Articles written in Journal of Earth System Science
Volume 127 Issue 3 April 2018 Article ID 0043
Several volumetrically minor ~2.8 Ga anorogenic granites and rhyolites occur along the marginal part of the Singhbhum craton whose origin and role in crustal evolution are poorly constrained. This contribution presents petrographic, geochemical, zircon U–Pb and trace element, and mineral chemical data on such granites exposed in the Pala Lahara area to understand their petrogenesis and tectonic setting. The Pala Lahara granites are calc-alkaline, high-silica rocks and define a zircon U–Pb age of 2.79 Ga. These granites are ferroan, weakly metaluminous, depleted in Al, Ca and Mg and rich in LILE and HFSE. They are classified as A2-type granites with high Y/Nb ratios. Geochemical characteristics (high SiO₂ and K₂O, very low MgO, Mg#, Cr, Ni and V, negative Eu anomaly, flat HREE and low Sr/Y) and comparison with melts reported by published experimental studies suggest an origin through high-temperature, shallow crustal melting of tonalitic/granodioritic source similar to the ~3.3 Ga Singhbhum Granite. Intrusion of the Pala Lahara granites was coeval with prominent mafic magmatism in the Singhbhum craton (e.g., the Dhanjori mafic volcanic rocks and NNE–SSW trending mafic dyke swarm). It is suggested that the ~2.8 Ga A-type granites in the Singhbhum craton mark a significant crustal reworking event attendant to mantle-derived mafic magmatism in an extensional tectonic setting.
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