On the production and fate of volatile fatty acids in hydrothermal fluids

Volatile fatty acids (VFAs or short-chain carboxylic acids) are key intermediates in biological and abiotic carbon transformations across geological fluids. Although well studied in sedimentary porewaters, their distribution in deep-sea hydrothermal fluids remains poorly constrained. Formate and acetate, central to hydrothermal origin-of-life models and shaped by diverse abiotic and biotic processes, are rarely quantified in these settings due to analytical challenges associated with saline matrices. Better constraints on VFA distributions would shed new light on carbon cycling in Earth’s heated crust and in hydrothermal environments on ocean worlds such as Europa and Enceladus.

This seminar will introduce a new high-pressure ion chromatography (HPIC) method for VFA analysis in saline waters (Pereira et al., 2025), offering high sensitivity and low detection limits without sample pre-treatment, derivatization, or large fluid volumes. Using this approach, VFA data from 66 hydrothermal fluids across 10 systems spanning the Arctic, Pacific, and Atlantic mid-oceanic ridges will be presented, along with pathways (abiotic, thermogenic, and biotic) governing their production and consumption.