Pioneer

Prospects, Active

Alternative names

Eastern Star
Rainbow
Ghezzi

Commodities and mineralogy

Main commodities Ag; Au; Cu
Ore minerals chalcopyrite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-4
Latitude 63.3134
Longitude -145.9856
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

Geologic description

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).
Geologic map unit (-145.987861163904, 63.3129815230303)
Mineral deposit model Porphyry Cu (Cox and Singer, 1986; model 17).
Mineral deposit model number 17
Age of mineralization Late Triassic.
Alteration of deposit The propylitically altered gabbro contains saussuritized and albitized plagioclase, and the mafic minerals are altered to actinolite (Rose, 1965).

Production and reserves

Workings or exploration
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.
Indication of production None

Additional comments

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.

References

MRDS Number A011786

References

Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 6/10/2002