Temporal variations in the dynamic evolution of an overriding plate: Evidence from the Wulong area in the eastern North China Craton, China

Abstract The evolution of overriding-plate deformation, and the mechanisms responsible for this deformation, are debated. One area where these processes can be investigated is the eastern North China Craton (NCC) in China, which was situated in an overriding-plate position relative to the subducting Paleo-Pacific Plate during the Jurassic and Cretaceous. Here we constrain the structural evolution of the Jurassic and Cretaceous using new structural, stress field, and geochronological data from the Wulong area. The results show that the first phase of deformation (D1) produced a series of SE-dipping reverse shear zones and parallel folds in response to NW-SE shortening at 157–146 Ma (Late Jurassic). Based on microscopic observations and quartz c-axis analysis, it is suggested that the temperature during D1 deformation was 500 ± 50 °C. A second phase of contractional deformation (D2) at 146–132 Ma (earliest Early Cretaceous) gave rise to numerous NE-SW–striking sinistral faults and shear zones. The majority of D2 structures display ductile fabrics in the southwest of the Wulong area and brittle deformational features in the northeast, thus indicating enhanced exhumation in the former area. Microstructures of D2 sinistral shear zones indicate deformation temperatures of 300–400 °C. Inversion of fault slip data from the sinistral faults demonstrate that N-S compression was responsible for the D2 structures. The third phase of deformation (D3) was related to WNW-ESE extension during the middle to late Early Cretaceous (132–100 Ma). This extensional phase produced a series of NE-SW–striking normal faults and reactivated pre-existing structures. Dikes and plutons were emplaced during the D3 deformation, synchronous with the peak destruction of the NCC. Our results indicate that the eastern NCC showed temporal variations in stress and strain during the Jurassic and Cretaceous. Consistent with the slab-driven model, we suggest that this behavior represents the response of the overriding-plate to changes in subduction kinematics.

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

Lithosphere ◽

10.2113/2020/8831664 ◽

2020 ◽

Vol 2020 (1) ◽

Author(s):

YaYun Liang ◽

Wenhui Guo ◽

Yao Ma ◽

Enquan Zhao

Keyword(s):

Continental Crust ◽

Early Cretaceous ◽

North China Craton ◽

Late Jurassic ◽

North China ◽

Temporal Variations ◽

Late Mesozoic ◽

Jiaodong Peninsula ◽

Intrusive Rocks ◽

Subducting Slab

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.

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

Geological Society of America Bulletin ◽

10.1130/b35261.1 ◽

2019 ◽

Vol 132 (3-4) ◽

pp. 617-637 ◽

Cited By ~ 3

Author(s):

Yunjian Li ◽

Guang Zhu ◽

Nan Su ◽

Shiye Xiao ◽

Shuai Zhang ◽

...

Keyword(s):

Early Cretaceous ◽

North China Craton ◽

Large Scale ◽

North China ◽

Normal Faults ◽

Western Boundary ◽

Geochronological Data ◽

The North ◽

Hinge Model ◽

Metamorphic Core

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.

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