X-Ray Diffraction Study of Chrysotile Compressed in Water under High P–T Conditions of up to 8 GPa and 420°С

Abstract

An in situ X-ray diffraction (XRD) study of chrysotile Mg₃Si₂O₅(OH)₄ compressed in water under conditions of high Р–Т (up to 8 GPa and 420°С) is performed to clarify the effect an aqueous medium has on the stability of this mineral from the group of serpentine recognized as the most important transporter of water in subduction zones. The transformation of chrysotile to OH-chondrodite Mg₅Si₂O₈(OH)₂ (at 5 GPa and 410–420°С) is observed, along with the onset of decomposition to the 10 Å phase. Compared to a dry system, where chrysotile transitions directly to the 10Å phase, an intermediate phase of OH-chondrodite forms first in a chrysotile–water system.