Ann Creek Prospect (Bee Mining), Delta River Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Ann Creek Prospect (Bee Mining)	Prospect
Delta River Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Mineralization at the prospect is similar to that at the Rainbow Mountain prospect (Emerick) (MH209).
Location: This prospect is located at an elevation of 3,200 feet in a north tributary to lower Ann Creek. It is just south of the center of section 23, T. 18 S., R. 10 E., Fairbanks Meridian. The site corresponds to locality 3 of Rose (1965) and locality 11 of Cobb (1979 [OFR 79-238]); it combines localities S84 and S85 in table 2 of Nokleberg and others (1991). It is the same as Foley's (1992) Ann Creek showing.
Geology: A tabular intrusive body of partly serpentinized ultramafic and gabbroic rocks that trends approximately east-west is exposed in a small creek on the north side of Ann Creek (Rose, 1965). North of the intrusion the rocks are dark, siliceous sedimentary rocks and light-colored tuff. To the south they are andesitic and dacitic volcanic rocks. The rocks are part of the Slana Spur Formation of Pennsylvanian age, but their differences on either side of the ultramafic body suggest that they were intruded along a fault (Rose, 1965). Airborne magnetic data indicated that this body may connect with the Rainy ultramafic-mafic intrusion (Late Triassic age) 3 miles to the west (see MH164) (W.T. Ellis, oral communication, 2001). The rocks in the Ann Creek body vary from fairly fresh dunite, peridotite, and mafic gabbronorite to serpentinite. A dike of serpentinized peridotite extends southeastward from the mafic gabbro, and it appears to be cut off by a fault. Near the east end of the ultramafic zone, shattered and serpentinized diorite or quartz diorite is in contact with the dunite. According to Rose (1965), the diorite may be a differentiate of the ultramafic-gabbro sequence. Small lenses of massive sulfide occur in an approximately 50-foot-thick zone of of gabbro that also contains disseminated pyrrhotite, pyrite, pentlandite, chalcopyrite, and a trace of galena (Rose, 1965, locality 3). Serpentinite at this location also carries small amounts of sulfides. Disseminated and massive sulfide samples contained 0.17 to 2.01 percent nickel and 0.1 to 0.61 percent copper (Saunders, 1962 [PE 68-08]). Samples of sulfides from a 1-foot vein (several hundred feet southwest of Rose's locality 3) assayed 0.20 ounce of gold per ton and 0.32 ounce of silver per ton (Rose, 1965). A sample of a massive sulfide lens in the Ann Creek ultramafic body contains 1.9 percent nickel, 3.5 percent copper, 0.02 percent cobalt, 540 parts per billion (ppb) palladium, and 340 ppb platinum (Foley, 1992). Sperrylite was identified in a gabbronorite sample that contained 0.44 percent nickel, 0.3 percent copper, 0.02 percent cobalt, and 340 ppb palladium.
Workings: Disseminated and massive sulfide samples contained 0.17 to 2.01 percent nickel and 0.1 to 0.61 percent copper (Saunders, 1962 [PE 68-08]). Samples of sulfides from a 1-foot vein (several hundred feet southwest of locality 3) assayed 0.20 ounce of gold per ton and 0.32 ounce of silver per ton (Rose, 1965). A sample of a massive sulfide lens in the Ann Creek ultramafic body contains 1.9 percent nickel, 3.5 percent copper, 0.02 percent cobalt, 540 parts per billion (ppb) palladium, and 340 ppb platinum (Foley, 1992). Sperrylite was identified in a gabbronorite sample that contained 0.44 percent nickel, 0.3 percent copper, 0.02 percent cobalt, and 340 ppb palladium.
Age: Late Triassic.
Alteration: Local serpentinization.

Commodities (Major) - Ag, Au, Cu, Ni; (Minor) - Cr, Pb, Pd, Pt
Development Status: Undetermined.
Deposit Model: Ni-Cu-PGE in differentiated mafic-ultramafic sill.

Other Databases

Link to USGS - Alaska:	MH166

Other Regions, Features and Areas containing this locality

References