Report No.dggs.alaska.gov/webpubs/mirl/report_no/text/mirl_n45.pdf"true fineness" which is the ratio of gold to gold plus silver multiplied by 1000 (Boyle, 1979, p. 197). Note that

M I R L R e p o r t No. 4 5

A SUMMARY OF GOLD FINENESS VALUES FROM ALASKA PLACER DEPOSITS

Paul A. Metz Mineral Industry Research Laboratory

and

D. B. Hawkins Geology/Geophysics

School of Mineral Industry University of Alaska

Fairbanks, Alaska 99701

March, 1981

TABLE OF CONTENTS

Page

Table of Contents . . . . . . . . . . . . . . . . . . . . . i

Figures. . . . . . . . . . . . . . . . . . . . . . . . . i

Tables and Plates . . . . . . . . . . . . . . . , . . . . . iii Abstract . , . . . . . . . . . . . . . . . . . . . . , . . i ,v

Acknowledgements . . . . . . . . . . . . . . . . . . . . vi

Introduction . . . - . . . . . . . . . . . . . . - . . . ,. 1

Prlevious Investigations on the Fineness of Gold from Alaskan Placer Deposits . . . . . . . . . . . , . . . . . . 3

Discussion of the Fineness of Placer Gold from Alaska by Mining District . . . . . . . . . . . . . . . . . . . . . 3

Areal Distribution of Fineness Values in the Fairbanks Mining District . . . . . . . . . . . . . . . . . . . . . . 8

Summary and Conclusions . . . . . . . . . . . . . . . . . . 11

Appendix I . . . . . . . . . . . . . . . . . . . . . . . . 5 4

References Cited . . . . . . . . . . . . . . . . . . . . . 58

Bibliography . . . . . . . . . . . . . . . . . . . . . . . 59

FIGURES

Page

Fig. 1. Location of Alaskan placer mining districts . . . 12

Fig. 2. Gold fineness for Nizina district . . . . . . . . 24

Fig. 3. Gold fineness for Kenai district . . . . . . . . 2 5

Fig. 4. Gold fineness for Yentna district . . . . . . , . 26

Fig. 5. Gold fineness for Bonnifield district . . . . . . 27

Fig. 6. Gold fineness for Circle district . . . . . . . . 28

Fig. 7. Gold fineness for Eagle district . . . . . . . . 29

Fig . 8 . Fig . 9 . Fig . 10 . Fig . 11 . Fig . 12 . Fig . 13 . Fig . 14 . Fig . 15 . Fig . 16 . Fig . 17 . Fig . 18 . Fig . 19 . Fig . 20 . Fig . 21 . Fig . 22 . Fig . 23 . Fig . 2 4 . Fig . 25 . Fig . 26 . Fig . 27 .

FIGURES (cont.')

Page

. . . . . . Gold fineness for Fairbanks district 30

Gold fineness for Fortymile district . . . . . 31 . . . . . Gold fineness for Hot Springs district 32

. . . . . . . Gold fineness for Iditarod district 33

. . . . . . . . . Gold fineness for Innoko district 34

. . . . . . Gold fineness for Kantishna district 35

. . . . . . . Gold fineness for Koyukuk district 36

. . . . . . . Gold fineness for Marshall district 37

. . . . . . . Gold fineness for Rampart district 38

Gold fineness for Ruby district . . . . . . . . 39 . . . . . . . Gold fineness for Tolovana district 40

. . . . Gold fineness for Tuluksak-Aniak district 41

. . . . . . . Gold fineness for Council district 42

. . . . . . Gold fineness for Fairhaven district 43

. . . . . . . Gold fineness for Kougarok district 44

. . . . . . . . . Gold fineness for Nome district 45

. . . . Gold fineness for Port Clarence district 46

. . . . . . . Gold fineness for Solomon district 47

. . . . . . . . . Gold fineness for all districts 48

. . . . . . . . . . . . . Means of all districts 4 9

TABLES AND PLATES

Page

TABLE 1. Placer gold fineness for various Alaskan mining districts . . . . . . . . . . . . . . . . . . . . 13

TABLE la. Analysis of variance between and within mining districts . . . . . . . . . . . . . . . . . . . . 23

TABLE 2 . Mean, standard deviation and range of gold fineness values by mining district . . . 50

TABLE 3. Average gold fineness values for mining districts grouped according to geographic region . . 52

TABLE 4. Host rocks for the mineralization in the Fair- banks mining district . . . . . . . . . . . . . . 53

PLATE I . Mineral resources of the Fairbanks North Star Borough showing gold fineness values for various creeks in the Fairbanks mining district . . (in pocket)

iii

ABSTRACT

Gold fineness values for Alaskan placer deposits were

calculated using mint return production records and the follow-

ing formula for gold fineness:

Fineness = (Au/(Au + A g ) ) x 1000.

Past gold and silver production records from individuals and

mining companies for the period 1900-1974 from 800 creeks in

Alaska were examined and 550 creeks with production in excess of

LOO troy ounces of gold were selected for data analysis. The

data are summarized according to 41 mining districts and six

regions.

The overall mean fineness for the 550 samples is 889, the

standard deviation of the mean is 28.57, the 95% confidence

interval for the mean is 880-898. The mean gold fineness values

for the six regions studied are:

Fineness No. of Districts

Seward Peninsula 908 9

Upper Yukon-Tanana 884 11

Chandalar-Koyukuk 898 2

Lower Yukon-Kuskokwim 880 9

Copper-Susitna 8 8 6 8

Southeastern 893 3

The values for individual placers range from 567-995. One-

way analysis of variance among the six regions and the 41 dis-

tricts shows that the regions and districts can't be distin-

guished on the basis of gold fineness. The Kantishna district

is anomalous and has the lowest mean value of 789, the lowest

individual sample value of 567 and a coefficient of variation of

16 versus the average coefficient of variation of 4.33. The

Rampart and Council districts have a mean fineness of 915, the

highest mean values of the districts. Several districts, Kan-

tishna in particular, have bimodal distributions of fineness,

suggesting different sources of gold or different processes

affecting deposition.

We were unable to relate the gold deposits to particular

host rocks or to discern clearly the relationship of intrusive

rocks to the placer deposits.

