Study of Single-Crystal Elasticity of Zoisite Ca2Al3Si3O12 (OH) by Brillouin Scattering (CAT#: STEM-ST-0123-YJL)

Introduction

Hydrous phases in subduction zones are potential agents that can transport water to the deep earth. Properties of these hydrous minerals, especially elastic moduli, are necessary to model seismic wave speeds and hence place constraints on recycling of H2O through subduction zones. Zoisite Ca2Al3Si3O12(OH) is a hydrous mineral containing 2 wt% water that is potentially important in subduction zones. It has a large stability fi eld that extends up to 5.0 GPa at 700 °C and 6.6 GPa at 950 °C in the CaO-Al2O3-SiO2-H2O (CASH) system. In the basalt + H2O system, zoisite remains stable to pressures of 3.1 GPa at 650 °C. Breakdown of zoisite at this pressure may be a source of fl uid release at 100–120 km depth depending on the thermal structure of the subducting slab.