Geochronological and geochemical investigations on high-pressure rocks and their host rocks from the Odenwald-Spessart and Erzgebirge basement, Variscides

该项目的重点是确定德国Variscan造山带萨克森图林根带两个高压基底区的变质岩和火成岩的年龄：(i) Odenwald-Spessart基底，它是德国中部结晶带的一部分，（ii） Erzgebirge基底。尽管这两个基底区对于重建Variscan造山运动之前和期间的地球动力学演化具有重要意义，但目前对这两个地区的高压变质作用年龄知之甚少，其范围为Odenwald-Spessart的c. 360 - 330 Ma和Erzgebirge的c. 380 - 330 Ma。计划中的研究旨在通过测定两个基底区不同岩性的锆石、金红石和独居石的U-Pb同位素数据来解决这一不确定性。这些数据应该能提供更精确的信息，关于变质高峰的时间，也可能是关于岩石的冷却历史。此外，锆石的Lu-Hf数据与整个岩石的Sm-Nd同位素数据可用于确定样品的来源（波罗的海或冈瓦纳），并有助于更好地定位中德结晶带内Rheic缝合线的位置，该位置目前仍有争议。此外，还计划对长英质和基性火成岩进行岩石学、地球化学和同位素地球化学研究，以确定这些岩石的源区和前体熔体形成的构造环境。此外，还将确定锆石氧同位素数据，以实现这一目标。Odenwald-Spessart和Erzgebirge基底区以大量晚造山长英质至中火成岩为特征。可以预料，这些火成岩是由于一次大的热异常而形成的。然而，这种异常的起源是完全不清楚的，可能是由羽头引起的，也可能是与瓦里斯坎造山带最终合并期间的板块断裂有关。我们的新数据可能有助于揭示这些大量融化的原因。

The focus of this project is to determine the age of metamorphic and igneous rocks from two high-pressure basement areas in the Saxothuringian Zone of the Variscan Orogen in Germany: (i) the Odenwald-Spessart basement, which is part of the Mid-German Crystalline Zone and, (ii) the Erzgebirge basement. Despite the importance of the two basement areas for the reconstruction of the geodynamic evolution prior to and during the Variscan orogeny, the age of high-pressure metamorphism in both areas is currently only poorly known and ranges from c. 360 to 330 Ma in the Odenwald-Spessart and c. 380 to 330 Ma in the Erzgebirge. The planned study aims to resolve this uncertainty by determining U-Pb isotope data of zircon, rutile and monazite from different lithologies of the two basement areas. The data should provide more precise information about the timing of peak metamorphism and possibly also about the cooling history of the rocks. In addition, zircon Lu-Hf data, together with whole rock Sm-Nd isotope data, can be used to determine the provenance of the samples (either Baltica- or Gondwana-derived) and may help to better locate the position of the Rheic Suture within the Mid-German Crystalline Zone, whose position in currently debated. Furthermore, a petrological, geochemical and isotope geochemical study of felsic and mafic igneous rocks is planned to characterize the source region and the tectonic setting in which the precursor melts of these rocks formed. In addition, zircon oxygen isotope data will also be determined towards achieving this aim. The Odenwald-Spessart and Erzgebirge basement areas are characterized by large volumes of late-orogenic felsic to intermediate igneous rocks. It is to be expected that the igneous rocks formed as a result of a large thermal anomaly. However, the origin of this anomaly is entirely unclear and may have been caused by a plume head or may have been related to slab break-off during the final amalgamation of the Variscan orogen. Our new data may help to shed some light on the cause of these large volumes of melts.