Fluid-fluxed melting in the Himalayan orogenic belt: Implications for the initiation of E-W extension in southern Tibet

The geochemistry of granite is largely controlled by physical and chemical parameters that are closely linked to tectonic processes in evolving orogenic belts. Therefore, temporal changes the geochemical compositions granites could be used infer critical shifts processes. Himalayan leucogranites crustal anatexis products, providing a case formulate petrogenetic models for test models. From west east, High Himalaya Tethyan Himalaya, two groups derived from fluid-absent melting (Group A) fluid-fluxed muscovite B), respectively. In Cona Mount Everest areas, Group B crystallized at 26−10 Ma, A formed 19−13 Ma. have higher CaO, Sr, Ba, Zr, Hf, Th, Sr/Y, Zr/Hf, Th/U, lower Rb, Nb, Ta, U, Rb/Sr, 87Sr/86Sr than those granites. These differences highlight role deep-origin fluids dissolution control accessory phases on silicic magma systems. Field microstructural observations show E-W extension occurred synchronously with intrusion melting. Elevated heat flow accompanying dehydrate hydrous minerals release deep-seated crust (e.g., Lesser Sequence). Such flux melt metasedimentary rocks within produce Together literature data, Lhasa terrane belt, extensions Tibet may initiated as early 26