Huston, D.L., Pehrsson, S., Eglington, B.M., and Zaw, K., 2010, The geology and metallogeny of volcanic-hosted massive sulfide 

deposits—Variations through geologic time and with tectonic setting: Economic Geology, v. 105, p. 571–591.

Martin, J.M., and Whitfield, M., 1983, The significance of the river input of chemical elements to the ocean, in Wong, C.S., Boyle, 

E.A., Bruland, K.W., Burton, J.D., and Goldberg, E.D., eds., Trace metals in sea water: New York, Plenum Press, p. 

265–296.

National Oceanic and Atmospheric Administration, 2002, Submarine ring of fire 2002—Explorer ridge—Hydrothermal 

vents and ocean chemistry: NOAA Ocean Explorer, 

http://oceanexplorer.noaa.gov/explorations/02fire/background/vent_chem/media/chemistry.html.

Plumlee, G.S., 1999, The environmental geology of mineral deposits: Society of Economic Geologists, Reviews in 

Economic Geology, v. 6A, p. 71–116.

Rose, A.W., Hawkes, H.E., and Webb, J.S., 1979, Geochemistry in mineral exploration (2nd ed.): Academic Press, London, 

657 p.

U.S. Environmental Protection Agency, 2003, List of drinking water contaminants and MCL’s: U.S. Environmental Protection Agency 

Report EPA 816-F-03-016, June 2003, 6 p.

Alaska Department of Environmental Conservation, 2003, Water quality standards: Alaska Department of Environmental Conservation Report 18-AAC-70, 54 p.

Dusel-Bacon, Cynthia, Alenikoff, J.N., Premo, W.R., Paradis, S., and Lohr-Schmidt, I., 2007, Tectonic setting and metallogenesis of 

volcangenic massive sulfide deposits in the Bonnifield mining district, northern Alaska Range, in Gough, L.P., and Day, W.C., eds., 

Recent U.S. Geological Survey studies in the Tintina gold province, Alaska, United States, and Yukon, Canada—Results of a 

5-year project: U.S. Geological Survey Scientific Investigations Report 2007–5289–B, p. Bi–B8 (33–44).

Eppinger, R.G., Briggs, P.H., Dusel-Bacon, Cynthia, Giles, S.A., Gough, L.P., Hammarstrom, J.M., and Hubbard, B.E., 2007, Environmental geochemistry at Red Mountain, an unmined volcanogenic massive sulfide deposit in the Bonnifield district, Alaska Range, 

east-central Alaska: Geochemistry, Exploration, Environment, Analysis, v. 7, part 3, p. 207–223.

Gilbert, W.G., 1977, General geology of Healy D-1 and Southern Fairbanks A-1 quadrangles, Alaska: Alaska Division of Geological and 

Geohphysical Surveys, Open-File Report 105, plate 1.

Giles, S.A., Eppinger, R.G., Granitto, M., Zelenak, P.P., Adams, M.G., Anthony, M.W., Briggs, P.H., Gough, L.P., Hageman, P.L., 

Hammarstrom, J.M., Horton, J.D., Sutley, S.J., Theodorakos, P.M., and Wolf, R.E., 2007, Geochemical data for stream-sediment, 

surface-water, rock, and vegetation samples from Red Mountain (Dry Creek), an unmined volcanogenic massive sulfide deposit in 

the Bonnifield district, Alaska Range, east-central Alaska: U.S. Geological Survey Data Series 204, 64 p., available on CD–ROM or 

at http://pubs.usgs.gov/ds/2006/204.

Gough, L.P., Eppinger, R.G., Briggs, P.H., and Giles, S.A., 2006, Biogeochemical characterization of an undisturbed highly acidic, 

metal-rich bryophyte habitat, east-central Alaska: Arctic, Antarctic, and Alpine Research, v. 38, no. 4, p. 522–529.

References Cited References Cited

All photographs by Robert G. Eppinger except figure 19, by Larry P. Gough.

