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

水对地幔过渡带转化和变形机制的影响

• 批准号: 0208419
• 负责人: Thomas Sharp
• 金额: $ 20.37万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208419&HistoricalAwards=false
• 关键词: Effects; Water; Transformation; Deformation; Mechanisms

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.

H2O在橄榄石及其高压多晶型物、硅铝石和环磷铝石中的高溶解度引起了人们对H2O在上地幔和过渡带中的作用的极大兴趣。最近对双地震带的解释（Peacock，2001年）表明，俯冲的海洋岩石圈也可能携带H2O进入地幔，并可能进入过渡带。俯冲岩石圈中的H2O不仅对岩石圈的变形机制和变形组构有重要影响，而且对岩石圈的相变机制和动力学也有重要影响。这是可能的，H2O的存在下，作为氢的橄榄石，将影响橄榄石ringwoodite转化机制和提高反应速率。研究人员建议使用氘代圣卡洛斯橄榄石在多砧装置中进行动力学转化实验。他们将使用反应边缘的宽度来确定作为温度、压力和D2O含量的函数的生长速率。TEM将被用来表征在氘代橄榄石的转化机制。采用二次离子质谱法测定了热压起始原料和转化后原料中的D2O含量，并研究了H2O对橄榄石塑性变形的影响。Jung和Karato（2001）表明，在高压下简单剪切产生的组构随着H2O含量的增加而变化。透射电镜将被用来表征的位错显微结构，滑移系统和变形机制的橄榄石，wadsleyite和ringwoodite在高压下在潮湿条件下变形。