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-en

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 for understanding the driving force behind plate movement.

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

LIANG Guanghe, YANG Weiran. 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): 328-341.

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): 328-341.

图/表 8

Fig.1 Geomorphic elevation and distribution of main seamounts in the South Atlantic region. Lines A-A' and B-B' (in red) are the two seismic survey lines in this study. Modified after [9].

Fig.2 Two structural sections of the passive basins flanking the South Atlantic (modified after [9]), showing the Moho dip angles. (a) Profile A-A’ of the middle South Atlantic. (b) Profile B-B’ of the southern South Atlantic. The areas inside the purple boxes were used to calculate the dip angle of Moho surface.

Fig.3 Gravitational slippage model and shear stress calculation of inclined Moho surface

Fig.4 Schematic diagram of the South Atlantic breakup and continental drift processes. (a) Initial continental cracking stage. (b) Drift stage. (c) Current state.

Fig.5 Schematic diagram of the new continent drift model, demonstrating the process is driven by mantle upwelling and gravitational slip

Fig.6 Schematic diagrams illustrating the tectonic evolutionary process of the South Atlantic breaking up

Fig.7 Schematic diagrams of two passive continental margin structural models (modified after [22]) showing the slip driving forces. (a) Model of passive continental model with volcanic-rifted margin. (b) Model of passive continental model with magma-poor margin. (c) Simplified geological representation of a. (d) Simplified geological representation of b.

Fig.8 Comparison of the differential stress characteristics between continental (a) and oceanic (b) lithosphere. Modified after [32-34].

