| 西南印度洋中脊斜向扩张分段特征及构造成因探讨 |
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| 引用本文： | 张华添,李江海,陶春辉.西南印度洋中脊斜向扩张分段特征及构造成因探讨[J].地学前缘,2021,28(2):271-283. |
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| 作者姓名： | 张华添 李江海 陶春辉 |
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| 作者单位： | 北京大学地球与空间科学学院教育部造山与地壳演化重点实验室,北京100871;自然资源部第二海洋研究所自然资源部海底科学重点实验室,浙江杭州310012 |
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| 基金项目： | 中国大洋“十三五”课题项目(DY135-S2-01-01);中国大洋“十三五”课题项目(DY135-S1-01-03-01) |
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| 摘 要： | 斜向扩张是超慢速扩张洋中脊独特的构造特征,其地形分段特征明显区别于经典的快速-慢速端元洋中脊模型,是理解超慢速扩张洋中脊地质过程的重要切入点。基于西南印度洋中脊Indomed-Gallieni和Shaka-DuToit段多波束地形数据,分析了不同斜向扩张角度(α)洋中脊的地形分段样式。其中,46.5°~47.5°E(α=5°)、16°~25°E(α=10°)和48.5°~52°E(α=15°)为近正向扩张段,发育雁列式叠置的中央火山脊;47.5°~48.5°E(α=50°)和16°~25°E(α=60°)为斜向扩张段,仅在洋脊段中部形成中央火山脊。利用有限差分+颗粒法(FD+MIC)数值模拟技术研究了洋中脊应变分布特征对不同α值的响应,结合地形分析,认为斜向扩张角度和温度异常分布共同控制了洋中脊地形分段样式。近正向扩张洋中脊(α＜20°)在温度异常处形成地壳伸展应变的集中区,有利于岩浆汇聚,发育雁列式叠置的中央火山脊,其位置随温度异常分布的变化而改变;斜向扩张洋中脊(α>20°)地壳伸展应变集中区的位置受斜向扩张几何样式控制,在洋脊段中部发育中央火山脊,对温度异常不敏感,形成位置长期固定的岩浆活动中心。
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| 关 键 词： | 斜向扩张 超慢速扩张洋中脊 地形分段样式 多波束地形 数值模拟 |
| 收稿时间： | 2019-01-02 |
Discussions on the bathymetric segmentation and tectonogenesis of the oblique spreading Southwest Indian Ridge |
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| ZHANG Huatian,LI Jianghai,TAO Chunhui.Discussions on the bathymetric segmentation and tectonogenesis of the oblique spreading Southwest Indian Ridge[J].Earth Science Frontiers,2021,28(2):271-283. |
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| Authors: | ZHANG Huatian LI Jianghai TAO Chunhui |
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| Institution: | 1. Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China2. Ministry of Natual Resources Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natual Resources, Hangzhou 310012, China |
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| Abstract: | Oblique spreading is a characteristic feature of ultra-slow spreading ridges. As its bathymetric segmentation pattern is distinct from classical fast-slow spreading ridge models, it can provide insight into the geological process of ultra-slow spreading ridges. Based on multibeam bathymetric data, the segmentation patterns (with variable spreading obliquity (α)) of the Southwest Indian Ridge (SWIR) Indomed-Gallieni and Shaka-DuToit zones are analyzed. Results show that the SWIR segments, between 46.5°E and 47.5°E (α=5°), 16°E and 25°E (α=10°), and 48.5°E and 52°E (α=15°), respectively, are quasi-orthogonal spreading segments, which have developed en échelon axial volcanic ridges. Along the axis of the oblique spreading SWIR, between 47.5°E and 48.5°E (α=50°) and between 16°E and 25°E (α=60°), only one axial volcanic ridge has formed at the center of the axis. The distribution of the strain rates along the mid-ocean ridges with variable obliquity (α) is calculated by a ‘finite difference+markers in cells’ (FD+MIC) technique. Combined with bathymetry analysis, two factors influencing the segmentation pattern of oblique spreading results, namely, the spreading obliquity and distribution of temperature disturbance, are proposed. Along the quasi-orthogonal spreading segments (α<20°), temperature disturbance led to localization of extensional strain and development of en echelon axial volcanic ridges. In the oblique spreading segments (α>20°), strain localization was controlled by oblique geometry so the axial volcanic ridges only developed in the middle of the segment. These volcanic ridges were insensitive to temperature disturbance, therefore, they could form lasting fixed local magmatic centers. |
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| Keywords: | oblique spreading ultra-slow spreading ridges bathymetric segmentation multibeam bathymetry numerical modeling |
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