U-Pb ID-TIMS baddeleyite age and geochemistry of the newly identified ca. 1.94 Ga magmatic event in the Central-Western Bastar craton

Abstract

A NNW-trending mafic dyke from the central-western Bastar craton yields a UPb ID-TIMS baddeleyite age of 1944 ± 6 Ma. By correlating additional dykes with similar trend and geochemical characteristics, we identify a previously unrecognized dyke swarm, named herein the Pakhanjore swarm. Geochemical evidence suggests that the studied rocks are derived from partial melting of a spinel-rich, shallow lithospheric mantle source, involving 5–15 % partial melting as indicated by the non-modal batch melting model. AFC (Assimilation and fractional crystallization) modelling further reveals that fractional crystallization with moderate crustal assimilation (r = 0.3) contributes to the overall magmatic evolution. The similarity in trend of the ca. 1.94 Ga Pakhanjore swarm with the 1.89–1.88 Ga Bastanar swarm, and the ca. 1.85 Ga Sonakhan swarm of the Bastar craton suggests their emplacement occurred within a shared tectonic regime and/or paleostress field. Although notable geochemical similarities exist between the ca. 1.94 Ga Pakhanjore swarm and the 1.89–1.88 Ga and ca. 1.85 Ga mafic dykes, a direct genetic linkage remains inconclusive. However, based on available geological, geochronological, and geochemical data, the 1.89–1.88 Ga and ca. 1.85 Ga swarms appear to be part of a shared LIP event, whereas the ca. 1.94 Ga event likely represents an independent magmatic episode. The spatial alignment of all three dyke swarms with the NNW-trending Pranhita-Godavari Basin suggests a potential tectonic connection.