Tracing of the Deep Fluids in Western Tianshan by the Electron Microprobe Analyses of Omphacite Form High-Pressure Veins and Host-Rocks

Abstract

Western Tianshan High-pressure (HP)-metamorphic belt is characterized by developed High-pressure (HP) veins, which are composed by HP-metamorphic minerals. The host rocks of the HP-veins are mainly composed by eclogites and blueschists. As the direct record of the deep fluids in the paleo-subduction zones, the HP-veins can provide us deep samples for probing into the deep fluids in the subduction zones. Fluids in the deep subduction zones play an important role in crust-mantle exchange related to plate subduction process. The electron microprobe analyses of HP-metamorphic minerals omphacite inside the veins and host rocks in western Tianshan high-pressure metamorphic belt is mostly paid attention. The result shows that the composition of the omphacite from HP-veins have the same composition of the omphacite from the host rocks, which indicates that the fluids from which the HP-vein precipitated originated from the host rock.