Assembly of the Lhasa and Qiangtang terranes in central Tibet by divergent double subduction

Abstract

Integration of lithostratigraphic, magmatic, and metamorphic data from the LhasaQiangtang collision zone in central Tibet (including the Bangong suture zone and adjacent regions of the Lhasa and Qiangtang terranes) indicates assembly through divergent double sided subduction. This collision zone is characterized by the absence of Early Cretaceous high-grade metamorphic rocks and the presence of extensive magmatism with enhanced mantle contributions at ca. 120110 Ma. Two JurassicCretaceous magmatic arcs are identified from the CaimaDuobuzaRongmaKangqiongAmdo magmatic belt in the western Qiangtang Terrane and from the Along TsoYanhuDaguoBaingoinDaru Tso magmatic belt in the northern Lhasa Terrane. These two magmatic arcs reflect northward and southward subduction of the Bangong Ocean lithosphere, respectively. Available multidisciplinary data reconcile that the Bangong Ocean may have closed during the Late JurassicEarly Cretaceous (most likely ca. 140130 Ma)through arc-arc "soft" collision rather than continent-continent "hard" collision.Subduction zone retreat associated with convergence beneath the Lhasa Terrane may have driven its rifting and separation from the northern margin of Gondwana leading to its accretion within Asia.

Underplating of basaltic magmas and crustal growth in a continental arc: Evidence from Late Mesozoic intermediate–felsic intrusive rocks in southern Qiangtang, central Tibet

“…In the present study, taking into account ophiolites in the BangongNujiang Suture (Bao et al, 2007;Zhang et al, 2014a;Zhu et al, 2006b) and the nature of Late Mesozoic magmatic rocks (e.g., Kapp et al, 2005;Li et al, 2014a,b;Liu et al, 2012Liu et al, , 2014Sui et al, 2013;Zhu et al, 2009Zhu et al, , 2016; this study) in southern Qiangtang and central and northern Lhasa sub-blocks, we suggest that both southern Qiangtang and central and northern Lhasa sub-blocks were located in continental arc settings related to bidirectional subduction of the Bangong-Nujiang oceanic basin as outlined above (Zhu et al, 2016; this study).…”

“…The bidirectional subduction of the Bangong-Nujiang Ocean has recently been suggested (Xu et al, 2014;Zhang, 2007;Zhu et al, 2016), and such a scenario can better account for the twin magmatic flare ups if slab break-off events did not occur. We suggest that, during Late Mesozoic, the Bangong-Nujiang oceanic basin most probably subducted both northward under southern Qiangtang and southward under central and northern Lhasa, respectively (Fig.…”

Evolution of the Bangong–Nujiang Tethyan ocean: Insights from the geochronology and geochemistry of mafic rocks within ophiolites

“…1a) (Pan et al, 2012(Pan et al, , 2013Zhang et al, 2012;Zhu et al, 2012Zhu et al, , 2013Zhu et al, , 2015Wang et al, 2013). The Qiangtang terrane is bound by the Jinsha suture to the north and the Bangong-Nujiang suture to the south (Fig.…”

“…The BNSZ extends for >2000 km from Bangong in the west to Nujiang in the east, and it forms the boundary between the NLT and SQT (Girardeau et al, 1984;BGMR, 1993;Pan et al, 2013;Wang et al, 2013;Zhu et al, 2013Zhu et al, , 2015. The suture is considered to represent the Tethyan Ocean.…”

“…subduction of the BNTO (Qu et al, 2009;She et al, 2009;Du et al, 2011;Li et al, 2014aLi et al, , 2014bLi et al, , 2014cLiu et al, 2014a;Zhu et al, 2015). Meanwhile, Early…”