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

q

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>228–310

 (>4 x)1

>171–228

 (>3 –4 x)1

>114–171

 (>2–3 x)1

89–114

 (<2 x)1

Sediments (ppm)

Cerium

>8,000–28,000

 (>100,000 x)2

>800–8,000

 (>10k–100k x)2

>80–800

 (>1k–10k x)2

0.014–80

 (<1,000 x)2

Waters (μg/L)

EXPLANATION

Figure 29. Cerium in water and stream sediment samples. Anomalously high cerium from acidic spring 

water exceeds global crustal background >100,000×. pH rise due to mixing waters causes cerium to precipitate in creek sediment, which remains high (>4× background) until confluence with Dry Creek. μg/L = 

micrograms per liter. ppm = parts per million.

1

Crustal background 57 ppm (Rose and others, 1979).

2

Crustal background 0.08 μg/L (Martin and Whitfield, 1983).

1 2 3 4 5 6 7 8 9 10

pH

0.001

0.01

0.1

1

10

100

1,000

10,000

100,000

Cerium, in micrograms per liter

Copahue Volcano, Argentina

Natural, mineralized

Diverse mine drainage

Other Waters n = 300

 (Argentina, Brazil, Canada, 

 Spain, United States)

Upstream of alteration zone

Downstream of alteration zone

Within alteration zone

Red Mountain Waters n = 33

EXPLANATION

Figure 28. Cerium in Red Mountain filtered and acidified water compared to cerium from mine drainage 

and mineralized water from diverse deposit types from the United States, Canada, Brazil, and Spain. Rare 

earth element concentrations in waters from Red Mountain are exceedingly high. Data from Eppinger and 

others (2007). 

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>20,500–58,302 (>100,000)

>10,300–20,500 (>50,000–100,000)

>2,050–10,300 (>10,000–50,000)

>205–2,050 (>1,000–10,000)

>2.05–205 (>10–1,000)

0.019–2.05 (0.09–10)

x Background1

EXPLANATION

Sum REE (μg/L)

q

0 0.5 KILOMETER1

0 0.5 MILE1

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

Figure 27. Sum of rare earth elements (REE) (Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb) in water samples. 

The highest REE sampled in acidic springs exceeds global crustal background by >100,000×. REE elements 

are mobilized by acidic groundwater dissolving accessory minerals, including fluocerite, in the felsic Mystic 

Creek Member of the Totatlanika Schist, not from the deposit itself. μg/L = micrograms per liter.

1

Crustal background 0.205 μg/L (Martin and Whitfield,1983).

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>1,900–3,300 (500–1,000)

>370–1,900 (100–500)

>190–370 (50–100)

91–190 (1–50)

Sulfate (mg/L) x Background1

EXPLANATION

q

Figure 26. Sulfate in water samples. High sulfate occurs in creek water flowing across the alteration zone 

(100–500× global crustal background), but sulfate in most acidic springs in lower section of deposit exceeds 

background by 500–1,000×. Sulfate is mitigated by mixing with Dry Creek. mg/L = milligrams per liter. 

1

Crustal background 3.7 μg/L (Rose and others, 1979).

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>30,000–240,000 (>1,000–10,000)

>3,000–30,000 (>100–1,000)

>300–3,000 (>10–100)

1–300 (0.03–10)

Zinc (μg/L) x Background1

EXPLANATION

q

Figure 25. Zinc in water samples. Zinc is high (>1,000× global crustal background) on all creeks except Red 

Mountain Creek where only the acidic spring east of Red Mountain has zinc higher than 100× background. 

Zinc is mitigated somewhat after Red Mountain Creek mixes with Dry Creek. μg/L = micrograms per liter. 

1

Crustal background 30 μg/L (Martin and Whitfield, 1983).

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>100–590 (>1,000–5,900)

>10–100 (>100–1,000)

>1.0–10 (>10–100)

>0.05–1.0 (>0.5–10)

<0.05 (undetect) (<0.5)

Lead (μg/L) x Background1

EXPLANATION

q

Figure 24. Lead in water samples. Lead is undetected in creek waters above the alteration zone (AZ), but 

exceeds 1,000× global crustal background on Lago Creek and Megan’s Draw after passing through the AZ. 

