An overview of ore genesis in the Singhbhum Craton, Eastern India

Abstract

The Singhbhum Craton (SC) of Eastern India comprises large economic grade reserves of Fe, Mn, Cr, PGE, Ti, Au, U, Cu, P, REE and W ores along the peripheral part of central granitic pluton. The ore mineralization is primarily associated with the orthomagmatic and volcano-sedimentary rock sequences of three mid-Archean greenstone terrains e.g. Tomka-Daitari-Nuasahi (3.5-3.1 Ga) in the south, Jamda-Koira-Jojohatu (3.3-3.1 Ga) in the west, and Gorumahisani-Badampahar (3.5-3.1 Ga) in the east, and a Proterozoic mobile belt e.g. North Singhbhum Fold Belt (NSFB; 2.2-1.6 Ga) containing the Singhbhum Shear Zone (SSZ; 2.0-1.0 Ga) and South Purulia Shear Zone (SPSZ; 1.0 Ga). All of the three greenstone terrains contain banded iron formation (BIF) hosted Fe ores, whereas phyllite hosted sedimentary Mn ores occur only in the western greenstone terrain. The magmatic Fe-Ti oxide ores occur within gabbro-anorthosite of the southern and eastern greenstone terrains. Chromitite occurs within dunite-orthopyroxenite of the southern and western greenstone terrains, whereas significant PGE mineralization occurs only within gabbro and Fe-Ti oxide ore bands of the southern greenstone terrain. The eastern greenstone terrain comprises chert-phyllite-chlorite schist hosted significant Au mineralization. The NSFB comprises major deposits of Cu, U, P and REE ores within the SSZ, and Au and W deposits within the Chaibasa-Dalma-Chandil volcano-sedimentary sequences including the SPSZ. Such diverse nature of ore mineralization almost throughout the Precambrian Eon as a whole offers vital information pertinent to the complex inner and surficial dynamics of the early Earth. This paper reviews and compiles genesis of the individual ore deposits to convey its comprehensive implications to a better understanding of the evolutionary history of the SC. Broadly, primary ore mineralization in the SC occurred in three episodes. (i) During 3.5-3.25 Ga, authigenic Fe-, Mn- and Au- rich sediments started to deposit in marine greenstone basins within the SC, accompanied by intermittent ultramafic-mafic volcanism, hydrothermalism and clastic sedimentation. The plutonic counterparts of the greenstone volcanic rocks e.g. associated layered igneous complexes hosted orthomagmatic chromite, PGE and Fe-Ti ores. The mineralization ceased by 3.1 Ga along with the closure of greenstone basins due to subsidence and mantle overturn. The greenstone belts were folded and metamorphosed along with granitic activities, and further altered by hydrothermal and supergene processes which formed/enriched the present ore bodies. (ii) The volcano-sedimentary rocks of NSFB containing sporadic Au mineralization started to deposit around 2.2 Ga within an intracontinental basin of NSFB block followed by a crustal doming, formation of back-arc and plume activity. The IOCG type hydrothermal U-Cu-P-REE mineralization occurred during 2.0-1.8 Ga along the SSZ that formed between the subducting Singhbhum- and overriding NSFB- blocks. Primary ore deposition ended along with the closure of the basins due to crustal amalgamation between the Singhbhum- and NSFB- blocks around 1.6 Ga. Deformation, metamorphism and hydrothermal activity (1.6Ga) redistributed and concentrated the U, Cu, P, REE and Au ores. (iii) The formation of SPSZ in between NSFB and Chotanagpur block during 1.0Ga accompanied major W mineralization as well as remobilization and concentration of the U, Cu, P, REE and Au ores.