江南东段地区NE-SW向断裂带断层滑移矢量反演及其大地构造意义

Inversion and Tectonic Implications of Fault-Slip Data of NE-SW-Striking Fault Zones in Eastern Jiangnan Area

华南中-新生代构造演化受太平洋构造域和特提斯洋构造域的联合控制.以江南东段NE-SW向景德镇-歙县剪切带和球川-萧山断裂中发育的脆性断层为研究对象,利用野外交切关系和断层滑移矢量反演方法厘定了7期构造变形序列并反演了各期古构造应力场,讨论了断层活动的时代及其动力学.白垩纪至新生代研究区7期古构造应力场分别为:(1)早白垩世早期(136～125Ma)NW-SE向伸展;(2)早白垩世晚期(125～107Ma)N-S向挤压和E-W向伸展;(3)早白垩世末期至晚白垩世早期(105～86Ma)NW-SE向伸展;(4)白垩世中期(86～80Ma)NW-SE向挤压和NE-SW向伸展;(5)晚白垩世晚期至始新世末期(80～36Ma)N-S向伸展;(6)始新世末期至渐新世早期(36～30Ma)NE-SW向挤压和NW-SE向伸展;(7)渐新世早期至中新世中期(30～17Ma)NE-SW向伸展.结合区域地质研究表明,第1期至第4期古构造应力场与古太平洋构造域的板片后撤、俯冲以及微块体(菲律宾地块)间的碰撞作用有关;第5期伸展作用受控于新特提斯构造域俯冲板片后撤,而第6期和第7期古构造应力场主要与印-亚碰撞的远程效应有关.白垩纪至新生代,华南东部受伸展构造体制和走滑构造体制的交替控制.先存断裂的发育可能是导致华南晚中生代走滑构造体制的主要控制因素.

Mesozoic to Cenozoic tectonic evolution of the South China Block was dominated jointly by the Pacific tectonic domain and the Tethys tectonic domain. Brittle faulting of the NE-SW-striking Jingdezhen-Shexian shear zone and the Qiuchuan-Xiaoshan fault was studied in the eastern Jiangnan area. Based on cross-cutting relations and inversion of fault-slip data, seven stages of structural deformation were identified and their paleostress fields were inverted. Their formation ages and geodynamics are also discussed. Cretaceous to Cenozoic paleostress fields that occurred in the eastern Jiangnan area are:(1) NW-SE extension during early stage of Early Cretaceous (136-125 Ma);(2) N-S compression and E-W extension during late stage of Early Cretaceous (125-107 Ma);(3) latest Early Cretaceous to early stage of Early Cretaceous (105-86 Ma) NW-SE extension;(4) middle Late Cretaceous (86-80 Ma) NW-SE compression and NE-SW extension;(5) N-S extension during late stage of Late Cretaceous to latest Eocene (80-36 Ma);(6) NE-SW compression and NW-SE extension during latest Eocene to early stage of Oligocene (36-30 Ma);(7) early stage of Oligocene to medium stage of Miocene (30-17 Ma) NE-SW extension. Combining these with regional geological evidences, the first to fourth paleostress fields were related to roll-back, subduction of the Pacific Plate and collision between micro-terrane (Philippine Sea plate) and the South China Block. The fifth paleostress field was attributed to the roll-back of Neo-Tethys oceanic plate whereas the sixth and seventh paleostress fields to the far-field effect of the India-Asia collision. Extensional regimes and strike-slip regimes alternately dominated Cretaceous to Cenozoic structural deformation in the South China Block. The predominated factor for the strike-slip regimes in the South China Block is re-existed faults occurred before Late Mesozoic.