING OF PRIMARY GOLD ABUNDANCE ON GOLD MINERALIZATION 27 

1-

:I: 

~ 

i:ij 

3: 

!:: 

u.i 

1-

~ 

>-

a:: 

<( 

Cl 

z 

0 

(.) 

LU 

(f) 

5 

4 

0 

0 

EXPLANATION 

0 

Aktau intrusion 

+ 

Dzhamansay intrusion 

Au, IN PARTS PER BILLION 

FIGURE 12.-Positive correlation of secondary sericite with 

gold abundance for samples from two intrusions in Uzbekistan, U.S.S.R. Data from Paley, Murovtsev, and Borozenets (1967). 

lith that has yielded 1,145,800 ounces of lode gold 

through 1959 (Koschmann and Bergendahl, 1968, 

p. 156). Mantei and Brownlow (1967, p. 234) concluded: "* * * gold of a crystallizing magma 

tends to be concentrated in the residual fluids * * * 

to the extent of forming the ore veins at the edge 

of the stock." The extensive data now available 

clearly suggest to us that, if anything, gold tends 

to become depleted in the residual fluid as crystallization proceeds (p. 6). 

Mantei and Brownlow, aware that the Marysville 

case may not be typical, suggested that "apparent 

concentration" of gold took place in the Marysville 

magma, but not in the Skaergaard intrusion of east 

Greenland (V~ncent and Crocket, 1960a), because 

of a higher original content of gold. However, we 

have shown, from the preceding comparison of gold 

content in fresh versus hydrothermally altered 

Butte Quartz. Monzonite, that low initial gold content in the rock is no deterrent to gold mineralization. Moreover, gold content for the five Marysville 

rocks analyzed by Mantei and Brownlow ( 1967) 

ranges between 4 and 89 ppb and averages 34 ppb; 

hence, their values are anomalously high relative to 

valu.es typical of unaltered plutonic rocks, that is, 

a general average of 2 ppb or less (table 4 and 

fig. 3). We suggest that the samples studied by Mantei and Brownlow very likely have undergone alteration, such that the data do not permit estimates of 

the "original" gold content of the Marysville 

magma. 3 To further complicate matters, though isotopic (potassium-argon) age data indicate that the 

Marysville stock ( 78 m.y., Baadsgaard and others, 

1961) was emplaced within the same time span 

(68-78 m.y.) as the Boulder batholith (Tilling and 

others, 1968), the relation of the gold veins to the 

stock remains uncertain, and we cannot dismiss the 

possibility that gold mineralization at Marysville 

is not related to the stock at all, but rather to poststock (Miocene?) volcanism (Knopf, 1950). Thus, 

the relatively high gold abundance determined by 

Mantei and Brownlow (1967) for rocks and minerals of the Marysville stock can alternatively be 

interpreted as reflecting introduction by postmagmatic processes that may well have occurred considerably later than, and completely unrelated to, 

stock emplacement. 

- DILLSBURG AND CORNWALL DISTRICTS, PENNSYLVANIA 

The Dillsburg arid Cornwall intrusions are mineralogically and chemically similar and show ironenrichment differentiation trends, the degree of 

enrichment being greater in the Dillsburg sheet 

(Lapham, 1968). In addition to the magnetite deposits (limestone replacement) associated with both 

these intrusions, the only gold produced in any significant quantity in Pennsylvania (37,459 ounces 

through 1959) comes from the Cornwall mine; the 

gold is recovered from copper concentrates ( chalcopyrite) associated with the magnetite ore (Koschmann and Bergendahl, 1968, p. 231). Hotz (1953) 

believed that the magnetite ore at Dillsburg was 

derived directly from the adjacent diabase sheet by 

volatile-rich, iron-bearing fluids being expelled just 

before the sheet consolidated at its present level. 

However, Lapham ( 1968) has summarized geologic 

evidence supporting the thesis that, at Cornwall, ore 

mineralization occurred a finite, but unknown, interval of time after the solidification of the chilled margin of the diabase sheet; he has postulated that ore 

fluids, rather than being derived from the crystallizing diabase at its present level, originated by fractionation from the diabase ~agma as it differentiated 

in a deeper seated source area. In any case, mineralization in both areas is linked in some manner 

to the magma which produced the diabase-granophyre intrusions. 

The Dillsburg intrusion has had a complex petrologic history, and one of its unusual petrochemical 

3 Recently completed geochemical profiles across many veins in the Marysville stock show anomalies in metal content over the immediate vicinity of 

the veins, but away from the zones of mineralization, gold abundance in 

the rock can be as low as the value for unaltered plutonic rocks, that is, in 

the range of 1-2 ppb (Mantei and others, 1970). -
28 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

features, as compared with the Cornwall and other 

diabase-granophyre suites, is the abnormally high 

degree of iron enrichment characteristic of rocks 

formed during the intermediate stages of crystallization. Hotz ( 1953) suggested that during this 

stage volatile-rich fluids, generated lower in the 

crystallizing sheet, were apparently capable of mobilizing iron and ultimately depositing magnetite in 

the overlying sedimentary strata; the development 

of late hydrous silicates (at the expense of pyroxene) and of other alteration products, Hotz postulated, also mark the passage of hydrothermal fluids 

through the system. Davidson and Wyllie (1968), 

utilizing detailed optical observations and electronprobe analyses, have demonstrated the breakdown 

of primary iron and titanium oxides in many rocks 

of the Dillsburg intrusion; this breakdown leaves 

skeletal ilmenite and forms a second-generation, 

low-titanium magnetite; Davidson and Wyllie attributed the origin of secondary hydrous minerals to 

the same alteration process. 

We have shown (p. 12) that gold content for 

the Dillsburg intrusion and the one chilled margin 

sample from Cornwall is distinctly higher relative 

to other samples of chilled margins of dikes in the 

same area; gold content is also higher than in other 

suites from the Triassic basin of the Eastern United 

States, not to mention compositionally similar rocks 

elsewhere. These high concentrations, we suggest, 

reflect alteration effects, not primary features. It is 

significant to note that the high gold content of the 

Dillsburg rocks is matched by a high copper content (fig. 10). Although the mechanism contributing to these anomalously high gold content is obscure, available geologic and petrographic evidence 

indicate that ample opportunity existed for the redistribution and concentration of gold by late-stage 

fluids, which caused alteration and replacement of 

primary oxide and silicate minerals and which resulted in the magnetite deposits. Moreover, the 

Cornwall intrusion r~presents another example of. 

gold production from a mineralization associated 

with a host rock whose primary gold abundance is 

not significantly higher or lower than "background 

levels" for the province as a whole. 

JEROME DISTRICT, CENTRAL ARIZONA 

Because of its close association with sulfides, gold 

is economically important in all the mines of the 

Jerome district; approximately 1,890,000 ounces of 

byproduct gold have been produced from the area, 

principally from the United Verde and United 

Verde extension copper mines (Anderson and 

Plagioclase 

Quartz 

EXPLANATION 

Au (ppb) 

Yavapai {. 0 <1 

Series • 1- 5 

• >5 

Orthoclase 

FIGURE 13.-Normative plagioclase, orthoclase, quartz, and 

variation in gold content of Precambrian rhyolites and 

quartz porphyry of the Yavapai Series, central Arizona. 

Solid line encloses field for samples of quartz porphyry 

and of the Ash Creek Group; dashed line encloses field 

for samples of the Alder Group. Patterned area represents young unaltered glassy rhyolitic rocks from Wyoming and California, all of which contain less than 1 ppb 

gold. Normative data from Anderson (1968, fig. 6); goldabundance data from ta~~e 39. 

Creasey, 1958). Anderson (1968) has ably documented the complex relationships between metamorphism, metasomatism, and hydrothermal alteration of the silicic volcanic rocks of the Yavapai 

Series (Precambrian). 

As noted by Anderson (1968), chemical data indicate that the rhyolites as a group are characterized by a low total..;alkali content and highly variable ratios of sodium to potassium, as compared 

with fresh rhyolitic obsidians from elsewhere in 

the Western United States (fig. 13). In addition, 

Anderson demonstrated that iron-magnesium metasomatism (iron and magnesium were probably derived from older basaltic rocks) has affected some of 

the rhyolites. Rocks of the Alder Group are more 

uniform in alkali content (expressed in terms of 

normative feldspars) than those of the Ash Creek 

Group or of the quartz porphyry (Anderson, 1968, 

fig. 6). Gold content of samples of the Alder Group 

is less than 1 ppb except for two samples (fig. 13) ; 

significantly, those two samples have an anomalously 

low potassium (hence, normative Or) content, less 

than 0.22 percent K20 rather than the range of 
BEARING OF PRIMARY GOLD ABUNDANCE ON GOLD MINERALIZATION 29 

1.6-4.0 percent for the other samples of the group 

(Anderson, 1968, table 3). 

Rhyolites of the Ash Creek Group tend to have 

not only a higher iron content than those of the 

Alder Creek but also a more variable and lower 

alkali content. Not too surprisingly, gold content in 

these rocks is likewise extremely variable but, on 

the whole, much higher. The highest gold values 

observed for the Ash Greek Group are for two chloritized samples (table 39, Nos. 4 and 5) underlain 

by basalt. Similarly, the quartz porphyry is characterized by a variable alkali content and, accordingly, a variable but relatively high gold content 

(table 39 and fig. 13). 

Thus, we conclude from our data and those of 

Anderson ( 1968) that a gross correlation exists 

between variable but relatively high gold content 

and variable and lower alkali content (also higher 

iron content). In other words, these results strongly 

suggest that gold enrichment in these rocks is related to secondary processes, which caused loss of 

alkalis and apparent gain of iron and magnesium, 

and therefore has no direct relationship to variations in primary gold abundance. 

BULLFROG DISTRICT, NYE COUNTY, NEV. 

