Geochronology and petrogenesis of the TTG gneisses and granitoids from the Central Bundelkhand granite-greenstone terrane, Bundelkhand Craton, India: Implications for Archean crustal evolution and cratonization

In this contribution we present field relations, U-Pb zircon geochronology, in-situ Lu-Hf isotopes, bulk-rock SmNd isotopes and geochemistry of the tonalite-trondhjemite-granodiorite (TTG) gneiss, sanukitoid and anatectic granites from the Central Bundelkhand granite-greenstone terrane (CBGGT). The present study provides a comprehensive insight into the crust-mantle evolution, reworking, and cratonization of the Bundelkhand Craton (BC) during the Archean Eon. We report two discrete episodes of Neoarchean TTG magmatism at similar to 2.71 and similar to 2.68 Ga from the BC for the first time. Additionally, we identify a TTG gneiss that is significantly older (similar to 3.34 Ga) than thus far assumed in the eastern part of the area. Furthermore, zircon U-Pb ages of the sanukitoids and the anatectic granites suggest synchronous emplacement at 2.58-2.50 Ga. Zircon of Paleoarchean TTG, Neoarchean TTG, sanukitoid, and anatectic granites show epsilon Hf-(t) values in the following ranges: +1.7 to 0.9, +4.1 to -10.7, -3.6 to -6.2, and -5.9 to -7.8, respectively, which are indicative of significant crustal reworking. Neoarchean TTG gneiss shows epsilon Nd-(t) and epsilon Hf-(t) value of + 4.5 and + 10.0 to -6.8, respectively, indicating a juvenile crustal source and probably formed by the partial melting of deep-seated mafic crust in the garnet stability field. Neoarchean TTGs formed in arc creation/collision to the Paleoarchean nucleus of the BC. The amalgamation of diverse micro-blocks occurred by the arc-continent collision and probable breakoff of the descending slab between crustal blocks of the BC during Neoarchean. This event generated anatectic granites by intense partial melting of the existing crust, which resulted as closing of subduction and marked as final stabilization and cratonization of the BC. This event also shows evidence that the BC did not amalgamate until similar to 2.50 Ga.

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This study provides comprehensive insights into the crust-mantle evolution, reworking, and cratonization of the Bundelkhand Craton during the Archean Eon, reporting new findings such as two discrete episodes of Neoarchean TTG magmatism and an older TTG gneiss than previously thought. The research also suggests that the Bundelkhand Craton did not fully amalgamate until around 2.50 Ga.