Program > Browse abstracts by speaker > Wu Ye

Seismic heterogeneities have been observed throughout the lower mantle. Understanding of the observed seismic velocities requires knowledge of sound velocities of constituent minerals in Earth's interior. As the third most abundant phase of the lower mantle, calcium silicate perovskite (davemaoite) has a significant influence on mineralogical models. Experimental measurements of sound velocities of davemaoite at lower mantle conditions are scarce due to its unquenchable nature. Here, we synthesized quenchable Ti-bearing calcium perovskite as a good analogue for unquenchable davemaoite and investigated its crystal structure, equation of state, refractive index, and sound velocity under high pressure. Tetragonal Ti-bearing calcium perovskite is stable without phase transition up to ~48 GPa but exhibits enhancing octahedral rotation and distortion with increasing pressure. The refractive index of Ti-bearing calcium perovskite increases slightly with pressure ranging from ~1.93 to ~2.04 up to 73 GPa and was used to calculate longitudinal sound velocity (VP) by time-domain Brillouin scattering measurements. Applying density, bulk modulus and its pressure derivative obtained by the constructed equation of state, then transverse sound velocity of Ti-bearing calcium perovskite was derived. Sound velocities of Ti-bearing calcium perovskite are significantly lower than those of CaSiO3, especially transverse sound velocity. Our results strengthen the hypothesis that the presence of calcium perovskite in deeply subducted basaltic crust can explain the low velocity signatures in the lower mantle.