TY - JOUR A1 - Fiebig, Jens A1 - Stefánsson, Andri A1 - Ricci, Andrea A1 - Tassi, Franco A1 - Viveiros, Fatima A1 - Silva, Catarina A1 - Lopez, Taryn A1 - Schreiber, Christoph A1 - Hofmann, Sven A1 - Mountain, Bruce W. T1 - Abiogenesis not required to explain the origin of volcanic-hydrothermal hydrocarbons T2 - Geochemical perspectives letters N2 - Abiotic formation of n-alkane hydrocarbons has been postulated to occur within Earth's crust. Apparent evidence was primarily based on uncommon carbon and hydrogen isotope distribution patterns that set methane and its higher chain homologues apart from biotic isotopic compositions associated with microbial production and closed system thermal degradation of organic matter. Here, we present the first global investigation of the carbon and hydrogen isotopic compositions of n-alkanes in volcanic-hydrothermal fluids hosted by basaltic, andesitic, trachytic and rhyolitic rocks. We show that the bulk isotopic compositions of these gases follow trends that are characteristic of high temperature, open system degradation of organic matter. In sediment-free systems, organic matter is supplied by surface waters (seawater, meteoric water) circulating through the reservoir rocks. Our data set strongly implies that thermal degradation of organic matter is able to satisfy isotopic criteria previously classified as being indicative of abiogenesis. Further considering the ubiquitous presence of surface waters in Earth’s crust, abiotic hydrocarbon occurrences might have been significantly overestimated. KW - hydrocarbons KW - volcanic gases KW - abiogenesis Y1 - 2019 UR - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/51257 UR - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-512579 SN - 2410-3403 SN - 2410-339X N1 - Published by the European Association of Geochemistry under Creative Commons License CC BY-NC-ND 4.0 VL - 11 SP - 23 EP - 27 PB - Assoc. CY - [Paris] ER -