Granitic orthogneiss contributions to the generation of Himalayan leucogranites: insights from the eastern Himalayas

Multi-component crustal sources are universally acknowledged as the overriding factor in causing geochemical heterogeneities of the Cenozoic Himalayan leucogranites. In previous studies, metasedimentary rocks from the Greater Himalayan Crystalline Complex were always underlined to be the dominant origin for leucogranites after the Eocene and Oligocene transition (ca. 2O conditions triggered by compressional thrust activity of the Main Central Thrust and arc-parallel extension have remarkably modified original source structures (infiltration by LHS-derived fluids) and melting behaviours (more recognized fluid-present partial melting cases). Consequently, the role the granitic gneisses would be strengthened because of the greatly improved fertility via fluid-present melting; and the Sr – Nd isotopic signatures of Himalayan leucogranites would be spatially-temporally evolved.