FLUID INCLUSION EVIDENCE FOR AMPHIBOLITE-GRANULITE FACIES TRANSITIONAL METAMORPHISM IN DELHI SUPERGROUP OF ROCKS

The Deri-Ambaji massive sulphide deposits are associated with the Prec ambrian rocks of Delhi Supergroup. Detailed fluid inclusion studies of quartz associated with the host rock of sulphide deposit as well as w ith ores show high density CO2 (1.05-1.08 g/cm3) as the dominant fluid phase and CO2-H2O (0.94-0.98 g/cm3) and minor H2O inclusions are also present. The isochore for the high density fluid inclusions indicate the pressure limit of 7.5 Kbars, at the upper temperature limit 800-de grees-C, which is in accordance with the estimation by mineralogic the rmobarometery. The lower P-T limit is of 2.5 Kbar at 500-degrees-C, wh ich indicates that the transition of upper amphibolite to granulite fa cies o f metamorphism has taken place in the area. The P-T path deline ated from combined mineralogical and fluid data is characterised by T- convex nature, which is indicative of isothermal crustal uplift, proba bly promoted by extensional tectonics.