Newly located Occurrences of 

lode Gold Near Table Mountain, 

Circle Quadrangle, Alaska 

Newly Located Occurrences of 

Lode Gold Near Table Mountain, 

Circle Quadrangle, Alaska 

By W.O. MENZIE, RENMIN HUA, and H.L. FOSTER 

Results of brief studies of the field relations, trace-element 

geochemistry, mineralogy, and fluid inclusions of new lode 

gold occurrences near Table Mountain, Circle quadrangle, 

Alaska, are reported. Similar occurrences probably were the 

sources of placer gold deposits in the Circle mining district. 

U.S. GEOLOGICAL SURVEY BULLETIN 1682 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

library of Congress Cataloging-in-Publication Data 

Menzie, W.D. 

Newly located occurrences of lode gold near Table 

Mountain, Circle quadrangle, Alaska. 

(U.S. Geological Survey Bulletin 1682) 

Bibliography: p. 

Supt. of Docs. No.: I 19.3:1682 

1. Gold ores-Alaska Mountain Region (Yukon-Koyukuk 

Borough). I. Hua, Renmin. II. Foster, Helen Laura, 1919-

. Ill. Title. IV. Series: U.S. Geological Survey Bulletin 

1682. 

QE75.B9 No. 1682 557.3 s 86-600235 

[QE390.2.G65] [553.4'1 '097986] 
CONTENTS 

Abstract 1 

Introduction 1 

Geologic setting 2 

Results of initial geochemical sampling 4 

Field relations of the gold occurrences 4 

Geochemical results 4 

Petrography of mineralized samples 4 

Fluid-inclusion studies 5 

Crushing experiments 9 

Discussion 10 

References cited 13 

FIGURES 

1. Map of the Circle quadrangle 1 

2. Reconnaissance geologic map of the Table Mountain area 2 

3. Photomicrographs of selected thin and polished sections from the Table 

Mountain a rea 3 

4. Map showing locations of sample sites 5 

5. Histograms of homogenization temperatures of fluid inclusions from the 

Table Mountain occurrence 12 

6. Histograms of homogenization temperatures of fluid inclusions from 

occurrences in and adjacent to the granite 12 

TABLES 

1. Analytical data of rocks from the Table Mountain area 6 

2. Analytical data of rocks from stations 31, 32, and 33 in the Table 

Mountain area collected in 1983 10 

III 

Newly Located Occurrences of Lode Gold Near 

Table Mountain, Circle Quadrangle, Alaska 

By W.O. Menzie, Renmin Hua 1

, and H.L. Foster 

Abstract 

Newly located occurrences of lode gold in the 

vicinity of Table Mountain, Circle quadrangle, are 

probably similar to those which were sources for 

placer gold in the Circle district and Faith Creek 

area. Brief studies were made of the field relations, 

trace-element geochemistry, mineralogy, and fluid 

inclusions of the occurrences. Most of the goldbearing samples are clustered in two areas. The 

highest concentrations of gold (2.6-140 ppm) occur, 

just west of Table Mountain, in black biotite schist and 

in quartz veins adjacent to a fault zone that is 

intruded by a hypabyssal felsic dike. Five kilometers 

to the northeast, where a small granite pluton crops 

out, gold was detected in lesser amounts ( 0.05-0.2 

ppm) in country rocks adjacent to the granite, in the 

granite adjacent to dikes, and in felsic dikes. The 

occurrences have a simple mineralogy: pyrrhotite, 

arsenopyrite, minor chalcopyrite, and rare enargite 

and sphalerite. They formed from low-saline fluids 

( 10 weight percent NaCl equivalent) whose sulfur 

fugacities were within the stability field of 

pyrrhotite. Based upon fluid-inclusion data, we infer 

that the occurrences formed at moderate 

temperatures from fluids that initially boiled, over the 

range 370 to 320 °C, and then gradually cooled. Field 

relations and estimated depths of formation of contact 

metamorphic effects and quartz veins indicate that 

the occurrences formed in an active tectonic 

environment. 

INTRODUCTION 

The Circle quadrangle, a major gold producing 

area of Alaska, has produced at least 850,000 oz of 

gold (Bundtzen and others, 1984), all from placer 

deposits. Production has been from four areas (Menzie 

and others, 1983), the majority coming from the Circle 

mining district. During regional geologic studies, 

which were part of the Alaska Mineral Resource 

Assessment Program (AMRAP), several samples of 

1Department of Geology, Nanjing University, Nanjing, 

China. 

gold-bearing rock were collected from two areas in the 

Circle B-4 quadrangle. At one area, near Table 

Mountain, two samples of fine-grained biotite schist 

collected adjacent to a fault contained 40 and 140 ppm 

gold. About 5 km northwest of Table Mountain, low 

levels of gold (<1 ppm) were detected from samples 

taken in and adjacent to a small felsic pluton. 

Although the streams that drain these two areas 

have not been mined, the main productive streams of 

the Circle district are just to the east; a smaller area 

of placer mining, here called the Faith Creek placer 

area, lies to the west of Table Mountain (fig. 1). 

Because occurrences such as those near Table 

Mountain and the pluton are probably similar to those 

that were sources for the placer gold, brief studies 

were made of the field relations, trace-element 

chemistry, mineralogy, and fluid inclusions. The 

studies indicate that these gold occurrences, which are 

characterized by a simple mineral assemblage, 

probably formed at shallow depths in and adjacent to 

fractures that were active during the late stages of 

felsic igneous activity. 

"'lime Peak 

Mt "" 

"'Prind!!../) r---.,. 

I ...-/ / / L.---;L._,/ 

Faith Creek 

placer area 

? I 

20 KILOMETERS I 

_.....------ oCentral I' --...... , l Circle mining ') 

"' 1 district 1 

Table ( ~ /-, ,.._../ Mt \_../ ...... ...._../ J 

650L-----------------------------~-Q-UA_D_RA_N_GL_E_LO_CA_T_ION~ 

Figure 1. Circle quadrangle showing locations of areas 

discussed in text. 

1 
GEOLOGIC SE'ITING 

The Table Mountain area, Circle quadrangle, is in 

the northeastern part of the Yukon Tanana Upland-- a 

physiographic province that mostly lies between the 

Yukon and Tanana Rivers in east-central Alaska. 

Recent geologic studies include reports by Foster and 

others (1983), Burack and others (1984), and Burack 

(1983). The Table Mountain area (fig. 2) is composed 

primarily of pelitic and quartzitic schists and 

quartzites that have been regionally metamorphosed to 

upper greenschist facies, then subsequently intruded 

and contact metamorphosed by a granite (Streckeisen, 

1975) pluton. The rocks were in turn cut by a leftlateral fault (the Swamp Saddle fault) and intruded by 

felsic hypabyssal rocks, probably in the early Tertiary. 

The metamorphic rocks in the Table Mountain 

area belong to the quartzite and quartzitic schist unit 

of Foster and others (1983) and are composed of light 

gray quartzite, black biotite schist, fine-grained 

greenish-gray mafic rocks and light-greenish-gray 

calc-silicate rocks (Burack, 1983). These rocks were 

metamorphosed to upper greenschist facies before the 

intrusion of the granite (Burack, 1983). The intrusion 

Geology modified from Burack ( 1983) 

and Foster and others (1983) 

of the granite into the quartzite and quartzitic schist 

unit locally resulted in the development of biotite 

porphyroblasts that transect the metamorphic 

foliation, the resorption of garnet, and the 

development of a granoblastic texture. Based upon 

these changes, Burack (1983) concluded that the 

contact metamorphism took place at between 475 and 

515 °C and at pressures less than 2 kbar, or at a depth 

of about 6 km. 

