Metal-driven anaerobic oxidation of methane and the Sturtian deglaciation.

Hu, Jun; Li, Sanzhong; Wang, Shui-Jiong; Peckmann, Jörn; Guan, Hongxiang; Jiang, Shao-Yong; Chen, Wei; Cui, Huan et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The Sturtian and Marinoan glaciations shaped Neoproterozoic palaeoenvironmental evolution. While methane emission likely intensified the Marinoan greenhouse effect, its role during the Sturtian glaciation-coinciding with widespread iron formations (IFs)-remains poorly understood. Here, we analysed bio-essential metals (Ni, Co, Zn), rare earth elements and yttrium (REY), Fe (δ<sup>56</sup>Fe) and Ni (δ<sup>60</sup>Ni) isotopes in hematite and magnetite, alongside bulk-rock and in-situ C isotopes of Mn-rich carbonates from five well-preserved Sturtian-aged IFs in South China. Our findings provide geochemical evidence for a methane-related biogeochemical pathway driving Fe-bearing mineral transformation via methanogenesis and metal-driven anaerobic methane oxidation (AOM), mediated by methanogens and anaerobic methane-oxidizing archaea (ANME) in ferruginous settings. Additionally, the Sturtian deglaciation facilitated atmospheric-oceanic O<sub>2</sub> exchange, increased nutrient influx from weathering, and methane release under slow AOM oxidation kinetics, potentially aiding ice sheet melting or prolonging glacial waning.