Ore controls in sandstone uranium deposits of the Colorado Plateau

Abstract

Marked lithologic control characterizes most uranium deposits in sandstone formations of the Colorado Plateau. Deposits in rocks ranging in age from the Cutler formation of Permian age to the Wasatch formation of Eocene age are primarily in 1) fluvial sandstones which, 2) contain carbonized plant matter, 3) are light-colored or gray, rather than red, and 4) contain feldspar or mica. In addition, 5) sandstones that are inter-bedded with or interfinger with shales or mudstones are particularly favorable. These features are also characteristic of most sedimentary copper deposits.Most uranium deposits in sandstone formations show no immediate connection with tectonic features, but a general clustering of orebodies around large positive structures is noted. The reason for this is not clear.It is postulated that at least some of the uranium in the ores was derived from the same source as the host rocks. In this light the sand-stone uranium deposits may be the continental analogue of uranium-rich marine black shales and phosphorites. Sedimentary copper deposits may have had a similar origin. Uranium moving seaward in streams, during erosion of a land mass, may be fixed on the continent in certain favorable fluvial environments.