Gold production from the Bullfrog district 

through 1959 was 120,400 ounces (Koschmann and 

Bergendahl, 1968, p. 191). According to Cornwall 

and Kleinhampl ( 1964), most of the gold and silver 

deposits are in fissures and veins related to normal 

faults; these faults occur either near the rim of the 

Bullfrog Hills caldera or near the contact between 

the central domal uplift, where basement rocks are 

exposed, and the Tertiary pyroclastic material 

within the caldera. Cornwall and Kleinhampl suggested that the ore-bearing solutions were prob.,. 

ably derived from a magma chamber beneath the 

present location of the caldera. Except for the three 

closely associated altered samples (2.0-22 ppb gold, 

table 40) thought to be part of the lower part of 

the caldera, the rhyolites; latites, and basalts associated with the caldera do not contain any more 

gold than their unaltered counterparts from elsewhere in the Western United States (table 7). 

Again, we suggest the occurrence of gold mineralization in this region is not obviously, if at all, 

related to primary gold abundances in the host 

rocks. It is perhaps worthwhile to note that our 

interpretation of data for gold mineralization in 

the Bullfrog district, which is underlain by Tertiary volcanic rocks, does not differ in principle for 

mineralization of the Jerome district, Arizona, 

which is underlain in large part by Precambrian 

volcanic rocks of grossly similar lithology. 

THE MOTHER LODE, CALIFORNIA 

The Mother Lode of California, a belt about 120 

miles long and 1-4 miles wide in the western foothills of the Sierra Nevada, has yielded through 1959 

about 13,300,000 ounces of lode and byproduct 

gold, that is, roughly a third of total lode and byproduct production from California (from data 

compiled by Koschmann and Bergendahl, 1968). 

The host rocks for the ore deposits are metamorphic 

rocks (slates, schists, and greenstones) of Jurassic 

and Carboniferous age which have been intruded by 

plutonic rocks ranging in composition from peridotite (serpentinized) to granodiorite. 

Many of the world's largest primary gold deposits occur within granite-greenstone terranes similar to that hosting the Mother Lode. From studies 

mainly on such deposits in Precambrian greenstone 

belts of Canada and South Africa, many previous 

investigators have advocated the hypothesis that the 

gold ultimately had its source in the volcanic and 

clastic country rocks, rather than in the granitic 

intrusions (Macgregor, 1951; Boyle, 1960). In contrast, Knopf (1929) suggested that the source of 

gold in the Mother Lode was the magma from which 

the granitic rocks were derived. Unfortunately, only 

extremely limited quantitative abundance data on 

gold in rocks from such greenstone-granite associations are available to test these conflicting 

hypotheses. 

Viljoen, Saager, and Viljoen (1969) reported 

average values of gold for samples of the country 

rock of the Steynsdorp Goldfield, South Africa 

(metabasalt and ultramafic rocks, 5-20 ppb; tuffaceous shale, 75 ppb), higher than the average value 

for the Steynsdorp granite ( < 5 ppb) · which intrudes them. However, it should be noted that Viljoen, Saager, and Viljoen claimed only a sensitivity 

of 5 ppb fo:r their gold determinations. Nonetheless, 

on the basis of gold abundance data, along with 

other geologic and geochemical arguments, Viljoen, 

Saager, and Viljoen contended that the gold was 

derived from the country rock, not the intruding 

granite. 

Our more precise, but nonetheless limited, data on 

Mother Lode (table 16) show that, excluding the 

relatively high value of one of the. slate samples 

(30.6 ppb), the gold content of the country rock is 

typical for basic and intermediate volcanic rocks 

and is not appreciably different from that for rocks 

of the Sierra Nevada batholith. We emphasize, how-
30 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

ever, that no data on gold abundance are available 

for granitic rocks within the Mother Lode district 

and that, inasmuch as the greenstones are presumably regionally metamorphosed volcanic rocks, their 

gold abundance may not necessarily represent primary abundances. 

TABLE 16.-Comparison of gold concentration in samples of 

host rocks from the Mother Lode district with samples from 

the Sierra Nevada batholith 

Average 

Number gold 

of Range content Suite or location Rock type samples (ppb) (ppb) 

Mother Lode district_ __ Meta volcanics 1.2- 3.4 2.1 

(greenstones) . 

Slate ----------- 2 3.6-30.6 

Sierra Nevada Quartz diorite ___ 1 1.4 

batholith.1 Granodiorite ---- 11 .4- 5.2 1.5 

Quartz monzonite to alaskite. 5 .3- 1.3 .8 

1 Data from table 19. 

Thus, the meager data presently available to us 

makes it premature to speculate as to the source of 

the gold in these major deposits in greenstonegranite terranes. In view of the important economic 

benefits that might accrue, a comprehensive investigation, within the framework of background data 

given in this reconnaissance report, on the gold geochemistry of the Mother Lode and other deposits in 

similar settings is clearly needed. before the critical 

questions of the source and of the concentration of 

gold can be answered. 

THERMAL SPRINGS, YELLOWSTONE NATIONAL PARK, 

WYO. 

The association of epithermal gold and silver deposits with volcanic hot springs or thermal activity 

is not uncommon and has been discussed in detail 

by White ( 1955). For example, in the Yellowstone 

area, the formation of veinlets of auriferous pyrite 

from thermal waters of Monarch Geyser (Norris 

Basin) has been noted by Weed (1905) .' For the 

Taupo Volcanic Zone, New Zealand, Weissberg 

(1969) reported high concentrations of gold (as 

much as 85,000 ppb), silver, mercury, arsenic, antimony, and thallium in siliceous sinters and precipitates currently depositing from thermal waters containing only 0.04 ppb gold; Weissberg, however, did 

not present data on gold content in the volcanic 

rocks through which the thermal waters course. 

J. J. Rowe and others of the U.S. Geological Survey are currently investigating the gold content of 

the thermal waters and their precipitates in Yellowstone National Park. Preliminary data indicate 

that gold content is very low in the thermal waters, 

generally 0.004-0.040 ppb, yet rather high in sinters 

depositing from such waters, generally 5-50 ppb 

but up to 5,000 ppb (table 17). Sinters having high 

gold. concentrations also contain correspondingly 

higher amounts of arsenic, antimony, and mercury. 

On the other hand, the host rhyolites of the thermal 

springs system only contain low amounts of gold, 

0.1-1.3 ppb (table 38). 

TABLE 17.-Ranges of gold content in rhyolite, thermal waters, 

and precipitates from thermal waters, Y ellow~-tone National 

Park, Wyo. 

[From table 38 and preliminary unpublished data] 

Gold (ppb) 

Rhyolites ---------------------------------- 0.1 -1.3 

Thermal waters ---------------------------- 1 .004- .1 

Precipitates -------------------------------- 2 .5 -5,000 

1 Most values. however, are in the range of 0.004-0.040 ppb. Because the 

few .samples that contain 0.1 ppb gold also have an unusually high amount 

of colloidal silica, ·the amount of gold actually in solution may be considerably less than 0.1 ppb. 

2 Most commonly 5-50 ppb. 

These results are in general accord with those of 

Weissberg ( 1969) and likewise indicate that precipitates having high concentrations of gold, nearly 

ore grade, are actively forming from solutions having very low gold levels. Furthermore, our data 

show that above-average gold concentration in the 

country rock is not required for the rocks to serve 

as a possible· source for the gold. The rhyolites of the 

Yellowstone area, for example, could readily supply all the gold in the thermal systems (including 

precipitates) by yielding about 10 percent or so of 

their original content. Calculations by Weissberg 

( 1969), based on discharge rates and life span of 

the W airakei geothermal system in New Zealand, 

indicate that a strong argument can be made for the 

formation of some economic epithermal gold deposits 

by precipitation from dilute hydrothermal solutions. 

These collective results bear on, and render somewhat moot, the question of the .ultimate source of the 

gold (and perhaps of other metals) in metallization 

processes. One rather obvious implication is, of 

course, that gold mineralization bears no simple 

relationship to known or assumed primary gold 

abundance of the host rock and that mechanisms of 

gold transport (or remobilization) and deposition 

(or redeposition), rather than initial concentrations, 

play the dominant role in gold mineralization. 

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32 DISTRIBUTION OF GOLD· IN IGNEOUS ROCKS 

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34 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

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TABLES 18-44 
36 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE lB.-Distribution of gold in rocks of the 

Southern California batholith 

Sample No. 

SLRM-354-------· 

334-------· 

299-------· 

230-------· 

66GSC-27 --------· 

10--------· 

SLR-213---------· 685 _________ , 

582---------· 

60-2-------------· 

1-------------· El 38-28 _________ _ 

Ra-3-------------

66GSC-20--------· 

18--------· El 38-126 ________ _ 64GSC-2 _________ . 

4---------· 

3---------· 

S-11-------------

13-------------· 

14-------------· 

12-------------· 9 ______________ , 

10 __ .:, __________ _ 15 _____________ _ 

6--------------· 

Cor-1------------· 

El 38-265---------

167---------

Cor-3------------

Rock type Au (ppb) 

Olivine norite ----------------------------- 0.8 

N orite ------------------------------------ 1.5 

Hornblende gabbro ------------------------ 11.6 

Quartz-biotite norite ----------------------- 9.3 

Gabbro ----------------------------------- . 7 ____ do------------------------------------- 2.7 

Green Valley Tonalite ----------'------------ 10.7 ____ do _______ .;._____________________________ 1.1 

____ do------------------------------------- 11.3 

Lakeview Mountain Tonalite --------------- 2.5 

Bonsall Tonalite --------------------------- 1.7 _ ___ do------------------------------------- .8 

Tonalite ---------------------------------- 3. 7 Tonalite (sphene rich) -------------------- .5 ____ do------------------------------------- .8 

Granodiorite ------------------------------ 1.2 

Woodson Mountain Granodiorite ------------ .6 ----dO-----------------~------------------- .5 Woodson Mountain Granodiorite (aplite)---- .3 

Woodson Mountain Granodiorite------------ .5 ____ do------------------------------------- .3 ____ do------------------------------------- .3 ____ do------------------------------------- .4 ____ do------------------------------------- .3 _ ___ do------------------------------------- .3 _ ___ do--------·----------------------------- .2 ____ do------------------------------------- .3 ____ do------------------------------------- .5 Quartz monzonite (fine phase) ------------- .5 

Quartz monzonite (coarse phase) ----------- 1.9 

Granite (altered) ------------------------- 5.6 

TABLE 19.-Distribution of gold in rocks of the Sierra Nevada, 

Coast Range, and Transverse Ranges, Calif. 

