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.

智力优点。 Komatiites对地球的热和组成演化提供了关键但有争议的约束。最重要的是高岩岩浆的水含量 - 在低水含量的形成下，高地幔的潜在温度高于现代价值，而湿熔化需要更适度的增加。当前对高元石含量的估计值是可变的，并且有争议。此外，对于Komatiite岩浆及其地幔源中其他挥发性元件（S，F，CL）的丰富性，相对较少，尽管这些元素有潜力为地球化学循环和脱气模型提供主要约束。我们提出了一项关于挥发物含量的合作研究。这主要是通过对津巴布韦Belingwe Greenstone保存完好的Komatiite样品中硅酸盐和氧化物阶段中的熔体夹杂物的测量，但还将涉及从其他低和中等变质级的选择中的Komatiite的检查和初步测量。该研究将结合岩石学观测和微分析技术：次级离子质谱法（SIMS）；激光消融电感耦合等离子体质谱法（LA-ICP-MS）和电子微探针分析（EMPA）。从贝林威样品中的熔体夹杂物报告的先前数据在komatiite水含量的估计方面并不确定，我们提出了一种仔细的分析方案来纠正这一点。我们还将测量其他挥发性物种（CO2，F，S，CL）以及主要和痕量元素，S和H的物种形成以及H同位素组成。这些附加数据将有助于定义脱气，氢扩散，地壳同化，改变和其他有可能改变原始水含量的过程的影响，但还将为Komatiite Magmas及其地幔来源提供新的见解。初步数据表明，在样品中，我们手头上的融合物包含H2O，CO2，S和CL的大量且可测量的丰度。总体而言，我们的研究将对Komatiite Magmas和Archean Mantle和Komatiites源区域的挥发性含量提供一些第一个直接约束。更广泛的影响。这项工作将解决一些更广泛的影响。这项工作将支持两家研究机构（俄勒冈州立大学和华盛顿卡内基研究所）之间的两个PI的寄养合作，并为这两个地方的地球化学分析设施的开发和维护做出了贡献。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变的长期项目的一部分。这项工作的一个特别重要的影响是培养本科研究，并吸引有才华的本科生在OSU和CIW的最先进的研究和使用研究设施中。 OSU的两名大学生将进行与该项目有关的高级论文研究，这将涉及加拿大Abitibi Greenstone Belt中的Komatiite和相关岩石的访问。两种PI都活跃于培养本科研究。 Pi-Kent正在为OSU Petrology小组协调本科研究，并将在2006年秋季共同为大三和老年人的本科研究课程。目前，俄勒冈州立大学的本科研究正在通过这些活动以及最近的本科生研究协调员的雇用。