Tectonothermal evolution of the Banded Gneissic Complex in central Rajasthan, NW India: present status and correlation

Abstract

In this study, we make a critical synthesis of the available magmatic, metamorphic and geochronological data, particularly from the Banded Gneissic Complex of central Rajasthan in northwestern India. Based on well-constrained database, we demonstrate that the Precambrian crust of this segment of Peninsular India records a protracted sedimentational, tectono-magmatic and tectono-metamorphic history over a period of >1 Ga from c. 2.2-2.1 Ga to 0.95-0.88 Ga that can be correlated with the accretion and dispersal of two supercontinents, namely Columbia and Rodinia. Following the stability of the Archean craton at ~2.5 Ga, the Aravalli basin opened up by ~2.2-2.1 Ga on a tonalite-trondhjemite-granodiorite-amphibolite basement, and closed at ~1.8-1.9 Ga due to westward subduction of the Aravalli crust during the Aravalli orogeny. This can be correlated with the global accretionary process associated with the formation of Columbia. A-type granite magmatism in the North-Delhi Fold Belt at 1.7 Ga and the formation of medium-pressure granulites, synchronous with mafic and felsic magmatism with or without orthopyroxene at ~1.74-1.72 Ga in the Sandmata Metamorphic Complex (SMC) are related to a switching of tectonic style from subduction to extension or from subduction to a cycle of back-arc extension and back-arc closure. The supracrustal and metaigneous granulites of the SMC and the A-type granites of the North-Delhi Fold Belt acted as basement for the opening up of two Mesoproterozoic sedimentary basins: the Delhi Basin to the west and the Mangalwar Basin to the east. These basins were closed with the onset of a continent-continent collisional orogeny at ~0.95-0.88 Ga (cf. Grenvillian orogeny), producing an extensive, amalgamated crustal domain, involving the inverted Delhi and Mangalwar basins, their reworked basement rocks and the cratonic domains lying to the east and the west of these basins. Crustal amalgamations and stitching of cratons/microcontinents at c. 1.0 Ga in northwestern India are also correlatable with collisional tectonics in other Proterozoic mobile belts of central, eastern and southeastern India, and constitute an important part on the growth and the assembly of the Greater Indian Landmass in Rodinia.