抄録
We report newly obtained U–Pb SHRIMP ages of zircons from the granitoids in the vicinity of Chitradurga shear zone of Dharwar craton, South India. The analyses yielded two different ages, an older age of ca. 3300 Ma and younger ages of ~ 2600–2650 Ma, those suggest two major igneous activities in the study area. The former activity contemporaneous with the formation of Mesoarchean (~ 3.3 Ga) basement rocks (i.e., Peninsular Gneiss) and the latter reflects the Neoarchean (~ 2.6 Ga) regional plutonic activity in the Western Dharwar craton. Field and petrographic observations suggest that the intensity of deformation is high at the boundary between amphibolites and granitoids. Our new age dates imply that the formation of Chitradurga shear zone postdated the magmatic activity in the study area and the deformation structures possibly related to the development of Chitradurga shear zone. The area on either sides of the boundary between Eastern and Western Dharwar cratons experienced a Neoproterozoic event between 700–600 Ma indicated by prominent SHRIMP lower intercepts.
