Chemistry and Bonding of Grain Boundary Carbon in Mantle Xenoliths

地幔捕虏体中晶界碳的化学和成键

• 批准号: 0087714
• 负责人: Laurence Garvie
• 金额: $ 10.6万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-01-01 至 2002-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0087714&HistoricalAwards=false
• 关键词: Chemistry; Bonding; Grain; Boundary; Carbon

GarvieEAR-0087714Electrical conductivities from laboratory measurements and geophysical data are often at odds, since common crustal silicates are significantly more insulating than are crustal conductivities determined by geophysical models. It has been suggested that the electrical conductivity of these rocks is in part controlled by intergranular C. The nature of this C is poorly known. Electron optical, diffraction, and spectroscopic studies reveal heterogeneous materials, with chemical and structural variations at the nanometer scale. The origin of the intergranular C is also in dispute. The intergranular C contains a host of elements, most notably Cl. It is unknown whether any of these elements are associated with graphite intercalation compounds (GIC), separate discrete mineral inclusions, or as organic compounds. The proposed study will focus on the chemistry and mineralogy of grain-boundary C in mantle xenoliths from alkali basalts, kimberlites, and samples recovered from the German continental scientific drilling site (KTB). Particular attention will be directed towards determining the local chemical composition of the C, with the view of identifying the hosts of the associated elements. It is necessary to ascertain the presence of GICs in the intergranular C because of their significant physical and chemical properties. Understanding the structure-property relationships of intergranular C requires a knowledge of the microstructure, including a quantitative appreciation of chemical bonding and its spatial distribution. Structural information will be revealed by high resolution transmission electron microscopy (HRTEM). The proposal describes studies that rely on the high-energy resolution and brightness of a TEM equipped with a field-emission gun (FEG) electron source and the high sensitivity of the new Gatan 766 DigiPEELS spectrometer. This experimental setup provides nanometer-scale, trace element, analytical capabilities. Electron energy-loss spectroscopy (EELS) with a TEM is an established spectroscopic technique that provides qualitative and quantitative chemical information. EELS is a highly sensitive microanalytical tool, and offers an advantage over energy dispersive x-ray spectroscopy (EDXS) for analyzing light elements.

Garviews-0087714实验室测量的电导率和地球物理数据通常不一致，因为普通地壳硅酸盐的绝缘性明显高于地球物理模型确定的地壳电导率。这些岩石的电导率部分受粒间碳的控制。这个C的性质知之甚少。电子光学，衍射和光谱研究揭示了异质材料，在纳米尺度上的化学和结构变化。晶间C的起源也存在争议。粒间碳含有大量元素，最显著的是Cl。目前还不清楚这些元素是否与石墨层间化合物（GIC），独立的离散矿物包裹体或有机化合物有关。拟议的研究将侧重于碱性玄武岩，金伯利岩和从德国大陆科学钻探现场（KTB）回收的样品中的地幔捕虏体中的晶界C的化学和矿物学。将特别注意确定C的局部化学成分，以确定相关元素的宿主。晶间碳具有重要的物理和化学性质，因此有必要确定晶间碳中是否存在晶间碳。理解晶间碳的结构-性质关系需要微观结构的知识，包括化学键及其空间分布的定量评价。结构信息将通过高分辨率透射电子显微镜（HRTEM）显示。 该提案描述了依赖于配备场发射枪（FEG）电子源的TEM的高能量分辨率和亮度以及新型Gatan 766 DigiPEELS光谱仪的高灵敏度的研究。该实验装置提供了纳米级的痕量元素分析能力。带有TEM的电子能量损失光谱（EELS）是一种成熟的光谱技术，可提供定性和定量的化学信息。EELS是一种高灵敏度的微量分析工具，在分析轻元素方面优于能量色散X射线光谱法（EDXS）。