关键词: 郯庐断裂带, 同位素年龄测定, 断层滑动, 太平洋板块

Abstract: The Tanlu fault zone extending toward northeast China is branched into three subdivison parts. They are Yilan-Yitong,Mishan-Dunhua and Siping-Changchun faults. According to the isotopic chronological determination,the Rb-Sr isochron age of the diabase whole rock within the fault zone is (100±5.9)Ma,the ⁴⁰Ar/³⁹Ar plateau age of the augite is 105Ma. The ⁴⁰Ar/³⁹Ar plateau age of biotite mineral selected from the fault breccia and schists (mica quartz schists) within the Yilan Yitong fault zone is (100±1)Ma and (105.5±1.2)Ma～(95.7±1.8)Ma,respectively. In this region,in view of the outcrop investigation and comparison of different strata,strain calculation,the fault displacement is about 4km,or not more than 10km which is far less than the general estimation that the Tanlu fault zone is displaced more than 500km (Xu,1984). In this part,deformation of the fault is not very intensive,only cutting the Quantou formation (122Ma) of the lower Cretaceous system. Within the fault zone,the fault gouges developed less than 0.5m width. All of the evidence illustrates that the sinistral strike slip occurred during the time of 100Ma,i.e.,the end of early Cretaceous early of late Cretaceous. Activities of this part of the Tanlu fault zone affect the neighbouring basins where inverted structures occur. It is suggested that the strike-slip movement along the Tanlu fault of this part occurred on the basis of counterclockwise rotation of the eastern Asia continent and is associated with the subduction of the Pacific plate which induced upwelling of the upper mantle.

Key words: Tancheng Lujiang fault, Isotopic age dating, Fault slip, Pacific plate 