Collaborative Research: The Effects of CO2-H2O Fluids on the Deformation of Quartzite and Marble in the EJB Aureole, California

实验室研究表明，水对岩石的流变性有很大的影响，特别是对岩石的强度、应变率和恢复机制有很大影响。在这个项目中，来自中央密歇根大学和密苏里大学哥伦比亚分校的一个研究小组将使用自然实验室的方法来研究可变的流体成分对自然变形的石英岩和大理石的直接影响。该团队将研究可变的水-二氧化碳流体对加州怀特山尤里卡谷-约书亚平坦-比尔克里克复合岩体周围光环中这些岩石变形和重结晶的影响，在那里，一段强烈的高温变形与岩体侵位有关。该项目的目标是确定受流体影响的围岩的流变性如何影响中地壳深成岩体的侵位和空间形成过程，并从更广泛的角度评估流体如何影响大陆岩石圈的变形和强度。尤里卡山谷-Joshua Flat-Beer Creek岩体光环的受限环境提供了一个机会，补充了实验室实验对岩石变形和重结晶的现有理解，这些实验必须在比自然中看到的高得多的应变率下进行。这项研究将结合野外、显微构造、岩石学和地球化学工作，确定不同水量和流体成分对石英岩及其相关大理岩变形的影响。田野工作将为研究提供背景，并识别高应变和低应变区域。将使用电子背散射衍射、普适阶段和颗粒形状分析来确定石英岩和大理石的变形和恢复机制。岩石中的矿物学和稳定同位素比率将指示流经不同岩性的流体的组成，而对流体包裹体的分析将直接显示流体的组成。地球岩石圈的变形速度控制其地形特征。实验室实验表明，在大陆深部地壳所经历的高温和压力下，水尤其能促进岩石的变形和重结晶。因此，虽然人们普遍认为，在下大陆地壳中，岩石是韧性的，但它们变得韧性的温度受到岩石中可能存在的流体成分的影响。在上地壳，岩浆岩周围岩石的变形也会受到流体成分的影响。然而，将实验室实验应用于大陆地壳的变形有时是困难的，因为实验室和地壳发生变形的时间尺度非常不同，而且实验室实验不能再现自然界中看到的复杂的变形环境。该项目将在加利福尼亚州怀特山的一个岩体的变质光环的自然实验室中评估地壳岩性的变形和重结晶。变质光环中的岩石经历了不同程度的变形和重结晶，似乎受到了水和二氧化碳比例不同的流体的影响。将使用现场工作和几项复杂的技术来确定变质光环中岩石的变形和重结晶机制，以及流经岩石的流体的组成。这项工作将更好地了解影响岩石变形速度的因素，这些速度受构造力和岩浆通过地壳上升的控制。

It has been shown by laboratory studies that water has a drastic effect on the rheology of rocks, specifically influencing rock strength, strain rates, and recovery mechanisms. In this project, the a research team from Central Michigan University and the University of Missouri, Columbia, will use a natural laboratory approach to investigate the direct effects of variable fluid composition on naturally deformed quartzites and marbles. The team will examine the influence of variable water-carbon dioxide fluids on deformation and recrystallization of these rocks in the aureole surrounding the Eureka Valley-Joshua Flat-Beer Creek composite pluton in the White Mountains of California where a period of intense high temperature deformation was associated with pluton emplacement. The goal of the project is to determine how the rheology of the wall rocks, influenced by fluids, affected the emplacement and space-making processes of mid-crustal plutons, and from a broader perspective, to assess how fluids affect the deformation and the strength of the continental lithosphere. The constrained environment of the Eureka Valley-Joshua Flat-Beer Creek pluton aureole provides an opportunity to compliment the current understanding of rock deformation and recrystallization from laboratory experiments that must be done at much higher strain rates than are seen in nature. The study will integrate field, microstructural, petrologic and geochemical work to determine the influence of variable amount of water and fluid composition on deformation of quartzites and related marbles. The fieldwork will provide the context for the study and recognize areas of high and low strain. Electron backscatter diffraction, universal stage, and grain shape analyses will be used to determine the deformation and recovery mechanisms of the quartzites and marbles. Mineralogy and stable isotope ratios in the rocks will indicate the compositions of fluids that flowed through the individual lithologies, while analysis of fluid inclusions will directly show fluid compositions.The rate of deformation of the Earth's lithosphere controls its topographic features. Laboratory experiments have shown that water in particular promotes the deformation and recrystallization of rocks at high temperatures and pressures experienced by the deep continental crust. Thus, while it is generally recognized that in the lower continental crust rocks are ductile, the temperature at which they become ductile is influenced by the composition of fluids that may exist in the rocks. In the upper crust, the deformation of rocks around magma plutons will also be influenced by fluid compositions. The application of laboratory experiments to deformation of the continental crust is sometimes difficult, however, because of the vastly different time scales at which deformation occurs in the laboratory and the crust and because laboratory experiments do not reproduce the complex deformation environments seen in nature. This project will evaluate the deformation and recrystallization of crustal lithologies in the natural laboratory of the metamorphic aureole of a pluton in the White Mountains of California. The rocks in the metamorphic aureole have experienced various degrees of deformation and recrystallization that appear to have been influenced by fluids with variable proportions of water and carbon dioxide. Field work and several sophisticated techniques will be used to determine the deformation and recrystallization mechanisms of rocks in the metamorphic aureole and the compositions of fluids that flowed through the rocks. This work will provide a better understanding of factors that influence rock deformation at rates that are controlled by tectonic forces and magma ascent through the crust.