Occurrence of kornerupine-bearing granulite from Karimnagar, Andhra Pradesh

Here, we report the occurrence of kornerupine-bearing, quartz-free granulite from the Malial area of Karimna. gar district, Andhra Pradesh. It occurs as small enclaves and pods within the granite-gneiss, associated with garnet-orthopyroxene-cordierite-biotite-gneiss. Its mineral assemblage includes kornerupine-cordieritebiotite-spinel, K-feldspar, ilmenite and magnetite. Kornerupine, a hydrated magnesium-aluminium silicate plots on the 4MgO-3Al(2)O(3)-4SiO(2) (4: 3: 4) composition along the solid solution join between 4: 3: 4 and 1:1:1 (3.5MgO.3.5Al(2)O(3).3.5SiO(2)) compositions. The relative X-Mg values among various minerals are as follows: cordierite > biotite > kornerupine > spinel. The deduced post-peak metamorphic pressure-temperature conditions of 5-6 kbar and 650-750 degrees C for the kornerupine-spinel-bearing quartz-free granulites are consistent with the experimental work on stability of kornerupine in the MgO-Al2O3-SiO2-H2O system.