Geochemical Evidence for Thickening and Thinning of Lower Crust beneath the Jiaodong Peninsula: Implications for Late Mesozoic Destruction of the Eastern North China Craton

Abstract

The eastern North China Craton (NCC) has been recognised as undergoing cratonic destruction during the Mesozoic; however, the mechanism of its destruction is still unclear. The main difference between the proposed models is whether the lower continental crust (LCC) underwent thinning. In this study, we conducted comprehensive analyses of Late Mesozoic felsic intrusive rocks, including Late Jurassic granites (166–146 Ma), Early Cretaceous granodiorites (136–123 Ma), and latest Early Cretaceous granites (123–108 Ma) from the Jiaodong Peninsula, located on the southeastern margin of the NCC. These rocks allowed us to investigate variations in the LCC thickness in this region and to further discuss the destruction mechanism of the eastern NCC. Here, temporal variations in crustal thickness can be tracked using whole-rock La/Yb ratios of the felsic intrusive rocks. Our study shows that the continental crust in the eastern NCC thickened during the Late Jurassic (>40 km) due to compression and the westward subduction of the Palaeo-Pacific Ocean lithosphere beneath the NCC since the Early Jurassic. The continental crust further thickened during the Early Cretaceous, caused by the steepening of the subducting slab after ~144 Ma that produced crustal underplating of mantle-derived melts in an extensional setting. However, the continental crust thinned (20–40 km) during the latest Early Cretaceous, caused by the rollback of the subducting slab after ~123 Ma. The geochemical compositions of three stages of felsic intrusions also suggest that the regional tectonic stress that affects the eastern NCC altered from a compressional to an intraplate extensional environment after ~144 Ma. Thus, the Late Mesozoic destruction of the eastern NCC and its accompanying magmatism were controlled by prolonged thermomechanical-chemical erosion due to low-angle subduction, steepening, and rollback of the Palaeo-Pacific Oceanic lithosphere.

The Formation of the Jiaodong Gold Province

“…The La/Yb and Sr/Y ratios, indicator of crustal thickness, of intermediate Mesozoic rocks proves the crustal thinning in Jiaodong Peninsula during the metallogenic period (Chapman et al, 2015;Zhao et al, 2016;Liang et al, 2020). The Late Jurassic Linglong granites (166-146 Ma) and the Early Cretaceous Guojialing granodiorites in Jiaodong exhibit adakitic characteristics, including high Sr/Y ratios (20.4-378, average of 126) and La/Yb ratios (7.48-206, average of 77.7; Zhao et al, 2016;Liang et al, 2020), which suggest a thickened continent crust (>40 km; ~1.2 GPa; Rapp et al, 2003). In contrast, the latest Early Cretaceous granites (123-108 Ma) exhibit lower Sr/Y (0.27-108, average of 25.3) and La/Yb (2.…”

“…In contrast, the latest Early Cretaceous granites (123-108 Ma) exhibit lower Sr/Y (0.27-108, average of 25.3) and La/Yb (2. 59-176, average of 38.7;Liang et al, 2020) ratios as compared to the earlier two magmatic stages in the Jiaodong. This indicates a crustal thickness of 20-40 km, corresponding to 0.8-1.2 GPa (Alonso-Perez et al, 2009;Zou et al, 2019).…”

“…This process resulted in the replacement of Paleozoic lithosphere, which was thick (>180 km), cold (40 mW/m 2 ), and stable, by the Cenozoic- Data sources (age of gold deposits): Li et al, 2003Li et al, , 2006Zhang et al, 2003;Li et al, 2008. Present lithosphere that is thin (<100 km) and hot (65 mW/ m 2 ) (Gao et al, 2002(Gao et al, , 2008Xu et al, 2004;Goldfarb et al, 2007;Zhang, 2012;Zhu et al, 2017;Li et al, 2019c). The La/Yb and Sr/Y ratios, indicator of crustal thickness, of intermediate Mesozoic rocks proves the crustal thinning in Jiaodong Peninsula during the metallogenic period (Chapman et al, 2015;Zhao et al, 2016;Liang et al, 2020). The Late Jurassic Linglong granites (166-146 Ma) and the Early Cretaceous Guojialing granodiorites in Jiaodong exhibit adakitic characteristics, including high Sr/Y ratios (20.4-378, average of 126) and La/Yb ratios (7.48-206, average of 77.7; Zhao et al, 2016;Liang et al, 2020), which suggest a thickened continent crust (>40 km; ~1.2 GPa; Rapp et al, 2003).…”

“…subcontinental lithospheric mantle and devolatilization at ~120 Ma (Cai et al, 2013(Cai et al, , 2015Ma et al, 2014a, b;Deng et al, 2017). Simultaneously, crustal thinning took place in the Jiaodong Peninsula (Zhu et al, 2017;Li et al, 2019c;Liang et al, 2020).…”

Petrogenesis of Mesozoic Magmatic Suites in the Jiaodong Peninsula: Implications for Crust-Mantle Interactions and Decratonization

“…The Mesozoic magmatic rocks in the Jiaodong Peninsula include the Jurassic Linglong biotite granite, Early Cretaceous Guojialing granodiorite, and Aishan granite porphyry (Figure 1). Extensive studies have been conducted to investigate their petrogenesis and to constrain the NCC decratonization [11,[16][17][18][19]. The Linglong granite is suggested to be derived from the melting of thickened Archean lower crust [17,19] with no significant mantle contribution [20], while the genesis of the Early Cretaceous Guojialing granodiorite is still disputed [17,19].…”