渤海海域中郯庐深断裂带的结构模型及新生代运动学

Structural model and Cenozoic kinematics of Tan-Lu deep fracture zone in Bohai Sea area

郯庐深断裂带自安徽庐江—山东郯城、沂水、安丘一线向北延伸进入渤海海域被新生代盆地沉积层和海水覆盖。根据区域重、磁力异常图解释的渤海海域的郯庐深断裂带位于莱州湾—渤海东部—辽东湾东部一线,总体走向NNE,对应于渤海海域NNE向地幔隆起带的东部斜坡。渤海海域新生代盆地与地幔隆起呈镜像反映,构成古近纪断陷的边界断层包括NE向、NNE向、NEE向、NW向和NWW向等多个方向,且多表现出铲式正断层的几何学、运动学特征。渤海海域新生代盆地在莱州湾—渤海东部—辽东湾东部发育有由2～4条走向NNE向、陡倾斜的基底走滑断层及相关构造变形组成的右旋走滑构造带,位置与区域重磁资料解释的郯庐深断裂带大致相当。综合深层地壳结构和新生代盆地构造特征有理由认为,渤海海域中新生代盆地中的走向NNE向、陡倾斜的基底走滑断层构造带的与深层至少切割莫霍面的深断裂带构成了一条地壳尺度垂向的强变形构造带。渤海海域的郯庐深断裂带在新生代时期郯庐断裂带并非只发生右旋走滑运动,在区域裂陷作用中控制古近纪断陷的伸展断层可能利用了深断裂带在浅层地壳的部分断层面,并且因为伸展位移在中地壳层中发生拆离滑脱,而深断裂带的右旋走滑位移才使浅层断层与深层断层保持紧密联系。

The Tan-Lu DFZ（deep fracture zone） stretches from Lujiang（in Anhui） through Tancheng,Yishui and Anqiu（in Shandong） to Bohai Sea area where it is covered by Cenozoic basin sedimentary layer and sea water.Judging from the regional gravity-magnetic field map,Tan-Lu DFZ in the Bohai Sea area lies along the Laizhou Bay—eastern Bohai Sea—Liaodong Bay line,generally striking NNE,parallel to the eastern limb of the mantle rise in the Bohai Sea.The Cenozoic basin in the Bohai Sea resembles a mirror image of the mantle rise.The boundary faults of the Paleogene rifting sub-basins are developed in multiple directions,dominantly striking NE,NNE,NEE,NW,NWW,and mostly showing characteristics of listric normal faults in terms of geometry and kinematics.2 to 4 steeply dipping NNE-trending basement strike-slip faults developed along the Laizhou Bay—eastern Bohai Sea—Liaodong Bay line constitute a right-lateral strike-slip structure with their associated structural deformation,and the location is approximately consistent with the Tan-Lu DFZ interpreted by the regional gravity-magnetic field map.In combination with the characteristics of deep crust structure and Cenozoic basin structure,the authors have reasons to believe that the structural model of Tan-Lu DFZ in Bohai Sea area is a vertical strong deformation zone at the crust scale,which is composed of the NNE-trending right-lateral strike-slip zone in Cenozoic basin and the deep faults cutting the Moho surface.However,the Tan-Lu DFZ is not a simply right-lateral strike-slip zone.Extensional faults controlling Paleogene fault sub-basin might have utilized the fault surface in shallow crust of the deep fracture zone,and could have been detached in middle crust layer during extensional displacement;nevertheless,the right-lateral strike-slip displacement of the deep fracture zone was likely to cause the connection between the shallow fault and the deep fault.