Pillow Basalts from the Manipur Ophiolitic Complex (MOC), Indo-Myanmar Range, Northeast India

Pillow basalts have been reported from the Manipur Ophiolitic Complex (MOC) of the Indo-Myanmar Range. The pillows are closely packed together or individualistic and they are varying from 50 cm to 0.5m in diameter and vary from undeformed spheroid to flattened ellipsoids. They are ranging from silica undersaturated nephenine in norms) to silica saturated (hypersthene in norms) with respect to silica and characterized by enrichment of Large Ion Lithophile Elements (LILE) and depleted of TiO₂, P₂O₅, Nb, Nb/Y values with high concentration of Al₂O₃, Cr, Ni and affinity with sub-alkaline and tholentic basalt in composition. The sub-aqueous natures of volcanism are indicated by the presence of pillow structures. Petrological and geochemical studies indicate that pillow basalts of Manipur Ophiolitic Complex are derived from a common source at higher degree of partial melting and possibly emplaced in a plate margin environment, which could be in a back arc basin of an oceanic environment that overlap the N-type MORB and IAB.