Further Zircon U-Pb Age Data for the Daginkatte Formation, Dharwar Supergroup, Karnataka Craton

SHRIMP U-Pb analyses of zircons from a rhyolite sample collected from the Daginkatte Formation of the Chitradurga Group (Dharwar Supergroup), close to the type locality, give an age of 2601 ± 6 Ma (1σ 23 of 24 analysed grains). This is within error of the 2614 ± 8 Ma (2σ 11 grains) recently reported by A.P. Nutman and his colleagues in 1996 from a sample of acid volcanic schist of the same formation, about 25 km along strike. Combining Nutman et aI's (1996) published data with the new analyses reported here gives a pooled age of 2606 ± 6 Ma (n = 34, 1σ, χ² = 1.31), within error of both of the separately determined ages. Having regard to the reported uniform lithology of the Daginkatte Fonnation, the pooled age is probably that of a short magmatic event during which it was formed, and provides a firm constraint relevant to this stratigraphic level of the Chitradurga Group; however. it is now important to determine whether the rhyolitic rocks of the Daginkatte Formation are intrusive or extrusive.