A 1.88 Ga giant radiating mafic dyke swarm across southern India and Western Australia

Abstract

Baddeleyite from a mafic dyke near Bhanupratappur of the central Bastar Craton (India) yielded a weighted-mean 207Pb/206Pb age of 1882.4 ± 1.5 Ma. The dykes are tholeiitic and have variable Mg# (41–60), TiO2 (0.83–1.74 wt%) and low CaO (<10.9 wt%) indicating they are not representative of primary melts and differentiated prior to or during emplacement. Petrological modeling shows that the chemical variability of the dykes is primarily due to crystal fractionation and crustal contamination. The Sr and Nd isotopes (87Sr/86Sri = 0.7032–0.7068; εNd(t) = −1.1 to +1.7) are variable but broadly chondritic. Trace element modeling suggests the dykes were likely derived by partial melting of a mantle source from the spinel-garnet transition zone. The dykes from the central Bastar Craton have the same age and are chemically similar to NW trending dykes and sills from the southern Bastar Craton (1883.0 ± 1.4 Ma; 1883.5 ± 4.4 Ma; 1885.4 ± 3.1 Ma) and dykes from the Yilgarn Craton (1888 ± 9) of Western Australia. The similar age, complimentary orientations and geochemistry of the dykes from the Bastar and Yilgarn Cratons supports the notion that Southern India and Western Australia were once connected during the Paleoproterozoic and separated by ∼1.88 Ga.