Mixing of Red Mountain Creek and Dry Creek mitigates most lead. μg/L = micrograms per liter.

1

Crustal background 0.1μg/L (Martin and Whitfield,1983).

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

Dry Creek

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>100–670 (>5,000–30,500)

>10–100 (>500–5,000)

>1.0–10 (>50–500)

>0.004–1.0 (>0.1–50)

0.004 (undetect) (<0.1)

Cadmium (μg/L) x Background1

EXPLANATION

q

Figure 23. Cadmium in water samples. Waters flowing across the alteration zone (AZ) immediately exceed 

global crustal background levels by 500×, increasing to >5,000× below the AZ. Most springs within the AZ 

exceed background by >5,000×. Cadmium is somewhat mitigated in waters after Red Mountain Creek joins 

Dry Creek. μg/L = micrograms per liter. 

1

Crustal background 0.02 μg/L (Martin and Whitfield,1983). 

3000

4000 3500

4500

5000

5500

6000

5000

4500

4000

3500

3000

3500

Dry Creek

Megan’s

Creek

Lago Ck.

Creek

Red Mountain

Fosters

Draw

Mountain

Red

0 0.5 KILOMETER1

0 0.5 MILE1 6,470 ft 2,750 ft

Approx. visible extent of alteration

Creek site Spring site

>1,500–14,000 (>1,000–10,000)

>150–1,500 (>100–1,000)

>15–150 (>10–100)

>0.5–15 (>0.01–10)

<0.5 (undetect) (<0.01)

Copper (μg/L) x Background1

EXPLANATION

q

Figure 22. Copper in water samples. Copper exceeds global background levels by up to 1,000× in stream 

waters, but from 100–10,000× in springs within the alteration zone. Copper is greatly mitigated in waters of 

Red Mountain Creek by mixing with Dry Creek. μg/L = micrograms per liter. 

1

Crustal background 1.5 μg/L (Martin and Whitfield,1983). 

6.5

8.5

0.3

0.05

250

10

4

250 500

Conductance,

 μS/cm

Turbidity, FTU

Dissolved O2

Alkalinity, n =15

Acidity, n =23

ClF- NO3

-

SO4

2-

Ca

Al

Fe

K

Mg

Na

Si

pH

TDS

2

3

4

5

6

7

8

9

pH

Concentration, in milligrams per liter

0.0005

0.005

0.05

0.5

5

50

500

5,000

n = 33

Figure 21. Boxplots of field measurements, anions, major cations, and pH. 

Sulfate, F–

, and NO3

–

 naturally exceed Environmental Protection Agency’s 

drinking water primary MCL. Medians of total dissolved solids (TDS), Al, Fe, and 

pH exceed the secondary MCL. FTU = formazine turbidity units. μS/cm = microSiemens per centimeter. Data from Eppinger and others (2007).

100

6

2

10

100

50

4

2,000

15

100

5

1,300

50

5,000

CuCdCo

BaBe

Cr

As

Ag

Li

MnMo

Ni

P

Sr

PbSe

Th

Sb

Y

U

Tl

V

W

∑REE

Zn

0.005

0.05

0.5

5

50

500

5,000

50,000

500,000

Concentration, in micrograms per liter

n = 33

Figure 20. Boxplots of trace cations and sum of rare earth elements (∑REE). Elements 

Cu, Cd, Ni, Pb, Be, As, and Tl naturally exceed the Environmental Protection Agency’s 

drinking water primary MCL. Median levels of zinc and manganese exceed the secondary 

MCL. See Element Maps for maps of Zn, ∑REE, Cu, Cd, and Pb. Data from Eppinger and 

others (2007).

1

Primary MCL is a maximum contaminant regulatory

 action level established by the Alaska Department of 

 Environmental Conservation.

2

Secondary MCL is a nonregulatory, recommended

 water-quality goal.

