Dynamic water loss of antigorite by impact process

•Antigorite in meteorites can carry water to hotter regions.•Impact dehydration was investigated experimentally through recovery techniques.•The dehydration depending on porosity and impact pressure is heterogeneous.•High-pressure products were not found in the post-shock antigorite. Impact-induced dehydration of serpentine in primitive meteorites is believed to be a mechanism to provide water in terrestrial planets. Primitive meteorites show a wide range of porosity and it is necessary to know the effect of porosity on the dehydration. In this work we report the dynamic dehydration reaction in powdered samples of antigorite by shock recovery experiments, in which recovered samples were investigated using techniques of X-ray diffractions, electron microscopy, and thermal analyses of shock recovered samples. The present experimental results indicate that the dehydration reaction is weakly pressure-dependent below a peak shock pressure of ∼21GPa and becomes violent at pressures of 21–60GPa. The kinetics was found to be dependent on not only peak shock pressure but also the initial porosity and sample amount. We discuss the heterogeneous dehydration reactions based on the phases identified in the recovered samples, more than previously thought.