Thermochemical oxidation of methane induced by high-valence metal oxides in a sedimentary basin.

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 ¹³C-depleted CO₂, soluble Mn²⁺ and Fe²⁺. Mn generally plays the dominant role compared to Fe, due to its lower Gibbs free energy increment during oxidation. Both CO₂ and metal ions are then incorporated into authigenic calcites, which are characterized by extremely negative ?¹³C 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.

SUBMITTER: Hu WX 

PROVIDER: S-EPMC6277441 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature