Rotation and extension of the crust in SE-Tibet

了解青藏高原隆升等大尺度构造过程对恢复古气候演化具有重要意义。高原形成的机制一直备受争议，但量化程度很低。我们建议对块体旋转模式和长波长褶皱进行古地磁研究，以帮助更好地了解主要地球动力学过程的机制和时间。利用了与末次冷却有关的低品位变质岩的二次热磁剩磁。剩磁采集的年代测定和剩磁特征的确定需要进行热年代学和地质测温研究。在我们的研究中，我们将重点放在西藏东南部，这是东部构造带周围横向质量转移的关键区域，到目前为止，这里只做了很少的工作。我们将包括已经存在的来自南部高原和西部和中部喜马拉雅山脉的古地磁结果，以及来自GPS测量的最近水平位移和第四纪走滑速率的信息。古地磁结果将被用来确定横向质量转移的开始，更好地约束第一个隆起阶段的持续时间，以及用于量化横向质量转移速率。此外，我们还将研究两个地堑构造的年代学和伸展速率，这两个构造似乎代表了旋转的地壳尺度地块之间的边界。这将对地块旋转模式的几何形状和时间提供独立的约束，并使我们能够更好地评估地壳减薄对高原高程历史的重要性。

Understanding large-scale tectonic processes such as uplift of the Tibetan Plateau is important for reconstructing the palaeoclimatic evolution. The mechanism of plateau formation is highly debated and poorly quantified. We propose a palaeomagnetic study of block rotation patterns and long-wavelength folding, to contribute to a better understanding of the mechanism and timing of major geodynamic processes. Secondary thermomagnetic remanences of low-grade metasediments related to last cooling are used. Dating of remanence acquisition and determination of the remanence character require thermochronologic and geothermometric investigations. For our study we focus on SE-Tibet, a key area of lateral mass transfer around the eastern syntaxis, where only very little work has been done until present. We will include the already existing palaeomagnetic results from the southern plateau and the Himalaya in the western and central part, and also information on recent horizontal displacements from GPS measurements and Quaternary strike-slip rates. Palaeomagnetic results will be used to define the onset of lateral mass transfer and better constrain the duration of the first uplift phase as well as for quantification of lateral mass transfer rates. Additionally, we will investigate the chronology and rates of extension in two graben structures that appear to represent the boundaries between rotating crustal-scale blocks. This will provide independent constraints on the geometry and timing of block rotation patterns, and allow us to better assess the importance of crustal thinning for the plateau's elevation history.