Precambrian mafic dyke swarms from the central Indian Bastar craton: Temporal evolution of the subcontinental mantle

The Archaean Bastar craton of central India comprises three different mafic dyke swarms of Precambrian age. Two sets of mafic dyke swarms are subalkaline tholeiitic in nature, whereas the third dyke swarm is high-Si, low-Ti and high-Mg in nature and documented as boninite-norite mafic rocks. The two sets of subalkaline mafic dykes were emplaced during the Mesoarchaean (BD1 swarm) and Paleoproterozoic (similar to 1.9 Ga; BD2 swarm), respectively, whereas boninite-norite (BN) dyke swarm is emplaced in Neoarchaean. BD1 dykes are low Ti + Fe + HFSE and high-Mg olivine to quartz normative rocks, whereas BD2 dykes are predominantly quartz normative with relatively high Ti + Fe + HFSE and low-Mg contents. These distinguished geochemical characteristics, and compatible-incompatible trace element modelling suggest that the Mesoarchaean BD1 dykes were derived from similar to 15-20% batch melting of a depleted lherzolite mantle source; in contrast, the Paleoproterozoic BD2 dykes were derived from similar to 7-10% batch melting of a metasomatized enriched mantle source. The BN dykes are product of different pulses of high-Mg boninitic magma that was produced by similar to 20% melting of a refractory mantle source. Voluminous extraction of basaltic material during the Archaean (BD1 phase) was probably the main cause for producing refractory lithosphere at the end of Archaean (responsible for BN phase) and later, during the Paleoproterozoic, an enriched of metasomatized mantle lithosphere was formed (responsible for BD2 phase); this exemplifies temporal evolution of the subcontinental mantle of the central Indian Bastar craton.