Detrital Origin of Fuchsite-Bearing Quartzites in the Western Dharwar Craton, Karnataka, India

Abstract

Abstract Quartzites in the Nuggihalli (Banavara), Holenarsipur, JavanahaIli, Bababudan and Chitradurga schist Belts were evaluated using petrographic and chemical methods. All the examined quartzites originated as clastic sandstones, none as inorganically precipitated cherts. Chromium is introduced to the oldest quartzites in the form of detrital chromite. Fuchsite is forming in association with this chromite during metamorphism. There is no evidence for significant contributions of hydrothermal Cr. There are secular trends in median Cr/Al2O3, Cr/Fe2O3, Cr/Zn and K2O/AI2O3 ratios. These trends are consistent with the gradual evolution of mafic and sialic sedimentary source tenanes over the interval from approximately 3.5-2.5 Ga ago. The compositions of the quartzites from Javanahalli and Bababudan Belts are sufficiently different to suspect, but not prove, they are from different sources.