从南大西洋裂解过程解密大陆漂移的驱动力

doi:10.13745/j.esf.sf.2021.12.27

地学前缘 ›› 2022, Vol. 29 ›› Issue (1): 316-327.DOI: 10.13745/j.esf.sf.2021.12.27

从南大西洋裂解过程解密大陆漂移的驱动力

梁光河¹^,²^,³(), 杨巍然⁴^,^*()

1.中国科学院地质与地球物理研究所矿产资源研究重点实验室, 北京 100029
2.中国科学院地球科学研究院, 北京 100029
3.中国科学院大学, 北京 100029
4.中国地质大学(武汉) 地球科学学院, 湖北武汉 430074

收稿日期:2021-12-15 修回日期:2021-12-22 出版日期:2022-01-25 发布日期:2022-02-22
通信作者: 杨巍然
作者简介:梁光河(1965—),男,副研究员,从事地球物理与大地构造研究。E-mail: lgh@mail.iggcas.ac.cn
基金资助:
国家科技基础资源调查专项第二次青藏高原综合科学考察研究项目(2019QZKK0805)

Decipher the driving force in continental drift from new insights about the South Atlantic breakup process

LIANG Guanghe¹^,²^,³(), YANG Weiran⁴^,^*()

1. Key Laboratory of Mineral Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2. Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
3. University of Chinese Academy of Sciences, Beijing 100029, China
4. School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China

Received:2021-12-15 Revised:2021-12-22 Online:2022-01-25 Published:2022-02-22
Contact: YANG Weiran

摘要/Abstract

摘要：

南大西洋裂解造成的非洲和南美洲的大陆分离得到了广泛认可,该区域也与大陆漂移学说的诞生密切相关。但大陆漂移的驱动力从其提出至今一直存在争议,定量化分析大西洋裂解过程中板块运动的驱动力显得尤为重要。我们研究了南大西洋两侧被动大陆边缘盆地区域的两条深反射地震勘探剖面,在构造地质解译基础上,详细估算了非洲大陆的莫霍面倾角,得到了沿莫霍面地壳重力滑移剪切力的大小,用于解释大西洋裂解过程中非洲大陆运动的动力机制。结果说明,非洲大陆板块在地幔上涌形成的倾斜界面上能够产生强大的重力滑移力,且南部驱动力大于中部。大陆板块依靠连续的地幔热上涌和重力滑移力会持续漂移。该模型能够合理解释大西洋上诸多线状分布的大陆残片的成因机制,也能合理解释南大西洋南部宽度大于中部的内在原因,最后对南大西洋的打开过程进行了精细的构造演化史恢复。该研究为板块运动提供了一个新的动力模式,为认识板块运动驱动力提供了更为精确的约束信息。

关键词: 大西洋裂解, 非洲大陆板块, 南美洲大陆板块, 重力滑移驱动力, 大陆漂移

Abstract:

It has been widely recognized that the separation of the African and South American continents is caused by the South Atlantic breakup. The South Atlantic region is highly relevant to the development of the continental drift hypothesis. The driving force behind continental drift, however, has been in debate ever since the hypothesis was proposed. Therefore, quantitative analysis of the forces driving plate movement in the process of Atlantic breakup is particularly important. Here, we analyzed two deep seismic reflection survey profiles located on either side of the South Atlantic, in passive continental margin basins, and estimated the Moho dip angle of the African continent on the basis of tectonic geological interpretation. We then calculated the magnitude of crustal gravitational slip shear force along the Moho to explain the dynamic mechanism of African continent movement in the process of Atlantic breakup. We demonstrated that the African continental crust can produce a strong gravitational slip force on the inclined interface formed by mantle upwelling, and the shear force is greater in the south than in the middle part of the crust. According to our analysis, the continental crust can drift continuously by continuous hot mantle upwelling and gravitational slide. This model can reasonably explain the genetic mechanism for the many linear continental fragments in the Atlantic Ocean, and it can also provide an internal reason for why the South Atlantic today is wider in the south than it is in the middle. Based on this model we reconstructed the tectonic evolutionary history of the South Atlantic breakup process. This research established a new dynamic model of plate motion and provided more accurate constraint on understanding the driving force behind plate movement.

Key words: Atlantic breakup, African continental crust, South American continental crust, gravitational slip, continental drift

中图分类号:

P542
P541

梁光河, 杨巍然. 从南大西洋裂解过程解密大陆漂移的驱动力[J]. 地学前缘, 2022, 29(1): 316-327.

LIANG Guanghe, YANG Weiran. Decipher the driving force in continental drift from new insights about the South Atlantic breakup process[J]. Earth Science Frontiers, 2022, 29(1): 316-327.

图/表 9

图1 南大西洋区域地貌高程和主要海隆及火山分布图

Fig.1 Geomorphic elevation and distribution of main seamounts and volcanoes in the South Atlantic region

图2 南大西洋被动大陆边缘盆地分布及研究区剖面位置示意图 (据文献[19]修改)

Fig.2 Distribution of passive continental marginal basins on the two sides of the South Atlantic and the profile locations in the study area. Modified after [19].

图3 南大西洋两条地震勘探剖面构造图及莫霍面倾角 (修编自文献[19]) a—大西洋中段A-A'剖面图; b—南大西洋南部B-B'剖面图。图中右侧紫色方框是计算莫霍面倾角的区域。

Fig.3 Two structural sections of the passive basins on two sides of the South Atlantic and related Moho dip angles (modified after [19]). (a) Profile A-A' in the middle South Atlantic. (b) Profile B-B' in the southern South Atlantic. Areas inside the purple box were used in calculating the Moho dip angles.

图4 倾斜莫霍面重力滑脱模型及剪切应力计算

Fig.4 Model of gravitational sliding on inclined Moho surface and calculation of shear stress

图5 南大西洋裂解和大陆漂移过程示意图 a—陆块裂解初期;b—漂移过程中;c—当前状态。

Fig.5 Schematic diagram of the South Atlantic breakup and continental drift processes. (a) Initial cracking stage. (b) Drift process. (c) Current state.

图6 地幔上涌和重力滑移双驱动新大陆漂移模型示意图

Fig.6 Schematic diagram of the new continent drift model, demonstrating the process is driven by mantle upwelling and gravitational slip

图7 大西洋裂解构造演化史恢复示意图

Fig.7 Schematic diagram illustrating the tectonic evolutionary process of the Atlantic breakup

图8 两种被动大陆边缘结构模型与滑移驱动力简化图 (a和b据文献[22]) a—火山型被动大陆边缘模型;b—贫岩浆型被动大陆边缘模型;c—对a的简化地质解释;d—对b的简化地质解释。

Fig.8 Simplified diagram of two passive continental margin structural models (adapted from [22]) and the slip driving force. (a) Model of passive continent with volcanic-rifted margin. (b) Model of passive continent with magma-poor margin. (c) Simplified geological interpretation of a. (d) Simplified geological interpretation of b.

图9 大陆(A)和大洋(B)岩石圈差应力结构特征对比 (改自文献[32,33,34])

Fig.9 Comparison of differential stress characteristics between continental (A) and oceanic (B) lithosphere. Modified after [32,33,34].

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从南大西洋裂解过程解密大陆漂移的驱动力

Decipher the driving force in continental drift from new insights about the South Atlantic breakup process

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