Effects of Water on Transformation and Deformation Mechanisms in the Mantle Transition Zone

H2O在橄榄石及其高压晶型、黄铁矿和环木石中的高溶解度引起了人们对水在上地幔和过渡带中的影响的极大兴趣。最近对双地震带(孔雀，2001)的解释表明，俯冲的大洋岩石圈也可能携带H2O进入地幔，并可能携带H2O进入过渡带。俯冲岩石圈中的H2O可能对相变机制和动力学以及变形机制和产生的组构产生深远的影响。在橄榄石中，水的存在可能会影响橄榄石-环木石的转化机理，提高反应速率。研究人员建议在多砧座装置中使用氚化圣·卡洛斯橄榄石进行动力学转化实验。他们将使用反应轮缘的宽度来确定生长速度作为温度、压力和D2O含量的函数。透射电子显微镜将被用来描述氚橄榄石的转化机制。用SIMS法测定热压原料和转化原料中的D2O含量。水对橄榄石的塑性变形也有很大的影响。Jung和Karato(2001)表明，高压下简单剪切产生的织物随着H2O含量的增加而变化。利用透射电子显微镜对高压湿条件下变形的橄榄石、水滑石和环木石位错微结构、滑移系统和变形机制进行了研究。

SharpEAR-0208419The high solubility of H2O in olivine and its high-pressure polymorphs, wadsleyite and ringwoodite has led to a great deal of interest in the effects of H2O in the upper mantle and transition zone. Recent interpretations of double seismic zones (Peacock, 2001) suggest that subducting oceanic lithosphere may also carry H2O into the mantle and possibly the transition zone. H2O in subducting lithosphere is likely to have profound effects on phase transformation mechanisms and kinetics as well as on deformation mechanism and resulting fabrics. It is likely that the presence of H2O, as hydrogen in olivine, will influence olivine-ringwoodite transformation mechanisms and enhance reaction rates. The investigators propose to perform kinetic transformation experiments in a multi-anvil apparatus using deuterated San Carlos olivine. They will use the widths of reaction rims to determine growth rates as a function of temperature, pressure and D2O content. TEM will be used to characterize transformation mechanisms in the deuterated olivine. D2O contents of the hot-pressed starting material and the transformed material will be determined with SIMS.H2O has also been shown to have a great influence on the plastic deformation of olivine. Jung and Karato (2001) show that the fabric produced in simple shear at high pressure changes with increasing H2O content. TEM will be used to characterize the dislocation microstructures, slip systems and deformation mechanisms in olivine, wadsleyite and ringwoodite deformed at high pressure under wet conditions.