THE FELSIC MAGMATIC PROVINCE IN EAST GONDWANA - IMPLICATIONS FOR PAN-AFRICAN TECTONICS

The East Gondwana crustal fragments, namely southern India, Sri Lanka, Madagascar, East Antarctica and Western Australia, preserve evidence for a prominent Pan-African felsic magmatic event represented by felds pathoidal syenites, alkali granites and syenites emplaced proximal to fault lineaments. In Peninsular India, late or post-kinematic alkaline plutons ranging in age from 864 to 600 Ma characterize the Eastern Gh ats belt, whereas a strong Pan-African imprint is provided by 550-750 Ma alkali granites and syenites in the southern granulite segment. In Sri Lanka, alkali granites occur in all major geologic units, with rad iometric ages in the range of 550-760 Ma. In Madagascar, alkali granit es and syenites with late Proterozoic to Palaeozoic ages are reported. Felsic magmatic activity in East Antarctica is characterized by post- tectonic granitic and syenitic plutons in Enderby Land and Queen Maud Land, showing an age range of 550-770 Ma. Pan-African felsic plutons i n Western Australia define ages of 550-570 Ma. This paper summarizes t he petrologic, geochemical and geochronologic characteristics of felsi c plutons in the various East Gondwana fragments. Many of the intrusiv es represent anorogenic A-type magmas generated in rift-related enviro nments of high heat flow and abundant volatile activity, correlative w ith an extensional tectonic regime and probably including melts genera ted from both upper mantle and lower crustal sources. This paper ident ifies a major Pan-African felsic magmatic province in East Gondwana, w hich, in association with their petrogenetic significance, is consider ed to be suggestive of a geodynamic signature of East Gondwana during the Pan-African period. Copyright (C) 1996 Elsevier Science Ltd