Drinking water contaminant levels from U.S. Environmental

 Protection Agency (2003) and Alaska Department of 

 Environmental Conservation (2003)

Secondary Maximum Contaminant Level2

Primary Maximum Contaminant Level (MCL)1

Minimum concentration

25th percentile

Median value

75th percentile

Maximum concentration

EXPLANATION

Figure 19. Detail of highly 

acidic spring on Megan’s 

Draw with Gymnocolea 

inflata (black and green 

liverwort on left), and a mix 

of Polytrichum commune and 

P. juniperinum (pinkish and 

light green moss on right). 

The muddy water-filled 

depression is a moose 

footprint.

Figure 18. Mixing zone 

below clear acidic spring on 

Lago Creek visible on left 

edge of photo. Green and 

black liverwort Gymnocolea 

inflata lines the left bank 

splash zone.

Figure 17. Iron-oxide-stained 

alluvium on Dry Creek, 

approximately 0.5 mile 

downstream of confluence 

with Red Mountain Creek. 

Circum-neutral pH of Dry 

Creek, combined with 

acid-consuming rock flour in 

the water, causes final iron 

load to precipitate as red 

staining on rocks.

Figure 16. Detail of acid salt 

precipitates under a 

protected ledge.

Figure 15. Aluminumoxyhydroxide-floc precipitate. 

 The floc has a gel-like

 appearance but breaks apart

 when disturbed

Figure 14. Supergene vuggy 

silica float (rock fragments) 

from a scree pile shed from 

the west side of Red Mountain. Precipitating iron-oxide 

cements the rock fragments 

together with “ferricrete.”

Figure 13. Mixing of low-pH 

water from the acidic spring 

(upper half of channel) with 

higher pH water of Red 

Mountain Creek (lower half 

of channel). Changes in pH 

trigger precipitation of iron 

oxides from the springwater 

and aluminum-oxyhydroxide 

minerals from the creekwater.

Figure 12. Iron-oxidecemented pool on Lago 

Creek. Ferricrete underlies 

and cements all alluvium. 

Note milky appearance of 

water due to actively precipitating aluminum floc.

Figure 11. Fosters Creek just above the 

confluence with Lago Creek. The 

flowing water is clear; the white color is 

caused by aluminum-oxyhydroxide 

precipitates coating the creekbed.

Figure 10. Acidic spring west of Red 

Mountain alongside Lago Creek. The bright 

salmon-colored precipitate was identified by 

x-ray-diffraction analysis as dominantly 

schwertmannite, a mineral that commonly 

forms in iron-rich, acid sulfate waters in the 

pH range of 2–4. Note black liverwort, a 

possible acidophile or metallophile (Gough 

and others, 2006), growing in the splash 

zone on the right side of the creek.

-1 0 1 2 3 4 5 6 7 8 9

pH

0.0001

0.001

0.01

0.1

1

10

100

1,000

10,000

100,000

Sum Cd + Co + Cu + Ni + Pb + Zn, in milligrams per liter

High acid,

High acid,

Acid,

high metal high metal

Ultra acid,

extreme metal

low metal

High acid,

extreme metal

Acid,

extreme metal

Near neutral,

extreme metal

Near neutral,

high metal

Acid,

low metal

Near neutral,

low metal

Ultra acid,

ultra metal

High acid,

ultra metal

Diverse mine drainage, n = 125

Upstream of alteration zone, n = 8

Downstream of alteration zone, n = 6

Within alteration zone, n = 19

EXPLANATION

Figure 9. Ficklin diagram of pH versus the dissolved metals Cd + Co + Cu + Ni + Pb + Zn from 

filtered and acidified water samples. Mine drainage waters are from diverse mineral deposit types 

worldwide, for purposes of comparison. Diagram from Eppinger and others (2007).

Figure 8. Acidic spring east 

of Red Mountain alongside 

Red Mountain Creek. This 

spring has one of the lowest 

pH values (3.0) and highest 

specific conductance values 

(3,400 microSiemens/ 

centimeter) found at the 

deposit. The sum of rare 

earth elements dissolved in 

the spring water is 583,000 

parts per billion, more than 

100,000 times crustal 

background levels (fig 27).

Figure 7. Quartz stockwork 

observed in colluvium. The 

surrounding rock has been 

eroded away leaving raised 

quartz veinlets behind.

