Geochemistry of Mesozoic mafic volcanic rocks from the Yanshan belt in the northern margin of the North China Block: relations with post-collisional lithospheric extension

Abstract

Major element, trace element and Sr–Nd isotope data for three suites of mafic volcanic rocks that erupted at c. 180 Ma (Group 1), c. 163–140 Ma (Group 2) and 136–110 Ma (Group 3) in the Yanshan belt in the northern margin of the North China Block (NCB) are presented in this paper. All the rocks show significant enrichment in large ion lithophile elements and light REE (LREE) but depletion in Nb–Ta and Th–U, and moderately radiogenic Sr (87Sr/86Sr(i)= 0.7052–0.7068) and unradiogenic Nd (εNd(t)=−15.1 to −7.2) isotopic compositions. Sr–Nd isotopic modelling suggests an insignificant role of crustal contamination or assimilation fractional crystallization, and the geochemical variations in these rocks were mainly attributed to source heterogeneity and variable degrees of ferromagnesian, plagioclase and accessory mineral fractionation. The low Th/La (0.039-0.10) points to recycling of low-Th/La (e.g. Th/La <0.2) ancient crustal materials into the source region, probably related to the palaeo-Asian Ocean subduction. Compared with the late Mesozoic mafic rocks from the NCB interior, the Yanshan belt mafic lavas generally have higher Al2O3, TiO2, P2O5, LREE, high field strength elements, Sr and 87Sr/86Sr(i) but lower MgO and compatible elements. Major element extrapolation (MgO=8% normalization) reveals that the Yanshan belt mafic volcanic rocks have higher Ti8 and Fe8, and lower Si8 than those from the NCB interior, suggesting that they were probably derived from a relatively fertile mantle source, different from the Mesozoic chemically refractory lithospheric mantle beneath the NCB interior. Combining the geochemical features of the mafic rocks with Mesozoic deformation events in the northern NCB, we suggest that the three stages of mafic volcanism were caused by episodic lithospheric extension. The Group 1 rocks, which occur locally along major faults, were generated during a post-compressional extension related to the collision between the NCB and Mongolian Block; the Group 2 rocks formed as a result of post-collisional lithospheric extension related to the collision between the North China–Mongolian Block and the Siberian plate; and the Group 3 rocks were extruded in an extensional regime in response to lateral escape related to surrounding plate interactions.

Late Jurassic‐Early Cretaceous Deformation in the Western Yanshan Fold‐Thrust Belt: Insights From Syntectonic Sedimentation in the Chicheng Basin, North China

“…Great debate exists in previous papers about the nature of the regional tectonics in the Yanshan belt during the formation of the late Mesozoic basins. Some authors insisted that the Chicheng basin represents a typical rift basin in an extensional setting during the Late Jurassic‐Early Cretaceous period based on the geochemical characteristics of the volcanic interlayers (Guo et al, ; Qi et al, ; Shao et al, ). However, other authors proposed that the formation and development of the Chicheng basin occurred in response to compressional tectonics based on sedimentary analyses of the basin fill (Liu et al, , ; Zhao, ).…”

Field relation, geochemistry and origin of the Xinglonggou volcanic rocks in Beipiao area, Liaoning Province (China): Reappraisal on the foundering of lower continental crust of North China Craton

“…This feature is distinguished from those of Mesozoic igneous rocks in the North China Craton (e.g. Chen and Chen, 1997;Fan et al, 2007;Guo et al, 2007) …”

“…12 and 13). Compared with other Mesozoic igneous rocks of the North China Craton, the Xinglonggou volcanic rocks exhibit young and immature characteristics of radiogenic isotopes similar to those of the Late Paleozoic-Mesozoic igneous rocks of the Xing'an-Inner Mongolia Orogenic Belt (Chen and Chen, 1997;Jahn et al, 1999;Wu et al, 2002;Jahn, 2004;Gao et al, 2005;Fan et al, 2007;Guo et al, 2007;Huang et al, 2007). Consequently, it is inferred that the source of the Xinglonggou volcanic rocks is different from those of the Mesozoic igneous rocks of the North China Craton (Figs.…”

“…As a useful ''petrological tool'' deciphering the deep dynamic process, the high-magnesium igneous rocks had attracted considerable attention over the last decade (e.g. Griffin et al, 1998;Zhang et al, 2003Zhang et al, , 2004Gao et al, 2004Gao et al, , 2008Xu et al, 2004;Chen et al, 2007;Fan et al, 2007;Guo et al, 2007;Zhang, 2007). Among these rocks, the Xinglonggou volcanic rocks occurred in western Liaoning Province, the NE part of North China Craton are the only known samples that formed in early or middle Jurassic (Chen and Chen, 1997;Gao et al, 2004).…”

Implications of subduction and subduction zone migration of the Paleo-Pacific Plate beneath eastern North China, based on distribution, geochronology, and geochemistry of Late Mesozoic volcanic rocks

“…The models include delamination of lower crust and mantle (Deng et al 1996;Gao et al 1998Gao et al , 2004Qian et al 2003;Wu et al 2005;Huang et al 2007;Zhai et al 2007;Yang and Li 2008), thermo-tectonic destruction of a lithospheric root (Menzies et al 1993;Menzies and Xu 1998;Griffin et al 1998;Xu 2001), hydrolytic weakening of subcontinental lithosphere (Niu 2005(Niu , 2006, and thinning associated with intracontinental rifting and continental marginal rifting (Ren et al 2002). There are also many different proposals for tectonic forces that might have driven the thinning process: a global-scale mantle superplume (Jahn et al 1999;Wilde et al 2003), subduction of continental lithosphere at the southern boundary of the NCC during collision between South China and North China (Menzies and Xu 1998;Gao et al 2002), subduction of continental lithosphere at the northern boundary of the NCC during collision between Siberia and the NCC (Meng 2003;Wang et al 2006a;Guo et al 2007), and a combination of northward and southward subduction and collision at both boundaries (Zhang et al 2003;Zhai et al 2007). None of these theories explain all the data (Wu et al 2008).…”