Kinetics and Mechanism of Olivine Phase Transformations: Implications for Subduction

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

Weidner 0001217 A knowledge of the kinetics and mechanisms of the transformation of olivine to its high-pressure polymorphs wadsleyite and ringwoodite under subduction zone conditions is important for understanding the dynamics of subduction, the mechanism of deep earthquakes, and the mechanical properties of subducting lithosphere. The goal of this research is to study the transformational characteristics of olivine to its high-pressure polymorphs in the pressure and temperature domain of a subducting slab (i.e., high pressures and relatively low temperatures). The investigaotors will utilize a synchrotron x-radiation source coupled with a multi-anvil high-pressure system to conduct experimental studies in the pressure range up to 20 Gpa and a wide range of temperature. The transformation kinetics and mechanisms will be examined as a function of grain size, deviatoric stress, water content, and defect concentration (i.e., oxygen fugacity; hot-pressing vs. cold-pressing). Transformation mechanisms will be investigated through TEM analysis of recovered partially-transformed samples. The investigators will determine the effect of deviatoric stress on the transformation mechanisms and will also quantify the structural properties of high-pressure phases with time through structural refinements using monochromatic x-rays.