Granite crops out over an area of only about 2 

km2; however, the distribution of contactmetamorphosed rocks suggests that granite underlies 

much of the Table Mountain area at relatively shallow 

depths (Burack, 1983). Two phases of the granite are 

exposed: coarse-grained equigranular biotite granite, 

and porphyritic biotite granite with a fine-grained 

groundmass. The coarse-grained granite (Streckeisen, 

1975) is composed of 23 percent plagioclase feldspar, 

29 percent quartz, 41 percent potassium feldspar, and 

7 percent biotite. Plagioclase is altered to white 

mica, and biotite is altered to chlorite. Because the 

granite is altered, it has not been dated; similar 

plutons in the northwest part of the Circle quadrangle 

have yielded ages of 66 to 57 m.y. B.P. (Wilson and 

Shew, 1981). 

/ 

0 

I 

.5 

I 

1 KILOMETER I 

EXPLANATION 

~ Alluvium and colluvium (Quaternary) 

[fi.::.\1 Dike and hypabyssal rocks (Tertiary) 

~Granite (Tertiary and (or) Cretaceous) 

~ Quartzite and quartzitic schist 

~ (Paleozoic and (or) Precambrian) 

~ Rocks that have been contact 

~ metamorphosed 

~ o o Fault or lineament from aerial -- photograph-Dotted where 

covered. Arrows indicate 

direction of relative horizontal 

movement 

-3000- Contour, in feet 

Figure 2. Reconnaissance geologic map of Table Mountain area. 

2 
Both the granite and metamorphic rocks have 

been intruded by dikes and hypabyssal rocks which are 

most abundant west and southwest of the granite. 

Most dikes are felsic, but a few are of intermediate 

composition. Some dikes are aphanitic, others are 

porphyritic. Phenocrysts in the porphyritic dikes are 

quartz, potassium feldspar, and plagioclase. The 

groundmass of the dikes was probably originally 

plagioclase, potassium feldspar, and quartz, but it is 

B 

~ 

L_ ________ .9_m __ m ____ ~ 

\ 

.9 mm 

. 9 mm 

now mainly fine-grained white mica. The quartz 

phenocrysts have rounded crystal forms suggestive of 

partial resorption (fig. 3A) and in some cases the 

quartz phenocrysts are embayed (fig. 3B). Some dikes 

contain limonite cubes that formed after pyrite(?), and 

one dike contains minor disseminated purple fluorite in 

a veinlet. The textures of the dikes suggest that they 

were emplaced at shallow depths. 

.05 mm 

.05 mm 

Figure 3. Photomicrographs of selected thin and 

polished sections from Table Mountain area. A, 

Rounded quartz phenocrysts in felsic dike. __!!, Rounded 

and embayed quartz phenocryst in felsic dike. C, 

Quartz veinlet in felsic dike. D, Arsenopyrite 

surrounded by pyrrhotite from margin of quartz vein. 

~' Fluid inclusions from porphyritic felsic dike • 

3 
RESULTS OF INITIAL GEOCHEMICAL SAMPLING 

Table 1 lists analytical data for 5-kg grab 

samples collected during early phases of the study 

(Foster and others, 1984). Gold was detected in all of 

the major rock types present in the area: pelitic and 

quartzitic metamorphic rocks, calc-silicate rocks, 

altered granite, and felsic dikes. Figure 4 shows the 

spatial distribution of the 11 gold-bearing and 72 

barren samples. The gold-bearing samples are 

concentrated in two areas: (1) near Table Mountain 

and (2) in and adjacent to the exposed granite pluton. 

Field Relations of the Gold Occurrences 

Table Mountain Occurrence 

Two samples of tourmaline and sulfide-bearing 

black biotite schist, which contain 40 and 140 ppm 

gold, were collected about 3/4 km west of Table 

Mountain. This area is adjacent to a fault zone, which 

is characterized by the presence of tourmaline in 

adjacent rocks (Burack, 1983). During our follow-up 

study a felsic dike and a sulfide-bearing quartz vein 

were identified nearby (station 31, fig. 4). The felsic 

dike rock intrudes schistose quartzite beneath the 

ridge crest adjacent to the fault. The dike contains 

phenocrysts of quartz, potassium feldspar, and 

sericitized plagioclase set in a fine-grained 

groundmass that has been altered to white mica (fig. 

3~). The dike also contains rare veinlets with 

disseminated purple fluorite. The margins of the body 

are brecciated, and the resulting breccia is cut by thin 

quartz veinlets (fig. 3C). In places, breccia fragments 

are set in a rna trix ofTimonite. Along the ridge, west 

of the fault zone, a 2.5- to 5-cm-thick arsenopyritebearing quartz vein has been emplaced parallel or 

subparallel to the foliation of the schistose 

quartzites. Both the vein and foliation are 

subhorizontal. The vein contains open spaces and 

comb structure; arsenopyrite occurs within the vein 

but is most common as a coating on the outer edges of 

the vein wall. Tourmaline also occurs locally along the 

vein wall. We followed the vein for about 100 m along 

strike until it was lost in rubble. It seems likely that 

this 2.5- to 5-cm-thick vein underlies ~uch of the 

ridge west of the fault-- an area of 0.1 km . 

Occurrences in and Adjacent to the Granite 

Some samples of altered granite and the adjacent 

quartzite and quartzitic schist contain low levels of 

gold (see table 1); the gold-bearing samples were found 

within the pluton and on the north, east, and south 

sides of the pluton. Two sites were examined more 

closely, one near the eastern (station 32) and one near 

the western (station 33) margins of the granite (fig. 

4). On the west edge of the granite, a yellow-stained 

(arsenic?) hypabyssal felsic dike with potassium 

feldspar, quartz, and biotite phenocrysts in a very fine 

grained groundmass cuts the equigranular granite. The 

dike contains fine-grained sulfides, disseminated and 

as clots in the groundmass. Adjacent to the dike the 

4 

granite contains clots of probable arsenopyrite. On 

the east side of the granite, several dikes are exposed 

that contain large phenocrysts of potassium feldspar, 

rounded quartz, and altered plagioclase feldspar set in 

a fine-grained greenish matrix. 

Geochemical Results 

Table Mountain Occurrence 

Table 2 presents analyses of 5-kg grab samples 

collected from the Table Mountain occurrences in 

1983. The samples were taken from one site, station 

31 (fig. 4). Traces of silver and low levels of tin were 

found in the hypabyssal dike and in an iron-stained 

sample of the breccia. Two samples of breccia that 

were not iron stained do not contain silver or tin at 

detectable levels. Two samples of the quartz vein 

with sulfides along the vein walls both contained high 

values of gold, arsenic, and copper. Antimony was 

detected in both samples. 

Occurrences in and Adjacent to the Granite 

Gold was detected only in the sulfide-bearing 

hypabyssal felsic dike (table 2). Silver was detected in 

the dike and in the granite adjacent to the dike; tin 

was also detected in these samples. A sample of this 

dike without sulfides contained detectable tin but not 

gold or silver, and a sample of a porphyritic phase of 

the pluton contained 10 ppm tin but also did not 

contain detectable gold or silver (table 2). A sample 

of quartzite from adjacent to the pluton did not 

contain gold, silver, or tin in detectable amounts. A 

sample of a dike from the eastern side of the pluton 

was geochemically indistinct. 

