Results of diamond drilling and geologic investigation of the Shirley May (Garo) uranium deposit, Park County, Colorado

Abstract

The Shirley May (Garo) uranium deposit near Garo, Park County, Colo., consists of tyuyamunite and carnotite that occur as disseminations and as fracture fillings in three beds of medium- to coarse-grained sandstone. The sandstones are in the Maroon formation of Permian age. This deposit was explored by means of 12 core-drill holes, totalling 2,003 feet. The deposit is on the northeast flank of the Garo anticline, a local structure that probably is related to Tertiary tectonic movement. In the vicinity of the deposit the sedimentary rocks strike northwest and dip steeply. They are cut by numerous northerly-trending faults that have horizontal displacements of as much as 1,000 feet. The ore minerals tyuyamunite, carnotite, volborthite, calciovolborthite, malachite, azurite, chalcocite(?) , and an unidentified yellow to dark-red vanadium oxide are restricted to a complexly faulted area. The ore body that has yielded most of the uranium ore is in the uppermost ore-bearing sandstone (bed no. 1) and is stratigraphically 50 and 150 feet above the ore horizons in sandstones nos. 2 and 3, respectively. The uranium content of samples from the mine workings ranges from 0. 001 to 0. 48 percent uranium; dump samples contain as much as 2.39 percent uranium. A total of 40 tons of uranium ore, averaging 1.0 percent uranium, was produced in 1919.