New geochemical data for mafic intrusions within the Eocene Nisai Formation along the suture zone between the Indian and Eurasian plates are used to constrain their petrogenesis and assess the local tectonics and mantle dynamics. Petrological and geochemical data indicates that these alkalic intrusions have moderately enriched incompatible trace element compositions similar to ocean island basalt (OIB) magmatism. Modelling suggests these intrusions are the result of 1-5% melting of a deep, enriched, predominantly garnet-lherzolite, with a small amount of subduction-derived fluids. These melts then underwent fractional crystallisation at lithospheric depths of ~30 km.