Unnamed Prospect (ARDF - DE051), Nichols Bay, Prince of Wales Island, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
Location: This prospect is near the shoreline on the east side of upper Nichols Bay in the NE1/4 NE1/4 section 29, T. 82 S., R. 88 E. There is an old shaft, which may be one of the prospects described by Chapin (1918) on the east side of Nichols Bay. Maas and others (1991) called it the Nichols Bay shaft. The coordinates are at the old shaft, but Gehrels (1992) identified several massive sulfide layers along about a mile of shoreline near the shaft.
Geology: Gehrels and others (1983) and Maas and others (1991) report an old shaft at this location. Gehrels and others describe several massive-sulfide layers in silicic volcanic rocks that are part of a sequence of interbedded graywacke, slate, and silicic volcanic rocks of the Silurian or Ordovician Descon Formation (Gehrels, 1992). The massive sulfide layers are generally parallel to the bedding. The most prominent massive sulfide layer is 3 meters thick and contains pyrite and sphalerite; it is exposed near the old shaft. Samples contained up to 30 parts per million (ppm) silver, 3,000 ppm arsenic, 1,500 ppm barium, 500 ppm copper, 1,000 ppm lead, and 2.3 percent zinc. Maas and others (1991) also sampled the massive-sulfide layers near the old shaft. Their samples across a 60-foot-wide band of silicified volcanic rocks with disseminated sulfides contained up to 66 parts per billion gold, 491 ppm lead, and 4,907 ppm zinc. Samples from pyrite-rich massive-sulfide layers contained up to 513 ppm lead and 1.8 percent zinc. They also collected seven samples along the east shore of Nichols Bay between this site and the head of the bay. Their best values were 42 parts per billion gold, 0.9 ppm silver, 82 ppm copper, 43 ppm lead, and 154 ppm zinc.
Workings: There is an old shaft on the property and this probably was one of the prospects Chapin (1918) described on the east side of Nichols Bay. Gehrels and others (1983) indicated that claims had recently been staked in the area.
Age: The massive-sulfide layers are contemporaneous with the deposition of the Silurian or Ordovician Descon Formation.
Commodities (Major) - Cu, Zn; (Minor) - Ag, As, Ba, Pb
Development Status: None
Deposit Model: Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
| Arsenopyrite|| Chalcopyrite|| Pyrite|| Sphalerite|
4 entries listed. 4 valid minerals.
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Gehrels, G. E., 1992, Geologic map of southern Prince of Wales Island, southeastern Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-2169, 23 p., 1 sheet, scale 1:63,360. Gehrels, G. E., Berg, H. C., and Saleeby, J. B., 1983, Ordovician-Silurian volcanogenic marine sulfide deposits on southern Prince of Wales Island and the Barrier Islands, southeastern Alaska: U.S. Geological Survey Open-File Report 83-318, 10 p., 1 sheet. 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. Maas, K. M., Still, J. C., Clough, A. H., and Oliver, L. K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: Southern Prince of Wales Island and vicinity--Preliminary sample location maps and descriptions: U.S. Bureau of Mines Open-File Report 33-91, 139 p.
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Locality Updated: Challenge deposit, Emerald Lake Hills, San Mateo Co., California, USAFrom Brent Thorne, 7th Dec 2013 23:31:03