Petrography of Mineralized Samples 

Table Mountain Occurrence 

Burack (1983) examined thin sections and a 

polished section of the gold-bearing black biotite 

schist in transmitted and reflected light. She reported 

that they contain abundant biotite, tourmaline, and 

silver-colored sulfides including arsenopyrite. She also 

noted that the sulfides cross the weak foliation in the 

rock and therefore formed after the foliation. 

We examined both thin and polished sections of 

the quartz vein with sulfide-coated outer walls. 

Sulfides occur within the vein and as a coating with 

biotite and minor white mica on the outer vein walls. 

Sulfide minerals identified in and adjacent to the 

quartz vein were pyrrhotite and arsenopyrite, minor 

amounts of chalcopyrite, and rarely enargite and 

sphlalerite. The pyrrhotite is anhedral and cut by 

cracks along which it is oxidized. Arsenopyrite is 

euhedral and occurs as bladed crystals which in places 

appear as islands within the pyrrhotite (fig. 3D). 

Chalcopyrite is subhedral and in places contains 

unreplaced pyrrhotite. The enargite is anhedral. The 

spalerite contains chalcopyrite. 
Occurrences in and Adjacent to the Granite 

Thin sections of the sulfide-bearing felsic dike 

and the adjacent sulfide-bearing granite were 

examined in transmitted light. Sulfides in the felsic 

dike are very fine grained. They are abundant in the 

groundmass of the dike and occur both disseminated in 

the groundmass and in clots. The granite adjacent to 

the dike contains isolated clots of arsenopyrite on the 

rims of partially altered plagioclase grains. 

Fluid-Inclusion Studies 

Fluid inclusions from the quartz vein at the 

Table Mountain occurrence and from dikes from the 

occurrences in or adjacent to the pluton were studied 

by using a heating-freezing stage. Sites for these 

samples are shown by an asterisk in figure 4. Of the 

20 doubly polished plates that were examined, 6 

contain a sufficient number of inclusions of a size 

large enough (>5llm along their maximum dimension) to 

make the heating-and-freezing measurements. The 

samples contain two major types of fluid inclusions: 

liquid-rich inclusions and vapor-rich inclusions, termed 

type I and type II, respectively. Liquid-rich inclusions 

6 

• 30?5 

Figure 4. Locations of sample sites (see tables 1 and 2). 

are more common than vapor-rich ones in the samples 

that contain both types. Inclusions of both types occur 

as isolated entities and are unrelated to visible 

microfractures. Type I inclusions are distributed 

randomly throughout the quartz; type II inclusions are 

round, occur in clusters, and show no evidence of 

necking to adjoining type I inclusions. Therefore both 

types of inclusions are interpreted as being primary 

and (or) pseudosecondary and where both types are 

present, as having been trapped at the same time. 

Most fluid inclusions for which measurements were 

made belong to type I; these inclusions generally have 

less than 15-volume-percent vapor phase at room 

temperature. Salinities of the fluid inclusions were 

determined by using the depression-of-freezing-point 

method described by Roedder (1962). 

Table Mountain Occurrence 

Measurements were made on three samples of 

the quartz vein from the Table Mountain 

occurrences. Sample 311' is white quartz with 

abundant sulfides; it contains only liquid-rich 

inclusions. Sample 31J"' is sulfide-bearing vein 

material with clear and white quartz that contains 

0 .5 1 KILOMETER 

EXPLANATION 

Sample sites 

e2 Number indicates number of samples in 

which no gold was detected 

Q One sample with as much as 1 ppm gold 

/~ Number indicates number of samples 

without detectable gold and dot indi- cates one sample with 1 to 10 ppm gold 

0 

~32 

Two samples that contained at least 10 

ppm gold 

Geochemical and fluid-inclusion samples 

for this study 

-3000- Contour, in feet 

5 
Table 1. Analytical data of rocks from the Table Mountain area 

[Analysis of Au by atomic absorption; all other analyses by six-step semiquantitative emission spectrographic 

methods. Fe, Mg, Ca and Ti in percent; all others in parts per million. G, greater than the amount listed; L, less 

than the amount listed; N, not detected at amount listed. Analysts included R.M. O'Leary. G. W. Day, E.F., 

Cooley, P. Risoli, A. Gruzensky, G. Ito, S.J. Sutley, J. Hurrell, G. D. Hoffman, R.R. Carlson, W. Martin, F.J. 

Takacs. D.L. Brown. J.A. Domenico, D. Galland. J.M. McDade, A.L. Meir, D.G. Murrey, A.J. Toevus, and S. A. 

Wilson] 

Station Rock Fe 

number and description 

sample letter 

35A 

35B 

36C 

37A 

38 

39 

40 

42A 

43B 

3017C 

3020A 

3075A 

3075C 

3075G 

3075J 

30751 

3075N 

3082B 

3082D 

3084D 

3089A 

3090B 

3090E 

3092B 

3093A 

3095A 

3103A 

3106A 

3107A 

3107B 

31071 

3107L 

3111B 

3121A 

3121D 

3121F 

3121G 

3122B 

3124F 

3125B 

3125C 

3126E 

3127G 

3128B 

3129A 

3129E 

3129G 

3132A 

3133F 

3135A 

3136A 

3136B 

6 

Gray quartzite 

Chloritic schist 

Gray quartzite 

Gray quartzite with 

sulfides 

Gray quartzite 

(iron stained) 

Calc-silicate 

Gray quartzite with 

sulfides 

Granite 

Chloritic schist 

(hornfelsed) 

Mafic schist 

Dike 

Gray-brown quartzite 

Dike with sulfides 

Quartzite· 

(iron stained) 

Chloritic schist 

Gray quartzite 

Gray quartzite 

Felsic dike with 

sulfides 

Felsic dike 

(iron stained) 

Granite 

Calcareous quartzite 

with sulfides 

Calc-silicate 

Quartzite with 

sulfides 

Mafic schist 

Calc-silicate with 

sulfides 

Black biotite schist 

with sulfides 

Felsic dike 

Ch1oritic schist 

Black biotite schist 

Gray quartzite 

Quartz vein with 

sulfides 

Dark gray-green 

2.0 

7.0 

1.5 

3.0 

s.o 

2.0 

s.o 

1.5 

s.o 

s.o 

s.o 

1.5 

2.0 

1.5 

3 .o 

1.5 

1.0 

1.0 

1.0 

1.5 

• 7 

1.0 

1.5 

5.0 

s.o 

s.o 

1.0 

s.o 

s.o 

1.5 

5.0 

quartzite with sulfides 10.0 

Calc-silicate with 

sulfides 

Black biotite schist 

Felsic dike 

Gray quartzite 

Calc-silicate with 

sulfides 

Black biotite schist 

with sulfides 

Black biotite schist 

Blue-gray quartzite 

Granite 

Black biotite schist 

with sulfides 

Gray quartzite 

Black biotite schist 

White quartzite 

Quartz veins 

(breccia?) 

