Thermal history of a Late Mesoproterozoic paired metamorphic belt(?)during Rodinia assembly:New insight from medium-pressure granulites from the Aravalli-Delhi Mobile Belt,Northwestern India

摘要

In this study, we investigate the possible record of a Late Mesoproterozoic paired metamorphic belt in the Aravalli-Delhi Mobile Belt (ADMB), NW India using a suite of supracrustal and metaigneous gran-ulites from the Pilwa-Chinwali granulite terrain at the north-western margin of the ADMB. Using metamorphic reaction textures,mineral chemistry,metamorphic reaction history,geothermobarometric computations and electron microprobe dating of monazite in 5 samples of pelitic granulite, leptynite gneiss,enderbite and charnockite,we have deduced a medium-pressure granulite facies metamorphism (P between 4.9 and 6.8 kbar, T > 760-815 °C) along a heating-cooling, counterclockwise P-T path be-tween 1.09 and 1.01 Ga.When collated with published metamorphic and chronological constraints and geological settings of the adjoining crustal domains of the ADMB, these findings provide new insights into the developments of two tectonic domains of contrasting thermal gradients at ca.1.0 Ga,consistent with metamorphic transformations in tectonically thickened middle-lower crustal sections during continental collision to continental subduction and in the root zones of spatially adjacent island arc,as part of the Rodinia supercontinent assembly event.