Shock Compression of Coesite up to 950 GPa

Abstract

Experimental investigations of silica under high pressure and temperature offer crucial insights into modeling of Earth and super-Earths’ interiors. Despite extensive studies on Hugoniots of silica polymorphs like fused-silica (2.20 g/cm³), quartz (2.65 g/cm³) and stishovite (4.29 g/cm³) up to a terapascal, unexplored region of melting and liquid of silica at high pressures is leaved because of the Hugoniots dependence on ambient density. This emphasizes the urgence to supplement the phase diagram to constrain silica properties under extreme conditions. Here, the Hugoniot and shock temperature of coesite (2.92 g/cm³) were studied by laser shock compression experiments up to 950 GPa. Our findings confirm shock-induced superheating in coesite, revealing a higher Grüneisen parameter and lower electrical conductivity compared to those of fused-silica and quartz along an isothermal line (<2 × 10⁴ K). These results suggest unique properties of shocked coesite, which imply a warmer and longer-lived silica magma ocean of earlier rocky-planets.