Unnamed Prospects (ARDF - MH052; western 'Joy Creek' area), Valdez Creek Mining District, Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
Unnamed Prospects (ARDF - MH052; western 'Joy Creek' area)	- not defined -
Valdez Creek Mining District	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

Location: A cluster of mineral occurrences and prospects is about one-quarter mile west-northwest of the center of section 29, T. 19 S., R. 5 E., Fairbanks Meridian. This cluster includes mineral localities 1 to 3 on plate 2 of Clautice and others (1989). These localities probably correspond to localities 13 and 14 in table 2 of Nokleberg and others (1991) and locality 12 in figure 4 of Cobb (1979 [OFR 79-238]). This area is also described by Clautice and others (1989) and Smith and others (1973). The prospects are included in the locally named 'Joy Creek' area, which was mapped in detail by R.A. Blakestad and G.A. Moerlein (written communications, 1980).
Geology: The mineral occurrences in this area are in the footwall of a major low-angle thrust fault. The hanging wall of the thrust is composed of argillite and graywacke of Jurassic to Cretaceous age (Clautice and others, 1989, plate 1). The footwall host rocks of the mineral deposits are mainly highly faulted andesite-basalt of probable Late Triassic age. A pyritic felsic body has been emplaced along the thrust (?) fault in this locality (Clautice and others, 1989). Clautice and others (1989) described the following deposits (localities 1 to 3): quartz-carbonate veins in brecciated greenstone assayed as much as 1,880 parts per billion (ppb) gold, 1,080 parts per million (ppm) lead, and 5,990 ppm zinc. Although galena and sphalerite are not reported at locality 1, the lead and zinc values indicate their probable presence. The deposit at locality 2 contains more than 1 percent copper in malachite-stained greenstone. The deposit at locality 3 contains abundant pyrite in greenstone; the pyrite is extensively altered to limonite, and chalcopyrite, azurite, and malachite are abundant locally. This last deposit is probably at the site reported by Clautice and others (1989) and Smith and others (1973) and by Cobb (1979 [OFR 79-238, locality 12, figure 4). It also probably corresponds to locality 13 of Nokleberg and others (1991, table 2), who reported the presence of bornite and iron-bearing carbonate minerals; a sample assayed 2.4 percent copper and 5 ppm silver. R.A. Blakestad (written communication, 1980) reported about 0.5 ppm gold in black Triassic argillite in the fault footwall of Jurassic argillite at sites close to those visited by Clautice and her associates. The prospect is fairly old. Clautice and others (1989) noted a few shallow prospect pits near locality 3 of Clautice and others (1989). The so-called Joy Creek area was mapped in detail by Blakestad in 1980.
Workings: A few shallow prospect pits were dug before about 1970 (Clautice and others, 1989). The area was studied in reconnaissance by Clautice and others (1989) and in detail by Rodney A. Blakestad (written communication, 1980).
Age: Probably mid- to Late Cretaceous, during a period of regional deformation.

Commodities (Major) - Cu; (Minor) - Ag, Au, Pb, Zn
Development Status: None
Deposit Model: Diverse polymetallic deposits in footwall of a major thrust fault.

Other Databases

Link to USGS - Alaska:	MH052

Other Regions, Features and Areas containing this locality

References