The Xiaoqinling metamorphic core complex: A record of Early Cretaceous backarc extension along the southern part of the North China Craton

Abstract

Many metamorphic core complexes (MCCs) of Early Cretaceous age are documented in the northern part of the North China Craton (NCC), which formed in a backarc extensional setting. However, whether or not the MCCs are also present in the southern part of the NCC, and where the western boundary of backarc extension lies, remain unclear. We present new structural and geochronological data to show that Early Cretaceous structures in the Xiaoqinling region (China) lying in the southern part of the central NCC represent a Cordilleran-type MCC. The NW-dipping detachment zone on the northwestern edge of the Xiaoqinling MCC is a ductile extensional shear zone that is overprinted by a later brittle detachment fault. The footwall (lower plate) consists of Archean metamorphic rocks and Mesozoic plutonic rocks, and was cut by a series of ductile normal sense shear belts and later brittle normal faults that strike predominantly NE-SW. Both the ductile and brittle structures indicate that NW-SE extension was responsible for the development of the MCC. Geochronological data suggest that the MCC initiated at 138 Ma and lasted until 100 Ma, recording a protracted extensional history. The MCC experienced an early phase of crustal-scale normal faulting (138–126 Ma) and later isostatic doming (125–100 Ma), consistent with the “rolling-hinge” model. The Xiaoqinling MCC shows similar features and a similar evolution to other intraplate MCCs in the northern and southeastern parts of the NCC, and shows that the southern part of the NCC was also involved in intense backarc extension and magmatism. Distribution of these intraplate MCCs indicates synchronous backarc extension over a length of around 1800 km. Delamination of a flat oceanic slab during roll-back is consistent with such large-scale, synchronous extension in the overriding plate.

Relations between earthquake distributions, geological history, tectonics and rheology on the continents

“…They were particularly influenced by the North China 'craton', an area with Precambrian rocks at the surface that currently has thin lithosphere, although Ordovician mantle nodules show that it was thick in the Palaeozoic. The explanation is now likely to be that the area stretched dramatically in the Tertiary [85], with some of the extension still active in a graben system today [86], rather than the mantle lithosphere delaminating.…”

Origin of Low‐Angle Ductile/Brittle Detachments: Examples From the Cretaceous Linglong Metamorphic Core Complex in Eastern China

“…Many studies have demonstrated widespread extension and magmatism as well as lithospheric thinning of ~100 km in the eastern NCC during the Early Cretaceous (Li et al, 2020; Lin et al, 2014; Liu et al, 2013; Wu, Xu, et al, 2014; Zhu et al, 2012, 2015). The results of these processes are collectively referred to as craton destruction, and they are considered to have taken place in a back‐arc extensional setting related to rollback of the subducted Paleo‐Pacific Plate (Wu, Xu, et al, 2014; Zhu et al, 2012, 2018; Zhu, Zhang, et al, 2017).…”

“…Extension produced a series of rift basins (Zhu et al, 2012) as well as many MCCs in the eastern NCC (Figure 1). Early Cretaceous MCCs include those at Hohhot (Davis et al, 2002; Guo et al, 2012), Yunmengshan (Davis et al, 1996; Zhu et al, 2015), Kalaqin (Lin et al, 2014), Waziyu (Zhang et al, 2012), Wanfu (Liu et al, 2013), Liaonan (Liu et al, 2005), Xiaoqinling (Li et al, 2020), Fangshan (Sun et al, 2010), and Linglong (Lin et al, 2013). The Sulu Orogen contains the synchronous Wulian (Ni et al, 2013) and Queshan (Xia et al, 2016) MCCs.…”

“…Outline tectonic map of eastern China showing metamorphic core complexes (MCCs) of Early Cretaceous age in the North China Craton. HH = Hohhot MCC (Davis et al, 2002; Guo et al, 2012); XQ = Xiaoqinling MCC (Li et al, 2020); YM = Yunmengshan MCC (Davis et al, 1996; Zhu et al, 2015); KQ = Kalaqin MCC (Lin et al, 2014); WZ = Waziyu MCC (Zhang et al, 2012); WF = Wanfu MCC (Liu et al, 2013); LN = Liaonan MCC (Liu et al, 2005); QS = Queshan MCC (Xia et al, 2016); WL = Wulian MCC (Ni et al, 2013); FS = Fangshan MCC (Sun et al, 2010); LL = Linglong MCC (this study).…”

Late Cretaceous geodynamics of the Palaeo‐Pacific plate inferred from basin inversion structures in the Songliao Basin (NE China)

“…The Mesozoic–Cenozoic tectonic history of the region surrounding the basin has been controlled mainly by subduction of the Palaeo‐Pacific plate (e.g. Dong et al, 2015; Kong et al, 2020; Li et al, 2012; Li, Zhu, et al, 2019; Pang et al, 2014; Xu et al, 2018). During subduction, eastern Asia underwent shortening that generated coeval arc magmatism and NE‐striking fold–thrust belts (e.g.…”