Bee Creek prospect (Dry Creek prospect), Alaska Peninsula District, Lake and Peninsula Borough, Alaska, USA
This prospect is located on land conveyed to or patented by the Bristol Bay Native Corporation.
Location: This prospect is in T. 42 S., R. 58 W., of the Seward Meridian, near the headwaters of an unnamed creek entering Dry Creek approximately 1 mile north of Chignik Bay. The location is accurate.
Geology: At this prospect sandstone, siltstone, argillite, and conglomerate of the Jurassic Naknek Formation have been intruded by a small dacite stock, which is surrounded by a sulfide system and alteration halo covering approximately 2 square miles (Fields, 1977). The intrusive is mainly dacite, but quartz diorite, andesite, and quartz porphyry have also been reported. The intrusive is part of a nearly east-west trending linear belt extending from Weasel Mountain (CG008) on the east to Cathedral Creek (CG001) on the west. The Bee Creek prospect was explored by Bear Creek Mining Company in 1975 and 1976 and by Resource Associates of Alaska in 1979 and 1981. The prospect is marked by a geochemical and color anomalies. Clusters of arsenic, copper, gold, lead, silver, and zinc anomalies surround the deposit. The main mineralized area is in a steep cirque basin that varies from 500 to 1,500 feet in elevation. Work by Resource Associates of Alaska (Anderson and others, 1979) suggest that mineralization may extend southwest into the McKinsey Valley. The mineralization is mainly at the border of the dacite stock in arkose, conglomerate, and quartzite. Resource Associates of Alaska (Anderson and others, 1979) claim that the hornfelsed sediments near the contact contain the best mineralization and that the mineralization decreases towards the core of the intrusive. The age of the mineralization is between 3.2 and 3.8 million years (Wilson, 1980). The deposit is a porphyry copper. Chalcopyrite and pyrite occur in a stockwork of hairline fractures containing quartz-sulfide veinlets throughout an area about 2,000 feet in diameter. Disseminated chalcopyrite and pyrite occur in biotitized hornfels and these sulfides replace mafic minerals in the dacite. Molybdenite is finely disseminated in quartz veinlets, in gypsum veinlets, and in clots of chalcopyrite. Pyrite forms a halo on the periphery of the system. Some magnetite veins have been reported; they appear to be early in the mineralization sequence and contain no sulfides. Veins containing lead and zinc values are peripheral to the copper zone. Within the copper zone, richer surface samples contained 500 to 2,000 parts per million (ppm) copper, 0.04 to 0.18 ppm gold, 20 to 220 ppm molybdenum, and 0.4 to 0.18 ppm silver (Fields, 1977). Secondary biotite is widely distributed both within and beyond the chalcopyrite zone. It replaces mafic minerals and forms fine-grained aggregates both in the pluton and in the surrounding sediments. The biotite zone centers on the stock and extends irregularly southward over an area of 1,500 by 3,400 feet. Discontinuous zones of sericitic alteration are peripheral to the biotite zone and are locally superimposed on the potassic and propylitic alteration. Propylitic alteration of chlorite and epidote forms an outer alteration zone. A strong zone of argillic alteration located between the phyllic and propylitic zones also has been reported (Butherus and others, 1981). Bear Creek drilled 5 holes in the copper zone in 1975-76. Four holes averaged 500-1200 ppm copper and 5-28 ppm molybdenum. The best hole averaged 0.25 percent copper, 0.01 percent molybdenum, and 0.06 ppm gold over 500 feet. In 1979 Resource Associates of Alaska discovered two areas of polymetallic quartz veins. Samples of this material contained up to 5700 ppm copper, 4.4 ppm gold, 1.18 percent lead, 530 ppm molybdenum, 4.2 ounces silver per ton, and 1.62 percent zinc (Anderson and others, 1979). A resource of 4.5 to 9 million tonnes grading 0.25 percent copper and 0.01 percent molybdenum has been estimated (Young and others, 1997). Full Metal Minerals and Metallica Resources drilled 2 holes on the Bee Creek porphyry in 2006 that totaled 1,000 meters (Full Metal Minerals, 2008, Alaska Peninsula; Metallica Resources, 2008) They interpret the deposit as a multiphase dioritic intrusion within a coincident copper-gold-molybdenum anomaly centered on a magnetic high about 2 kilometers in diameter. Notable intercepts in the two holes were: 1) 34 meters that contained 0.26 percent copper and 0.085 gram of gold per ton, 2) ll8 meters that contained 0.32 percent copper and 0.212 gram of gold per ton, and 3) 40 meters that contained 0.51 percent copper and 0.212 gram of gold per ton. The holes were mostly in sedimentary rocks cut by numerous intermediate to felsic dikes. The copper mineralization is mostly in hornfelsed sedimentary rocks; some is in altered diorite as stockworks of quartz-magnetite-chalcopyrite veinlets.