ACKNOWLEDGEMENTS

The r e p o r t i s t h e f i r s t i n a ser ies o f p u b l i c a t i o n s by t h e

M i n e r a l I n d u s t r y R e s e a r c h Labora to ry and t h e A l a s k a D i v i s i o n of

G e o l o g i c a l and G e o p h y s i c a l S u r v e y s u n d e r a s p e c i a l a p p r o p r i a t i o n

by t h e A l a s k a State L e g i s l a t u r e t o the S c h o o l of M i n e r a l I n d u s t r y

t o c o n d u c t a " M i n e r a l A p p r a i s a l o f I n t e r i o r A l a s k a Mining D i s -

t r i c t s " . T h i s p rogram w a s i n i t i a t e d a t t h e r e q u e s t o f t h e

F a i r b a n k s North S t a r Borough. Funding for t h e r e p o r t w a s sup-

p l i m e n t e d by a grant u n d e r t h e Mining and M i n e r a l Resources

R e s e a r c h I n s t i t u t e , O f f i c e of S u r f a c e Mining , U.S. Depar tment of

I n t e r i o r .

The p h o t o g r a p h o n t h e cover of t h e p u b l i c a t i o n i s f rom t h e

Bunnel C o l l e c t i o n , U n i v e r s i t y A r c h i v e s , E l m e r E . Rasmuson L i -

b r a r y , U n i v e r s i t y o f A l a s k a , F a i r b a n k s .

Introduction

The expression of the relative quantities of gold and

silver in a mineral deposit can be described by two methods;

first as the simple ratio of gold to silver and second as the

"true fineness" which is the ratio of gold to gold plus silver

multiplied by 1000 (Boyle, 1979, p. 197). Note that "fineness"

as generally defined is the parts gold per thousand parts alloy,

which could include base metals, However, as used in this

paper, "fineness" is the ratio of gold to gold plus silver times

1000.

Sample calculation of gold silver ratio and true fineness,

Au gold Ag silver

Gold to silver ratio = Au/Ag True fineness = (Au/(Au+Ag)) x 1000

EXAMPLE

Production record

Gold Creek

Au 975 troy ounces

Ag = 105 troy ounces

Gold to silver ratio = Au/Ag = 975/105 = 9.29

True fineness = (Au/(Au+Ag)) x 1000 =

(975/(975+105)) x 1000 = 903

The advantage of using the fineness value rather than a simple

ratio in statistical reduction of data has been reviewed by Koch

and Link (1971). Although the use of fineness values is pre-

ferable in data reduction and analysis much of the literature

deals with the simple Au/Ag ratio. In this discussion both

expressions will be utilized since much of the referenced liter-

ature deals with Au/Ag ratios.

Boyle (1979) has extensively reviewed the literature on the

Au/Ag ratios of the various types of gold deposits and a summary

of his conclusions are listed in Appendix I. The major conclu-

sion bearing on this paper is that gold placers always have

Au/Ag ratios greater than 1,

In this investigation production records from approximately

800 creeks in Alaska were reviewed. These production records

were primarily mint returns reported by individuals and mining

companies up through 1974. These records are not inclusive of

all the production from Alaska nor do they include all of the

production from a given creek. The records report the number of

troy ounces of gold and silver produced and the last date of

recorded production. Fineness values were calculated for each

creek with a record of at least ten troy ounces of silver. By

this method a sample size of about one hundred ounces was in-

sured thus increasing the reliability of a given sample. Fine-

ness values for 550 creeks were determined and are listed in

this report. These fineness values represent past production

records and should not be used as a basis for determining the

fineness of current production on a given creek.

Previous Investigations on Fineness of Gold From Alaskan Placer

Smith (1941) discussed in detail the fineness of gold from

Alaskan placer deposits. The data base included 1534 samples

from 84 different creeks or areas in 41 separate mining dis-

tricts. The analysis of the data only included a determination

of the ranges in values and the percentage of values within

selected ranges. The values range from a low of 565 to 970

fine. Twenty-three percent of the records had fineness above

900; forty-two percent were between 850 and 899; twenty-six

percent were between 800 and 849; and nine percent were below

800 fine. Smith (1941) did not attempt to interpret the sig-

nificance of the data nor did he attempt to present data from

every creek in a given mining district.

We have calculated mean fineness values for each of the

seven major regions that were defined by Smith (1941). The

values are as follows: Southeastern, 898; Copper River, 888;

Cook Inlet, 898; Yukon River, 882; Kuskokwin River, 892; Seward

Peninsula, 907; and Kobuk River, 884.

Discussion of the Fineness of Placer Gold from Alaska by Mining District

The fineness values in Table 1 are tabulated by mining

district (see Figure 1) in the same order as the data presented

by Smith (1941). The means and standard deviations of fineness

values were calculated for each mining district. Histograms for

each district with at least eight samples are displayed in Fig-

ures 2 through 25. Figure 26 is a histogram of all fineness

v a l u e s l i s t e d i n T a b l e 1 and F i g u r e 2 7 i s a h i s t o g r a m of t h e

means f o r all t h e min ing d i s t r i c t s . Both h i s t o g r a m s i n F i g u r e s

2 6 and 2 7 a p p e a r t o be l i k e t h a t f o r a normal d i s t r i b u t i o n .

Note t h a t t h e f i n e n e s s s c a l e (x a x i s ) i s n o t t h e s a m e f o r a l l

h i s t o g r a m s . The means, s t a n d a r d d e v i a t i o n s and r a n g e s o f f i n e -

n e s s v a l u e s f o r e a c h min ing d i s t r i c t a r e l i s t e d i n T a b l e 2 .

I n T a b l e 2 s e v e r a l s t a t i s t i c s are c a l c u l a t e d . These a r e

t h e mean, s t a n d a r d d e v i a t i o n , s t a n d a r d normal v a r i a t e and t h e

c o e f f i c i e n t o f v a r i a t i o n . The mean o r a r i t h m e t i c a v e r a g e m e a -

s u r e s t h e c e n t r a l t e n d e n c y o r most p r o b a b l e v a l u e , t h e s t a n d a r d

d e v i a t i o n i s a measure o f t h e s p r e a d of t h e d a t a a b o u t t h e mean.

The s t a n d a r d normal v a r i a t e z = , where x i i s t h e v a l u e of

t h e o b s e r v a t i o n , Z i s t h e mean, s i s t h e s t a n d a r d d e v i a t i o n . z

i s measured i n u n i t s o f s t a n d a r d d e v i a t i o n and r e l a t e s t h e

observed v a l u e s t o t h e s t a n d a r d no rma l d i s t r i b u t i o n from which

p r o b a b i l i t y s t a t e m e n t s can be made. The c o e f f i c i e n t of v a r i a -

t i o n i s d e f i n e d as

CV = (s/X) 100 and r e l a t e s t h e s p r e a d of t h e v a l u e s t o

t h e mean.

