Petrology of Deccan Trap Basalts of the Western Ghats Around Igatpuri and their Petrogenetic Significance

Major and trace element analyses of sixteen samples of basaltic rocks. representing a vertical section of 1600m (from Bhiwandi to Jgatpuri and beyond into Kalsubai Hill) of the Western Ghats, are presented. The analyses show a very wide variation in Mg number, and indicate very distinct differentiation trends. The MgO contents vary between 4.55% and 12.43% showing a continuous variation from tholeiitic basalts to picrite basalts that are enriched in phenocrystal olivine. It is shown that the MgO-rich picritic basalts have differentiated to form the normal low-MgO basalts. It is also shown that the very high contents of MgO is due to accumulation of phenocrysta] olivine.