Trace Element Crystal Growth Speedometry: Implications for Magmatic and Hydrothermal Systems

这项研究的目的是为了更好地理解是什么控制着晶体在简单和复杂的自然系统中生长的速度。例如，晶体生长对预测火山爆发的条件有直接的影响，因为结晶可能会导致气泡的形成或增加岩浆的粘度，这两者都有助于火山爆发所需的超压力的积累。量化晶体的生长速度还可以让我们了解岩浆体在灾难性地喷发之前需要多长时间才能生长，从而给生命和人类社会带来危险的环境。然而，限制晶体生长速率的适当方法仍然难以捉摸。这项工作的目标是开发和校准一种新的晶体生长速度计，该计基于微量元素在偏离平衡的水平上被纳入快速生长晶体的程度。理论将结合最先进的原位分析测量，以开发一种用于定量晶体生长速率的通用工作流程。这项工作将对以下方面产生影响：1)喷发前的岩浆动力学；2)断层和裂缝在自然或诱发地震后愈合的速度；3)具有重要经济意义的矿藏在矿脉中沉淀的速度。这项工作还对控制熔体或溶液结晶释放潜热的速率有意义，这反过来又对可再生能源（太阳能和风能）的化学储存有意义。该项目的参与者还将参与莱斯大学地球、环境和行星科学系的几个社区外展项目：1)为该部门赞助的地球、环境和能源杂志《outcroings》制作内容；2)为休斯敦的K-12教师和学生提供地质教育；3)参加并组织一年一度的工业-水稻地球科学研讨会，该研讨会汇集了工业界和学术界的领导人，共同研究社会共同感兴趣的问题。本项目的目标是开发一种相对较新的晶体生长速度计，该计基于不平衡微量元素的掺入，否则这些微量元素将被晶体在平衡状态（不相容元素）所排斥。这种速度计将通过对晶体生长速率独立受限的实地研究进行校准来开发。一个基本目标将是评估在岩浆系统中如何观察到与晶体快速生长有关的常见不平衡效应。本文将利用高分辨率激光烧蚀电感耦合等离子体质谱和飞行时间二次离子体质谱对不同构造和火山环境下岩浆中的橄榄石进行综合采样，分析不相容的微量元素。然后将经验速度计应用于来自不同岩浆环境的橄榄石斑晶种群，以绘制种群内晶体生长速率的分布，特别强调解决斑晶是在长期岩浆房中缓慢生长还是在喷发前形成核并生长的问题。从这项工作中获得的见解将用于开发不同地质环境下的晶体生长模型，例如断层愈合和伟晶岩生成过程。

The purpose of this study is to better understand what controls how fast crystals can grow in simple and complex natural systems. For example, crystal growth has direct implications for predicting the conditions for volcanic eruptions because crystallization may induce the formation of bubbles or increase the viscosity of magma, both of which facilitate the build-up of the over-pressures needed for eruptions. Quantifying crystal growth rates would also provide insight into how long it takes for magma bodies to grow before they erupt catastrophically, generating hazardous conditions for life and human society. Adequate methods for constraining crystal growth rate, however, remain elusive. The goal of this work is to develop and calibrate a new crystal growth speedometer based on the extent to which trace elements are incorporated into a rapidly growing crystal at levels that deviate from equilibrium. Theory will be combined with state of the art in situ analytical measurements to develop a generalized workflow for quantifying crystal growth rates. This work will have implications for 1) magma dynamics prior to eruption, 2) the rate at which faults and cracks heal after a natural or induced earthquake and 3) the rates at which economically important mineral deposits are precipitated in veins. The work also has implications for controlling the rate of latent heat release by crystallization from melts or solutions, which in turn, has implications for chemical storage of renewable energies (solar and wind). Participants of this project will also be involved in several community outreach programs in the Department of Earth, Environmental and Planetary Sciences at Rice University: 1) content production for Outcroppings, a department sponsored magazine of the Earth, environment and energy, 2) geology education with K-12 teachers and students in Houston, and 3) participation and organizing of an annual industry-Rice Earth Science symposia that brings together leaders in industry and academia to work on problems of mutual societal interest.The goal of this project is to develop a relatively new crystal growth speedometer based on disequilibrium incorporation of trace elements that would otherwise be rejected by the crystal at equilibrium (incompatible elements). This speedometer will be developed by calibrating against field studies in which crystal growth rates have been independently constrained. A fundamental objective will be to evaluate how common disequilibrium effects associated with rapid crystal growth are observed in magmatic systems. A comprehensive sampling of olivines in magmas from different tectonic and volcanic settings will be analyzed for incompatible trace elements using state of the art high resolution laser ablation inductively coupled plasma mass spectrometry and time of flight secondary ion mass spectrometry. The empirical speedometer will then be applied to olivine phenocryst populations from different magmatic settings to map out the distribution of crystal growth rates within the population, with particular emphasis on resolving the question of whether phenocrysts grow slowly in a long-lived magma chamber or instead nucleated and grew just before eruption. Insights from this work will be used to develop models for crystal growth in different geologic settings, such as during fault healing and generation of pegmatites.