Figure 6. Dissolution vugs 

(cavities) in sulfide-rich 

mottled metarhyolite found 

on the west end of the 

deposit between Fosters and 

Lago Creeks (see geologic 

map). 

Figure 5. View of Red 

Mountain from Red Mountain 

Creek above the deposit. 

Note the natural transition 

from vegetation-covered 

Totatlanika Schist (left) to the 

completely vegetation-free 

volcanogenic massive sulfide 

deposit (right). 

Figure 4. Volcanic heat at spreading center drives hydrothermal circulation and chemical exchange 

between the ocean crust (brown) and seawater (dark blue). Metal-laden plume drifts on sea current 

and minerals precipitate into seafloor deposits. HT = high temperature. cm/s = centimeters per 

second. Image from National Oceanic and Atmospheric Administration (2002).

Figure 3. Possible settings of volcanic-hosted massive sulfide (VHMS) deposits in convergent 

margins. High-T = high temperature. Adapted from Huston and others (2010).

Figure 2. View of Red 

Mountain from the air, 

looking south. Note the 

extraordinary orange and red 

staining and lack of vegetation over the deposit.

Element Maps

Element Maps

Element Concentration Boxplots Element Concentration Boxplots

 The Red Mountain deposit is a spectacular example of acid generation, metal 

leaching, metal precipitation, and self-mitigation processes occurring in a completely 

natural, undisturbed setting. Red Mountain Creek and its tributaries within the alteration 

zone do not and probably never have supported significant aquatic life, except perhaps 

those organisms that have adapted to the extreme environment of low pH and very metalliferous conditions. Any future mining attempts will need to thoroughly account for the 

deposit’s acid-generating and metal-liberating potential as part of mine feasability.

Conclusion Conclusion

 Almost no vegetation covers the AZ, nor grows within or adjacent to creeks 

crossing the Red Mountain VMS deposit (figs. 2 and 5) due to the acid generation and 

mobility of metals into the surface environment. However, creeks, springs, and seeps 

within the AZ or in areas affected by acidic groundwaters are inhabited by an unusual 

community of bryophytes (liverworts and mosses). Gymnocolea inflata, a black and 

green bryophyte, grows in areas of standing or flowing water, and the mosses Polytrichum commune and P. juniperinum grow above the water or in the splash zone (figs. 8, 

10, 18, and 19). Analyzed brypohyte vegetation from areas that receive metal-laden spray 

indicates high levels of metals such as As, Cd, Cu, Fe, Hg, Pb, and Zn. It is unknown 

whether the Red Mountain bryophyte assemblage is acidophilic or requires high concentrations of dissolved metals, and there are no reports in current literature of similar observations (Gough and others, 2006).

 Downstream of the AZ, diamondleaf willow (Salix pulchra and S. glauca) dominates creekside vegetation and is known to be an important food source for moose, hare, 

and ptarmigan. Where the tree-root mass is located in creek sediment instead of soil, the 

willows have much higher levels of major and trace elements (Al, As, Cd, Cr, Fe, Al, and 

Pb), and levels of cadmium are orders of magnitude above levels found to be toxic to 

ptarmigan (Gough and others, 2006). It is unknown what toxicity this represents to local 

fauna.

Biology Biology

 The waters of Red Mountain Creek remain acidic (pH ≈4.2) and metalliferous 

from the alteration zone (AZ) to the confluence with Dry Creek 1.5 miles (2.5 km) 

downstream. By contrast, the waters of Dry Creek are near-neutral pH, alkaline, and 

relatively nonmetalliferous due to it being a relatively large, turbid, glacial-flour-rich 

creek that drains rocks with acid-consuming capability (Martin and Whitfield, 1983).

 Red to orange staining is evident on alluvium from the AZ down Red Mountain 

Creek and for about 1 mile (1.5 km) down Dry Creek, but beyond this only weaker hues 

exist for about another 0.5 mile (0.8 km) (fig. 17). The only geochemical signature of Red 

Mountain that persists beyond the confluence is slightly anomalous zinc in sediments, 

and cerium and lanthanum in waters. Thus, the hydrogeochemical and visual indicators 

are that the Red Mountain VMS deposit appears to be largely self-mitigating within a few 

miles downstream of the deposit, due largely to dilution by the much larger Dry Creek. 

