151 / 2023-04-14 21:45:11

Distinct compressional behaviors between silicate melts and glasses at high pressures

高压物理与材料科学 > 高压地球科学-I

Melting of Earth’s silicate mantle is a first-order process that controls the chemical evolution of Earth. By melting, a liquid with a different chemical composition from the residue solid is created and separated under gravity, thereby producing chemically stratified layers, such as the oceanic crust. The existence of partially molten silicate rocks is often believed to be connected to the low seismic velocity anomalies in the mantle. The seismic detection of those melts relies on the compressional properties of melts, which are poorly constrained at high pressures due to technical challenges. Alternatively, silicate glasses are often considered as an analog to silicate melts as they both lack long-range ordering, and thus the glass properties such as the sound velocity are often used interchangeably with those of melts in the geoscience literature. In this study, we performed a series of in-situ sound velocity measurements on both silicate melts and glasses at high-pressure and high-temperature conditions and demonstrate directly that silicate melts and glasses have distinct compressional behaviors. We find silicate glasses undergo complex densifications upon compression and have significantly higher velocities than melts. We have applied our melt velocities to understanding a range of melt related processes in the deep mantles of Earth and the Moon.