Th-U-Pb age pattern in metamorphic monazites from the Variscan high pressure units in the Saxothuringian Zone (Saxony, NE-Bavaria)

Saxothuringian带的异地域以具有低温、高压、中压和低压变质作用的地质单元为特征。这些单元的压力-温度（P-T）轨迹记录了华力西造山运动过程中石炭纪的大陆碰撞。独居石（（LREE，Th，U，Si，Ca）PO_4）电子探针Th-U-Pb定年方法可用于研究变质区的几个热事件。在这个项目中，云母片岩和片麻岩的薄片中的独居石和石榴石将通过自动化的基于SEM的方法来表征。通过独居石的显微结构原位分析、石榴石中钇的LA-ICPMS分析和地质温压法，可以将P-T轨迹的不同段与时间剖面（岩石年代学）联系起来。石榴石结晶之前和之后的热事件可以通过一个地质单元的几个样品的独居石年龄分布模式来识别。结合P-T轨迹，独居石的年龄分布模式可以重建大陆碰撞推覆叠加和向石炭纪-二叠纪强烈岩浆活动过渡的时空关系。

The Allochthonous Domain of the Saxothuringian Zone is characterised by geological units with ultrahigh temperature, ultrahigh pressure, high pressure, medium pressure and low pressure metamorphism. The pressure-temperature (P-T)-paths of the units recorded a Carboniferous continental collision in the course of the Variscan orogeny. Th-U-Pb dating of monazite ((LREE, Th, U, Si, Ca)PO4) by electron microprobe allows to resolve several thermal events in metamorphic terrains. In this project, monazite and garnet in thin sections of micaschists and gneisses will be characterised by automated SEM-based methods. By the in situ analysis of monazite in microstructures, analysis of Y in garnet by LA-ICPMS and geothermobarometry, distinct segments of the P-T paths can be related to time sections (Petrochronology). Thermal events previous and posterior to a garnet crystallisation can be identified by the monazite age distribution pattern from several samples of a geological unit. In combination to the P-T paths, the monazite age distribution pattern allow the temporal-spatial reconstruction of the continent collision with nappe stacking and the transition to intense Carboniferous-Permian magmatism.