Only a few studies use the potential of metasediments for the extraction of paleogeographical information. However, making use of the geochemistry of metasediments, the depositional environment and climatic conditions can be reconstructed over geological time periods.
This is demonstrated in this project using whole rock analyzes, boron concentrations, trace elements (including rare earth elements) as well as 11B/ 10B - isotope ratios of metamorphic sediments of the Pfitsch-Mörchner basin (Eastern Alps, Austria / Italy), whose precursor rocks were deposited during the mesozoic on top of Variscan basement.
Amongst other things, the geochemical data indicate that the sediments were metasomatically altered after their deposition by extremely saline aqueous solutions (so called brines). These brines, which due to their density can also penetrate deeper sedimentary layers, tend to form in areas with a high evaporation rate and suggest that the sediments were originally deposited under arid to semi-arid conditions in a small, probably lacustrine-fluvial intramontane basin. For this interpretation, the highly fluid-mobile element boron with its great variability in the 11B / 10B isotope ratios plays a decisive role.
Based on further data, as well as petrographic information and field observations, a consistent, conceptual model of the development of this basin and its diagenetic modifications has been established (see figure).
For further information see:
Franz, G., Berryman, E.J., Kutzschbach, M., Meixner, A., Loges, A., and Schultze D. (2021): Geochemistry of metasedimentary rocks and palaeogeographic implications: a case study from a Permo-Triassic metasedimentary cover on Variscan basement, south-western Tauern Window, Austria-Italy. European Journal of Mineralogy, in press.
Berryman et al. (2017), https://doi.org/10.1016/j.lithos.2017.04.008
Prof. Dr. Gerhard Franz
Project scientist TU Berlin:
Dr. Martin Kutzschbach
Other project partners:
Dr. Eleanor Berryman (Canmet Mining, Kannada), Dr. Anselm Loges & Dr. Dina Schultze (FU Berlin), Prof. Dr. Simone Kasemann, Anette Meixner (Uni Bremen & MARUM)