P-wave velocities of alkaline olivine basalt at high pressure and temperature and its controlling factors

摘要

SEISMIC wave inversion is one of the most important means for us to recognize the composition and structure of the Earth's interior. Although the experimental techniques of elastic wave velocity measurement at in situ high pressure and temperature develop very fast in recent years and the elastic wave velocities of the Earth's interior material can be measured at pressure up to several hundred kilobars in laboratory, geophysicists are still in short of elastic wave velocity data of the Earth's interior material at high pressure and temperature which is the most important experimental basis for geophysical interpretation. In this note we measure the P-wave velocities of serpentinized alkaline olivine basalt at 2.0-5.0 GPa and 25-1200°C , and then discuss the effects of temperature, pressure and phase transformation as well as serpentine dehydration on its P-wave velocity. A special phenomenon termed as softening effect is found and its mechanism is intepreted by the identification of experimental products.