Unnamed Prospect (ARDF - BC090; near Black Crag), Petersburg Mining District, Wrangell City and Bourough, Alaska, USAi

Regional Level Types
Unnamed Prospect (ARDF - BC090; near Black Crag)	- not defined -
Petersburg Mining District	Mining District
Wrangell City and Bourough	Borough
Alaska	State
USA	Country

Location: This unnamed site is about a mile southeast of Black Crag near the Alaska-British Columbia boundary in section 36, T. 61 S., R. 88 E. The location is accurate.
Geology: Still and others (2002) found possible evidence of claim staking here and were told of drilling for molybdenum in the 50's but there is no information about exploration here prior to their work. They briefly examined the area and collected several mineralized samples as part of a regional mineral assessment for the Bureau of Land Management. The site might be part of the prospect several miles to the southwest (BC004) that was explored in the 1970's. The country rocks in the general area of Black Crag are a Miocene(?) alkali-feldspar granite stock and associated quartz-porphyritic rhyolite dikes (Koch, 1996). The prospect is near the margin of the stock, which intrudes Eocene granodiorite and quartz monzonite plutons and Mesozoic or Paleozoic pelitic schist and paragneiss. On the east side of the valley, Still and others (2002) collected several samples of float that consisted of: 1) quartz porphyry with molybdenite along fractures; 2) fine-grained silicified felsite cut by a 0.1-foot-thick seam of molybdenite; and 3) silicified granite with pyrite and chalcopyrite. Samples of the molybdenite-bearing rocks contained 735 and 1,348 parts per million (ppm) molybdenum and the copper-bearing sample contained 1,508 ppm copper. A sample of silicified breccia cemented by pyrrhotite contained 93 parts per billion gold, 43.5 ppm silver, and 558 ppm zinc. At the head of the valley under a hanging glacier, volcanic rock with molybdenite along fractures is abundant. Samples contained 23 to 2,529 ppm molybdenum, 119 to 713 ppm zinc, and up to 1,740 ppm cerium, 954 ppm lanthanum, 440 ppm neodymium, 60 ppm samarium, 72.6 ppb thorium, and 16 ppm uranium.
Workings: Still and others (2002) found possible evidence of claim staking here and were told of drilling for molybdenum in the 50's but there is no information about exploration here prior to their work. They briefly examined the area and collected several mineralized samples as part of a regional mineral assessment for the Bureau of Land Management. The site might be part of the prospect several miles to the southwest (BC004) that was explored in the 1970's.
Age: Tertiary or younger based on the age of the host rocks.
Alteration: Mineralized rocks are silicified.
Reserves: None.

Commodities (Major) - Ag, Au, Cu, Mo, Zn; (Minor) - Ce, La, Nd, Sm, Th, U
Development Status: None
Deposit Model: Porphyry Cu-Mo (Cox and Singer, 1986; model 21a)

Other Databases

Link to USGS - Alaska:	BC090

Other Regions, Features and Areas containing this locality

References