地学前缘 ›› 2020, Vol. 27 ›› Issue (3): 254-261.DOI: 10.13745/j.esf.sf.2020.4.2

• 非主题来稿选登 • 上一篇    下一篇

下地壳流变学性质对南大西洋两岸盆地结构不对称性的控制

王殿举1,2(), 李江海1,2,*(), 李一赫3   

  1. 1.北京大学 地球与空间科学学院, 北京 100871
    2.北京大学 石油与天然气研究中心, 北京 100871
    3.山西大同大学 建筑与测绘工程学院, 山西 大同 037003
  • 收稿日期:2020-01-21 修回日期:2020-03-16 出版日期:2020-05-20 发布日期:2020-05-20
  • 通讯作者: 李江海
  • 作者简介:王殿举(1989—),男,博士研究生,地质学专业。E-mail: djwang2015@pku.edu.cn
  • 基金资助:
    国家重大科技专项(2016ZX05033002);国家重大科技专项(2016ZX05033001)

Rheology of the lower crust controls the polarity of conjugated basins asymmetry on the South Atlantic passive margin

WANG Dianju1,2(), LI Jianghai1,2,*(), LI Yihe3   

  1. 1. School of Earth and Space Sciences, Peking University, Beijing 100871, China
    2. Institute of Oil and Gas, Peking University, Beijing 100871, China
    3. College of Architecture and Surveying Engineering, Shanxi Datong University, Datong 037003, China
  • Received:2020-01-21 Revised:2020-03-16 Online:2020-05-20 Published:2020-05-20
  • Contact: LI Jianghai

摘要:

南大西洋两岸被动陆缘盆地蕴藏大量的油气资源,是近年来油气勘探的热点区域。南大西洋两侧共轭盆地的结构存在明显的不对称性,南美侧的桑托斯盆地垂直走向方向的宽度(约850 km)是位于非洲侧的南宽扎盆地(约200 km)的4倍。盆地结构的不对称性导致南大西洋两岸被动陆缘盆地油气分布与成藏规律具有明显的差异,但是盆地结构不对称性的动力学成因目前还存在较大争议。为此开展2D热力学耦合的地球动力学数值模拟实验,数值模拟中采用有限元方法求解黏-弹-塑性连续介质的本构方程。实验结果证明了下地壳流变学性质差异是控制盆地结构的关键因素。当下地壳流变学性质不对称时,在克拉通上发育的盆地往往为狭窄盆地,而在造山带上发育的盆地为宽广盆地。克拉通深厚地壳通过改变软流圈的流动影响地壳破裂和盆地结构。与前人数值模拟结果相比,本文的模型不仅能正演不对称盆地的形成过程,也能预测共轭盆地不对称极性,与南大西洋地质情况能够更好吻合。

关键词: 南大西洋被动陆缘盆地, 不对称扩张, 下地壳, 流变学性质, 数值模拟

Abstract:

The passive continental margin basins on both sides of the South Atlantic contain a large amount of oil and gas resources and became an important target for oil and gas exploration in recent years. The conjugated basins of the South Atlantic passive margin has clear asymmetry, such that the width of the Santos Basin (~850 km) on the South American side is four times that of the South Kwanza Basin (~200 km) on the African side. Basin structural asymmetry leads to significant differences in oil and gas distribution and accumulation. However, the dynamics of this asymmetrical structure is still controversial. Here, we carried out a series of 2D thermodynamic numerical modeling experiments, using finite element method to solve the constitutive equation of the visco-elastic-plastic continuous medium. The results showed that the rheology of the lower crust is the key factor controlling the structure of the basin. When the rheology of the lower crust is asymmetrical, basins developed on the craton are narrower than those on the orogenic fold belts. The deep crust of the craton alters the flow of the asthenosphere, thus controls crustal rupture and basin structure. Compared to the previous modeling results, our model can predict not only the formation process of asymmetric basins, but also the polarity of the conjugated basins to better match the geological conditions of the South Atlantic.

Key words: passive continental margin basin of the South Atlantic, asymmetric expansion, lower crust, rheological properties, numerical simulation

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