Petrogenesis and Metallogenic Evolution of Leucogranites from the Paleoproterozoic Malanjkhand Granitoids, Central India

Abstract

The Birsa and Devgaon leucogranites represent contemporaneous episodes of highly fractionated felsic magmatism associated with the Paleoproterozoic Malanjkhand granitoids in the Bastar craton, Central India. Major element oxides geochemistry reveals that two leucogranites are strictly granite in composition and both show calc-alkaline affinity. Geochemical discrimination diagrams inferred that these leucogranites shows affinity towards I-type magma with metaluminous characters. Geochemical classification inferred that the Birsa leucogranite preferred to be magnesian whereas Devgaon leucogranite designated to be ferroan type. Geothermobarometry estimation suggested that 1.2-4.5 kbar pressure and 750o-830oC temperature conditions at the shallow depth of the continental crust is responsible for the emplacement of leucogranites. Crystallization evolution of feldspar in the leucogranite provided evidences of late stage felsic magmatism in the Malanjkhand pluton. Molybdenum enrichment in the leucogranite possibly due to crystal fractionation under high oxygen fugacity conditions inherited from the magma chamber in the continental crust. Anomalous high concentration of Mo in the Devgaon leucogranite is contributed from episodic hydrothermal system with poor supply of sulphur. Occurrences of molybdenite in the Devgaon leucogranite provides high exploration potential to investigates granite molybdenite system in the Bastar craton.