[Samples supplied by F. C. W. Dodge and D. C. Ross, 

U.S. Geol. Survey] 

Sample No. 

BCc-12----------· 

. BCa-20----------· 

BCc-13--------~-­

SL-18------------

BP-8------------· 

1------------· 

FD-4------------· 20 ___________ _ HL-29 __________ _ 

KR--------------· 

BP-2------------· 

R-99-------------

FD-2------------· 

3------------· 

BP-3------------· 

~~{_-_-_-_-_--:_-_-_-_-_-_. 

Mo-1-----------· Dr-100 __________ _ 

510----------· 

Dr-321----------· v -4_ _________ :_ __ _ 

Rock type Au (ppb) 

Sierra Nevada 

Mount Givens Granodiorite --------------- 0.4 ____ do------------------------------------- 1.9 

Granodiorite of Dinkey Creek type -------- 1.8 

----dO------------------------------------- .9 Tinemaha Granodiorite -------------------- .5 

----dO------------------------------------- 5.2 

Granodiorite of the Raymond quarries------ 1.0 

----dO--------.----------------------------- 3.0 

Biotite granite of Dinkey Lakes ----------- .9 

Granodiorite of the Goddard pendant ------ .8 

Granodiorite of McMurray Meadows ------- .8 

Alaskite of Evolution basin ---------------- 1.3 Hunter Mountain Quartz Monzonite -------- .6 Paiute Monument Quartz Monzonite ------- .9 

Quartz monzonite of Mount Alice mass_____ .3 

Pyroxene quartz diorite ------------------- 1.4 

Lamarck Granodiorite ---------------------- .5 

Coast Range 

Quartz monzonite, Monterey --------------- 2.1 

Granodiorite, Red Hills -------------------- .7 

Quartz diorite, Bodega Head -------------- .5 

Transverse Ranges 

Granodiorite. Long Buttes, Los Angeles Co__ 0.7 

Granodiorite Holcomb Ridge, Los Angeles Co- .2 

TABLE 20.-Distribution of gold in rocks of the Idaho batholith 

[Samples supplied by B. F. Leonard and E. S. Larsen, Jr., 

Sample No. 

CPR-117 --------- 118 ______ :._ __ L54-90Q _________ _ 900A ________ _ 47L81 ___________ _ 47L227 __________ _ 

47Ll13 __________ _ 

47L288 __________ _ 47L70 ___________ _ L253 ____________ _ L112 ____________ _ 

L255 ____________ _ L304 ____________ _ 

L30L ___________ _ L295 ____________ _ 

U.S. Geol. Survey] 

Rock type Au (ppb) 

Diorite ----------------------------------- _ ___ do-------------------------------------

Quartz diorite ----------------------------- _ ___ do-------------------------------------

gorphJ:rit!c ====~~===================================== tonalite gneiss ----------------

-~~~do~~~~~e __ ::::::::::::::::::::::-------- ____ do ____________________________ _ 

~~]I~~:~~::~:::~:::~::~~:~~~:~:~~~~~::~~~ 

0.5 

2.6 

.2 

1.5 

2.5 

6.0 

2.1 

3.1 

3.2 

1.9 

2.8 

.8 

1.3 

5.2 

1.4 

TABLE 20.-Distribution of gold in rocks of 

the Idaho batholith-Continued 

Sample No. 

L288-------------

L58-88-----------

L53-537 A-------- L59-1765 ________ _ L61-1182 ______ ...: __ . L62-1784B _______ _ L64-2559 ________ _ 

CPR-123--------- 47L219 __________ _ 

L-169------------

84------------- 47-L-272 __ :_ _____ _ L-263 ___________ _ 

209 ___________ _ 201 ___________ _ 

L62-1784A _______ _ 

L58-130----------

L53-554----------

L58-128L--------

L64-2609---------

Rock type Au (ppb) 

Granodiorite ------------------------------ 3.0 ____ dO------------------------------------- .6 ____ dO------------------------------------- .6 ____ dO------------------------------------- ,3 ____ dO------------------------------------- .2 ____ dO------------------------------------- .1 ____ do------...:------------------------------ 2.0 ____ dO------------------------------------- .9 

Quartz monzonite ------------------------- 2.7 ____ dO------------------------------------- 1.1 ____ dO------------------------------------- 1.1 Muscovite quartz monzonite --------------- .6 _ ___ dO------------------------------------- .9 _ ___ do------------------------------------- .4 

Granite (fine grained) -------------------- .5 

Alaskite ---------------------------------- .3 ____ do------------------------------------- .6 ____ dO------------------------------------- .2 ____ do------------------------------------- .4 

Aplite ------------------------------------ .8 

TABLE 21.-Distribution of gold in rocks of the 

Boulder batholith, Montana 

Sample No. 

8-1419 __________ _ 

4T-349-----------

2T-1065----------

7W-2L----------· 3T-273 __________ _ 

1K-24L---------- 6K-306 __________ _ 

DDH-B-3--------· 62K-oo __________ _ 

Rock type Au (ppb) 

Syenogabbro ------------------------------ 0.6 

Unionville Granodiorite -------------------- 3.4 

Granodiorite of Rader Creek pluton-------- 1.0 

Quartz monzonite of Donald pluton--------- .5 

Clancy Granodiorite 1 ---------------------- 2.0 

Quartz monzonite of Homestake pluton_____ .5 

Butte Quartz Monzonite ------------------- .8 ____ do------------------------------------- 2 .6 Alaskite related to Butte Quartz Monzonite_ .7 

1 Clancy Granodiorite of Knopf (1957) is coextensive with the Butte Quartz Monzonite. 2 Average of 19 samples from a 4,000-ft. borehole (see table 14). 

TABLE 22.-Distribution of gold in rocks of the Tatoosh 

pluton, Mount Rainier National Park, Wash . [Samples supplied by T. L. Wright, U.S. Geol. Survey] 

Sample No. 

TP-5----------· 

9----------· 

25---------· 

32---------· 

66---------· 

72---------· 

7 4---------· 

76---------· 

81---------· 112A ______ _ 152 ________ _ 17L _______ _ 201-_______ _ 21L _______ _ 

TP ------------· 

Rock type Au (ppb) 

Granodiorite ------------------------------ ____ do------------------------------------- ____ do------------------------------------- ____ do------------------------------------- ____ do------------------------------------- ____ do------------------------------------- ____ do------------------------------------- ____ do------------------------------------- ----do ______________________ .:_ _____________ _ 

_ ___ do-------------------------------------

----dO-------------------------------------

_ ___ do _________________________________ .;. __ _ 

_ ___ do-------------------------------------

B~~~~?~-==============~======:::::::::::::: 

0.3 

2.8 

.4 

3.8 

.8 

.6 

4.2 

1.4 

.5 

.7 

.5 

.9 

.9 

.6 

.6 

TABLE 23.-Distribution of gold in four plutonic rocks 

from the Rocky Mountains, Colo. 

Sample No. 

7179----------· 

77 4 1----------· 

7395----------· 

G-78----------

Rock type and location Au (ppb) 

Quartz monzonite, Mount Princeton_________ 0.4 

Granite, Mount AnterO--------------------- .4 

Quartz diorite, Mount Princeton____________ .5 

Granite, Silver Plume quarry_______________ .6 

TABLE _24.-Distr~bution of_ gold ~n plutonic rocks of the 

Whtte Mountaw Plutomc Senes, New Hampshire 

[Samples supplied by A. P. Butler, U.S. Geol. Survey] 

Sample No. 

BNH-5--------- 13 _______ _ 

56 _______ _ 68 _______ _ 49 _______ _ 

52 _______ _ 36 _______ _ 39 _______ _ 40 _______ _ 

Rock type Au (ppb) 

Biotite granite ---------------------------

====~~===================================== _ ___ do-------------------------------------

====~~===================================== 

====~~===================================== ----dO-------------------------------------

0.5 

.9 

.4 

.3 

.5 

.5 

.4 

.8 

.s 
TABLES 37 

TABLE 24.-Distribution of gold in plutonic rocks of the 

White Mountain Plutonic Series, 

New Hampshire-Continued 

Sample No. Rock type Au (ppb 

BNH-57 -------· Biotite granite ---------------------------- 0.3 88 _______ _ ____ dO------------------------------------- .2 55-S-824 ______ _ ____ dO------------------------------------- .8 807 ______ _ ____ do------------------------------------- .5 882 ______ _ ____ do------------------------------------- 1.6 821_ _____ _ ____ do------------------------------------- 1.2 

BNH-67 -------- Biotite-amphibole granite ------------------ .8 

64-------- so _______ _ ____ dO------------------------------------- .5 

Amphibole granite ------------------------ .4 

25-------- 28 _______ _ _ ___ do------------------------------------- .2 

8 ____ ____ do------------------------------------- .8 :_ ___ _ 45 _______ _ Gabbro Riebeckite ______ granite ------------------------ .4 :_ ____________________________ . .8 

48 _______ _ Monzodiorite ------------------------------ .8 44 _______ _ 42 _______ _ Syenite ----------------------------------- .8 

Nepheline syenite ------------------------- .8 

7--------- 20 _______ _ Syenite dike ------------------------------ .4 

Quartz syenite -·--------------------------- .8 

TABLE 25.-Distribution of gold in some alkalic plutonic rocks 

from North Carolina and South Carolina 

[Samples supplied by R. E. Lemmon, Univ. of North Carolina, 

and David Gottfried, U.S. Geol. Survey] 

Sample No. 

