The detection of potassic alteration by gamma-ray spectrometry—Recognition of alteration related to mineralization

Abstract

Abstract Canadian case histories document the use of airborne and ground gamma-ray spectrometry to detect and map potassium alteration associated with different styles of mineralization. These include: volcanic-hosted massive sulfides (Cu-Pb-Zn), Pilley's Island, Newfoundland; polymetallic, magmatic-hydrothermal deposits (Au-Co-Cu-Bi-W-As), Lou Lake, Northwest Territories; and porphyry Cu-Au-(Mo) deposits at Mt. Milligan, British Columbia and Casino, Yukon Territory. Mineralization in two of these areas was discovered using airborne gamma-ray spectrometry. In each case history, alteration produces potassium anomalies that can be distinguished from normal lithologic potassium variations by characteristic lows in eTh/K ratios. Interpretations incorporating airborne and ground spectrometry, surficial and bedrock geochemistry and petrology show that gamma-ray spectrometric patterns provide powerful guides to mineralization. This information complements magnetic, electromagnetic, geological, and conventional geochemical data commonly gathered during mineral exploration programs.