Geologic guides to carnotite deposits on the Colorado Plateau

Abstract

The carnotite deposits of the Colorado Plateau have been our principal domestic source of uranium and vanadium. Several of the geologic features associated with the deposits have been of considerable value in prospecting and they are now being used successfully by the U.S. Geological survey in its program of exploration drilling on the Colorado Plateau. The deposits occur in lenticular sandstone beds1 mostly in the Morrison formation. Sandstone less than about 40 feet thick rarely contains sizeable ore deposits. Sandstone that is pale to light brown, and speckled with stain, is most favorable; sandstone that has a pronounced reddish cast contains few deposits. Mudstone that is associated with the sandstone normally is red, but near ore deposits has been altered to gray. This altered mudstone is an indicator of ground favorable for ore. The presence of abundant carbonized plant remains in the ore-bearing sandstone also is a useful supplemental guide. Quantitative expressions of the value of these geologic features as guides to ore have been established as a result of recent studies by the Geological survey, based on geologic logs of more than 2,500 drill holes.