Abstract

Several significant uranium discoveries have been made since 1953 along the front range of Colorado. Uranium ore has been found both in Precambrian rocks and sedimentary rocks. The Precambrian rocks consist of metasediments and intrusive batholithic granites. The sediments range from Pennsylvanian to Tertiary in age. Uranium ore is found in the upper (Muddy) sandstone member of the Dakota formation in close association with asphalt, pyrite, and ilsmenite (molybdenum oxide) and is controlled by a west dipping strike-slip fault. The ore body occupies a position adjacent to and in the footwall side of the fault, and traces of uranium are found on the hanging wall side. Uranium is also found in the lower sandy portion of the Dakota shale.The uraninite is believed to be a primary ore of hydrothermal origin. It is further suggested that uranium-bearing hydrothermal solutions originated in the Precambrian complex and migrated eastward along the Golden thrust fault. The Golden thrust fault, which underlies the area, therefore served as a conduit for the solutions. The solutions then migrated into minor shear zones that intersect the main Golden thrust fault, and where these minor faults traversed permeable sandstone, the solutions impregnated the sandstone. Uranium was then precipitated from the hydrothermal solutions when favorable conditions for deposition, such as asphaltum, were encountered.

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