An Andean‐type arc transferred into a Japanese‐type arc at final closure stage of the Palaeo‐Asian Ocean in the southernmost of Altaïds

Abstract

Permian progressive accretion or continental rift is a long‐term debate topic in the final evolution of the Altaïds or the Central Asian Orogenic Belt (CAOB). The Beishan orogenic collage in the southernmost part of the CAOB recorded the ultimate closure of the Palaeo‐Asian Ocean. In this paper, we present (a) field structural measurements/data or observations and fold geological maps in the Liuyuan Basin, (b) geochronological results to rocks on the Shibanshan arc and in the Liuyuan Basin, and (c) geochronological and regional geological data collected around the Liuyuan area, in order to investigate the tectonic setting and evolution of the Liuyuan Basin, and finally discuss the termination of the Palaeo‐Asian Ocean. We notice that (a) rocks cropping out on both sides of the Liuyuan Basin have similar petrological and geochronological feature, which are probably from one ancient terrane, (b) sediments and volcanic rocks in the Liuyuan Basin formed in an arc‐related basin within an extensional deep to semi‐deep water setting or in a limited oceanic basin, and (c) at least two stages of folding could be recognized in the Liuyuan Basin; the age of this progressive deformation was constrained by the maximum depositional age of basinal sediments and undeformed or weakly deformed stitching plutons, which is variable from 275 to 217 Ma; orogenesis therefore was related to arc‐related accretion rather than a rift open‐close process in Late Permian to Early Triassic. Finally, we conclude that (a) the Liuyuan Basin is a back‐arc basin, not a rift basin or lake, (b) final closure of the Palaeo‐Asian Ocean was from Late Permian to Triassic, and (3) an Andean‐type arc transferred into a Japanese‐type arc at the final closure of the Palaeo‐Asian Ocean in the southernmost part of the CAOB. Last but not the least, we further speculate that eclogites developed in the Shibanshan arc were emplaced to the Beishan orogenic collage via a destroyed back‐arc basin.

Permian back‐arc basin formation and arc migration in the southern Central Asian Orogenic Belt, Northwest China

“…The presence of these distinct arcs is inconsistent with the model of Tian and Xiao (2020), where the Liuyuan Complex formed as the Shibanshan arc rifted from its Dunhuang block basement.…”

“…Alternatively, Wang et al (2017) proposed the Liuyuan Complex is an intra-continental magmatic suite emplaced into the already amalgamated CAOB, with the lavas being the eruptive LIP facies, and the plutonic rocks representing a layered intrusion. Recently, Tian and Xiao (2020)…”

Origins of the meta‐mafic rocks in the southern Dunhuang Block (NW China): Implication for tectonic framework of the southernmost Central Asian Orogenic Belt

“…The southernmost unit of the Beishan Orogen is the Shibanshan terrain. Some researchers regarded the Shibanshan terrain is a continental arc along the northern margin of the Dunhuang Block formed by the southward subduction of the PAO (Xiao et al, 2010; Zuo, Zhang, He, & Zhang, 1991), which developed at least by the beginning of Late Cambrian to Early Ordovician (Tian & Xiao, 2019). And some other people considered it as a Mesoproterozoic microcontinent amalgamated in the Beishan Orogen (He, Klemd, Yan, & Zhang, 2018; He, Sun, Mao, Zong, & Zhang, 2015; He, Zong, Jiang, Xiang, & Zhang, 2014; Jiang, He, Zong, Zhang, & Zhao, 2013; Yuan et al, 2015).…”

The Dashui Subduction Complex in the Eastern Tianshan‐Beishan Orogen (NW China): Long‐Lasting Subduction‐Accretion Terminated by Unique Mid‐Triassic Strike‐Slip Juxtaposition of Arcs in the Southern Altaids

“…The Shibanshan Arc consists of Meso‐to Neoproterozoic metamorphic rocks (He, Sun, et al., 2015; Jiang et al., 2013; Song et al., 2016; Yuan et al., 2015, 2019; Zong et al., 2017), Paleozoic magmatic rocks (Wang et al., 2016; W. Zhang et al., 2011; Zhang, Pease, et al., 2015), and Devonian to Permian sedimentary rocks (Niu et al., 2018b, 2018c; Xu et al., 2018). These rocks are considered to belong to a Paleozoic magmatic arc situated on the northern margin of the Dunhuang block (Tian & Xiao, 2019; Xiao, Mao, et al., 2010; Zheng et al., 2020).…”