Paradox Basin Uranium-Vanadium Deposits: Comparative Mineralogy and Paragenesis

Broadly similar U(-V) deposits are hosted by Permian to Jurassic sandstones in the Paradox Basin of the Colorado Plateau. Common features of all the Paradox Basin deposits include occurrence in bleached red bed sandstones; accessory barite and/or celestine; authigenic Ti minerals; lack of correlation between mineralization and plant coal distribution; and evidence for or actual traces of hydrocarbons in the rock before and/or during mineralization. All but the structure-hosted Cutler deposits also show a mix of hematite, pyrite, and hypogene U and/or V minerals enclosed under authigenic overgrowths surrounding detrital quartz cores, which are extensively replaced by fringes of vanadian phyllosilicates. In the Entrada-hosted deposits, all but traces of hypogene U and V oxides have been removed to leave mainly the V-phyllosilicate minerals, but otherwise they resemble the mineralogy and paragenesis in the rest of the Paradox Basin U-V deposits. This paper presents and compares the deposit types to each other and to global sandstone-hosted U resources. Deposits hosted in the Jurassic Salt Wash Member of the Morrison Formation mostly form tabular, V-dominated bodies in permeable, trough cross-bedded horizons of bleached former red beds. Common quartz overgrowths entrap pyrite, pitchblende, and montroseite. Pitchblende and montroseite also form interstitial masses in cementing V-phyllosilicates, which corrode and partially replace the quartz overgrowths. Common accessory phases include pyrite (some framboidal), chalcopyrite, ferroselite, clausthalite, galena, sphalerite, and barite, with minor asphalt globules that corrode quartz overgrowths and cores and contain pitchblende and pyrite. Down the stratigraphic section, the Jurassic Entrada hosts minor lenticular deposits in aeolian sandstones just below a capping limestone. Ore minerals consist mainly of roscoelite replacing quartz overgrowths and cementing the sandstone. Except for small vanadiferous pitchblende inclusions trapped under quartz overgrowths, minor U-vanadates are the only U minerals observed. Continuing down-section, U-V deposits in the Triassic Chinle occur in conglomerates and sandstones just above the Chinle-Cutler unconformity in the Big Indian district, and in the basal Chinle in White Canyon. Quartz overgrowths are rarer but also enclose inclusions of hematite and pitchblende, more rarely V minerals. Pitchblende, montroseite, and V-phyllosilicates are the main ore minerals, forming intersti