A-3------------

69G-9a ________ _ 9b ________ _ 

A-2------------

1-1 E-1------------ ______ .. _____ _ 

2------------· 69G-11a _______ _ G-4 ___________ _ 

69G-11 b _______ _ 

8---------- 8 _________ _ 

14--------- 18 ________ _ 

Rock type and location Au (ppb) 

Quartz monzonite, Salisbury pluton, 0.7 Rowan County, N.C. 

----dO------------------------------------- .2 ____ do------------------------------------- .5 _ ___ dO------------------------------------- 1.4 ____ dO------------------------------------- 1.4 ____ do------------------------------------- 1.8 ____ dO------------------------------------- 1.2 

---~dO------------------------------------- .2 ____ do _____________________ ;________________ 2.8 

____ do------------------------------------- .2 ____ do------------------------------------- .3 Granite, Pageland, S.C--------------------- .2 

Gabbro, Concord quadrangle, North Carolina .7 Syenite, Concord quadrangle, North Carolina .2 

TABLE 26.-Distribution of gold in volcanic rocks 

from Hawaii 

[Samples supplied by H. A. Powers, T. L. Wright, and A. T. Anderson, 

U.S. Geol. Survey] 

Sample No. 

HW-6-----------· 

HW-6 (G)-------· 

TLW67-17 -------· 

HK-1868G-2 _____ _ 1919 ________ _ 

1954-L ______ _ 

1959-C p -----------· ______ _ 

HK-1955-AP AG -----

____ _ 

EG ____ _ 

KG ____ _ KL ____ _ Q ______ _ 

z ______ _ 

1697 -------------· 

TLW-67-GL _____ _ 

HML-1868-------· HML-1887-D ____ _ L ____ _ s ____ _ 1899-G ____ _ 

1907-KG ___ _ 1942-D ____ _ 1942-G ____ _ 

1950-L V ---· 

Rock type and location 

KILAUEA 

Prehistoric 

Au (ppb) 

Basalt ----------------------------------'-- 4.6 

Glass concentrate from sample HW-6_______ 1.5 

Basalt, Cone Crater ----------------------- 4.8 

Historic summit eruptions 

Glassy basalt from spatter cone, 1868 lava__ 2.2 

Splatter from Halemaumau, 1919 ---------- 2.4 

Basalt, 1954 eruption --------------------- 2.0 

Basaltic pumice, 1952 eruption ------------ 2.7 

Crust on lava lake, 1D59 eruption --------- 1.8 

East rift zone 

Lava flow from vent A, 1955 eruption______ 1.0 

Glassy crust of spatter cone, vent A, 1955 1.1 

eruption. 

Glassy surface of lava flow, vent E, 1955 5.2 

eruption. 

Glassy top of Kii flow, 1955 eruption______ 1.0 

Interior of Kii flow. 1955 eruption_________ 1.1 

Glassy lava from vent Q, 1955 eruption---- .5 

Glassy lava from cone near vent Z, 1955 2.0 

eruption. 

Submarine basalt, glassy fraction, from 2.0 

depth of 2,960 meters. 

MAUNA LOA 

Picrite basalt, 1852 eruption -------------- 1.7 · Hypersthene basalt, 1868 eruption --------- 2.1 

Dense interior of 1887 flow ---------------- 1.9 

Glassy spatter, 1887 eruption -------------- 6.6 Glassy crust of 1887 flow, upper vent ------ 2.0 

Glassy crust on lava, 1899 eruption -------- 2.7 

Glassy crust on lava, 1907 eruption -------- 1.8 

Interior of 1942 flow ---------------------- 2.0 

Glassy part of 1942 flow ------------------ 2.0 

Glassy crust of 1950 flow ------------------ 2.8 

TABLE 26.-Distribution of gold in volcanic rocks 

from Hawaii-Continued 

Sample No. Rock type and location Au (ppb) 

HALEAKALA 

llOL------------· Picrite basalt ----------------------------- 0.2 

1102-------------· Andesite ---------------------------------- .8 

1108-------------· _ ___ do-----------------------------------'-- .5 1104 _____________ _ _ ___ do------------------------------------- 1.8 1105 _____________ _ _ ___ do------------------------------------- 8.9 

1106-------------· _ ___ do------------------------------------- .8 

HONOLULU VOLCANIC SERIES 

1040L-----------· Nepheline melilite basalt ------------------ 1.4 

KOOLAU VOLCANIC SERIES 

10408------------· Nonporphyritic basalt --------------------- 1.4 

TABLE .27.-Distribution of gold and copper in volcanic rocks 

from the Mid-Atlantic Ridge and East Pacific Rise 

[Samples supplied by A. E. J. Engel, A. T. Myers, and David Gottfried, 

U.S. Geol. Survey, and W. G. Melson, Smithsonian lnst.] 

Sample No. 

AD-2----------· AD5-18 ________ _ 

AD-4----------· 

PVD-17 --------

1---------

4-C-------

8--------- PV-77 50 _________ 

---------· _ 816 ________ _ 

805--------· 814 ________ _ 172 ________ _ 

GU-77 ---------· 15 _________ _ 52 _________ _ 22 _________ _ 

111221 .18 ______ _ .22 ______ _ 

.27------- .41 ______ _ 

111228.7-------- 111229.1_ ______ _ .6 _______ _ 

.7--------

111280.5 _______ _ .19 ______ _ 

111283.L ______ _ 

111284.244 _____ _ .280 _____ _ .292 _____ _ 

111286.108 _____ _ .104_ ____ _ 

111287 ,8 _______ _ .76 ______ _ 

.67------- 111288.8 _______ _ 

111289.178------

DR-10R _______ _ Dr-101_ _______ _ 

Rock type 

MID-ATLANTIC RIDGE 

Tholeiite ------------------------ ---- do -------------------------- ---- do --------------------------

EAST PACIFIC RISE 

Tholeiite ------------------------ ---- do -------------------------- ---- do -------------------------- ---- do -------------------------- Alkalic basalt -------------------

---- do -------------------------- ---- do -------------------------- ---- do -------------------------- ---- do -------------------------- ---- do --------------------------

---- ---- do _______________________ 

-------------------------- _: __ 

---- do -------------------------- ---- do --------------------------

EAST PACIFIC RISE Juan de Fuca ridge-Blanco fracture zone 

Dredge 1 

Tholeiite ------------------------

---- do -------------------------- ---- do -----------------------.--- ---- do -------------------------- ---- do -------------------------- ---- do -------------------------- ---- do -------------------------- ---- do --------------------------

Dredge 2 

---- do -------------------------- Tholeiite, pillow lava, sections from 

rind (1) to interior. (6); 1 __________ ,;. __________________ _ 

2 ------------------------------

8 ------------------------------

4 ------------------------------

5 ------------------------------

6 ------------------------------

Dredge 8 

Tholeiite 

Dredge 5 

____ do -------------------------- ---- do --------------------------

---- do -------------------------- ---- do -------------------------- ---- do --------------------------

Dredge 6 

Tholeiite ------------------------- ---- do -------------------------- ---- do -------------------------- ---- do -------------------------- ---- do --------------------------

Dredge 10 

Glassy rind of tholeiitic basalt_ __ _ 

Interior of flow ------------------

Cu 

(ppm) I 

66 

81 

75 

75 

64 

87 

80 

42 

56 

48 

20 

84 

87 

10 

15 

88 

58 

Au 

(ppb) 

0.6 

1.6 

.5 

1.0 

1.8 

1.0 

2.0 

1.2 

.8 

1.8 

.9 

.9 

1.0 

.8 

.s 

.2 

.4 

0.8 

.2 

.1 

.4 

.8 

.4 

.6 

.8 

.8 

.5 

4.6 

1.0 

.9 

.5 

.4 

.8 

.2 

.2 

.6 

.6 

.7 

.2 

.4 

.8 

.2 

.8 

.2 

.2 
38 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE 27.-Distribution of gold and copper in volcanic rocks 

from the Mid-Atlantic Ridge and 

East Pacific Rise-Continued 

Sample No. Rock type 

Dredge 11 

111243.5-------- Tholeiite 

Dredge 12 

111244.10 ______ _ Tholeiite ------------------------ .15------- ---- do --------------------------

Dredge 18 

111245.3 _______ _ Tholeiite ------------------------ .93 ______ _ ---- do -------------------------- .95 ______ _ ---- do -------------------------- .97D _____ _ ---- do --------------------------

Cu Au 

(ppm)1 (ppb) 

0.5 

.4 

.6 

.5 

.4 

.3 

.1 

1 R. G. Havens, analyst (Engel and others, 1965). 

TABLE 28.-Distribution of gold in plateau basalts and other 

volcanic rocks, Oregon and Washington 

[Samples supplied by T. P. Thayer, U.S. Geol. Survey, and A. C. Waters] 

Sample No. Location Au (ppb) 

BASALTS OF THE COLUMBIA RIVER GROUP Picture Gorge Basalt 

26-15-20 ________ _ 

5-18-20----------· 

PG-12-----------· 

RLH-19---------· 13---------· 

CB-8------------· 

V-19-7 ----------· 

ABG-15A-55 ____ _ DLP-57-36 ______ _ P55-9-1A ________ _ 

Little Horse Spring, Crook County, Oreg___ 2.7 East of Drakes Butte. Maury Mountains, 3.2 Crook County, Oreg. Picture Gorge section, Grant County, Oreg__ 3.0 

____ do------------------------------------- .5 ____ do------------------------------------- 2.3 

Yakima Basalt 

Crescent Bar, Grant County, Wash ________ _ 0.8 Basal flow, Waterville, Douglas County, 11.0 Wash. 

