Origin and Evolution of Crust Along the South-Eastern Margin of Bastar Craton, Central India

Ghosal, Samyayan (2026) Origin and Evolution of Crust Along the South-Eastern Margin of Bastar Craton, Central India. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Samyayan Ghosal (19RS039)) 19RS039.pdf - Submitted Version Restricted to Repository staff only Download (10MB)

Abstract

A major portion of continental crust was created by the end of Archean. However, the actual mechanism of Archaean crustal growth is a highly debated issue and remains a major research interest globally. For instance, whether the continental growth was uniform or episodic, what were the mechanisms of crustal differentiation and nature of crust-mantle interactions, what was the geodynamic regime–whether there was modern style of plate tectonics—all these remains major problems in Archean crustal evolutionary studies till date. To address these broad research problems, the present study was carried out on the well-exposed rocks along the southeastern margin of the Bastar Craton encompassing field investigation, petrographic analysis, whole-rock geochemistry, and zircon U-Pb and Lu-Hf isotopic analysis. The area records ~2.86 Ga crust generation in the form of a high-HREE sodic granitoid, produced due to shallow partial melting of a juvenile mafic crust in an intraplate setting. Thereafter, the area preserves crust generation signature from ~2.75–2.65 Ga with initiation of crustal reworking at ~2.70 Ga, documented by the detrital zircons of a paragneiss. Later, during ~2.48–2.47 Ga, the area witnessed voluminous continental growth in a post collisional extensional setting, mainly in the form of potassic ferroan granitoids with A-type granite characteristics, accompanied by subordinate low silica ferro-potassic granitoid. The potassic ferroan granitoids were formed due to high temperature reworking of Eo-Paleoarchean crust, whereas the low silica ferro-potassic granitoid was formed due to partial melting of shallow sub-continental lithospheric mantle metasomatized by melts from recycled Eo-Paleoarchean crust and slab-derived fluids. Subsequently, granitoid exhumation supplied immature clastic sediments in the nearby basins likely produced by extensional collapse, whose metamorphic product was preserved in the form of a paragneiss in the area. The findings suggest a changing continental crust generation pattern during late Mesoarchean to early Paleoproterozoic—late Mesoarchean to early Neoarchean period of juvenile magmatism associated with non-plate tectonic regime, followed by the advent of modern-style plate tectonics and granitoid diversification during Archean-Proterozoic transition. Comparison with globally renowned cratons manifested asynchronous similar continental growth pattern.

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