Reworking of old continental lithosphere: an important crustal evolution mechanism in orogenic belts, as evidenced by Triassic I-type granitoids in the East Kunlun orogen, Northern Tibetan Plateau

Paleo-Tethyan evolution of Tibet as recorded in the East Cimmerides and West Cathaysides

“…We infer that the East Kunlun-A'nyemaqen strand of Paleo-Tethys began to open in the Carboniferous. Northward subduction of its oceanic lithosphere beneath the East Kunlun-Qaidam-Qilian terranes led to the formation of the Bulhanbuda magmatic arc at 270-185 Ma (Xiong et al, 2014) and of the west Qinling accretionary wedge at the active continental margin of the northern A'nyemaqen terrane ( Fig. 4B; Yan et al, 2012).…”

“…Post-collisional magmatism, facilitated by slab break-off, produced high-silica adakitic granitoids (230-185 Ma, e.g., Xiong et al, 2014), and was accompanied by focused extensional deformation and sedimentary basin development within the East Kunlun ocean basin. The overthickened orogenic crust also underwent partial melting, producing S-type granites.…”

Petrogenesis and geodynamic implications of the Mid-Triassic lavas from East Kunlun, northern Tibetan Plateau

“…The two northern elements are divided by the North East Kunlun Fault, whereas the Central East Kunlun and South East Kunlun sectors are separated by the Central East Kunlun fault (Jiang et al, 1992;Meng et al, 2013;Xia et al, 2014). There is a growing consensus that the EKOB has documented a complicated history of seafloor spreading, subduction, and terrane amalgamation between Gondwanaland and Laurasia since the Early Paleozoic (Jiang et al, 1992;Yang et al, 1996;Yin and Harrison, 2000;Zhang et al, 2004;Chen et al, 2008;Xiong et al, 2014). The Buqingshan-A'nyemaqen suture zone is divided from the Southern Zone by the South Kunlun Fault and linked to the Hohxil-Songpan-Ganzi Basin to the south .…”

“…Defining the northern border of Gondwanaland, the Buqingshan-A'nyemaqen ophiolites are remnants of the Paleo-Tethyan oceanic lithosphere (Yang et al, 1996). Yang et al (2004) and Jiang et al (1992) identified mid-ocean ridge basalts (zircon SHRIMP U-Pb age of 308 Ma) and arc basalts (whole-rock Rb-Sr isochron age of 260 Ma) in the EKOB; these are probably related to the seafloor spreading stage and the subduction stage of the Paleo-Tethys Ocean, respectively (Xiong et al, 2014). Previous studies have revealed that the Permian-Triassic magmatic rocks in the EKOB are mainly calcic to calc-alkaline, having formed during the subduction-related orogenic period and the subsequent syn-to post-collision stage (Harris et al, 1988;Jiang et al, 1992;Yin and Harrison, 2000;Mo et al, 2007a …”

“…However, these characteristics are not fully shown by dacites in this study (Mg# = 17-48 and Na 2 O = 1.99-3.23 wt%). Therefore, partial melting of Precambrian mafic basement with involvement of a mantle component is the most reasonable interpretation (e.g., Xiong et al, 2014). Zircons from rhyolites show large variations in εHf(t) values (up to 4 epsilon units) and indicate an open-system process or reflect hybrid melts derived from different end-members (Griffin et al, 2002;Hawkesworth and Kemp, 2006;Kemp et al, 2007;Li et al, 2015c).…”