青藏高原晚古生代-早中生代冈瓦纳大陆北界的古地磁研究

Tibetan Plateau is a complex tectonic domain，a series terranes rifting between southwest margin of pan-cathysian block and the northern margin of the great southern continent of the Gondwana, then arc-arc/arc-continent collision after the multi-period back-arc spreading. From the north to the south, Tibetan Plateau can be divided into the Early Paleozoic Qinling-Qilian-Kunlun tectonic area of the pan-Cathaysian continent, the late Paleozoic Qiangtang-Sanjiang-Yangtze tectonic area of the Pan-Cathaysian continent and the Late Paleozoic-Mesozoic Gangdise-Himalaya tectonic area on the northern margin of Gondwana. There are four plate suture zones (Indian river Brahmaputra suture zone, Xijr Ulan-Jinshajiang sutural zone, Bangonghu-Nujiang Suture and Shuanghu-Longmu Co suture zone) considered to be the boundary between the two plates of Gondwanaland Eurasia. The mainstream view is that the two continents is sutured by the Bangong-Nujiang suture zone, but new results suggest that Shuanghu-Longmu Co suture zone may be the boundary of the two plates. So that Qiangtang terrane has became a key area to solve the problems mentioned above(the boundary between the two continents). This project chooses the northern boundary of Gondwana during the Late Paleozoic to Early Mesozoic as the key scientific problem. To establish the late Paleozoic-early Mesozoic geomagnetic apparent polar wander path of the northern Qiangtang, southern Qiangtang and Gangdise terranes is our research goal. According to the key points and weak points of current researches, we plan to carry out research to improve the key pole position of the key areas, the key geology stages, for the sake of providing constraints on reconstructing the distribution of lands and seas, basin-mountain coupling and its spatial configuration relationships of the Tibet Plateau in different stages.

近年来古地磁学对青藏高原构造演化的研究取得长足进展，积累了不少重要数据，获得了多个质量较高的“关键极”，为冈瓦纳与欧亚大陆的界线（即冈瓦纳大陆北界）的确定和特提斯演化等重大科学问题提供了定量证据。结果表明，冈瓦纳北界在不同地质时期具有不同的界线且与两大陆之间小型地块运动学特征相联系。但这些古地磁研究还不足以完全刻画出这些小型地块的精细运动学特征，仍处于数据积累阶段。本项目拟延续和拓展前期古地磁研究，以晚古生代-早中生代冈瓦纳大陆北界的厘定为关键科学问题，以建立北羌塘、南羌塘、冈底斯三个块体晚古生代至早中生代古地磁极移曲线为目标，针对目前研究的关键点和薄弱点，补充和完善关键地区、关键时代的关键古地磁极位置数据，为研究青藏高原晚古生代以来不同阶段的海陆分布、盆山耦合及其空间配置，尤其是厘定冈瓦纳与欧亚大陆的界线和研究界线随时间的变化与特提斯演化的关系，提供定量依据。

按照课题计划书，针对近年来古地磁学对青藏高原构造演化的研究取得的进展和积累的数据，本研究查漏补缺，在拉萨地块、南羌塘地块和北羌塘地块获得多个质量较高的“关键极”，为冈瓦纳与欧亚大陆的界线（即冈瓦纳大陆北界）的确定和特提斯演化等重大科学问题提供了定量证据。结果表明，冈瓦纳北界在不同地质时期具有不同的界线且与两大陆之间小型地块运动学特征相联系。但已有的古地磁研究还不足以完全刻画出这些小型地块的精细运动学特征，仍处于数据积累阶段。本项目延续和拓展了前期古地磁研究，以晚古生代-早中生代冈瓦纳大陆北界的厘定为关键科学问题，以建立北羌塘、南羌塘、冈底斯(拉萨)三个块体晚古生代至早中生代古地磁极移曲线为目标，针对研究的关键点和薄弱点，补充和完善了关键地区、关键时代的关键古地磁极位置数据，为研究青藏高原晚古生代以来不同阶段的海陆分布、盆山耦合及其空间配置，尤其是厘定冈瓦纳与欧亚大陆的界线和研究界线随时间的变化与特提斯演化的关系，提供了定量依据。尤其是在确定早二叠世时新特提斯洋的打开、中晚三叠世拉萨块体快速北移等方面，提供了关键性的证据。已按照课题计划书全面完成工作。除了已发表的11篇论文之外，后续还有两篇论文将在2021年发表（已接受）。