The evolution of the European Crust – U-Pb, Pb, Hf, and O isotope systematics of detrital zircon, rutile and K-feldspar from the sediments of major European rivers

• Applicant: Professor Dr. Hans Heinrich Bahlburg
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397638449

Large river system drain wide continental areas spanning different geotectonic domains. The detritus accumulating in the lower reaches of such systems ideally reflects the entirety of the lithological spectra constituting the geotectonic domains. Considering sorting and transport effects, river sediments reflect the composition of the respective continental crust and therefore allow for the analysis of its evolution. This analysis rests mainly on minerals that permit the reconstruction of the isotopic and temporal evolution of the crust. We propose a study of 15 major European river systems to study the geochemical evolution of the European continental crust. We will sample the rivers in the lower reaches to obtain U-Pb age dates from zircon and rutile by LA ICPMS. Both minerals are very resilient under weathering and transport conditions. Zircon is derived originally mainly from felsic to intermediate magmatic and metamorphic rocks whereas rutile may be derived also from mafic metamorphic rocks. Therefore rutile allows for the consideration of the role of more mafic lithologies. We will combine these analyses with the study of O and Hf isotopes in zircon by SHRIMP II and LA ICPMS, respectively. Both isotope systems combined allow for the crucial distinction between juvenile and recycled crustal components. Finally, the Pb isotope analysis of K-feldspar by LA ICPMS will be used to evaluate the recycled component in the detrital zircon data and the climatic influence on the detrital compositions as K-feldspar is a common detrital mineral in first-cycle sands.The primary objective of our study is the analysis of the geochemical evolution of the European continental crust in terms of the temporally changing relative contribution of juvenile additions and recycling of older crust. We will assess the evolution of the European continental crust and its relation to the known supercontinent cycles. We will test the alleged bias of the global U-Pb zircon age and supercontinent record towards collisional granitoids of collisional orogens. We will compare our data with the respective record of the Phanerozoic Andes, a long-standing accretionary orogen. The zircon record of the Andes region reflects the same supercontinent cycles as the collisional orogens commonly favored in the definition of such cycles. We will therefore also test our hypothesis that the alleged bias of the zircon and supercontinent record towards granitoids of interior orogens does not universally apply.

• DFG Programme: Research Grants