Commodities
PrimaryCopper, Molybdenum
SecondarySilver, Zinc, Tungsten, Lead
Commodity typeM
Materials
Ore mineralsArgentojarosite, Beudantite, Chalcocite, Chalcopyrite, Covellite, Jarosite, Molybdenite, Pyrite, Pyrrhotite, Sphalerite, Copper
GangueActinolite, Andalusite, Anhydrite, Calcite, Chlorite, Epidote, Garnet, Goethite, Hematite, Jarosite, Kaolinite, Limonite, Montmorillonite, Quartz, Siderite
Geology
Host rockDacite
AlterationAlteration consists of early potassic and propylitic alteration in the microbreccia and earlier porphyritic intrusions, and later sericite-quartz-pyrite alteration throughout the intrusive complex. The deposit also has undergone supergene enrichment, and calcareous schists near the complex have undergone calc-silicate hornfelsing and iron metasomatism.. The early potassic and propylitic alteration centers around a 330-foot- diameter zone of stockwork quartz veins. Potassic alteration extends west for about 3600 feet, and gradually transitions to propylitic alteration. Quartz veins in the stockwork zone make up to 90% of the rock. Older, smaller 'A'- type veins containing potassium-feldspar margins locally contain molybdenum, pyrite, and chalcopyrite. Younger, larger, 'B'- type veins usually contain molybdenum in their cores or along selvages. Sericite, anhydrite, and andalusite occur along some vein margins.. The propylitic alteration consists of chlorite, epidote, calcite, actinolite, montmorillonite, and chalcedonic quartz. The later sericite-quartz-pyrite alteration is fracture controlled and pervasive through the intrusive complex.. A zone of supergene enrichment underlies the oxide (gossan) zone, which typically is 300-400 feet deep. The supergene zone contains chalcocite and sparse covellite and native Cu, as well as pyrite and chalcopyrite. Within the oxide zone, goethite, hematite, jarosite, and limonite are common. The oxidation of these rocks results in the formation of a kaolinite-sericite-quartz assemblage that is leached of all sulfides.
Economic & production
Development statusProspect
Identification
Deposit ID10002531
MRDS IDA013473
Alternate namesTim's Greisen
RegionNA
Data scoreB
Coordinates64.17638, -157.57004
References
Gemuts, I., Puchner, C.C., and Steefel, C.I., 1983, Regional geology and tectonic history of western Alaska, western Alaska geology and potential: Alaska Geological Society Symposium, Anchorage, Alaska, Feb. 16-18, 1982, p. 57-85.Harris, T.D., 1985, Geology of the Round Top porphyry copper-molybdenum deposit, west-central Alaska: University of Colorado, Boulder, M.Sc. thesis, 202 p.Flanigan, B., 1998, Genesis and mineralization of ore deposits in the Illinois Creek region, West Central Alaska: University of Alaska, Fairbanks, M.Sc. thesis, 125 p., 2 plates.