Abstract
In the Archean Dharwar craton of southern India N-S trending belts of metabasic rocks are exposed which underwent regional metamorphism at about 2.5 Ga ago. The progressive changes in the assemblages and mineral chemistry of metabasites was studied in a N-S traverse covering the Chitradurga and Nagaman-gala belts, the Sargur area, and the Nilgiri Hills. Towards the south with increasing metamorphic grade greenschists ($$chl + act + ab + ep \pm carb$$, qtz) give way to amphibolites ($$hbl + plag \pm qtz$$, gar, cumm) and mafic granulites ($$pyx + plag + gar \pm hbl$$, qtz). The amphibole composition changes from actinolite in the greenschist zone to tschermakitic hornblende in the amphibolite zone and pargasitic-hastingsitic hornblende in the granulite zone. The Ti content of the amphiboles systematically increases in this direction. The plagioclase composition changes from albite in the greenschist zone to oligoclase/andesine in the amphibolite zone and andesine/labradorite in the granulite zone. Almandin...
Published Version
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