Investigation of Secondary Water in Volcanic Glass and its Isotopic Signatures

由火山喷发的岩浆快速冷却而成的玻璃可能会告诉我们气候条件，因为这些材料在暴露在环境中时会与大气发生反应。水与火山玻璃的反应形成了一个水合带，反映了当时的气象条件。这些区域可以用氢和氧稳定同位素来测量，然后可以用来推断喷发时的环境条件。这项研究将通过实验、理论计算和自然观察相结合的方式来约束天然玻璃水合的地质机制。这类研究的结果将适用于危险废物处置的稳定性、考古环境中黑铁矿和硅质岩人工制品的改变以及珍珠岩的形成等问题，珍珠岩是一种重要的工业天然材料。对这些地质过程的了解还可以让我们了解火山口湖和卡特迈国家公园中的富马洛丘是如何形成的，以及如何通过地球、火星和其他大气中有水的行星上的遥感和火星车遥感来拍摄玻璃的水化变化。该项目将促进俄勒冈大学新设立的火山学集群租用计划之间的协同和合作，并将促进国际合作。资金将用于资助俄勒冈大学稳定同位素实验室的研究生和本科生以及分析基础设施。新推出的连续流动质谱学和微束方法现在首次允许相对容易地对火山玻璃进行多方法同位素调查。这项实验研究将研究硅玻璃和水从常温到水热(25至250摄氏度)的氢和三重氧同位素分馏系数。研究人员将用NanoSIMS和FTIR成像实验产品中的水化曲线，目标是水和D/H交换曲线，并对它们进行建模，以得出分馏和扩散参数。与合作者一起，他将对水合并与水交换的玻璃和类似沸石相进行从头算平衡同位素和数值动力学同位素分馏。新开发的氢同位素方法与玻璃中的三重氧同位素参数相结合，将为大气降水(冰期或间冰期)的水化创造预测标准。利用实验和文献数据中实验确定的水化和同位素趋势，该模型将预测矿床冷却期间的二次水化、蚀变和同位素趋势，以及渗流和沟道化水的输送，就像在气体泄漏管道中观察到的那样。上述结果对于理解褐沸石和熔岩侵位后的水-玻璃相互作用和古气候研究是相关的，因为硅酸盐玻璃在侵位后几个月到十几年的冷却过程中水合，提供了大气水同位素值的瞬时快照。与薄壁火山灰相比，快速水化的厚壁珍珠岩和富马孔泄漏管中的同位素参数是保存气候信号的更好目标，薄壁火山灰的水化时间超过1000年，平均可产生世纪至千年的信号。在对自然的应用中，该提案将通过专门针对动力学和水-岩石相互作用的持续时间来解释火山口湖尖顶和10000烟之谷的沉积物的起源，允许承认冰川和冰间水合作用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Glass formed by quick quenching of magma from erupting volcanoes may inform us about climatologic conditions because these materials react with the atmosphere when exposed to the environment. The reaction of water with volcanic glass creates a hydration zone that reflects the meteoric conditions at the time. These zones can be measured with hydrogen and oxygen stable isotopes that can then be used to infer the environmental conditions at the time of the eruption. This research will constrain geological mechanisms of hydration of natural glass with a combination of experiments, theoretical computations, and natural observations. Results of this type of research will be applicable to questions related to the stability of hazardous waste disposal, the alteration of obsidian and chert artifacts in archeological environments, and the formation of perlite that is an important natural material used in industry. Knowledge of these geological processes can also inform us on how fumarole mounds were formed in the Crater Lake and Katmai National Parks, and how hydration alteration of glass can be imaged with remote, and rover-based sensing on Earth, Mars and other planets that have water in their atmospheres. This project will promote synergy and collaboration among the newly created Volcanology cluster hire program at the University of Oregon and will promote international collaboration. Funding will support graduate and undergraduate students, and analytical infrastructure of the stable isotope lab at the University of Oregon.Newly available continuous flow mass spectrometric, and microbeam methods now permit multi-method isotopic investigation of volcanic glass with relative ease for the first time. The experimental study will investigate hydrogen and triple oxygen isotopic fractionation factors for silicic glasses and water from ambient to hydrothermal (25 to 250 C) temperatures. The investigator will image hydration profiles in experimental products with NanoSIMS and FTIR targeting water and D/H exchange profiles and model them to derive fractionation and diffusion parameters. With collaborators, he will perform ab initio equilibrium isotopic and numerical kinetic isotopes fractionation of glass and analogous zeolite phases upon hydration and exchange with water. The newly developed hydrogen isotope methods in combination with triple oxygen isotope parameters in glass will create predictive criteria for hydrating meteoric waters (glacial or interglacial). Using experimentally-determined hydration and isotopic trends from the experiments and literature data, the model will predict secondary hydration, alteration, and isotopic trends across the deposit during its cooling, with percolative and channelized water transport as is observed in gas escape pipes. The above results are relevant for understanding water-glass interaction after ignimbrite and lava emplacement, and for paleoclimate research, as silicic glass hydrates during cooling within months to 10s of years upon emplacement, providing instantaneous snapshots of meteoric water isotopic values. Isotopic parameters in rapidly hydrated thick-walled perlites and fumarole escape pipes are better targets for preservation of climatic signal than thin-walled ash that hydrates over 1000s of years and averages out century to millennia-scale signals. In application to nature, the proposal will explain the origin of Crater Lake Pinnacles and deposits at the Valley of 10,000 Smokes by specifically targeting kinetics and the duration of water-rock interactions, allowing the recognition of glacial vs. interglacial hydration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.