摘要
郯庐断裂带内一系列走滑糜棱岩类的^(40)Ar/^(39)Ar测年表明,郯庐断裂早白垩世发生了左旋走滑运动。这一大规模的走滑运动,造成了两类走滑构造,一类为变质岩中低绿片岩相左旋韧性剪切带,另一类为中生代火成岩、沉积岩中的脆性、脆-韧性左行平移断层。这反映断裂带的走滑运动从早白垩世初期持续到早白垩世后期。断裂带的走滑运动诱发了大规模的、以富钾、中酸性为主的岩浆活动。地球化学分析显示,这些岩浆岩既有壳源的信息,也有幔源的贡献,反映是断裂减压、壳-幔相互作用下形成的岩浆活动,也暗示断裂带在走滑期切入壳-幔边界。该断裂带走滑运动中,除了在莱阳盆地形成了拉分盆地外,还在合肥盆地东部造成了走滑挠曲盆地,控制下白垩统朱巷组的沉积。郯庐断裂带早白垩世走滑运动中的构造、岩浆、沉积事件,是西太平洋伊泽纳崎板块高速斜向俯冲的结果,属于滨太平洋构造。
The 40Ar/39Ar values of the mylonite series from the Tan-Lu fault belt demonstrate that the fault belt has experienced sinistral strike-slip movement in the Early Cretaceous. The large-scale strike-slip movement caused two types of strike-slip structures. One is sinistral ductile shear belts with low greenschist facies in metamorphic rocks. The other is brittle or brittle-ductile sinistral wrench faults in Mesozoic igneous and sedimentary rocks. These suggest that the strike-slip movement lasted from the earliest to the latest Early Cretaceous. The strike-slip movement triggered large-scale magmatism characterized by K-rich and intermediate rocks. Geochemical analyses of the igneous rocks show that the rocks contain both crust-derived and mantle-derived information. It is proposed therefore that the magmatism occurred in the conditions of faulting depression and crust-mantle in-teraction and that the fault cut into crust-mantle boundary during the strike-slip period. In addition to the Early Cretaceous pull-apart basin in the Laiyang basin, a strike-slip flexural basin with deposition of the Lower Creta-ceous Zhuxiang Formation was developed in the east of the Hefei Basin during strike-slip movement of the fault belt. The structures, magmatism and sedimentation of the Tan-Lu fault belt during its Early Cretaceous strike-slip movement are caused by high-speed, oblique subduction of the Izawa Nosaki plate in West Pacific, and are parts of the circum-Pacific tectonics.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2002年第3期325-334,共10页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号 49872074)资助的成果。