The v a l u e s of t h e s t a n d a r d normal v a r i a t e can be u s e d t o

e s t i m a t e t h e p r o b a b i l i t y of o b t a i n i n g a sample mean a. c e r t a i n

number o f s t a n d a r d d e v i a t i o n s from t h e g r a n d mean. On t h e \

a v e r a g e , w e e x p e c t 6 8 % o f t h e v a l u e s t o f a l l be tween +- 1 s , 9 5 %

be tween + - Zs, and 9 9 % be tween t- 3s of t he mean. The proba-

b i l i t y of o b t a i n i n g a v a l u e - 3 . 5 s from t h e mean as in t h e case

of t h e K a n t i s h n a v a l u e s i s 1 i n 5 0 0 0 . C l e a r l y , t h e K a n t i s h n a

d i s t r i c t v a l u e s a r e anomalous.

From the above figures and Table 2 the following observa-

tions can be made:

1. The Circle, Kantishna, Koyukuk and Rampart districts

appear to have bimodal distributions of fineness values, in that

these three districts have samples with fineness values less

than 750. Other samples in these districts had to be around 900

fineness.

2. The Kantishna district has the lowest single fineness

value, 567, the lowest mean fineness value, 789, the highest

standard deviation, 126, and the highest coefficient of varia-

tion, 15.97.

3 . T h e Council district has the highest single fineness

value, 995.

4 . O f t h e districts with 4 or more samples, Gold Hill has

the highest mean fineness, 920.

5. Of the districts with 4 or more samples, McKinley has

the lowest standard deviation, 10, lowest coefficient of varia-

tion, 1.11.

In order to determine whether the districts could be dis-

tinguished by their fineness values, an analysis of variance

(ANOVA) was conducted on the data in T a b l e 1 using the Statisti-

cal Package for the Social Sciences published by the University

of Kansa~. The resulting F ratio is 4.314 and for 40 and 509

degrees of freedom (See Table la) at the 95 percent confidence

level this value is significant. Under the Duncan procedure two

subsets were determined. The first subset includes district

numbers 2, 5, 6, 8, 11, 12, 13, 14, 17, 19, 21, 22, 24, 26, 31,

32 and 41 (see Table 2 ) . The second subset included all the

districts except district 22, the Kantishna district. Under the

Tukey procedure the districts could not be divided into separate

subsets. From the analysis of variance only the Kantishna dis-

trict can be distinguished from the other districts by gold

fineness value at the 95% significance level.

An analysis of variance (ANOVA) was also done on the means

of the gold-fineness values from the different mining districts

grouped according to geographic region. The data and groupings

are shown in Table 3. The ANOVA was not significant at the 95%

confidence level, meaning that the gold fineness values for the

different regions are not significantly different.

The data in Table 3 show, however, that of the six regions

examined, the Seward Peninsula districts have the highest mean

fineness value of 905, and also tend to be the most uniform with

a coefficient of variation of 1.02. The lower Yukon and Kuskokwin

region, which includes the Kantishna district, has the lowest

mean gold fineness of 880, and the greatest variability, as

shown by a coefficient of variation of 4.14. The Southeastern

region shows a greater variability but the samples making up the

regional mean (3) and district mean (41, are so few that the

variance is unusually high and is probably not representative of

the region as a whole,

Without a detailed analysis of the regional geology of the

individual mining districts, only a general hypothesis can be

proposed to the account for the bimodal distributions and the

dispersion of the data within individual districts. The dis-

t17icts which demonstrate bimodal distributions generally contain

both metamorphosed sedimentary and volcanic rocks and intrusive

igneous rocks. The metamorphic rocks are often host to massive

sulfide mineral occurrences which tend to be high in silver

relative to gold. Quartz-vein deposits are usually associated

with intrusive igneous rocks and the gold fineness in quartz

vein deposits is usually high. Placer deposits formed from the

erosion of massive sulfide deposits would probably result in

lower fineness values while the placer deposits formed from

weathering and erosion of gold-quartz veins would generally have

higher fineness values.

The dispersion in fineness v a l u e s may be a function of

source rocks however it may a l s o be a function of depth of

formation of the lode source. Quartz veins in or near an intru-

sive body would form at higher temperatures than those veins

formed at greater distance from the heat source. Erosion of

veins in the epithermal (low temperature) zone would produce

placer deposits with a lower fineness than erosion of veins

formed in the mesothermal (medium temperature) and hypothermal

(high temperature) z o n e .

Forbes (1980) carried out scanning-electron microscope/x-

ray spectrometric analysis studies on gold nuggets and found

silver depletion rinds up to several microns thick on natural

nuggets but not on man-made nuggets. The loss of silver in

natural nuggets could be accounted for by the greater solubility

of silver under atmospheric environmental conditions during and

after placer formation. As grain size decreases the overall

surface area increases, and relatively more silver will be

leached. The theoretical result of such selective loss of

silver is to increase the fineness of the placer gold. These

observations are connected with those of Koshman and Yugay

(1972) who showed that chemical or mechanical treatment of

samples of placer gold increase the fineness of the gold by

dissolving or releasing chemical or mineral impurities. V51joen

(1971) has noted the opposite effect in gold grains from the

paleoplacer deposits of the Witwatersrand System. In this case,

the theoretical fineness decreases with decreasing grain size.

The opposite effect may be a function of differences in environ-

mental conditions during and after deposition in the 2.7 billion-

year old sediments. In either case, the fineness of the placer

gold has been affected by the depositional environment. The ef-

fects of depositional environments must be considered in any

hypothesis that attempts to explain the differences in the

fineness of placer gold. In Alaska, high-organic contents in

the alluvial deposits and permafrost conditions will affect the

relative solubilities of gold and silver and will be major

parameters affecting the environments of deposition of placer

gold.

Areal Distribution of Placer Fineness Values in the Fairbanks - - - - -

Mining District

The rocks that crop out in the Fairbanks district are part

of a sequence of metasedimentary and metaigneous rocks known as

the Yukon-Tanana Uplands schist of Lower Paleozoic and or Precam-

brian age (Foster, et a1 1 9 7 3 ) . The schist is both the host

rock for the lode-gold deposits in the district as well as the

bedrock unit for the placer gold deposits. This unit is com-

posed of a structurally complex sequence of quartz muscovite

schist, quartz mica schist, feldspathic schist, chlorite schist,

biotite garnet schist, carbonaceous schist, calcareous schist

and crystalline limestone. Recent work has shown that the unit

also contains a variety of gneisses, calc-magnesian schist,

phyllite, amphibolite and eclogite. The metamorphic sequence is

intruded by Mesozoic and Tertiary age rocks that range in compo-

sition from diorite to granite. Rocks of the Fairbanks district

have been affected by at least two major deformational events.

