Wasserisotopiemessung an Fluideinschlüssen von Speläothemen mittels CRDS - Untersuchung der Beziehung des Karbonat-d18O-Werts zu klimatischen Schwankungen
Mineralogie, Petrologie und Geochemie
Zusammenfassung der Projektergebnisse
The fluid inclusion line established at Heidelberg University makes it possible to perform fast and precise analyses of the stable isotope ratios of tiny fluid inclusion water amounts (>0.2 µl) through absorption spectroscopy. There exist only a limited number of facilities worldwide that are capable of extracting and analysing small water amounts in the microliter range from speleothem fluid inclusions. The methodological studies that have been carried out, such as the analysis of the adsorption effect, are unique for this measurement system with a saturated water vapour background. We could show that the adsorption of water molecules on the freshly produced calcite surface does not influence the isotope signal of the sample and, thus, renders the method very robust. Furthermore, the application of water-filled glass capillaries is a simple and reliable method for inter-laboratory comparison, which allows assessing the precision and accuracy of different analytical systems (mass spectrometry and absorption spectroscopy). The analysis of a stalagmite from Romania exemplified that the application of the δ2H/T relationship can be used to very precisely reconstruct paleo-temperatures. General precondition for this application is a well-defined δ2H/T relationship for the cave location. Beyond thermometry, significant deviations of the stable water isotopes from the GMWL were detected in two well-investigated stalagmites from Germany and Puerto Rico. A stronger fractionation of oxygen compared to hydrogen isotopes in some of the related samples with a slope < 8 has not been documented yet in fluid inclusion studies. The same effect is observed in these two stalagmites, despite belonging to different climatic regions. This observation with consistent low δ2H-δ18O slopes (2-4) indicates that fractionation due to evaporation may be important in the fluid inclusions of some speleothems. In turn, the relative position of the fluid inclusion isotope data with respect to the GMWL could be used to independently specify the climatic conditions during stalagmite formation: a position on the GMWL indicates rather humid climatic conditions, whereas a significant deviation with slopes close to 4 indicates a relatively dry climate with evaporation. The aspect of evaporation has been mostly excluded in stalagmite studies based on humidity aspects. This result was a big surprise and will be published timely as this finding constitutes an important contribution for the characterization of the CaCO3-H2O-CO2 system in the cave environment and can help to improve the understanding of kinetic fractionation during calcite precipitation. In summary, the analysis method presented here offers a fast, efficient and cost-effective approach to analyse stable water isotopes in fluid inclusions of speleothems and should be routinely integrated in the analysis of stalagmite samples and related paleoclimate studies.
Projektbezogene Publikationen (Auswahl)
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2016. Influence of isotopic reequilibration on speleothems and fluid inclusion, Geophysical Research Abstracts Vol. 18, EGU 2016-13726, 2016
Kluge, T., Haderlein, A., Weißbach, T.
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2016. Paleoclimate reconstruction from speleothem fluid inclusions - are isotope ratios really preserved? Goldschmidt conference 2016: Goldschmidt Abstracts, 1548, 2016
Kluge, T., Haderlein, A., Weißbach, T.
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2019. Reproducibility and accuracy of fluid inclusion isotope studies using the CRDS technique. Goldschmidt conference abstracts 3663, 2019
Weißbach, T., Kluge, T., Fohlmeister, J., Riechelmann, D., Vonhof, H.
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2020. A comparison of IRMS and CRDS techniques for isotope analysis of fluid inclusion water, Rapid. Commun. Mass Spec
de Graaf, S., Vonhof, H., Weißbach, T., Wassenburg, J., Elan, L., Kluge, T., Haug, G.
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2020. Spectroscopic isotope ratio analysis on speleothem fluid inclusions - analytics and paleoclimatic case studies. Heidelberg University, p. 225
Weißbach, T.
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2020. Speleothem record from Pentadactylos cave (Cyprus): high-resolution insight into climatic variations during MIS 6 and MIS 5. Geophysical Research Abstracts, EGU 2020-11105
Nehme, C., Verheyden, S., Kluge, T., Weißbach, T., Nader, F., Gucel, S., Chralambidou, I., Saterfield, L., Cheng, H., Edwards, L., Claeys, P.
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2020. Temperature reconstruction using CRDS fluid inclusion analysis from a late Holocene stalagmite (Romania). The Karst Record IX, abstract volume, 2020
Weißbach, T., Kluge, T., Juhl, M.-C., Warken, S., Fohlmeister, J., Riechelmann, D.F.C., Vonhof, H.
