Continental origin of the Gubaoquan eclogite and implications for evolution of the Beishan Orogen, Central Asian Orogenic Belt, NW China

Abstract

The Gubaoquan eclogite occurs in the Paleozoic Beishan Orogen of NW China. Previously it has been interpreted as a fragment of subducted oceanic crust that was emplaced as a mélange within continental rocks. Contrary to this, we demonstrate that the Gubaoquan eclogite protolith was a Neoproterozoic basic dyke/sill which intruded into Proterozoic continental rocks. The SHRIMP U-Pb zircon dating of the metamorphic rims of the Gubaoquan eclogite yields an age 466 ± 27 Ma. Subdued heavy rare earth element abundances and lack of negative Eu anomalies of the metamorphic zircon domains confirm that this age represents eclogite facies metamorphism. The host augen orthogneiss has a U-Pb zircon age of 920 ± 14 Ma, representing the timing of crystallization of the granitic protolith. A leucogranitic vein which intrudes the eclogite has a U-Pb zircon age of 424 ± 8.6 Ma. This granitic vein marks the end of high-grade metamorphism in this area. The overcomplication of tectonic history of the Beishan Orogen is partially caused by inconsistent classifications and nomenclature of the same rock units and arbitrary subdivisions of Precambrian blocks as individual microcontinents. In an attempt to resolve this, we propose a simpler model that involves the partial subduction of the northern passive margin of the

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

“…Combined with all the data presented by previous studies, in this study, we present that the Liuyuan Basin is a back-arc basin and that the pillow lavas and its associated rocks such as clastic sediments and limestones formed in a back-arc basin tectonic setting. The following reasons are demonstrated: First, according to the previous geological mapping and combined with geochronology data collected in this paper ( Figure 3 and Table Third, eclogites discovered in the Gubaoquan area have a metamorphic age of 465-467 Ma Qu et al, 2011;Saktura et al, 2017) and with a formation age of 920 Ma (Saktura et al, 2017). In the south of the Liuyuan Basin, although large areas of land were covered by the Quaternary sediments, eclogite was still found in the Hongliuxia area~100 km south of our study area by Wang et al (2016), and it has a metamorphic age of 411 Ma and formation age of 1316 Ma.…”

“…Third, eclogites discovered in the Gubaoquan area have a metamorphic age of 465–467 Ma (Liu et al, 2011; Qu et al, ; Saktura et al, ) and with a formation age of 920 Ma (Saktura et al, ). In the south of the Liuyuan Basin, although large areas of land were covered by the Quaternary sediments, eclogite was still found in the Hongliuxia area ~100 km south of our study area by Wang et al (), and it has a metamorphic age of 411 Ma and formation age of 1316 Ma.…”

Age, depositional environment, and tectonic significance of an Early Neoproterozoic volcano‐sedimentary sequence in the eastern Beishan orogenic belt, southern Central Asian Orogenic Belt

“…1 – Hongshishan mélange, 2 – Xingxingxia‐Shibanjing mélange, 3 – Hongliuhe‐Xichangjing mélange, 4 – Liuyuan mélange. Data: 1 – Yuan et al (2015); 2 – Mei et al (1999); Ye et al (2013); Liu et al (2015); Yuan et al (2015); Saktura et al (2017); Soldner et al (2020); 3 – Jiang, He, Zong, Zhang, and Zhao (2013); 4 – He, Sun, Mao, Zhong, and Zhang (2015); Yuan et al (2019); 5 – Ao et al (2016); 6 – Niu et al (2019) [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…Previous studies have suggested that an extensive Precambrian basement, referred to as the Beishan complex, occurs in the arc terranes of the Beishan orogenic belt, except for the Quershan Terrane (Figure 1b; BGMRGP, 1996; He et al, 2005; Yang et al, 2012; Zuo et al, 1991), but their protolith ages of many so‐called Precambrian rocks are speculative. Although Precambrian ages have been obtained from some rocks by the zircon U–Pb dating (He et al, 2015; Jiang et al, 2013; Liu et al, 2015; Niu et al, 2019; Saktura et al, 2017; Soldner et al, 2020; Ye et al, 2013; Yuan et al, 2015, 2019), many of the rocks previous thought to be Precambrian are actually Palaeozoic in age (Song et al, 2015, 2016; Song, Xiao, Han, Li, et al 2013; Song, Xiao, Han, & Tian, 2013, Song, Xiao, Han, Tian, & Wang, 2013 Zheng, Li, Xiao, & Zhang, 2018).…”

“…To date, the only accurate ages reported for Precambrian rocks in the Shuangyingshan‐Huaniushan Terrane are those for the Gubaoquan granitic and mafic rocks (905–865 Ma; Liu et al, 2015; Saktura et al, 2017; Soldner et al, 2020; Ye et al, 2013; Yuan et al, 2015). Consequently, it is unclear whether this terrane is a Precambrian microcontinental block or not.…”