Black biotite schist 

Gray quartzite with 

tourmaline 

Gray quartzite 

Black biotite schist 

Calc-silicate with 

sulfides 

Calc-silicate with 

sulfides 

1.5 

7.0 

• 7 

1.0 

10.0 

s.o 

3.0 

s.o 

1.5 

5.0 

3.0 

1.5 

• 7 

1.5 

2.0 

2.0 

1.5 

s.o 

10.0 

7 .o 

Mg 

1.00 

2.00 

• 20 

.30 

2.00 

5 .oo 

2.00 

3.00 

.10 

3.00 

2.00 

• 70 

1.00 

.07 

1.00 

.20 

.15 

.10 

.07 

.30 

.15 

.30 

.so 

s.oo 

2.00 

1.50 

.10 

3.00 

2 .oo 

• 70 

s.oci 

7 .oo 

10.00 

3. 00 

.20 

.20 

1.00 

1.50 

1.00 

2.00 

• 30 

1.50 

l. 50 

.so 

.30 

.30 

.70 

.so 

.30 

3.00 

5 .oo 

3.00 

Ca 

o.so 

1.50 

.05 

.20 

s.oo 

10.00 

2.00 

• 30 

.20 

7.00 

.20 

• 70 

.30 

.051 

.07 

.07 

• 50 

. 15 

.051 

• 20 

3.00 

.so 

• 70 

7 .oo 

.so 

1.00 

.15 

7.00 

.15 

1.50 

10.00 

10.00 

15.00 

5. 00 

.15 

.15 

10.00 

2.00 

.15 

2.00 

.20 

Ti 

0.200 

• 700 

.100 

.200 

.soo 

.050 

.300 

.100 

.500 

.700 

.500 

.100 

.150 

.050 

.300 

.070 

.070 

.030 

.020 

.100 

.070 

.100 

.150 

.700 

.500 

.500 

.020 

.500 

.700 

.200 

1.000 

Mn 

300 

700 

200 

300 

1,500 

2,000 

1,000 

300 

500 

1 '000 

500 

300 

300 

100 

300 

200 

300 

200 

200 

300 

300 

200 

500 

1,500 

700 

500 

200 

1,500 

200 

500 

s,ooo 

1.000 2 '000 

.050 1,000 

1.000 1' 500 

.015 150 

.100 200 

.070 S,OOOG 

• 700 300 

1.000 500 

.700 2,000 

.070 200 

3.00 1.000 1,500 

• 07 • 500 500 

.30 .100 300 

.20 .200 300 

.051 .150 300 

.20 .150 300 

.15 .200 500 

.15 .150 300 

.30 • 700 500 

10.00 .100 5,000G 

10.00 .150 5 ,OOOG 

Ag 

0.5N 

.SN 

.5N 

.s 

.51 

.SN 

.51 

.SN 

.51 

.51 

.51 

.SN 

.s 

.51 

.SN 

.51 

.51 

1.0 

As 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

1.5 200N 

.SN 200N 

.51 200N 

.51 200N 

.51 200N 

.5 200N 

.51 200N 

2.0 10,000G 

.51 700 

.51 200N 

1.0 200N 

.SN 200N 

0.51 200N 

.51 200N 

.SN 200N 

.51 200N 

1. 5 200N 

.SN 200N 

.51 200N 

1.51 10,000 

.SN 200N 

.SN 200N 

.5 200N 

.51 

.SN 

.51 

.SN 

.SN 

.51 

1.0 

.SN 

.51 

.SN 

.SN 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200 

200N 

200N 

B 

30 

500 

20 

10 

10 

70 

101 

30 

70 

101 

70 

50 

30 

20 

100 

50 

30 

30 

30 

70 

20 

30 

15 

10 

70 

200 

70 

15 

2 ,OOOG 

300 

20 

10 

Ba 

201 

500 

150 

50 

50 

20N 

30 

500 

150 

100 

300 

700 

1,500 

70 

700 

100 

500 

150 

150 

300 

300 

150 

200 

150 

300 

300 

300 

100 

70 

300 

500 

300 

100 201 

20 50 

70 30 

10N 200 

10 50 

1 '500 300 

100 3,000 

20 100 

30 1 '500 

15 

70 

150 

20 

15 

20 

2,000 

30 

150 

101 

101 

150 

1,000 

300 

300 

300 

200 

500 

300 

1,000 

20 

100 

Be 

101 

15 

10 

101 

15 

101 

101 

50 

10 

101 

20 

20 

30 

10 

30 

101 

101 

70 

30 

150 

10 

10 

10 

101 

15 

20 

150 

15 

50 

20 

30 

10 

1.01 

1.01 

1.5 

1.01 

10 .o 

1.5 

1.5 

1.01 

3 .o 

1.0 

2 .o 

7.0 

1.0 

1.0 

1.0 

2.0 

1.0 

2.0 

3.0 

3.0 

Bi 

10N 

10N 

10N 

10N 

10N 

10N 

lON 

10N 

10N 

10N 

lON 

10N 

10N 

10N 

10N 

10N 

10N 

101 

101 

10N 

lON 

lON 

10N 

10N 

10N 

15 

10N 

10N 

10N 

10N 

10N 

10N 

20 

10N 

10N 

10N 

15 

50 

10N 

101 

15 

20 

101 

10N 

10N 

10N 

101 

101 

10N 

10N 

10N 

10N 

Co 

15 

50 

7 

10 

30 

5 

30 

5 

30 

50 

50 

5 

10 

15 

50 

7 

30 

50 

50 

50 

5 

50 

30 

20 

30 

70 

5 

30 

5 

30 

70 

20 

30 

5 

30 

30 

51 

10 

7 

50 

30 

20 
Cr 

100 

500 

30 

70 

50 

15 

200 

20 

150 

100 

300 

70 

100 

10 

200 

30 

30 

!ON 

lON 

50 

10 

20 

70 

300 

300 

150 

lON 

70 

300 

100 

50 

70 

20 

500 

lON 

20 

70 

300 

500 

300 

30 

500 

300 

70 

20 

30 

70 

50 

50 

300 

70 

200 

Cu 

20 

200 

20 

300 

300 

15 

so 

7 

30 

100 

200 

5 

20 

20 

10 

SL 

SL 

20 

10 

15 

50 

150 

70 

300 

7 

500 

50 

10 

300 

70 

700 

150 

300 

100 

150 

15 

200 

100 

7 

SL 

700 

50 

10 

500 

70 

30 

La Mo 

20L SN 

70 SN 

20 SN 

20 SN 

20L SN 

20L SN 

20N SN 

30 SN 

20L SN 

20 SN 

70 SN 

100 SN 

100 SN 

20 SN 

70 SN 

20L SN 

30 SN 

50 SN 

20 SN 

50 15 

20N SN 

50 SN 

20 SN 

20L 15 

30 SN 

50 

20 

20 

200 

50 

SN 

SN 

SN 

SN 

SN 

30 SN 

20 SN 

20L SN 

50 SK 

50 SN 

30 SK 

20L SN 

100 SN 

150 SN 

20 SK 

100 200 

50 SN 

70 SN 

70 5 

20N SN 

20L SN 

20 SN 

50 SN 

30 SN 

70 SN 

50 SN 

100 SN 

Nb 

20N 

20L 

20N 

20N 

20N 

20N 

20N 

20L 

20N 

20N 

20L 

20L 

20 

20N 

20L 

20N 

20N 

30 

30 

20L 

20N 

20N 

20N 

20N 

201 

20L 

30 

20N 

20L 

20N 

20N 

20N 

20N 

20L 

30 

20N 

20N 

20L 

201 

20N 

201 

20N 

20L 

20N 

20N 

20N 

20N 

20N 

20N 

20L 

20L 

20 

Ni Pb 

30 lON 

70 30 

20 lON 

30 lON 

30 lON 

5 lOL 

30 lOL 

10 20 

50 10 

70 lOL 

70 30 

30 lON 

30 50 

50 lON 

20 50 

70 lOL 

15 lON 

50 

50 

30 lON 

10 lOL 

20 lON 

