| 安宁河断裂带新生代构造变形与磁组构特征 |
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| 引用本文：华天,李金玺,李智武,袁梦雨,蔡鸿燕,童馗,王自剑,李轲,刘树根,曾璐.2022.安宁河断裂带新生代构造变形与磁组构特征[J].地球学报,43(2):144-156. |
| DOI：10.3975/cagsb.2021.122001 |
| 摘要点击次数: 1954 |
| 全文下载次数: 1201 |
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| 基金项目:中国科学院战略性先导科技专项(编号: XDA23090203);国家自然科学基金(编号: 41602153; 41472107) |
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| 中文摘要:安宁河断裂带作为青藏高原东边界鲜水河—小江断裂带的重要组成部分, 是认识高原隆升和侧向生长的理想对象。为了进一步厘清安宁河断裂带新生代以来的构造变形, 本文对该断裂带中段进行了详细的野外地质调查和磁组构研究, 厘定了安宁河断裂带新生代构造变形特征和序列, 主要获得以下认识: (1)构造解析表明, 安宁河断裂带存在三期构造变形。据切割关系判断, 第一期变形最大主应力方向为NE–SW向, 造成局部断层的逆冲和右旋走滑运动。第二期变形最大主应力方向为E–W向, 形成走向近N–S的劈理带。第三期变形最大主应力方向为NW–SE向, 以断层的逆冲活动为主。(2)岩石磁学结果表明, 上三叠统白果湾组主要载磁矿物为顺磁性的硅酸盐矿物。安宁河断裂带磁面理较磁线理发育, 磁化率椭球体以扁圆型为主, 表明安宁河断裂带以挤压、剪切变形为主。最小磁化率主轴方位表明安宁河断裂带曾受NW–SE向和E–W向主压应力控制。构造变形与磁组构对比研究表明, 多期脆性变形下, 磁组构对应变的记录具有差异性。在脆性变形地区开展磁组构研究, 应建立在构造解析基础之上。(3)结合区域构造演化、地层不整合关系以及年代学研究, 本文推测早期NE–SW向挤压可能与印亚板块初始碰撞相关。NE–SW向应力场控制下, 安宁河断裂重新激活。E–W向应力可能主要响应青藏高原的向东生长, 可能主要发生在渐新世到早中新世。NW–SE向应力可能主要响应青藏高原的南东向生长, 即川滇地块的侧向挤出。在此期间, 鲜水河断裂、安宁河断裂和小江断裂自北向南以走滑形式贯通。 |
| 中文关键词:安宁河断裂带 新生代 构造变形 磁组构 |
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| Cenozoic Structural Deformation and Magnetic Fabric Characteristics of Anninghe Fault Zone |
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| Abstract:The Anninghe fault zone located on the southeast margin of the Tibet Plateau is an important constituent of the Xianshuihe–Xiaojiang fault system. It is an ideal target to understand the uplift and lateral growth of the plateau. To further clarify the structural deformation of the Anninghe fault zone since the Cenozoic, in this study, a detailed field geological survey and magnetic fabric study on the middle section of the fault zone were conducted. The characteristics and sequence of the Cenozoic structural deformation of the Anninghe fault zone were determined. The following results were obtained: (1) Structural analysis showed that there are three stages of structural deformation in the Anninghe fault zone. According to the cutting relationship, the direction of the maximum principal stress of the first stage deformation is NE–SW, resulting in thrust and dextral strike slip movement of the local faults. In the second stage, the direction of the maximum principal stress is E–W, forming a cleavage zone oriented in the N–S direction. The direction of the maximum principal stress of the third stage deformation is NW–SE, which is dominated by thrust. (2) The rock magnetism study showed that the main magnetic bearing minerals of Baiguowan formation are paramagnetic silicate minerals. The Anninghe fault zone has more developed magnetic foliation than the magnetic lineation, and the susceptibility ellipsoid is mainly oblate, indicating that the Anninghe fault zone is dominated by compression and shear deformation. Moreover, the comparative study of tectonic deformation and magnetic fabric showed that the records of magnetic fabric on strain are different under multi-stage brittle deformation. Evaluation of the magnetic fabric in the brittle deformation area must be based on structural analysis. (3) Combined with regional tectonic evolution, stratigraphic unconformity, and geochronology, this study speculates that the NE–SW compression may be related to the initial collision of the Indo-Asian plate. Under the control of the NE–SW stress field, the Anninghe fault zone is reactivated. The E–W compression may mainly respond to the eastward growth of the Tibetan Plateau, which may have occurred from Oligocene to Early Miocene. Moreover, the NW–SE compression may mainly respond to the southeastward growth of the Tibetan Plateau—that is, the lateral extrusion of the Chuandian block. During this period, the Xianshuihe–Anninghe–Xiaojiang fault formed in the form of sinistral strike-slip from N–S. |
| keywords:Anninghe fault zone cenozoic structural deformation magnetic fabric |
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