西南极中-新生代古地磁与板块重建研究进展

Progress in Mesozoic-Cenozoic paleomagnetism and plate reconstruction of West Antarctica

根据西南极已发表的中—新生代古地磁数据,对西南极不同地块进行了古大陆重建。识别出古太平洋板块对西南极构造演化影响广泛的两次构造事件:一是120~100 Ma古太平洋板块内翁通爪哇-马尼希基-希库朗基大火成岩省的喷发与全球板块洋壳扩张速率高峰期引起的西南极瑟斯顿岛-埃茨海岸与东玛丽·伯德地快速南向移动;二是古太平洋-凤凰板块洋中脊在~100 Ma俯冲至西南极之下导致的以罗斯海区域为主的岩石圈伸展、瑟斯顿岛-埃茨海岸与玛丽·伯德地远离东南极以及南极半岛发生南向运动与顺时针旋转。证明太平洋板块俯冲与西南极板块运动的耦合关系。未来需要在西南极获得更多具有准确年代学限制的可靠的古地磁数据,这将对西南极的构造演化模式提供更多的制约,并有助于深入理解南极大陆的构造演化过程、板块生长与裂解的地球动力学机制。

In this study,we summarized paleomagnetic data from West Antarctica and reconstructed the paleoposition of different crustal blocks of West Antarctica.Plate reconstructions identified two widely influenced tectonic events in West Antarctica due to the subduction of the Pacific Plate,including the rapid southward drift of Thurston Island-Eights Coast and Eastern Marie Byrd Land during the eruption of Ontong Java-Manihiki-Hikurangi Large Igneous Provinces and related peak global ocean crust production rate at 120~100 Ma;The lithospheric extension in the Ross Sea region and rapid separation of Thurston Island-Eights Coast and Marie Byrd Land from East Antarctica,as well as the southward drift and clockwise rotation of the Antarctic Peninsula due to the subduction of Pacific-Phoenix Ridge under the Ross sea region at~100 Ma.This supports a co-evolution of the tectonic process between the Pacific Plate subduction and the plate motion in West Antarctica.In the future,we need more reliable paleomagnetic data with precise age constraints to make a more detailed reconstruction of different tectonic processes of West Antarctica.This will help us in understanding the geological evolution of Antarctica,and the geodynamics mechanism of plate growth and plate separation.