Adakitic rocks from slab melt-modified mantle sources in the continental collision zone of southern Tibet

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

“…(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). Lhasa crustal basement and the lower crust component of the Lhasa terrane proposed by Zhu et al (2012a) and Miller et al (1999) respectively.…”

“…Gao et al (2010b) suggested that none of the exposed Lhasa crustal basement or the juvenile crust could adequately explain the magma derivation for the Gangdese adakites. 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.…”

Geochemical variations in Miocene adakitic rocks from the western and eastern Lhasa terrane: Implications for lower crustal flow beneath the Southern Tibetan Plateau

“…1), Guo et al (2007) suggested that the different geochemical and Sr-Nd isotope compositions of adakitic rocks in the eastern and western Lhasa terranes are the result of mixing between ultrapotassic magmas and lower crustal melts beneath the Lhasa terrane. Accordingly, the adakitic rocks in the western Lhasa terrane should display higher K 2 O and K 2 O/Na 2 O values than those from the eastern Lhasa terrane (Gao et al, 2010), corresponding to other transitional characteristics, such as K 2 O concentrations and older Nd model ages between the Miocene ultrapotassic rocks and the adakitic rocks in western Lhasa. However, these regional characteristics are not seen (Figs.…”

“…Third, Xu et al (2010) reported that the melting of mafic granulites in the Himalaya terrane results in relatively low K 2 O concentrations, which are inconsistent with the high K 2 O content of adakitic rocks in the Lhasa terrane. In addition, based on the Sr-Nd isotope composition of adakitic rocks in the Lhasa terrane, Gao et al (2010) considered that the mafic granulite in the Himalaya terrane is unlikely to be a non-radiogenic end-member for the mixing array in the Sr-Nd plot. Finally, the adakitic rocks in the Lhasa terrane have different Sr-Nd isotopic characteristics to the gneiss and granites of the North Himalayan (Zhang et al, 2004) and High Himalayan Crystalline Series (Harris et al, 1988), which have anomalously enriched Sr-Nd isotopic compositions relative to the adakitic rocks (Fig.…”

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 adakitic intrusive rocks within the Gangdese batholith are considered to have been generated in two main stages, the Jurassic-Cretaceous (160-77 Ma) and : (1) Jurassic-Cretaceous adakitic rocks generated in an arc setting were related to Neo-Tethyan subduction processes, by melting of either subducted oceanic slabs (e.g., Jiang et al, 2012;Ma et al, 2013a;Wei et al, 2007;Zhang et al, 2010b;Zhu et al, 2009) or thickened mafic continental lower crust (e.g., Guan et al, 2010;Wen et al, 2008b); (2) Cenozoic adakitic rocks occurring as small-volume plugs or dikes/sills, which intrude or crosscut the Gangdese batholith, the Linzizong volcanic successions and associated sedimentary formations, and extend~1300 km across nearly the entire southern Lhasa (Fig. 1b) (e.g., Chung et al, 2003Chung et al, , 2005Chung et al, , 2009Gao et al, 2007Gao et al, , 2010Guan et al, 2012;Guo et al, 2007;Hou et al, 2004Hou et al, , 2012Ji et al, 2012;Jiang et al, 2011Jiang et al, , 2014Pan et al, 2012;Xu et al, 2010;Zhang et al, 2010a).…”