The Role of Post Shock Heating by Plastic Deformation During Impact Devolatilization of Calcite (CaCO3)

An accurate understanding of the relationship between the impact conditions and the degree of shock induced thermal metamorphism in meteorites allows the impact environment in the early Solar System to be understood. A recent hydrocode has revealed that impact heating is much higher than previously thought. This is because plastic deformation of the shocked rocks causes further heating during decompression, which is termed post shock heating. Here we compare impact simulations with laboratory experiments on the impact devolatilization of calcite to investigate whether the post shock heating is also significant in natural samples. We calculated the mass of CO₂ produced from the calcite, based on thermodynamics. We found that iSALE can reproduce the devolatilization behavior for rocks with the strength of calcite. In contrast, the calculated masses of CO₂ at lower rock strengths are systematically smaller than the experimental values. Our results require a reassessment of the interpretation of thermal metamorphism in meteorites.