Workings: In 1975-76 Bear Creek Mining Company did detailed mapping and sampling and drilled 5 holes totaling 1,865 feet. Resource Associates of Alaska explored the deposit in 1979 and 1981. Additional mapping and sampling was done by the U.S. Geological Survey in 1980 and 1981. Full Metal Minerals and Metallica Resources drilled 2 holes on the Bee Creek porphyry in 2006 that totaled 1,000 meters (Full Metal Minerals, 2008, Alaska Peninsula; Metallica Resources, 2008).
Alteration: The alteration at this prospect appears to be the classic porphyry type with a potassic core grading outward through phyllic, argillic, and propylitic alteration zones although these may not all be developed fully. The best copper mineralization is in the potassic zone.
Reserves: The prospect contains an estimated resource of 4.5 to 9 million tonnes grading 0.25 percent copper, 0.01 percent molybdenum, and trace gold.
Commodities (Major) - Ag, Au, Cu, Mo; (Minor) - Pb, Zn
Development Status: None
Deposit Model: Porphyry copper; porphyry copper-molybdenum (Cox and Singer, 1986; models 17, 2
References- Anderson, G.D., Fitch, G.M., Lappie, D.W., Lindberg, P.A., and Fankhauser, R.E., 1979, Exploration and evaluation of Bristol Bay Native Corporation Lands, Vol. II, Book 1: Prepared for Houston Oil and Minerals Company by Resource Associates of Alaska, 78 p. (Report held by Alaska Earth Sciences, Inc., Anchorage, Alaska.)
- Butherus, D.L., White, D.C., Smith, W.H., Radford, G., Sandberg, R.J., and Pray, J.C., 1981, Exploration and evaluation of precious metal potential of Bristol Bay Native Corporation Lands, southwest Alaska, 1981, Vol. 1: Prepared for NERCO by Resource Associates of Alaska, 90 p. (Report held by Alaska Earth Sciences, Inc. Anchorage, Alaska.)
- Cox, D.P., Detra, D.E., and Detterman, R.L., 1981, Mineral resource maps of the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF- 1053-K, 2 sheets, scale 1:250,000.
- Fields, E.D., 1977, 1976 Annual report: Alaska search, Chignik area-Bristol Bay region: Bear Creek Mining Company, 44 p., 22 map sheets. (Report held by the Aleut Corporation, Anchorage, Alaska.)
- Full Metal Minerals, 2008 (Alaska Peninsula): http://www.fullmetalminerals.com/s/alaskapeninsula.asp (as of March 4, 2008).
- Metallica Resources Inc., 2008; Exploration - Southwest Alaska:
- Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.
- Wilson, F.H., 1980, Late Mesozoic and Cenozoic tectonics and age of porphyry copper prospects, Chignik and Sutwik Island quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 80-543, 94 p., 5 sheets, scales 1:250,000 and 1 inch = 1,000 feet.
- Wilson, F.H., and Cox, D.P., 1983, Geochronology, geochemistry, and tectonic environment of porphyry mineralization in the central Alaska Peninsula: U.S. Geological Survey Open-File Report 83-783, 24 p.
- Young, L.E., St. George, P., and Bouley, B., 1997, Porphyry copper deposits in relation to the magmatic history and palinspastic restoration of Alaska, in: Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 306-333.
- Singer, D.A., Berger, V.I., and Moring, B.C. (2008): Porphyry copper deposits of the world: Database and grade and tonnage models, 2008. US Geological Survey Open-File Report 2008-1155.
17 entries listed. 14 valid minerals.
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New Locality Added: Gleann Dubh, Morven peninsula, North West Highlands (Argyllshire), Scotland, UKFrom Paul Render, 6th Dec 2013 21:44:31