Methane-derived authigenic carbonates – A case for a globally relevant marine carbonate factory

• Published in: Earth-science reviews Vol. 243; p. 104487
• Main Authors: Akam, Sajjad A., Swanner, Elizabeth D., Yao, Hongming, Hong, Wei-Li, Peckmann, Jörn
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2023
• Subjects: Authigenic carbonates; Carbon burial; Carbon sequestration; Carbonate factories; Cold seeps; Gas hydrates; Geological carbon cycling; Marine carbon budget; Marine silicate weathering; Methane cycling; Methane derived authigenic carbonate; Methane seeps; Methane-derived carbonates; Methanogenic carbonate; Ocean acidification; Marine silicate weathering; Methane cycling; Methane derived authigenic carbonate; Methane-derived carbonates; Cold seeps; Authigenic carbonates; Marine carbon budget; Ocean acidification; Carbon sequestration; Carbon burial; Methanogenic carbonate; Carbonate factories; Geological carbon cycling; Gas hydrates; Methane seeps
• ISSN: 0012-8252; 1872-6828; 1872-6828
• DOI: 10.1016/j.earscirev.2023.104487

Precipitation of methane-derived authigenic carbonates (MDAC) is an integral part of marine methane production and consumption, but MDAC's relative significance to the global marine carbon cycle is not well understood. Here we provide a synthesis and perspective to highlight MDAC from a global marine carbon biogeochemistry viewpoint. MDAC formation is a result and archive of carbon‑sulfur (CS) coupling in the shallow sulfatic zone and carbon‑silicon (CSi) coupling in deeper methanic sediments. MDAC constitute a carbon sequestration of 3.93 Tmol C yr−1 (range 2.34–5.8 Tmol C yr−1) in the modern ocean and are the third-largest carbon burial mechanism in marine sediments. This burial compares to 29% (11–57%) organic carbon and 10% (6–23%) skeletal carbonate carbon burial along continental margins. MDAC formation is also an important sink for benthic alkalinity and, thereby, a potential contributor to bottom water acidification. Our understanding of the impact of MDAC on global biogeochemical cycles has evolved over the past five decades from what was traditionally considered a passive carbon sequestration mechanism in a seep-oasis setting to what is now considered a dynamic carbonate factory expanding from deep sediments to bottom waters—a factory that has been operational since the Precambrian. We present a strong case for the need to improve regional scale quantification of MDAC accumulation rates and associated carbonate biogeochemical parameters, leading to their incorporation in present and paleo‑carbon budgets in the next phase of MDAC exploration.