NSFGEO-NERC: Sulfur Cycling at Subduction Zones

该项目由美国国家科学基金会地球科学理事会 (NSF/GEO) 和英国国家环境研究理事会 (NERC) 通过 NSF/GEO-NERC 牵头机构协议共同资助。该协议允许美国/英国的单一联合提案由其调查员拥有最大预算比例的机构提交并进行同行评审。在成功联合确定资助后，每个机构将资助与其本国相关的预算和调查人员的比例。硫是地球环境中的关键元素。当火山喷发时，硫磺被喷射到大气中，具有冷却作用。硫还是铅和锌等经济金属的运输剂和宿主。控制火山和金属矿藏中硫含量的一系列因素仍然是科学上的一个主要问题，也是本项目寻求回答的一个问题。硫的一种可能来源包括海底沉积物，这些沉积物潜入地球至岩浆形成的深处。该项目正在通过首次测量不同俯冲带火山系统的硫形态和通量来测试这一假设。 来自美国（哥伦比亚大学）、英国（牛津大学）和意大利（巴勒莫大学）的科学家团队将与德克萨斯农工大学的海洋钻探计划和爱丁堡大学的 NERC 离子微探针设施合作，对沉积物和火山物质中的硫及其同位素进​​行新的测量。大部分项目预算将支持哥伦比亚大学博士学位。学生、哥伦比亚大学本科生和牛津大学博士后。 Mather、Aiuppa 和 Plank 组成的 PI 团队将在国际会议上举办特别会议，并出版专注于深硫的特别期刊。该项目旨在研究岩浆系统中硫的起源，可能会在矿床的硫供应与收敛边缘的火山排放之间建立新的联系。该国际项目的目标是俯冲带硫循环的主要未知数。 US-NSF 该项目的重点将填补俯冲带地幔硫输入方面的关键知识空白。它将涉及对汤加、马里亚纳群岛、阿留申群岛、阿拉斯加和中美洲海沟沉积剖面的广泛分析，选择代表硫沉积和成岩作用以及极端同位素变化的端元海洋环境。海洋钻探计划岩心将通过 XRF 岩心扫描进行分析，这是一种量化异质分布的黄铁矿和重晶石（沉积物中硫的主要宿主）的战略方法。岩心扫描结果将指导巴勒莫大学通过元素分析仪-质谱联用进行散装硫和硫同位素分析的离散采样，重点关注可能出现在单个沉积部分中的硫化物与硫酸盐主导的区域。结果将是对最终成员海沟中硫的通量和同位素组成的首次全面估计（具有不确定性），并改进了全球估计。该项目的 UK-NERC 部分将采用一种新颖的方法来了解火山弧 S 的输出。它将首次测量未脱气橄榄石电弧熔体包裹体中的硫同位素组成。计划的工作将包括对来自与上述沉积物目标相同的俯冲系统的熔体包裹体套件进行深入研究。这将确保该项目的美国、英国和意大利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。该项目不仅将为任何俯冲带提供第一个全面的沉积物输入硫通量和岛弧同位素组成，还将测试相互竞争的假设，即岛弧火山硫的浓度和同位素组成反映a）俯冲输入或b）俯冲带中硫物质和同位素的分馏。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This is a project that is jointly funded by the National Science Foundation's Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.Sulfur is a critical element in Earth's environment. When volcanoes erupt, sulfur is ejected into the atmosphere with cooling effects. Sulfur is also the transport agent and host of economic metals such as lead and zinc. The cluster of factors that control how much sulfur is available to volcanoes and metal deposits is still a major question in science, one that this project seeks to answer. One possible source of sulfur includes the sediments on the seafloor, which are subducted into the Earth to the depths where magmas form. This project is testing this hypothesis by measuring for the first time the sulfur forms and fluxes that feed volcanic systems at different subduction zones. A team of scientists from the US (Columbia University), the UK (Oxford University) and Italy (University of Palermo) will partner with the Ocean Drilling Program at Texas A&M University and the NERC Ion Microprobe Facility at the University of Edinburgh to make novel measurements of sulfur and its isotopes in sediments and volcanic material. Most of the project budget will support a Columbia Ph.D. student, a Columbia undergraduate, and an Oxford postdoc. The PI Team of Mather, Aiuppa and Plank will incubate special sessions at international meetings and a special journal issue focused on Deep Sulfur. This project, aimed at the very origins of sulfur in magmatic systems, may lead to novel connections between the sulfur supply to ore deposits and volcanic emissions at convergent margins. This international project targets major unknowns in the sulfur cycle at subduction zones. The US-NSF focus of this project 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 by coupled Elemental Analyzer-Mass Spectrometry with a focus on the 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 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. 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, UK and Italian parts of this project, and allow for the first-time direct tracing of sulfur isotopes from sediment input to arc output. This project will not only provide the first comprehensive sediment input sulfur fluxes and arc isotopic compositions for any subduction zone, but also test the competing hypotheses that the concentrations and isotopic compositions of arc volcanic sulfur reflect a) the subducted inputs or b) the fractionation of sulfur species and isotopes in the subduction zone.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.