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

[909588delaney]本研究的主要目的是评估缅因州西部和新罕布什尔州黑山的变质长岩中含铁、铁和氢的化学平衡。我们将研究三种不同变质等级的含石墨、磁铁矿和赤铁矿岩石样品：石榴石、下硅线岩和星闪岩带。这将允许确定：(1)所有含铁相和Hamong含水相中Fe3+和Fe2+的原位分配系数；(2) Fe3+/Fetotal对温度和fO2的依赖性、Fe3+取代对其他阳离子取代的影响及其对地温学的意义；(3) H和Fe3+电荷平衡变化的阳离子取代。我们还将描述并试图理解单个矿物颗粒内Fe3+/Fetotal的分带以及同一岩石中同一矿物颗粒间Fe3+/Fetotal的变化；最后，我们将评估组合对存在的组成矿物相中Fe3+/Fetotal的影响。这些测量将在标准的1英寸圆形岩石薄片上进行，使用光束尺寸小于10 x 15微米和相对快速的非破坏性技术，同步加速器微xanesspectroscopy （SmX）用于Fe3+/Fetotal，离子微探针（SIMS）用于H，电子微探针（EPMA）用于其他主要元素。有了我们的分析结果，我们可以开始解决组合和晶体化学对Fe2+和Fe3+在偏晶矿物中掺入的竞争影响。我们还希望有效和快速地证明SmX作为岩石学工具的潜在重要性。

9909588DelaneyThe 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.