CAREER: Tracing sulfur in subducting slabs with apatite oxybarometry

职业：用磷灰石氧压计追踪俯冲板片中的硫

• 批准号: 2236903
• 负责人: Megan Holycross
• 金额: $ 81.95万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2028-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2236903&HistoricalAwards=false
• 关键词: CAREER; Tracing; sulfur; subducting; slabs

Tectonic plate boundaries are important loci of mass transfer in the Earth system. The transfer of volatile elements from Earth’s deep interior to its surface and atmosphere at subduction zones enables a habitable planet. Magmas erupted at arc volcanoes, located at subduction zones, are more oxidized than magmas erupted at mid-ocean ridges. Arc volcanoes are the basis of the continental crust and host economic ore deposits. Quantifying the processes that lead to the oxidation of magmas in subduction zones is then critical for understanding the formation of continents and ores. This project will investigate the hypothesis that the transfer of sulfur throughout the subduction system is responsible for the elevated oxidation state of arc magmas. High-pressure experiments will be executed to measure the behavior of sulfur in rocks at subduction zone conditions. Experimental results will be used to inform observations of natural subduction-related rocks. This project includes research and mentoring experiences for a postdoctoral associate, a PhD student and two undergraduate students from underrepresented groups. Project results will be assimilated into new open access Earth science educational content. A hybrid capstone outreach event will be held to disseminate research outcomes to the public.This study will examine the hypothesis that the oxidized signature of arc magmas is due to the transfer of sulfate from metamorphosed oceanic crust on the down-going slab to the overlying arc mantle. High-pressure experiments will be executed to calibrate a new proxy for the oxidation state of subduction-related rocks based on the incorporation and valence state of sulfur in the mineral apatite. Experimental apatite will be co-crystallized with sulfide or sulfate phases such that the behavior of sulfur in apatite can be used to provide indirect information on the relative stabilities of sulfide vs. sulfates in subducted oceanic crust. Results from the experiments will be applied to determine the oxidation states of suites of apatite-bearing metabasites to determine if subducting slabs record an increase in oxidation state concurrent with the increase in dissolved oxygen in the deep oceans and rise in seawater sulfate in the Early Phanerozoic.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.

构造板块边界是地球系统中物质转移的重要场所，挥发性元素从地球内部深处转移到俯冲带的表面和大气，使得位于俯冲带的弧火山喷发的岩浆更加氧化。与大洋中脊喷发的岩浆相比，弧火山是大陆地壳的基础，也是经济矿藏的量化过程。俯冲带对于了解大陆和矿石的形成至关重要，该项目将研究硫在整个俯冲系统中的转移导致弧岩浆氧化态升高的原因。俯冲带条件下岩石中硫的行为将用于指导对自然俯冲相关岩石的观察。该项目包括一名博士后助理、一名博士生和两名本科生的研究和指导经验。项目结果将被纳入新的开放获取地球科学教育内容中，将举行混合顶点推广活动，向公众传播研究成果。这项研究将检验弧岩浆的氧化特征是由于将进行硫酸盐从下降板片上的变质洋壳转移到上覆弧地幔的高压实验，以校准氧化态的新代理。基于矿物磷灰石中硫的掺入和价态的俯冲相关岩石实验磷灰石将与硫化物或硫酸盐相共结晶，以便磷灰石中硫的行为可用于提供有关硫的相对稳定性的间接信息。俯冲洋壳中的硫化物与硫酸盐的实验结果将用于确定一组物质的氧化态。含磷灰石变碱岩，以确定俯冲板片是否记录了氧化态的增加，同时伴随着深海溶解氧的增加和显生宙早期海水硫酸盐的增加。该奖项反映了 NSF 的法定使命，并被认为值得通过以下方式获得支持：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。