Berg Basin Prospect, Petersburg Mining District, Wrangell City and Bourough, Alaska, USAi

Regional Level Types
Berg Basin Prospect	Prospect
Petersburg Mining District	Mining District
Wrangell City and Bourough	Borough
Alaska	State
USA	Country

Location: This is a well documented prospect on a unnamed south-flowing tributary to the north end of Berg Creek. However, an extended ground and air search for the prospect by Jan Still of BLM and D. J. Grybeck of the USGS in 1996 showed that the area was covered with thick vegetation and talus; the adit was only seen from the air and difficult of access. The prospect is at an elevation of about 1,780 feet at the top of a steep talus slope about 0.5 mile southwest of the center of section 32, T. 63 S., R. 86 E.
Geology: This prospect was discovered in 1907. It was explored by several surface pits, a tunnel about 800 feet long, and several hundred feet of diamond drilling in 1947 and 1948 (Fowler, 1950) Seven men were working at the property then but apparently there has been no work since. The country rocks in the area are biotite schist and subordinate marble and calc-silicate rocks that are intruded by Eocene tonalite and granodiorite and by younger dikes and sills of rhyolite, basalt, and pegmatite (Brew and others, 1984). The deposit consists of a stockwork of quartz veinlets carrying pyrite, galena, and sphalerite, and of sporadic small masses of sphalerite and galena (Gault and others, 1953; Still and others, 2002). Some of the veins contain moderate values of gold and silver. The small sulfide masses occur in a composite basaltic dike, in thin breccia zones along the contacts of basalt and rhyolite dikes and sills, along contacts of basalt dikes with schist near rhyolite, and disseminated in the rhyolite. One diamond drill hole intersected 5 feet of solid and disseminated galena. No galena or sphalerite have been found except where basaltic dikes are associated with rhyolite sills and dikes. The galena contains up to 28 ounces of silver per ton. A quartz vein reported to carry about 0.68 ounce of gold per ton crops out at the surface but could not be found in the underground workings.
Workings: This prospect was discovered in 1907. It was explored by several surface pits, a tunnel about 800 feet long, and several hundred feet of diamond drilling in 1947 and 1948 (Fowler, 1950) Seven men were working at the property then but apparently there has been no work since.
Age: The age of the deposit is inferred to be mid-Cenozoic, based on its spatial and apparently genetic association with dikes and sills that cut the Eocene tonalite.
Reserves: None.

Commodities (Major) - Ag, Au, Pb, Zn; (Minor) - Cu
Development Status: Undetermined.
Deposit Model: Polymetallic veins? (Cox and Singer, 1986; model 22c).

Other Databases

Link to USGS - Alaska:	PE042

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References