Investigation of Secondary Water in Volcanic Glass and its Isotopic Signatures

由火山喷发的岩浆快速淬火形成的玻璃可以告诉我们气候条件，因为这些物质暴露在环境中时与大气发生反应。水与火山玻璃的反应产生了一个水合带，反映了当时的气象条件。这些区域可以用氢和氧的稳定同位素来测量，然后可以用来推断喷发时的环境条件。本研究将通过实验、理论计算和自然观测相结合，对天然玻璃水化的地质机制进行约束。这类研究的结果将适用于与下列问题有关的问题：危险废物处置的稳定性、考古环境中黑曜石和燧石文物的变化以及珍珠岩的形成（珍珠岩是工业中使用的重要天然材料）。对这些地质过程的了解还可以告诉我们火山口湖和卡特迈国家公园里的喷气孔丘是如何形成的，以及如何利用地球、火星和其他大气中有水的行星上的远程和基于探测器的传感器来成像玻璃的水化变化。该项目将促进俄勒冈大学新成立的火山学集群招聘项目之间的协同与合作，并将促进国际合作。资金将用于支持研究生和本科生，以及俄勒冈大学稳定同位素实验室的分析基础设施。新出现的连续流动质谱和微束方法使得火山玻璃的多方法同位素研究第一次相对容易。实验研究将研究从环境温度到热液温度（25至250℃）下硅玻璃和水的氢和三氧同位素分馏因素。研究人员将利用NanoSIMS和FTIR成像实验产品的水化特征和D/H交换特征，并对它们进行建模，以获得分馏和扩散参数。与合作者一起，他将在水化和与水交换时对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结合玻璃中的三氧同位素参数将创建水化大气水（冰期或间冰期）的预测标准。利用实验和文献数据中确定的水化和同位素趋势，该模型将预测整个矿床在冷却期间的二次水化、蚀变和同位素趋势，以及在气体逸出管道中观察到的渗透和渠化水输送。上述结果有助于理解火烟煤和熔岩就位后的水玻璃相互作用，也有助于古气候研究，因为硅玻璃在就位后数月至10年的冷却过程中会发生水合物，从而提供了大气水同位素值的瞬时快照。与薄壁火山灰相比，快速水合的厚壁珍珠岩和火山喷发孔逸出管中的同位素参数是保存气候信号的更好目标，因为薄壁火山灰的水合时间超过1000年，并将世纪到千年尺度的信号平均下来。在自然界的应用中，该提案将通过特别针对动力学和水-岩石相互作用的持续时间来解释火山口湖尖峰和10,000烟谷沉积物的起源，从而识别冰川与间冰期的水化作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.