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.

海底俯冲上的碳沉积物进入深地球。但是，目前尚不清楚火山气体和喷发的表面重新出口多少，以及多少持续到深陆壁上。许多基本的地球过程悬在了这个深碳循环的平衡中，例如地球的大气进化和钻石的形成，但是该循环的效率高度不确定。该项目将研究汤加群岛，汤加群岛被认为可以输出任何俯冲带的最少碳。位于汤加群岛后面的Lau盆地是研究挥发性回收的理想选择，因为它的深度从100到300公里。这很重要，因为碳的深度可能比水更大。结果将从模型，计算和实验室实验中测试最新预测，并将适用于其他俯冲区系统的一般碳循环模型。该项目旨在使用熔体夹杂物测量俯冲的碳和水回收到汤加弧和刘盆地岩浆。最近的工作表明，熔体夹杂物中多达90％的二氧化碳如何包含其微小的收缩气泡，很少被测量，并且从来没有用于汤加弧。对于整个LAU盆地，都有一个发表的熔体融合分析，没有CO2测量。这是该项目的主要努力是使用活塞缸设备和Lamont开发的一种技术，通过实验重新调整汤加弧和LAU背面的熔体夹杂物和气泡。所有样本均可从现有收藏中获得。假设汤加群岛是由于俯冲沉积物输入中缺乏碳，这是一个全球冷俯冲板，以输出任何俯冲带的最少碳，这是一个可能不会在火山弧下方释放大量碳的全球冷俯冲板，并且是高度耗尽的壁炉架。初步数据和计算表明，汤加弧的碳回收很少，但是有些可能会在后弧中出现。该项目将为配对的ARC-BACK-ARC系统提供第一个二氧化碳（和H2O）的综合估计。该项目的主要广泛影响是社区重新构成的工作。鉴于1000年代已发表的二氧化碳丰度中的大多数人中，对融合物的研究正在进行革命。实际上，现在需要重新审视每项熔体纳入研究，以量化收缩气泡中的二氧化碳浓度。为了应对这一挑战，将邀请研究人员在拉蒙特（Lamont）提交熔体包含物以进行实验重新生成，然后将返回样品进行分析和出版。目的是生成15-20个具有恢复CO2的新数据集，并将其优先考虑与CO2/S火山气体记录耦合的数据集。该项目还将支持博士生。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估，被认为是珍贵的支持。