秦岭构造带徽成盆地白垩纪-新生代构造应力场演化历史

沿凤-太断裂带发育的徽成盆地斜切秦岭构造带，成为东、西秦岭构造地貌的分界带。该盆地由上部成县群和下部东河群2套地层序列组成，之间为角度不整合接触。基于沉积地层序列、野外断层滑动矢量运动学分析和古构造应力场反演，结合上部成县群磁性地层学的研究结果和基性岩脉的年代测试结果，确定了该盆地2期伸展断陷成盆阶段和3期构造挤压改造的交替演化历史。认为下部盆地形成于早白垩世时期(107Ma之前)，成盆应力场为NWW- SEE引张，与东西向勉略断裂带左旋走滑拉分作用有关，其中加积了一套河湖相砂砾岩沉积。该走滑盆地在沉积晚期遭受NW- SE向挤压应力作用，控盆边界断层发生反转，地层发生宽缓的褶皱变形，基性岩脉侵位其中(107Ma)。上部新生的断陷盆地很可能形成于早白垩世晚期-晚白垩世(自107Ma以来)，受NW- SE引张作用，沿凤-太断裂带发生复活，其中堆积了一套河流相红色砂泥岩和砂砾岩沉积地层。该断陷盆地遭受2次挤压应力场的改造:早期NNW- SSE向挤压、晚期NNE- SSW向挤压，这两期挤压作用使控盆边界断裂(凤太断裂、勉略断裂)发生构造反转，地层陡倾，但盆地内部变形较弱。与区域构造演化历史对比，认为这两期挤压应力作用分别发生在白垩纪晚期与古近纪。

Evolution history of Cretaceous to Cenozoic structural tectonic field in the Huicheng Basin along the the Qinling tectonic belt

The elongated, nearly W- E trending Chenghui basin obliquely cuts the Qinling orogenic belt, forming the morphological boundary between the east and west Qinling Range. This basin is composed of two sedimentary sequences, namely the Donghe Group below and the Chengxian Group above, contacted by an unconformity. Based on the sedimentary sequence analysis, fault kinematic analysis and paleotectonic stress field inversion, we established a deformation history of this basin featured by two extensional phases for basin formation and three compressional stress fields for basin redeformation. The results show that the Donghe Group was formed in Early Cretaceous under local NWW- SEE extension resulting from the E- striking, left- lateral strike- slip motion on the Mianlve Fault. This strike- slip basin suffered from NW- SE compressions, which caused gentle folding of the Donghe Group. A latest Early Cretaceous mafic dyke dated to be 107 Ma was emplaced in this folded Donghe Group, which suggests that this compressional deformation event should predate 107 Ma. The Chengxian Group, mainly consisting of red- colored muddy conglonerates and coarse sandstone and mudstones, was deposited in an NWW- SEE extensional setting, and was controlled by the E- striking Fen- Tai fault. This sedimentary group has recorded two compressional stress events: NNW- SSE compression and NNE- SSW compression, both of which occurred respectively in latest Cretaceous and in late Paleogene. These two events resulted in the inversion of bains- bounding faults: the Feng- Tai fault and the Mianlve fault, but the interior of the Huicheng basin was only weakly deformed.