EAGER: Collaborative Research: Collaborative Investigations of Isotopic Fractionation by Thermal Diffusion and Thermal Migration

这个早期概念的探索性研究资助（EAGER）代表了一个跨学科的努力，以解决地球化学过程，可能是负责稳定同位素变化的火成岩（NTSI）中的“非传统稳定同位素”的最新观测。Mg和Si同位素的显著分馏很难用矿物和熔体之间的平衡来解释。令人兴奋的新发现，大的同位素分馏发生在熔体内的温度梯度提供了一个可能的解释所观察到的同位素变化。热扩散分馏是如此之大，它可以提供一个独特的工具来辨别岩浆分异热梯度驱动过程的作用的基础。该项目代表了一种协同和新颖的合作，为NTSI分馏现象的研究带来了实验，分析和理论方法。将开展三项补充工作，包括：1）实验室硅酸盐Soret利用天然组分和选定的简单体系进行的（全熔融）实验; 2）热迁移过程中主量和微量元素行为及NTSI分馏分析玄武岩到流纹岩整体成分的（部分熔融）实验和Mg、Si和Fe的BetaT测定;（3）MgO-SiO_2体系中温度梯度下同位素分馏的分子动力学模拟，探讨热扩散对NTSI分馏影响的物理基础。拟议的科学计划汇集了三组研究人员，他们在岩石学/地球化学研究方面具有不同的专业知识，从野外岩石学到实验岩石学再到分子动力学模拟。

This EArly-concept Grant for Exploratory Research (EAGER) represents an interdisciplinary effort to address the geochemical processes that could be responsible for recent observations of stable isotope variations for "non-traditional stable isotopes" in igneous rocks (NTSI). Significant fractionations in the isotopes of Mg and Si are difficult to explain in terms of equilibrium between minerals and their melts during common igneous differentiation processes. The exciting new discovery that large isotopic fractionations occur in melts held within a temperature gradient offers a possible explanation for the observed isotope variations. The fractionation by thermal diffusion is so large that it may provide the basis for a unique tool to discern the role of thermal-gradient-driven processes for magmatic differentiation. This project represents a synergistic and novel collaboration that brings experimental, analytical, and theoretical approaches to the study of this NTSI fractionation phenomenon. Three complementary efforts will be undertaken that include: 1) Laboratory silicate Soret (fully molten) experiments using both natural compositions and selected simple systems; 2) Analysis of major and trace element behavior and NTSI fractionation in thermal migration (partially molten) experiments on basalt to rhyolite bulk compositions and determination of BetaT for Mg, Si and Fe; and 3) Molecular dynamics simulations of isotope fractionation within a temperature gradient in the MgO-SiO2 system to investigate the physical basis for the effects of thermal diffusion on NTSI fractionation. The proposed science plan brings together three groups of researchers with different expertises in petrology/geochemistry research from field petrology to experimental petrology to molecular dynamics simulation.