Mineralogical Studies of Kerur Formation Badami Group, Kaladgi Basin, Karnataka

Abstract

Heavy and clay mineral analysis is a significant tool to interpret the provenance and paleoclimate of sandstone in proterozoic intracratonic Kaladgi-Badami basin, southern India. The distributions of heavy minerals are more in lower conglomerate; at the depth of 162.35m, zircon is 9.01%, magnetite is 74.18% and ilmenite is 24.61%. The ZTR index is 97.02%. The lower part of the upper unit of core quartz arenite, at the depth of 70.55m shows the following distribution of heavy minerals; zircon 2.94%, magnetite 50.84% and ilmenite 35.71%. The ZTR index of the quartz arenite is 65.52%; moderately abundant heavy minerals are tourmaline, rutile, and garnet; less abundant mineral is zircon in the core. The clay deposits in the basal arenite unit starts from 187 to 171.45m. The X-ray diffraction patterns shows 75% of Illite at the depth of 187m and 181.4m, 40% of chlorite at the depth of 181.7m, 36.36% of monmorillonite and 25% of kaolinite at the depth of 183m but 36.36% at the depth of 177.1m. kaolinite peaks are identified only in two samples. The study reveals that intense weathering in humid climate was responsible for alteration of granitic source rocks in the formation of kaolinitic clays in an acidic environment. The ZTR index reflects that the Badami sediments have attained moderate to high mineralogical maturity. The inference made out of the assemblage of heavy minerals point out that the Badami sediments have been sourced mainly from granitic and metamorphic terrain with a broad drainage basin. In most sandstone and conglomerate, the average ZTR index is moderate but varies widely among samples; apparently local lithologic source area variations largely control these relatively unmodified heavy mineral assemblages.