Fachbereich 14 - Geowissenschaften
Institut für Planetologie
Analytische Planetologie

Stosswelleneffekte in Karbonaten und Sulfaten: Natur - Experiment - Modellirung

Devolatilization of volatile-rich target rocks may occur during impact events. In the context of the 65 Ma Cretaceous/Tertiary (K/T) boundary event, impact-released CO₂ and SO_x likely have changed chemical composition as well as the radiative balance of the atmosphere, and hence, the Earth's climate. Amplitudes of the consequences for the biosphere ("impact winter") are directly linked to the amount of released SO_x and CO₂ (estimates for CO : 260 to 100 000 Gto). In a recent assessment of the Chicxulub case, global warming due to CO₂ input is assumed to be minor compared to cooling due to sulfate aerosols. According to our experimental and modeling results, CaCO₃ seems to be stable up to very high dynamic pressure; the major shock effect is melting. Tests with dolomite and magnesite should help to confirm these findings. - In 2001, the project will focus on CaSO₄. Major goals are

• documentation of shock effects in anhydrite at low dynamic pressures and,
• a better knowledge of the pT-field in which devolatilization of sulfates may occur during cratering.

We perform (1) shock experiments with high-explosive set-ups (100 GPa; T 900 K), (2) fast decompression (15 s) experiments with a multi-anvil press (20 GPa, 2500 K), and (3) evaluate phase boundaries in (static) piston cylinder experiments. (4) A significant part of the project are modeling of the equation of state for CaSO₄ and CaCO₃ at high p, T, and numerical simulation of shock experiments. (5) Characterization of the recovered samples is done optically, with X ray and Raman techniques, by SEM, and TEM.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft

Beteiligte Wissenschaftler:

Agrinier, P. (IPG, Paris), Deutsch, A. (Münster, Leiter), Hornemann, U. (EMI, Efringen-Kirchen), Ivanov, B. A. (RAS Moskau), Langenhorst, F. (BGI Bayreuth)

Veröffentlichungen:

Agrinier, P., Deutsch, A., Schärer, U., Martinez, I. (2001): Fast back-reactions of shock-released CO₂ from carbonates: an experimental approach. Geochim. Cosmochim. Acta 65, 2615-2633.

Ivanov, B. A., Deutsch, A. (2002): The phase diagram of CaCO₃ in relation to shock compression and decomposition. Phys. Earth Planet. Interiors 129, 131-143.

Ivanov, B. A., Langenhorst, F., Deutsch, A., Hornemann, U. (2002): How strong was impact-induced CO₂ degassing in the K/T event? Numerical modeling of laboratory experiments. In: Catastrophic events and Mass Extinctions: Impacts and beyond (eds. Ch. Koeberl and K. G. Mac Leod). Geol. Soc. Amer. Spec. Pap. 356, 587-594.

Langenhorst, F., Boustie, M., Deutsch, A., Hornemann, U., Matignon, Ch., Migault, A., Romain, J. P. (2002): Experimental techniques for the simulation of shock metamorphism: A case study on calcite. Springer series "High-Pressure Shock Compression of Solids V - Shock Chemistry and Meteoritic Applications" (ed. Davison L., Horie Y., Sekine T.), Springer Berlin -Heidelberg - New York; pp 1-25.

Langenhorst, F., Porier, J.-P., Deutsch, A., Hornemann, U. (2002): Experimental approach to generate shock veins in single crystal olivine by shear melting. Meteoritics & Planet. Sci. 37, 1541-1544.