牟平-即墨断裂带不仅构成了苏鲁造山带与胶北地块(华北地块)的边界,也是中国东部巨型郯庐走滑断裂系(即郯城-庐江走滑断裂系)的主要组成部分。基于野外断层滑动矢量分析和古构造应力场反演、侵入岩和火山岩锆石U-Pb离子探针和Ar-Ar测年分析,结合海域地球物理资料解释成果,研究了该断裂带平面展布形态和晚中生代构造演化历史。结果表明,牟平-即墨断裂带在晚侏罗世-白垩纪时期经历了挤压左旋平移引张伸展右旋走滑拉分等3个显著不同的运动学转变历史。晚侏罗世是重要的挤压作用时期,沿断裂带发生显著的左旋走滑活动,牟平-即墨断裂带东支桃村-东陡山断裂记录了约30km的左旋错移量。早白垩世时期,构造体制以引张伸展活动为主,引张应力方向为NW-SE至近W-E向,沿断裂带形成一系列深而狭长的断陷盆地;盆地中侵入岩和火山喷发岩锆石U-Pb离子探针和Ar-Ar测试,获得了一致的年龄在106~123Ma。晚白垩世古新世时期,断裂带以右旋走滑活动为主,右旋剪切拉分作用控制了胶县-莱阳伸展断陷盆地的发育,沿断裂带局部凹陷区控制了晚白垩世王氏群沉积。早、晚白垩世之间发生一期构造挤压事件,挤压方向NW-SE,导致断陷盆地构造反转和断裂带左旋走滑活动,但这期走滑位移量不大。牟平即墨断裂带运动学历史和构造应力场演化较完整地记录了中国东部晚中生代构造体制转换过程,并对构造体制转换过程的动力学背景提供了重要的构造地质学制约。
The Muping-Jimo fault zone not only forms the boundary between the Su-Lu (Jiangsu-Shandong)orogenic belt and Jiaobei(north Jiaodong Peninsula)block (North China Block), but also consists of the huge Tancheng-Lujiang left-lateral strike-slip fault system in East China. Based on field analysis of fault slip data and paleostress inversion, zircon SHRIMP and Ar/Ar dating of intrusive and volcanic rocks, and combining with the results of geophysical interpretations in the North Yellow Sea, this paper presents evidences for the distribution and tectonic evolution history of the Muping-Jimo fault. The results show that this fault zone experienced, during the period from the late Jurassic to Cretaceous, three distinct periods of fault motion, characterized by left-slip transpression during the late Jurassic, extension or transtension during the Early Cretaceous and right-slip transtension during the Late Cretaceous and Paleogene. Late Jurassic was an era for important left-lateral strike-slip motion along the Tancheng- Lujiang fault system, which is marked by about 30 km offset along the Taocun-Dongdoushan fault. The tectonic stress regime changed to extension during the Early Cretaceous and the Muping-Jimo fault zone was dominated by normal faulting which resulted in formation of deep and narrow fault-down troughs. The direction of extension during this period was NW-SE to W-E. Dating of granites intruded in the Early Cretaceous Laiyang Group and basalts of the Early Cretaceous Qingshan Group yielded consistent results bracketed between 106 Ma and 123 Ma. During.the Late Cretaceous and possibly lasted for Paleogene, the Muping-Jimo fault zone moved right-laterally and controls pull-apart opening of the Jiaolai(Jiaoxian- Laiyang) basin. A phase of transpression, characterized by NW-SE compression, occurred near the end of the Early Cretaceous, which caused the Early Cretaceous basins to be deformed and inverted, and the Muping-Jimo fault zone to be activated left-laterally. The kinematic history of the Mu