Reconnaissance for radioactive minerals in Washington, Idaho, and western Montana, 1952-1955

Abstract

BS>About 50 occurrenccs of radioactive minerals and nearly 50 properties not abnormally radioactive were examined during geologic reconnaissance for radioactive minerals in Idaho, Washington, and western Montana during the period July 1952 to June l955. The most important uranium deposits are in or near granitic to quantz monzonitie intrusions of probable Cretaceous age in central and northern Idaho, westernmost Montana, and northeastern Washington. These areas are considered to be most favorable for prospecting. Margins of gramitic intrusive bodies in central Montana and western Washington may also be favorable. Uranium-bearing pegmatites associated with granitic intrusive rocks are considered too small and too low grade to be potential sources of uranium. Some placer deposits in southern and central Idaho contain sufficient concentrations of uranium minerals to be of interest as a source of uranium. Known thorite- bearing veins are confined to Precambrian rocks of the Belt series in northern and east-central Idaho and southwestern Montana. Monaziterich layers in metamorphic rocks in east-central Idaho do not seem large enough and continuous enough to permit profitable mining. (auth)