Aerial radiometric and magnetic reconnaissance survey of portions of Arizona, Idaho, Montana, New Mexico, South Dakota and Washington. Volume 2-D Choteau Quadrangle. Final report

The results of a high-sensitivity, aerial, gamma-ray spectrometer and magnetometer survey of the Choteau Quadrangle, Montana, are presented. Instrumentation and methods are described in Volume 1 of this final report. This work was done by Texas Instruments Incorporated under Bendix Field Engineering Corporation Subcontract No. 78-184-L as part of the US Department of Energy National Uranium Resource Evaluation (NURE) Program. Statistical and geological analysis of the radiometric data revealed 41 uranium anomalies worthy of field-checking as possible prospects. Twenty anomalies may be caused by uranium mineralization in Precambrian quartzites, argillites, and limestones. One anomaly in particular is very strong and extends about a half mile over three geologic units. One anomaly occurring over Cambrian rocks may reflect the presence of a deposit similar to the Blind River and Rand deposits; however, it is just as likely that it is related to a shale sequence in predominantly limestone rocks. Six anomalies associated with highly faulted Paleozoic rocks along the eastern boundary of the Rocky Mountains may contain uranium mineralization in limestones, dolomites, or sandstones. Sandstone-type uranium deposits may be indicated by 10 preferred anomalies in Cretaceous sedimentary rocks in the Great Plains physiographic province on the eastern side of the quadrangle. Many anomalies in Quaternary units may reflect the existence of uranium-rich source rocks that may host uranium prospects