Record of post-collisional A-type magmatism in the Alwar complex, northern Aravalli orogen, NW India

Abstract

The Alwar complex is situated in the northern part of the Aravalli orogen, NW India and contains A-type granites of late Palaeoproterozoic age. The current study focusses on the Harsora and Dadikar plutons to characterize and constrain the tectonic setting of Palaeoproterozoic felsic A-type magmatism in this crustal segment using whole-rock geochemical data. The rocks studied are metaluminous to slightly peraluminous A-type ferroan granites. The granites are generally characterized by strongly fractionated LREE patterns with nearly flat HREE profiles and show moderate to strong negative Eu anomalies, in addition to prominent negative anomalies in Ba, Nb, Sr, P and Ti. The results show the post-collisional setting of A-type granites in the northern Aravalli orogen and signify that A-type granites may not only form in anorogenic setting. This study provides a new dimension to the understanding of palaeoproterozoic geodynamic evolution in the Aravalli orogen.