Petrology and Geochemistry of Hornblendic Rocks from Kanigiri-Gogulapalle Area, Andhra Pradesh

Abstract Hornblendic rocks (hornblende schists, amphibolites, and hornblendites) occur in intimate association with metasedimentary schists and granitic rocks in the Kanigiri Gogulapalle area of Andhra Pradesh, India. Field studies indicate that a majority of these rocks are possibly concordant intrusives, some of them being metasedimentary. Petrographic study shows that most of them consist of hornblende and plagioclase as essential minerals, whereas some are characterized by tremolite and plagioclase with accessory calcic minerals. Absence of detrital minerals and pyroxenic cores in the amphiboles characterize all the rocks. Geochemical studies reveal that the rocks are most probably magmatic intrusives judged from the low Niggli k and high TiO2 values and the presence of high Sr, Cr, V, and Ni amongst the trace elements.