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，但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。这种深层碳循环，例如地球的大气演化和钻石的形成，但该循环的效率高度不确定，该项目将研究汤加群岛，该地区被认为是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循环的理想场所，因为它的采样深度为 100 至 300 公里，因为碳可能在比水更深的深度释放。该项目旨在利用最近的熔体包裹体测量再循环到汤加岛弧和劳盆地岩浆的俯冲碳和水。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，而这种现象很少被测量，而且在汤加弧区也从未被测量过。对于整个 Lau 盆地，只有一个已发表的熔体包裹体。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对汤加弧和劳弧后的熔体夹杂物和气泡进行实验再均化。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浓度的俯冲带，汤加群岛被重新夺回，从而产生了所有俯冲带中最少的碳量。初步数据和计算表明，很少有碳再循环到汤加弧，但有些可能会出现在弧后。该项目将提供对二氧化碳的首次全面估计。 （和 H2O）配对弧-弧后系统的一个主要更广泛的影响是社区再均化工作，鉴于已发表的 1000 个 CO2 丰度中的大多数都是这样，熔体包裹体的研究正在经历一场革命。实际上，现在需要重新审视所有熔体夹杂物研究，以量化收缩气泡中的二氧化碳浓度。为了应对这一挑战，研究人员将被邀请提交熔体夹杂物进行实验。在拉蒙特进行再均化，之后样本将被返回进行分析和出版，目标是生成 15-20 个含有恢复的 CO2 的新数据集，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。