The first metamorphic event is associated with a complete re-

crystallization of the parent rock and with the development of

metamorphic mineral assemblages indicative of the middle and

upper greenschist facies. A later phase of metamorphism appears to

have been less intense and associated with the development of

retrograde metamorphic mineral assemblages. The early recrys-

tallization is associated with west northwest-trending folds,

while the later phase is associated with folding about northeast-

trending axes. Fold styles associated with the early recrystal-

lization appear to be isoclinal and overturned to the northeast.

Some folds are arcuate and recumbant. The northwest-trending

folds appear to be overturned and (or) recumbant, with axial

planes usually dipping to the south. The degree and direction

of overturning is variable and related to the superimposed

northeast-trending structures.

Chapman and Foster (1969) described 188 lode mineral deposits

in the Fairbanks district. These include: gold quartz veins

and fissure-zone replacement gold deposits, antimony, tungsten,

lead and zinc mineralization parallel to the compositional

layering and foliation of the Yukon Tanana Upland Schist and

tungsten skarn mineralization in the schist adjacent to the

Mesozoic and Tertiary intrusive rocks. With minor exceptions

all the deposits contain at least trace amounts of gold and

silver. Table 4 lists the host rocks for a11 the mineral oc'cur-

rences in the district as well as those with only Hg-Sb-W-Au-Ag

mineralization.

The placer deposits in the district are found along streams

draining the Pedro Dome, Giimore Dome and Ester Dome areas.

Both Pedro Dome and Gilmore Dome are cored by complex intrusives,

ranging in composition from granite to quartz diorite. Although no

major outcrops of intrusive rocks have been mapped in the Ester

Dome area numerous small irregular intrusive bodies and dikes

have been mapped on the flanks of the dome. Since the placer

and lode gold deposits in the district are restricted to these

areas, earlier workers including Chapman and Foster (1969)

thought that the intrusive rocks were the source of the gold.

Whether the intrusives were the source of the gold or whether

they simply provided the thermal energy to remobilize the pre-

cious metals in the Yukon Tanana Upland Schist, the intrusive

center appears to have some spatial relationship to the placer

deposits.

The role played by host rock and intrusive bodies in relation

to the gold mineralization of the district is not clear. At pre-

sent, we are examining this important question and it is ex-

pected that ongoing studies may yield data bearing on this

problem.

Summary and Conclusions

The expression of the relative quantities of gold and

silver in a mineral deposit can be described by either a simple

ratio of gold to silver or as a fineness value. The relative

quantity of gold and silver in a given deposit is a function of

the complex physiochemical conditions that existed during and

after deposition. The determination of these complex conditions

may be partial guides to the discovery of additional minerali-

zation.

Reported fineness values from Alaskan placer gold deposits

range from 567 to 995. Although the individual mining districts

cannot be distinguished by fineness values alone, several gen-

eralizations can be drawn. The Kantishna district has the

lowest mean fineness of 789 and the lowest fineness value of

567, and the highest standard deviation of 126. The Rampart and

Council districts have a mean fineness of 915 which is the

highest mean value for the districts with four or more samples.

The Council district has the highest fineness value of 995. The

Circle, Hot Springs, Richardson, Kantishna, Koyukuk, Marshall,

Georgetown and Tolovana districts have large coefficients of

variation, bimodal distributions, thus suggesting different

sources for the placer gold. This is particularly true for

Kantishna district.

Kant ishna Koyukuk Marsha l l Ramp ar t Richardson Ruby To lsvana McKin ley Georgetown Tuluksak Aniak Goodnews Bay Bluf f Counci l Fairhaven Kougaruk Koyuk Nome P o r t C l a r e n c e Solomon Kobuk

F igu re 1. Loca t ion of major p lace r mining d i s t r i c t s i n Alaska.

YEN'TNA YENTNA YENTNh YEN'TNA YENTNA YE:N"I'A Y EN'T'NA YE:NTNA YENTNA YEi:N'TNA YE:NTNA YE,N'I'NA VALDEZ CREEK VALDEZ CREf:K VAL..DEZ CIIEE:I.;' Bi:lNN I f:'I EL,fl BONNIFI'EL,D P(INNSF1ELD BONN1'F:IE:LD BONNIF'IEL-D BCINNI:FIEL..D B B N N I F I E L D BOMNIF~IELII BIINN.TI::'IEL,D BONNY F IEL,D R U N H I F I E L D RC1NNIF:'TELD C:ElhNLrALAFi' CHANDALAR C:tJc?rNDRLAR CtiANDAL.AR I:t.IANI:lAL..AA CHISANA [::HI SANA CHISANA C t i I SANA C:tJISANA C: I R C: I,.. E C I HCL-E CIRCLE C: I FirC1.E.: C: I RCL. E C1RCL.E CIRCLE (:I RCL..E CXRCLE CIF('CL..E C S RC1-E C1RI:L.E C I RC1.E C1RCL.E CIIRCLII C I R C L E CIRCLE

M I L L S ANI:l 'TWIN NO'TQEAC N1JGGE:T F:'A SS F'(IUI3MAN pETE:FtS RlJRY OlJL..C:H Si.d(JFi'T !;LUATE THUNDER WILL.OW w:r L_L.CIW I-.I.JCKY GUL,C3i VA1,DE:Z wnr*rE 1:lANIEL.S X:l R Y E:VA GCIL,D K I N G G'RIJBS'rAI(E tiOMES'TAI.;'E L.. I 'T 'T 1- E W CI 0 S Fi MARGUERITE MOUSE: F'L..R'T'T'E REX TOThTLANIKA PICi L I T T L E SOUAW S T + MARYS Sr.4tJAW TOP I N B I G EL..DORAISW CHISANA GOLD RUN L..I'r'TL-E EZLIlORAIlO SKOQKUH BIRCH BONANZA HOT TOM DCII ... L..RR BOULnER BUTTE CtDAl.. CROOKED DEADWOOD X)E:EZP EAGLE F A I T H HALF MILL-AR HARR I SON INDEPENDENCE KE'TCHEH LOPER MAMMOTH

'TAl,KEE'TNA TALK'EETNA 'l'A1,liEEl'NA TALI(EE:'I'NA TALICEEf'NA TAL-I<EETNA TALKE:E'I'NA TAI-KEEf HA TALKEE'I'NA TALKEE'I'NA ANCb-IORAGE: TAL..K'EEf:TNA t4IAL.Y HE:ALY HEALY FAIRBANKS HEAl..Y FAIRBANKS FAIRBANKS FAIRBANIiS FAIRBANI($ F A I RE(ANI.i'S HEAL-Y FAIRBANI(S t.IEAL..Y FAIRRhNI(S FAIRBANKS CHANIlAL,AR CHANDALAR CHhNCIAL..AR CHANDALAR CHRNDALAR NARESNA NARESNA NAEfESNA NABESNA NAHESNA CIRCLE C I R C L E CTRCL,E CHARLEY R I V E R C I R C L E CHARLEY RIVER CIRCLE: C I R C L E CIRCLE C I R C L E C I R C L E C I R C L E C I R C L E C I R C L E C I R C L E CIRCLE CIRCLE

