“Stable isotope fractionation processes (∂18O and ∂ 13C) during precipitation of speleothem calcite: systematic investigation in laboratory experiments“
The most widely applied climate proxies in speleothems are stable carbon and oxygen isotopes (∂13C and ∂18O). They can be measured at very high resolution, and in combination with precise absolute dating by the 230Th/U method, they enable palaeoclimate reconstruction at monthly to annual resolution. The interpretation of the stable isotope signals in terms of past temperature and/or precipitation variability, however, is complex because both ∂18O and ∂13C depend on a complicated interplay of various processes in the atmosphere, the soil and karst above the cave and the surface of the stalagmite. Quantitative reconstruction of temperature and precipitation has, thus, remained impossible so far.
We have developed several new laboratory experiments aiming to understand the basic physical and chemical processes influencing the ∂18O and ∂13C signals in speleothems. The experiments are performed under completely controlled conditions, which are very similar to those in natural caves.
In particular, we want to quantify the influence of kinetic isotope fractionation in speleothems and verify and expand recent modelling studies. Furthermore, we will quantitatively determine the corresponding isotope fractionation factors and the time constants of the isotope-geochemical (exchange) reactions. In the framework of further experiments, we will examine the fractionation of "clumped isotopes" and determine distribution coefficients for several trace elements, such as Mg, Sr, Ba, P and U.
Hansen, M., Kluge, T., Scholz, D., 2022 Investigating clumped isotope disequilibrium effects for DIC and CaCO3 during formation of (speleothem) CaCO3: insights from cave analogous laboratory experiments. Geochimica et Cosmochimica Acta, 321, 244-264.
Lindemann, I., Hansen, M., Scholz, D., Breitenbach, S., Hartland, A., 2022 Effects of organic matter complexation on partitioning of transition metals into calcite: Cave-analogue crystal growth experiments. Geochimica et Cosmochimica Acta, 317, 118-137.
Sade, Z., Hegyi, S., Hansen, M., Scholz, D., Halevy, I., 2022 The effects of drip rate and geometry on the isotopic composition of speleothems: Evaluation with an advection-diffusion-reaction model. Geochimica et Cosmochimica Acta, 317, 409-432.
Deininger, M., Hansen, M., Fohlmeister, J., Schröder-Ritzrau, A., Burstyn, Y., Scholz, D., 2021 Are oxygen isotope fractionation factors between calcite and water derived from speleothems systematically biased due to prior calcite precipitation (PCP)?. Geochimica et Cosmochimica Acta, 305, 212-227.
Bajnai, D., Guo, W., Spoetl, C., Coplen, T., Methner, K., Löffler, N., Krsnik, E., Gischler, E., Hansen, M., Henkel, D., Price, G., Raddatz, J., Scholz, D., and Fiebig, J., 2020. Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures. Nature Communications, 11, 4005.
Wassenburg, J. A., Riechelmann, S., Schröder-Ritzrau, A., Riechelmann, D. F. C., Richter, D. K., Immenhauser, A., Terente, M., Constantin, S., Hachenberg, A., Hansen, M. and Scholz, D., 2020. Calcite Mg and Sr partition coefficients in cave environments: Implications for interpreting prior calcite precipitation in speleothems. Geochimica et Cosmochimica Acta 269, 581-596.
Hansen, M., Scholz, D., Schöne, B.R. and Spötl, C., 2019. Simulating speleothem growth in the laboratory: Determination of the stable isotope fractionation (d13C and d18O) between H2O, DIC and CaCO3. Chemical Geology 509, 20-44.
Hansen, M., Scholz, D., Froeschmann, M.-L., Schöne, B. R., and Spötl, C., 2017. Carbon isotope exchange between cave air and thin solution films on speleothem surfaces: Artificial cave experiments and a complete diffusion-reaction model. Geochimica et Cosmochimica Acta 211, 28-47.
Dreybrodt, W., Hansen, M., and Scholz, D., 2016. Processes affecting the stable isotope composition of calcite during precipitation on the surface of stalagmites: Laboratory experiments investigating the isotope exchange between DIC in the solution layer on top of a speleothem and the CO2 of the cave atmosphere. Geochimica et Cosmochimica Acta 174, 247-262.
Hansen, M., Dreybrodt, W., and Scholz, D., 2013. Chemical evolution of dissolved inorganic carbon species flowing in thin water films and its implications for (rapid) degassing of CO2 during speleothem growth. Geochimica et Cosmochimica Acta 107, 242-251.