Water in the Mantle: Effects of Hydration on Physical Properties of Mantel Minerals

地幔中的水：水合作用对地幔矿物物理性质的影响

• 批准号: 0711165
• 负责人: Joseph Smyth
• 金额: $ 33万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711165&HistoricalAwards=false
• 关键词: Water; Mantle; Effects; Hydration; Physical

Intellectual merit. Hydrogen is perhaps the most poorly constrained compositional variable in the bulk Earth, and its geochemical behavior at pressure poorly understood. At low pressures (5 GPa) it is highly incompatible, but its compatibility in mantle minerals increases with pressure (depth) so that its solubility in nominally anhydrous silicates increases to percent levels in deeper upper mantle and transition zone. At such concentrations it has a significant effect on elastic properties of these minerals so that it may be possible to detect the presence of hydration in these regions from seismic studies.This project aims to synthesize and measure physical properties of single-crystal samples of hydrous variants of nominally anhydrous high pressure silicates and to measure properties that can be used to constrain the role of hydrogen in the Earth's mantle. A collection of over 50 samples from previous multi-anvil experiments is available for study. Also, collaborative synthesis experiments on omphacite, wadsleyite II, and perovskite will be conducted using 1200 and 5000 ton presses in at Bayerisches Geoinstitut in Bayreuth, Germany. The effects of hydration on the crystal structure and compressibility of forsterite, wadsleyite and ringwoodite will be measured by single crystal X-ray diffraction and oriented, characterized samples will be provided for measurement of elastic properties using Brillouin spectroscopy. The effect of hydration on thermal expansion of olivine, wadsleyite, ringwoodite, and enstatite will be measured at room pressure and temperatures of 100 to 600 K by single crystal X-ray diffraction. Exploratory experiments to measure compressibility at high temperature by powder or single-crystal synchrotron diffraction will be conducted in collaboration with the group at University of Hawaii. Proton positions in these materials will be investigated by single-crystal neutron diffraction at ISIS (Oxford, UK) or SNS (Oak Ridge). The major objective is to provide constraints from mineral physics on the amount and role of H in the Earth's mantle.Broader impacts. This research will promote extensive inter-institutional and international collaboration and result in exchange of ideas and technology across a broad scientific spectrum. This project also will involve undergraduate and graduate in research as an integral part of the PI's teaching program.

智力上的优点。 氢可能是地球中最不受约束的成分变量，其在压力下的地球化学行为知之甚少。在低压（5 GPa）下，它是高度不相容的，但它在地幔矿物中的相容性随着压力（深度）的增加而增加，因此它在名义上无水硅酸盐中的溶解度在更深的上地幔和过渡带中增加到百分之一水平。在这样的浓度下，它对这些矿物的弹性性质有显著的影响，因此，有可能通过地震研究来检测这些地区是否存在水合作用，该项目旨在合成和测量名义上无水高压硅酸盐的水合变体的单晶样品的物理性质，并测量可用于限制氢在地幔中的作用的性质。从以前的多砧实验收集了50多个样品可供研究。此外，绿辉石，wadsleyite II和钙钛矿的合作合成实验将在德国拜罗伊特的Bayerisches Geoinstitut使用1200和5000吨压力机进行。将通过单晶X射线衍射和定向测量水合作用对镁橄榄石、硅镁石和林伍德石的晶体结构和可压缩性的影响，将提供表征样品用于使用布里渊光谱测量弹性性能。水化作用对橄榄石，wadsleyite，ringwoodite和顽火辉石的热膨胀的影响将在室温下和100至600 K的温度下通过单晶X射线衍射测量。将与夏威夷大学的小组合作，进行利用粉末或单晶同步加速器衍射测量高温下压缩性的探索性实验。这些材料中的质子位置将在ISIS（英国牛津）或SNS（橡树岭）通过单晶中子衍射进行研究。主要目标是提供矿物物理学对地幔中氢的数量和作用的限制。这项研究将促进广泛的机构间和国际合作，并在广泛的科学领域交流思想和技术。这个项目也将涉及研究作为PI的教学计划的一个组成部分的本科生和研究生。