I 0 4

It3 P ;F i-i z Gf #

NO+ D I S T R I C T CREE!( QUADRANGLE ( ~ u / G s u t n c ) ) x 1000 -d.-_..".".-Id.h _--............ -- --._"..-. - -_-.-........ -. "._.... -....--- * -......- C.-..l*ttllll..Il-....--.l -I-.-.I- -..".-----r---ll

HOT SF'RINGS HOT SPRINGS HOT SPRINGS HOT SPRINGS HOT SFRINGS HQT SPRINGS HOT SF'RINGS HOT SPRINGS HOT SPRINGS I-IClT SPRINGS HOT SPRINGS I*iOT SPRINGS HOT SPRINGS HOT SPRINGS HOT SPRINGS HOT SPRINGS IDITARQII I D 1 TAROXT I D I T A R O D IDXTAROD I D I T A R O D I D I T A R O D IDXT4RUII I I I I T A R O D I B I T A R O D I D I T ARQD I D I T A R O D ID1 TAROD I D I T A W O I ~ I D I T A R O D I n I T A R O D I D I T A R O D I U I T A R O D I I f I T A R O n I tl I TARQD INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNQKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO INNOKO

GLENN GLENN GULCH ,JAC#SCIN MILLXR NEVADA GUL..CI-I NEW YQRK OMEGA PATTERSON F'IClNEER RHODE I S L A N D ROSA SEA'T'TL.E SULL. XUAN THANKSGIVING TlJFTY WOODCHCIPF'ER BLACK CHICKEN CROOKED XSONLIN F L A T GLEN GULCH GRANITE HAPPY JUL I AN MALAMUTE MOORE UTTER PRINCE ClUARTZ SLATE SNOW GULCH T R A I L UPGRADE WILLOW BEAR BEAVER BEDROCK BOOB COL,ORAL~O C R I PFLE DODGE ESFERONTO ESTER F O X GULCH GANES GOLU RUN L I - r ' r ~ ~ HACKIE MADISON OF'HIR BPAULDING SFRUCE VICTOR GULCH

'I" ANANA 'I'RNANA TANANA TANANA 'I'ANANA 'TANANR TANANA TANANA TANANA TAANANA TANANA TANRNA TANANA 'T'ANANA TANANA TANANA I D I T A R O D I D I T A R O U II?ITAFi'OlCi I D I T A R O D I D I T A R Q D I D I T A R O D ID1"I'AHOD I D I T A R Q D IDSTARUIS f D I'T'AROD IBf TARUD IXSIITAROII I D I T A R Q I I UFHIR I D I T A R O ~ I 1111 TARQII m 1 T m o r 1 I D I T A R O D IDITARIJTI OPHIK OPHIR OPHIR QF'HIR OF'HIR OPHZR OPHI R OPHIR O P t i I R OFHIR OFHIR OFHIR OFHIR IDITAROXI OFHIR OF'HXR I D I T A R O D QPHIR OFHIR

NO+ D I S T R I C T .-. .- ..- -- .... - *.,. .*.. ,.., "+ *., ...* -. .... .- ....

I NNClKO I(ANT:E!.iCINA 1.i: h N 'T' X 8 1.1 N A KAN'T'I SHNA KAN'T T SEiNA l(:ANTI SHNA I<AN'T :[ SHNA I(AN'V'1:SHNA KANT lt3IiNA KANTISHNA KANTISt iNA KAN'TISHNA KIJYtJI(IJK Ii'CIYUKUK K0YIIlC:~JI.;' KOY Ul(l.lk' KCJY lJKt,Jl< I.I'CIYIJKUK KOY 1JI<UK l<UYUl<lJl< K[:)Y Ul<IJlK 1.I' (I Y 1J K [I I< Iif:IYUKUK KtIYIJKUK KE)YIJI<IJK KCIYLIKUK KOYI.JKI.JK I(C)Y LJKIJK KCl Y[.Jl<iJk' KOYlJKlJK KOY I.JKUK KQY I.JKUK I(OYUKUli I(OYIJKUI( KI:)YlJKlJK KOYUKI.JK KOYI.JKUK KOY UKlJK I(OY UKUK KOYUKUK KCIYUKUK KCIY UKLJK KOY I.II(UK KOYIJKUR KCIYUKUK I(CSY lJI<Uk: KQYUKIJK FIARStiALL MARSHALL MARSHALL MARSHALL HAFitStiA1.L MARSHALL HARSHALL

YANKEE C A R S BOiJ C:RE)CIKED EI I J I3 Ei: K h F t 7 X D A Y (:i 1" A C: I I. Fi' (3 1, E: N LI'FTL..E MOClSE HU)CISF.: STAMI::'EDE 'tWE:Nl'Y.-TWO PUP YEL"l."OM ARCH :t BAl-D F :I: RCti ("RE:IJI''E E: :K (3 t4.r M I 1.- 1:: EHHh F'AY GU1.C:t-l F:' A Y F4.J F:' GhF;i'NE!T GI:)LD HAHMOND HAMHOND H I V E K HCIBA'J'ZA I N D I A N J A Y ,JIM IiOYUKUK L..hKE L 1: NXlA htASCZC)'r MYRTLE: NI11..AN F'ORCUF:'l'NE EjHEEF' S L A T E SOUTH FORK KOYUKUK SH I TI4 SPRING SWITH THOMPSON PUP TWELVEMIL..€ IJ'TOF'XA UTQPIA VF:F?HC!NT WAKEUS W r 1. X:l

BUB'TA I L RUS'TER DISf iFPOINTMENT ELEPHANT FL-4.1' i(Al<C) HONTEZUMA

urSti I: R MT t MCKINLEY MT t MCKTNL-EY MT + MCKiNLEY M'T' MCKf NL..EY HT + MCK1NI.-EY MT* H(::KINL..EY H I + MCK INL-EY MT M.IC:KXNI ... EY HT t MC;I(INI..EY MT MI::KINL..E:Y H'F+ HCI<lNL.EY W f SEMAN W J: SEi:MAN W I E;E:MAN CHANI:lAL..AR WISEMAN WISEMAN W ISEi'lAN CtiANDAL.AR WISEMAN WISEMAN WISEMRN tilJGtiES HllGHEiS WISEMAN CtiANDR1,AR CHANDhLAR C;HANDAl,.AH C:tiRNDAL,AFr: WISEMAN WISEMAN W ISEHAN W ISEHAN CIiANDALAR CHANDALAR BETTLES W ISENAN WISEMAN W I SEMAN WISEMAN W ISEMAN MEL(3Z I TNA W I SEHAN WXSEMAN CHANDA1,AF;' BE'TTLES RUSSIAN M I S S I O N RUSSIAN M I S S I O N RUSSIAN M I S S I O N RUSSIAN MISS ION RUSSIAN M I S S I O N HOLY CROSS RUSSIAN MISSION

PIARSHA1,L.. MARSH ALL.. MAFI:SHAL..L_ Fi'AMPAR'T RAMF'ART RAMPART RAMPART HAMF'AR'T RAMPART RAMPART RAMPART RAMPAR'T RAMPART RAWF'AR'I' RAMF'AR'T RfCWARDSQN RICHARDSON RICHARDSON RICHARDSON R f CHAI:i'KlSC)N RICHARDSON R ICWARDSON RUBY FI'IJBY RUBY FI'IJEcY RUBY RUEY RUBY RUBY RUBY RUBY RUBY RUBY RUEY RUBY RIJBY RUBY RUBY RIJBY RUBY RUBY RUBY RLJBY RUBY RUBY RUBY RUBY RUBY TQLOVANA TO1,C)VANA 'TOLOVANA 'I"13LOVANA TCJLQVANA

WES'l' I-'ClRlt: W I:LI..OW WILLOW W 3: I... 8 C l N E{I:GHINQOK 1:lAWSON FL.UR1 DA GI.JNN1: SON ttO&I: ER ilLJN'TIil2 L x GI.~ M x NEICII~ NEVADA GULhC:H RUAIL RUF.{Y sLn.r.E SCllJ'Tt1 FTC)RK C4lJA 11, BANNER PUCKEYE CAR 1BClI.J LIEHUCRA'T NO GRUEf P Y Nfi: 'rENI:IEFi'F'6Cl'r' BEAR PUF:*

EIRCH CAtlF' D1JNC:AN FLAT F-OLJRTH O F <JI.JI ... Y GL-EN GlJl..C:ti GRANT'I'E GREENS7'C)RE LONG MI f lN f GHT MQNUMEN'T MCIOSE MEKE'tCHUM UF'HIR F'QORMAN RUBY SHClKT SOL.UWON SF'RlJCE STRAIGHT SWIFT TAHARACK TENDERFOOT TIMBER 'TRA 11, wILLaw AMY GERTRUDE L I I..L. I AN LIVENGOO11 LUCKY

QUADRANGLE (AU/(rrSU+A@) x 1000 ." ....._..-. "..-.-l-"X-----d-"..d .---.-".. -.....-...."..---

t4CILY CRCJSS Rl.J!i;SIAN H ISSICIN RUSSIAN HISSION TANANA L. I VEN(;CICID 'TANANA L..IVENGOOD TANANA '1'ANANh 'TANANA 'I'ANRNA 1, X V Ei: N G (:I O 1:l TANANA TANANA 'TANfiNh B I G X:IE:l.,f'A BIG XSE:L'I'A H I G DEL..'I'A BIG BE1,'TC.I BIG DEI ..: I 'A RIG DE:L..'TA B f Cj DELTA RIJEY BUSY NlJLA'T(1 RUBY RLJBY HIJBY RlJBY RLJEtY HlJBY RIJBY RLJBY RlJBY RLJBY RUBY RUBY RUBY RUBY RlJBY RUBY RIJBY RUBY RUBY RUBY RUBY RUBY RUBY RUBY LIVENGOQIl LIVENGQOD I- 1VE:NC;OOKI 1, f VENGOC)D LIVENG008

NO+ DISTRICT CREEK aUAClRANGLE (A u &yJ$&bO) X ---- -.--..-.---.- ---- ----- ..*-- - -----.- -.- ---.----- -------"*---.--.*--

l'QL.OVANA TOLOUANR TOLOVANA TOLOVANA MCKINLEY MCKINLEY MCKINLEY MCKINLEY MCKTNLEY MCKINLEY MCKINLEY GEORGETOWN GEORGETOWN GEORGETOWN TULUKSAK-ANIAK TULUKSAK--ANXAK TULUKSAK-ANIAK TULUKSAK-ANXAK TULUKSAK-AN1 AK TULUKSAK-ANIAK TULUKSAK-ANIAK TULUKSAK-ANIAK TUL-UKSAK-ANIAK TULUKSAK-ANIAK TUL-UKSAK-ANIAK TULUKSAK-ANIAK GOODNEWS RAY GOODNEWS BAY (;OI:)DNEWS BAY GOQDNEWS BAY GOQUNEIWS BAY GOODNEWS BAY BLUFF' BLUFF Bl..IJFF COUNCIL COUNCIL COUNCIL COUNCIL COUNCIL- COUNC I L COUNCIL COUNCIL, COUNCIL COUNCIL COUNCIL COUNCIL COUNCIL COUNCIL COUNCIL FAIRHAVEN FAIRHAWEN FAIRHAVEN FAXRHAVEN

MYRTLE QL I UE RUTH WILBUR BIRCH GULCH CANDLE CRIF'PLE EAGLE HIIIUEN tiO)l.ME::S MOORE CROI3KED DONLIN .JlJL.. I AN EKAR BBNANZ A CANYON CRIPPLE Ll OME FOURTY*-SEVEN GRANITE MARVEL, MARY LOU GULCH TAYLOR T INY TULUKSAK BUTTE FOX GULCH KOWKQW RAINEY SLATE WA'TTAHUSE CALIFORNIA DANIELS SWEDE AGGI E ALBION CROOKED DUTCH ELKHORN GOLD BOTTOH MELSING MISTERY MYSTERY N f UKLUK OFHIR O'r TER SWEETCAKE WARM WILLOW BEAR CANDLE CUNNXNGHAM DISCOVERY GULCH

LIVENGOOD L IUENGOOXI LIVENGOQD L I VENGOOD HEDFRA MCGRATH OPHIR i4CGRA'TH WEDFRA MEICIFRA IDITAROn IDITAROD 1 U I TAROI[:I I ICIITAFi'Oll RUSSIAN MISSION RUSSIAN MISSION BETHEL.. EETI.iEL BETHEL SLEETHIJ'TE BETHEL BETHEL BETHEL TAYLOR HTS RUSSIAN MISSION RUSSIAN MISSION GOODNEWS BAY GOODNEWS BAY GOODNEWS BAY GOODNEWS BAY GOODNEWS BAY GOOIjNEWS BAY SOLOMON SOLOMON SQLQMON SOLOMON BENDELEBEN BENDELEBEN SOLQHON SOLOMON SOLOMON SOLQMON SOLOMON SOLOMON SOLOMON SOLOMON BENDELEBEN SOLQMON SOLQMQN SOLOMON CANDLE CANDLE BENDELEBEN PENDELEBEN

