The Multi-Stage Tectonic Evolution of the Xitieshan Terrane,North Qaidam Orogen,NW China:from Grenville-Age Orogeny to Early-Paleozoic Ultrahigh-Pressure Metamorphism

The geodynamic evolution of the Early Paleozoic ultrahigh-pressure metamorphic belt in North Qaidam,western China,is controversial due to ambiguous interpretations concerning the nature and ages of the eclogitic protoliths(Martinson et al.,2006;Song et al.,2006;Yang et al.,2006).Within this framework we present new LA-ICP-MS U-Pb zircon ages from eclogites and their country rock gneisses from the Xitieshan terrane,located in the central part of the North Qaidam UHP metamorphic belt(Fig.l).Xitieshan eclogites contain clearly different protoliths characteristics and as such provide a natural laboratory to investigate the geodynamic evolution of the North Qaidam UHP metamorphic terrane(e.g.Zhang C.et al.,2013).LA-ICP-MS U-Pb zircon dating of three phengite-bearing eclogites and two pelitic gneisses from the Xitieshan terrane yielded 424-427 Ma and 917-920 Ma ages.The age of 424-427 Ma,consistent with geochemical and geochronological data from the former literature,is interpreted to date continental lithosphere s...The geodynamic evolution of the Early Paleozoic ultrahigh-pressure metamorphic belt in North Qaidam,western China,is controversial due to ambiguous interpretations concerning the nature and ages of the eclogitic protoliths(Martinson et al.,2006;Song et al.,2006;Yang et al.,2006).Within this framework we present new LA-ICP-MS U-Pb zircon ages from eclogites and their country rock gneisses from the Xitieshan terrane,located in the central part of the North Qaidam UHP metamorphic belt(Fig.l).Xitieshan eclogit中国地质学会、美国地质学会3Vol.8