下地壳流变结构对南海大陆岩石圈破裂形态影响的数值模拟研究

Rifting to drifting transition of the continental lithosphere is an exciting topic in geodynamics. The South China Sea has undergone a complex cycle from continental rifting to seafloor spreading, and is an idea place to analyze the rheological structure of lower crust and the influence on lithospheric rupture. The rheology of the lower crust plays an important role in lithospheric rupture process, and is one of the key factors on the rupture mechanism and evolution model. In this study, the lithospheric rheology model of the South China Sea will be established and evaluated by numerical simulation based on comprehensive analyses of various geophysical data and latest IODP results. The response of different lower crustal rheology to lithospheric rupture will be analyzed through changing the viscosity and the strength of the lower crust. Further study will be made into the rheological structure of lower crust and the rifting-drifting model of lithosphere. This study will provide insights into the lithosphere rupture mechanism of the South China Sea. In addition, it will improve our understanding of the extension types of global passive continental margins.

大陆岩石圈张裂-破裂是当今地球动力学的前沿课题。下地壳的流变性质在岩石圈破裂过程中起着至关重要的控制作用，是研究岩石圈破裂机制及演化模式的关键因素之一。南海新生代经历了从陆缘张裂到海底扩张的复杂的演化过程，保留了丰富的岩石圈破裂信息，是研究下地壳流变结构及其对岩石圈破裂形态影响的理想场所。本研究在各类地球物理探测及最新大洋钻探成果的基础上，利用有限元数值模拟方法，建立南海大陆岩石圈破裂的数值模型；以下地壳的粘滞性为突破口，改变下地壳的流变强度，分析不同下地壳流变对岩石圈破裂的响应；对比南海岩石圈破裂形态，剖析南海大陆岩石圈下地壳的流变性，进而探讨南海大陆岩石圈破裂模式。通过本研究的开展，不仅为进一步理解南海岩石圈破裂机制和演化模式提供理论依据，也将拓展对全球被动大陆边缘伸展机制的认识。

下地壳的流变性质在岩石圈破裂过程中起着至关重要的控制作用，是研究岩石圈破裂机制及演化模式的关键因素之一。本文在各类地球物理探测及最新大洋钻探成果的基础上，利用有限元数值模拟方法，建立南海大陆岩石圈破裂的数值模型；以下地壳的粘滞性为突破口，改变下地壳的流变强度，分析不同下地壳流变对岩石圈破裂的响应；对比南海岩石圈破裂形态，剖析南海大陆岩石圈下地壳的流变性。提出了以南海下地壳作为解耦层存在的张裂模型，并揭示了岩石圈地壳和地幔几乎同时破裂，并快速形成洋壳的张裂-破裂模式。通过本研究的开展，不仅为进一步理解南海岩石圈破裂机制和演化模式提供理论依据，也将拓展对全球被动大陆边缘伸展机制的认识。