الملخص

Veins, vienlets, pockets and cavity- filling deposits of barite are found to be associated with Upper Jurassic Formations (Marsis deposit) and Upper Cretaceous Bekhme Formation (Lefan deposit). The strontium isotope ratios of barite are presented here and the data have been used to understand the source and origin of barite. The relation of barite mineralization with carbonate host rocks reveals a stratabound epigenetic origin for barite. The obtained 87Sr/86Sr ratios range from 0.708226 to 0.708452; these values reveal the possibility of involvement of crustal Sr in the deposition of Marsis and Lefan barite. Isotopic data reveal that strontium in barite is derived from coeval seawater of Late Cretaceous and other processes like mixing of low temperature hydrothermal solution derived from the crust that is rich in radiogenic 87Sr.