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

合作研究：缅因州西部变泥岩中涉及铁和氢的化学平衡

• 批准号: 9902857
• 负责人: Charles Guidotti
• 金额: $ 0.99万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9902857&HistoricalAwards=false
• 关键词: Collaborative; Research; Chemical; Equilibria; Involving

9902857GuidottiThe 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.

9902857Guidotti 这项研究的主要目标是评估缅因州西部的变泥质岩石和新罕布什尔州黑山的相关岩石中涉及二价铁和三价铁以及氢的化学平衡。 我们将研究来自三种不同变质等级的石墨、磁铁矿和赤铁矿岩石的样品：石榴石、低硅线石和十字石带。 这将允许确定： (1) Fe3+ 和 Fe2+ 在所有含 Fe 相和 Hamong 水相中的原位分配系数； (2) Fe3+/Fetotal 的温度和 fO2 依赖性以及 Fe3+ 取代对其他阳离子取代的影响及其对地温测量的影响； (3) 电荷平衡 H 和 Fe3+ 变化的阳离子取代。 我们还将表征并寻求了解单个矿物颗粒内的 Fe3+/Fetotal 分区，以及同一岩石中相同矿物颗粒之间 Fe3+/Fetotal 的变化；最终，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 1" 圆形岩相薄片上进行，使用小于 10 x 15 微米的光束尺寸，以及相对快速、无损的技术，例如用于 Fe3+/Fetotal 的同步加速器 microXANES 光谱 (SmX)、用于 H 的离子微探针 (SIMS) 以及用于其他主要元素的电子微探针 (EPMA)。有了我们手头的分析结果，我们可以 开始解决组合和晶体化学对变钙岩矿物中 Fe2+ 和 Fe3+ 结合的竞争影响。 我们还希望有效、快速地证明 SmX 作为岩石学工具的潜在重要性。