Multicomponent diffusion in silicate melts using eigen-component approach

使用特征分量方法在硅酸盐熔体中进行多组分扩散

• 批准号: 2314724
• 负责人: Youxue Zhang
• 金额: $ 47.5万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2314724&HistoricalAwards=false
• 关键词: Multicomponent; diffusion; silicate; melts; using; Multicomponent; diffusion; silicate; melts; using

This project will investigate diffusion of all major oxides (defined to be more than one weight percent) in dry natural silicate melts using a new approach. In the past, researchers could only successfully and quantitatively study the diffusion of oxides in natural silicate melts with monotonic, or flat, concentration profiles. But what about oxides with non-monotonic profiles? The goal of this project is to develop an easier way to quantify diffusion of all major oxides in dry silicate melts. One application of the new method will be the modeling of the mixing of two magmas. Preliminary results show that such mixing may result in unexpected high concentrations of some metals. Such high concentrations may lead to ore formation. Hence, one of the practical applications is to explain previously unexplained ore formation, and to predict possible locations of ore deposits. Other applications of the new method include more accurate quantification of crystal growth and dissolution rates. This research will also solve a major theoretical problem in high-temperature geochemical kinetics. This project will investigate multicomponent diffusion in dry natural silicate melts using eigen-component approach. Multicomponent diffusion in silicate melts is fundamental to mass transport in igneous processes and is also one of the most difficult experimental and theoretical problems facing geochemical kineticists. Multicomponent diffusion is often encountered in natural silicate melts but not treated due to the level of difficulties in terms of both theory and especially experiments. This team has extracted a diffusion matrix in basaltic melts at three different temperatures, and roughly verified that the diffusion eigenvector matrix in basaltic melts is roughly independent of temperature. They now hypothesize that the diffusion eigenvector matrix is also roughly independent of melt composition in dry melts. They are now further improving the eigenvector matrix and hope to verify that the eigenvector matrix is invariant with composition. In the eigen-component approach, plots of “concentrations” of eigen-components (rather than oxide wt% or mole fractions) versus distance will be made. If their hypothesis is correct, then using the eigenvector matrix, all eigen-component plots would be monotonic, and diffusion eigenvalues (i.e., diffusivity for the eigen-components) will be obtained from fitting the eigen-component profiles. If some eigen-component plots in some experiments show nonmonotonic profiles, within the framework of our hypothesis, it would mean inaccuracy of the eigenvector matrix, and hence the need to improve the eigenvector matrix. To complete the investigation of multicomponent diffusion in a melt, a couple of well-designed experiments at each temperature and pressure will be enough to determine all eigenvalues, and hence the full diffusion matrix. This team's hypothesis and new approach will contribute to the fundamental understanding of diffusion in natural silicate melts. The success of the proposed work will remove one difficult problem from the list of geochemical kineticists and allow future geochemists to realistically predict diffusion-controlled processes, such as magma mixing, mineral growth and dissolution, and post-entrapment interaction between a melt inclusion and its host mineral. They will build and publish an online resource to compute multicomponent diffusion profiles. This would enable interested students and scientists to use multicomponent diffusion in their research of geological problems. This planned online calculator will help facilitate the use of their results by the petrological and geochemical community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目将使用一种新方法研究干燥天然硅树脂中所有主要氧化物的差异（定义为超过一个重量百分比）。过去，研究人员只能成功和定量研究氧化物在具有单调或平坦浓度曲线的天然有机硅中的扩散。但是，具有非单调轮廓的氧化物呢？该项目的目的是开发一种更简单的方法来量化干硅酸盐融化中所有主要氧化物的差异。新方法的一种应用是两个岩浆的混合建模。初步结果表明，这种混合可能会导致意外的高浓度某些金属。这样的高浓度可能导致矿石形成。因此，实际应用之一是解释先前未知的矿石形成，并预测矿床的可能位置。新方法的其他应用包括更准确地量化晶体生长和溶解速率。这项研究还将解决高温地球化学动力学中的主要理论问题。该项目将使用特征组件方法研究干燥天然有机硅熔体中的多组分扩散。在火成点过程中，硅熔体中的多组分扩散是大规模运输的基础，也是地球化学动力学家面临的最困难的实验和理论问题之一。自然有机硅熔体通常会遇到多组分扩散，但由于理论（尤其是实验）的难度水平而没有治疗。该团队在三种不同的温度下提取了玄武岩熔体中的扩散矩阵，并大致证实了玄武岩熔体中的扩散特征向量基质大致与温度大致独立。他们现在假设他们的扩散特征向量基质大致独立于干熔体中的熔体组成。现在，他们正在进一步改善特征向量矩阵，并希望验证特征向量矩阵与成分不变。在本征组件方法中，将制定与距离相对于距离的本征组成部分（而不是氧化物WT％或摩尔分数）的“浓度”图。如果它们的假设是正确的，则使用特征向量基质，所有本本特征组件图都是单调的，并且将通过拟合本征组件的轮廓获得差异特征值（即，特征值的扩散率）。如果某些实验中的某些本征组件图在我们的假设的框架内显示了非单调曲线，则意味着特征向量矩阵的不准确性，因此需要改善特征向量矩阵。为了完成对熔体中多组分扩散的研究，在每个温度和压力下进行了几个精心设计的实验，足以确定所有特征值，从而使完整的扩散矩阵。该团队的假设和新方法将有助于对天然有机硅融化的扩散的基本理解。拟议的工作的成功将从地球化学动力学家列表中消除一个困难的问题，并允许未来的地球化学主义者实际预测扩散控制的过程，例如岩浆混合，矿物质的生长和溶解以及熔体融合及其宿主矿物质之间的交流后相互作用。他们将构建和发布在线资源以计算多组件扩散配置文件。这将使感兴趣的学生和科学家在对地质问题的研究中使用多组分差异。该计划的在线计算器将有助于支持岩石学和地球化学社区的结果。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准通过评估来获得的支持。