Estacada quadrangle, Oregon -------------- ____ do-------------------------------------

DLP-56-21_ _____ _ Brownsville quadrangie, Oregon ------------ Salem quadrangle, Oregon -----------------

4.3 

4.0 

4.7 

4.0 

PLIOCENE-QUATERNARY OLIVINE BASALT 

10-15--17---------

11-17-18---------· 

Rieff volcano. Prineville, Oreg______________ 1.8 

MS-4------------· 

Conant butte, Post, Oreg ___________ .________ .7 

Ochoco State Park, Prineville, Oreg________ .6 7a ___________ _ Quarry, 1 mile south of Madras, Oreg______ .4 

CLARNO FORMATION 

10-i3-17 ---------· Andesite, Oregon -------------------------- 0.5 26-17-18---------· Basaltic andesite, Newsom Creek, Oreg_____ .6 

JOHN DAY FORMATION 

31-15-18---------· 

1-16-17 ----------· 28-12-18---------· 

Rhyolite, Bursa Road, Oreg________________ 0.5 Perlite, Eagle Creek, Oreg_________________ .4 

Dacite, Ochoco Reservoir q~adrangle, Oreg__ .3 

TABLE 29.-Distribution of gold in basalts of the Snake River 

Group and associated rhyolitic rocks, Idaho 

[Samples supplied by H. A. Powers, U.S. Geol. Survey) 

Sample No. 

54P-3-------- 4 _______ _ 

5--------· 

23-------· 55P-42-------· 

54P-6B-------· 61_ ______ , 

65-------· 55P-275 ______ _ 

235------· 236 ______ , 

237 ------· W JC167-58 ___ _ WJC148-58 ___ _ 

GF51-57 ------ OB9-57 ------- PV67-57 ------ OB32-57 ------ CP40-57 ------· 

Rock type 

Basalts 

____ 

Basalt do ____________ ------------_ ____ do ____________ _ ____ do ____________ _ ____ do ____________ _ 

Olivine basalt ----- ____ do ____________ _ ____ do ____________ _ _ ___ do ____________ _ ____ do ____________ _ ____ do ____________ _ 

Plagioclase basalt--

Olivine basalt ----- _ ___ do ____________ _ ____ do ____________ _ 

Basalt ------------ ____ do ____________ _ 

Alkaline basalt_ ___ _ ____ do ____________ _ 

Location 

Near Tuana gulch _______ _ 

Clear Lake Springs -------

Near 

____ do Buhl ___________________ ---------------_ 

Thousand Springs --------

Wendell ----------------- Near Bliss --------------- Sand Springs ranch ______ _ 

Malad Spring ------------ Near Owsley Bridge ______ _ _ ___ do ___________________ _ ____ do ___________________ _ 

American Falls powerhouse_ 

Near Rockland ----------- Alkali Creek ------------- Clover -Creek ------------- _ ___ do ___________________ _ 

King Hill ---------------- ----dO--------------------

Au 

(ppb) 

0.9 

.2 

1.3 

.9 

.3 

.2 

.4 

.1 

.6 

.5 

1.1 

.2 

.4 

.4 

.1 

.3 

.2 

.5 

.2 

TABLE 29.-Distribution of gold in basalts of the Snake River 

Group and associated rhyolitic rocks, Idaho-Continued 

Sample No. 

53P-5B-------· 81 ______ _ 

85 _______ , 

54P-10B------· 125 _____ .;., 

58P-147 ------· 

Rock type Loca~ion 

Au 

(ppb) 

Rhyolites 

Porphyritic rhyolite Obsidian tuff _____ _ _ ___ do ____________ _ 

Rhyolite tuff ______ _ ____ do ____________ _ 

Pumice scoria -----

Elmore County ----------- 0.6 Twin Falls County-------- .2 _ ___ do-------------------- .2 

South of Murphy --------- .4 West of Oakley ---------- 1.2 West of Carey ----------- 1.1 

TABLE 30.-Distribution of gold and copper in the Greenstone 

Flow (1,300 feet thick) of the Michigan copper district 

[Samples supplied by H. R. Cornwall, U.S. Geol. Survey] 

Sample No. 

3132 _________ _ 3134 _________ _ 

3138 _________ _ 3140 _________ _ 3142 _________ _ 

G-297 -------- 3144_ ________ _ 

G-26 _______ .;._ 3150 _________ _ 3152 _________ _ 

3154_ ________ _ 

Depth, 

in feet, 

below 

surface 

of flow 

118 

215 

315 

245 

387 

422 

501 

800 

941 

1,085 

1,228 

Rock type 

____ 

Basalt do _________________ ----------------_ 

·---dO------------------

Pegmatite ------------- Basalt ----------------- Pegmatite ------------- Basalt ---------------- Granophyre ----------- Basalt ---------------- ·---dO------------------

____ do _________________ _ 

1 K. J. Murata, analyst (Cornwall and Rose, 1957). 

Cu (ppm)1 

90 

100 

83 

210 

110 

100 

110 

60 

72 

80 

110 

Au 

(ppb) 

1.4 

14.4 

3.9 

3.5 

2.9 

7.6 

2.9 

8.5 

5.5 

1.8 

7.0 

TABLE 31.-Distribution of gold in basalt and diabase from 

the Triassic basin, Eastern United States 

Sample 

No. Rock Location 

Connecticut 

[Samples supplied by P. M. Hanshaw and C. E. Fritts, U.S. Geol. Survey] 

Au 

(ppb) 

E2395__________ Diabase -------------- East Roc~ road ------- 3.0 E2200__________ _ ___ do________________ West Cheshire -------- 2.6 E239L--------- ____ do________________ Pine Rock, New Haven 2.7 County. 

E2277 ---------- Talcott Basalt -------- Sunset Rock Park______ 4.3 E227 !__________ _ ___ do________________ Near Farmington ----- 2.0 

E2279__________ Basalt --------------- State Route 72, at U.S. 3.2 5. E2272__________ Holyoke Basalt ------ Near Farmington ----- 1.4 E2398__________ Hampden Basalt ----- Quarry, Bradford ----- 2.9 

E2274__________ Holyoke Basalt ------ Quarry 4, New Haven 1.3 County. 

E227 5---------- ----dO---------------- ----dO----------------- 1.0 E2270__________ Basalt dike ---------- Near River Glen ------ 3.1 E2396__________ Diabase -------------- Barone quarry, · New 3.4 Haven County. 

E2276__________ Hampden Basalt ----- Stanley Quarter Park__ 3.7 

E2397 ---------- Basalt --------------- Quarry near North 1.1 Branford. 

WC2-2---------· Diabase -------------- Connecticut River basin_ 4.2 WC9-1---------· ____ do________________ _ ___ do_________________ 1.7 

New Jersey 

[Samples supplied by G. T. Faust, U.S. Geol. Survey] 

1-B-20--------- 2-B-30 ________ _ 

3-BT-2--------· 4-BT-5 ________ _ 5-B-2 _________ _ 

6-B------------

7-B-13---------

8-B-17 --------- 9-C-2----------· 10-C-6 _________ _ 

11-M-1-AAAA __ 

12-M-1-M------

13-ML-2-------· 

14-ML-4-------· 

15-ML-10------· 

16-ML-28------· 

17-ML-48------· 

18-ML-64------· 

19-ML-69------· 

20-ML-86------· 

21-ML-98------· 

22--ML-112-----· 

23-ML-122-----· 

24-ML-146-----· 

Watchung Basalt ---- ____ do _______________ _ 

____ do _______________ _ _ ___ do _______________ _ 

____ do _______________ _ 

----dO-----------------

----dO----------------

____ do _______________ _ 

____ do _______________ _ ____ do _______________ _ ____ do _______________ _ 

____ do---------------- ____ do _______________ _ 

____ dO----------------

----dO----------------

____ do _______________ _ ____ do _______________ _ ____ do _______________ _ ____ do _______________ _ ____ do _______________ _ ____ do _______________ _ 

____ do _______________ _ ____ do _______________ _ 

----dO----------------

Somerset County ------

----dO-----------------

____ do ________________ _ _ ___ do ________________ _ 

_ ___ do ________________ _ ____ do ________________ _ ____ do ________________ _ ____ do ________________ _ ____ do ________________ _ 

----dO-----------------

_ ___ do ________________ _ 

____ do ________________ _ 

----dO-----------------

____ do ________________ _ ____ do ________________ _ 

____ do----------------- _ ___ do ________________ _ ____ do ________________ _ ____ do ________________ _ _ ___ do ________________ _ _ ___ do ________________ _ ____ do ________________ _ ____ do ________________ _ 

____ do-----------------

2.7 

3.8 

2.8 

3.5 

6.0 

5..9 

4.8 

4.2 

3.7 

4.2 

4.0 

4.0 

3.7 

4.0 

4.4 

4.1 

9.6 

7.0 

4.5 

5.6 

4.9 

5.2 

23.1 

5.8 
TABLES 39 

TABLE 31.-Distribution of gold in basalt and diabase from 

the Triassic basin, Eastern United States-Continued 

Sample 

No. Rock Location 

Au 

(ppb) 

Pennsylvania 

[Dillsburg samples supplied by P. ·E. Hotz, U.S. Geol. Survey; Cornwall 

samples, by. D. M. Lapham, Pennsylvania Geol. Survey; other samples 

by A. W. Rose and R. C. Smith, Pennsylvania State Univ. Locahty: 

D.D.H., diamond drill hole] 

1 888-----------· 

1 400-----------· 2 465-----------· 

3 645-----------· 

3 560-----------· 

4 601-----------· ss ____________ _ 

C2-7 -----------· 

C-18-----------· 

19-----------

28 __________ _ 

88-----------

40 __________ _ 

40P ----------

C4-212---------· 

22L _______ _ 

5-----------

II-38-G--------· 

D-7 ------------

10 __________ _ 

13 __________ _ 

15-----------

84 __________ _ 

46 __________ _ 

7 5 __________ _ 

79 __________ _ 

89 __ ..; _______ _ 

Diabase with coarse network. 

Normal diabase ------ Pegmatitic facies ---- Granophyric diabase --

Granophyre ---------- ----dO----------------

6-ft diabase dike, 1 ft 

from contact. 

