Unnamed Prospect (ARDF - TL064; near Round Mtn), Yentna District, Matanuska-Susitna Borough, Alaska, USA
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Location: Alaska Department of Natural Resources unpublished claim records show this locality, about one mile south of Round Mountain, to cover an approximately one square mile area in Section 25, T. 23 N., R. 19 W., of the Seward Meridian and adjacent Sections 35 and 36, in T. 22 N., R. 19 W., of the Seward Meridian. Coordinates are given for poorly exposed part of the prospect in Section 35. Exposures in Section 25 are in a canyon, easily seen from the air.
Geology: Mesozoic marine sedimentary rocks (KJs) and (or) undivided Tertiary tuff and tuffaceous sedimentary rocks (Tvs) mapped by (Reed and Nelson, 1980) are intruded by intermediate to mafic sills, dikes and small plugs (Cominco American Incorporated, unpublished report). The intrusive rocks are overprinted by quartz-sericite-pyrite and magnetite-carbonate alteration. Auriferous veins, pods and stockwork which contain variable amounts of pyrite, pyrrhotite, sphalerite, galena and quartz,+/-chalcopyrite, stibnite and arsenopyrite are concentrated along intrusive contacts and structures. Geochemical values in rock chip samples range from several hundred ppb gold to just under an ounce per ton gold in select high grade samples. Silver values up to about an ounce per ton is recorded select samples (Cominco American Incorporated, unpublished report).
Workings: Prospecting, silt, soil and rock chip geochemistry, magnetic and VLF geophysical survey, and mapping at 1:12,000 scale by Cominco American Incorporated in the late 1980s. Geochemical values in rock chip samples range from several hundred ppb gold to just under an ounce per ton gold in select high grade samples. Silver values up to about an ounce per ton is recorded select samples (Cominco American Incorporated, unpublished report).
Age: Early or middle Tertiary; mineralization is interpreted to be linked to the Tvs, which Reed and Nelson (1980) relate to plutonism of the same age in this part of the Alaska Range.
Alteration: Quartz-sericite-pyrite, quartz-pyrite, carbonate, and magnetite alteration.
Commodities (Major) - Ag, Au, Pb, Zn; (Minor) - As, Sb
Development Status: None
Deposit Model: Polymetallic veins (Cox and Singer, 1986; model 22c).
9 entries listed. 8 valid minerals.
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Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, 1 sheet, scale 1:250,000.