参考文献 44

[1]	WEGENER A. The origins of the continents[J]. Journal of Geodynamics, 2001, 32:31-63.
[2]	CHEN L, WANG X, LIANG X, et al. Subduction tectonics vs. Plume tectonics: discussion on driving forces for plate motion[J]. Science China: Earth Sciences, 2020, 50(4):501-514(in Chinese with English abstract).
[3]	YANG J S, LIAN D Y, WU W W, et al. Recycling of subducted crust in deep mantle: a new research orientation to earth dynamics[J]. Acta Geologica Sinica, 2021, 95(1):42-63 (in Chinese with English abstract).
[4]	WOLFGANG F, MARTIN M, BLAKEY R. Plate tectonics[M]. Berlin, Heidelberg: Springer, 2011.
[5]	HOERNLE K, ROHDE J, HAUFF F, et al. How and when plume zonation appeared during the 132 Myr evolution of the Tristan Hotspot?[J]. Nature Communications, 2015, 6:7799. https://doi.org/10.1038/ncomms8799 DOI URL
[6]	BOUYSSE P. Geological map of the world. Scale: 1∶50000000[M]. 3rd ed. Paris: CGMW/CCGM, 2009.
[7]	YONO T, CHOI D R, GAVRILOV A A, et al. Ancient and continental rocks in the Atlantic Ocean[J]. New Concepts in Global Tectonics Newsletter, 2009, 53:4-37.
[8]	SKOLOTNEV S G, BELTNEV V E, LEPEKHINA E N, et al. Younger and older zircons from rocks of the oceanic lithosphere in the central Atlantic and their geotectonic implications[J]. Geotectonics, 2010, 44(6):462-492. DOI URL
[9]	CLASS C, ROEX A L. South Atlantic DUPAL anomaly: dynamic and compositional evidence against a recent shallow origin[J]. Earth and Planetary Science Letters, 2011, 305(1/2):92-102. DOI URL
[10]	EWINGJ I, LUDWIG W J, EWING M, et al. Structure of the Scotia Sea and Falkland Plateau[J]. Journal of Geophysical Research Atmospheres, 1971, 76(29):7118-7137. DOI URL
[11]	DERUELLE B, NGOUNOUNO I, DEMAIFFE D. The ‘Cameroon Hot Line’ (CHL): a unique example of active alkaline intraplate structure in both oceanic and continental lithospheres[J]. Comptes Rendus: Géoscience, 2007, 339(9):589-600.
[12]	GANNOUN A, BURTON K W, BARFOD D N, et al. Resolving mantle and magmatic processes in basalts from the Cameroon volcanic line using the Re-Os isotope system[J]. Lithos, 2015, 224/225:1-12. DOI URL
[13]	VENTURA R S, GANADE C E, LACASSE C M, et al. Dating Gondwanan continental crust at the Rio Grande Rise, South Atlantic[J]. Terra Nova, 2019, 31:424-429. DOI URL
[14]	REN J S, XU Q Q, ZHAO L, et al. Looking for submerged landmasses[J]. Geological Review, 2015, 61(5):969-989.
[15]	ESCRIG S, SCHIANO P, SCHILLING J G, et al. Rhenium-osmium isotope systematics in MORB from the Southern Mid-Atlantic Ridge (40 degrees-50 degrees S)[J]. Earth and Planetary Science Letters, 2005, 235:528-548. DOI URL
[16]	ESCRIG S, CAPMAS F, DUPRE B, et al. Osmium isotopic constraints on the nature of the DUPAL anomaly from Indian mid-ocean-ridge basalts[J]. Nature, 2004, 431:59-63. DOI URL
[17]	PEATE D W, HAWKESWORTH C J, MANTOVANI M S M, et al. Petrogenesis and stratigraphy of the High-Ti/Y Urubici magma type in the Paraná Flood Basalt Province and implications for the nature of the ‘Dupal’-type mantle in the South Atlantic Region[J]. Journal of Petrology, 1999, 40:451-473. DOI URL
[18]	FODOR R V, HANAN B B. Geochemical evidence for the Trindade hotspot trace: Columbia seamount ankaramite[J]. Lithos, 2000, 51(4):293-304. DOI URL
[19]	ZHANG Y, LI J H, YANG M L, et al. Characteristics and genesis of structural segmentation of the passive continental margins on both sides of the South Atlantic[J]. China Petroleum Exploration, 2019, 24(6):799-806 (in Chinese with English abstract).
[20]	BRUNE S, HEINE C, CLIFT P D, et al. Rifted margin architecture and crustal rheology: reviewing Iberia-Newfoundland, Central South Atlantic, and South China Sea[J]. Marine & Petroleum Geology, 2017, 79:257-281.
[21]	BLAICH O A, INGE F J, FILIPPOS T. Crustal breakup and continent-ocean transition at South Atlantic conjugate margins[J]. Journal of Geophysical Research: Solid Earth, 2011, 116:B01402.
[22]	FRANKE D. Rifting, lithosphere breakup and volcanism: comparison of magma-poor and volcanic rifted margins[J]. Marine and Petroleum Geology, 2013, 43:63-87. DOI URL
[23]	CLERC C, RINGENBACH J C, JOLIVET L, et al. Rifted margins: ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust[J]. Gondwana Research, 2018, 53:20-40. DOI URL
[24]	BOTT M H P. Ridge push and associated plate interior stress in normal and hot spot regions[J]. Tectonophysics, 1991, 200:17-32. DOI URL
[25]	MAO X P, LU X L H, WANG X M, et al. Role of circumferential-direction stress in crustal movement[J]. Earth Science Frontiers, 2020, 27(1):221-233 (in Chinese with English abstract).
[26]	HUBBERT M K, RUBEY W W. Role of fluid pressure in mechanics of overthrust faulting[J]. Geological Society of America Bulletin, 1959, 70:115-166. DOI URL
[27]	HALES A L. Gravitational sliding and continental drift[J]. Earth and Planetary Science Letters, 1969, 6(1):31-34. DOI URL
[28]	JACOBY W R. Instability in the upper mantle and global plate movements[J]. Journal of Geophysical Research, 1970, 75:5671-5680. DOI URL
[29]	SUZANNE E, BEGLINGE R, HARRY D, et al. Relating petroleum system and play development to basin evolution: West African South Atlantic basins[J]. Marine and Petroleum Geology, 2012, 30:1-25. DOI URL
[30]	ZHU W L, CUI H Y, WU P K, et al. New development and outlook for oil and gas exploration in passive continental margin basins[J]. Acta Petrolei Sinica, 2017, 38(10):1099-1109 (in Chinese with English abstract).
[31]	WANG D J, LI J H, LI Y H. Rheology of the lower crust controls the polarity of conjugated basins asymmetry on the South Atlantic passive margin[J]. Earth Science Frontiers, 2020, 27(3):254-261 (in Chinese with English abstract).
[32]	KRONENBERG A, BRANDON M T, FLETCHER R, et al. Beyond plate tectonics: rheology and orogenesis of the continents[M]// New departures in structural geology and tectonics. San Francisco: Stanford University Press, 2003.
[33]	JACKSON J. Strength of the continental lithosphere: time to abandon the jelly sandwich?[J]. GSA Today, 2002, 12:4-9.
[34]	KOHLSTEDT D L, EVANS B, MACKWELL S J. Strength of the lithosphere: constraints imposed by laboratory experiments[J]. Journal of Geophysical Research: Solid Earth, 1995, 100(B9):17587-17602.
[35]	FRANKEL H R. The continental drift controversy[M]. New York: Cambridge University Press, 2012.
[36]	PAVLENKOVA N I, PAVLENKOVA G A. The upper mantle structure of the Northern Eurasia from seismic profiling with nuclear explosions[J]. NCGT Journal, 2017, 5(1):6-26.
[37]	GUNGY C, PANNING M, ROMANOWICZ B. Global anisotropy and the thickness of continents[J]. Nature, 2003, 422(6933):707-711. DOI URL
[38]	SHAPIRO N M, RICZWOLLER M H, MARESCHAL J C, et al. Lithospheric structure of the Canadian Shield inferred from inversion of surface-wave dispersion with thermodynamic a priori constraints[J]. Geological Society, London, Special Publications, 2004, 239(1):175-194. DOI URL
[39]	REN J S, NIU B G, ZHAO L, et al. Basic ideas of the multisphere tectonics of Earth system[J]. Journal of Geomechanics, 2019, 25(5):607-612 (in Chinese with English abstract).
[40]	WILSON J T. Static or mobile Earth: the current scientific revolution[J]. Tectonophysics, 1969, 7(5):600-601. DOI URL
[41]	MA X Y. Lithospheric dynamics atlas of China [M]. Beijing: China Cartographic Publishing House, 1989(in Chinese).
[42]	YANG W R, GUO T Y, LU Y L, et al. “Opening” and “closing” in the tectonic evolution of China[J]. Earth Science: Journal of Wuhan College of Geology, 1984, 9(3):39-53(in Chinese with English abstract).
[43]	YANG W R, JIANG C F, ZHANG K, et al. Discussions on opening-closing-rotating tectonic system and its forming mechanism and on the dynamic mechanism of plate tectonics[J]. Earth Science Frontiers, 2019, 26(1):337-355(in Chinese with English abstract).
[44]	YANG W R, JIANG C F, ZHANG K, et al. Applying the view of opening-closing-rotating tectonics to study how the Earth’s interior is working[J]. Earth Science Frontiers, 2020, 27(1):204-210 (in Chinese with English abstract).