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High-pressure(HP) veins were extensively developed in western Tianshan high-pressure(HP) metamorphic belt. The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids. Analytical data show that the immediately adjacent host-rocks of the studied HP vein are eclogites and gradually turned into blueschist as the distance from the veins increases, which indicates that the vein-forming fluid was derived from adjacent host-rocks; the boundaries between the vein and the host-rocks are sharp, which indicates that the fracture of the host-rocks is brittle during the vein-forming process. It is suggested that this type of HP veins is precipitated from the liquid formed by the dehydration of the host-rocks during the prograde metamorphism from blueschist to eclogite facies, which results in hydrofracturing of the rocks and provides the space for the vein to precipitate. The width of the eclogite-facies host-rocks is usually 1–2 cm, which provides the direct evidence that the fluid flow is on centimeter-scale.

Shaxi porphyry Cu-Au deposit was one of the important discoveries of the exploration in the middle-lower reaches of Yangtze River in China in 1970’s. Gold occurrence in the Shaxi porphyry copper-gold deposit (central Anhui province, eastern China) was investigated by means of microscope analyses, EPMA and PIXE. Combined with geological and mineralogical methods, the characteristies of occurrence of gold in the large scale sulfide mineralization in this region were fully investigated. The results show that gold distributes in both chalcopyrite and pyrite as submicroscopic inclusions (less than 1 µm). Au is positively correlated with As, Fe, S, Cu, Zn and Ti. The condition of gold transformation in thermal fluid system controlling deposition of Au in the region is probably the oxidation potential of the red sedimentary rocks of shale and fine grain sandstone which may be crucial as a geochemical barrier to the reducing fluid. This study lays foundation for the further research and exploration of the porphyry copper-gold deposit both theoretically and practically in the lower reaches of Yangtze region.