Colorado Plateau deposits

U3Og). The concentration during the period 400-300 M years occurs in marine black shales, while that in the 300 M years to recent period is accounted for by sedimentary-type deposits, an important example being the Colorado Plateau deposits of USA. 

Tabular deposits The Uravan district of southwestern Colorado is the most typical occurrence of tabular deposits, sometimes referred to as Colorado Plateau deposits. In general, the orebodies tend to lie in the lower portion of a reduced channel sandstone. They are roughly concordant to bedding, with horizontal dimensions much greater than the vertical. 

Coffinite was first described as a new mineral by Stieff and co-workers from several localities in the sandstones of the Colorado Plateau deposits often intimately associated with asphaltic material. It was also found in vein-type deposits in Spain by Arribas and has since been found in almost all types of deposits. The composition has been reported as U(SiOi4)i AOrganic matter was always present and organometallic complexes of uranium may have accounted for the excess uranium rather than requiring excess (OH) to account for the U Si ratio deviating from unity. USi04 has been prepared by Fuchs and Gebert with no evidence of OH substitution. 

More than 30 years ago it became apparent that sandstones of the Athabasca Basin in Saskatchewan are host to significant deposits of uranium. Previous work elsewhere, primarily in the Colorado Plateau (Cannon 1964) and the former Soviet Union (Kovalevsky 1972), had shown that plants are capable of accumulating high concentrations of U. Surveys near the eastern margin of the Athabasca Group revealed an area of... 

Two types of deposits, where the internal S-isotope variations fit the expected scheme of bacterial reduction, but where the biogenic nature was already known from other geological observations, are the sandstone-type uranium mineralization in the Colorado Plateau (Warren 1972) and the Kupferschiefer in Central Europe (Marowsky 1969), although thermal sulfate reduction may have occurred at the base of the Kupferschiefer (Bechtel et al. 2001). 

Bromley, M. (1992) Topographic inversion of early interdune deposits, Navajo Sandstone (Lower Jurassic), Colorado Plateau, USA. Sedimentary Geology 80, 1-25. 

We can not immediately conclude that we are seeing evidence for nuclear reactions. This variability was recognized years ago within the A.E.C. and it has been hypothesized that the New Mexico effect is due to chemical exchange in the oxidation-reduction cycles which are largely responsible for the formation of the large sandstone deposits of uranium in the Colorado Plateau. Now... 

Two of the most well-known applications of the sodium carbonate leaching of ores are the extraction of uranium from pitchblende in Canada and extraction of both uranium and vanadium from camotite, which is mined in numerous localities of the Colorado Plateau area of the United States. The latter deposits were originally worked for their vanadium content but since the 1939-45 war the emphasis has been on uranium, with vanadium a subsidiary product. 

Radiogenic helium, radon and radium, each with a different mechanism of migration, should be effective even in completely reduced systems. Examples of these occurrences are tabular Colorado Plateau type deposits related to reducing conditions in a palaeo-river bed and rereduced host rocks where roll fronts are no longer in proximity to surface oxidation. 

Roll-type uranium deposits occur in intracratonic sedimentary basins in the U.S.A. Best known are those in Tertiary strata of Wyoming (Powder River, Shirley and Wind River basins) and the Texas Gulf Coast. Smaller deposits are present in Jurassic rocks of the Colorado Plateau. 

Hansley PL, Spirakis CS (1992) Organic matter diagenesis as the key to a unifying theory for the genesis of tabular uranium-vanadium deposits in the Morrison Formation, Colorado Plateau. Econ Geol 87 352-365... 

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