Back to article

Figures and tables

Abiogenesis not required to explain the origin of volcanic-hydrothermal hydrocarbons

J. Fiebig1,

1Institute of Geosciences, Goethe University, Altenhöferallee 1, 60438 Frankfurt/Main, Germany

A. Stefánsson2,

2Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik, Iceland

A. Ricci3,

3Department of Biological, Geological and Environmental Sciences, University of Bologna, Piazza di Porta San Donato 1, 40126 Bologna, Italy

F. Tassi4,

4Department of Earth Sciences, University of Florence, Via La Pira 4, 50121 Florence, Italy

F. Viveiros5,

5Institute of Volcanology and Risks Assessment (IVAR), Universidade dos Açores, Rua da Mae de Deus, 9501-801 Ponta Delgada, Portugal

C. Silva5,6,

5Institute of Volcanology and Risks Assessment (IVAR), Universidade dos Açores, Rua da Mae de Deus, 9501-801 Ponta Delgada, Portugal
6Centre for Information and Seismovolcanic Surveillance of the Azores, Rua da Mãe de Deus, 9501-801 Ponta Delgada, Portugal

T.M. Lopez7,

7Geophysical Institute, Alaska Volcano Observatory, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775, USA

C. Schreiber1,

1Institute of Geosciences, Goethe University, Altenhöferallee 1, 60438 Frankfurt/Main, Germany

S. Hofmann1,

1Institute of Geosciences, Goethe University, Altenhöferallee 1, 60438 Frankfurt/Main, Germany

B.W. Mountain8

8GNS Science, Wairakei Research Centre, 114 Karetoto Road, Taupo 3384, New Zealand

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Fiebig, J., Stefánsson, A., Ricci, A., Tassi, F., Viveiros, F., Silva, C., Lopez, T.M., Schreiber, C., Hofmann, S., Mountain, B.W. (2019) Abiogenesis not required to explain the origin of volcanic-hydrothermal hydrocarbons. Geochem. Persp. Let. 11, 23–27.

German Science Foundation (DFG; grant FI 948/8-1).

Geochemical Perspectives Letters 11  |  doi: 10.7185/geochemlet.1920
Received 11 April 2019  |  Accepted 25 June 2019  |  Published 29 July 2019
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0




Figure 1 Plot of δ13C of individual n-alkanes against carbon number. δ13C ranges of modern marine organic matter (Druffel et al., 1992

Druffel, E.R.M., Williams, P.M., Bauer, J.E., Ertel, J.R. (1992) Cycling of dissolved and particulate organic matter in the open ocean. Journal of Geophysical Research 97, 15639–15659.

; Sara et al., 2007

Sara, G., De Pirro, M., Romano, C., Rumolo, P., Sprovieri, M., Mazzola, A. (2007) Sources of organic matter for intertidal consumers on Ascophyllum-shores (SW Iceland): a multi-stable isotope approach. Helgoland Marine Research 61, 297–302.

), terrestrial C3 vegetation (Kohn, 2010

Kohn, M.J. (2010) Carbon isotope compositions of terrestrial C3 plants as indicators of (paleo)ecology and (paleo)climate. Proceedings of the National Academy of Sciences of the USA 107, 19691–19695.

) and Archean organic matter (Hayes and Waldbauer, 2006

Hayes, J.M., Waldbauer, J.R. (2006) The carbon cycle and associated redox processes through time. Philosophical Transactions of the Royal Society B 361, 931–950.

) are shown for comparison. (a) Emissions that are characterised by invariant δ13C-C2+. (b) Compilation of all n-alkane data analysed in this study. (c) Comparison between n-alkane data from this study (area in grey) and data available from abiotic sites (Supplementary Information): hydrothermal sites (blue); ophiolite gases (black); old craton gases (red) and inclusions in igneous rocks (green).
Back to article | Download in Powerpoint


Figure 2 Plot of δ2H-CH4 vs. δ13C-CH4. Samples with an obvious microbial origin (δ13C-CH4 < –60 ‰, Fig. 1b) are not considered. (a) Data classified after the origin of external water feeding the hydrothermal system (Table S-1). Blue and green squares are representative of the carbon and hydrogen isotopic compositions of marine organic matter and C3 plants, respectively (Schoell, 1984

Schoell, M. (1984) Wasserstoff- und Kohlenstoffisotope in organischen Substanzen, Erdölen und Erdgasen. Geologisches Jahrbuch D67, 1–161.

). The carbon and hydrogen isotopic compositions of instantaneously generated fractions of methane deriving from open system cracking of marine and terrestrial (C3 plants) organic matter were modelled as a function of the fraction of precursor sites remaining inside the cracked organic matter (Supplementary Information). The cracking trend for methane deriving from marine organic matter (blue line) matches the variation of δ13C-CH4 and δ2H-CH4 observed for seawater-fed hydrothermal systems (blue data points). The cracking trend for methane from terrestrial organic matter (green line) corresponds to the slope described by most low δ13C-CH4 samples from meteoric water-fed hydrothermal systems (green data points), but – on average – occurs shifted relative to the latter to higher δ13C and δ2H. This implies that methane precursor sites in decomposing terrestrial organic matter either occur depleted in 13C and 2H with respect to the average C3 plant isotopic composition or that the corresponding carbon and hydrogen isotope fractionations (αC, αH) are larger than those obtained from xylite (Berner et al., 1995

Berner, U., Faber, E., Scheeder, G., Panten, D. (1995) Primary cracking of algal and landplant kerogens: kinetic models of isotope variations in methane, ethane and propane. Chemical Geology 126, 233–245.

), with αHC remaining unchanged. Both possibilities are consistent with carbon isotope constraints on pyrolysis of coal (Cramer et al., 1998

Cramer, B., Krooss, B.M., Littke, R. (1998) Modelling isotope fractionation during primary cracking of natural gas: a reaction kinetic approach. Chemical Geology 149, 235–250.

). (b) Data classified after the style of degassing (wells vs. fumaroles). (c) Comparison between methane data from this study and data available from other abiotic sites (Supplementary Information): labelling as in Figure 1c, extended by (hyper)alkaline spring data (open symbols). Field characteristic for methane from microbial (c) and confined sedimentary systems (b, c) redrawn after Schoell (1988)

Schoell, M. (1988) Multiple origins of methane in the Earth. Chemical Geology 71, 1–10.

.
Back to article | Download in Powerpoint