Pioneer; Eastern Star; Rainbow; Ghezzi Prospects, Delta River Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Pioneer; Eastern Star; Rainbow; Ghezzi Prospects	Group of Prospects
Delta River Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

A sulfur isotope analysis by American Copper and Nickel returned a Del S34 value of 0 (W.T. Ellis, oral communication, 1996). A zero value suggests that the mineralization is probably primary magmatic in origin.
Location: This prospect area is centered near the southwest end of a small ridge above the divide between North Fork and West Fork Rainy Creek. It is at an elevation of about 4,900 feet in the SE1/4NE1/4 section 34, T. 18 S., R. 9 E., Fairbanks Meridian. It corresponds to locality 5 of Rose (1965), locality 3 of Cobb (1979 [OFR 79-238]), and locality S61 in table 2 of Nokleberg and others (1991).
Geology: The rocks in the prospect area are amphibole 'serpentinite' intruded by two main varieties of gabbro: dark, fine-grained, unmineralized gabbro, and dikes, pods, and plugs of a light-colored propylitically altered and mineralized leucogabbro (Rose, 1965). The mineralization consists of chalcopyrite and pyrite in fractures in shear zones and as disseminations. The gabbro is Late Triassic; it intrudes the Slana Spur Formation of Pennsylvanian age (Nokleberg and others, 1991). The shear zones strike northeast and range to as much as a meter wide and several meters long. A composite surface sample of the mineralized gabbro assayed 1.0 percent copper, 0.01 ounce of gold per ton, and 0.22 ounce of silver per ton (Rose, 1965). A U.S. Geological Survey grab sample contained 6.0 percent copper and 0.017 ounce of gold per ton (Nokleberg and others, 1991).
Workings: Workings include several pits and trenches and an undetermined number of drill holes completed in 1974 (W.T. Ellis, oral communication, 1996). A composite surface sample of the mineralized gabbro assayed 1.0 percent copper, 0.01 ounce of gold per ton, and 0.22 ounce of silver per ton (Rose, 1965). A U.S. Geological Survey grab sample contained 6.0 percent copper and 0.017 ounce of gold per ton (Nokleberg and others, 1991). The occurrence is on active claims of MAN Resources.
Age: Late Triassic.
Alteration: The propylitically altered gabbro contains saussuritized and albitized plagioclase, and the mafic minerals are altered to actinolite (Rose, 1965).

Commodities (Major) - Ag, Au, Cu
Development Status: None
Deposit Model: Porphyry Cu (Cox and Singer, 1986; model 17).

Other Databases

Link to USGS - Alaska:	MH148

Other Regions, Features and Areas containing this locality

References