驱动印度大陆北漂的动力是什么?

doi:10.13745/j.esf.sf.2022.11.5

摘要/Abstract

摘要：

印度大陆板块从位于南半球的冈瓦纳大陆裂解并漂移到当前位置已得到普遍认可,但大陆板块运动的驱动力在大陆漂移学说提出至今一直存在争议,定量估算印度大陆板块运动的驱动力有助于减少争议。我们收集了印度大陆南部被动大陆边缘盆地区域的两条深反射地震勘探剖面,并对其进行了构造地质解译,详细估算了其莫霍面倾角,得到了地壳重力滑移剪切力的大小,用于解释印度大陆运动的动力机制。结果说明,印度大陆板块在地幔上涌形成的倾斜界面上能够产生足够大的重力滑移力驱动印度大陆向北漂移。由此提出一个“地幔上涌和重力滑移”双驱动大陆漂移模型,即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印度洋上的大陆残片,也能合理解释印度大陆北漂中左旋的成因机制。该重力滑移驱动机制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: 印度大陆北漂, 大陆地壳, 重力滑移, 动力机制, 地震勘探

Abstract:

It is widely recognized that the Indian continental plate splits and drifts from Gondwana in the southern hemisphere to its current location, but the driving force behind such movement has been under debate ever since the theory of continental drift was put forward. Quantitative estimation of the driving force may help to resolve the issue. We collected two deep reflection seismic exploration profiles in the passive continental margin basin area of the southern Indian subcontinent. We interpreted the data structurally, estimated the dip angle of Moho surface in detail, and obtained the magnitude of crustal gravity slip shear force which was used to explain the dynamic mechanism of the Indian plate movement. The results show that the Indian continental plate can produce enough gravity slip force on the inclining interface formed by mantle upwelling to drive the Indian subcontinent to drift northward. Hence, a “mantle upwelling and gravity slip” dual-drive continental-drift model is proposed. That is, continental plate can drift by relying on continuous mantle thermal upwelling and gravity slip force. This model can reasonably explain the continental fragments in the Indian Ocean and the genetic mechanism of left rotation in the northward drift of the Indian continent. The gravity-slip driving mechanism provides a new dynamic model for plate motion and more accurate constraints for understanding the driving force behind plate motion.

Key words: northward drift of Indian continent, continental crust, gravity slip, dynamic mechanism, seismic exploration

中图分类号:

P541

梁光河, 杨巍然. 驱动印度大陆北漂的动力是什么?[J]. 地学前缘, 2023, 30(2): 68-80.

LIANG Guanghe, YANG Weiran. What forces are driving the Indian subcontinent to drift northward?[J]. Earth Science Frontiers, 2023, 30(2): 68-80.

图/表 11

图1 印度洋盆及周缘大地构造略图(修编自文献[8,26]) 1—马斯克林洋底高原;2—马达加斯加微陆块;3—马达加斯加洋底高原;4—莫桑比克微陆块;5—厄加勒斯微陆块;6—马里昂洋底高原;7—Conrad海隆;8—克洛泽洋底高原;9—Elan Bank微陆块;10—凯尔盖朗洋底高原;11—Broken脊;12—纳多鲁列斯微陆块;13—Cuvier微陆块;14—Exmouth微陆块;15—东经90°海岭;16—查戈斯-拉卡迪夫海岭;LLSVP—超级地幔柱。Ⅰ—西索马里盆地;Ⅱ—马斯克林盆地;Ⅲ—Gop裂谷;Ⅳ—沃顿洋脊;Ⅴ—南海。a—红河走滑断裂;b—实皆走滑断裂;c—苏门答腊走滑断裂;d—苏门答腊—爪哇海沟;e—Arakan前陆冲断带;f—喜马拉雅前陆冲断带;g—恰曼走滑断裂;h—马卡兰增生楔;i—扎格罗斯前陆冲断带;j—东非裂谷系;k—戴维走滑断裂。

Fig.1 Tectonic sketch map of the Indian Ocean basin and surrounding areas. Modified after [8,26].

图2 印度大陆板块周边地震勘探剖面(b据文献[28]) a—剖面平面位置图; b—天然地震勘探接收函数剖面地质解释。

Fig.2 (a) Locations of seismic exploration sections in the southern Indian continental plate and (b) geological interpretation of the seismic receiver function section along CD line (after [28]).

图3 剖面AB的地震勘探剖面及对应的地质解释(剖面位置见图2a)(a据文献[27]) a—人工反射波地震勘探剖面;b—该地震勘探剖面的构造地质解译,红色箭头表示印度陆壳滑移方向。

Fig.3 Seismic exploration profile of artificial reflected wave along line AB (after [27]), and (b) structural geological interpretation of the seismic exploration section (see Fig.2a for section location). Red arrow indicates slip direction of the Indian continental crust.

图4 剖面EF的地震勘探剖面及对应的地质解释(剖面位置见图2a)(a据文献[27]) a—人工反射波地震勘探剖面;b—该地震勘探剖面的构造地质解译,红色箭头表示印度陆壳滑移方向。

Fig.4 Seismic exploration profile of artificial reflected wave along line EF (after [27]), and (b) structural geological interpretation of the seismic exploration section (see Fig.2a for section location). Red arrow indicates slip direction of the Indian continental crust.

图5 剖面A-B-C-D和E-F-C-D综合地质解释

Fig.5 Comprehensive geological interpretation of sections along lines A-B-C-D and E-F-C-D (section locations see Fig.2a)

表1 重力滑移剪切应力计算表

Table 1 Calculation table of gravity slip shear stress

剖面模型参数	测线AB	测线EF
H	40 km	40 km
h	12 km	36 km
L	60 km	70 km
a	14°	27°
P	256 MPa	480 MPa

图6 印度裂离冈瓦纳大陆、漂移和碰撞过程示意图 a—印度陆块裂解初期;b—漂移过程中;c—碰撞俯冲。

Fig.6 Model describing the drift and collision processes during the breakup of India from Gondwana. (a) Initial stage of the breakup. (b) Drift process. (c) Collision-subduction process.

图7 重力滑移大陆漂移新模式示意图

Fig.7 A new model for continental drift driven by gravity slip force

图8 印度区域地质图及德干玄武岩和斯里兰卡成因动力机制示意图(a和b改自文献[8]) a—印度大陆当前受力状态;b—66 Ma印度大陆受力状态,说明德干玄武岩成因和斯里兰卡裂离印度的动力机制。图例说明同图1。

Fig.8 Schematics illustrating the splitting mechanism of the Deccan rift and Sri Lanka before 66 Ma, suggesting the difference in driving forces between the west and east sides of southern India generates sinistral shear to produce two rifts. (a) Current stress status of India. (b) Stress status of India at 66 Ma. Modified from [8].

图9 印度大陆晚白垩世和早始新世构造演化(改自文献[36])

Fig.9 Late-Cretaceous and Early-Eocene tectonic evolution of the Indian subcontinent. Modified from [36].

图10 基于大陆漂移后尾迹特征对东半球主要陆块的来源进行追踪

Fig.10 Tracing the origin of major continents in the Eastern Hemisphere based on wake characteristics of continental drift

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