Colorado Plateau Deposits

uranium and vanadium deposits in the United States, located in the states of Colorado, New Mexico, Arizona, and Utah. Area, 375,000 sq km.

The deposits have been known since 1898. In 1905—48 (with interruptions) they were mined for vanadium. In 1910–23 uranium and radium were also extracted from the carnotite ores. As a result of the prospecting that started in 1948, the Colorado Plateau deposits are numbered among the major uranium areas of the world. The reserves of uranium and vanadium ores (according to a 1969 estimate) were 50 million tons and the uranium reserves in them, 111,400 tons (with an average content on the order of 2 kg of uranium per ton of ore). Around 75 percent of these reserves is located at the Ambrosia Lake deposit in New Mexico. In 1969 the uranium output of the Colorado Plateau deposits was 75 percent of the total uranium output in the United States. The deposits are structurally confined to a Precambrian median mass. The uranium and vanadium ores occur in platform mantle composed of sedimentary rock (predominantly sandstone and schists with intercalations of conglomerates, limestones, and argillites). A predominant portion of the uranium (98 percent) is mined from Jurassic (the Morrison formation) and Triassic deposits (Chinle and Shinarump formations).

The ore bodies have a lenticular shape and lie conformingly to the bedding of the rock. Also characteristic are unique ore bodies (“rolls”) with curvilinear edges in the cross section. The area of the ore bodies varies from hundreds to tens of thousands of square meters, and the thickness is from several centimeters to 30 meters. The primary ores contain uranium in the form of low-valent compounds, such as pitchblende and coffinite; vanadium is found in the form of montroseite. Oxidized ores are characterized by the development of high-valent uranium and vanadium compounds, chiefly carnotite and tyuyamunite. In addition to the uranovanadates, vanadates of calcium, iron, and other elements are also present.