50 lON 

70 lOL 

70 30 

70 

7 

50 

70 

50 

10 

30 

lOL 

70 

lOL 

50 lOL 

70 15 

15 lOL 

50 lOL 

5 50 

10 lON 

30 lON 

70 20 

70 30 

70 lOL 

10 70 

70 lON 

70 30 

30 20 

lON 

30 lON 

15 lON 

15 20 

20 10 

70 30 

50 lON 

30 lON 

Sb Sc Sn 

lOON 20 lON 

lOON 70 10 

lOON lON 

lOON 20 lON 

lOON 50 50 

lOON SL lON 

lOON 70 lON 

lOON lON 

lOON 30 lON 

lOON 100 lOL 

lOON 70 lQN 

lOON 10 lON 

lOON 15 lON 

lOON SL lON 

lOON 30 lON 

lOON 5 lON 

lOON 5 lON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

lOON 

50 

SL 50 

10 14 

SL lON 

5 lON 

15 lON 

70 20 

70 20 

50 

SL 

70 

70 

30 

lON 

50 

70 

70 

lON 

50 30 

50 20 

30 

70 30 

5N 50 

SL lON 

50 100 

70 30 

70 lON 

50 30 

5 lON 

70 30 

50 lON 

10 lON 

5 lON 

70 lON 

15 lON 

7 lON 

10 lON 

70 lON 

15 100 

30 70 

Sr 

lOOL 

300 

lOOL 

100 

300 

100 

lOON 

200 

lOON 

300 

100 

150 

500 

lOON 

150 

lOON 

200 

lOON 

lOON 

150 

300 

100 

150 

150 

150 

300 

lOON 

300 

50 

300 

700 

200 

300 

300 

lOON 

lOOL 

100 

300 

300 

100 

200 

lOU 

lOOL 

150 

1001 

lOON 

lOOL 

lOOL 

100 

lOOL 

100 

700 

v 

150 

300 

50 

lOU 

200 

50 

200 

50 

200 

500 

300 

100 

150 

lOL 

150 

70 

50 

lON 

lON 

lOU 

20 

70 

150 

500 

300 

200 

15 

500 

300 

150 

200 

300 

100 

300 

lON 

70 

200 

300 

500 

500 

70 

300 

200 

150 

20 

70 

150 

70 

70 

300 

100 

150 

w 

SON 

SOL 

SON 

SON 

SON 

SOL 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SOL 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

50 

SON 

SON 

SOL 

SON 

SON 

SON 

70 

SOL 

SON 

SON 

150 

50 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SOL 

SON 

SON 

SON 

SON 

500 

50 

Y Zn 

20 200N 

50 200N 

lOL 200N 

20 200N 

30 200N 

lOL 200N 

20 200N 

15 200N 

20 200N 

50 200L 

50 200L 

20 200N 

30 200L 

30 2001 

30 200L 

15 200N 

15 200N 

100 

70 

30 

10 

20 

20 

50 

30 

30 

70 

30 

100 

30 

30 

50 

10 

30 

100 

10 

50 

70 

100 

30 

20 

30 

50 

15 

10 

20 

20 

20 

20 

70 

30 

50 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200 

200L 

200N 

200N 

2001 

200N 

200N 

200N 

200N 

200L 

200N 

200N 

300 

200N 

200N 

200N 

500 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200L 

500 

300 

Zr Au 

150 O.OSN 

150 .OSN 

150 .OSN 

100 .OSN 

70 .OSN 

lON .OSN 

70 .OSN 

100 .OSN 

150 .OSN 

70 .OSN 

150 .OSN 

150 • OS N 

200 .OSN 

70 .OSN 

l 00 .OSN 

150 .OSN 

150 .OSN 

100 

100 

100 

150 

150 

150 

100 

150 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.os 

.OSN 

.OSN 

150 140.00 

100 .25 

70 .OSN 

150 .USN 

150 .OSN 

70 .OSN 

100 .USN 

15 .OSN 

200 .OSN 

100 .OSN 

200 • OSN 

100 .OSN 

150 40 .oo 300 • 05 

200 .OSN 

70 • OS N 

200 .10 

150 .OSN 

150 .OSN 

200 .OSN 

200 .OSN 

100 .OSN 

500 .OSN 

150 .OSN 

150 .OSN 

100 .OSN 

150 .OSN 

7 
Table 1. Analytical data of rocks from the Table Mountain area-Continued 

Station 

number and 

sample letter 

3136C 

3136F 

3136H 

3137D 

3139C 

3139D 

3139E 

3l39J 

3140I 

3145C 

3145E 

3146D 

3147B 

3148B 

3148C 

3148D 

3148E 

3148F 

3149B 

3150D 

3150G 

3150H 

3150I 

3150K 

3151C 

3152E 

0044B 

44A 

44B 

44C 

44D 

Rock 

description 

Calc-silicate with 

sulfides 

Calc-silicate 

Calc-silicate 

Gray quartzite with 

sulfides 

Breccia 

(iron stained) 

Black biotite schist 

with sulfides 

Gray quartzite with 

sulfides 

Gray quartzite with 

sulfides 

Black biotite schist 

with quartz vein 

and sulfides 

Gray quartzite with 

vein 

Black biotite schist 

Gray quartzite 

Black biotite schist 

Intermediate dike 

Intermediate dike 

Intermediate dike 

Intermediate dike 

Granite 

Granite 

Quartzite 

Calc-silicate 

Calc-silicate with 

sulfides 

Calc-silic?te with 

sulfides 

Calc-silicate 

Blue-green quartzite 

Chloritic quartzite 

Calc-silicate 

Felsic dike 

Gray quartz 

(iron stained) 

Calc-silicate with 

sulfides 

Calc-silicate with 

sulfides 

Fe 

10.0 

s.o 

1.0 

5 .o 

1.5 

7.0 

3.0 

3.0 

s.o 

2.0 

s.o 

3.0 

3 .o 

1.5 

5.0 

s.o 

3.0 

10.0 

1.5 

1.5 

15.0 

5.0 

7 .o 

7.0 

1.5 

3.0 

10.0 

1.0 

3.0 

10.0 

5.0 

Mg 

5.00 

l. 50 

l. 50 

2.00 

• 30 

3.00 

1.00 

1.00 

2.00 

.so 

1.50 

1.00 

1.50 

.70 

5.00 

5.00 

1.50 

.02 

.30 

.so 

1.50 

1.50 

1.50 

2.00 

.30 

1.50 

1.00 

.15 

• 70 

l.OO 

Ca 

10.00 

15 .oo 20.00 

7 .oo 

.15 

• 70 

1.00 

3.00 

.20 

.10 

.07 

.10 

.15 

.so 

s.oo 

s.oo 

3 .oo 

.05L 

.as 

1.00 

10.00 

10.00 

15.00 

s.oo 

.20 

5 .oo 15.00 

.as 

1.00 

15.00 

3.00 10.00 

both liquid- and vapor-rich fluid inclusions. Sample 311 

is white and clear quartz from the vein. The sample 

contains both vapor-rich and liquid-rich fluid 

inclusions. Salinities of fluid inclusions range from 0 

to 9.9-weight-percent NaCl equivalent; most are from 

3 to 7 percent. Heating data are shown separately in 

histograms (fig. 5). 

