Late Cretaceous adakitic and A-type granitoids in Chanang, southern Tibet: Implications for Neo-Tethyan slab rollback

Abstract

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Two episodes of Eocene mafic magmatism in the southern Lhasa terrane imply an eastward propagation of slab breakoff

“…The cover sequence of the southern Lhasa terrane is made up of the early Jurassic Yeba Formation's bimodal magmatic assemblage (Wei et al, 2017), the late Jurassic-early Cretaceous Sangri group's high Sr/Y andesite (Zhu et al, 2009), and the Paleogene Linzizong volcanic sequence (69-44 Ma) (Zhao et al, 2009;Liu et al, 2014). Five magmatic episodes in southern Tibet have been identified, each preserving a distinct geodynamic evolutionary stage; their ages are 366-252 Ma (Wang et al, 2020), 220-145 Ma (Wei et al, 2020), 120-66 Ma (Wang et al, 2021;Meng et al, 2020), 68-40 Ma (Zhu et al, 2017) and 33-8 Ma (Hou et al, 2004;Zhu et al, 2009;Wang et al, 2014Wang et al, , 2020. They likely reflect activity driven, in sequence, by Paleo-Tethyan Ocean subduction, early and late Neo-Tethyan subduction, India-Asia collision, and post-collisional evolution.…”

Late Cretaceous‐Palaeocene arc magmatism in Bumeicun, Gangdese, southern Tibet: Products of slab rollback of Neo‐Tethyan Ocean?

“…Dominant views point out that a pulse of heat anomaly is caused by the detachment of relic Neo‐Tethyan oceanic crust from the Indian continent, which becomes the driving force of the P‐E magmatism blast (Ji et al, 2016; Kohn & Parkinson, 2002; Yin & Harrison, 2000). Furthermore, various models have been proposed for the petrogenesis and geodynamic background of this period, including: plate subduction leading to partial melting of thickened lower crust (Wen et al, 2008), partial melting of oceanic subduction plates (Jiang et al, 2012, 2014; Wang et al, 2021), mid‐ocean ridge subduction (Zhang et al, 2022; Zheng et al, 2014) or plate rollback leading to asthenosphere upwelling and subsequent magma ‘flare‐up’ (Ma, Wang, Wyman, Jiang, et al, 2013; Meng et al, 2019; Wang, Richards, Hou, et al, 2015; Zhu et al, 2015). These models have their own rationality, but still need more geological evidence to test.…”

“…Numerous recent studies have supported the slab rollback model. They attributed the production of mafic rocks, I‐type granite, A2‐type granite, high‐Mg or low‐Mg adakitic magma to the thermal anomaly caused by slab rollback, which will trigger the partial melting of asthenosphere mantle, oceanic slab, juvenile crustal materials or thickened lower crust (Ji et al, 2019; Lu et al, 2022; Schlunegger & Kissling, 2015; Wang et al, 2021; Xu et al, 2019). However, the specific starting time still needs to be determined accurately.…”