Metamorphic Evolution of the Amphibolites from Bundelkhand Craton, Central India: P-T Constraints and Phase Equilibrium Modelling

Abstract

The amphibolites from the Mauranipur and Babina regions are located in the central part of the Bundelkhand Craton (BuC), northern India. During the geodynamic evolution of the BuC, these amphibolites underwent medium-grade metamorphism. This study combines textural observations of amphibolites from two distinct regions (Mauranipur and Babina) with mineral chemistry and phase equilibrium modelling. Observations suggest that the amphibolites of both areas have gone through three stages of metamorphism. The pre-peak stage in the amphibolites from the Mauranipur and Babina regions is marked by the assemblages Ep-AmpCpx-Pl-Ilm-Ru-Qz and Ep-Amp-Cpx-Pl-Ab-Ilm-Qz respectively; the peak metamorphic stage is characterized by the mineral assemblages Amp-CpxPl-Ilm-Ru-Qz and Amp-Cpx-Pl-Ilm-Qz-H2O, which is formed during the burial process, and the post-peak stage is represented by the assemblages Amp-Pl-Ilm-Ru-Qz and Amp-Pl-Ilm-Qz-H2O respectively, which is formed by exhumation event. By applying the phase equilibria modelling in the NCFMASHTO system, the P-T conditions estimated from pre-peak, peak to post-peak stages are characterized as 6.7 kbar/510 ℃, 7.3 kbar/578 ºC and > 3.0 kbar/>585 ºC, respectively, for the Mauranipur amphibolites; and 6.27 kbar/520 ºC, 5.2 kbar/805 ºC and > 3.0 kbar/>640 ºC respectively for Babina amphibolites. The textural association and P-T conditions of both amphibolites suggest that these rocks were affected by burial metamorphism followed by an exhumation process during subduction tectonism in the BuC.