Experimental Study of Pressure-induced Structural Changes in Silicate Glasses to >100 GPa

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Silicate magmas are the most efficient carriers of heat and matter throughout Earth's reservoirs, and play an important role in a wide range of geological processes. Silicate magmas are high pressure objects, formed at depth in the present Earth beneath volcanoes, mid-ocean ridges, subduction zones, and hotspots, or in the deep magma ocean in the early Earth. Silicate magmas undergo structural changes at high pressure conditions, and knowledge of the pressure-induced structural changes in silicate magmas is important to understand behavior of silicate magmas in the Earth's deep interior. The investigator developed new double-stage high-pressure apparatus combined with synchrotron X-ray measurement, to study pressure-induced structural changes in silicate glasses, which is an analogue material of silicate magmas, at high pressure conditions to 100 GPa corresponding to the lowermost part of the Earth's mantle. Establishing the new high-pressure experimental technique in a user facility (the beamline 16-BM-B, HPCAT in the Advanced Photon Source) contributes to researches not only in Earth and planetary sciences but also in various scientific fields such as physics and material sciences as well as engineering, and to educational activities for graduate students and young postdoctoral researchers.This project aims to experimentally investigate pressure-induced structural changes in SiO2 and silicate glasses at high pressure conditions to 100 GPa. Large volume sample is vital for accurate measurement of the structure of silicate glasses at high pressure conditions using X-ray diffraction measurement. The investigator developed a new double-stage Paris-Edinburgh type large volume press to generate high pressures to 100 GPa with large sample volume. Structure of silicate glasses will be measured by in situ multi-angle energy dispersive X-ray diffraction at high pressures. This project will provide vital experimental constraints on understanding pressure-induced structural changes in silicate magmas at the pressure conditions of the Earth's deep mantle to the core-mantle boundary by (1) obtaining the first experimental data for structure of silicate glasses to 100 GPa, and (2) establishing relationship between Si-O coordination number and oxygen packing fraction to generalize the pressure-induced structural changes in silicate glasses for application to silicate magmas in the Earth?s deep interior.