Journal of Southeast Asian Earth Sciences. Vol. 14, Nos 314, pp. 137-147, 1996 Copyright (0 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved PII: s0743-9547(%)ooo53-0 0743-9547/96 SI 5.00 + 0.00 Geochronologic constraints of granulite terranes of South India and their implications for the Precambrian assembly of Gondwana M. Yoshida,* R. S. Bindu,* H. Kagami,? T. RajeshamJ M. Santosh$ and H. ShirahataT *Department of Geosciences, Osaka City University, Osaka, Japan TInstitute of Earth Interior Research, Okayama University, Misasa, Japan SGeological Survey of India, Southern Region, Hyderabad, India $Centre for Earth Science Studies, Trivandrum, India T[Muroran Institute of Technology, Muroran, Japan zyxwvutsrqponmlkjihgfedcbaZYXWVUT (Receiued 15 January 1996; accepted for publication 10 June 1996) Abstrrc+-Recent geochronologic data allow us to propose a new characterization of Precambrian granulite terranes in Peninsular India. The Archean granulite terranes, including the Godavari Granulite Belt (GGB) along the Godavari Valley and the Nilgiri-Madras Granulite Belt (NMGB) along the southern fringe of the Dharwar Craton and north of the Palghat-Cauvery Shear Zone, are characterized by metamorphic events at ca. 2.8-3.0 Ga and intense granitic activity at ca. 2.5 Ga associated with middle- to high-grade metamorphism. The Proterozoic granulite terranes include the Eastern Ghats Granulite Belt (EGGB) along the Bengal Bay Coast of India, the Periyar-Madurai Granulite Belt (PMGB) south of the Palghat-Cauvery Shear Zone and north of the Achankovil Lineament, and the Trivandrum Granulite Belt (TGB) south of the Achankovil Lineament. The Proterozoic granulite belts are characterized by model Nd ages ( TD~) of mostly ca. 2.0-3.0 Ga with local 1.3-l .8 Ga. Intense deformation and regional high-grade metamorphism predates emplacement of A-type granitic plutons at ca. 550-740 Ma and the last granulite metamorphism took place at ca. 550 Ma. Both GGB and NMGB have similar geochronologic characteristics to the Napier Complex of East Antarctica in that they suffered ca. 2.8-3.0 Ga and ca. 2.5 Ga tectonothermal events. EGGB, PMGB and TGB have similar ranges in Nd TDM ages as the Rayner and the Liitzow-Holm complexes in East Antarctica. They are also similar to the Sri Lankan Precambrian, when the three Precambrian units in Sri Lanka are not differentiated and mixed altogether. In this assembled East Gondwana, late Archean granulite terranes form a continuous belt from NMGB to GGB through the Napier Complex, forming a horseshoe-shaped belt surrounding the Dharwar Craton. The Paleoproterozoic- Mesoproterozoic terranes form a broad belt continuing from EGGB to PMGB through the Rayner and the Liitzow-Holm complexes. This belt forms a major part of the Mesoproterozoic Circum East Antarctic Mobile Belt surrounding East Antarctica, which is important for the assembly of East Gondwana. Within the Proterozoic terrains, signatures in the distribution of TDM ages facilitate the differentiation of the Paleoproterozoic and Mesoproterozoic terranes which have distinct distributional characteristics. Copyright 0 1996 Elsevier Science Ltd Inroduction krishna and Naqvi, 1986). With regard to the southern granulite terranes, differentiation into the northern Geological, structural and petrological studies from Archaean and southern Proterozoic terranes bounded Peninsular India have contributed much to our by the Palghat-Cauvery Shear Zone was stressed by understanding of Precambrian events. However, reliable Grew and Manton (1986) and has been supported by geochronologic data for the interpretation of high-grade several recent works (e.g. Harris et al., 1994). It is metamorphic terranes were insufficient until recently considered necessary to review geochronologic data, (e.g. Geological Survey of India, 1989), and thus including those that have been accumulated recently previous geotectonic division of Peninsular India (e.g. (e.g. Harris et al., 1994; Jayananda et al., 1995; Radhakrishna and Naqvi, 1986) was not fully based on Unnikrishnan-Warrier et al., 1995a, b), and to con- the necessary geochronologic evidence. strain the geotectonic division of Precambrian Penin- There have been different views with regard to the sular India. geotectonic division of the Precambrian of Peninsular The present authors have been studying the assembly India. For example, all of the eastern to southern of East Gondwana, specifically the Precambrian granulite terranes were regarded as one Archaean India-Antarctic sector; thus, the geochronological study terrane (e.g. Narayanaswami, 1975; Geological Survey of Precambrian terranes of India has been a fundamental of India, 1993), or the Eastern Ghats Granulite Belt effort. The present study reviews the published and was regarded as Mesoproterozoic and was differenti- unpublished geochronologic data, provides a new ated from the remaining South Indian granulite geochronotectonic division of granulite terranes of terranes, which were considered older (e.g. Radha- Peninsular India and constrains the assembly of 137