Self-Mitigation

Self-Mitigation

 In protected areas, secondary dissolved minerals precipitate as acidic salts (fig. 

16). These highly soluble efflorescent sulfate salts temporarily sequester iron, other 

metals, and acidity. Dissolution of these salts during precipitation events, or by snowmelt, 

can cause a pulse of acidity and dissolved metals into the surface-water environment. 

Soluble accessory metals include Fe, Al, Mg, Mn, Cd, Co, Cu, Ni, Mo, Pb, Zn, and the 

rare earth elements. A variety of accessory mineral salts have been identified at Red 

Mountain, all of which are products of pyrite dissolution and coincident acid rock drainage.

Acid Salts Acid Salts 

 When a pH change occurs in acidic runoff, the dissolved metals can start to 

precipitate. Figure 13 shows a vivid example of this process. Here, water from the same 

acidic spring shown in figure 8 (top half of channel in figure 13) mixes with water from 

Red Mountain Creek (bottom half of channel in figure 13). The spring water, at a pH of 

3.0, has a load of dissolved iron and is actively precipitating iron (orange colors), while 

the creek water, at a pH of roughly 5, has previously lost all iron and is precipitating only 

aluminum (white colors). As the two waters mix, the pH rises in the spring water and 

drops in the creek water, causing a reaction front.

 Iron precipitates throughout the deposit and down all creeks draining the deposit 

in the form of “ferricrete” and underlies and cements all alluvium to a depth of several 

meters (figs. 8, 12, and 14). Aluminum-oxyhydroxide-floc precipitates cause a milky 

appearance in flowing water and collect in calm water and pools in a white, gel-like 

coating that breaks apart when disturbed (figs. 11, 12, 13, and 15).

Metal Oxide Precipitation

Metal Oxide Precipitation

 The destrucion of the original rock-forming minerals through QSP alteration has 

released many of their elemental constituents into the subsurficial and surficial aquatic 

environments. Figure 9 illustrates how neutral-pH waters from upstream of the deposit 

are low in metals, whereas acidic waters within and below the deposit approach extreme 

levels. The primary metal is iron, indicated by the extreme amount of red oxide staining 

throughout the deposit, but other metals include Al, Cd, Co, Cu, Ni, Mn, Mo, Pb, Zn, and 

various rare earth elements (figs. 20 and 21). The metals remain dissolved until a change 

in Eh (oxidation potential) or pH causes them to precipitate. Hence, some metals can 

remain dissolved in waters flowing beyond the boundary of a VMS deposit (see Element 

Maps).

Metal Dissolution and Transport

Metal Dissolution and Transport

 Red Mountain is divided by a dense network of faults and fracture zones 

(unpublished data), and the deposit is tilted to the north (see geologic map) exposing 

underlying quartz stockwork veins in the lower (southern) section of the deposit and 

massive sulfide horizons in the upper (northern) section. A zone of altered rock has 

formed around and within the deposit, marked by intense red, maroon, orange, and 

yellow colors and a near-total lack of vegetation (fig. 5). A series of acidic springs, 

sampled during the study (figs. 8, 10, 18, and 19), were found to be associated with the 

fault and fracture network suggesting that groundwater flow along fractures is important, 

if not prevalent. As Red Mountain Creek, Fosters Creek, and Lago Creek bisect and cross 

the deposit, the waters become acidic and metalliferous, with corresponding increases in 

conductivity (see geologic map).

Acidic Springs and Runoff Acidic Springs and Runoff

 The massive to semimassive zinc-, lead-, and silver-rich sulfide horizons at Red 

Mountain occur within and at the base of an aphanitic (microcrystalline) metarhyolite that 

has undergone intense primary quartz-sericite-pyrite (QSP) alteration and secondary 

oxidation of pyrite.

