Collaborative Research: Behavior of Boron During Prograde Diagenesis and Metamorphism of Pelagic Sediments from the Nankai Trough

合作研究：南海海槽远洋沉积物的成岩作用和变质作用中硼的行为

• 批准号: 2026692
• 负责人: Demian Saffer
• 金额: $ 19.21万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2026692&HistoricalAwards=false
• 关键词: Collaborative; Research; Behavior; Boron; During

Subduction zones, where one tectonic plate slides beneath another, are places where water, carbon dioxide and other chemical components are transferred between the Earth’s surface and interior. Some chemical components that enter into subduction zones are released back to the oceans (as water or gas); others contribute to magmas in volcanoes (where they become part of the crust as igneous rocks or are released to the atmosphere as volcanic gases) and still others are transported all the way into the deep interior of the Earth. Understanding how elements and compounds are divided between the surface and the interior of Earth can provide important information about the regulation of carbon dioxide levels in the atmosphere, the concentration of radioactive elements near the surface of the Earth, and the tendency of some volcanoes to erupt violently. This project uses the element boron, which is highly concentrated in seawater and ocean sediments compared to the interior of the Earth, to track the recycling of surface components through subduction zones. If we can measure the amount of boron entering into a subduction zone on the sea floor and how much boron is released by associated volcanoes and into the ocean, then we can calculate how much boron is recycled into the deep Earth. The workplan includes opportunities for intellectual exchange between collaborators in the United States, Italy, and Japan. Students at both the graduate and undergraduate levels will participate in and benefit from the collaborative exchange.Subduction zones are the primary locus for recycling of crustal materials into the Earth’s mantle, with important implications for mantle and continental crustal evolution throughout Earth history. Subducted sediments in particular contribute volatiles, trace elements, and unique isotopic signatures to the oceans, the mantle, and arc magmas. Boron is both highly fluid mobile and isotopically fractionated during thermally-driven desorption and metamorphic dehydration, making it an excellent tracer for both sediment and fluids. In contrast, Rare Earth Elements (HREE) and High Field Strength Elements (HFSE) are generally immobile, making them good tracers of sediment and basalt provenance. By observing the co-variation of B, d11B, and HREE/HFSE concentrations in progressively dehydrated marine clays and subsidiary basalts within a unique sample suite from the Nankai margin, we propose to constrain 1) the initial variability in slab inputs to the trench within a well-constrained segment of a single subduction zone; and 2) the evolution of sediment and released fluid composition through progressive desorption and dehydration prior to entering the sub-arc region. The workplan includes opportunities for intellectual exchange between collaborators in the United States, Italy, and Japan. Students at both the graduate and undergraduate levels will participate in and benefit from the international collaboration.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.

俯冲带是一个板块在另一个板块下方滑动的地方，是水、二氧化碳和其他化学成分在地球表面和内部之间转移的地方，进入俯冲带的一些化学成分会以水或气体的形式释放回海洋。 ）；其他物质在火山中形成岩浆（它们作为火成岩成为地壳的一部分，或作为火山气体释放到大气中），还有一些物质一直输送到地球深处，了解元素和化合物是如何形成的。地球表面和内部的划分可以提供有关大气中二氧化碳水平的调节、地球表面附近放射性元素的浓度以及一些火山猛烈喷发的趋势的重要信息。与地球内部相比，硼元素高度集中在海水和海洋沉积物中，如果我们能够测量进入海底俯冲带的硼量，就能追踪表面成分的循环。伴生物质释放出多少硼火山并进入海洋，然后我们可以计算有多少硼被回收到地球深处。该工作计划包括美国、意大利和日本的研究生和本科生之间的知识交流机会。俯冲带是地幔物质再循环的主要场所，对整个地球历史上的地幔和大陆地壳演化具有重要意义，特别是俯冲沉积物提供了挥发物、微量元素和独特的物质。海洋、地幔和弧岩浆的同位素特征，硼在热驱动的解吸和变质脱水过程中具有高度的流体流动性和同位素分馏性，使其成为沉积物和流体的极好示踪剂。 ）和高场强元素（HFSE）通常是固定的，这使得它们成为沉积物和玄武岩来源的良好示踪剂。 d11B 和 HREE/HFSE 浓度在南开边缘独特的样本套件中逐渐脱水的海洋粘土和附属玄武岩中，我们建议限制 1）在单次俯冲的良好约束段内输入海沟的板片的初始变化区域；2）在进入弧下区域之前通过逐步解吸和脱水来进行沉积物和释放的流体成分的演变。日本研究生和本科生都将参与国际合作并从中受益。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。