ON THE KHONDALITES OF THE EASTERN GHATS GRANULITE BELT, INDIA

摘要

Khondalite is largely characterized by the equilibrium mineral assemblage of quartz-K feldpar-sillimanite-gamet-ilmenite. Biotite or rutile is noticed occasionally. Presence of quartzite bands within khondalite and variation of mineral proportions in khondalite strongly indicate the sedimentary nature of the precursor. Quartzo-feldspathic leucosome is present on all scales within khondalite in an irretrievably entangled fashion, indicating the melt-bearing nature. Thus, the assemblage of the khondalite is suprasolidus in nature. Mineral chemical data, bulk chemical data and phase equilibrium modelling of the khondalite also support the suprasolidus nature of the khondalite assemblages. The phase equilibrium modelling points to the facts that (1) biotite bearing assemblage is a product of chemical variation in the protolith and (2) rutile bearing assemblage represents relatively high pressure inherited equilibrium. A near isothermal decompression segment can explain the mineralogical variations of the khondalites.