Collaborative Research: Diffusion of High Field Strength Elements (HFSE) and Rare Earth Elements (REE) in Pyroxenes and Pyroxene-bearing Rocks

合作研究：高场强元素 (HFSE) 和稀土元素 (REE) 在辉石和含辉石岩石中的扩散

• 批准号: 0738830
• 负责人: Yan Liang
• 金额: $ 15.01万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-01 至 2012-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0738830&HistoricalAwards=false
• 关键词: Collaborative; Research; Diffusion; Field; Strength

Intellectual Merit. The abundance and distribution of high field strength elements (HFSE) and rare earth elements (REE) in mafic and ultramafic rocks provide important clues to understanding the origin and evolution of igneous rocks. While the distribution of such trace elements between coexisting minerals and melt in many magmatic processes can be understood in terms of equilibrium fractionation, there are occasions where substantial chemical disequilibria between coexisting phases might provide unique and important insights into the time scales of geological processes. To better understand the various processes that give rise to disequilibrium distributions of HFSE and REE in the mantle and mantle derived rocks, partition coefficients and diffusion coefficients of these trace elements in major rocking-forming minerals are needed. Mineral-melt and mineral-mineral HFSE and REE partition coefficients for important mafic minerals such as clinopyroxene (cpx) and orthopyroxene (opx) are available for a range of temperatures, pressures, and melt and crystal compositions. There exists no HFSE diffusion data for any pyroxene compositions, while REE diffusion data in pyroxene is only available for the near endmember diopside and enstatite. It is not known how strongly REE and HFSE diffusion rates in pyroxenes depend on pyroxene compositions. In order to establish a database for studying kinetic fractionations of HFSE and REE in pyroxene-bearing rocks during magmatic and subsolidus processes, a three-year collaborative research program is proposed that consists of two major components: (1) laboratory studies of HFSE and REE diffusion in pyroxenes; and (2) ion probe and numerical studies of HFSE and REE zoning in coexisting cpx and opx in peridotites from the Trinity ophiolite. A range of pyroxene compositions common in the origin and differentiation of mafic and ultramafic rocks will be explored. Diffusion profiles from most diffusion experiments will be measured with Rutherford Backscattering Spectrometry (RBS). Trace element concentration profiles in coexisting cpx and opx will be measured by ion probe. Together with published partition and diffusion data, diffusion coefficients of HFSE and REE in pyroxenes obtained from this study will be used to develop generalized geospeedometry models that can be used to understand the processes and time scales of melt-rock reaction, via dissolution and reprecipitation, and subsolidus reequilibration experienced by the Trinity peridotites.Broader Impacts. Diffusion is a fundamental mass transfer process in solid-Earth systems and hence a very general topic. Diffusion coefficients obtained from this work will be widely applicable to pyroxenes and pyroxene bearing rocks from the Earth, Moon, Mars, and various meteorites. The dissolution-reprecipitation model to be developed will be useful to a range of practical applications beyond Earth Sciences. Results from this study will also provide valuable information for a diverse group of petrologists, geochemists, geochronologists, and cosmochemists, promoting cross-discipline integration in Earth Sciences. Results will be disseminated to a broader audience through public lectures and undergraduate and graduate courses. Finally, the proposed project will provide hands-on experience for undergraduates, research opportunities for senior thesis work, and experimental, computational, and educational experience for graduate students.

智力优点。高田格强度元素（HFSE）和稀土元素（REE）的丰度和分布在镁铁质和超镁铁质岩石中提供了重要的线索，以理解火成岩的起源和演变。虽然可以从平衡分馏中理解共存矿物质和熔体之间的这种痕量元素的分布，但在某些情况下，共存阶段之间的实质性化学不平衡可能会为地质过程的时间尺度提供独特而重要的见解。为了更好地了解，需要在地幔和地幔衍生的岩石中引起HFSE和REE的不平衡分布的各种过程，需要在主要摇摆形成矿物质中这些痕量元素的分区系数和扩散系数。重要的镁铁质矿物质（例如斜二烯（CPX）（CPX）和Orthopyroxene（OPX）的矿物质熔点和矿物矿物HFSE和REE分区系数可用于一系列温度，压力以及熔体和晶体组成。对于任何辉石组合物，都没有HFSE扩散数据，而辉石中的REE扩散数据仅适用于近端的Diopside和Enstatite。偶像偶然氧化烯的REE和HFSE扩散速率如何依赖于辉石组成。为了建立一个数据库，用于研究在岩浆和子宫孢子过程中HFSE和REE的动力学分馏，并提出了一项为期三年的协作研究计划，该计划由两个主要组成部分组成：（1）HFSE和REE在曲羟烯的实验室研究；（1） （2）来自三位一体蛇绿岩的橄榄岩中共存的CPX和OPX中HFSE和REE分区的离子探针和数值研究。将探索一系列在镁铁质和超镁铁质岩石的起源和分化中常见的辉石组成。大多数扩散实验的扩散曲线将通过卢瑟福反向散射光谱法（RBS）测量。共存CPX和OPX中的痕量元素浓度谱将通过离子探针测量。 Together with published partition and diffusion data, diffusion coefficients of HFSE and REE in pyroxenes obtained from this study will be used to develop generalized geospeedometry models that can be used to understand the processes and time scales of melt-rock reaction, via dissolution and reprecipitation, and subsolidus reequilibration experienced by the Trinity peridotites.Broader Impacts.扩散是固态系统中的基本传质过程，因此是一个非常普遍的主题。从这项工作中获得的扩散系数将广泛适用于辉石烯和辉石，从地球，月亮，火星和各种陨石中岩石岩石。要开发的溶解 - 重新注定模型将对地球科学以外的一系列实用应用有用。这项研究的结果还将为多样化的岩石学家，地球化学家，地球人学家和宇宙化学家提供宝贵的信息，从而促进地球科学中的跨学科整合。结果将通过公开讲座以及本科和研究生课程传播给更广泛的受众。最后，拟议的项目将为本科生提供实践经验，高级论文工作的研究机会以及研究生的实验，计算和教育经验。