Episodic Crustal Extension and Contraction Characterizing the Late Mesozoic Tectonics of East China: Evidence From the Jiaodong Peninsula, East China

摘要

During the Late Mesozoic, East China is characterized by widespread magmatism, thrusting and folding, extensional doming, strike-slip faulting, and block rotation. The Jiaodong Peninsula provides a key area located in East China to understand the episodic intracontinental extension and contraction and associated granitoid emplacement. Based on our structural analysis, magnetic fabric measurement, and gravity modeling, polyphase deformation and magma emplacement have been recognized within the Queshan-Kunyushan-Yuangezhuang-Sanfoshan (QKYS) massif of the central Jiaodong Peninsula. A significant Late Jurassic D-1 event, developed in the northern margin of the massif, was expressed by a high-temperature, top-to-the-NE shearing. Late Jurassic plutons display magnetic fabrics corresponding to the D-1 structural fabrics and several NW-SE-trending feeder zones at depth. These results link the syn-kinematic emplacement of Late Jurassic plutons with regional NE-SW extensional tectonics. In the south of the massif, a lower-temperature, top-to-the-SW contractional deformation (D-2) resulted from NE-SW contraction. The D-3 shear zone with a top-to-the-WNW kinematics is a rolling-hinge type detachment fault that exhumed the massif, indicating NW-SE regional extension. Finally, Early Cretaceous plutons emplaced into the upper crust with a fast-cooling rate and formed inverted drop shapes with concentric magnetic foliations and variably oriented magnetic lineations. In light of the previous geochronological results, the timing of these tectonic events is discussed. The tectonic evolution of the QKYS massif indicates a process from crustal thickening to lithospheric foundering in response to the Late Mesozoic plate convergences.