Collaborative Research: RUI: Chemical Equilibria Involving Iron and Hydrogen in Metapelites From Western Maine

9909587 Dyr这项研究的主要目标是评估缅因州西部的变质泥质岩和新罕布夏州Black Mountain的相关岩石中涉及亚铁和铁铁以及氢的化学平衡。我们将研究三种不同变质级别的含石墨、磁铁矿和赤铁矿的岩石样品：石榴石、下硅线石和球铁矿带。这将允许测定：(1)Fe~(3+)和Fe~(2+)在所有含铁相间和H~(2+)在水合相间的原位分配系数；(2)Fe~(3+)/Fe~(3+)的温度和fO_2关系以及Fe~(3+)取代对其他阳离子取代的影响；(3)H和Fe~(3+)的电荷平衡变化的阳离子取代。我们还将描述和了解单个矿物颗粒内的Fe3+/全量分带以及同一岩石中同一矿物颗粒间Fe3+/全量的变化；最终，我们将评估组合对组成矿物相中Fe3+/全量的影响。这些测量将在标准的1英寸圆形岩石薄片上进行，使用小于10×15微米的束流尺寸和相对快速、无损的同步微X射线能谱(SMX)技术(Fe3+/Fettal)、离子探针(SIMS)(H)和电子探针(EPMA)等主要元素。有了我们的分析结果，我们可以开始讨论组装和晶体化学对Fe2+和Fe3+在变云母矿物中的竞争作用。我们还希望有效和快速地展示SMX作为岩石学工具的潜在重要性。

9909587DyarThe primary goal of this research is to evaluate the chemical equilibriainvolving ferrous and ferric iron and hydrogen in metapelitic rocks fromwestern Maine and related rocks at Black Mountain, New Hampshire. We willstudy samples from graphite, magnetite, and hematite-bearing rocks at threedifferent metamorphic grades: garnet, lower sillimanite, and staurolitezone. This will permit the determination of: (1) in situ partitioncoefficients for Fe3+ and Fe2+ among all the Fe-bearing phases and for Hamong hydrous phases; (2) the temperature and fO2 dependence ofFe3+/Fetotal and effects of Fe3+ substitution on other cation substitutionsplus their implications for geothermometry; and (3) the cationsubstitutions that charge balance variations of H and Fe3+. We will alsocharacterize and seek to understand Fe3+/Fetotal zoning within individualmineral grains as well as variation of Fe3+/Fetotal among grains of thesame mineral in the same rock; ultimately, we will assess the effects ofassemblage on Fe3+/Fetotal in the constituent mineral phases present. These measurements will be made on standard 1" round petrographic thinsections using beam sizes of less than 10 x 15 micrometers and therelatively rapid, non-destructive techniques of synchrotron microXANESspectroscopy (SmX) for Fe3+/Fetotal, ion microprobe (SIMS) for H, and theelectron microprobe (EPMA) for other major elements. With our analyticalresults in hand, we can begin to address the competing effects ofassemblage and crystal chemistry on the incorporation of Fe2+ and Fe3+ inmetapelite minerals. We also hope to effectively and quickly demonstratethe potential importance of SmX as a petrologic tool.