Diabase dike, chilled 

margin. 

Diabase pegmatite, 300 

ft below top of sheet. 

Normal diabase, 433 ft 

below top of sheet. 

Altered normal diabase 

adjacent to an ore vein containing mag- netite, chlorite, and 

actinolite, 688 ft below top of sheet. 

Porphyritic diabase, 

1,020 ft below top 

and 10 ft above base 

of sheet. 

Normal diabase, 7 5 ft 

below top of sheet. 

Diabase pegmatite, near sample C-40. 

Normal diabase, 

approximately 50 ft 

below top of sheet. 

Normal diabase, 

approximately 450 ft 

below top of sheet. 

Granophyre vein in 

diabase 10 ft below 

top of the diabase 

sheet. 

Granophyre ----------

Diabase, 3-4 ft from upper contact. Diabase, 3-4 ft from 

lower contact. Diabase dike. <5 ft 

from contact. Diabase, 2 ft from 

lower contact. 

Diabase, llz-1 ft from 

lower contact. Diabase, 4-6 ft from upper contact. Diabase dike, 3-6 ft 

from contact. 

Diabase, 3 ft from upper contact. Diabase, lower third 

of sheet. 

Virginia 

Dillsburg, drill hole D-3 8.5 

____ do_________________ 22.6 

____ do----------------- 12.2 ____ dO----------------- 19.6 ____ do _____ ;.___________ 13.7 

____ do_________________ 9.0 

Sinking Springs quad- 1.6 

rangle, Cornwall district. 

Open pit of western 8.1 ore. body, Cornwall 

district. D.D.H. 155, Cornwall 2.0 

district. ____ do_________________ 2.3 

____ dO----------------- .4 

____ dO----------------- 2.0 

____ do----------------- 2.8 

____ do----------------- 5.5 

D.D.H. 1225-2, eastern 2.1 ore body, Cornwall 

district. ____ do_________________ 1.8 

945 level of eastern ore 2.0 

body, Cornwall district. 

Shaft of the western ore . 7 body, Cornwall district. 

East of Heidlersburg, 2.5 

U.S. Route 15. 

----dO----------------- 2.4 

South of Gettysburg, 1.9 

U.S. Route 15. 

Roadcut, U.S. Route 15, 1.7 

north of Pennsylvania. 

Maryland line. 

mile west of Eliza- 4.1 

beth town. 2 miles north of Bow- 4.0 

mansville. 

Safe Harbor quarry, 3.0 

southeast of Safe 

Harbor. 

Grace mine, 5th level, 2.5 

Morgantown. 

Reesers Summit ------- 7.2 

[Samples supplied by E. C. T. Chao, U.S. Geol. Survey) 

MQ1236--------· 

MQ63----------· 

MQ145-----~---· 

MQ197 FQ24 __________ ---------· _ 

MQ813A _______ _ 

MQ317 ---------· MQ120---------· 

MQ372---------· MQ197a _______ _ 

MQ198---------· 

MQ918---------· MQ197b ________ . 

MQ197c ________ . MQ635A _______ _ 

HS20-H-12H ___ . 

Diabase (essentially 

clinopyroxene and 

labradorite). ____ dO---------------- ____ do _______________ _ 

____ do----------------

----dO----------------

____ do _______________ _ 

____ dO----------------

Granophyric diabase 

(has less calcic 

plagioclase, amphibole, and quartz) . 

____ do----------------

----dO----------------

____ do _______________ _ 

----dO----------------

Granophyre (chiefly 

albitic plagioclase, 

amphibole, and 

quartz). ____ do _______________ _ ____ do _______________ _ 

____ do _______________ _ 

Fairfax County -------

____ do ________________ _ 

----dO-----------------

----dO-----------------

_ ___ do ________________ _ _ ___ do ________________ _ 

____ do ________________ _ 

____ do-----------------

____ do ________________ _ 

_ ___ do ________________ _ ____ do ________________ _ 

____ do ________________ _ ____ do ________________ _ 

____ d(> ________________ _ 

____ 

----dO----------------- do ________________ _ 

3.7 

2.4 

1.9 

2.6 

.3 

1.5 

3.7 

2.4 

6.5 

2.3 

2.4 

2.2 

1.1 

1.4 

3.8 

1.5 

TABLE 31.-Distribution of gold in basalt and diabase from 

the Triassic basin, Eastern United States-Continu~d 

Sample 

No. Rock 

North Carolina 

Location 

Au 

(ppb) 

[Samples supplied by P. C. Ragland, Univ. of North Carolina] 

BP-L--~-------

D8R-1---------· 

Du6-1----------

JY -1-----------

NC30-L-------· 

RD-1----------· 

107-ft low K20 diabase 

dike, 1 ft from contact. 47-ft low K20 diabase 

dike, 3 ft from contact. 6-ft low K20 diabase 

dike, 0.5 ft from contact. ,_.60-ft diabase dike, at contact. ,_.80-ft low K20 

diabase dike, 1 ft 

from contact. 

Deep River basin -----

____ do ________________ _ 

____ do-----------------

____ do ________________ _ 

____ dO-----------------

____ dO-----------------

4.5 

6.9 

3.6 

3.8 

7.9 

RS-1-----------

10-ft low K20 diabase 

dike, at contact. 9-ft low K20 diabase 

dike, 0.5 ft from contact. 

____ do ________________ _ 

2.7 

3.2 

South Carolina 

[Samples supplied by David Gottfried and Henry Bell, III, 

U.S. Geol. Survey) 

69G-4--------·-- 1,000-ft diabase dike, Northeast of Kershaw__ 2.2 near northeast contact zone. 5---------- Same dike, 300 ft from ____ do----------------- 2.3 

northeast contact. 6---------- Same dike, 600 ft from ____ do_________________ 2.6 

northeast contact. 7---------- Same dike, near south- ____ dO----------------- 3.2 west contact zone. 

1 Copper value is 150 ppm, 2 Copper value is 200 ppm. a Copper value is 250 ppm. 4 Copper value is 400 ppm, 

TABLE 32.-Distribution of gold in Precambrian diabase 

intrusions, Iron County, Mo. 

[Samples supplied by G. A. Desborough, U.S. Geol. Survey. 

Altered samples indicated by an asterisk ( •)] 

Shepherd Mountain intrusion 160-foot sill 

Sample depth Au Sample Feet above Au 

(feet) (ppb) No. base of sill (ppb) 

1,715* 0.5 2 5 7.4 

1.760 1.2 3* 7 .5 

1,775 1.4 5 42 3.1 

1,790 1.6 6* 44% 2.2 

1,810 1.8 s• 50 3.2 

1,822 5.7 9 89¥.! 1.7 

1,845 2.2 10 100 3.3 

1,862 2.0 12 118 3.8 

1,876 1.5 15* 140 .8 

1,923 3.5 16* 143 1.2· 

1,943 3.1 17 146 .6 

1.970 1.9 18 154 .7 

2,009 2.6 

TABLE 33.-Distribution of gold and copper in the 

Great Lake intrusion, Tasmania 

Depth, in feet 

below surface, 

drill core of 5123 

Granophyres 

10 --------------------------------------- 60 

100 

200 

300 

400 

460 

600 

550 

600 

700 

Central-zone dolerites 

Cu (ppm)l Au (ppb) 2 

44 1.4 77 1.0 

165 8.1 

130 1.2 

130 4.6 

155 5.0 

i7o 5.2 9.3 

12.0 

120 11.9 

79 6.2 
40 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE 33.-Distribution of gold and copper in the 

Great Lake intrusion, 2'asmania---Continued 

Depth, in feet 

below surface, 

drill core of 5123 

800 

900 

1,000 

1,200 

1,400 

1,500 

1,735 

Lower zone dolerites 

Chilled margin 

Cu (ppm) 1 

93 

60 

49 

42 

37 

44 

48 

Au (ppb) 2 

4.2 

3.4 

4.1 

3.5 

2.7 

2.4 

5.2 

(3) --------------------------------------- 75 7.3 

1 Data from Greenland and Lovering (1966). 2 Data from Rowe (1969). 3 Sample is from 1 foot above lower contact of drill core 5084. 

TABLE 34.-Distribution of gold in volcanic rocks of the 

liVestern Cascades, Oreg. 

[Samples supplied by D. L. Peck, U.S. Geol. Survey] 

Sample No. Rock type Au (ppb) 

Little Butte Volcanic Series (Oligocene and Miocene) 

P-55-9-14F ------ 16A _____ _ 

DLP-56-146 _____ _ 204_ ____ _ 27 ______ _ 65 ______ _ 

202 _____ _ ABG-54-55 ______ _ DLP-56-133 _____ _ 

17------- ABG-94-55 ______ _ DLP-56-82 ______ _ 128A ____ , 67-55 ______ _ 

Olivine basalt flow ------------------------ ----dO-------------------------------------

----dO-------------------------------------

Hypersthene andesite ---------------------- Basaltic andesite ------------------------- Dacite welded tuff ------------------------ Dacite plug ------------------------------- Vitric dacite welded tuff ------------------ Rhyodacite flow --------------------------- Rhyodacite welded tuff -------------------- ____ dO------------------------------------- ----dO-------------------------------------

5.3 

3.3 

5.0 

4.8 

2.8 

10.7 

3.8 

1.1 

1.1 

.6 

.8 

1.1 

.9 

1.4 

Sardine Formation (lower and middle Miocene) 

P-55-8-19D ______ , DLP-56-l15 _____ _ P-55-6-25G ______ , 29A _____ _ 

8-31A ______ , 7-28A _____ _ 

DLP-56-L-------

Basaltic andesite ------------------------- Olivine andesite --------------------------- Hypersthene andesite ---------------------- ----dO-------------------------------------

Labradorite andesite ---------------------- Hypersthene andesite ---------------------- Andesitic tuff -----------------------------

1.5 

.8 

1.0 

.6 

1.1 

7.0 

11.0 

TABLE 35.-Distribution of gold in volcanic rocks of the 

Southern High Cascades, Calif., and vicinity 

[Samples supplied by A. L. Smith and I. S. E. Carmichael, Univ. of 

California, and A. T. Anderson and David Gottfried, U.S. Geol. Survey] 

Sample No. 

