A Multi-faceted Experimental Constraints on the Dynamic Behavior of MgSiO3 Glass in the Deep Earth’s Interior

Abstract:

The macroscopic properties of densification, viscosity, chemical, and thermal differentiation associated with the structural modification and coordination number changes of silicate glass and melts have received great attention in terms of its linkage to dynamic processes in both deep Earth mantle and other terrestrial planet interiors. Considerable progress has been made over the past few decades in establishing the correlation between structural and properties of liquid silicate; however, there are still many issues to be addressed and improved in the study of silicate melts and glasses. Recent theoretical molecular dynamics (MD) calculation has shown that the most dominant effect of increasing density and bulk modulus is the rearrangement of cation-oxygen bond length and angles, both of which change with evolution of coordination number. Here we take a multifaceted experimental approach to investigate MgSiO₃ glass up to ~70 GPa in diamond anvil cell, by using micro-confocal Raman spectroscopy, angle dispersive X-ray scattering, and Brillouin spectroscopy, to elucidate the connection between structure and macroscopic properties of this super-cooled liquid. Our Raman, X-ray, and Brillouin data show intriguing features at high pressure, provide consistent evidence of a pressure-induced amorphous-amorphous structural modifications in MgSiO₃ glass at ~8, ~20, and ~40 GPa. An insight into the physical and chemical properties of the MgSiO₃ glass with multifaceted approaches will allow us to gain better understanding as to how structure changes and uncover missing links between the structure and physical property relationship, thus provide better constraints on the dynamic behaviors of silicate liquids within the Earth’s deep interior.