The histograms for the homogenization 

temperatures are strongly unimodal for all three 

samples and the modal temperature of the type I 

inclusions is approximately equal in all three samples 

(sample 311, 265 °C; sample 31J"', 255 °C; and sample 

31L', 275 °C). Homogenization temperatures for type 

II inclusions, in samples 311 and 31J'", range from 260 

to 380 °C--values which coincide with homogenization 

temperatures for the upper half of type I inclusions 

(see fig. 5). The majority of the homogenization 

temperatures for type II inclusions range from 320 to 

380 °C. Because type II and some type I inclusions 

occur together and appear to have formed at the same 

time, we interpret the data as recording the cooling of 

8 

Ti Mn 

0.100 5 ,OOOG 

.100 5,000 

.070 500 

.200 3,000 

• 070 200 

• 700 2 '000 

.sao 700 

.300 1 '000 

.700 1,000 

.150 

.700 

.soo 

• 500 

.300 

.700 

• 700 

• 700 

.070 

.070 

.200 

.300 

.300 

• 700 

1.000 

.150 

.200 

.soo 

.020 

.200 

.150 

300 

500 

500 

700 

300 

700 

l ,ooo 

500 

15 

200 

500 

5 ,OOOG 

5,000 

5 ,OOOG 

5, OOOG 

300 

1,000 

5 ,OOOG 

500 

500 

s,ooo 

• 700 3 ,ooo 

Ag 

O.SN 

.SN 

.SN 

• 5 

.SL 

.SL 

.5L 

.SN 

.5L 

.5 

.SL 

.SL 

.SN 

.SN 

.SN 

.SL 

.5 

2.0 

1.0 

.SN 

.5L 

.SL 

.SN 

.SN 

.SN 

.5N 

1.0 

.s 

.5N 

.SN 

As 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

10,000G 

1,000 

300 

200 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

200N 

B 

10L 

lOL 

!ON 

20 

10N 

150 

20 

15 

70 

70 

100 

30 

1 ,ooo 30 

10 

10 

20 

10L 

30 

20 

20 

15 

10 

lOL 

15 

20 

lOL 

15 

20 

20 

30 

Ba 

20N 

70 

100 

100 

150 

500 

70 

30 

500 

300 

700 

1,000 

1,500 

1,000 

1,000 

700 

1,500 

100 

700 

70 

100 

20L 

so 

70 

100 

30 

20L 

70 

200 

20L 

100 

Be 

s.o 

1.5 

l.OL 

1.0 

1.5 

1.0 

l.OL 

1.0 

1.5 

1.0 

2.0 

2.0 

3.0 

2.0 

l.OL 

1.0 

3.0 

1.5 

2.0 

l.OL70.0 

7.0 

7.0 

7.0 

1.0 

l.OL 

s.o 

15.0 

1.5 

7 .o 

20 .o 

Bi 

10N 

!ON 

10N 

lON 

!ON 

Co 

30 

20 

5 

30 

10N 50 

20 

20 

lON 

!ON 

!ON 

10N 

10N 

!ON 

10N 

10N 

10N 

20 

10N 

10N 

30 

10L 

!ON 

10N 

10N 

10N 

50 

lOL 

!ON 

30 

lOL 

30 

30 

20 

30 

20 

20 

10 

50 

30 

20 

30 

5 

10 

30 

20 

20 

20 

10 

20 

7 

5L 

50 

15 

20 

an initially boiling aqueous fluid. Boiling appears to 

have begun at about 370 °C and continued as the 

system cooled to about 320 °C. Because type I 

inclusions are more common in the samples than type 

II inclusions, it appears that most of the vapor phase 

was lost during boiling. Most of the type I inclusions 

were trapped below 320 °C when the fluid probably 

was a liquid. The presence in sample 311 of type II 

inclusions that have homogenization temperatures 

below 320 °c are interpreted as being the result of 

measurement errors that can result from difficulties in 

observing the exact temperature at which liquid 

homogenizes in vapor-rich fluid inclusions (see Bodnar 

and others, 1985, p. 1867). Assuming that the quartz 

vein was open to the surface (that is, the pressure was 

hydrostatic) and the fluid was boiling throughout the 

fluid column, the temperature-depth relationship of 

Haas (1971) may be used to calculate the depth of 

formation of the vein. A fluid with a salinity of 5-

weight-percent NaCl and a temperature of 320 to 

370 °C will boil at depths less than 1,400 to 2,400 m. 
Cr 

150 

100 

30 

70 

30 

500 

100 

100 

300 

50 

200 

100 

300 

150 

700 

700 

500 

30 

30 

70 

100 

200 

300 

200 

70 

200 

20 

101 

30 

70 

200 

Cu 

100 

10 

10 

500 

50 

300 

300 

200 

300 

30 

70 

51 

15 

10 

20 

20 

20 

51 

15 

7 

500 

100 

300 

200 

20 

51 

200 

51 

700 

30 

100 

La 

70 

70 

20N 

30 

20N 

70 

20 

30 

100 

20 

70 

70 

150 

100 

50 

50 

100 

20 

201 

20 

50 

100 

100 

200 

20 

201 

20N 

30 

30 

50 

50 

Mo 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

10 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

SN 

Nb 

201 

301 

20N 

20N 

20N 

201 

20N 

20N 

201 

20N 

201 

201 

201 

201 

201 

201 

201 

201 

201 

20N 

201 

201 

20 

50 

20N 

20N 

20N 

30 

20N 

201 

20 

Ni Pb 

50 lON 

20 101 

5 20 

30 lON 

15 lON 

70 30 

50 lON 

30 ION 

70 30 

50 50 

50 30 

50 10 

50 30 

5 50 

20 15 

15 20 

10 50 

51 150 

7 70 

30 lON 

30 101 

50 101 

30 101 

15 101 

30 10N 

70 101 

20 20N 

15 

50 101 

20 101 

70 101 

Occurrences in and Adjacent to the Granite 

Sb Sc 

lOON 20 

lOON 15 

lOON 51 

lOON 50 

lOON 10 

lOON 70 

lOON 30 

lOON 30 

lOON 70 

lOON 15 

lOON 50 

lOON 30 

1 OON 50 

lOON 15 

lOON 70 

lOON 50 

lOON 30 

100 10 

1 OON 10 

lOON 15 

lOON 20 

lOON 50 

lOON 50 

lOON 70 

lOON 10 

lOON 30 

lOON 51 

lOON 51 

lOON 

lOON 

lOON 20 

Measurements were made on three samples from 

occurrences in and adjacent to the granite. Sample 

33B is a porphyritic felsic dike with phenocrysts of 

potassium feldspar, rounded quartz, and altered 

plagioclase set in a chloritic groundmass. The quartz 

phenocrysts contain liquid-rich fluid inclusions. 

Sample 032C is a sample of yellow-stained, porphyritic 

felsic dike that contains mostly small liquid-rich fluid 

inclusions. One or two vapor-rich inclusions were 

observed, and in one case a liquid-rich fluid-inclusion 

contains a daughter mineral (fig. 3 E). Sample 82380-2-

1 is a sample of a felsic dike. Salinities for these 

samples range from 0.2- to 8.0-weight-percent NaCl 

equivalent, but most are lower than 2 percent. 

