Dissecting through the metallogenic potentials of Precambrian granitoids: case studies from the Bastar and Eastern Dharwar Cratons, India

Abstract

AbstractThe Malanjkhand granodiorite in the Bastar Craton hosts a major copper (+ molybdenum) deposit. It represents a Precambrian granite–ore system lacking in key morphological features of porphyry-type deposits but is comparable as a chemical package with a distinct mode of evolution of the magmatic-hydrothermal system. Mineral chemistry of biotite and apatite along with bulk geochemical data constrain critical parameters such as initial water and halogen contents of the magma. Evolution of the magmatic-hydrothermal fluid has been envisaged with available thermobarometric data. A quantitative ore genetic model in terms of efficiency of removal of metals and resultant mineralization in terms of quantity of metals has been attempted for the Malanjkhand deposit. The Eastern Dharwar Craton witnessed prolific granitic activities in multiple phases during the Late Archean and are spatially close to auriferous schist belts. Against a widely held view of a single metamorphogenic origin of metal and ore fluid, a granite–gold connection can be visualized for the auriferous schist belts of the Eastern Dharwar Craton through comparison of fluid characteristics in the granitoid and ore regimes and mineral chemical constraints. Although a quantitative genetic link between the granitoid and gold would need more data, a magmatic component of the ore fluid could be established based on the available information.