Common sulfides found at the Red Mountain VMS deposit:

 Pyrite (FeS2

) Chalcopyrite (CuFeS2) 

 Sphalerite (ZnS) Galena (PbS)

 As the deposit became exposed to air and water, supergene processes involving 

the chemical destruction of pyrite and coincident production of sulfuric acid and various 

secondary acidic minerals produced strongly acidic groundwater. The acidic groundwater 

further altered the bedrock creating local clay-rich zones and vuggy (cavitied) silica-rich 

rocks, and completely destroyed the original rock-forming minerals (figs. 6 and 7).

Examples of pyrite oxidation (from Plumlee, 1999):

 FeS2

 + 3.75O2 + 0.5H2O = Fe3+ + H+ + 2SO4

2– 1 mole acid

 FeS2

 + 3.5O2 + H2O = Fe2+ + 2SO4

2– + 2H+

 2 moles acid

 FeS2

 + 3.75O2 + 3.5H2O = 2SO4

2– + 4H+

 + Fe(OH)3(5) 4 moles acid

 FeS2

 + 14Fe3+ + 8H2O = 15Fe2+ + 2SO4

2– + 16H+

 16 moles acid

Sulfide Geochemistry Sulfide Geochemistry

 At Red Mountain, several massive sulfide horizons have been identified within 

the Totatlanika Schist, near the contact between the felsic metavolcanic and carbonaceous 

rocks of the Mystic Creek Member and the overlying metasedimentary rocks of the 

Sheep Creek Member (see geologic map). Sulfide minerals such as pyrite, sphalerite, 

galena, and chalcopyrite were deposited throughout a brown pyritic mudstone or in 

massive horizons at the base of and within a mottled metarhyolite. Figure 4 shows a 

mechanism for sulfide deposition by typical “black smoker” plumes in a spreading center. 

 The Bonnifield mining district includes 26 known volcanogenic massive sulfide 

(VMS) prospects. These occur in a greenschist-facies assemblage of metavolcanic and 

metasedimentary rocks in the Yukon-Tanana terrane. Protoliths consist of felsic and mafic 

volcanic and subvolcanic rocks interfingered with carbonaceous and siliciclastic sediments, indicative of a submarine extensional back-arc-basin setting near the continental 

margin of the North American craton that was subsequently uplifted and exposed 

(Dusel-Bacon and others, 2007). See figure 3. 

Geology Geology

|k

Tcu

MDtmc

MDtsh

MDtsh

Qa

Qa

MDtsh

MDtch

Df

Qa

MDtm

MDtch

MDtmc

MDtc

Df

MDtsh

Qa

Df

MDtmc

Df

MDtsh

MDtch

Qa

Qa

MDtmc

MDtsh

MDtc

Df

MDtc

Qa

Tcu

Df Df

MDtmc

Df

Df

Qa

Qa

Qa

MDtmc

Qa

MDtmc

MDtmc

Qa

MDtsh MDtsh

MDtch

Df

Tcc

Tcc

Tcc

Tb

Df

Qa

MDtch

Tb

Df

MDtch

Df

MDtch

Df

Tcu

|k

|k

Dry Creek

Fosters Creek

Lago

Creek

Red Mountain Creek

Megan’s

Draw

Red Mountain Creek

3500

4000

4500

4500

5000

5500

5500

6000

4000

4000

3500

3000

3000

3000

3000

4000

3500

4000

4000

5500

5500

5000

4500

5000

4500

4000

4000

3500

4000

4500

5000

5000

5500

5000

4000

3500

4500

Red

Mountain

147°28'W 147°27'W 147°26'W 147°25'W 147°24'W 147°23'W 147°22'W 147°21'W 147°20'W 147°19'W 147°18'W 147°17'W

63°57'N 63°56'30"N 63°56'N 63°55'30"N 63°55'N 63°54'30"N 63°54'N

q

Geology and structure from W.G. Gilbert (1977).

All other data from the U.S. Geological Survey.

Projection: NAD83, UTM Zone 6N.

Central Meridian: 147°W.

