Ca-Mg Isotopic Probe of Transport Processes in High Temperature Geochemical Systems

这个项目的目的是利用新的分析和实验方法来确定岩浆和地热水中化学过程的速率。这类信息对于了解岩浆如何在火山下移动并最终喷发，以及估计地热系统的流体流速和寿命都很重要。研究的第二部分是利用对常见化学元素同位素的新测量方法，了解硅酸盐液体和水热溶液的材料特性。新方法将用于确定从岩浆和热液溶液中结晶的矿物是否在化学平衡状态下结晶。如果不是，根据初步数据很可能是这样的，那么目标是通过测量Ca， Mg和K的同位素丰度来确定这些矿物质的生长速度，然后提供有关自然过程速度的其他信息。拟议的测量矿物生长速率的方法是基于元素Ca， Mg和K的同位素测量，也将包括微量元素的测量。非平衡同位素效应将提供微量元素分馏过程的信息，这对解释矿物化学具有重要意义。对液体材料特性的研究利用了元素和分子在液体中扩散时发生的依赖质量的同位素变化。这些微妙的同位素变化现在可以监测到关键元素，包括Ca和Mg，以及其他化学物质，如Ar和CO2。所有这些物种都可以表现出与扩散相关的质量依赖的同位素变化。这些变化取决于液体的粘度、化学成分和化学结构，以及每种物质与液体分子的化学结合方式。因此，扩散引起的同位素变化提供了其他任何方法都无法确定的关于高温液体的独特信息。通过研究在已知条件下以比实验室实验慢得多的速度形成的天然岩石和矿物，实验将得到加强。这项研究的结果可能会对材料科学、火山学和地热能生产产生影响。

This project is aimed at using new analytical and experimental methods to determine the rates of chemical processes in magmas and in geothermal waters. This kind of information is important for understanding how magmas move under volcanoes and eventually erupt, and for estimating the fluid flow rates and lifetimes of geothermal systems. A second part of the research is directed toward understanding the material properties of silicate liquids and hydrothermal solutions, using novel measurements of isotopes of common chemical elements. The new methods will be used to determine whether minerals that crystallize from magma and hydrothermal solutions do so at chemical equilibrium. If not, as is likely according to preliminary data, the objective is to use measurements of isotopic abundances of Ca, Mg, and K to determine how fast such minerals grow, which will then provide other information about the speed of related natural processes.The proposed method for measuring mineral growth rates is based on isotopic measurements of the elements Ca, Mg, and K and will also include trace element measurements. Non-equilibrium isotopic effects will provide information about trace element fractionation processes, which are important for interpreting mineral chemistry. The research on liquid material properties uses mass-dependent isotopic changes that occur as elements and molecules diffuse through liquids. These subtle isotopic changes can now be monitored in key elements including Ca and Mg, as well as other chemical species like Ar and CO2. All of these species can exhibit mass-dependent isotopic changes related to diffusion. The changes depend on the viscosity, chemical composition, and chemical structure of the liquids, and the ways in which the each species is chemically bound to the liquid molecules. Consequently, diffusion-induced isotopic changes provide unique information about high temperature liquids that cannot be determined by any other method. Experiments will be augmented by study of natural rocks and minerals that formed under known conditions and at much slower rates than those of the laboratory experiments. The results of this research may have implications for materials science, volcanology, and geothermal energy production.