Garnet pyroxenite from Nilgiri Block, southern India: Vestiges of a Neoarchean volcanic arc

摘要: Southern peninsular India preserves records of Late Neoarchean Early Paleoproterozoic continental building and cratonization. A transect from the Paleoarchean Dharwar Craton to arc magmatic complex in Nilgiri Block across intervening Moyar Suture Zone reveals an arc-accretionary composed banded iron formation (BIF), amphibolite, metatuff, garnet-kyanite schist, metagabbro, pyroxenite charnockite. Here we investigate petrology, geochronology petrogenesis garnet-clinopyroxenite. The is mainly orthopyroxene clinopyroxene with local domains/pockets enriched a clinopyroxene-gamet assemblage. Thermobarometric calculations phase equilibria modeling suggest that orthopyroxene-and clinopyroxene-rich domains formed at 900-1000 degrees C, 1-1.2 GPa whereas garnet-and record higher pressure about 1.8-2 similar temperature conditions (900-1000 C). Zircon U-Pb SHRIMP dating show weighted mean Pb-207-Pb-206 age 2532 +/- 22 Ma, metamorphic overgrowth 2520 27 Ma 2478 Ma. We propose tectonic model involving decoupling break-off oceanic plate along southern flanks Craton, which initiated subduction. Slab melting eventually built volcanic on top overriding Craton. Our study supports active regime end Archean Era, aiding growth paleo-continents their assembly into stable cratons. (C) 2018 Elsevier B.V. All rights reserved.