Origin and evolution of granitoids associated with the Kadiri greenstone belt, eastern Dharwar craton: A history of orogenic to anorogenic magmatism

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Different tectonic models have been proposed to explain the Neoarchaean evolution of the eastern Dharwar craton (EDC). Here we present whole-rock elemental and Nd isotopic compositions coupled with zircon U–Pb age and trace elemental data on granitoids associated with the Neoarchaean Kadiri greenstone belt, EDC to track the tectonic evolutionary history of the terrain. Earlier works on volcanic rocks of the Kadiri belt (tholeiitic oceanic plateau basalt, high Mg# andesite and potassic adakite) envisaged continental margin arc–oceanic plateau collision. In this work the oldest recognized granitoid is a 2.56Ga syntectonic, sanukitoid-like hornblende granodiorite enriched in large-ion lithophile as well as ferromagnesian elements. It was probably derived from a metasomatized mantle wedge above a subduction zone. This is followed by syntectonic emplacement of 2.54Ga transitional TTGs and potassic adakitic volcanic rocks. Intrusion of 2.51–2.52Ga crustally derived granites (mostly K-rich; ɛNd=+0.9 to −3.7) marks the end of orogenesis in the area. A convergent orogenic setting characterized by assembly of diverse terranes, repeated slab-break-off and crustal reworking is proposed to interpret the association of various granitoids and volcanic rocks. Finally, intrusion of crustally derived, highly silicic, K-rich A-type granite (ɛNd=−0.6 to −4.8) and mantle-derived syenite occurred in a post-subduction, non-compressive environment during Palaeoproterozoic. Lithospheric delamination and attendant mantle melting and crustal reworking are suggested as possible mechanism for generation of these rocks. The negative ɛNd values and Mesoarchaean Nd depleted mantle model ages of some Neoarchaean to Palaeoproterozoic Kadiri granitoids attest to the presence of older crust in the eastern part of the EDC. The final cratonization of the EDC (2.52–2.50Ga) occurred later than in most of the other cratons.