The Detection of Potassic Alteration by Gamma Ray Spectrometry: Recognition of Alterations Related to Mineralization

Case histories developed by the Geological Survey of Canada since 1970 clearly demonstrate the successful application of airborne and ground gamma ray spectrometry to map potassium alteration associated with different styles of mineralization. These include: volcanic hosted massive sulphide (Cu-Pb-Zn) mineralization; polymetallic (Au-Co-Cu-Bi-W-As), magmatic-hydrothermal mineralization; and porphyry (Cu-Au-Ilvlo) mineralization. Alteration associated with mineralization may produce potassium anomalies which can be distinguished from the normal lithologic signature by characteristic eTh/K ratio lows. 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 compliments magnetic, electromagnetic, geological and conventional geochemical data commonly gathered during mineral exploration programs. In addition to applications to mineral exploration, airborne and ground gamma ray spectrometry provides valuable information useful for regional and detailed bedrock and surficial geological mapping and environmental radiation monitoring. Worldwide, increased levels of airborne gamma ray spectrometric surveying will foster increased ground spectrometric surveying and improvements to data processing, interpretation, case history development and presentation. More effective communication of these results will lead to better understanding and acceptance of the currently under-utilized gamma ray spectrometric method.