Association of A‐ and I‐type granitoids in the central Aravalli orogen, Rajasthan: Implications for the Neoproterozoic tectonic evolution of north‐west India

We present new mineralogical and geochemical data for the granitoid plutons of the Neoproterozoic Sendra Granitoid Suite, central Aravalli orogen, north-west India to constrain their petrogenesis and tectonic setting. The granitoids can be classified into two groups: (a) A-type Chang, Chitar, Borwar, and Seliberi plutons and (b) I-type Jaitpura pluton. The available geochronological data (zircon U–Pb ages) suggest that all the granitoids are coeval at 990–970 Ma. The granitoids are mostly granite sensu stricto, with subordinate granodiorite and rare tonalite. The rocks are metaluminous to mildly peraluminous and have high total REE abundances. Nevertheless, there are also certain geochemical differences between A-type and I-type granitoids. The I-type granitoids have relatively high Al2O3 and CaO concentrations and show significant fractionation with increasing SiO2. The least fractionated sample contains low abundances of the HFSE and has low Fe-number and Ga/Al ratios. In contrast, the A-type granitoids have lower CaO and higher HFSE concentrations, Fe-number, and Ga/Al ratios. Both A-type and I-type granitoids show negative Ba, Sr, Nb, P, Ti, and Eu anomalies, and are characterized by high zircon-saturation temperatures (801–977°C). The present data suggest that rocks of the Sendra Granitoid Suite were generated predominantly by partial melting of mafic sources at high temperatures and emplaced in a post-collisional extensional regime. Moreover, our study provides evidence of the preserved post-collisional extensional magmatism subsequent to the subduction during the assembly of the Rodinia supercontinent, which is otherwise relatively less prevalent over intra-plate or within-plate magmatism during this time period.