Si and Fe Isotope Geochemistry at High Pressure and Temperature

高压高温下的硅和铁同位素地球化学

• 批准号: 0948131
• 负责人: Anat Shahar
• 金额: $ 21.1万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948131&HistoricalAwards=false
• 关键词: Si; Fe; Isotope; Geochemistry; Pressure

Intellectual Merit. One of the main goals in earth science research is to determine the chemical composition of the Earth and its primary reservoirs. Isotopic and chemical mass balance calculations have been used extensively to better constrain fundamental issues such as the structure of mantle convection and determination of the light element contents in the core. Much work has focused on chemical partitioning experiments over a large range of pressures and temperatures. Although it has been assumed that pressure was not an important variable for isotopic fractionation among coexisting phases, new calculations of vibrational frequencies suggest that this assumption may not be true, and high P conditions may significantly influence stable isotopic variations within planetary bodies. It is well known that pressure can produce dramatic changes in material properties and mineral equilibria, but its effect on isotopic fractionation has not been well characterized. With the advent of new high-precision isotope ratio measurement techniques and development of high-pressure apparatus, there is great potential for interdisciplinary research in this field. It is proposed to investigate the effect of pressure on isotope fractionation, and specifically under conditions of core formation, as a function of mineralogy throughout the earth's mantle. Stable isotope geochemistry and experimental petrology/mineral physics methods will be applied to determine fractionation mechanisms. Isotopically spiked experiments will be conducted at high P-T conditions and run products analyzed to determine isotopic fractionation between coexisting phases. The results will be applied to understand the composition of the Earth's core and its interaction with the overlying mantle. Specific research questions include: [1] how does pressure affect isotopic fractionation of the non-traditional stable isotopes (Si, Fe)? [2] do fractionation factors change throughout the Earth's mantle as a function of pressure and hence mineralogy? [3] do large-scale processes such as core formation leave a stable isotopic signature that can be measured today?Broad Impacts. This project is defining a new field in the geosciences, necessitating the need for training in both mineral physics/experimental petrology and isotope geochemistry. A new female Staff member is named as a PI on this proposal and is responsible for much of the work therein. Results from the proposed study will be disseminated primarily through scientific journals and by participation at scientific conferences from both fields.

智力优势。地球科学研究的主要目标之一是确定地球及其主要水库的化学成分。同位素和化学质量平衡计算已被广泛用于更好地约束基本问题，如地幔对流的结构和确定轻元素的核心内容。许多工作集中在大范围的压力和温度下的化学分配实验。 虽然人们一直认为压力不是共存相之间同位素分馏的重要变量，但对振动频率的新计算表明，这种假设可能不正确，高P条件可能会显着影响行星体内稳定的同位素变化。众所周知，压力能引起物质性质和矿物平衡的剧烈变化，但它对同位素分馏的影响还没有得到很好的表征。随着高精度同位素比值测量技术的出现和高压仪器的发展，这一领域的跨学科研究具有巨大的潜力。建议研究压力对同位素分馏的影响，特别是在地核形成的条件下，作为整个地幔矿物学的函数。将应用稳定同位素地球化学和实验岩石学/矿物物理学方法来确定分馏机制。将在高P-T条件下进行同位素加标实验，并分析运行产物，以确定共存相之间的同位素分馏。研究结果将用于了解地核的组成及其与上覆地幔的相互作用。具体的研究问题包括：[1]压力如何影响非传统稳定同位素（Si，Fe）的同位素分馏？[2]分馏因素是否随着压力和矿物学的变化而在整个地幔中发生变化？[3]像地核形成这样的大规模过程是否留下了今天可以测量的稳定同位素特征？广泛的影响。该项目正在确定地球科学的一个新领域，因此需要进行矿物物理学/实验岩石学和同位素地球化学方面的培训。一名新的女性工作人员被任命为该提案的主要研究者，负责其中的大部分工作。拟议研究的结果将主要通过科学期刊和参加这两个领域的科学会议来传播。