Black Creek (lode)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au; Cu
Other commodities As; Bi
Ore minerals arsenopyrite; chalcopyrite; gold; pyrite; pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale HU
Quadrangle map, 1:63,360-scale A-2
Latitude 66.0764
Longitude -153.8631
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is located on Black Creek, upstream from the placered area (HU022). The occurrence is at an elevation of about 2,000 feet on the west side of Black Creek, about 0.3 mile south of the center of section 20, T. 8 N., R. 24 E., of the Kateel River Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence consists of disseminated pyrite and traces of chalcopyrite in Cretaceous metavolcanic rocks and late-stage aplite near the margin of a Cretaceous, granodiorite-quartz monzonite pluton (Miller and Ferrians, 1968). The occurrence is upstream from the placer gold area on Black Creek (HU022). Grab samples collected by Miller and Ferrians, described as pyritiferous hornfels and pyritiferous, felsic-intrusive rock, contain disseminated sulfides, 1,000 copper and up to 0.05 ppm gold.
Kurtak and others (1999) describe the geology as interbedded graywacke and mudstone that have been metamorphosed to resistant , brown hornfels along the contact of the granodiorite/quartz monzonite. They also observed quartz cemented breccia zones, quartz veinlets, felsic dikes, and lesser porphyritic andesite(?) cutting the sediments and hornfels. The graywacke and hornfels contain 1-2% pyrrhotite and minor arsenopyrite that occur as disseminations and stringers. Quartz veinlets contain a little chalcopyrite. The sulfides appear to be more prevalent near the felsic dikes. Samples contain up to 611 ppb gold, 3,912 ppm copper, 2,676 ppm arsenic, and 473 ppm, bismuth.
Nokleberg and others (1996) describe, without a specific location, the general Indian Mountain area as a porphyry Cu-Au system. This system, which likely includes all the individual lode occurrences within the area, consists predominately of chalcopyrite- and tourmaline-bearing intrusive breccias that are surrounded by concentric phyllic-argillic-propylitic alteration halos. A pyrite zone surrounds the intrusive rocks.
Geologic map unit (-153.865731902329, 66.0758622583072)
Mineral deposit model Porphyry Cu-Au? (Cox and Singer, 1986; model 20c?).
Mineral deposit model number 20c?
Alteration of deposit Fine-grained, pyritiferous intrusive rocks in the area are reported to be highly altered but there is no detailed description of the alteration.

Production and reserves

Workings or exploration Only surface sampling.
Indication of production None

References

MRDS Number A015582

References

Bottge, R.G., 1988, Maps summarizing land availability for mineral exploration and development in western Alaska, 1986: U.S. Bureau of Mines Open-File Report 14-88, 38 quadrangle overlays.
Reporters J.M. Britton (Anchorage)
Last report date 8/1/2002