普里兹湾岩石圈及下伏地幔地球物理-岩石学三维结构及其冈瓦纳裂解的构造意义

Prydz Bay is at the important position of Gondwana breakup in the East Antarctic, which was located at the triple junction of India, Australian and Antarctic plates in the early Mesozoic, and was influenced by the Kerguelen mantle plume. The relationship between Gondwana breakup and the mantle plume is a key scientific problem to understand the dynamic process of the geological evolution of East Antarctic. This research area is a representative area for understanding the interaction mechanism between continental breakup and mantle plume. The geophysical-petrological structure of the lithosphere and sublithospheric upper mantle is the most important evidence of studying the dynamic process of interaction between continental breakup and mantle plume, but there is no such research in Prydz Bay. In this research project, we will use the date of the geophysical and mantle xenoliths petrology in Prydz Bay, through the method of integrated geophysical-petrological modeling to inverse the structure modeling of temperature, density, P wave and S wave velocity, rock chemical composition and so on. The geophysical-petrological 3D model of the lithosphere and sublithospheric upper mantle in Prydz Bay will be constructed for the first time. This reasearch will promote the understanding of the interaction mechanism between the Kerguelen mantle plume and Gondwana breakup, and also has an important enlightenment to the study of the lithosphere breakup process associated with other mantle plumes in the world.

普里兹湾处于东南极洲冈瓦纳大陆裂解的核心位置，在早中生代位于印度、澳大利亚与南极洲板块裂离的三联点，同时受到凯尔盖朗地幔柱的影响。其裂解过程与地幔柱的关系，不仅是了解东南极洲地质演化动力学过程的关键科学问题，而研究区也是认识大陆裂解与地幔柱相互作用机制的代表性区域。岩石圈及下伏地幔的地球物理-岩石学结构是研究大陆裂解和地幔柱相互作用动力学过程最为重要的证据，但目前在普里兹湾缺乏相应研究。本项目拟综合利用普里兹湾的地球物理和地幔捕虏体岩石学资料，通过地球物理-岩石学联合反演的方法，从地幔岩石地球化学组分出发，开展温度、密度、P波和S波速度、岩石化学组分等结构的模拟，首次构建研究区岩石圈及下伏地幔的地球物理-岩石学三维模型，探讨东南极洲冈瓦纳裂解与凯尔盖朗地幔柱的相互作用的动力学过程。该研究将深化对东南极洲冈瓦纳裂解机制的认识，同时对研究全球其他地幔柱相关的岩石圈裂解过程具有重要的启示作用。

普里兹湾位于东南极洲冈瓦纳裂解的三联点位置，是了解东南极地质演化动力学过程的关键，也是认识大陆裂解与地幔柱相互作用机制的全球代表性区域。然而由于恶劣的自然环境导致地质地球物理外业调查难以开展，造成普里兹湾区域岩石圈深部结构研究至今仍然匮乏。为此，本项目综合利用空间重力异常、大地水准面和地形数据，通过多观测联合反演的方法获得包括地壳莫霍面深度、平均地壳密度和岩石圈-软流圈界面的深度等岩石圈深部结构模型。通过对模型的分析，本项目首次发现普利兹湾兰伯特裂谷存在双裂谷现象，而裂谷之间存在着跳跃现象。为了对这种裂谷跳跃现象进行解释，本项目进一步开展了与阿法尔裂谷的对比研究，剖析了兰伯特裂谷与阿法尔裂谷的差异性，并探讨了兰伯特双裂谷形态的成因机制，认为普里兹造山带或Kuunga缝合带的存在可能是形成兰伯特裂谷跳跃的重要因素。通过深入分析普利兹湾与东印度板块大陆边缘的共轭关系，首次揭示了共轭大陆边缘两端双裂谷之间的对应关系。