0 0.5 1MILE

0 0.5 1 KILOMETER

SCALE 1:24,000

>7.0

6.1–7.0

5.1–6.0

4.1–5.0

3.1–4.0

<3.0

pH

<800 801–1,200 1,201–2,000 >2,000

Conductivity (microSiemens/centimeter)

Conductivity versus pH in waters

Creek site Spring site

Approximate visible extent of alteration

Fault (Dashed where approximate,

 dotted where inferred)

Contact

Structure

|k Keevy Peak Formation (lower Paleozoic)

Df Devonian felsic intrusives

MDtm Moose Creek Member

MDtc California Creek Member

MDtch Chute Creek Member

MDtmc Mystic Creek Member

MDtsh Sheep Creek Member

Totatlanika Schist (Mississippian–Devonian)

Tcc Tertiary coal outcrop

Tcu Tertiary coal-bearing rocks, undivided

Tb Tertiary(?) basaltic intrusion

Qa Quaternary alluvium, colluvium, talus, or fan

Map units

EXPLANATION

Geologic map of the Red Mountain

VMS deposit area, Alaska Range

West Fork

Delta River

Mystic Ck.

California Ck.

Wood River

Nenana River

Moose Creek

Little

Totatlanika River

Tatlanika Ck.

Dry Creek

Sheep Ck.

Healy River

Moody Creek

3

HEALY D-3

HEALY D-4

HEALY D-2

HEALY D-1

FAIRBANKS A-2

FAIRBANKS A-4 FAIRBANKS A-3

FAIRBANKS A-1

RED MOUNTAIN

STUDY AREA

Healy

149°0'W 148°50'W 148°40'W 148°30'W 148°20'W 148°10'W 148°0'W 147°50'W 147°40'W 147°30'W 147°20'W 147°10'W 64°0'N 63°55'N 63°50'N 63°45'N

Digital elevation, shaded relief, town and 

quadrangle data from USGS; hydrological 

data from National Hydrological Dataset.

Highway data from Alaska Department of 

Transportation.

Projection: NAD83, UTM zone 6N

USGS 1:63,360 quadrangle Central meridian: 147°W.

Major creek or river

Alaska State highway

Town

0 8642 10 KILOMETERS

0 8642 10MILES

SCALE 1:300,000

8,425 1,200

Elevation (feet) BONNIFIELD

STUDY

AREA

ALASKA

Figure 1. Map of the central part of the Bonnifield mining district and study area, with the Red Mountain deposit study area identified.

he U.S. Geological Survey (USGS) has investigated the environmental 

geochemistry of a group of unmined volcanogenic massive sulfide (VMS)

deposits in the Bonnifield mining district, Alaska Range, east-central Alaska. 

The spectacularly colored Red Mountain deposit is the best exposed of these 

and provides excellent baseline geochemical data for natural environmental 

impacts of acidic rock drainage, metal dissolution and transport, and acidic 

salt and metal precipitation from an exposed and undisturbed VMS deposit. 

T

By Stuart A. Giles and Robert G. Eppinger

By Stuart A. Giles and Robert G. Eppinger

A Geochemical A Geochemical Perspective of Red Mountain—An Unmined Volcanogenic Massive Sulfide Deposit in the Alaska Range erspective of Red Mountain—An Unmined Volcanogenic Massive Sulfide Deposit in the Alaska Range

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY Open-File Report 2014–1037

Any use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government

Publishing support provided by:

Denver Publishing Service Center

To learn about the USGS and its information products visit 

http://www.usgs.gov/

1-888-ASK-USGS

For more information concerning this publication, contact:

Center Director

USGS Central Minerals and Environmental Resources Science Center

Box 25046, Mail Stop 973

Denver, CO 80225

(303) 236–1800

Or visit the Central Minerals and Environmental Resources Science Center Web site at:

http://minerals.cr.usgs.gov/

Suggested Citation:

Giles, S.A., and Eppinger, R.G., 2014, A geochemical perspective of Red Mountain—An unmined volcanogenic massive

sulfide deposit in the Alaska Range: U.S. Geological Survey Open-File Report 2014–1037, 1 plate 

http://dx.doi.org/10.3133/ofr20141037. .

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141037