Crustal evolution of the Southern Granulite Terrane, south India: New geochronological and geochemical data for felsic orthogneisses and granites

This article presents LA-ICPMS U-Pb zircon and U-Th-Pb monazite ages and geochemical data for felsic orthogneisses and granites from the Southern Granulite Terrane of India, a key area for reconstructing the evolution of the late-Neoproterozoic Gondwana supercontinent. The data identify two distinct crustal domains in the Madurai Province, the major part of the Southern Granulite Terrane, and we present a new geotectonic model for their crustal evolution. The Western Madurai Domain is widely composed of late-Neoarchaean (2.53-2.46 Ga) subduction-related, magnesian charno-enderbites, which were reworked in the early-Palaeoproterozoic (2.47-2.43 Ga) during granulite fades metamorphism and partial melting. The Eastern Madurai Domain is dominated by a vast supracrustal sequence, which was deposited on a late-Palaeoproterozoic (1.74-1.62 Ga) basement of magnesian charnockites and Hbl-Bt gneisses that formed through reworking of underlying Archaean rocks. Both domains of the Madurai Province were intruded by voluminous mid-Neoproterozoic A-type charnockites and felsic orthogneisses (0.83-0.79 Ga), which formed through reworking of Archaean to Palaeoproterozoic rocks, together with minor leuco-gabbros and rhyolites, during a major phase of extensional rifting. Regional mid-Neoproterozoic (0.82-0.78 Ga) metamorphism is temporally and spatially related to A-type granite magmatism. Convergence of the two domains in the late-Neoproterozoic (ca. 0.55 Ga) culminated in their collision along a SSW-NNE-trending belt of ultrahigh-temperature metamorphic rocks, the Kambam UHT Belt, and was associated by the localized emplacement of leucogranites (0.56 Ga). Accretion of the Madurai Province at the Archaean Dharwar Craton occurred in the earliest Palaeoproterozoic along the Moyar-Bhavani-Cauvery Suture, a distinct crustal domain characterized by late-Neoarchaean (2.50 Ga) subduction-related, magnesian enderbites. They resemble the age and composition of the Western Madurai Domain charno-enderbites and intrude Mesoarchaean charnockites (2.85 Ga) and metabasites, representing remnants of oceanic crust. The suture zone was, coeval with the Western Madurai Domain, affected by early-Palaeoproterozoic (2.49-2.45 Ga) HP granulite facies metamorphism. Just as the Madurai Province the suture zone was intruded by ferroan mid-Neoproterozoic (0.84 Ga) metagranitoids but was only locally affected by an early-Cambrian overprint (0.54 Ga). The inferred early-Palaeoproterozoic accretion of the Madurai Province at the Dharwar Craton and the extension-related origin of the voluminous mid-Neoproterozoic A-type charnockites are difficult to match with the recently established concept of a Neoproterozoic subduction zone and suture between the craton and the Madurai Province. In a Palaeogeographic model the widely Neoarchaean Western Madurai Domain is correlated with the Antananarivo Domain of central Madagascar, whereas the Proterozoic Eastern Madurai Domain is linked with the Ongole Domain, the southernmost segment of the Eastern Ghats Belt, and the Wanni Complex of Sri Lanka. (C) 2014 Elsevier B.V. All rights reserved.