Location: This record covers a scattering of several occurrences in an area about 5 miles by 2 1/2 mile in size with the long dimension oriented north. The center of the area is east of the head of Big John Creek near hill 1908 which is southwest of Towers Lake and about 0.3 mile southwest of the center of section 14, T. 58 S., R. 74 E.

Geology: This site was originally of interest because of widespread geochemical anomalies in a large suite of elements, zinc in particular. The samples commonly contain anomalous copper, molybdenum, and nickel, and various samples were anomalous in silver, lead, cadmium, manganese, mercury, arsenic, and antimony (Bittenbender and others, 2001). Still and others (2002) indicate that the suite suggests the presence of volcanogenic massive sulfide deposits. In following up these anomalies, they found several occurrences of mineralization in scattered borrow bits and road cuts. None seemed to explain the magnitude of the widespread geochemical anomalies but they do lend support to the concept of massive sulfide mineralization in the area. The rocks in the area are part of the Cannery Formation of Permian and Mississippian age (Karl and others, 1999); they are a heterogeneous unit of chert, cherty argillite, silicified limestone, siltstone, and graywacke, with minor conglomerate, tuff, and volcanic rocks. In the three most notable areas of outcrop where the mineralization was found, it consists of: 1) pyrite in seams and layers in a 20-foot-thick unit of silicified schist, chert, and graphitic schist, 2) seams and patches of fine-grained to crystalline pyrite in quartz veins and silicified schist and slate, and 3) layers of pyrite up to 2 inches thick in a layer of silicified schist at least 10 feet thick in a unit of argillite. Numerous samples were collected and analyzed. None had high values in any of the common ore elements but many had values above background. The highest values were 136 parts per billion gold, 1,762 parts per million (ppm) zinc, 0.9 ppm silver, 166 ppm copper, 920 ppm lead, 727 ppm arsenic, 486 ppm nickel, and 9,176 ppm barium.

Workings: The only work was sampling by the Bureau of Land Management during a regional mineral assessment.

Age: Probably contemporaneous with the Permian and Mississippian host rocks.

Alteration: The schists is commonly silicified.

Commodities (Major) - Au, Ba, Co, Zn; (Minor) - As,Cu, Hg, Ni, Pb, Sb
Development Status: None
Deposit Model: Volcanogenic massive sulfide deposit.

Other Databases

Link to USGS - Alaska:	PE083

Other Regions, Features and Areas containing this locality

References