Prospect, Inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; As; Ba; Cu; Sb
Ore minerals barite; galena; marcasite; pyrite; sphalerite
Gangue minerals fluorite; quartz

Geographic location

Quadrangle map, 1:250,000-scale HW
Quadrangle map, 1:63,360-scale C-5
Latitude 68.5694
Longitude -158.6833
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Drenchwater-East prospect is near the southwest corner of section 15, T. 10 S., R. 29 W., about 3.3 miles southwest of the junction of Wager Creek and Drenchwater Creek. It is part of a belt of similar mineralization that extends for about a mile to the northwest (also see HW003 and HW004).

Geologic setting

Geologic description

The Drenchwater deposits were found in 1975 by the U.S. Geological Survey and several comprehensive studies were done by the USGS and the U.S. Bureau of Mines from 1977 to 1992 that included detailed mapping, geochemical and geophysical surveys, and much sampling (Jansons and Baggs,1980; Jansons, 1982; Nokleberg and Winkler, 1978,1982; Kurtak and others, 1995). Anaconda Exploration explored the deposits in 1980 and in 1993 the Arctic Slope Regional Corporation and Kennecott Exploration applied for a permit to drill. The permit was turned down by the Bureau of Land Management because the area was part of the National Petroleum Reserve that is closed to exploration and mining.
The Drenchwater-East deposit is one of three similar deposits that form a belt about 1.2 miles long (see also Drenchwater Creek (HW004) and Drenchwater-West (HW003)). The deposits are in the Drenchwater Fenster, where the Key Creek sequence consists of the Kuna, Siksikpuk, Otuk and Okpkkruak Formations of Mississippian to Cretaceous age. The structure of the area is dominated by a series of south-dipping thrust faults that intensely deformed the rocks. The stratiform mineralization is mostly in carbonaceous shale and silicified mudstone, associated with altered volcanic rocks, mainly submarine felsic tuffs, and lesser mafic volcanics including trachyte, trachyandesite, and basalt. The mineralization is associated with silicification of the shale, mudstone, and volcanic rocks.
There are four types of mineralization: semi-massive; disseminated; layered diagenetic; and breccia-cemented. Sphalerite is the dominant sulfide; variable amounts of pyrite, marcasite, and galena occur; there are rare fluorite and barite; and anomalous silver, arsenic, and antimony show up in assays of the ore. Samples contained up to 23 percent zinc, 5.1 percent lead, 1,150 parts per million (ppm) copper and 15 ppm silver. Biotite from volcanic rocks interbedded with the mineralization has K-Ar ages of 319+10 and 330+17 Ma. A sample of galena has a Pb-isotope model age of 200 Ma. Most of those who have studied the deposits interpret them to be volcanogenic massive-sulfide deposits.
Geologic map unit (-158.686294588045, 68.568849714671)
Mineral deposit model Volcanogenic lead-zinc massive sulfide deposit (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Biotite from volcanic rocks interbedded with the mineralization has K-Ar ages of 319+10 and 330+17 Ma. A sample of galena has a Pb-isotope model age of 200 Ma.
Alteration of deposit Widespread silicification of shale and volcanic host rocks.

Production and reserves

Workings or exploration Several detailed studies of the prospect from 1975 to 1992 by the U.S. Geological Survey and the U.S. Bureau of Mines included geological mapping, geochemical and geophysical surveys, and considerable sampling. Explored by Anaconda Exploration in 1980.
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

MAS number 0020200002.


MRDS Number A015681


Reporters M.T. Powers, D.F. Huber, J.M. Schmidt and J.H. Dover (U.S. Geological Survey); D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/18/2010