Zircon U-Pb-Hf isotope systematics and whole rock geochemistry of basement rocks of the Bergsträsser Odenwald – implications for pre-Variscan geodynamic evolution of Central Europe

中德结晶带（MGCZ）在揭示新元古代至晚石炭世中欧复杂的前华力西期至同华力西期构造岩浆演化过程中起着关键作用。这种演化的最完整记录保存在Bergsträsser Odenwald的基底岩石中，尽管非常矛盾。虽然有大量的（同位素）地球化学-地质年代学数据和模型存在于Bergsträsser Odenwald的华力西演化（360和320 Ma之间），但关于前华力西事件的信息很少，尽管新的锆石年龄限制了Cadomian基底和志留纪侵入体的碎片。这一新数据仅限于NE-SW向片岩带（所谓的“Schieferzüge”）内的少数样品和地点，形成了变质围岩，主要是华力西花岗岩类（辉长岩到花岗岩）。在本建议中，我们将通过对Bergsträsser Odenwald所有片岩带的变沉积岩和变火成岩进行系统的年代学（同位素）地球化学研究来填补这一知识空白。总体目标是回答以下开放性问题，这些问题代表了研究的三个主要主题：1。Bergsträsser Odenwald可以告诉我们关于MGCZ在中欧前华力西演化中的作用吗？2. Bergsträsser Odenwald的变质沉积岩的地球化学和U-Pb-Hf同位素记录是什么？关于它们的沉积时代和物源，我们可以了解到什么？3. Bergsträsser Odenwald的变质火成岩记录如何与变质沉积岩在年龄和成分上联系起来？为了提出新的限制，我们将对Bergsträsser Odenwald所有片岩带中至少10种变质沉积岩的代表性碎屑锆石群（n>150颗粒）进行系统调查;结合锆石形态学研究、内部结构的BSE/CL成像、原位U-Pb定年和Hf同位素分析。计划对10个变火成岩进行相应的程序。此外，还将从变质沉积岩和变质火成岩中获取大量岩石地球化学数据（主要和微量元素），以便在沉积物沉积和（或）侵位时对其大地构造背景进行严格限制。

The Mid-German Crystalline Zone (MGCZ) plays a key role for unravelling the complex pre- to syn-Variscan tectono-magmatic evolution in central Europe from the Neoproterozoic to the late Carboniferous. The most complete record of this evolution is preserved in basement rocks of the Bergsträsser Odenwald, even though highly ambivalent. While a large number of (isotope)geochemical-geochronological data and models exist for the Variscan evolution of the Bergsträsser Odenwald (between 360 and 320 Ma), information about pre-Variscan events are scarce, although new zircon ages constrain pieces of Cadomian basement and Silurian intrusiva. This new data are limited to a few samples and localities within NE-SW trending schist zones (so called “Schieferzüge”), forming the metamorphosed country rocks to the predominant Variscan granitoids (gabbros to granites). In this proposal we will close this gap of knowledge by performing a systematic geochronological-(isotope)geochemical study on metasedimentary and meta-igneous rocks from all schist belts of the Bergsträsser Odenwald. The overarching aim is to provide answers on the following open questions, which represent the three main topics of the study: 1. What can the Bergsträsser Odenwald tell us about the role of the MGCZ during the pre-Variscan evolution of Central Europe? 2. What is the geochemical and U-Pb-Hf isotope record of metasedimentary rocks of the Bergsträsser Odenwald and what can be learned about their depositional age and provenance? 3. How is the record of meta-igneous rocks of the Bergsträsser Odenwald linked to metasedimentary rocks in age and composition? To place new constraints, we will carry out systematic investigations on representative detrital zircon populations (n>150 grains) from at least 10 metasedimentary rocks from all schist zones of the Bergsträsser Odenwald; combining zircon morphological studies, BSE/CL imaging of internal structures, in-situ U-Pb dating and Hf isotope analyses. A corresponding procedure is planned for 10 meta-igneous rocks. In addition, bulk-rock geochemical data (major and trace elements) will be obtained from metasedimentary rocks, and meta-igneous rocks to place tight constraints on their geotectonic setting by the time of sediment deposition and/or emplacement.