Homestake Mine, Hyder District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
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Location: The Homestake mine is in Section 7 at about 3500 feet elevation on a south-facing mountainside approximately 0.3 mile east of upper Ibex Creek (Elliott and Koch, 1981, p. 14, loc. 51). The location is probably accurate within a quarter of a mile.
Geology: The country rock in the area of the Homestake mine is Triassic Texas Creek Granodiorite, which regionally underlies and locally intrudes pelitic metasedimentary and subordinate andesitic metavolcanic strata of the Jurassic or older Mesozoic Hazelton Group; and the Eocene Hyder Quartz Monzonite, which intrudes the Hazelton and Texas Creek rocks (Smith, 1977, Koch, 1996). The deposit consists of a quartz fissure vein 4-5.5 feet thick in Texas Creek Granodiorite (Buddington, 1925, p. 88-89). The vein was traced in outcrop for about 250 feet. The mineralized parts of the vein contain bands of solid sulfide up to 4 feet thick consisting mainly of argentiferous 'steel' galena, accompanied by pyrite, chalcopyrite, and a little sphalerite. The granodiorite hanging wall of the vein contains stringers of tetrahedrite. So-called 'steel' galena resembles augen gneiss with eyes of granulated pyrite in flow-banded galena; this texture indicates that the mineral deposit was subjected to intense stress since its formation (Buddington and Chapin, 1929, p. 320). A 9.5-ton test shipment of sorted ore sent to a smelter in 1925 contained 50% Pb, 0.7% Zn, 22.87 oz Ag per ton, and 0.29 oz Au per ton (Buddington, 1929, p. 95; Cobb, 1978, p. 39). Lead-isotope studies of galena from the Homestake mine (Maas and others, 1929, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Workings: A 25-foot crosscut adit is reported to have cut the vein 35 feet below its outcrop (Buddington, 1926, p. 53).
Age: Lead-isotope studies of galena from the Homestake mine (Maas and others, 1929, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Commodities (Major) - Ag, Au, Cu, Pb, Zn
Development Status: Yes; small
Deposit Model: Polymetallic veins
6 entries listed. 6 valid minerals.
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Buddington, A.F., 1925, Mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 773-B, p. 71-139. Buddington, A.F., 1926, Mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 783, p. 41-62. Buddington, A.F., 1929, Geology of Hyder and vicinity, southeastern Alaska, with a reconnaissance of Chickamin River: U.S. Geological Survey Bulletin 807, 124 p. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Bradfield Canal quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-922, 98 p. Elliott, R.L., and Koch, R.D., 1981, Mines, prospects, and selected metalliferous mineral occurrences in the Bradfield Canal quadrangle, Alaska: U.S. Geological Survey Open-File Report 81-728-B, 23 p., 1 sheet, scales 1:250,000 and 1:63,360. Koch, R.D., 1996 [In press), Reconnaissance geologic map of the Bradfield Canal quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report, 1 sheet, scale 1:250,000. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p. Smith, J.G., 1977, Geology of the Ketchikan D-1 and Bradfield Canal A-1 quadrangles, Alaska: U.S. Geological Survey Bulletin 1425, 49 p., 1 plate.