近日，英国南安普敦大学Rosalind M. Coggon团队研究了一个由海洋地壳角砾岩承载的地质碳循环汇。2025年11月24日出版的《自然—地球科学》杂志发表了这项成果。
在老化海洋地壳中，碳酸钙沉淀通过海底风化反应封存溶解于海水中的二氧化碳，这一过程在百万年时间尺度上影响大气CO2浓度。然而，这一地壳碳汇及其在洋中脊扩张过程中与CO2脱气作用的平衡程度，由于对持续数百万年CO2吸收的广阔洋脊斜坡采样不足，仍缺乏定量研究。
研究组通过国际大洋发现计划南大西洋横跨航次390航次对大西洋中脊慢速扩张带6100万年前断层作用形成的碎屑角砾岩进行钻探，量化了其中的碳汇。这些碎屑角砾岩形成于断层作用导致的大规模崩塌堆积，经过4000万年碳酸盐胶结作用，封存了约7.5 wt%的海水来源CO2，含量是先前钻探的上部地壳的2至40倍。基于断层几何形态估算的碎屑角砾岩丰度表明，慢速扩张洋脊形成的碎屑可容纳相当于其下部地壳形成过程中释放CO2量的大部分。随着扩张速率降低，板块离散中由断层作用（及碎屑形成）所占比例呈非线性增加。因此，历史扩张速率的变化可能影响海洋地壳CO2释放与吸收在全球碳循环中的平衡。
附：英文原文
Title: A geological carbon cycle sink hosted by ocean crust talus breccias
Author: Coggon, Rosalind M., Carter, Elliot J., Grant, Lewis J. C., Evans, Aled D., Lowery, Christopher M., Teagle, Damon A. H., Kempton, Pamela D., Cooper, Matthew J., Routledge, Claire M., Albers, Elmar, Estep, Justin, Christeson, Gail L., Harris, Michelle, Belgrano, Thomas M., Sylvan, Jason B., Reece, Julia S., Estes, Emily R., Williams, Trevor
Issue&Volume: 2025-11-24
Abstract: Calcium carbonate precipitation in ageing ocean crust sequesters carbon dioxide dissolved in seawater through seafloor weathering reactions, influencing atmospheric CO2 concentrations on million-year timescales. However, this crustal carbon sink, and the extent it balances CO2 degassing during crustal formation at mid-ocean ridges, remain poorly quantified due to limited sampling of the vast ridge flanks where CO2 uptake continues for millions of years. Here we quantify the carbon sink hosted within talus breccias that accumulated through mass wasting 61 million years ago during rift faulting at the slow spreading Mid-Atlantic Ridge, cored during International Ocean Discovery Program South Atlantic Transect Expedition 390. After 40 million years of carbonate cementation, these breccias contain ~7.5wt% seawater-derived CO2, 2 to 40 times more than previously cored upper crust. Our estimates of talus breccia abundance based on fault geometries indicate that talus formed at slow-spreading ridges can accommodate a CO2 sink equivalent to a large proportion of the CO2 released during accretion of the underlying crust. The proportion of plate divergence accommodated by faulting, and hence talus abundance, increases nonlinearly with decreasing spreading rate. Consequently, past variations in spreading rate may have impacted the balance between ocean crust CO2 release and uptake in Earth’s carbon cycle.
DOI: 10.1038/s41561-025-01839-5
Source: https://www.nature.com/articles/s41561-025-01839-5