Heating data are shown as histograms (fig. 6). The 

histograms for the three samples are bimodal. The 

lower mode in two of the samples occurs at about 275 

°C; the lower mode in the third sample occurs at about 

265 °C. The upper modes occur at 355, 315 and 295 

Sn Sr 

100 100 

150 100 

lON 1,000 

lON 300 

lON lOON 

101 1001 

lON 1001 

15 1001 

lON 1001 

lON 

10N 

lON 

50 

10 

10N 

10N 

10N 

50 

10N 

10N 

150 

150 

150 

150 

10N 

10N 

150 

50 

10 

150 

100 

1001 

1001 

150 

200 

150 

500 

300 

300 

100 

100 

100 

300 

300 

300 

lOON 

100 

100 

200 

lOON 

200 

1001 

700 

v 

100 

150 

70 

150 

70 

500 

200 

150 

300 

100 

200 

150 

200 

100 

200 

200 

150 

50 

70 

100 

150 

150 

150 

100 

100 

200 

200 

101 

30 

50 

200 

w 

300 

SOL 

SON 

SON 

SOL 

SON 

SON 

SOL 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SOL 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SON 

SOL 

SON 

Y Zn 

50 700 

30 300 

15 200N 

30 200N 

10N 200N 

70 2001 

20 200N 

20 200N 

50 2001 

20 

50 

30 

70 

50 

50 

50 

50 

10 

20 

15 

30 

30 

50 

50 

30 

20 

15 

100 

30 

15 

50 

2001 

2001 

200N 

2001 

200N 

2001 

2001 

2001 

200N 

200 

200N 

300 

300 

300 

200 

200N 

200N 

500 

200N 

200N 

300 

200 

Zr Au 

150 0.051 

150 .OSN 

70 .OSN 

100 .OSN 

50 .OS N 

200 .OSN 

150 .os 

100 .20 

200 .051 

150 

200 

200 

150 

200 

150 

150 

200 

70 

70 

100 

150 

150 

200 

500 

150 

150 

100 

150 

30 

100 

200 

.OSN 

.USN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.20 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

.OSN 

0 c in the three samples studied using the heatingfreezing stage. The data indicate that fluids were 

trapped at two temperatures, the lower of which was 

similar to that of type I inclusions in the quartz vein. 

Crushing Experiments 

A crushing stage was used to investigate the 

noncondensible gases in the fluid inclusions (Roedder, 

1970; 1984). In a first test, materials from the six 

samples examined in the heating and cooling 

experiments were crushed in an immersion oil 

(nD=1.515) mounting fluid. Upon crushing, gases were 

liberated from the fluid inclusions and formed bubbles 

in the oil. The gas bubbles moved into the liquid at 

moderate speeds. This test indicates that the vapor 

phase of the inclusions contains a noncondensible gas 

in addition to water vapor, and that the pressures 

inside the fluid inclusions are considerably above 1 

atmosphere but are not so high as to cause the gases to 

9 
Table 2. Analytical data of rocks from stations 31. 32, and 33 in the Table Mountain area collected in 1983 

[Analysis of Au by atomic absorption; all other analyses by six-step semiquantitative emission spectrographic 

methods. Fe, Mg, Ca, and Ti in percent; all others in parts per million. G, greater than the amount listed; L, less 

than amount listed; N, not detected at amount listed. Analyst R.M. O'Leary ] 

Station Rock description Fe Mg Ca Ti 

number and 

sample letter 

31A Felsic dike 0.7 0.10 0.20 0.030 

31B Breccia 

(iron stained) • 7 • 50 .OSL .100 

31C Breccia from near 

felsic dike l.O .70 s.oo .100 

31D Breccia with 

gray material s.o 2.00 15.00 .200 

31E Arsenopyrite-bearing 

vein 7.0 2.00 .so .500 

31H Arsenopyrite-bearing 

vein 1.5 .20 .20 .100 

32A Felsic dike with 

sulfides 1.0 .20 .os .100 

32B Equigranular granite 

with sulfides 

(adjacent to 32A) l.O .so .20 .100 

32C Felsic dike • 7 .20 .os • 0 70 

32D Granite porphyry witt 

fine-grained 

groundmass l.O • 70 • 70 .150 

32E Quartzite s.o l. 50 .07 .500 

33A Altered intermediate 

dike 3.0 3 .oo 3.00 • 700 

33B Porphyritic intermediate dike 2.0 l. 50 • 70 .30 

be expelled explosively. In order to determine if 

carbon dioxide is in the vapor phase of the fluid 

inclusions, a 10 percent barium chloride solution was 

used as a mounting fluid. Upon crushing, some of the 

vapor bubbles that were expelled from the fluid 

inclusions dissolved immediately into the barium 

chloride solution. When the mounting fluid was 

acidified by the addition of dilute hydrochloric acid, 

the bubbles that were expelled from the fluid 

inclusions did not disappear. The results indicate that 

carbon dioxide is present but distributed unevenly in 

the vapor phase of the fluid inclusions (see Roedder, 

1984, p. 212-219). However, carbon dioxide probably is 

not present in sufficient amounts to form a separate 

liquid carbon dioxide phase. The presence of the 

carbon dioxide in the fluids associated with 

mineralization calls into question depth estimates 

using a boiling NaCl-H2o fluid (see Roedder, 1984). 

Nevertheless, based on geologic relations, the 

approximate depths calculated by the methods 

described by Haas (1971) are probably a good estimate 

for mineralization in the Table Mountain area. 

DISCUSSION 

The available data on the field relations, traceelement geochemistry, mineralogy, and fluid inclusions 

suggest (1) these occurrences, like other low-sulfide 

gold deposits and occurrences (see Boyle, 1979, p. 279-

290), have simple mineralogies that are associated 

with low-saline fluids having sulfur fugacities within 

the stability field of pyrrhotite; (2) the occurrences 

formed at moderate temperatures, and the fluids 

boiled; (3) the occurrences formed at relatively 

10 

Mn Ag As B Ba Be Bi Co 

700 1.5 200N 50 70 10 10N SN 

200 .s 200N 50 150 ION SL 

1,000 .SN 200N 20 150 10N 

2,000 .SN 200N 10L 20 10N 10 

500 l.O 10,000 100 200 10L 50 

200 l.O 10,000G 50 30 10N 10 

150 7.0 200N 15 1,000 50 SN 

300 • 7 200N 20 700 7 10 SN 

200 .SN 200N 20 500 10 10N SN 

700 .SN 200N 20 1,000 7 N 5 

700 .SN 200N 150 500 2 N 15 

1,000 .SN 200N 10L 1,000 N 30 

1,000 .SN 200N 10L 1,500 N 10 

shallow depths; (4) the occurrences formed in an active 

tectonic environment; and (5) occurrences similar to 

these may have been the sources of placer gold in the 

Circle quadrangle. 

The mineralogy and geochemistry of the 

occurrences near Table Mountain, as well as in and 

adjacent to the granite, are similar to other lowsulfide quartz vein deposits. The most common 

sulfides are arsenopyrite and pyrrhotite; minor sulfides 

and sulfosalts include enargite, chalcopyrite and 

sphalerite. Gold is associated with arsenic and is more 

abundant than silver. Studies of fluid inclusions 

suggest the fluids that deposited the metals were low 

salinity ( 10-weight-percent NaCl equivalent); the 

presence of pyrrhotite instead of pyrite constrains the 

sulfur fugacity of the fluid. 

The occurrences formed at moderate 

temperatures and in part from fluids that boiled. 

Boiling is indicated by the presence of cogenetic 

liquid-rich and vapor-rich fluid inclusions in the quartz 

vein west of Table Mountain (station 31, fig. 4). The 

majority of filling temperatures of vapor-rich 

inclusions from this occurrence are from 320 to 380 

°C. The average filling temperatures of liquid-rich 

fluid inclusions from this occurrence are from 255 to 

27 5 °C. Together, the fluid inclusions appear to 

record a cooling of fluids in the vein that was 

accompanied by the deposition of sulfides and quartz. 

