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。 在地质世界中，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结合。在这些矿物质中，水既以 H2O 分子的形式存在，也以它的前体形式存在，即氢原子以氢氧根的形式与氧原子结合。尽管浓度相对较低，通常低于百万分之几百，但这种岩石的体积却很大。这些水的很大一部分融入了我们通常认为无水的矿物质中。这些名义上无水的矿物包括长石、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测定名义上无水矿物的“水”含量。这些标准已在美国和国外广泛传播。这些标准最初是为与红外光谱一起使用而开发的，但现在，另一种称为二次离子质谱法的分析技术可以在较小的区域提供相当或更好的灵敏度。新方法不是自校准的，并且部分依赖于先前为红外光谱开发的标准。 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，长石是少数仍需要使用质谱方法进行研究的主要造岩矿物之一。由于业界对测量陆地和外星样品中长石中的 H 的兴趣，这项工作特别受到关注。它还将研究矿物中氟离子的掺入，目的是改进校准协议，同时系统地研究来自地幔的样品，这些样品先前已表明氢和氟之间存在耦合。这些研究对于解决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。他们解决了哪些相含有痕量“水”以及浓度是多少的问题。它们还有助于了解这些挥发物在整个地球上的空间分布。分析标准还用于解决有关太阳系其他地方（例如月球）是否存在临界挥发物的问题。名义上无水合成矿物和具有技术重要性的相关合成固体中是否存在少量“水”对于设备的运行成功起着重要作用，例如高功率电子电路的支架、数据通信中使用的电光晶体和计算机、手表和电信设备中使用的光纤和计时电路。这项研究将加深人们对微量氢和氟在此类矿物和材料中发挥的重要作用的理解，并将通过制定这些元素的新标准和评估校准协议使国际社会受益。这项工作还为受训成为专业科学家和工程师的学生提供直接参与研究过程的机会。