Water in Nominally Anhydrous Minerals of the Lower Crust

知识价值。长期以来，人们一直认为下地壳和地幔几乎是无水区域，与此相反，人们越来越认识到，名义上的无水矿物（NAMs，即那些水不属于矿物配方化学计量部分的矿物）可能构成地球上大量的水。室内。水在许多基本的地球内部过程中起着关键作用。例如，尽管估计的丰度很低，但地幔中的水被认为会影响对流和化学成分的循环、行星流变学和变形以及地震速度特征。地球吗?地壳主要由长石和石英组成，可能含有大量的水（高达百万分之几百），因此构成了一个主要的行星水库。为了量化下地壳中水的含量和分布，本项目重点研究了萨斯喀彻温省北部的阿萨巴斯卡麻粒岩地体，暴露了约20,000平方公里的代表性下地壳岩性。水的浓度将被测量，并利用傅里叶变换红外光谱（FTIR）绘制。阴极发光成像也将用于识别石英中保存的原生分带，这可能与原生流体包裹体的定位有关。这些岩石中水的丰度和分布将被量化，这些知识将用于评估水对地壳过程影响的以下方面：NAMs中的水在多大程度上起到促进下地壳部分融化的通量作用？在多大程度上，看似只涉及无水的变质反应？矿物质实际上依赖于不结盟运动反应物的逐渐脱水？从NAMs中释放出来的水对地壳变形的影响是什么？更广泛的影响。除了为研究生和本科生提供培训和经济支持的典型社会效益外，该项目还提供了与加拿大地质调查局和萨斯喀彻温省地质调查局的成员在实地环境中继续进行丰富的思想交流的机会，并为加拿大斯托尼·拉皮兹偏远城镇的居民举办晚间地质论坛。该研究区域将来将成为地球物理学家和地质学家的现场论坛。研究成果也将在各种外联活动中分享。例如，将在加拿大报纸上发表一系列文章，重点介绍阿萨巴斯卡麻粒岩地体的地质情况；这些是基于对PI Williams的采访。

Intellectual Merit. In contrast to long-held opinion that the lower crust and mantle are nearly anhydrous domains, it is increasingly recognized that nominally anhydrous minerals (NAMs; i.e., those for which water is not a stoichiometric part of the mineral formula) potentially constitute a significant inventory of water in the Earth?s interior. Water plays a critical role in many fundamental interior Earth processes. For example, despite low estimated abundance, water in the mantle it is thought to influence convection and recycling of chemical components, planetary rheology and deformation, and seismic velocity characteristics. The Earth?s crust is dominated by feldspar and quartz that may host significant amounts (up to hundreds of ppm) of water, thus comprising a major planetary water reservoir. In an attempt to quantify the content and distribution of water in the lower crust, this project focuses on a study of the Athabasca Granulite Terrane, northern Saskatchewan, that exposes some ~20,000 km2 of representative lower crustal lithologies. Concentrations of water will be measured and mapped using Fourier transform infrared (FTIR) spectroscopy. Cathodoluminescence imaging also will be used to identify preserved primary zoning in quartz that might correlate with localization of primary fluid inclusions. The abundance and distribution of water in these rocks will be quantified and this knowledge used to assess the following aspects of the influence of water on crustal processes: [1] to what extent does water in NAMs act as a flux to promote partial melting in the lower crust?, [2] to what extent are metamorphic reactions that seemingly involve only ?anhydrous? minerals actually dependent on progressive dehydration of NAM reactants?, and [3] to what does water liberated from NAMs influence crustal deformation? Broader Impacts. In addition to the typical societal benefits of training and financially supporting graduate and undergraduate students, this project offers the opportunity of continuing a rich exchange of ideas in a field setting with members of the Geologic Survey of Canada and the Saskatchewan Geologic Survey, and to conduct evening geologic forums for the residents of the remote town of Stony Rapids, Canada. The study area will be the site of a field forum for geophysicists and geologists in the future. Research results will also be shared in various outreach activities. For example, a series of articles is to be published in Canadian newspapers, focusing on the geology of the Athabasca Granulite Terrane; these are based on interviews with PI Williams.