Collaborative Research: Sulfur Isotope Systematics and Oxygen Fugacity Evolution in the 1257 Samalas Magma Reservoir, Indonesia

硫是火山系统中仅次于水和CO2的第三大挥发性元素。火山爆发时释放到大气中的硫会扰乱全球气候，造成酸雨，对环境造成重大影响。火山爆发1257年，印度尼西亚龙目岛上的萨马拉火山爆发，产生了过去2000年来最大的火山硫排放事件。这一事件与“小冰河时代”开始时的多年全球变冷事件相吻合。“这个项目的中心研究问题是：这座火山是如何积累了这么多可喷发的硫磺的？科学家参与者将测试硫富集机制的假设，深入探讨硫的性质和硫化物，磷灰石和火山玻璃（快速冷却的熔体）从这次喷发的浮石样本中的行为。该项目将利用最先进的分析技术来研究硫化学，其中许多技术是由研究小组的参与者最近开发的。该项目将对火山下岩浆系统的能力产生新的见解，以积累足够大的可喷发硫库，从而对全球环境产生重大影响。这项工作将支持几个早期的职业研究人员，并将吸引不同的本科生群体参加纽约（CUNY）和美国自然历史博物馆（AMNH）。该项目利用硫的复杂地球化学行为来跟踪其在岩浆系统中从液相（硅酸盐熔体）到固相（矿物）和气相的运动。硫是一种多价元素，其价态可在与陆地岩浆系统相关的狭窄氧化还原范围内从S2-变为S6+。这使得硫成为岩浆氧化还原条件变化的一个很好的示踪剂，这些条件可能在1257 Mt.萨马拉斯喷发。所涉及的岩浆过程（例如，除气）应导致玻璃和矿物中硫同位素的可预测分馏，这将进一步限制萨马拉硫积累的动力学。矿物和玻璃中硫的价态将通过X射线吸收近边结构（XANES）光谱测定，而硫同位素比将通过二次电离质谱（西姆斯）测定。这种对氧化还原和同位素研究的回顾是解决硫相关科学问题的一种强有力的新方法。该项目将作为其他火山系统未来研究的蓝图，并将对更广泛的地球科学界感兴趣的岩浆硫化物成矿过程和地壳岩浆演化产生影响。该奖项反映了NSF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。

Sulfur is the third most abundant volatile element in volcanic systems following water and CO2. Release of sulfur to the atmosphere during volcanic eruptions can perturb climate on a global scale and cause acid rain, resulting in significant environmental impact. The eruption of Mt. Samalas on Lombok Island, Indonesia, in 1257 generated the largest volcanic sulfur emission event of the last 2000 years. This event is coincident with a multi-year global cooling event around the beginning of the "Little Ice Age." The central research question of this project is: how did this volcano build up so much eruptible sulfur? The scientist participants will test hypotheses of sulfur enrichment mechanisms by probing deep into sulfur's properties and behavior within sulfides, apatites, and volcanic glasses (rapidly cooled melts) from pumice samples from this eruption. The project will utilize the most advanced analytical techniques to investigate sulfur chemistry, many of which were developed recently by participants on the research team. This project will yield new insights into the capability of magmatic systems beneath volcanoes to accumulate reservoirs of eruptible sulfur large enough to create significant global environmental impacts. This work will support several early-career researchers, and will engage a diverse group of undergraduate students to participate at City University of New York (CUNY) and the American Museum of Natural History (AMNH). The project exploits the complex geochemical behavior of sulfur to track its movement from the liquid phase (silicate melt) into solid (mineral) and gas phases in magmatic systems. Sulfur is a polyvalent element that can change its valence state from S2- to S6+ over a narrow redox range relevant for terrestrial magmatic systems. This makes sulfur an excellent tracer for changes in magma redox conditions that may have played a critical role in the transport, enrichment, and release of sulfur during the 1257 Mt. Samalas eruption. The involved magmatic processes (e.g., degassing) should lead to predictable fractionations of sulfur isotopes in glasses and minerals, which will further constrain the dynamics of sulfur build-up at Samalas. The valence states of sulfur in minerals and glasses will be determined via X-ray absorption near-edge structure (XANES) spectroscopy, whereas sulfur isotope ratios will be measured by secondary ionization mass spectrometry (SIMS). This dovetailing of redox and isotope studies is a powerful new approach to addressing sulfur-related science questions. This project will serve as a blueprint for future studies of other volcanic systems and will have implications for magmatic sulfide ore-forming processes and crustal magma evolution of interest to the broader Earth science community.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.