Geochronology of the Dharwar Craton - A Review

The relevance of isotope age data in delineating the genetic relationships between the broad types of Archaean terrains of the Dharwar craton - viz., the greenstone belts, the granites and migmatites and the granulite facies complexes - is pointed out. The main results of the Rb-Sr isochron measurements carried out in this laboratory are summarized. The conglomerates have yielded the highest ages observed in this study, (3250 ± 150 m.y.), while two emplacement events at 2950 m.y. and 2600 m.y. have been observed in the migmatites and gneisses with evidence of metamorphic overprinting at 2300 m.y. and 2000 m.y., the latter being reflected in the Closepet event. While a whole rock isochron of 2475 m.y. has been observed for Chitradurga granites, the age relationships between the greenstones and granites still remains to be solved.