Thermochemical oxidation of methane induced by high-valence metal oxides in a sedimentary basin.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30510284.
- Also identified by DOI 10.1038/s41467-018-07267-x and PMC identifier 6277441.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Thermochemical oxidation of methane (TOM) by high-valence metal oxides in geological systems and its potential role as a methane sink remain poorly understood. Here we present evidence of TOM induced by high-valence metal oxides in the Junggar Basin, located in northwestern China. During diagenesis, methane from deeper source strata is abiotically oxidized by high-valence Mn(Fe) oxides at 90 to 135 °C, releasing <sup>13</sup>C-depleted CO<sub>2</sub>, soluble Mn<sup>2+</sup> and Fe<sup>2+</sup>. Mn generally plays the dominant role compared to Fe, due to its lower Gibbs free energy increment during oxidation. Both CO<sub>2</sub> and metal ions are then incorporated into authigenic calcites, which are characterized by extremely negative δ<sup>13</sup>C values (-70 to -22.5‰) and high Mn content (average MnO = 5 wt.%). We estimate that as much as 1224 Tg of methane could be oxidized in the study area. TOM is unfavorable for gas accumulation but may act as a major methane sink in the deep crustal carbon cycle.