Dual stable isotopes of CH<sub>4</sub> from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO<sub>2</sub> [electronic resource].
- Washington, D.C. : United States. Dept. of Energy. Office of Science, 2017. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Physical Description:
- pages 187-192 : digital, PDF file
- Additional Creators:
- Pacific Northwest National Laboratory (U.S.), United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
- Volcanism and post-magmatism contribute significant annual methane (CH<sub>4</sub>) fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit CH<sub>4</sub> (as well as carbon dioxide (CO<sub>2</sub>) and other gases), but the ultimate sources of this CH<sub>4</sub> flux have not been elucidated. In this paper, we use dual stable isotope analysis (δ<sup>2</sup>H and δ<sup>13</sup>C) of CH<sub>4</sub> sampled from ten high-temperature geothermal pools in Yellowstone National Park along with other isotopic and gas analyses to evaluate potential sources of methane. The average δ<sup>13</sup>C and δ<sup>2</sup>H values of CH<sub>4</sub> emitted from hot springs ( 26.7 (± 2.4) and - 236.9 (± 12.0) ‰, respectively) are inconsistent with microbial methanogenesis but do not allow distinction between thermogenic and abiotic sources. Correlation between δ<sup>13</sup>C<sub>CH4</sub> and δ<sup>13</sup>C of dissolved inorganic C (DIC) is consistent with DIC as the parent C source for the observed CH<sub>4</sub>, or with equilibration of CH<sub>4</sub> and DIC. Methane formation temperatures estimated by isotopic geothermometry based on δ<sup>13</sup>C<sub>CH4</sub> and δ<sup>13</sup>C<sub>CO2</sub> ranged from ~ 250–350 °C, which is just below previous temperature estimates for the hydrothermal reservoir. Further, the δ<sup>2</sup>H<sub>H2O</sub> of the thermal springs and the measured δ<sup>2</sup>H<sub>CH4</sub> values are consistent with equilibration between the source water and the CH<sub>4</sub> at the formation temperatures. Though the ultimate origin of the CH<sub>4</sub> could be attributed to either abiotic of themorgenic processes with subsequent isotopic equilibration, the C<sub>1</sub>/C<sub>2+</sub> composition of the gases is more consistent with abiotic origins for most of the samples. Finally, our data support the hypothesis that subsurface rock-water interactions are responsible for at least a significant fraction of the CH<sub>4</sub> flux from the Yellowstone National Park volcanic system.
- Published through SciTech Connect., 05/16/2017., "pnnl-sa--121866", ": S0377027316304164", Journal of Volcanology and Geothermal Research 341 ISSN 0377-0273 AM, and James J. Moran; Laura M. Whitmore; Zackary J. Jay; Ryan deM. Jennings; Jacob P. Beam; Helen W. Kreuzer; William P. Inskeep.
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