DISTRICT

F A I RHAVIiN FAIRHAVEN FAIRHAUIEN FAIRHAVEN F:'A I FilHAUEN FAIRHAVEN FAIRHAVEN FAIRHAVEN FAIRtJAUEN E'AIRHAVEN FAIRHAVEN KOUGAROK KOUGAROK KOUGAROK KOUGAROK KOUGAROK KOUGAROK KClUGAROK KOUGARQK KOlJGAROK KQUGBROK KCIUGAROK KOUGAROK KOUGAROK KQUGAREIK I(OUL3ARt.K KOUGAROK KOIJGAROK KOUGAROK KOIJGAROK KOUGAROK KCJIJCjAROI.i: KOUGAHOK KO1JGARDK KOUGARQK ICOUGAROK KOYUK KOYUK KOYUK ICCIY 1JK KOYUK NOME NOME NOME NOME NQME NOME NOME NOME NOHE NOME NQWE NOME NOME

CREEK ..................................... "a, *.. ..., ".. -. -. .,.-....

OLAC1E:R GOLD HUN HANNUH INMACHUCK JUMP LAST CHANCE KOOFUK KIJGRUI\;: R I V E R MlJD OL..n GL.URY I~'A'T"TERS0N ATL-AS BEPISt:lN BLACK GULCH BOlJl ... nER B U Z Z A R D GULCH COFFEE DAML D 1: I: K DrJME (3Af:i;F If 3.. D GFi QUSE t4ARRa: S HUMBLIL-T I N D I A N IRON KOUGAFi'C3k' MACKLIN MRSCOT GULCM NCIRTH FORK #OlJGRRC)K NOXAF'AGA QUARTZ ThYL..OR T R I N I T Y WINDY WONDER GULCH BEAR BONANZA IIIME SWEEPSTAKE UNOALIK ANVIL ARC'T 1 C PANGQA BANNER BASIN BEACH BOULDER BOURBON AND WONDER BUSTER CENTER CHR I S'T I AN CLARA COQPER GULCH

QUADRANGLE (RU/(AUtAG)) x 1000 .... --.------.-._..lI__-.*.---.---.--.-_--l__

RENUULERE:N C ANIILE BENDELEBEN BENDEI-EHEN CANDI,.E CANDLE CANCILE BENIIELEBEN CANDLE

,IIE~NIIEL,EBEN BENUE:LEBEN E{ENX:lEL..EBEN SOLOMON BlNXllEt..ERE:N BENUELEBEN EI:NDEL.EBEN BENnEL-EBEN I3ENDELIE:BE:N BENDEL-EBEN EENX:IEL..EBI,N BENIlEL.EBEN BENDEL.E:IE{EN BENDELWEBEN BEN1SEL.EBEN RENDEL-EBEN SOLUM[:)N BENDELEREN BENBELEBEN EiENDELEBEN BENDEL-ETBEN BEND EL-EBEN BENDELEBEN BENDELEBEN BENDELEBEN BEiNDEL. EEEN BENDELEBEN CANltlLE NOR'TON BAY CANDLE CANDLE NORTCIN BAY NOME NOME NOME NQME NOME NOME NOME NCIME NO#E NOHE NOME NOHE NOME

NO+ DISTRICT CREEK OUADRANGLE (OU /b U $.&GI) ---...-.-. .."---...--..."--.----.I-r-.- - w - ,-. .- ............................... "" l-l......I..r,.-,ll-"+.- - *.-XI - -..* I.*-.".- z-L.a,-.-

NOME NOHE NOHE NOME NOME NQME NClME NCIME NOHE NOHE NOME NOME NOME NWME NDME NOME NOWE NUME NOi'lE: NOME NOME NOHE NOME NOME NOME NOME NOME: NOME NOHE NOHE NUME NDME N Cl M E: NOME NOME: NOME NOME NUME NUME NOME NI3HE NOME PORT CLARENCE PORT CLARENCE P Q f t l ' CL.ARENCE PORT CLARENCE PORT CLARENCE PORT CLARENCE PORT CLARENCE PORT CLARENCE PORT C1,AREZNCE PORT CLARENCE PORT CLARENCE FORT CLARENCE

IIRHLING DERBY LIEX'I'EW DOROTHY I IRY FLAT GL.RCIER BRASS GIJLdCH GRUB GULCH HASTINGS HOEiSON IIOLY OIXE EIUNGHY TREiNE JESS I...AFi'l' CHANCE L_AUFI'AXIA L. 1: 'r TI... E NRNILA MQNLJHENT NEKALA GULCH NI:W'I"ON NOME REACH 12) NCIME: BEACti ( 3 ) NOME R I V E R N1JGOE:T OREGON F:*ELUK

F:'TONEER FRTJSPEC'T ROCK ROCKY M'T ST MICHAELS SAUNDERS SHEPHERD SNAKE SFECIHEN GULCH SUBMARINE BEACH SUNSET TWIN MT+ WhSHINGTQN WONDER A1,DEfi' ELlJESTONE BUCK BUClD COYOTE DESE D I C K GQLDRUN IGLOO M I L L I O N SUNSET SWANSQN

NOHE NOHE NOME NUME NOME NOME NOME NClME NOHE NQWE NOME NClME NOME NQME NOME NQME NOHI:: NOME NOME NOHE NOME NOME NUME NClME NOME NOME NOME: NUME NOME NUME NCl ME NQME NQME NOME NOME NOME NOME NQME NOHE NOME NOME NQHE TELLER TELLER TELLER TELLER TELLER TELLER TELLER TELLER TELLER TELLER TELLER TELLER

NO + D I S ' I ' R I C T C:REE:K Cl lJAI lRANGLE (AU/(RUf AG)) x 1000

-...+- ..-.........",-----. ---.----------------**.-.*..* ........ .... ..-..*-- * ----.--,-.. "+-..,+.- -.v.w---- -.+* ----,--. ...-- --..--

F.'IlR'r CI,AFrENCE SCILOMCIN SCIL..ElM[JN SOLOFION SOL..UMQN SOLOMON SOLOMON SOLOMON SOLOMON SOLOWON EiOL..OMON SOLOMQN SQLOWON SOLOMON SOLOMON SOLOMON SOLOMON SOLOMON SOLOHON KQEUK KOEUK KOBUK KOBUK KQBUK

W I N D Y AHERsC:AN BEAVER BIG tiURRAH BUTTE: CASAClEPhGA GOOSE: K A S S O N L I T T L E HURRAH LOWER W I L L O W MOONLIGH'1" P A J A A A F:'E:NELOF'E F E N N Y S H O V E L SOLOMON SPR1lC:E WEST W IL-1,OW C A L I F ' C I R N I A CANYON DAtiL KL.El'?Y GHLJNGNAK

'T'ELLLER SOLUMUN SOLOMON SOLOHON SOLOHON SClLOMUN SULOHON SCILOHON SQLQHON SOL,OMON SOL..OMUN SOLOMON SOLOHON SOL,OMON SOLOMON E;OLC)MON SOLOMQN SI:)LClMON SOLOMON SIIIJNGNAK B A I R D PITS SHIJNGNAK B A I R B MT!i A M B L E f t RIVER

TABLE la. Analysis of variance between and within mining districts.

