Microthermometric study of apatite occurring in the proterozoic ultramafic rocks of Aravalli Supergroup, Jharol Area, Udaipur, Rajasthan, India

Coarsely crystallized, semi precious green and yellow varieties of apatites are occurring in talcosic ultramafic rocks of the Jharol area. XRD data shows that the green variety is hydroxyl-chlorapatite while, the yellow variety is a fluor apatite. Fluid inclusion studies carried out on these apatite samples reveal that majority of primary inclusions in hydroxyl-chlorapatite are H2O-CO2 type while, the fluorapatite contains biphase aqueous inclusions without visible CO2 suggesting that the metamorphic fluids were C-O-H type in southern part and aqueous type with low salinity in northern part of the area. Microthermometric data coupled with stable mineral phases (or metamorphic index minerals) confirm that steatitisation of ultramafic rocks took place at about 400º-490 ºC temperature and 2 to 3 kb pressure with metamorphic gradient increasing from north to south in the area.