Collaborative Research: Geochemical variation of the Pacific crust subducting beneath the Izu-Bonin arc and its implications for the generation of arc magmas

合作研究：伊豆-小笠原弧下太平洋地壳俯冲的地球化学变化及其对弧岩浆生成的影响

• 批准号: 1333698
• 负责人: Paterno Castillo
• 金额: $ 33.78万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-05-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1333698&HistoricalAwards=false
• 关键词: Collaborative; Research; Geochemical; variation; Pacific

The Izu-Bonin arc in the western Pacific Ocean is one of the best-investigated volcanic arcs in the world and lead (Pb) isotopes are one of the foremost isotopic tracers of the recycling of altered ocean crust. It is widely accepted that there is a strong compositional link between magmas erupted along volcanic arcs above subduction zones and subducted altered oceanic crust that is cycling back down into the mantle via deep ocean trenches. That said, currently available Pb elemental and isotopic data for Izu-Bonin arc magmas and the associated subducting altered ocean crust are at odds with this model, raising the spector that altered ocean crust may not, in fact, be an important source of arc magmas, which throws into question our understanding of arc magmatism as a whole. This research will use geochemical analyses (elemental and isotopic) of new and already collected samples of ocean crust to determine whether there is a discrepancy between subduction zone input and arc output in the Izu-Bonin arc-trench system. Using a UNOLS ship, samples of basaltic crust will be dredged from the seafloor along a ~900 km transect targeting active, vertical fault scarps along the Pacific Plate which is subducting into the Izu-Bonin Trench. This transect allows sampling of rocks of a range of crustal ages, which will include samples from the area where there is a hypothesized change in the composition of Mesozoic Pacific crust at ~125 Ma. Samples will be analyzed for chemical composition and the results will be used to determine mass balances of slab input/arc output. The work will also entail a calibration of the magnetic timescale. Results of the investigation will provide a crucial test of current concepts on crustal recycling at subduction zones and modes of crustal extraction from the mantle in which the subduction processing of carbon plays a pivotal role. Goals of this research are linked directly to the science plan of the NSF-funded Integrated Ocean Drilling Program (IODP) and will provide essential data input to four upcoming IODP drilling expeditions (three JOIDES Resolution legs scheduled for 2014 and one CHIKYU expedition that is pending). Broader impacts of the project will foster national and international collaboration among the investigators and will support two investigators from groups under-represented in the sciences. The project also will support graduate and undergraduate students who will be fully integrated into the science discovery aspect of the project. Project results will be incorporated into a 1-day workshop for teachers from the San Diego Unified School District through the NSF-funded Center for Ocean Science Education Excellence in California.

西太平洋的Izu-bonin弧是世界上最经过评估的火山弧之一，铅（PB）同位素是最重要的同位素示踪剂之一，它是改变海壳的回收。人们普遍认为，沿着俯冲带上方的火山弧形爆发岩浆与俯冲的改变的海洋壳，通过深海沟向下循环回到地幔中。也就是说，目前可用于Izu-Bonin弧岩浆和相关的俯冲改变的海壳的PB元素和同位素数据与该模型不一，这引起了我们对整个弧岩浆主义的理解。这项研究将使用新的且已经收集的海壳样品的地球化学分析（元素和同位素），以确定Izu-Bonin Arc-Trench系统中俯冲带的输入和ARC输出之间是否存在差异。使用UNOLS船，将沿着约900 km的横断面靶向沿太平洋板的主动，垂直断层雪板从海底挖出的玄武岩样品，沿太平洋板，该板块俯冲到Izu-bonin沟渠中。该横断面允许对一系列地壳年龄的岩石进行采样，其中包括来自〜125 MA的中生代太平洋壳的组成的区域的样品。样品将进行化学成分分析，结果将用于确定平板输入/弧输出的质量平衡。这项工作还需要对磁性时间尺度进行校准。该研究的结果将对俯冲区域的地壳回收以及从地幔中的地壳提取模式的当前概念进行关键检验，碳的俯冲处理起着关键作用。这项研究的目标直接与NSF资助的综合海洋钻井计划（IODP）的科学计划有关，并将为即将到来的四次IODP钻探探险提供基本数据输入（2014年安排的三个开车式分辨率腿和一项尚待审查的尚待访问）。该项目的更广泛的影响将促进调查人员之间的国家和国际合作，并将支持来自科学不足的团体的两名调查人员。该项目还将支持将完全融入该项目的科学发现方面的毕业生和本科生。项目结果将通过加利福尼亚州NSF资助的海洋科学教育中心，为圣地亚哥统一学区的教师提供为期1天的研讨会。