Samples from occurrences in and adjacent to the 

granite (station 32, 33, and 82380-2) do not contain 

vapor-rich fluid inclusions. Filling temperatures of 

liquid-rich fluid inclusions from samples of felsic dikes 

are bimodal. The upper temperature mode varies with 

the sample. The lower mode in the samples ranges 

from 265 to 275 °C, temperatures similar to those for 

samples of the quartz vein from near Table Mountain. 
Cr Cu La Mo Nb Ni Pb Sb 

lON 51 50 SN 70 50 lOON 

10 20N 30 15 50 lOON 

15 10 20N SN 20N 20 lON lOON 

50 15 20N 15 20N 30 15 lOON 

100 500 20N SN 20N 70 15 1001 

15 150 20N SN 20N 20 10 1001 

10 70 20N 20 20N 30 lOON 

15 51 30 20N 5 50 lOON 

101 51 20N 15 20N 5 30 lOON 

20 50 SN 30 10 30 lOON 

100 20 50 SN 20 30 20 lOON 

200 70 SN 20 10 30 lOON 

50 100 SN 30 10 50 lOON 

The inference that the occurrence formed at 

shallow depth is supported by two pieces of evidence: 

(1) using the method of Haas (1971), a fluid with a 

salinity of 5 weight percent and a temperature of 320 

to 380 °C will boil at a depth of 1,400 to 2,400 m if it 

is open to the surface. (2) The presence of detectable 

gold in felsic dikes (station 32, 3103 and 31) and the 

presence of arsenopyrite in the granite adjacent to a 

felsic dike (station 32) suggests involvement of the 

dikes in the hydrothermal activity. The textures of 

the dikes suggest that they crystallized in a shallow 

environment. 

The inference that the occurrences formed in the 

active tectonic environment that accompanied the late 

stages of the felsic igneous activity is supported by 

field relations, including probable movement on the 

Swamp Saddle fault. Differences in postulated depth 

of formation of the contact metamorphic effects and 

of the quartz vein west of Table Mountain provide 

additional evidence of tectonic activity. 

Gold occurrences west of Table Mountain 

(stations 3095, 3122 and 31) suggest control by the 

adjacent fault. The presence of tourmaline in the 

fault zone and in gold-bearing samples adjacent to the 

fault (stations 3095 and 3122),as well as locally from 

the outer walls of the quartz vein (station 31), links 

the fault and the gold-bearing samples. 

The difference between the estimated depth of 

formation of the contact effects related to the 

intrusion of the granite (6 km), and the depth of 

formation of the quartz vein west of the Table 

Mountain as estimated from the method used by Haas 

(1971) (1.4 - 2.4 km), implies substantial regional 

uplift. The time period over which the uplift took 

place is uncertain, because neither the granite nor the 

felsic dikes that are associated with the gold 

Sc Sn Sr v w y Zn Zr Au 

SN 50 lOON 101 SON 150 200N 100 O.OSN 

15 lOON 70 SON 50 200N 70 .OSN 

ION lOON 70 SON 20 200N 50 .OSN 

10 ION l ,000 150 SOL 50 200N 70 .OSN 

20 lON lOON 200 SOL 20 200N 150 2.60 

10N lOON 100 SOL lON 200 30 12.60 

20 lOON 50 SON lON 200N 70 .051 

5 10 100 50 SON 30 200N 100 .OSN 

SN 101 1001 20 SON 50 200 50 .USN 

7 

20 

30 

10 200 70 SON 50 N 100 .OSN 

lON lOON 150 SON 100 N 200 .OSN 

lON 300 150 SON 70 N 150 .OSN 

10 lOON 50 SON 70 N 200 .OSN 

occurrences have been dated successfully. However, 

similar plutons in the northwest Circle quadrangle 

have yielded ages between 66 and 57 m.y. B.P. (Wilson 

and Shew, 1981). Felsic dikes and hypabyssal rocks 

similar to those in the Table Mountain area exist in or 

adjacent to other plutons in the region. The only 

occurrence of similar rocks that are not closely 

associated with a pluton occur in the Faith Creek area, 

where they occur along the trend of an aeromagnetic 

low that also underlies the Table Mountain area. 

These relationships suggest that the felsic dikes and 

hypabyssal rocks are comagmatic with the granite and 

place some constraints upon the time period over 

which the uplift took place. Thus it seems reasonable 

to suggest that the Table Mountain area was being 

uplifted at a rate of 3.6 to 4.6 km per 10 m.y. just 

before the start of the hydrothermal activity that 

formed the gold occurrences. This rate of uplift can 

be compared with the rate of 6 km in 60 m.y. that 

Forbes and Turner (197 5) calculated for the Yukon 

Tanana Upland on the basis of argon-blocking 

temperatures in biotite. 

The Swamp Saddle fault, which offsets regional 

metamorphic isograds about 8 km (Foster and others, 

1983) and offsets dike rocks from the pluton, probably 

was a major locus of tectonic activity in the Table 

Mountain area. 

The possibility that occurrences such as those 

west of Table Mountain (stations 3095, 3122 and 31) 

might act as sources of gold elsewhere in the Circle 

quadrangle is probably best assessed by estimating the 

amount of gold in the occurrences. If the quartz vein 

at station 31 does underlie the small hill on the w~st 

end of the ridge (an area of approximately 0.1 km ), 

averages 3.75 em in thickness, and has an average gold 

content of 7 ppm, it would contain over 1,400 oz of 

11 
A 

I Two inclusions 

180 220 260 300 340 380 

B 

180 220 260 300 340 380 420 

c 

140 180 220 260 300 340 380 

TEMPERATURE, IN DEGREES CELSIUS 

Figure 5. Histograms of homogenization temperatures 

of fluid inclusions from samples from Table Mountain 

occurrence. Open area, data for type I inclusion; area 

with dot. type II inclusion. A, Sample 311. B. Sample 

31J. C, Sample 31L. - -

12 

A 

I Two inclusions 

220 260 300 340 380 

220 260 300 340 380 

220 260 300 340 

TEMPERATURE, IN DEGREES CELSIUS 

Figure 6. Histograms of homogenization temperatures 

of fluid inclusions from samples from occurrences in 

and adjacent to the granite. All data are for type I 

inclusions. A, Sample 32C. !!_. Sample 33B. C. Sample 

82380-2-1. 

gold. Such a figure is probably a conservative 

estimate of the gold available in the area west of 

Table Mountain, because it neglects gold from the 

black biotite schist adjacent to the fault and does not 

consider the possibility of additional veins beneath the 

hill. Although the occurrence does not contain a large 

amount of gold, especially when compared to that 

mined in the Circle quadrangle, it seems likely that 

there were many similar occurrences within the 

quadrangle. Thus, much of the gold in the Circle 

quadrangle probably was derived from small local gold 

occurrences that are characterized by a simple 

mineralogy, and formed at shallow depths in and 

adjacent to faults that were active during the last 

stages of felsic igneous activity. 
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Bodnar, R.J., Burnham, C. W., and Sterner, S.M., 1985, 

Synthetic fluid inclusions in natural quartz. III. 

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the system H20-NaCl to 1000 °C and 1500 bars: 

Geochimica et Cosmochimica Acta, v. 49, p. 

1861-1873. 

Boyle, R. W., 1979, The geochemistry of gold and its 

deposits: Geological Survey of Canada Bulletin 

280, 584 p. 

Bundtzen, T.K., Eakins, G.R., Clough, J.G., Lueck, 

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D.A., 1984, Alaska's Mineral Industry 1983: 

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Burack, A.C., Laird, Jo, Foster, H.L., and Cushing, 

G.W ., 1984, Metamorphic petrology of the Table 

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States Geological Survey in Alaska: 

Accomplishments during 1981: U.S. Geological 

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P· 

Haas, J.L., Jr., 1971, The effect of salinity on the 

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58. 

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219. 

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13 
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