Studies of metamorphic vein in ultrahigh-pressure rocks

Metamorphic veins enclosed in ultrahigh-pressure rocks provide an unique opportunity to trace fluid activity during continental subduction. High-ultrahigh pressure rocks may contain "pure" quartz-vein (quartz content >98%), and variably complicated polymineral "impure" vein. Recent studies show that these metamorphic veins can be used to improve the understanding of fluid/melt nature and element transfer in continental collision zones. At present, the main scientific questions include: (1) identifying the fluid/melt nature that formed the variable metamorphic veins; (2) obtaining the ability and scale of major and trace element transfer (especially for the fluid-immobile HREE and HFSE) during veining, and investigating the difference in fluid/melt nature affects on the element geochemical behavior under UHP metamorphic conditions; (3) acquiring the exact timing of veining.