西南印度洋构造地貌与构造过程  

Morphotectonics and Tectonic Processes of the Southwest Indian Ocean

作　　者：李三忠[1,2] 索艳慧[1,2] 余珊[1,2] 赵淑娟[1,2] 戴黎明[1,2] 曹花花[1,2] 张臻[1,2] 刘为勇[3] 张国堙[3] 

机构地区：[1]海底科学与探测技术教育部重点实验室,山东青岛266100 [2]中国海洋大学海洋地球科学学院,山东青岛266100 [3]国家海洋局第二海洋研究所国家海洋局海底科学重点实验室,浙江杭州310012

出　　处：《大地构造与成矿学》2015年第1期15-29,共15页Geotectonica et Metallogenia

基　　金：国家自然科学基金杰出青年基金项目(批准号:41325009);重大项目课题(编号:41190072);973项目(编号:2012CB417305)联合资助

摘　　要：本文基于海底水深数据,制定了西南印度洋超慢速扩张脊新的海底构造地貌划分原则,将西南印度洋划分为7级构造地貌单元；并以该洋中脊中段的Discovery II和Gallieni转换断层之间及其邻区的海底构造地貌特征为依据,将其与该区断裂演化、分段性、分段拓展机制、中央裂谷形成过程、脊–柱相互作用和洋中脊跃迁进行综合分析。结果表明,该区洋中脊可以划分为4个三级构造地貌单元（即洋中脊的一级分段）,从西向东被Andrew Bain和Prince Edwards、Discovery II以及Gallieni转换断层依次分割,分别反映为强热点–洋中脊相互作用的扩张脊、弱热点–洋中脊相互作用的扩张脊和正常超慢速扩张脊的地貌类型。每个三级分段可进一步划分为3~4个四级分段,本文仅侧重Discovery II和Gallieni转换断层间洋中脊四到七级的4个级别分段划分（即洋中脊的四级构造地貌单元再划分为3级）。其中,第七级构造地貌单元分别为侧列式裂谷（剪切带）、雁列式裂谷、横断层带等构造分割。该段洋中脊先后受 Marion、Crozet、Madagascar 等热点或海台的影响,经历了3次洋中脊跃迁,时间大致分别为80 Ma,60 Ma和40 Ma,该过程与冈瓦纳大陆裂解以来的大洋演化有关。最后,本文详细分析了20 Ma以来的西南印度洋洋中脊轴部的周期性拉分式断陷、多米诺式箕状断陷、地堑式断陷和海洋核杂岩等构造过程。The Southwest Indian mid-ocean ridge （SWIR） is an ultraslow spreading ridge. Based on the submarine bathymetric data, we develop a new division principle on submarine morphotectonics and subdivide the SWIR into the seven-order tectonic geomorphologic units. Taking its submarine morphotectonics in the middle segment and adjacent seafloors of the mid-ocean ridge between Discovery II and Gallieni transform faults as a sample, this paper systematically analyzes its tectonic evolution, segmentation, segmentation and propagation mechanism, the formation of the central rift valley, the ridge-plume interactions, and the ocean ridge jumping. The results showed that the mid-ocean ridges can be divided into four three-order morphotectonics units （i.e., one-order segments of mid-ocean ridge）, from west to east, which are separated by the Andrew Bain, the Prince Edwards, the Discovery II, and the Gallieni transform faults, respectively, corresponding to ridge landforms associated with a strongly hotspot-affected ridge, a weakly hotspot-affected ridge, and a normal ultraslow spreading ridge. Each segment can be further subdivided into three or four secondary segments. This paper focuses only on the segmentation and division from fourth-order to seventh-order morphotectonics units between the Discovery II and the Gallieni transform faults （i.e., the fourth-order morphotectonics unit of mid-ocean ridges can be subdivided into other three secondary units）. Here the seventh-order morphotectonics unit consists of segments of laterally-aligned rifts （shear zone）, en echelon rifts, and other transverse-faulting structures. The mid-ocean ridge segment experienced three oceanic ridge jumping at about 80 Ma, 60 Ma and 40 Ma, respectively, which were affected by the Marion and Crozet hotspots, or the Madagascar Plateau, etc. The oceanic processes of the SWIR are related to the Gondwana breakup, and its tectonic processes has been analyzed in detail as the periodic pull-apart extension, domino-style half-graben, graben sub

关 键 词：西南印度洋 转换断层 分段性 构造地貌 断层组合 

分 类 号：P67[天文地球—海洋地质]