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条件下结晶，并且晶体生长坚定地发生在界面限制（而不是扩散限制）状态。然而，越来越多的结构和成分证据表明，早期岩浆结晶的特征是树枝状晶体的快速生长和形成。在这种情况下，掺入元素的扩散速率可以显著影响晶体生长。本提案概述了利用动态结晶实验和前沿成分和微织构分析技术，研究橄榄石和斜辉石两种基性晶相枝晶生长的力学和岩石学结果的计划。知识价值。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下橄榄石结晶，利用一种新的实验几何结构来增强缺陷的形成。本模块的活动将测试关于弯曲橄榄石-熔体界面起源的假设，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），以及熔体包裹体夹闭过程。预期的结果对地球化学研究具有重要意义。水晶地层学吗?以及海洋岛屿岩浆管道系统的地球物理模型。模块2中的微分析研究以斜辉石树突为目标，研究一种以前在液体中自由生长的晶体中未被识别的渐进式晶格旋转，并且无法用现有的晶体生长理论解释。电子背散射衍射（EBSD）映射将用于表征先前合成的实验样品以及自然产生的斜辉石枝晶和多面体晶体中晶格取向偏差的发生。选择的材料将在TEM箔中进一步使用衍射对比成像、高分辨率相衬成像和能量色散x射线光谱来确定适应晶格旋转的缺陷微观结构。更广泛的影响。我们将继续为夏威夷K-12教师提供专业发展计划，该计划是在之前和当前的奖励期间开发的。这个名为“火山岩石学教师研究经验”（RET/V-P）的项目强调地球科学基础知识和实地地质背景。我们将开发和传播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。我们将与综合地球数据应用（IEDA）主任Lehnert博士合作，开发适合将新的纹理和分析数据纳入地球化学资源库目录的模式。任务包括整合(a)从非平衡（即以动力学为重点）实验中收集的分析数据，(b)元数据，如与图像相关的表格分析数据，以及(c)微晶体取向数据，例如在EBSD分析和x射线元素映射期间生成的数据。

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.