Collaborative Research: Volatile Contents of Komatiites

合作研究：科马提岩的挥发性成分

• 批准号: 0635866
• 负责人: Erik Hauri
• 金额: --
• 依托单位: Carnegie Institution of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635866&HistoricalAwards=false
• 关键词: Collaborative; Research; Volatile; Contents; Komatiites

Intellectual merit. Komatiites provide key, but controversial, constraints on the thermal and compositional evolution of the Earth. Of primary importance are the water contents of komatiite magmas - at low water contents formation of komatiites require mantle potential temperatures 500 C above modern values, whereas wet melting requires more modest increases. Present estimates of komatiite water contents are variable and hotly debated. Further, relatively little is known about the abundances of other volatile elements (S, F, Cl) in komatiite magmas and their mantle sources, although these have the potential to provide primary constraints for models of geochemical cycling and degassing. We propose a collaborative study of volatile contents in komatiites. This will primarily be through measurements of melt inclusions trapped within silicate and oxide phases in well-preserved komatiite samples from the Belingwe Greenstone Belt in Zimbabwe, but will also involve examination and preliminary measurements of komatiites from a selection of other low and medium metamorphic grade terranes. The study will use a combination of petrographic observations and microanalytical techniques: Secondary Ion Mass Spectrometry (SIMS); Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Electron Microprobe Analysis (EMPA). Previous data reported from melt inclusions in Belingwe samples are not definitive in terms of estimates of komatiite water contents and we propose a careful analytical scheme to rectify this. We will also measure abundances of other volatile species (CO2, F, S, Cl) as well as major and trace elements, S and H speciation and H isotope composition. This additional data will help define the effects of degassing, hydrogen diffusion, crustal assimilation, alteration and other processes that have the potential to alter primary water contents, but will also provide new insights into the compositions of komatiite magmas and their mantle sources. Preliminary data demonstrate that melt inclusions in samples we have in hand contain significant and measurable abundances of H2O, CO2, S and Cl. Overall our study will provide some of the first direct constraints on the volatile contents of komatiite magmas and Archean mantle and komatiites source regions. Broader impacts. This work will address several broader impacts. The work will support two PI's, foster collaboration between two research institutions, Oregon State University and the Carnegie Institute of Washington, and contribute to development and maintenance of geochemical analysis facilities in both places. The work will also provide fundamental information about the chemical and thermal evolution of the earth and is part of a long-term project to investigate the volatile structure and evolution of the mantle. A particularly important impact of this work will be to foster undergraduate research and to engage talented undergraduates in state-of-the-art research and use of research facilities at OSU and CIW. Two undergraduates from OSU will perform senior thesis research related to the project and this will involve visits to both CIW and to field outcrops of komatiite and associated rocks in the Abitibi Greenstone Belt in Canada. Both PI's are active in fostering undergraduate research. PI-Kent is coordinating undergraduate research for the OSU petrology group and will co-teach a course in undergraduate research for juniors and seniors in Fall 2006. Undergraduate research at Oregon State is currently being reinvigorated through these activities and via recent employment of an undergraduate research coordinator.

智力上的优点。科马提岩对地球的热和成分演化提供了关键但有争议的限制。最重要的是科马提岩浆的含水量——在低含水量的情况下，科马提岩的形成需要地幔潜在温度比现代值高500℃，而湿熔融则需要更适度的增加。目前对科马提岩含水量的估计是可变的并且存在激烈争论。此外，人们对科马提岩浆及其地幔源中其他挥发性元素（S、F、Cl）的丰度知之甚少，尽管这些元素有可能为地球化学循环和脱气模型提供主要约束。我们提议对科马提岩中的挥发性成分进行合作研究。这主要是通过对来自津巴布韦贝林圭绿岩带的保存完好的科马提岩样品中硅酸盐和氧化物相中捕获的熔融包裹体进行测量，但也将涉及对来自其他低和中变质等级地体的科马提岩进行检查和初步测量。该研究将结合岩相观察和微量分析技术：二次离子质谱（SIMS）；激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) 和电子微探针分析 (EMPA)。以前从贝林圭样品中的熔体包裹体报告的数据在科马提石含水量的估计方面并不明确，我们提出了一个仔细的分析方案来纠正这一问题。我们还将测量其他挥发性物质（CO2、F、S、Cl）的丰度以及主量元素和微量元素、S 和 H 形态以及 H 同位素组成。这些额外的数据将有助于确定脱气、氢扩散、地壳同化、蚀变和其他可能改变原生水含量的过程的影响，同时也将为科马提岩岩浆的成分及其地幔来源提供新的见解。初步数据表明，我们手头样品中的熔体包裹体含有大量可测量的 H2O、CO2、S 和 Cl。总的来说，我们的研究将为科马提岩浆和太古代地幔和科马提岩源区的挥发性含量提供一些初步的直接限制。更广泛的影响。这项工作将解决几个更广泛的影响。这项工作将支持两位 PI，促进俄勒冈州立大学和华盛顿卡内基研究所这两个研究机构之间的合作，并为两地地球化学分析设施的开发和维护做出贡献。这项工作还将提供有关地球化学和热演化的基本信息，并且是研究地幔挥发性结构和演化的长期项目的一部分。这项工作的一个特别重要的影响将是促进本科生研究，让有才华的本科生参与最先进的研究以及使用俄勒冈州立大学和 CIW 的研究设施。俄勒冈州立大学的两名本科生将进行与该项目相关的高级论文研究，其中包括参观 CIW 以及加拿大阿比蒂比绿岩带的科马提岩露头和相关岩石。两位 PI 都积极致力于促进本科生研究。 PI-Kent 正在协调俄勒冈州立大学岩石学小组的本科生研究，并将于 2006 年秋季共同为大三和大四学生教授一门本科生研究课程。俄勒冈州立大学的本科生研究目前正在通过这些活动以及最近聘用的一名本科生研究人员而得到重振。协调员。