Aerial radiometric and magnetic reconnaissance survey of portions of Arizona, Idaho, Montana, New Mexico, South Dakota and Washinton. Volume 1. Instrumentation and methods. Final report

Instrumentation and methods described were used for a Department of Energy (DOE) sponsored high-sensitivity, aerial gamma-ray spectrometer and magnetometer survey of the Butte, Choteau, Cut Bank, Great Falls, Havre, Lewistown, Shelby (Montana); Pocatello, Twin Falls (Idaho); Ritzville (Washington); Hot Springs (South Dakota); and St. Johns (Arizona-New Mexico) NTMS, 1:250,000-scale quadrangles. The survey was carried out by Texas Instruments Incorporated under Bendix Field Engineering Corporation Sub-contract No. 78-184-L. The objective of the work was to define areas showing surface indications of a generally higher uranium content where detailed exploration for uranium would most likely be successful. A Sikorsky S-58T helicopter equipped with a high-sensitivity gamma-ray spectrometer and ancillary geophysical and electronic equipment was employed for areas having the ruggedest terrain, including all of Butte and Choteau Quadrangles. A DC-3 aircraft carrying a more sensitive gamma-ray spectrometer system was used in regions of flatter terrain, including all of Shelby and Lewistown Quadrangles. The systems were calibrated using DOE calibration facilities at Grand Junction, Colorado, and Lake Mead, Arizona. Gamma-ray spectometric data were processed to correct for variations in atmospheric, flight, and instrument conditions and were statistically evaluated to remove the effects of surface geologic variations. The resulting first-priority uranium anomalies (showing simultaneously valid eU, eU/eTh, and eU/K anomalies) were interpreted to evaluate their origin and significance. Results of the interpretation in the form of a preferred anomaly map, along with significance-factor profile maps, stacked profiles, histograms, and descriptions of the geology and known uranium occurrences are presented in the individual quadrangle volumes of this final report