The Grenvillian orogeny in the Altun–Qilian–North Qaidam mountain belts of northern Tibet Plateau: Constraints from geochemical and zircon U–Pb age and Hf isotopic study of magmatic rocks

Petrogenesis of the early Paleozoic low-Mg and high-Mg adakitic rocks in the North Qilian orogenic belt, NW China: Implications for transition from crustal thickening to extension thinning

“…The basement consists of felsic gneiss, marble, amphibolite and minor granulite. The Qilian block was previously considered to be a fragment rifted from the North China craton, but recent geochemical and geochronological data demonstrate that the metamorphic basement has a close affinity to the Yangtze craton (South China block; e.g., Wan et al, 2006;Yu et al, 2013b). Along the northern margin of the Qilian block, several ca.…”

The multi-stage tectonic evolution of the Xitieshan terrane, North Qaidam orogen, western China: From Grenville-age orogeny to early-Paleozoic ultrahigh-pressure metamorphism

“…Bulk rock geochemical signatures resemble N-MORB, E-MORB or near sea mount basalts (C. Zhang et al, 2013). Considering available 750-800 Ma and 877 ± 8 Ma protolith ages, preserved in zircon cores (Zhang et al, , 2011a, it is inferred that some of the Xitieshan terrane eclogites originate from Neoproterozoic protoliths, interpreted to be emplaced onto the continental crust long before the early Paleozoic subduction/collision event leading to UHP metamorphism in North Qaidam (C. Zhang et al, 2013). The age of the eclogite facies metamorphism, preserved in zircon rims, was determined, both by SHRIMP and SIMS analyses, to have taken place at 440-460 Ma and 433 ± 3 Ma, respectively (Song et al, 2011;Zhang et al, 2011a;Liu et al, 2012).…”

“…Zhang et al, 2008;Song et al, 2012). Therefore, the Neoproterozoic Grenville-age metamorphism and the magmatic belt occurred coevally and most probably form remnants of an active continental margin (Song et al, 2012Yu et al, 2013).…”

“…In terms of bulk-rock geochemical and Sr-Nd isotope characteristics, low-Ti and high-Ti eclogite compositions have been identified in the Xitieshan terrane. Bulk rock geochemical signatures resemble N-MORB, E-MORB or near sea mount basalts (C. Zhang et al, 2013). Considering available 750-800 Ma and 877 ± 8 Ma protolith ages, preserved in zircon cores (Zhang et al, , 2011a, it is inferred that some of the Xitieshan terrane eclogites originate from Neoproterozoic protoliths, interpreted to be emplaced onto the continental crust long before the early Paleozoic subduction/collision event leading to UHP metamorphism in North Qaidam (C. Zhang et al, 2013).…”

“…bimineralic and phengitebearing eclogite (C. Zhang et al, 2009). Both types show different geochemical and isotopic characteristics (C. Zhang et al, 2013). Some Bim-eclogites are characterized by low Ti contents and low I Sr ratios preserve both an eclogite protolith U-Pb zircon age of 877 Ma and a continental lithosphere subduction U-Pb zircon age whereas other Bim-eclogites, characterized by high Ti contents and high I Sr ratios, only show in their U-Pb zircon record the 440-460 Ma oceanic subduction ages but the Neoproterozoic zircon cores are lacking (Zhang et al, 2011a).…”