Water in the Mantle: Effects of Hydration on Physical Properties of Mantle 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: 0337611
• 负责人: Joseph Smyth
• 金额: $ 34.02万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337611&HistoricalAwards=false
• 关键词: Water; Mantle; Effects; Hydration; Physical

One tenth of one weight percent H2O in the minerals of the Transition Zone of the Earth's mantle (400 to 670 km depth) is an amount roughly equal to 800 m. of liquid water over the surface of the planet. It is indeed possible that the volume of Earth's oceans has not been constant, but has been maintained through geologic time by a dynamic exchange with water stored as hydroxyl in the solid silicate phases of the mantle. The nominally anhydrous silicate minerals that make up the upper mantle and Transition Zone (enstatite, olivine, wadsleyite, and ringwoodite) can incorporate up to several weight percent H2O, and seismic velocities in reference Earth models are consistent with significant hydration (~1 percent by weight H2O) of wadsleyite and ringwoodite in a Transition Zone of pyrolite composition. This is a proposal to investigate the stability, crystal chemistry, and physical properties of hydrous enstatite, olivine, wadsleyite, ringwoodite, and perovskite phases that could occur in a hydrous upper mantle and Transition Zone in order to refine estimates of the water content of the Earth's interior. In collaboration with colleagues at the Bavarian Geological Institute (Bayerisches Geoinstitut, BGI), samples of hydrous olivine, enstatite, wadsleyite, ringwoodite and perovskite with a range of hydrogen contents and Mg/Fe ratios will be synthesized. Samples will be characterized by single-crystal X-ray and neutron diffraction, electron microprobe, IR, Raman, and Mossbauer spectroscopies, and transmission electron microscopy. Isothermal compressibilities will be measured by single-crystal X-ray diffraction in the diamond anvil cell at University of Colorado, and by synchrotron powder diffraction at the Advanced Photon Source. The broader impacts of the proposed research include training of graduate and undergraduate students in laboratory geophysics in a university that is distant from major centers of mineral physics research in the US and introducing these students to experiments at larger facilities such as APS. The proposed research project is complementary to on-going field observational geophysics programs (seismology), geophysical modeling and planetary sciences at the University of Colorado. The project has a strong and on-going international component of collaboration of US students and faculty with scientists at the Bavarian Geological Institute in Bayreuth, Germany, University of Oxford, and ISIS neutron diffraction facility (UK). Domestic collaborations of the proposed study include University of Hawaii and Advanced Photon Source (APS) at Argonne National Laboratory.

在地幔过渡带（深度400至670公里）的矿物中，十分之一重量百分比的H2O大约等于800米。液态水的数量。地球海洋的体积确实可能不是恒定的，而是通过与地幔固体硅酸盐相中以羟基形式储存的水进行动态交换而在地质时期得以维持。构成上地幔和过渡带的名义上无水硅酸盐矿物（顽火辉石、橄榄石、华德士来石和林伍德石）可以掺入高达几个重量百分比的H2O，参考地球模型中的地震速度与软锰矿组成的过渡带中华德士来石和林伍德石的显著水合作用（约1%重量H2O）一致。这是一个建议，以调查的稳定性，晶体化学和物理性质的含水顽火辉石，橄榄石，wadsleyite，ringwoodite，和钙钛矿相，可能会发生在一个含水的上地幔和过渡带，以完善地球内部的水含量的估计。将与巴伐利亚地质研究所（Bayerisches Geoinstitut，BGI）的同事合作，合成具有一系列氢含量和Mg/Fe比的含水橄榄石、顽火辉石、沃兹斯利石、林伍德石和钙钛矿样品。样品将通过单晶X射线和中子衍射、电子显微探针、红外光谱、拉曼光谱和穆斯堡尔光谱以及透射电子显微镜进行表征。等温压缩率将在科罗拉多大学的金刚石对顶砧室中通过单晶X射线衍射测量，并在高级光子源中通过同步加速器粉末衍射测量。拟议研究的更广泛影响包括在远离美国主要矿物物理研究中心的大学中对研究生和本科生进行实验室物理学培训，并将这些学生介绍给APS等大型设施的实验。 拟议的研究项目是对科罗拉多大学正在进行的实地观测地球物理学方案（地震学）、地球物理建模和行星科学的补充。该项目有一个强大的和正在进行的国际合作的美国学生和教师与科学家在巴伐利亚地质研究所在拜罗伊特，德国，牛津大学和ISIS中子衍射设施（英国）的组成部分。这项研究的国内合作伙伴包括夏威夷大学和阿贡国家实验室的高级光子源（APS）。