Comparison of geophysical, mineralogical, and stratigraphic attributes in drillholes MAC-218 and RL-88, McArthur River uranium camp, Athabasca Basin, Saskatchewan

Abstract

Multiparameter downhole geophysical measurements in two representative boreholes in the eastern Athabasca Basin are compared to visual, petrographic, mineralogical, and lithogeochemical analyses of their drill cores. Natural gamma-ray spectrometry data exhibit increased levels of radioactivity in the Read and Manitou Falls formations that relate mainly to natural thorium and, to a lesser extent, uranium abundances, whereas potassium responses are generally low. Thorium responses in these quartz-dominated fluvial deposits are closely correlated with detrital grain-size parameters such as the per cent of grains greater than 2 mm and are therefore interpreted to relate to primary heavy mineral accumulations and their diagenetic products (crandallite-group minerals) within coarser grained beds. Diagenetic attributes such as porosity and silicification are positively correlated with density, resistivity, and acoustic velocity. Natural gamma-ray logs are thus guides to stratigraphy, and other geophysical parameters calibrate ore-related alteration features, thereby facilitating integration of geological and geophysical transects.