S o u r c e D.F. Sum of Squares Mean Squares F R a t i o

Between Groups 4 0 0.2969 0.0074 4.314 With in Groups 5 0 9 0 . 8 7 5 9 0.0017 TOTAL 5 4 9 1,1728

T a b l e 2. Mean, s t a n d a r d d e v i a t i o n and r a n g e o f gold f i n e n e s s values by mining d i s t r i c t .

S tandard S c o r e D i s t r i c t Mo. of f o r D e v i a t i o n from Standard C o e f f i c i e n t Number D i s t r i c t Samples Grand Mean Mean D e v i a t i o n V a r i a t i o n Range

P o r cup i n e Juneau Yakataga Chis toch ina N i z i n a Nelchina Kenai Girdwood Yen tna Valdez Creek B o n n i f i e l d Chandalar Chisana C i r c l e Eag le Fa i rbanks For t y m i l e Gold H i l l H o t S p r i n g s I d i t a r o d Innoko Kant ishna Koyukuk Marsha l l Rampart Richardson Ruby To lovana McKinley Georgetown

T a b l e 2 con t inued

Tuluksak Aniak Goodnews Bay Bluf f Council Fai rhaven Kougaruk Koyuk Nome P o r t C la rence Solomon Kobuk

Grand Mean = 889.

S- = 28.57 X

95% Confidence I n t e r v a l f o r Mean = 880.2 - 897.7 = 880 - 898

Table 4. Host rocks for the mineralization in the Fairbanks mining district (data source: Chapman E Foster, 1969).

All mineral Hg/Sb/W Occurrences Occurrences

Silicified schist and schist undifferentiated

Quartzite and graphite schist

Muscovite schist and muscovite feldspar schist

Biotite and biotite garnet schist

Marble

Greenstone and amphibolite

Intrusive rocks and skarns undifferentiated

TOTAL

APPENDIX I

Summary of Boyles' (1979) Conclusions Regarding Au/Ag Ratios

for Various Deposits:

"1. Only three types of hypogene deposits have Au/Ag ratio

consistantly greater than 1. These are the auriferous

quartz pebble conglomerate deposits, certain skarn-

type deposits and most, but not all, gold-quartz veins

in Precambrian, Paleozoic, and Mesozoic rocks. Ter-

tiary deposits in certain belts also have ratios

greater than 1, but they a r e r e l a t i v e l y uncommon. A l l

Gold placers always have ratios greater than 1.

2. The Au/Ag ratios in disseminated deposits in shales

and sandstones (Kupferschiefer and red bed types) are

generally low, indicating a relatively high degree of

mobility and concentration of silver during the forma-

tion of these particular deposits.

3. In the auriferous quartz-pebble conglomerate deposits

the range of the Au/Ag ratios is generally narrow, but

there are some significant differences in some deposits

such as the Witwatersrand, .... (Range 5.8-15.6). 4. There are few data on the gold content of the "Mis-

s i s s i p p i Valley type" lead-zinc deposits, and hence a

precise knowledge of the Au/Ag ratios is not obtainable,

5. The Au/Ag ratios in skarn deposits are exceedingly

variable and related to the mineralogy and hence the

chemistry of these deposits.

6. Massive nickel-copper s u l p h i d e s of the Sudbury type,

generally associated with basic igneous rocks, seem to

have a narrow range of Au/Ag ratios from about 0.03 to

0.07, .... 7. The porphyry copper deposits tend to have a relatively

low Au/Ag ratio judging from the few good data avail-

able.

8. The massive polymetallic sulphide deposits (Flin Flon-

Noranda-Bathurst type) nearly all have relatively low

Au/Ag ratios, which average about 0.025.

9. The polymetallic veins and the native silver-cobalt-

nickel arsenide veins have the lowest ratios of all

the various types of auriferous hypogene deposits,

indicating an extreme mobility for silver and prac-

tically no mobility for gold during their formation.

LO. Gold-quartz veins in Precambrian, Paleozoic and

Mesozoic rocks generally have Au/Ag ratios greater

than 2, and these average about 4.2 (range 1.37 to

12.5).

11. Gold-quartz veins, lodes, and stockworks in Tertiary

andesite, dacite, rhyolite, and other associated

volcanic rocks generally have ratios less than 1 .... 12. Siliceous sinters precipitated from present-day hot

springs generally have Au/Ag ratios less than 1.

13. Gold placers always have Au/Ag ratios greater than 1

regardless of age of the source deposits.

Deposits in older geological formations are frequently

richer in gold than those in younger formations.

The evidence that the Au/Ag ratio is an index of tem-

perature of formation or recrystallization of deposits

is conflicting. .... On a statistical basis, however,

there is some evidence to support the contention that

deep-seated (high temperature?) deposits have a higher

Au/Ag ratio than those formed at intermediate depths

or near the surface, presumably under conditions of

lower temperatures.

There is considerable evidence to show that the Au/Ag

ratio increases in primary haloes with proximity to

ore shoots in most types of epigenetic gold deposits.

Shcherbina's (1956a) view that gold i s predominant

in telluride ores whereas silver is dominant in

selenide ores appears to be true.

Gold and silica (quartz) show a marked association

whereas silver tends to be concentrated in an environ-

ment where carbonates are abundant.

Evidence from many auriferous belts throughout the

world indicates that there is a wall rock effect on

the Au/Ag ratio, the ratio being higher where the wall

rocks are basic than where acidic rocks are the hosts.

The Au/Ag ratio in deposits seems to depend on regional

metallogenic peculiarities in a crude way, if only

certain types of deposits are considered."

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-

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Viljoen, E.A., 1971, An electron-microprobe analysis of gold in the Witwatersrand blanket and in ores from the Barberton Mountain Land, National Inst. Metal., S. Afr., Rept. no. 1361, 7 P*

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Documents

Report No.dggs.alaska.gov/webpubs/mirl/report_no/text/mirl_n45.pdf"true fineness" which is the ratio of gold to gold plus silver multiplied by 1000 (Boyle, 1979, p. 197). Note that