Impact volatilization of calcite and anhydrite and the effect on global climate from K/T impact crater at Chicxulub

Citation

Yang, Wenbo (1996) Impact volatilization of calcite and anhydrite and the effect on global climate from K/T impact crater at Chicxulub. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/n3xq-qe28. https://resolver.caltech.edu/CaltechETD:etd-08212009-144428

Abstract

In geophysics and planetary science, it is important to understand the shock devolatilization process of minerals as these represent key elements in our understanding of the formation and evolution of atmosphere and ocean. Shock vaporization experiments were carried out for porous (70% crystal density) anhydrite and porous (54% crystal density) up to 76 and 19 GPa, respectively. Velocity histories of aluminum-LiF window interface, which were driven by the vapor, were measured using velocity interferometer. Incipient and complete vaporization of CaSo4 and CaCO3 criteria have been obtained through thermodynamic calculations in which chemical dissociation or shock melting is taken into account. The incipient and complete vaporization pressures are 81±7 and 155±13 GPa for crystal anhydrite, and 27±1 and 67±6 GPa for porous anhydrite. For porous calcite, the incipient and complete vaporization pressure are 5.4±1.9 and 14.6±3.8 GPa, respectively. For crystal calcite, they are 54±6 and 103±12 GPa, respectively. One-dimensional numerical simulation was used to simulate the measured velocity profiles. The vaporized products can be described by equation, P=(γ-1)ρE, where γ varied as pressure changes. Using the new criteria, the amount of degassed carbon and sulfur have been estimated from Chicxulub impact and their effects on the global temperature have been calculated and discussed. The global warming caused by the degassed CO2 is 0.2-1.1°C and the degassed SO2 may caused a global cooling of is 8.5-16°C. Shock temperature measurements place constraints on high-pressure equation-of-states, permit detection and quantification of phase transformations. A high-sensitivity (24 mv/µW @850nm ), time-resolved six-channel pyrometer has been designed and constructed and used in shock temperature measurements. Due to the high gain of the system, small mineral samples (~5 mm in diameter) can be used in shock temperature experiments. Thermal conductivities of LiF and Al2O3 were measured, for the first time, using this new system, their values are 2-3 orders of magnitude less than theoretical values.

Thesis Files