Helium isotopic geochemistry of HP-UHP eclogite facies metamorphic rocks： a review

Abstract：The helium isotopic composition of each sphere of the Earth has its characteristic isotopic ratios. These ratios show significant differences. Therefore, helium isotopes, as a tracer, are more sensitive than other isotopes to distinguishing crust from mantle materials. Up till now, geochemical behaviors of helium isotopes during the HP-UHP metamorphism have not been well studied, it led to the limited application of helium isotope in eclogites. Many HP-UHP eclogite belts have been discovered in China. These eclogites can be genetically classified into two types： one is associated with subduction of the continental slab, and the other is formed by the subduction of the oceanic slab. This paper reviewed the progresses therefore of HP-UHP eclogite facies metamorphic rocks well studied and some problems and future work of the application of helium isotope in eclogites are also discussed.