Proterozoic Mobile Belts of Gondwana -Comparative study of Precambrian geology between India and Antarctica-

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Under the present research project (2 years, 1993-1994), 25 scientists from Japan and 13 scientists in India, totalizing 813 man-days, were funded for the field activities and related expenditures (total fund was 21,000,000 yen). The field survey covered Precambrian terrains in southern to southeastern Peninsular India and collected geologic data including rock samples of more than 3,000 kg in weight. Preliminary results of our work appeared in about 26 papers (all in English) and 32 oral presentations mostly in international symposiums. Important points of these works are given below.(1) Recent geologic informations of India, Antarctica and Sri Lanka were critically summarized and correlated. The Gondwana during late Proterozoic is found to be principally similar to that of Mesozoic.(2) Several mineral isochron ages of ca 500 Ma have been newly reported for granulites south of the Palghat-Cauvery tectonic line. Thus, the Precambrian of Peninsular India is divided into the Archaean terrain north of the tectonic line and the Proterozic terrain with dominant ca 500 Ma events to the south.(3) A Sm-Nd mineral isochron age of 3.0 Ga was first reported from the classic Madras granulite. Several Pb-Pb rock isochron ages were first obtained from rocks of the Karimnagar Granulite Belt south of Godavari Valley, and indicated that the granulites were formed during Archaean older than ca 2.6 Ga.(4) The granulite formation and correlatable events during the Pan African stage were identified in South India, Sri Lanka and Antarctica. An extensional tectonic model associated with the CO_2 flushing related with the mantle degassing was presented for the granulite events in the above areas.(5) Importance of the ca 1.1 Ga belt surrounding East Antarctica was pointed out and the term Circum East Antarctic Mobile Belt has been proposed. The belt is suggested to be principally related to the birth of the East Gondwana.