2012-10-01_REVISION - M1977305 (16)

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Table 1: Summary of Selected Properties of Solid Phase Layered Silicates (After Bohn et al., 1979) Component Kaolinite Montmorillonite Mineral Type (silicate layers) 11 2:1 Cation Exchange Capacity 1 -10 me/ 100g 80 -120 me/ 100g The Salt Wash Member of the Morrison Formation is the mineralized zone where uranium and vanadium ores are found. The unit is comprised of interbedded sandstones, shales and mudstones. The sandstone units, particularly the upper sandstone, are mineralized. These sandstones tend to be fine grain and well cemented. Underlying the Morrison Formation is the Summerville Formation that consists of shales and mudstones and is usually considered an aquitard in the area. The Entrada/Carmel Formations undivided (mapped as the same unit) underlie the Summerville aquitard and provide the first possible aquifers in the area. While the Carmel contains mudstone layers, the Entrada Formations consist dominantly of fine -grain aeolian sandstones. Underlying the Entrada/Carmel Formation is the Navajo Sandstone. According to Cater et al. (1955), the eastern edge of the Navajo Sandstone follows an irregular course through the western -most part of Colorado and in the Uravan quadrangle is part of a large discontinuous lens that only reaches a maximum thickness of 40 feet in this area. The siliceous cemented Kayenta Formation, commonly a resistant bench - forming unit, consists of sandstones, mudstones and conglomerates that overlie the massive Wingate Sandstone. The cliff forming Wingate consists of fine grain, well -sorted sand, and is an important source of low to moderate quantities of groundwater. Red shales and mudstones of the Chinle Formation complete the geologic section in the immediate area of the mine. 8.2 Mineralization The name "Uravan Mineral Belt" is applied to a narrow, elongated area in southwestern Colorado in which carnotite deposits in the Morrison formation have a closer spacing, larger size, and higher grade than those in adjoining areas. The belt extends from Gateway through Uravan to Slick Rock. The deposits within the belt tend to be clustered in patches (Fischer and Hilpert, 1952). Cater et al. (1955) state that the most common ore minerals found in the region are carnotite and micaceous vanadium minerals. The ore consists mostly of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals, and is also associated with thin mudstone partings, beds of mudstone pebbles, and carbonized fossil plant material. In general, the ore minerals were deposited in irregular layers that roughly follow the sandstone beds. In most deposits, the highest grade concentrations of ore minerals occur in sharply bounded structures called "rolls." Precipitation likely resulted from slight changes in the chemical composition of the solutions, perhaps in the environment of decaying organic material (Fischer and Hilpert, 1952). O'Connor Design Group Inc. U - 9