Abstract

Urano-organic substances form essential constituents of the uranium ore at Temple Mountain, Utah. These occur in the vicinity of highly altered collapse structures associated with carbonaceous and petroliferous materials. Chemically, the ore is similar to low-rank coals. Geological conditions, the uranium distribution, texture, physical properties, and microscopic characteristics are indicative of a petroliferous origin. The ore is considered a uranium analogue corresponding to thucolite, the thorium and rare-earth radioactive mineral. The writers believe that induration resulted from polymerization and oxidation-devolatilization of hydrocarbons, caused by the interaction of ore solutions and organic materials at elevated temperatures. The limits of temperature postulated are a minimum of 100° C. and a maximum possibly as high as 350° C.

A characteristic group of metallic elements is present in the ore, as shown by the X-ray spectrograph. A rough zonal relation exists. Arsenic, cobalt, and selenium are concentrated near the collapse, whereas uranium, zinc, and vanadium appear more abundant in the mining area away from the collapse. Small particles of uraninite and sphalerite are disseminated throughout the ore, but the zonal relation is emphasized by the occurrence of native arsenic near the collapse and by the occurrence of montroseite, the primary vanadium oxide, in the mining area. The distribution of supergene oxidation minerals of vanadium and arsenic is further confirmation.

Ore textures suggest the emplacement of uranium-bearing organic material by the flocculation and subsequent accretion of hydrocarbons immiscible in aqueous ore solutions. Replacement of the sediments took place under the corrosive influence of the ore and pre-ore solutions. Contemporaneously, metallic elements were extracted from the solutions by the organic material. During emplacement and induration, dispersed particles of metallic minerals were formed. Banded nodules of the organic material and associated metallic minerals developed as the intensity, composition, and quantity of the solutions varied through time.

A change in the character of the ore solutions is indicated in the vicinity of the collapse by the presence of large replacement masses of dolomite and siderite above the ore horizon, abundant late hydrothermal jarosite in the Chinle, marcasite below the ore horizon, and the replacement of carbonate at depth. Slightly acidic conditions prevailed at depth, and neutral to slightly alkaline conditions prevailed above the ore horizon. Collapse features provided channels for the migration of organic materials and for the penetration of hydrothermal solutions.

The occurrence of native arsenic, 2M1 mica clay, and large masses of dolomite, and the character of the urano-organic ore indicate heating in excess of the effects ordinarily attributed to ground water. The distribution and character of the alteration, the ore-mineral suite, and the presence of collapse structures suggest an epithermal hot-spring origin for the uranium mineralization. The features at Temple Mountain are significant in the delineation of centers of uranium mineralization elsewhere on the Colorado Plateau.

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