A new occurrence of sapphirine-bearing granulite from Podur, Andhra Pradesh, India

Abstract

We report here on a new occurrence of sapphirine bearing granulites in the high-grade granite gneisses from Podur. Podur is situated in the north-eastern part of the Eastern Dharwar Craton about 150 km NNE of Hyderabad, India. The common stable assemblage contains cordierite-biotite-sapphirine-spinel-corundum-K-feldspar. Interpretation of multiphase reaction textures in conjunction with mineral chemical data and topology in the (Fe,Mg)O-(Al2O3-K2O)-(SiO2-6K2O) system is consistent with the following reactions: \({\rm biotite} + {\rm corundum} = {\rm spinel} + {\rm K\hbox{-}feldspar} + {\rm H_2O}\)\({\rm phlogopite\ (in\ biotite)} + {\rm corundum} = {\rm eastonite\ (in\ biotite)} + {\rm spinel} + {\rm cordierite}\)\({\rm spinel} + {\rm cordierite} = {{\rm sapphirine}_{2:2:1}}^{*}\)\({\rm cordierite} + {\rm biotite} + {\rm corundum} = {{\rm sapphirine}_{7:9:3}}^{*} + {\rm K\hbox{-}feldspar} + {\rm H_2O}\)\({\rm sapphirine}_{7:9:3} + {\rm biotite} = {\rm cordierite} + {\rm spinel} + {\rm K\hbox{-}feldspar} + {\rm H_2O}\)\({\rm sapphirine} = {\rm cordierite} + {\rm spinel} + {\rm corundum}\)