Sischu Mountain

Prospect in Alaska, United States with commodities Tin, Arsenic, Gold, Bismuth, Copper, Manganese, Molybdenum, Nickel, Antimony, Zinc, Zirconium

Geologic information

Identification information

Deposit ID 10307708
Record type Site
Current site name Sischu Mountain

Geographic coordinates

Geographic coordinates: -152.926, 64.10354 (WGS84)
Relative position The Sischu Mountain prospects cover about 20 square miles, including Sischu Mountain and several surrounding peaks. The approximate center of the prospect area is in NE1/4SW1/4 section 30, T. 9 S., R. 27 W., of the Fairbanks Meridian. There is an airstrip at Lake Minchumina approximately 30 miles southeast of the prospects. The Sischu Mountain prospects are located on land selected by or conveyed to Doyon, Limited.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Tin Primary
Arsenic Secondary
Gold Secondary
Bismuth Secondary
Copper Secondary
Manganese Secondary
Molybdenum Secondary
Nickel Secondary
Antimony Secondary
Zinc Secondary
Zirconium Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Magnetite Ore
Pyrite Ore
Chlorite Gangue
Goethite Gangue
Kaolinite Gangue
Quartz Gangue
Tourmaline Gangue

Alteration

  • (Local) On Sischu Mountain, float samples exhibit silicification and chlorite-kaolinite alteration and vein brecciation with tourmaline. An area identified by a color anomaly consists of hydrothermally brecciated sandstone fragments in a goethite matrix.

Nearby scientific data

(1) -152.926, 64.10354

Comments on the geologic information

  • Geologic Description = Sischu Mountain is composed of multiple igneous phases intruding phyllite, limestone, and siltstone to the north and various volcanic rocks, including rhyolite, dacite, andesite, and basalt, to the south and east (Chapman and Yeend, 1981). The phyllite, limestone, and siltstone are of Devonian age, and the intrusive rocks are Cretaceous to Tertiary (Chapman and Yeend, 1981). Float mapping has found aplite, coarse biotite granite, porphyry granite, hornblende-biotite monzodiorite, and porphyry dikes (Bond, 1985). Regionally, the area contains a system of northeast-trending strike-slip and related conjugate faults associated with Cretaceous to Tertiary plutonic rocks and coeval or younger volcanic rocks (Clautice and others, 1993). On Sischu Mountain, float samples exhibit silicification and chlorite-kaolinite alteration and vein brecciation with tourmaline. Disseminated pyrite and chalcopyrite occur in altered intrusive rock. Some aplite dikes contain as much as 1 percent magnetite. An area identified by a color anomaly consists of hydrothermally brecciated sandstone fragments in a goethite matrix. A rock chip of altered granite contained as much as 1,450 ppm As, 25 ppm Bi, 100 ppm Sn, and 15 ppm Mo (Bond, 1985). Clautice and others (1993) reported analyses of several samples: (1) a rhyolite dike cutting limestone contained as much as 1,200 ppm Zr, 86 ppm Cu, 542 ppm Zn, 265 ppm Ni, 136 ppm As, 35 ppm Sb, 799 ppm Mn, and 10 ppm Sn; (2) limestone near a granitic contact contained as much as 114 ppm As; (3) equigranular, biotite monzonite contained 767 ppm Zn, 47 ppm As, 23 ppm Pb, and 6 ppm Sn; (4) a rhyolite dike in limestone contained 132 ppm As, 590 ppm Mn, and 38 ppm Pb; and (5) limonitic rhyolite contained 105 ppm As and 463 ppm Mn. A regional stream sediment sampling, airborne radiometrics, and mapping program in 1975-76 and 1980 identified several anomalies. In 1984, one sample was collected. In 1985, exploration efforts consisted of mapping and collecting 12 rock chip, 7 stream sediments, and 8 pan concentrate samples (Bond, 1985). There are no indications of production.
  • Age = Probably related to Cretaceous to Tertiary plutonism.

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name Ruby

Comments on the production information

  • Production Notes = There are no indications of production.

Comments on the workings information

  • Workings / Exploration = A regional stream sediment sampling, airborne radiometrics, and mapping program in 1975-76 and 1980 identified several anomalies. In 1984, one sample was collected. In 1985, exploration efforts consisted of mapping and collecting 12 rock chip, 7 stream sediments, and 8 pan concentrate samples (Bond, 1985). There are no indications of production.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF KH006

Bibliographic references

  • Deposit

    Cobb, E.H., 1977, Placer deposit map of central Alaska: U.S. Geological Survey Open-File Report 77-168B, 64 p., 1 map, scale 1:1,000,000.

  • Deposit

    Chapman, R.M., and Yeend, W., 1981, Geologic reconnaissance of the east half of the Kantishna River quadrangle and adjacent areas, in Albert, N.R.D., and Hudson, T., eds, The United States Geological Survey in Alaska, Accomplishments during 1979: U.S. Geological Survey Circular 823-B, 149 p.

  • Deposit

    Cobb, E.H., and Chapman, R.M., 1981, Mineral occurrences (other than mineral fuels and construction materials) in the Kantishna River and Ruby quadrangles, Alaska: U.S. Geological Survey Open-File Report 81-170, 94 p.

  • Deposit

    Bond, James, 1985, Geologic field examinations in Doyon Limited, regional selection block 9: Doyon Limited Report 85-19, 179 p. (Report held by Doyon, Ltd., Fairbanks, Alaska).

  • Deposit

    Clautice, K.H., Bowman, N.D., Clough, J.G., Gilbert, W.G., Kline, J.T., Smith, T.E., and Blodgett, R.B., 1993, Land selection Unit 8 (Kantishna River, Ruby, and Medfra quadrangles): References, lead isotope, geochemical and major oxide data: Alaska Division of Geological and Geophysical Surveys, 42 p., 1 sheet, scale 1:250,000.

  • Deposit

    Eakin, H.M., 1918, The Cosna-Nowitna region, Alaska: U.S. Geological Survey Bulletin 667, 54 p.

Comments on the references

  • Primary Reference = Bond, 1985

General comments

Subject category Comment text
Deposit Model Name = Plutonic-related mesothermal veining.
Deposit Other Comments = the Sischu Mountain prospects are located on land selected by or conveyed to Doyon, Limited. For more information, contact Doyon, Limited.

Reporter information

Type Date Name Affiliation Comment
Reporter 08-NOV-99 Cameron S. Rombach Alaska Division of Geological and Geophysical Surveys