Unnamed Occurrence (ARDF - MH093; west of Eureka Glacier), Valdez Creek Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - MH093; west of Eureka Glacier)	- not defined -
Valdez Creek Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Location: This occurrence is at an elevation of about 5,300 feet, a third-mile west of lower Eureka Glacier. It is southeast of the center of section 27, T. 18 S., R. 7 E., Fairbanks Meridian. The occurrence corresponds to locality 38 in table 2 of Nokleberg and others (1991).
Geology: This occurrence is in Upper Triassic ultramafic and mafic rocks that are enclosed in a Tertiary to Cretaceous composite granitic to dioritic pluton (Nokleberg and others, 1991). Rose (1966 [ADMM GR 20, figure 3]) mapped dunite bodies within diorite, quartz diorite, and gabbro in this area. The Broxson Gulch thrust appears to form the hanging wall of the intrusive series, and it has been inferred that dunite bodies formed a well-lubricated layer in the footwall of the thrust (Kurtak and others, 1992, p. 94). The hanging wall of the thrust consists of schist. This occurrence consists of chromite and magnetite disseminated in a serpentinized olivine cumulate inclusion in metagranodiorite (Nokleberg and others, 1991, locality 38, table 2). Grab sample 79NK051D contained more than 0.5 percent chromium. Also at this site, rubble of olivine melagabbro and feldspathic peridotite hosts sulfide mineralization (W.T. Ellis, unpublished data, 2001). The rock float at this site appears to be derived from a sill-like body of Upper Triassic gabbro and serpentinized peridotite and dunite in the cliffs on the south side of the cirque to the west. The sulfide mineralization consists of coarse-grained clots and disseminations of pyrrhotite, chalcopyrite, and pentlandite. Sulfide abundance rarely exceeds about 5 percent in the float. Samples assay results had not been obtained by the time of this report (W.T. Ellis, unpublished data, 2001).
Workings: The occurrence was found during geologic reconnaissance (Nokleberg and others, 1991). Sulfide mineralization was discovered during July 2001 (W.T. Ellis, unpublished field notes, 2001). The occurrence is on active MAN Resources claims.
Age: Late Triassic, synchronous with emplacement of the mafic-ultramafic rocks.
Alteration: The olivine cumulates are serpentinized.

Commodities (Major) - Cr, Cu, Ni; (Minor) - Pd, Pt
Development Status: No
Deposit Model: Disseminated chromite in layered mafic-ultramafic complex and Ni-Cu-PGE in diffe

Other Databases

Link to USGS - Alaska:	MH093

Other Regions, Features and Areas containing this locality

References