Welcome to visit Geoscience!

Geoscience ›› 2021, Vol. 35 ›› Issue (03): 776-786.DOI: 10.19657/j.geoscience.1000-8527.2021.060

• Petrology • Previous Articles     Next Articles

Sinistral Ductile Shear and Magmatic Migration Pattern in the Late Mesozoic Yishu Fault Zone

LI Sheng1,2(), NI Jinlong1,2(), ZHANG Shangkun3, SHEN Ying3   

  1. 1. College of Geological Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
    2. Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology, Qingdao, Shandong 266237, China
    3. Shandong Institute of Geological Sciences, Jinan, Shandong 250013, China
  • Received:2020-11-19 Revised:2021-04-23 Online:2021-06-23 Published:2021-06-24
  • Contact: NI Jinlong

Abstract:

Magma intrusion in the Yishu fault zone (YFZ) is closely related to fault activity, and the magmatic geochronology in the Yishu fault zone is of major significance for revealing the tectonic setting of the YFZ. Petrological and LA-ICP MS zircon U-Pb geochronological analyses were conducted on the Fulaishan syenite (in Juxian) in the Yishu fault zone, as well as the Guanfang quartz syenite (in Junan) and the intruding diorite porphyrite dykes. The sinistral ductile shearing of the Late Mesozoic YFZ was first recognized. Zircon U-Pb dating yielded (125.1±1.7) Ma (Fulaishan pluton), (125.6±2.0) Ma (Guanfang pluton), and (122.8±2.1) Ma (ductile-deformed diorite porphyrite dyke). The 125 Ma magmatic age obtained is consistent with the rapid exhumation (122-128 Ma) of the Wulian metamorphic core complex (MCC) and the rapid sedimentation in the Zhucheng fault-bounded basin on the eastern side of the YFZ. This indicates that the YFZ was in a period of intense lithospheric thinning and destruction. The 122.8 Ma age of the diorite porphyrite dike is consistent with the crystallization age of the post-Wulian MCC (e.g., Shichang and Fangzi plutons), indicating that the extension of the YFZ was significantly weakened during this period. It also shows the similar timing of lithospheric thinning across the Jiaodong Peninsula. During the Late Mesozoic, magmatism on both sides of the YFZ had a counterclockwise migration pattern, which may have related to the changing direction, angle, and/or velocity of the Izanagi plate subduction beneath the Eurasian plate.

Key words: Yishu fault zone, Fulaishan intrusion, Guanfang intrusion, Late Mesozoic, zircon U-Pb dating

CLC Number: