Uranium in the Gunnison County, Colorado
— Craig S. Goodknight

Uranium prospecting spread eastward from the Colorado Plateau in the middle and late 1950s to a more hard-rock environment in the area surrounding Gunnison. Two major uranium districts (Cochetopa and Marshall Pass) were discovered during that time, as were numerous uranium occurrences elsewhere in the area. More recently, in the late 1970s, the Gunnison country experienced renewed and more intense uranium exploration and development.

 

Approximately 1.2 million kg of L.1308 have been produced from the Gunnison country; over 99 percent of this has come from the Cochetopa and Marshall Pass districts. Uranium in both districts and many of the other occurrences is associated closely with fault and shear zones which cut brittle host formations (dolomites and sandstones) of Paleozoic and Mesozoic age. Minor uranium occurrences are in pegmatites and shear zones in Precambrian rocks, Cambrian vein material, and sandstones of early Tertiary age. Much of the information and basic data on the various uranium occurrences for this paper were collected from 1977-1979 during the evaluation of the Montrose (1°x2°) quadrangle by Bendix Field Engineering Corporation, under contract to the U.S. Department of Energy for the National Uranium Resource Evaluation (NURE) program. The reader is referred to the Montrose quadrangle evaluation report (folio) for additional information on uranium occurrences (many others having less than 0.01 percent U308) and favorability (Goodknight and Ludlam, 1981).

 

The area of Gunnison country for this paper is somewhat restricted to within the Montrose 1°x2° quadrangle boundary, and also excludes the area around Lake City; the boundary of the area described in this paper is shown in Figure 1. An index map (fig. 1) shows all the known occurrences of material containing at least 0.01 percent U308.