Tectonics of the Eastern GhaLs Mobile Belt of India -Study of Proterozoic Events in EasL Gondwana-

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Field based geological studies of Eastern Ghats, South India and Sri Lanka were conducted. Major results are as follows which appeared in 101 scientific publications.(1) Sm-Nd and Rb-Sr ages, and U-Pb isotopic and U-Th-Pb chemical ages of monazite and zircon were obtained. Circa 2500 and 2000 Ma of the precursory rocks, ca 1500, 1000, 700-800, and 500 Ma ages of repeated tectonothermal events were obtained.(2) Small scale rootless isoclinals folds and sheath folds proceeding the major isoclinals folds were identified in the central Eastern Gahts Mobile Belt.(3) Corundum-quartz assemblage were discovered in the metapelite from the central Eastern Ghats Mobile Belt. The metapelite suffered higher conditions than ca 13 Kb and 1150℃, and then drastic isothermal decompression to ca 9 kb and 950℃, followed by isosbaric cooling then isothermal decompression.(4) The polymetamorphic history of the Eastern Ghats Mobile Belt identified from the present study suggests that the juxtaposition with the Rayner Complex of Antarctica vas later than ca 1500 Na, and most possibly during the ca 1000 Ka event.(5) The Achankovil Shear Zone of South India vas found to have suffered the sinistral shear, at least in its central portion.(6) Petrological studies of granulites in central Sri Lanka and calc-silicate rocks and alkaline acid intrusive in South India, and tectonic studies of Precambrian East Gondwanaland were also examined.