Unnamed Occurrence (ARDF - BC093; east of Upper Marten Lake), Petersburg District, Wrangell-Petersburg Borough, Alaska, USA
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Geology: This occurrence was first described by Still and others (2002) in an area with little previous indication of mineralization. It is along a fault zone that strikes 330 degrees and dips 75 degrees to the northeast. The fault cuts Mesozoic and/or Paleozoic schist and paragneiss near the contact with Cretaceous diorite (Elliot and Koch, 1981). The occurrence is about 2 miles west of the Coast Range megalineament (Brew and Ford, 1978), and the 'Great Tonalite Sill' (Brew and Morrell, 1983). Quartz stringers and clay gouge are common in the fault zone. Some of the quartz stringers contain pyrite, pyrrhotite, and other sulfides. Four samples of iron-stained quartz were collected along the fault; one contained 475 parts per billion gold, 86.9 part per million (ppm) silver, and 1,218 ppm lead. Another quartz vein about 0.2 to 1 foot thick about 2 miles north of the main occurrence contains only minor pyrite and assayed 517 ppb gold.
Workings: Only a few samples collected by Still and others (2002) during a regional mineral assessment by the Bureau of Land Management.
Alteration: No information other than along a fault zone with clay gouge.
Commodities (Major) - Ag, Au, Pb
Development Status: None
Deposit Model: Gold-quartz veinlets along a regional fault.
3 entries listed. 3 valid minerals.
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Brew, D.A., and Ford, A.B., 1978, Megalineament in southeastern Alaska marks southwest edge of Coast Range batholithic complex: Canadian Journal of Earth Sciences, v. 15, p. 1763-1772. Brew, D.A., and Morrell, R.P., 1983, Intrusive rocks and pluton belts of southeastern Alaska, Geologic Society of America Memoir, 159, p. 171-193. 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 81-728B, 23 p., 1 sheet. Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central southeast Alaska: Bureau of Land Management Technical Report 51, 560 p.