Westward-younging high-Mg adakitic magmatism in central Tibet: Record of a westward-migrating lithospheric foundering beneath the Lhasa–Qiangtang collision zone during the Late Cretaceous

Quantitatively Tracking the Elevation of the Tibetan Plateau Since the Cretaceous: Insights From Whole‐Rock Sr/Y and La/Yb Ratios

“…Earlier uplift of the Northern Lhasa terrane relative to the Central Lhasa terrane is corroborated by sedimentological studies (DeCelles et al, 2007; Kapp, DeCelles, Gehrels, et al, 2007; Lai, Hu, Garzanti, Sun, et al, 2019), and paleocurrent data support a higher elevation of the Lhasa terrane relative to the Qiangtang terrane during this stage (Figure 4; Lai, Hu, Garzanti, Sun, et al, 2019). High‐pressure adakitic rocks derived from the lower crust also support thickened crust during the early Late Cretaceous (Sun, Hu, et al, 2015; Yi et al, 2018). Tectonic shortening/thrusting indicates the upper crust was thickened significantly during the Late Cretaceous (DeCelles et al, 2007; Kapp, DeCelles, Gehrels, et al, 2007), which supports the concept of the Northern Lhasaplano (Figure 4; Lai, Hu, Garzanti, Sun, et al, 2019; Murphy et al, 1997; Wang et al, 2020).…”

“…Geochemical data for Cretaceous to recent magmatic rocks in the TP were obtained from the Tibetan Magmatism Database (Table S6; Chapman & Kapp, 2017). Following previous authors (Yi et al, 2018; Zhu et al, 2019), we subdivided the Qiangtang and Lhasa terranes into five subterranes, including the Northern Qiangtang, Southern Qiangtang, Northern Lhasa, Central Lhasa, and Southern Lhasa terranes and investigate the paleo‐elevation history of each separately (Figure 2). Because of the distinct tectonic settings of different terranes during different time periods, subduction‐related and collision‐related equations were applied for each terrane according to specific circumstances (see Table S7).…”

Formation of Late Cretaceoushigh‐Mggranitoid porphyry in central Lhasa, Tibet: Implications for crustal thickening prior to India–Asia collision

“…Consequently, the Sebuta adakitic porphyry was more likely generated by partial melting of delaminated lower crust. Furthermore, previous studies attributed coexistence of coeval lower crust‐derived high‐Mg # and low‐Mg # melts to occurrence of delamination (Karsli et al, 2010; Sun, Hu, Zhu, et al, 2015; Yi et al, 2018). This is because, if the melts were derived from partial melting of a delaminated lower crust, they would inevitably interact with the overlying mantle peridotite thus generating high‐Mg # adakitic rocks.…”

“…(a) Tectonic map of China, showing the location of Tibet (modified after Cao, Zhang, Santosh, et al, 2019); (b) the tectonic subdivision of the Tibet Plateau, showing the major sutures and terranes (modified after Pan et al, 2012; Yin & Harrison, 2000). Ages are compiled from Cao, Zhang, Santosh, et al (2019), Chen, Xu, et al (2015), Liu, Wang, et al (2018), Luo et al (2019), Sun, Hu, Zhu, et al (2015), Wang et al (2014, 2019), Yi et al (2018) and Yu et al (2011) [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…However, the petrogenesis and tectonic settings of the Cretaceous magmatism in the central‐northern Lhasa block remain equivocal, with diverse models including the northward subduction of the Neo‐Tethyan Ocean lithosphere (Ma & Yue, 2010; Zhang et al, 2012; Zheng, Huang, Cai, et al, 2019), the southward subduction of the Bangong–Nujiang Ocean (Meso‐Tethyan Ocean) lithosphere and subsequent Lhasa–Qiangtang collision (Li et al, 2018; Mo et al, 2005; Pan, Mo, Hou, et al, 2006; Zhu et al, 2013; Zhu, Mo, Niu, et al, 2009a). Recently, delamination of a thickened lithospheric keel (including lithospheric mantle and lowermost crust) has also been proposed to account for the Late Cretaceous magmatism within the Lhasa–Qiangtang collision zone (Cao, Zhang, Santosh, et al, 2019; Chen et al, 2015; Wang, Tang, Wang, et al, 2019; Wang, Zhu, Zhao, et al, 2014; Yi et al, 2018; Yu, Chen, Xu, et al, 2011).…”