Mineralogical Applications of Transmission Electron Microscopy and Energy-Filtered TEM

该提案是对先前研究项目的更新，该项目涉及应用透射电子显微镜（TEM）和辅助技术来解决矿物学、岩石学和地球化学领域的重要问题。在这个更新中，提出了几个不同的项目，试图理解矿物的晶体化学及其在亚纳米尺度上的反应。这些项目将使用一个新的由nsf支持的300千伏瞬变电磁炉和一个场发射枪，该仪器对普通高分辨率瞬变电磁炉实验具有出色的分辨率，并彻底改变了我们的化学能力。提出的工作的主要重点将是探索如何将这些新的分析能力应用于矿物学和地质学，因为迄今为止，这种技术在地球科学中的应用在很大程度上尚未得到探索。有人建议尝试对一些小于一到几个单位胞的矿物微结构进行直接化学分析。这包括辉石和其他矿物中的层错、双平面和反相边界；钙质白云岩中的C域；辉石岩和长石中spinodal分解的精细化学调节以及在链状硅酸盐的动力学阻溶过程中形成的吉尼尔-普雷斯顿带。此外，将继续努力利用这些新的分析方法实现量化。其他要进行的项目包括探索新合成的含钠和含钾、含有交替的单和双硅酸盐链的高压核孔的结构紊乱和化学变化；硫化物、斑岩和辉长岩的化学组成与上部结构的可能关系铁长石与磁铅石群中其他矿物的有序-无序关系。

VeblenEAR-0073955This proposal is a renewal of a previous research program that involved applications of transmission electron microscopy (TEM) and ancillary techniques to problems important to the fields of mineralogy, petrology, and geochemistry. In this renewal, several diverse projects are proposed with an underlying thread of trying to understand the crystal chemistry of minerals and their reactions at the sub-nanometer scale. These projects will make use of a new NSF-supported, 300-kV TEM with a field-emission gun, an instrument that has excellent resolution for normal high-resolution TEM experiments and has revolutionized our chemical capabilities. The primary emphasis of the work proposed will be the exploration of how these new analytical capabilities can be applied to mineralogy and geology, as applications of this technique to the earth sciences so far have been largely unexplored. It is proposed to attempt direct chemical analysis of a number of mineral microstructures that are in the size range of less than one to a few unit cells. These include stacking faults, twin planes, and antiphase boundaries in pyroxenes and other minerals; the C domains in calcian dolomite; the fine-scale chemical modulations associated with spinodal decompositions in pyroxenes and feldspars; and Guinier-Preston zones that form during kinetically arrested exsolution in chain silicates. In addition, efforts to achieve quantification using these new analytical methods will be continued. Other projects to be pursued include explorations of structural disorder and chemical variation in newly synthesized, Na- and K-bearing, high-pressure pyriboles that contain alternating single and double silicate chains; of possible relationships between chemical composition and superstructures in the sulfides bornite and digenite; of order-disorder relationships in hibonite and other minerals of the magnetoplumbite group.