Extensional tectonics and North China Craton destruction: Insights from the magnetic susceptibility anisotropy (AMS) of granite and metamorphic core complex

Abstract

The craton is a long-lived stable geologic unit on the Earth's surface. However, since the Mesozoic, the North China Craton (NCC) experienced large-scale lithospheric removal, the fundamental change of physical and chemical characteristics of the lithospheric mantle, widely distributed crustal deformation, and extensive magmatism. This complex evolution contrary to other cratons is called the NCC destruction. Widespread magmatism in the eastern NCC is an important response to the lithospheric removal at depth and crustal deformation on the surface. The plutons emplace under a tectonic context and therefore record the information of the tectonics; especially, the anisotropy magnetic susceptibility (AMS) pattern of the pluton was acquired with the influence of regional stress. In the past fifteen years, about 22 plutons intruding during the different periods from the Late Triassic to the late stage of the Early Cretaceous have been studied with AMS. The emplacement mechanisms of plutons and the contemporary tectonic setting were discussed to constrain their relationship with the NCC destruction in different stages of magmatism. As a result, the Late Triassic, Early Jurassic, and Late Jurassic plutons exhibit consistent N(E)-S(W) trending magnetic lineations. The early stage of Early Cretaceous plutons display NW-SE trending magnetic lineations, while the late stage of Early Cretaceous plutons show magnetic lineations with various orientations. Combined with previous studies, it is concluded that the emplacements of the plutons intruding in these three stages were controlled by weak N(E)-S(W) trending extension, regional NW-SE trending extension, and weak extension in the shallow crustal level, respectively. The transformation of regional extension from the N(E)-S(W) to the NW-SE direction was accompanied by a strain-increasing tendency. The extensional tectonics in the eastern NCC was interpreted to represent the interaction between Mongol-Okhotsk belt, Paleo-Pacific plate, and eastern Eurasian continent.

Basal Décollement Splaying Induces Mid‐Crustal Tectonic Imbrication in an Intracontinental Orogen

“…The intervening granitic blocks and Late Jurassic monzonitic pluton are visibly undeformed. Our AMS results of the NJB also attest to the magmatic texture by structural observation of the granites (Figures 5a and 5b), exhibiting a concentric pattern of magnetic foliation and dispersed trending directions of magnetic lineation (Figure 11) that form a doming structure by magma diapirism (Charles et al., 2012; de Oliveira et al., 2010; W. Lin et al., 2021). This pattern is usually considered as a result of magma inflation above the feeder zone, which is supported by the gravity data and modeling results that the deepest root of the Jiuling Batholith is located in the north (Figures 13 and 14).…”

“…The intervening granitic blocks and Late Jurassic monzonitic pluton are visibly undeformed. Our AMS results of the NJB also attest to the magmatic texture by structural observation of the granites (Figures 5a and 5b), exhibiting a concentric pattern of magnetic foliation and dispersed trending directions of magnetic lineation (Figure 11) that form a doming structure by magma diapirism (Charles et al, 2012;de Oliveira et al, 2010;W. Lin et al, 2021).…”

Jurassic–Early Cretaceous tectonic evolution of the North China Craton and Yanshanian intracontinental orogeny in East Asia: New insights from a general review of stratigraphy, structures, and magmatism

“…The syn-tectonic Kunyushan pluton exhibits the margin-parallel gneissic to mylonitic foliation with a locally NE-SW subhorizontal mineral and stretching lineation in its northern margin (Meng and Lin, 2021). The AMS measurement suggests that the syn-emplacement fabrics of these Late Jurassic plutons possess mainly margin-parallel or concentric magnetic foliation patterns, exhibiting a dome-like geometry (Lin et al, 2021; Table 3). The lineations in the plutons exhibit variable orientations and plunges without any correlation with the regional strain (e.g., Paterson, 1989).…”

“…The Early Jurassic regional tectonic information is still not available from the fabrics of the granitic plutons due to overprinting of the fabrics in the Jiumen pluton by the later intrusion of the Jianchang pluton. Nevertheless, considerable effort has been devoted to the fabric study on numerous Late Jurassic plutons in the Yanshan belt and Jiaodong peninsula (Table 3; Lin et al, 2021). Similar to the Jianchang pluton, several contemporaneous granitic plutons are mainly composed of isotropic granite without observable planar and linear fabrics at outcrops (e.g., Siganding pluton, Luanjiahe pluton, and Wendeng pluton; Table 3).…”

“…Similar to the Jianchang pluton, several contemporaneous granitic plutons are mainly composed of isotropic granite without observable planar and linear fabrics at outcrops (e.g., Siganding pluton, Luanjiahe pluton, and Wendeng pluton; Table 3). Several Late Jurassic plutons have been greatly overprinted by the NW-SE directed detachment faulting of the Early Cretaceous MCCs (e.g., the Yiwulüshan, Linglong, and Queshan plutons; Wang, 2013;Lin et al, 2013aLin et al, , 2013bMeng and Lin, 2021;Lin et al, 2021). The syn-tectonic Kunyushan pluton exhibits the margin-parallel gneissic to mylonitic foliation with a locally NE-SW subhorizontal mineral and stretching lineation in its northern margin (Meng and Lin, 2021).…”