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

合作研究：印度尼西亚 1257 Samalas 岩浆库的硫同位素系统学和氧逸度演化

• 批准号: 1820185
• 负责人: Marc-Antoine Longpre
• 金额: $ 15.32万
• 依托单位: CUNY Queens College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-15 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1820185&HistoricalAwards=false
• 关键词: Collaborative; Research; Sulfur; Isotope; Systematics

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.

硫是火山系统中第三丰富的挥发性元素，仅次于水和二氧化碳。火山喷发时向大气中释放的硫会扰乱全球气候，造成酸雨，对环境造成重大影响。1257年，印度尼西亚龙目岛上的萨玛拉斯火山爆发，造成了近2000年来最大的火山硫排放事件。这一事件与“小冰期”开始前后持续多年的全球变冷事件相吻合。这个项目的核心研究问题是：这座火山是如何积聚如此多的可喷发硫的？科学家参与者将通过深入探测硫化物、磷灰石和火山玻璃（快速冷却的熔体）中硫的性质和行为来测试硫富集机制的假设。该项目将利用最先进的分析技术来研究硫化学，其中许多是最近由研究小组的参与者开发的。这个项目将为火山下的岩浆系统积累足以对全球环境产生重大影响的可喷发硫储集层的能力提供新的见解。这项工作将支持几位早期职业研究人员，并将吸引不同群体的本科生参加纽约城市大学（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，其价态可以在与陆地岩浆系统相关的狭窄氧化还原范围内从S2-转变为S6+。这使得硫成为岩浆氧化还原条件变化的极好示踪剂，在1257年萨玛拉斯火山喷发期间，岩浆氧化还原条件可能在硫的运输、富集和释放中发挥了关键作用。所涉及的岩浆过程（例如脱气）应该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斯硫积累的动力学。矿物和玻璃中硫的价态将通过x射线吸收近边结构（XANES）光谱确定，而硫同位素比率将通过二次电离质谱（SIMS）测量。这种氧化还原和同位素研究的结合是解决与硫有关的科学问题的一种强有力的新方法。该项目将作为未来其他火山系统研究的蓝图，并将对岩浆硫化物成矿过程和地壳岩浆演化产生更广泛的地球科学界感兴趣的影响。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。