Neoproterozoic Overprinting on the Archean Western Dharwar Craton, Southern India: Records from LA-ICP-MS U-Pb Geochronology of Rutile and Monazite

Abstract

This study provides new evidence for a significant Neoproterozoic tectono-thermal event in the southern Dharwar Craton, based on U-Pb dating of rutile and monazite from metamorphic rocks of the Sargur Group. Trace element analysis of rutile in garnet-bearing amphibolite, amphibolite, garnet-bearing staurolite-kyanite schist, and grunerite-garnet schist suggests that their protoliths were primarily basaltic rocks, sediments with mafic component, pelitic sediments, and mixed sediments with both mafic and felsic components, respectively. Rutile U-Pb ages of 625 ± 22 Ma (garnet-bearing amphibolite), 752 ± 5.1 Ma (amphibolite), 836 ± 4 Ma to 663 ± 26 Ma (garnet-bearing staurolite kyanite schist) and 860 ± 13 Ma (grunerite-garnet schist), along with a monazite U-Pb age of 789 ± 4.4 Ma (garnet-bearing staurolite kyanite schist), record a significant Neoproterozoic (860–625 Ma) tectono-thermal event along the southern margin of the western Dharwar Craton. This event is most likely associated with aborted rift-related alkaline magmatism along the northern margin of the Southern Granulite Terrane (SGT) and the southern margin of the Dharwar Craton. Given the lack of direct evidence for the assembly of the Rodinia supercontinent in the Dharwar Craton and SGT, this Neoproterozoic event is unlikely to be related to the breakup of Rodinia.