LAUSR

ABSTRACT A comprehensive whole-rock geochemical study of peridotites and volcanic rocks from the Indo-Myanmar Ranges (IMR) ophiolites deduces the source and extent of mantle melting and role of subduction components in modifying its melt composition. Melt modelling yields partial melting in the range of ~5–25% (with a maximum up to 20%) from a depleted MORB mantle (DMM) source. Two types of subduction component seem to have modified the IMR volcanics. The addition of hydrous fluids from a subducting slab has enriched few IMR volcanics in large-ion lithophile elements (LILEs) while those enriched in LREEs were affected by melts derived from subducting sediments. The MORB-Arc basalt geochemical signatures of the IMR volcanics are attributed to the evolving magma as the extent of mantle melting increases under the influence of fluids/melts from the dehydrating slab/sediments in the later stages of subduction initiation (SI).