242 __________ _ 235 _________ _:_ 

237----------- 72 ___________ _ 70 __ :._ ________ _ 

2 1------------- ____________ _ 

3------------- 6A __________ _ 

SA 7------------- __________ _ 

15A---------- 200 __________ _ 

187-----------

196 __________ _ 

199 __________ _ GM __________ _ 

GM-P -------- LGM ________ _ 

LGM-P -------

Cal 20 _______ _ 

Cal 24 _______ _ 

Cal 25 _______ _ 

Rock type Au (ppb) 

Mount Shasta 

Olivine basalt, cinder cone ------------------- 11.6 

Pyroxene andesite ---------------------------- 6.6 

---- do -------------------------------------- 4.3 ---- do -------------------------------------- 12.0 

Hornblende andesite -------------------------- 9.1 

Medicine Lake Highland 

Warner Basalt of Russell (1928), Gillems Bluff__ 3.5 

do -------------------------------------- 1.9 

do -------------------------------------- 3.3 

do -------------------------------------- 2.2 do -------------------------------------- 4.9 

do -------------------------------------- 6.2 ---- do -------------------------------------- 2.5 

Olivine basalt, latest flow in Modoc Basalt of 2.2 

Powers (1932). 

Olivine basalt, Paint Pot Crater Flow of Ander- .8 son (1941). 

Olivine basalt, Callahan Flow as used by Ander- .6 son (1941). 

Basaltic andesite, Schonchin flow ------------- 4.7 

Rhyolitic obsidian, G'ass Mountain ------------ .5 

Rhyolitic pumice, Glass Mountain ------------- .4 

Rhyolitic obsidian, Little Glass Mountain·------ .4 

Rhyolitic pumice, Little Glass Mountain ------- .5 

Lassen area 

Quartz basalt, near vent of 1851 flow, Cinder 1.5 

Cone, Lassen National Park. 

Quartz basalt, Cinder Cone,· Lassen National 14.1 

Park. 

Quartz basalt, pre-1851 flow near Butte Lake, 19.4 

Cinder Cone, Lassen National Park. 

TABLE 35.-Distribution of gold in volcanic rocks of the 

Southern High Cascades, Calif., and vicinity-Continued 

Sample No. Rock type Au (ppb) 

Lassen area-Continued 

Cal 43 _______ _ Quartz basalt, recent flow, West Prospect Peak, 12.7 Lassen National Park. 

3------------- 63 ___________ _ Basaltic andesite, Red Lake Mountain -------- 7.0 

Olivine basalt, Hat Creek Basalt of Anderson 4.6 

(1940). 

TABLE 36.-Distribution of gold in some rhyolites from 

Mono County, Calif. 

[Samples supplied by Irving Friedman, U.S. Geol. Survey] 

Sample No. 

3-65K ___________ _ 4-65K ___________ _ 

ll-65K-----------

13-65K----------- 14-65K __________ _ 

9-65K------------ 15-65K __________ _ 

20D-65K---------

Rock type Au (ppb) 

Porphyritic rhyolite ----------------------- 0.4 ----dO------------------------------------- .1 

Rhyolitic glass ---------------------------- 1.9 ----dO------------------------------------- .6 Obsidian----------------------------------- .3 ----dO------------------------------------- .2 Porphyritic rhyolite ----------------------- .2 

Porphyritic rhyolite glass ----------------- .1 

TABLE 37.-Distribution of gold in volcanic rocks of the 

Jemez Mountains, N. Mex. 

[Samples supplied by R. L. Smith, R. A. Bailey, and David Gottfried, 

U.S. Geol. Survey] 

Sample No. 

52-167L---------

166B---------- 53-1758 _________ _ 

62-1667---------- 63-1750 _________ _ 

1672 _________ _ A-59 ____________ _ 60 ____________ _ 64 ___________ . __ 

C-558------------

A-61------------- 62 ____________ _ 

3149-7----------- g __________ _ g __________ _ 

3 __________ _ 

Rock type and age or location Au (ppb) 

BASALTIC ROCKS 

Basalt, Pliocene -------------------------- 2.3 ----dO------------------------------------- 3. 9 

6.1 

Olivine basalt, Pliocene ------------------- 2.9 ----dO------------------------------------- 1. 7 ----dO------------------------------------- 2.1 

1.8 

2.6 ----dO------------------------------------- 1. 7 

1.3 

Olivine basalt, Pliocene-Pleistocene -------- 2.2 

----dO------------------------------------- 1.9 

PRECALDERA SILICIC VOLCANICS 

Quartz latite, Santa Clara Canyon --------

Rhyodacite, Ruiz Peak -------------------- Quartz latite, Bear Spring area ------------ Rhyolite, Bear Head ----------------------

0.3 

.3 

.1 

.1 

-----------------------------

J-1-432---------- 325 _________ _ 260 _________ _ 

230---------- 205 _________ _ 

M-1-0-6---------· 10-10.6 ______ _ S-1 _________ _ 

RHYOLITES OF BANDELIER TUFF 

Tshirege Member 

Ash flow, 230 ft above base --------------- 1.6 

Ash flow, 120 ft above base --------------- 1.0 

Ash flow, 56 ft above base ---------------- .6 Ash flow, 25 ft above base----------------- 1.0 

Air-fall pumice from base of section ------- .9 

Air-fall pumice --------------------------- . 7 ----dO------------------------------------- 1.0 ----dO------------------------------------- . 7 

Otowi Member 

------------ -------------------------- J-1-634---------- 594 _________ _ 

634---------- 394 _________ _ 274 _________ _ 114 _________ _ 

P-21-8 ____ :_ _____ _ 

20----------

Ash flow, 520 ft above base ---------------- Ash flow, 480 ft above base ---------------- Ash flow, 420 ft above base ---------------- Ash flow, 280 ft above base ---------------- Pumice, 160 ft above base ----------------- Pumice from base of section -------------- Air-fall pumice ---------------------------

----dO-------------------------------------

POSTCALDERA SILICIC VOLCANICS 

3149-L----------

2----------- 10 _________ _ 

JS64-2 __________ _ 

3149-1L---------

JS64-42---------- 52 _________ _ 

6a _________ _ 

60-LP -----------· SC67-7V --------- SC64-9 __________ _ 

3149-4-----------· 

s 5----------- __________ _ 

Quartz latite, Sawyer dome ---------------- Rhyolite, South Mountain ----------------- Rhyolite, San Antonio dome ---------------

----dO-------------------------------------

Rhyolite, Water Canyon ------------------ Rhyolite, Seco dome ----------------------- Rhyolite, San Luis dome ------------------ Rhyolite, Santa Rosa dome ---------------- Rhyolitic obsidian, Abrigo ---------------- Quartz latite, Cerro Rubio ---------------- Quartz latite, Pinnacle Peak -------------- Rhyolitic pumice, Battleship Rock ---------

Rhyolite, Banco Bonito ------------------- Rhyolitic pumice, El Cajete ----------------

0.4 

.7 

.7 

.5 

.6 

.4 

.7 

.6 

0.2 

.3 

.7 

.3 

.2 

.2 

.3 

·.6 

.5 

.4 

.3 

.6 

.6 

.7 
;;. 

l 

1 I 

TABLES 41 

TABLE 38.-Distribution of gold in volcanic rocks from 

Yellowstone National Park, Wyo., and vicinity 

[Samples supplied by L. P. Muffler, Warren Hamilton, and David Gottfried, U.S. Geol. Survey] 

Sample No. Rock type and location Au (ppb) 

G-YP-1_ ----------------------------------------------------- ________ _ 2 _________ _ 

3---------- 5 _________ _ 

5A--------· 

YP-A2 6---------.-__________ _ 

A1-----~-----

A3----------- YS-4------------· 

8 20A---------- ____________ _ 

24 ___________ _ 

26A _________ _ 

7 A-2--------- G-YP-4A--------· 4B--------· 

7----------

Rhyolite, Firehole Falls --------------------- Rhyolite, Midway Geyser basin --------------

Obsidian, Obsidian Cliff --------------------- Rhyolite tuff, Golden Gate Canyon ----------- Rhyolite tuff, below sample G-YP-5 ---------

Rhyolite tuff, Wraith Falls ------------------ Rhyolite tuff, Mount Everts -----------------

Obsidian, Reas Pass ------------------------ Perlite, Midway Geyser basin ---------------- Rhyolite tuff, Cougar Creek ----------------- Rhyolite tuff, West Yellowstone -------------

---- do ------------------------------------- ---- do ------------------------------------- Rhyolite, West Yellowstone ------------------ Obsidian, West Yellowstone ------------------ Basalt; Sheepeater Cliffs ---------------------

---- do ------------------------------------- Basalt. Undine Falls ------------------------

0.1 

.1 

.2 

.3 

.8 

.2 

.4 

.4 

.2 

1.3 

.4 

.5 

.4 

1.0 

1.5 

.2 

.2 

.2 

TABLE 39.-Distribution of gold in metamorphosed 

Precambrian silicic volcanic rocks in central Arizona 

[Samples supplied by C. A. Anderson, U.S. Geol. Survey] 

Sample No. Rock type Au (ppb) 

1 

2 

4 

5 

7 

8 

11 

12 

13 

14 

15 

16 

17 

18 

19 

Ash Creek Group 

Deception rhyolite -------------------------------- ---- do ------------------------------------------ Buzzard rhyolite (chloritized) -------~------------

---- do ------------------------------------------ Deception rhyolite --------------------------------

---- do ------------------------------------------

Alder Group 

Rhyolite, Green Gulch Volcanics 1 ------------------

---- do ------------------------------------------ Rhyolitic tuff, Spud Mountain Volcanics 1 ----------

---- do ------------------------------------------ Rhyolite tuff, Texas Gulch Formation 1 _____ ,.; ______ _ 

Rhyolite, Iron King Volcanics 1 __ .:_ ________________ _ 

Rhyolitic tuff ------------------------------------- Rhyolite, Spud Mountain Volcanics 1 -------..,------

Intrusive rhyolite, Spud Mountain Volcanics 1 ______ _ 

1.0 

.4 

12.4 

10.7 

1.0 

7.0 

0.9 

.2 

.2 

.2 

.2 

.5 

.2 

8.3 

3.4 

Quartz porp_h_y_r_Y ________________________ _ 

I Quartz porphyry --------------------------------- 7.4 

II ---- do ------------------------------------------ 1.0 III ---- do ------------------------------------------ 1.9 

V Quartz porphyry (foliated) ----------------------- 3.6 

VI ---- do ------------------------------------------ .5 

1 Formerly considered to be in Alder Group. 

TABLE 40.-Distribution of gold in volcanic rocks· from 

the Beatty area, Nevada 

[Samples supplied by H. R. Cornwall, U.S. Geol. Survey] 

Sample No. 

