2.62 Ga high‐temperature metamorphism in the central part of the Eastern Dharwar Craton: implications for late Archaean tectonothermal history

Abstract

Aluminous metasediments occurring in the central part of the Eastern Dharwar Craton (EDC), southern India, develop contrasting mineral assemblages in closely spaced domains. Detailed petrographic, mineral chemical and geothermobarometry showed 'peak' metamorphic conditions of 780-820°C and~5 kbar that resulted in partial melting of biotite-bearing protoliths. Initial bulk compositional heterogeneity and different degrees of melt extraction produced diverse restitic mineral assemblages. P-T pseudosections, constructed from effective bulk composition, and consideration of the sequence of mineral reactions, deduced from textural criteria, define a nearly isobaric heating-cooling P-T trajectory. Monazite in the metasediments has a detrital core age of 3161 ± 78 Ma and a metamorphic age of 2625 ± 26 Ma (EPMA chemical age), which is the first record of a pre-2500 Ma high temperature-low pressure metamorphism event in the EDC. Based on age contemporaneity with the 2.7-2.62 Ga hot juvenile magmas of tonalite-trondhjemite-granodiorite (TTG)-greenstone accretion and the deduced P-T history, we conclude that heat advecting from rising TTG magmas and mafic magmas (greenstones) as a consequence of mantle melting, resulted in a hot transient mid-crust during a major late Archaean tectonothermal event in the Eastern Dharwar Craton. All the phenomena are consistent with a recently proposed model involving an arc setting during ridge subduction and consequent opening of a slab window. This study therefore provides new constraints on the thermal evolution of the Eastern Dharwar Craton.

Geochemical and Nd isotope constraints on petrogenesis of granitoids from NW part of the eastern Dharwar craton: Possible implications for late Archaean crustal accretion

“…10) progressive shifting of magma generation locale (Beakhouse and Davis, 2005;Calvert et al, 2004;Davies and Blanckenburg, 1995;Lobach-Zhuchenko et al, 2008;Whalen et al, 2004b). This scenario of hot juvenile magmatic accretion is also in agreement with the presence of high temperature, low pressure metamorphic assemblages in, and the recent tectonomagmatic interpretation of EDC, envisioning pervasive flow of hot, buoyant, partially molten, soft crust in a convergent set up (Chardon et al, 2011;Jayananda et al, 2011).…”

Origin of iron oxide spherules in the banded iron formation of the Bababudan Group, Dharwar Craton, Southern India

“…1A), which in turn spatially associated with crustal reworking and emplacement of high-potassic Chitradurga and ArsikereBanavara plutons at 2.62 ± 0.02 Ga (Jayananda et al, 2006). Laterally to the east 2.62 Ga granulite facies metamorphic event related to the emplacement of the Chitradurga granite have been documented (Jayananda et al, 2011). The major N-S trending shear zones associated with cooling of crust, controlled lower temperature mesothermal (300 °C -350 °C) gold mineralization during compressional tectonics (Kolb et al, 2004).…”

Archaean granulite facies metamorphism at the Singhbhum Craton–Eastern Ghats Mobile Belt interface: implication for the Ur supercontinent assembly

“…The Chandar and Ektali supracrustals (metapelites) which have been inferred to be the components of the Singhbhum Craton, indicate that prior to ~3.07 Ga, sedimentary processes were operative. Orogenesis is also indicated by recent data in the Dharwar nucleus (Jayananda et al ., ; High T–low P metamorphism at ~2625 Ma) and in Bundlekhand nucleus (Saha et al ., ; High P metamorphism at ~2.78 Ga), thereby indicating that the stabilization of Ur possibly continued up to ~2.6–2.8 Ga.…”