NSFGEO-NERC: Sulfur Cycling at Subduction Zones

俯冲带是调节全球S加工和弧火山作用的气候效应、弧岩浆的经济潜力和固体地球储层氧化态的关键阀门。然而，在整个俯冲系统中，S的输入、加工和再循环仍然是不准确的。这个国际项目的目标是在俯冲带硫磺循环的主要未知数。该项目的美国国家科学基金会（US-NSF）重点项目（PI Plank， LDEO）将填补俯冲带地幔S输入方面的关键知识空白。它将涉及对汤加、马里亚纳、阿留申群岛、阿拉斯加和中美洲海沟沉积剖面的广泛分析，这些海沟被选为硫沉积、成岩作用和极端同位素变化的末端海洋环境的代表。海洋钻探计划的岩心将通过XRF岩心扫描进行分析，这是一种量化非均质浸染的黄铁矿和重晶石的战略方法，它们是沉积物中硫的主要寄主。岩心扫描结果将指导巴勒莫大学与Aiuppa教授和Vizzini教授合作进行散装硫和硫同位素分析的离散采样。在巴勒莫收集的试验数据证明了元素分析仪-质谱联用技术的质量，以及在单个沉积剖面中可能出现的硫化物与硫酸盐主导的清晰状态。结果将是对S进入端元海沟的通量和同位素组成的第一次综合估计（具有不确定性）和改进的全球估计。这个项目的英国- nerc部分（PI Mather, Oxford）将采用一种新的方法来理解火山弧S输出。它将首次测量未脱气的含橄榄石的电弧熔体包裹体中的硫同位素组成。爱丁堡NERC离子探针设备收集的试验数据证明了该技术的可行性，并在Fuego火山的熔体包裹体中产生了正的δ (34)S。计划中的工作将包括对来自与沉积物目标（上图）相同俯冲系统的熔融包裹体套件进行充分研究。这将确保该项目的美国和英国部分之间的密切合作，并允许首次直接追踪从沉积物输入到电弧输出的硫同位素。

Subduction zones are a key valve mediating global S processing and the climatic effects of arc volcanism, the economic potential of arc magmas, and the oxidation state of solid Earth reservoirs. Yet, the inputs, processing and recycling of S throughout the subduction system are still inaccurately known. This international project targets major unknowns in the sulfur cycle at subduction zones. The US-NSF focus of this project (PI Plank, LDEO) will fill a key knowledge gap in terms of S inputs to the mantle at subduction zones. It will involve extensive analysis of sedimentary sections at the Tonga, Marianas, Aleutians, Alaska and Central America trenches, chosen to represent end-member oceanic environments for sulfur deposition and diagenesis and extreme isotopic variations. Ocean Drilling Programs cores will be analyzed by XRF core scanning, a strategic approach to quantify heterogeneously disseminated pyrite and barite, major hosts of sulfur in sediment. Core scanning results will guide discrete sampling for bulk sulfur and sulfur isotope analyses at the University of Palermo, in collaboration with Prof. Aiuppa and Vizzini. Pilot data collected in Palermo demonstrate the quality of the coupled Elemental Analyzer-Mass Spectrometry technique and the clear sulfide- vs. sulfate-dominated regimes that may occur in a single sedimentary section. The outcome will be the first comprehensive estimates (with uncertainties) for the fluxes and isotopic compositions of S into end-member trenches and improved global estimates.The UK-NERC part of this project (PI Mather, Oxford) will take a novel approach to understanding volcanic arc S outputs. It will measure for the first time the sulfur isotopic composition in undegassed olivine-hosted arc melt inclusions. Pilot data collected at NERC Ion Microprobe Facility at Edinburgh demonstrate the viability of the technique, and yield positive delta(34)S in melt inclusions from Fuego volcano. Planned work will include well-studied melt inclusions suites from the same subducting systems as the sediment targets (above). This will ensure close collaboration between the US and UK parts of this project, and allow for the first-time direct tracing of sulfur isotopes from sediment input to arc output.