Location: This occurrence is at an elevation of 900 feet, about 1.2 miles north-northwest of the top of Spine Mountain, and about a mile east of Helen Todd Lake. The site is in section 12, T. 77 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 13 in Karl (1992). The location is accurate within 0.1 mile.

Geology: The country rocks in the area of this site are Upper Jurassic or Cretaceous flyschlike metasedimentary rocks that are gradationally interbedded with subordinate andesitic or basaltic metatuff (Berg, 1972 [I 684]; Berg and others, 1988; Karl, 1992). The area also contains small, generally fault-bounded, outcrop areas of recrystallized Upper Triassic basalt and limestone. The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrence consists of augite-porphyritic, Jurassic or Cretaceous, metatuff (greenstone) containing about five percent of disseminated sulfides, mainly pyrite and chalcopyrite (Karl, 1992). The greenstone is cut by quartz veins up to about 2 feet thick. A sample of the greenstone contained 3 ppm Ag, 200 ppm Cu, 100 ppm Co, 150 ppm Cr, and 150 ppm Ni (Karl, 1992, loc. 13).

Workings: A sample of the greenstone contained 3 ppm Ag, 200 ppm Cu, 100 ppm Co, 150 ppm Cr, and 150 ppm Ni (Karl, 1992, loc. 13).

Age: Disseminated sulfide mineralization may in part be cogenetic with Upper Jurassic or Cretaceous deposition of the metatuff (greenstone) hostrock. Fissure veins probably are Late Cretaceous or younger.

Alteration: Country rocks are pyritized.

Commodities (Major) - Ag, Cu

Development Status: None


Deposit Model: In part, possibly low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	KC168

Other Regions, Features and Areas containing this locality

References