Volatile Recycling at Tonga-Lau: A Global End-Member

Tonga-Lau 的挥发性回收：全球最终成员

• 批准号: 2332776
• 负责人: Terry Plank
• 金额: $ 56.2万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-11-15 至 2026-10-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2332776&HistoricalAwards=false
• 关键词: Volatile; Recycling; Tonga; Lau; Global

Carbon-bearing sediments on the seafloor subduct into the deep earth. However, it is unclear how much carbon re-emerges at the surface in volcanic gases and eruptions and how much continues into the deep mantle. Many fundamental earth processes hang in the balance of this deep carbon cycle, such as the earth’s atmospheric evolution and the formation of diamonds, and yet the efficiency of this cycle is highly uncertain. This project will study the Tonga Islands, a location that is thought to output the least amount of carbon of any subduction zone. The Lau Basin, located behind the Tonga Islands is ideal for studying volatile recycling as it samples depths from 100 to 300 km. This is important, as carbon may be released at greater depths than water. Results will test recent predictions from models, calculations, and laboratory experiments and will apply to general carbon cycle models for other subduction zone systems. This project aims to measure the subducted carbon and water recycled to Tonga Arc and Lau Basin magmas using melt inclusions. Recent work has demonstrated how up to 90% of the CO2 in melt inclusions may be contained with their tiny shrinkage bubbles, which are rarely measured, and never have been for the Tonga arc. For the entire Lau Basin, there is a single published melt inclusion analysis with no CO2 measurement. Thus, the primary effort in this project is to experimentally rehomogenize melt inclusions and bubbles from the Tonga Arc and Lau back-arc using the piston cylinder apparatus and a technique developed at Lamont. All samples are available from existing collections. The Tonga islands are hypothesized to output the least amount of carbon of any subduction zone owing to the lack of carbon in subducting sediment input, a globally cold subducting slab that may not liberate substantial carbon beneath the volcanic arc, and a highly depleted mantle source. Preliminary data and calculations suggest that very little carbon recycles to the Tonga arc, but that some may emerge in the back-arc. This project will provide the first comprehensive estimates for CO2 (and H2O) for a paired arc-back-arc system. A major broader impact of this project is a Community Rehomogenization effort. The study of melt inclusions is undergoing a revolution, given the recognition that most of the 1000’s of published CO2 abundances are greatly under-estimated. Virtually every melt inclusion study now needs to be revisited in order to quantify the CO2 concentration in the shrinkage bubble. In order to meet this challenge, researchers will be invited to submit melt inclusions for experimental rehomogenization at Lamont, after which samples will be returned for analysis and publication. The goal is to generate 15-20 new datasets with restored CO2, prioritizing those that have coupled CO2/S volcanic gas records. This project will also support a PhD student.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.

海底的含碳沉积物俯冲到地球深处。然而，目前尚不清楚有多少碳在火山气体和喷发中重新出现在地表，以及有多少碳继续进入地幔深处。许多基本的地球过程都依赖于这种深层碳循环的平衡，例如地球的大气演化和钻石的形成，但这种循环的效率却高度不确定。该项目将研究汤加群岛，该地区被认为是所有俯冲带中碳排放量最少的地区。位于汤加群岛后面的劳盆地是研究挥发性物质回收的理想场所，因为它的采样深度为 100 至 300 公里。这很重要，因为碳可能释放到比水更深的地方。结果将测试模型、计算和实验室实验的最新预测，并将适用于其他俯冲带系统的一般碳循环模型。该项目旨在利用熔体包裹体测量再循环到汤加弧和劳盆地岩浆中的俯冲碳和水。最近的研究表明，熔体包裹体中高达 90% 的 CO2 可能包含在微小的收缩气泡中，但这些气泡很少被测量，而且汤加岛弧也从未被测量过。对于整个 Lau 盆地，有一个已发表的熔体包裹体分析，没有 CO2 测量。因此，该项目的主要工作是使用活塞缸装置和拉蒙特开发的技术，通过实验重新均质来自汤加弧和劳弧后的熔体夹杂物和气泡。所有样品均可从现有收藏中获得。由于俯冲沉积物输入中缺乏碳、全球寒冷的俯冲板片可能不会在火山弧下方释放大量碳以及高度贫化的地幔源，汤加群岛被认为是所有俯冲带中碳排放量最少的。初步数据和计算表明，很少有碳循环到汤加弧，但有些可能会出现在弧后。该项目将为成对的弧-弧后系统提供二氧化碳（和水）的首次综合估算。该项目更广泛的主要影响是社区再均化的努力。鉴于人们认识到已发表的数千个二氧化碳丰度中的大多数都被大大低估了，熔体包裹体的研究正在经历一场革命。现在几乎所有熔体夹杂物研究都需要重新审视，以量化收缩气泡中的二氧化碳浓度。为了应对这一挑战，研究人员将被邀请提交熔体夹杂物以在拉蒙特进行实验再均化，之后样品将被返回进行分析和发表。目标是使用恢复的 CO2 生成 15-20 个新数据集，优先考虑那些耦合了 CO2/S 火山气体记录的数据集。该项目还将支持一名博士生。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。