Ortho- and Clino-Pyroxenes from the Charnockite Series of Amaravathi, Andhra Pradesh, South India

Abstract

The chemical analyses, structural formulae, and optical data of seven orthopyroxenes and six clinopyroxenes, all from the charnockite series of Amaravathi, are presented. The orthopyroxenes are in the hypersthene-ferrohypersthene range while the clinopyroxenes are in the sahlite range. The aluminous nature of the pyroxene is believed to be the result of high pressure. The clinopyroxenes have the granulite trend on the Wo-En-Fs plot. The tie-line projections and the K_D values for the pyroxene pairs indicate conditions of chemical equilibrium around 670 °C for the charnockite series of Amaravathi.