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)对揭示中欧新元古代至晚石炭世复杂的前-华力西-华力西期构造岩浆演化起着关键作用。这种演化的最完整记录保存在Bergsträsser Odenwald的基岩中，尽管非常矛盾。尽管存在大量关于Bergsträsser Odenwald(360-320 Ma)华力西演化的(同位素)地球化学-年代学数据和模式，但有关华力西前事件的信息很少，尽管新的锆石年龄约束了卡多米期基底和志留纪侵入岩的碎片。这一新数据仅限于东北-西南向片岩带(所谓的“Schieferzüge”)内的少数样品和地点，形成了变质围岩到主要的华力西花岗岩类(辉长岩到花岗岩)。在这项提议中，我们将通过对Bergsträsser Odenwald所有片岩带的变质沉积岩和变质火成岩进行系统的地质年代学(同位素)地球化学研究来弥合这一知识差距。主要目的是回答以下公开问题，这些问题代表了这项研究的三个主要主题：1.Bergsträsser Odenwald能告诉我们关于MGCZ在中欧华力西前演化过程中所起作用的什么？2.Bergsträsser Odenwald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可以了解到什么？3.Bergsträsser Odenwald变质火成岩记录在年龄和成分上与变质沉积岩有什么联系？为了施加新的限制，我们将对Bergsträsser Odenwald所有片岩带中至少10个变质沉积岩中的具有代表性的碎屑锆石群体(n&gt；150颗粒)进行系统的调查，结合锆石形态研究、内部结构的BSE/CL成像、原位U-Pb测年和Hf同位素分析。计划对10个变质火成岩进行相应的程序。此外，将从变质沉积岩和变质火成岩中获得大量岩石地球化学数据(主要和微量元素)，以严格限制沉积和(或)侵位时的大地构造环境。

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.