Sophie Gulch (Rock Creek)

The Sophie Gulch (Rock Creek) is a tungsten and gold mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Sophie Gulch (Rock Creek)

Commodity

Primary: Tungsten
Primary: Gold
Secondary: Lead

Location

State: Alaska
District: Nome

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

Orebody

Not available

Structure

Not available

Alterations

Alteration Text: Silicification, albitization, sulfidization, and oxidation of arsenopyrite to hematite.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Arsenopyrite
Ore: Galena
Ore: Gold
Ore: Hematite
Ore: Pyrite
Ore: Scheelite
Gangue: Albite
Gangue: Calcite
Gangue: Quartz

Comments

Comment (Exploration): Status = Active

Comment (Workings): Workings / Exploration = A placer deposit on Sophie Gulch was discovered early in the history of the Nome district. The patent plat issued for No. 1 Sophie Gulch Placer (U.S. Mineral Survey No. 721) shows three cuts in Sophie Gulch itself and a shaft on bedrock north of the gulch. The prospect was developed by shallow underground workings prior to 1916 when it was exploited for tungsten in a hydraulic open cut. Most of the tungsten-rich residual placer was mined then. During World War II, three bulldozer cuts showed very little remaining residual material (Coats, 1944) The area was prospected by R.V. Bailey in the 1980s and was extensively trenched and drilled in 1987 and 1988 by Placer Dome. It was further explored by Newmont in 1992 and by Kennecott Exploration Company in 1994 and 1995. An area that includes Sophie Gulch is being actively explored by Novagold Resources (May, 2000).

Comment (Reference): Primary Reference = This report

Comment (Production): Production Notes = Small production at Sophie Gulch began prior to 1916; it was mined extensively in 1916, mainly for tungsten. About 4,000 to 5,000 cubic yards of scheelite-bearing material were processed in 1916 (Mertie, 1918 [B 662-I, p. 425-449]; Coats, 1944; Thorne and others, 1948; Cobb, 1975).

Comment (Deposit): Other Comments = In 1944, the unweathered material was too low grade to mine for tungsten (Coats, 1944, p. 3).

Comment (Geology): Age = Mid-Cretaceous; veins cut regionally metamorphosed schist; see NM207.

Comment (Geology): Geologic Description = Sophie Gulch was placer mined for tungsten (scheelite) in 1916 (Mertie, 1918 [B 662-I, p. 457]); presumably some gold was also recovered. The mine location was about 300 feet above the point where Sophie Gulch enters the flood plain of Rock Creek. The tungsten deposit was a residual placer on mineralized bedrock; the bedrock itself was described as too low grade to be mined. About 4,000 to 5,000 cubic yards of residual placer material were mined and sluiced here that year. Mertie (1918) believed that the Sophie Gulch deposit produced a large percentage of all the scheelite mined in Alaska during 1916, when scheelite was actively sought because of high World War I prices. Scheelite was also reported on the selvages of the northeast-striking sheeted veins. Cathcart (1922, p. 246) visited Sophie Gulch a few years after Mertie. He reported quartz-feldspar and quartz-calcite veins of 'all directions', arsenopyrite, galena, and pyrite in the veins, and abundant arsenopyrite in the schist walls of the veins. Cathcart described the scheelite as yellow-brown and believed that the reddish hematitic alteration of the schist resulted from oxidation of arsenopyrite. Sophie Gulch closely follows a post-mineral(?), high-angle fault that strikes N 80 W. The fault is generally on the south side of Sophie Gulch; it was exposed and mapped in a trench by Kennecott Exploration Company in 1994. At the mouth of Sophie Gulch, the rocks south of the fault are graphitic quartz schist; the rocks north of the fault are mostly calcareous quartz-mica schist. The schist is cut by northeast-striking sheeted quartz veins. The schist's compositional layering and foliation strike northeast and dip southeast at low to moderate angles. Locally, the calcareous quartz-mica schist contains albitized zones concordant to the schistosity. The schist unit is succeeded upstream by graphitic mica schist. About 200 feet upstream on the north side, a concordant mineralized zone, locally at least 5 feet thick, was also found in Placer Dome's 1987 trench RT-7-7 (Placer Dome, written communication, 1987). Rocks in this zone contain arsenopyrite, subordinate pyrite, albite, and quartz. This zone dips gently to the southeast and appears to be the tungsten mining location described by Mertie when he visited the prospect in 1916 (Mertie, 1918).

Comment (Deposit): Model Name = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a); residual scheelite placer.

References

Reference (Deposit): Coats, R.R., 1944, Lode scheelite occurrences of the Nome area: U.S. Geological Survey Open-File Report 17, 6 p.

Reference (Deposit): Thorne, R.L., Muir, N.M., Erickson, A.W., Thomas, B. I., Hedie, H. E., and Wright, W. S., 1948, Tungsten deposits of Alaska: U.S. Bureau of Mines Report of Investigation 4174, 51 p.

Reference (Deposit): Hummel, C.L., 1962, Preliminary geologic map of the Nome C-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-247, 1 sheet, scale 1:63,360.

Reference (Deposit): Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Nome quadrangle, Alaska: U.S. Geological Survey Open-File report 78-93, 213 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Nome quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-463, 2 sheets, scale 1:250,000.

Reference (Deposit): Thorne, R.L., Muir, N.M., Erickson, A.W., Thomas, B. I., Hedie, H. E., and Wright, W. S., 1948, Tungsten deposits of Alaska: U.S. Bureau of Mines Report of Investigation 4174, 22 p.

Reference (Deposit): Cathcart, S.H., 1922, Metalliferous lodes in southern Seward Peninsula: U.S. Geological Survey Bulletin 722, p. 163-261.

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