Collaborative Research: Assessment of Sulfur Recycling in Arc Magmatism through Secondary Ion Mass Spectrometry Study of Sulfur Isotopes in Experimental and Natural Mafic Glasses

知识价值。本提案要求资助基于含硫气体、硅酸盐熔体和冷凝S相（硫酸盐和硫化物）之间同位素分馏的全球硫回收的协作实验和分析研究。来自三个机构的科学家参与其中：美国自然历史博物馆（C. Mandeville，首席PI），伍兹霍尔海洋研究所（N. Shimizu， PI）和罗德岛大学（K. Kelley， PI）。拟议的研究包括两个独立的方面。首先，将进行实验室实验，确定共存相之间S同位素分馏的机制和大小，作为压力、温度、硅酸盐熔体化学成分、氧的逸度以及硅酸盐熔体和气相中S形态的函数。S同位素分析将使用Woods Hole海洋研究所的IMS 1280离子微探针进行二次离子质谱（SIMS）技术。这种用于硫同位素测量的SIMS新技术现在可以应用于熔融包裹体（10微米）尺度的硅酸盐玻璃，从而可以分析被困岩浆包裹体中的硫同位素，评估火山脱气，以及评估弧岩浆中硫的最终来源。在第二阶段，将测定以橄榄石、正辉石和斜辉石为寄主的玻璃包裹体的天然原始岩浆的S同位素组成；互补挥发性、亲石性和高场强微量元素丰度将在罗德岛通过激光烧蚀ICP-MS分析在同一玻璃上测定。对印度尼西亚加隆贡火山、意大利埃特纳火山和阿拉斯加州奥古斯丁火山样品进行研究，研究源区地幔S同位素组成、水逸度和氧逸度对硅酸盐熔体和含硫相S同位素分馏的影响以及脱气过程对硅酸盐熔体S同位素组成的影响。总之，这些研究路径有望建立S同位素地球化学的常规测量方法，作为俯冲带化学通量的强大示踪剂，并用于评估地球主要储层（地幔、岩石圈（包括地壳）和耦合水圈-大气）之间的硫循环。更广泛的影响。了解挥发性脱气对监测和预测火山爆发至关重要。也。提高对硫同位素地球化学的认识对减轻火山灾害至关重要。pi将把科学成果纳入各自机构的教育和推广计划。PI Kelley是一名早期职业女性科学家，由罗德岛大学国家科学基金会资助的ADVANCE项目提供支持，该项目旨在培养女性科学家的职业生涯。她将在这个项目的框架下指导一名海洋学暑期本科生研究奖学金（SURFO）学生（罗德岛大学，海洋学研究生院的nsf资助的REU计划）。PI Mandeville将在这个项目的第二年和第三年指导两名美国自然历史博物馆的REU学生。PI将作为讲师参加AMNH的城市科学教学培训更新（TRUST）计划，该计划为纽约市更多的高中地球科学教师提供专业发展机会。AMNH将在项目的每一年举办一次信托会议。

Intellectual merit. This proposal requests funding for acollaborative experimental and analytical study of global recycling of sulfur based on the isotopic fractionation between S-bearing gases, silicate melt, and condensed S phases (sulfate and sulfide). Scientists from three institutions are involved (American Museum of Natural History (C. Mandeville, lead PI), Woods Hole Oceanographic Institution (N. Shimizu, PI), and University of Rhode Island (K. Kelley, PI). The proposed research comprises two separate aspects. First, laboratory experiments will be carried out to determine mechanisms and magnitudes of S isotopic fractionations between coexisting phases as a function of pressure, temperature, chemical composition of silicate melt, fugacity of oxygen, and speciation of S in silicate melt and gas phase. S isotopic analysis will be made using secondary ion mass spectrometry (SIMS) techniques with the IMS 1280 ion microprobe at Woods Hole Oceanographic Institution. This new SIMS technique for sulfur isotopic measurements can now be applied to silicate glasses at the melt inclusion (10's of microns) scale thus allowing analysis of sulfur isotopes in trapped magma inclusions, evaluation of volcanic degassing, and assessment of the ultimate source of sulfur in arc magmas. In a second phase, S isotopic compositions will be determined for natural primitive magmas trapped as glass inclusions hosted by olivine, orthopyroxene and clinopyroxene; complementary volatile, lithophile and high field strength trace element abundances will be determined on the same glasses via laser ablation ICP-MS analysis at Rhode Island. This will be carried out for samples from Galunggung (Indonesia), Etna (Italy), and Augustine (Alaska), volcanoes so as to investigate S isotopic compositions of source mantle, effects of water and oxygen fugacity on S isotopic fractionation between silicate melt and S-bearing phases, and effects of degassing processes on S isotopic composition of silicate melts. Together, these research paths are expected to establish routine measurement of S isotope geochemistry as a powerful tracer for chemical fluxes across subduction zones and for assessment of sulfur recycling among Earth's major reservoirs (mantle, lithosphere (including crust), and coupled hydrosphere-atmosphere). Broader Impacts. Understanding of volatile degassing is central to monitoring and forecasting volcanic eruptions. Also. improved understanding of sulfur isotope geochemistry is vital to volcanic hazard mitigation. The PIs will incorporate the scientific results into educational and outreach programs at their respective institutions. PI Kelley is an early-career female scientist, supported by the University of Rhode Island's NSF-funded ADVANCE program, which is aimed at nurturing the careers of female scientists. She will advise a Summer Undergraduate Research Fellowship in Oceanography (SURFO) student (Univ. of Rhode Island, Graduate School of Oceanography's NSF-funded REU program) under the umbrella of this project. PI Mandeville will advise two American Museum of Natural History REU students in years 2 and 3 of this project. The PI will participate as a lecturer in the Training Renewal for Urban Science Teaching (TRUST) program at AMNH which provides professional development opportunities for greater New York City high school Earth science teachers. A TRUST session will be administered by AMNH in each year of the project.