Light Element Incorporation in Nominally Anhydrous Minerals

名义无水矿物中的轻元素掺入

• 批准号: 1322082
• 负责人: George Rossman
• 金额: $ 34.32万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322082&HistoricalAwards=false
• 关键词: Light; Element; Incorporation; Nominally; Anhydrous

Water is essential not only to life, but also to geological processes such as volcanic eruption, magma melting and rising, and rock deformation. In the geological world, a major reservoir of water is tied up in solid rock deep in the Earth where it is chemically bound to the minerals. In these minerals, water is present both as the H2O molecule, and also as its precursor, the hydrogen atom bound to oxygen atoms in the form of hydroxide groups. Although the concentrations are relatively low, usually less than a few hundred parts per million, the volume of this rock is great. A large proportion of this water is incorporated into minerals we normally think of as anhydrous. These nominally anhydrous minerals include feldspars, quartz, olivine, garnets, and pyroxenes. For a couple decades, the Caltech lab has developed the first generation of analytical standards for determining the 'water' content of nominally anhydrous minerals using a variety of analytical tools. These standards have seen wide distribution across the United States and abroad. The standards were originally developed for use with infrared spectroscopy, but now, another analytical technique known as secondary ion mass spectrometry offers comparable or better sensitivity on smaller areas. The new method is not self-calibrating and has relied, in part, on the standards previously developed for infrared spectroscopy. In some ways, the first generation of standards is proving less than optimal in view of the improved spatial sensitivity offered by the new methods. The proposed study will re-evaluate existing standards and develop new, second generation ones to optimize the new-found analytical capabilities. Part of this work will involve an extensive characterization of feldspars, one of the few major rock-forming minerals that still need to be investigated using the mass spectrometry methods. This effort is particularly topical due to interest from the community in measuring H in feldspars from both terrestrial and extraterrestrial samples. It will also study fluorine ion incorporation in minerals with the goal of improving calibration protocols while systematically studying samples derived from the Earth's mantle were indications of a coupling between hydrogen and fluorine have been previously suggested. These studies are critical to the ultimate fundamental question of where the important volatile components such as water reside in the earth and how they influence the properties of rocks and minerals. They address the questions of which phases contain trace 'water' and at what concentrations. They also contribute to understanding the spatial distribution of these volatiles throughout our planet. The analytical standards are also used to address questions about the existence of critical volatiles elsewhere in the solar system such as the moon. The presence or absence of small amounts of 'water' in nominally anhydrous synthetic minerals and related synthetic solids of technological importance plays an important role in operational success of devices such as supports for high power electronic circuits, electro-optic crystals used in data communication and fiber optics, and timing circuits used in computers, watches and telecommunication devices. This research will broaden the communities understanding of the important role that trace amounts of hydrogen and fluorine play in such minerals and materials, and will benefit the international community through the development of new standards and assessment of calibration protocols for these elements. This work also provides opportunities for direct participation in the research process by students training to be professional scientists and engineers.

水不仅对生命至关重要，而且对火山喷发、岩浆融化和上升、岩石变形等地质过程也至关重要。在地质学的世界里，一个主要的水库被束缚在地球深处的固体岩石中，在那里它与矿物质发生化学反应。在这些矿物质中，水既以H2O分子的形式存在，也以它的前体——氢原子以氢氧根的形式与氧原子结合——的形式存在。虽然浓度相对较低，通常不到百万分之几百，但这种岩石的体积很大。这些水的很大一部分被合并成矿物质，我们通常认为是无水的。这些名义上的无水矿物包括长石、石英、橄榄石、石榴石和辉石。几十年来，加州理工学院实验室开发了第一代分析标准，用于使用各种分析工具确定名义上无水矿物的“水”含量。这些标准在美国和国外得到了广泛的应用。这些标准最初是为红外光谱而开发的，但现在，另一种被称为二次离子质谱法的分析技术在较小的区域上提供了相当或更好的灵敏度。这种新方法不是自校准的，而是部分依赖于以前为红外光谱制定的标准。在某些方面，鉴于新方法提供的改进的空间灵敏度，第一代标准被证明不是最佳的。拟议的研究将重新评估现有标准，并开发新的第二代标准，以优化新发现的分析能力。这项工作的一部分将涉及长石的广泛表征，长石是仍需要使用质谱法研究的少数主要造岩矿物之一。由于社区对测量地球和地外样本长石中的H感兴趣，这项工作特别受关注。它还将研究矿物中的氟离子结合，目的是改进校准方案，同时系统地研究来自地幔的样品，因为以前曾提出氢和氟之间存在耦合的迹象。这些研究对于解决诸如水等重要挥发性成分在地球中的位置以及它们如何影响岩石和矿物的性质这一最终基本问题至关重要。它们解决了哪些阶段含有微量“水”以及其浓度的问题。它们还有助于了解这些挥发物在我们星球上的空间分布。分析标准也用于解决太阳系其他地方（如月球）是否存在关键挥发物的问题。在名义上无水的合成矿物和相关的具有重要技术意义的合成固体中是否存在少量的“水”，对诸如高功率电子电路、数据通信和光纤中使用的电光晶体以及计算机、手表和电信设备中使用的定时电路等设备的运行成功起着重要作用。这项研究将扩大社会对微量氢和氟在这类矿物和材料中所起重要作用的认识，并将通过为这些元素制定新的标准和评估校准规程而使国际社会受益。这项工作还为培养成为专业科学家和工程师的学生直接参与研究过程提供了机会。