NSFGEO-NERC: Sulfur Cycling at Subduction Zones

这是一个由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的项目。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。在成功地联合确定一项裁决后，每个机构将为与其本国有关的预算和调查人员的比例提供资金。硫磺是地球环境的关键因素。当火山喷发时，硫被喷射到大气中，起到降温的作用。硫也是铅和锌等经济金属的运输剂和宿主。控制火山和金属矿床中硫含量的一系列因素仍然是科学中的一个主要问题，也是这个项目试图回答的一个问题。硫磺的一个可能来源包括海底的沉积物，它们被俯冲到地球深处形成岩浆的地方。该项目首次测量了供给不同俯冲带火山系统的硫的形态和流量，从而验证了这一假设。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离子微探测器设施合作，对沉积物和火山物质中的硫及其同位素进行新的测量。该项目的大部分预算将支持一名哥伦比亚大学博士生、一名哥伦比亚大学本科生和一名牛津大学博士后。Mather、Aiuppa和Plank的PI团队将在国际会议上孵化特别会议，并推出一期专注于深度硫磺的特别期刊。该项目针对的是岩浆系统中硫的来源，可能会导致矿藏的硫供应与汇聚边缘的火山排放之间的新联系。这一国际项目的目标是俯冲带硫循环中的主要未知数。该项目的美国-美国国家科学基金会的重点将填补S在俯冲带向地幔输入方面的关键知识空白。它将涉及对汤加海沟、马里亚纳海沟、阿留申海沟、阿拉斯加海沟和中美洲海沟沉积剖面的广泛分析，选择这些海沟来代表硫磺沉积和成岩作用以及极端同位素变化的终端海洋环境。大洋钻探项目的岩心将通过XRF岩心扫描进行分析，这是一种战略方法，用于量化不均匀分布的黄铁矿和重晶石，这是沉积物中硫的主要宿主。岩心扫描结果将指导巴勒莫大学使用元素分析仪-质谱仪进行批量硫和硫同位素分析的离散采样，重点放在单个沉积剖面中可能出现的硫化物主导与硫酸盐主导的区域。其结果将是对S进入终端成员海沟的通量和同位素组成的首次全面估计(具有不确定性)，并改进全球估计。这个项目的英国-国家科学研究中心将采用一种新的方法来理解S火山弧的输出。它将首次测量未脱气的橄榄石寄主弧形熔体包裹体中的硫同位素组成。计划中的工作将包括来自与上面沉积物目标相同的俯冲系统的经过充分研究的熔融包裹体套件。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弧光输出的硫同位素。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弧形同位素组成，而且还将检验相互竞争的假设，即弧形火山硫的浓度和同位素组成反映了a)俯冲输入或b)俯冲带硫物种和同位素的分馏。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.