TEM Studies of Weathering Reactions: The Importance of Mineral Structure, Microstructure and Composition

化学风化具有根本的重要性，因为它是 硅酸盐矿物在高温下形成的过程， 压力被转换成沉积物和土壤的成分。 尽管如此，结构和组成控制的 许多反应的机制和转化率仍然是 不太了解。 该提案描述了两个研究项目 设计用于高分辨率透射电子显微镜 研究风化的微观特征 在母体之间存在重要结构的反应 和矿物产品。 其中第一个涉及水合作用， 角闪石族矿物的氧化。 第二个项目聚焦 钙钛矿风化，其中含水矿物没有形成， 不会发生氧化。 一系列微结构的风化反应 具有接近端元组成的复杂角闪石， 共生和出溶角闪石，以及含 将检查链宽缺陷。 共生角闪石提供了 有机会比较风化率和机制， 相同的理化条件，并评估程度， 这些反应集中在相干应变、缺陷和晶粒 边界 还将研究钙钛矿的风化。 钙钛矿的水热溶解， 核废料储存陶瓷，已被广泛研究，但 自然风化反应在很大程度上被忽视了。 的 化学上简单地转化为TiO 2矿物可能涉及 相当大的结构性遗传。 这些项目的目的是 来阐明自然风化作用的晶体化学细节 过程，从而提高我们对机制的理解， 这些反应的发生。

Chemical weathering is of fundamental importance because it is the process by which silicate minerals formed at high-temperatures and pressures are converted to the constituents of sediments and soils. Despite this, the structural and compositional controls on the mechanisms and rates of transformations of many reactions are still poorly understood. This proposal describes two research projects designed to use high-resolution transmission electron microscopy to investigate the microscopic characteristics of weathering reactions where significant structural exists between the parent and product minerals. The first of these involves hydration and oxidation of amphibole-group minerals. The second project focuses on perovskite weathering, where hydrous minerals are not formed and oxidation does not occur. The weathering reactions of a selection of microstructurally complex amphiboles with close to end-member compositions, intergrown and exsolved amphiboles, and amphiboles containing chain-width defects will be examined. Intergrown amphiboles offer the opportunity to compare weathering rates and mechanisms under the same physiochemical conditions and to evaluate the degree to which reactions are focused by coherency strain, defects, and grain boundaries. The Weathering of perovskite will also be examined. Hydrothermal dissolution of perovskite, a possible component of nuclear waste storage ceramics, has been studied extensively, but the natural weathering reactions have been largely ignored. The chemically simple transformation to TiO2 minerals may involve considerable structural inheritance. The aims these projects are to clarify the crystal chemical details of the natural weathering processes, thus enhancing our understanding of the mechanisms by which these reactions occur.