Lamproitic Rocks from a Continental Collision Zone: Evidence for Recycling of Subducted Tethyan Oceanic Sediments in the Mantle Beneath Southern Tibet

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

“…Previous studies have shown that the adakitic rocks are K-rich, forming a 1000-km-long belt oriented sub-parallel to the IYS. The ages of the adakitic rocks range from 26.2 to 10 Ma (Cai et al, 2005;Chung et al, 2003Chung et al, , 2009Gao et al, 2007a;Guo et al, 2007;Hou et al, 2004;Xu et al, 2010;this study), within the range of the 22.5-12 Ma ages obtained for potassic-ultrapotassic igneous rocks in the Lhasa terrane (e.g., Ding et al, 2003;Gao et al, 2007b;Miller et al, 1999;Nomade et al, 2004;Williams et al, 2001Williams et al, , 2004Zhao et al, 2009), except for the 26.2 Ma age of adakitic rocks in Linzhi (Chung et al, 2003). Recently, Miocene adakitic dykes have been found on the southern side of the IYS, including the Mayum and Kuday dykes King et al, 2007) within the northern belt of the Tethyan Himalayan tectonic zone.…”

“…First, the Miocene adakitic rocks in Southern Tibet are found in the interior of a continent setting, which is inconsistent with a simple model of slab melting in an arc setting (Guo et al, 2007). Second, although these adakitic rocks are spatially and temporally associated with ultrapotassic rocks, they have Sr-Nd isotope compositions that distinguish them from the ultrapotassic rocks, suggesting an origin incompatible with the AFC model of ultrapotassic magma generation (Gao et al, 2007a(Gao et al, , 2007bGuo et al, 2007). Third, most adakitic rocks in Southern Tibet have relatively low contents of Cr, Ni, and other compatible elements, which is inconsistent with a model of melting involving delaminated lower crust .…”

“…Drummond and Defant (1990) and Martin (1986), and (b) La N /Yb N vs. Yb N after Defant and Drummond (1990) and Petford and Atherton (1996), showing the fields for adakite and arc intermediate-felsic rock. Data sources are as follows: Linzizong volcanics and the Gangdese batholith are from Zhang (1996), Jiang et al (1999), Song (1999), and Wu et al (2005; K-rich magmatic rocks are from Miller et al (1999), Williams et al (2001Williams et al ( , 2004, Ding et al (2003), Nomade et al (2004), andGao et al (2007b) (other data sources are as in Figs. 1 and 3).…”

“…The groundmasses of these porphyries consist mainly of plagioclase, alkali feldspar, biotite, quartz, zircon, Fe-Ti oxides, titanite, apatite, and glass. The petrographic characteristics of these adakitic rocks have been described by Hou et al (2004), Guo et al (2007), and Gao et al (2007aGao et al ( , 2007b. In the western Lhasa terrane, the adakitic rocks occur as erupted lavas or small intrusive bodies.…”

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

“…12. Also plotted are literature data for Jurassic porphyries from Qulong , Cretaceous adakites from Mamen ), Lizizong volcanics (Mo et al, 2008) and Miocene adakites Hou et al, 2004bHou et al, , 2013Qin et al, 2014;Xu et al, 2010) and fields of Indus-Yalung ophiolites (Miller et (Zhu et al, 2012a) and ultrapotassic rocks from south Tibet (Gao et al, 2007a;Liu et al, 2014;Miller et al, 1999;Zhao et al, 2009). The Nd-isotope model ages (T DM ) of the Qulong adakites range from 0.62 to 0.71 Ga (Table 4).…”