Bear Lodge Mountains District

The Bear Lodge Mountains district in northeastern Wyoming was first prospected in 1875 after the discovery of gold in feldspar porphyry. The Bear Lodge Mountains form a core of multiple Eocene alkalic intrusives surrounded by domed Paleozoic and Mesozoic sedimentary rocks. Mineralization includes disseminated, vein, carbonatite and replacement deposits; disseminated REE (rare earth elements) and gold have the greatest resource potential (Hausel, 1989; 1997). A 1990 estimate by Gersic and others projected 84 million tons of ore at an average grade of 1.5 percent REO (rare earth oxides). Recent exploration drilling in the Bear Lodge Mountains has most likely refined this estimate.

Area of recent exploration, southeast of Warren Peak in the Bear Lodge Mountains.
Area of recent exploration, southeast of
Warren Peak in the Bear Lodge Mountains.

Further information on the Bear Lodge Mountains can be found in the following WSGS publications:

WSGS Map Series MS-78, Geologic map of the Sundance 30′ x 60′ Quadrangle, Crook and Weston counties, Wyoming and Lawrence and Pennington counties, South Dakota(Link to Geologic Mapping page), by Wayne M. Sutherland (2007), scale 1:100,000, 26 p.

WSGS Open File Report 2007-06, Preliminary Geologic Map of the Devils Tower 30′ x 60′Quadrangle (Link to Geologic Mapping page), by Wayne M. Sutherland (2007), scale 1:100,000, 26 p.