BC-100---------- 149----------· 72b _________ _ 

MC-170a 72C----------· ________ _ 170b ________ _ 170c ________ _ 295 _________ _ BC-148 __________ _ 

MC-21L---------

MC-27 4a ________ _ 274b ________ _ 

27 4c ________ _ 299 _________ _ 

336 _________ _ 

17 5---------- 27 fi _________ _ 

297----------

Rock type Au (ppb) 

Bullfrog Hills caldera 

------------------------- Lithoidal welded tuff ----------------------

____ dO------------------------------------- Basal glass zone of rhyolite flow ---------- Felsitic zone of rhyolite flow BC-72b ------

Zeolitized tuff ---------------------------- Basal glass zone of flow ------------------- Felsitic zone of rhyolite flow MC-170b ___ _ Glass zone of rhyolite flow or intrusive ___ _ 

Porphyritic latite flow --------------------

Basalt flow -------------------------------

Yucca Mountains caldera 

0.5 

.2 

.2 

.3 22.0 

2.0 

9.2 

.9 

.5 

1.8 

Zeolitized basal tuff of welded tuff -------- 1.1 Basal glass zone of welded tuff ------------ 3.4 Lithoidal welded tuff --------------------- 1.5 Basal glass zone of welded tuff. ------------ 1.4 Glassy zone of intrusive rhyolite ---------- .3 

Rhyolite stock ---------------------------- 3.9 

Rhyodacite dike, upper Tertiary(?) -------- .8 

Recent basalt flow ------------------------ 1.7 

TABLE 41.-Distribution of gold in some samples of the 

Challis Volcanics, central Idaho 

[Samples supplied by B. F. Leonard, U.S. Geol. Survey] 

Sample No. 

y -54-565 ________ _ 582 ________ _ 

597--------- 598 ________ _ 

L-62-2150 _______ _ 64-2639 _______ _ 61-106 ________ _ 229 ________ _ 

y -54-599 ________ _ 599A ______ _ H-54-63 _________ _ 

Rock type Au (ppb) 

Andesite ---------------------------------- ----dO--------------------------------'-----

Andesite tuff ------------------------------

Dacite ------------------------------------ Latite ------------------------------------ Latite tuff -------------------------------- Rhyolite ---------------------------------- Rhyolite tuff ------------------------------ ____ do------------------------------------- ____ do-------------------------------------

Rhyolite ----------------------------------

0.3 

1.0 

.4 

.5 

.9 

1.0 

.6 

.3 

1.0 

1.7 

.4 

TABLE 42.-Distribution of gold in some calc-alkalic metavolcanic rocks from the southern Appalachians, North 

Carolina and Virginia 

[Samples supplied by D. W. Rankin and A. A. Stromquist, U.S. Geol. Survey] 

Sample No. 

1--------------- 2 ______________ _ 6 ______________ _ 

3--------------- 4 _______________ , 

5--------------- 11---------------

R-PN1-8 ________ _ 

WS3-2--------· 

WS4-17 -------· WS1-8--------· 

PN2-5L------- PN 4-13 _______ _ 

WC2-17 -------· WS1-5L------· 

66-------· 

Rock type 

Denton quadrangle, North Carolina 

Andesitic tuff breccia --------------------- 1.9 ----dO------------------------------------- .5 ----dO------------------------------------- .8 Rhyolitic flow ----------------------------- .5 Rhyolitic tuff ----------------------------- .6 ----dO------------------------------------- .4 Rhyolitic vitrophyre ----------------------- .9 

Mount Rogers Formation, Virginia 

Porphyritic rhyolite ----------------------- 0.1 ----dO------------------------------------- 2.8 .3 

Porphyritic rhyolite dike ------------------ .4 Phenocryst-poor rhyolite ------------------ .1 _ ___ do------------------------------------- .2 ----dO------------------------------------- .3 ____ do------------------------------------- .5 ----dO------------------------------------- .2 

TABLE 43.-Distribution of gold in alkalic igneous rocks from 

Big Bend National Park, Tex. 

[Samples supplied by J. T. Lonsdale, Univ. of Texas] 

Sample No. 

Ch-1------------- 243-D-------- 84Q-B _______ _ 

589----------- 386 __________ _ 

148-----------

724----------- 727-D _______ _ 

69-D---------· 

179----------- 47-A ________ _ 

i76-A--------

258----------· 

726-F --------· 47-B---------· 

577-B-------- 747-C ________ , 61-B ________ _ 

34Q-B--------· 

668-F --------· 767-A-3 _____ _ 

746-F --------· 162-B--------· 

232-D--------· 

203----------- 234 __________ _ 

687-F-2------· 

Rock type Au (ppb) 

Porphyritic olivine basalt ----------------- 0.5 Nepheline basalt, intrusive ---------------- .9 

Basalt, intrusive -------------------------- .5 Porphyritic olivine basalt, extrusive -------- .8 

Olivine basalt, intrusive ------------------- 4.3 

----dO------------------------------------- .6 

Porphyritic olivine basalt, intrusive ------- .3 Basalt porphyry, extrusive ---------------- .5 Analcite labradorite syenite --------------- .4 Analcite syenogabbro --------------------- .5 Syenogabbro, intrusive -------------------- .4 Analcite an~esine syenite, intrusive ------- 1.0 Olivine syenodiorite, intrusive ------------- 1.0 Trachyandesite, extrusive ----------------- .4 Analcite syenite, intrusive ---------------- .2 Trachyandesite porphyry, extrusive -------- .4 ____ do------------------------------------- .6 Augite soda trachyte, intrusive ------------ .2 Aegerine augite trachyte, intrusive -------- .4 Riebeckite trachyte, extrusive ------------- 1.9 

Pyroxene microgranite, intrusive ---------- .3 Riebeckite rhyolite, extrusive -------------- .4 Riebeckite granite, intrusive -------------- .4 Riebeckite granophyre, intrusive ---------- .2 Riebeckite microgranite porphyry --------- .8 Riebeckite granophyre, intrusive -'--------- 1.2 Quartz sanidine porphyry, intrusive ------- .4 

TABLE 44.-Distribution of gold in subsilicic alkalic rocks 

from central Montana 

[Samples supplied by W. T. Pecora and E. S. Larsen, Jr., U.S. Geol. Survey] 

Sample No. Rock type Au (ppb) 

Boxelder laccolith, Bearpaw Mountains 

83P ---------- Pegmatitic patch in syenite ---------------- 1.4 64 __________ _ Q ___________ _ Aplite dike in syenite ---------------------- 1.4 Syenite (summit), 360 ft above base -------- .4 
42 DISTRIBUTION OF GOLD IN IGNEOUS ROCKS 

TABLE 44.-Distribution of gold in subsilicic alkalic rocks 

from central Montana-Continued 

Sample No. Rock type Au (ppb) 

Boxelder laccolith, Bearpaw Mountains--Continued 

81-----------· 83 __________ _ 

63-----------· 49 __________ _ 

48 ___________ , 

45-----------· 33 ___________ , 58 ___________ , 

Syenite, 335 ft above base ------------------ Syenite, 300 ft above base ------------------ Mafic syenite, 210 ft above base ------------ Friable· shonkinite, 90 ft above base -------- Basal shonkinite, 70 ft above base ---------- Basal shonkinite, 25 ft above base ----------

Hard shonkinite, basal zone ---------------- ----dO-------------------------------------

Shonkin Sag laccolith, Highwood Mountains 

2L__________ Upper shonkinite -------------------------- 450----------· ----dO-------------------------------------

2.9 

1.1 

2.7 

6.1 

3.6 

4.0 

2.4 

4.1 

2.4 

.5 

TABLE 44.-Distribution of gold in subsilicic alkalic rocks 

from central M ontanar--Continued 

Sample No. Rock type Au (ppb) 

Shonkin Sag laccolith, Highwood MGuntains-Continued 

15 ___________ , 

1044---------· 

1067 ---------· 1065 _________ , 

1066---------· 

A1-----------

A------------ 451 __________ , 

B------------

1008---------· 

415----------· 

108L--------· 

~~~~~e -;;;~it;-::::::::::::::::::::::::::: ----dO-------------------------------------

Minette (3 in. thick) ---------------------- Aplitic syenite ---------------------------- Transition rock ---------------------------- ----dO-------------------------------------

----dO-------------------------------------

Lower shonkinite -------------------------- ----dO-------------------------------------

Mafic phonolite ---------------------------- Basal mafic phonolite, next to contact with 

sandstone. 

U. S. GOVERNMENT PRINTING OFFICE : 1972 0 - 443-785 

2.8 

3.2 

5.1 

2.0 

3.8 

.7 

.7 

2.3 

6.7 

6.7 

1.6 

10.4