Mantle contributions to crustal thickening during continental collision: Evidence from Cenozoic igneous rocks in southern Tibet

The formation of Qulong adakites and their relationship with porphyry copper deposit: Geochemical constraints

“…IS-0000 from GIGCAS. (Hou et al, 2004b;Qin et al, 2014) and this study, Gangdese Miocene adakites (Gao et al, 2010a;Hou et al, 2004bHou et al, , 2012Wang et al, 2010;Xu et al, 2010), Yarlung Tsangpo ophiolite (Miller et al, 2003;Niu et al, 2006;Xu and Castillo, 2004;Zhang et al, 2005), Linzizong volcanic rocks (Gao et al, 2008;Mo et al, 2007), Indian Ocean pelagic sediment (Benothman et al, 1989), Himalayan basement (Vidal et al, 1982). Cretaceous adakites: Zhu et al (2009);Jurassic porphyries: Yang et al (2011); Miocene adakites: Gao et al (2010b), Hou et al (2013), Hou et al (2004b) and Wang et al (2010).…”

“…Obviously, in spite of their wider ranges in Sr-Nd isotope compositions, many of the Qulong adakites have higher Sr-Nd isotopic compositions than that of the Linzizong volcanic rocks (Fig. 12), which may be equivalent to the juvenile crust in the Lhasa terrane during the Eocene (Mo et al, 2007). Moreover, the Miocene adakites occur in an E-W trending 1500 kmlong narrow belt along the Yarlung Tsangpo suture zone, whereas the voluminous Linzizong volcanic rocks mainly crop out north of the adakite belt.…”

Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet

“…The IYTS marks the closure of the Tethys, and lies on the southern boundary of an east-west-trending Andean arc-type calc-alkaline magmatic zone (including the Yeba, Sangri, Linzizong volcanic successions and the Gangdese batholith) in the Lhasa block ( Fig. 1a) (e.g., Coulon et al, 1986;Mo et al, 2007;Zhu et al, 2008).…”

“…Magma mixing generally requires mantle-derived basaltic and crust-derived felsic endmembers (e.g., Streck et al, 2007). In southern Lhasa, the candidates for mantle-derived basaltic and crust-derived felsic end-members are most plausibly represented by the 65-40 Ma Linzizong mafic magmas (e.g., Lee et al, 2012;Mo et al, 2007) and the synchronous (45-53 Ma) Gangdese granites (e.g., Ji et al, 2009Ji et al, , 2012Wen et al, 2008a), respectively. However, the ε Nd (t) and ε Hf (t) values of the Napuri adakitic rocks are lower than those of both the felsic and basaltic end-members, Defant and Drummond (1990) and Petford and Atherton (1996).…”

“…48 Ma), coinciding with the peak Gangdese magmatic activities at ca. 50 Ma (Chung et (Xu and Castillo, 2004); Himalayan sedimentsHimalayan leucogranites (Guo and Wilson, 2012); Cretaceous adakites (Jiang et al, 2011;Ma et al, 2013a;Zhu et al, 2009); 80 Ma thickened mafic lower crust-derived adakitic rocks (Wen et al, 2008b); the Linzizong volcanic rocks (Lee et al, 2012;Mo et al, 2007); Cenozoic (Oligo-Miocene) adakitic rocks (Gao et al, 2010;Guan et al, 2012;Guo et al, 2007;Hou et al, 2004;Ji et al, 2012;Jiang et al, 2012;Xu et al, 2010;Zhang et al, 2010a); the Amdo orthogneiss (Harris et al, 1988); sample NL-07 (leucogranite, representing the Himalayan sediments (Nd = 11.1 ppm, ε Nd (t = 47 Ma) = −15.9, Sr = 89.0 ppm, ( 87 Sr/ 86 Sr) i = 0.7372) (Guo and Wilson, 2012). Data sources for (b): Hf isotopic results of Late Cretaceous adakites (Ma et al, 2013a); fields of Hf-Nd isotopic data for Indian Ocean MORB, OIB and mantle array (Chauvel and Blichert-Toft, 2001;Ingle et al, 2003).…”