Phase Equilibria and Crystal-Chemistry of Some Calcic Amphiboles

9909452詹金斯角闪石的定量使用推断压力，温度和氧逸度参加变质或部分熔融在地壳中需要富含铁的角闪石的信息。 本研究将以富铁角闪石铁阳起石（Ca_2Fe_5Si_8O_22（OH）_2）为研究对象，采用两种互补的方法：（1）研究CaO-FeO-SiO_2-H_2O化学体系中铁阳起石的稳定性和化学性质;（2）研究铁阳起石与富镁角闪石透闪石固溶体的组分。 本研究的一个特定目标是在已知的压力、温度和氧逸度下合成纯的含铁角闪石。 这些角闪石将通过X射线衍射进行研究，目的是使用Rietveld结构分析来确定角闪石晶体结构中铁和镁的分布，并将通过穆斯堡尔光谱进行研究，以进一步表征阳离子分布并查看是否存在三价铁。 这些极细粒度合成角闪石的其他表征将包括分析透射电子显微镜，以获得单个颗粒的直接化学分析，并评估其晶体结构中存在的缺陷（如果有的话）的量。 从这项研究中，我们将获得重要的见解的热力学性质的端元铁阳起石，测试的假设，三价铁可能大大增加其热稳定性，并确定铁如何影响富镁角闪石的性质。 该研究为认识复杂的角闪石提供了有价值的参考。

9909452JenkinsThe quantitative use of amphiboles for deducing the pressures, temperatures, and oxygen fugacities attending metamorphism or partial melting in the Earth's crust requires information on iron-rich amphiboles. This proposal will focus on the key iron-rich amphibole ferro-actinolite (Ca2Fe5Si8O22(OH)2) using two complementary approaches: (1) investigation of ferro-actinolite stability and chemistry in the chemical system CaO-FeO-SiO2-H2O, and (2) investigation of the ferro-actinolite component in solid solution with the magnesium-rich amphibole tremolite. One particular goal of this research is to synthesize pure iron-bearing amphiboles under known pressure, temperature, and oxygen fugacities. These amphiboles will be studied by X-ray diffraction for the purpose of determining the distribution of iron and magnesium in the crystal structure of amphibole using Rietveld structure analysis and will be studied by Mossbauer spectroscopy to further characterize the cation distribution and to see if ferric iron is present. Additional characterization of these extremely fine-grained synthetic amphiboles will include analytical transmission electron microscopy to obtain direct chemical analyses of individual grains and to assess the amount of defects, if any, that are present in their crystal structure. From this study we will gain important insights into the thermodynamic properties of the end-member ferro-actinolite, test the hypothesis that ferric iron may greatly increase its thermal stability, and determine how iron influences the properties of magnesium-rich amphiboles. This study will provide a valuable point of reference for understanding chemically complex amphiboles.