Whole-rock geochemistry of augen gneiss from southeast of Dumka, Jharkhand, India

Abstract

The Chhotanagpur Granite Gneiss Complex (CGGC) exhibits various geological signatures that attract many geologist and researchers for detail investigation. The present paper focused on the petrography and geochemistry of augen gneiss exposed in the southeast of Dumka, Jharkhand. As in other areas of the CGGC, augen gneiss was the main rock exposure. They were coarse-grained and light colored rocks exhibiting well gneissic characteristics. The rock was mainly composed of quartz, feldspar, hornblende, pyroxene, biotite, garnet and other opaque minerals. It was also rich in alumina and potash contents. There was also a pronounced negative Eu anomaly which suggested that both K-feldspar and plagioclase were not removed in the differentiation sequence. As the whole CGGC experienced different orogenic activities, the studied rocks also showed various deformation effects. The augen gneiss was found to be originated from granite to granodioritic igneous parentage of calc-alkaline composition in the tectonic setting within plate granite.