Experimental and Microanalytical Study of Dendritic Crystal Growth in CMAS and Basaltic Magma

岩石成因和地球化学模型通常假设岩浆在接近平衡的条件下结晶，晶体生长坚定地发生在界面受限(而不是扩散受限)区域。然而，越来越多的结构和成分证据表明，以树枝状晶体的快速生长和形成为特征的早期岩浆结晶？在这种情况下，掺入元素的扩散速度会显著影响晶体的生长。这项建议概述了一项计划，利用动态结晶实验和前沿成分和显微结构分析技术，研究橄榄石和单斜辉石两种镁铁质晶相中树枝状晶体生长的力学和岩石学后果。智力上的功绩。模块1的实验和分析研究，目标是在动态温度条件下的热梯度中的橄榄石结晶，利用一种新的实验几何结构来促进缺陷的形成。本模块中的活动将测试关于弯曲的橄榄石-熔体界面的起源、在没有各向异性应力的情况下亚晶界的发展(低角度晶格取向错误)以及熔体包裹体捕获过程的假设。预期结果对地质学、晶体地层学、地质学等都有重要意义。以及海洋岛屿岩浆管道系统的地球物理模型。模块2中的微观分析研究以单斜辉石树枝晶为目标，研究一种以前在自由从液体中生长的晶体中未被识别的、无法用现有晶体生长理论解释的渐进晶格旋转方式。电子背散射衍射(EBSD)图谱将被用来表征先前合成的实验样品以及自然生成的单斜辉石树枝晶和多面体晶体中晶格取向错误的发生率。选定的材料将在透射电子显微镜薄膜中使用衍射对比度成像、高分辨率相衬成像和能量色散x射线光谱来进一步询问，以确定适应晶格旋转的缺陷微结构。更广泛的影响。我们将继续为夏威夷K-12教师在之前和当前的获奖期间培养的教师提供专业发展计划。这项名为“火山岩石学教师研究经验”(RET/V-P)的课程强调地球科学的基础知识和实地考察的地质学知识。我们将开发和传播用于6-8年级教学的教育材料，包括评估前和评估后的工具、课堂活动、对瓦胡岛几个地点的实地考察，以及更深入调查的资源。我们将与地球综合数据应用(IEDA)主任Lehnert博士合作，开发适合于将新的结构和分析数据纳入地球化学资源库目录的模式。任务包括纳入(A)从非平衡(即，侧重于动力学的)实验收集的分析数据，(B)与图像关联的表格分析数据等元数据，以及(C)微晶取向数据，例如在EBSD分析和X射线元素测绘期间生成的数据。

Petrogenetic and geochemical models generally assume that magmas crystallize under near equilibrium conditions, and that crystal growth occurs firmly in the interface-limited (as opposed to diffusion-limited) regime. However, mounting textural and compositional evidence points toward incipient magma crystallization characterized by rapid growth and formation of dendritic crystals ? in which case diffusion rates of the incorporated elements can significantly influence crystal growth. This proposal outlines a plan for studying the mechanics and petrologic consequences of dendritic crystal growth in two mafic crystalline phases, olivine and clinopyroxene, utilizing dynamic crystallization experiments and frontier compositional and microtextural analysis techniques. Intellectual Merit. The experimental and analytical study of Module 1, targets olivine crystallization in a thermal gradient under dynamic temperature conditions, utilizing a novel experimental geometry to enhance formation of defects. Activities in this module will test hypotheses regarding the origin of curved olivine-melt interfaces, development of subgrain boundaries (low angle lattice misorientations) in the absence of anisotropic stress, and the process of melt inclusion entrapment. The anticipated results have important implications for geochemical ?crystal stratigraphy? as well as geophysical models of ocean island magmatic plumbing systems. The microanalytical study in Module 2, targets clinopyroxene dendrites to investigate a style of progressive lattice rotation that is previously unrecognized in crystals growing freely from a liquid, and unexplained by existing crystal growth theory. Electron backscatter diffraction (EBSD) mapping will be used to characterize the incidence of lattice misorientations in previously-synthesized experimental samples as well as naturally-occurring clinopyroxene dendrites and polyhedral crystals. Selected materials will be further interrogated in TEM foils using diffraction contrast imaging, high resolution phase contrast imaging, and enegy-dispersive x-ray spectroscopy to determine the defect microstructure that accommodates the lattice rotation. Broader Impacts. We will continue offering a professional development program for Hawaii K-12 teachers developed during prior and current award periods. The program, Research Experience for Teachers in Volcano-Petrology (RET/V-P) emphasizes geoscience fundamentals and exposure to geology in a field setting. We will develop and disseminate educational materials intended for 6-8th grade instruction, composed of pre- and post-assessment instruments, classroom activities, field trips to several Oahu sites, and resources for deeper investigation. We will work with Dr. Lehnert, Director of the Integrated Earth Data Applications (IEDA), to develop schema appropriate for incorporation of novel textural and analytical data in the Geochemical Resource Library catalog. Tasks include incorporating (a) analytical data collected from non-equilibrated (i.e., kinetics-focused) experiments, (b) metadata such as tabulated analytical data that is contextualized with imagery, and (c) microcrystallographic orientation data, e.g., as generated during EBSD analysis and Xray element mapping.