Mesoarchean Microbial Cd, Ba, and Ni Cycling: Evidence for Photosynthesis in Pongola Group Stromatolites through Novel Stable Isotopes and High-Resolution Trace Element Maps

作者：Simon V. Hohl, Yiwen Lv, Yibo Lin, Yinggang Zhang, Yuxiang Jiang, Guang‐Yi Wei, Sebastian Viehmann · 发表于：Astrobiology · 年份：2024 · DOI：10.1089/ast.2024.0041 · 被引用次数：9 · 研究领域：Geochemistry and Elemental Analysis、Paleontology and Stratigraphy of Fossils、Geological and Geochemical Analysis

Nontraditional stable isotopes of bioactive metals emerged as novel proxies for reconstructing the biogeochemical cycling of metals, which serve as cofactors in major metabolic pathways. The fractionation of metal isotopes between ambient fluid and microorganisms is ultimately recorded in authigenic minerals, such as carbonates, which makes them potentially more reliable than standard biomarkers in organic matter. Stromatolitic carbonates are geochemical archives that allow for the study of the long-term interplay of the biosphere, atmosphere, and hydrosphere through deep time, with the unique potential to investigate early life environments and the evolution of the metallome. The present study uses stromatolites from the ∼2.95-billion-year-old Pongola Supergroup (S. Africa) as a field laboratory for combined in situ trace metal mapping and layer-specific, novel stable metal isotope compositions to infer early Earth microbial metal cycling via phototrophic and chemo-litho-autotrophic metabolisms. Quantitative in situ trace element maps reveal intrinsic biosedimentary enrichments of nickel (Ni), cadmium (Cd), phosphorus (P), iron (Fe), and manganese (Mn) in stromatolitic laminae. In contrast, barium (Ba) shows a more homogeneous distribution. Authigenic carbonates from pristine stromatolite laminae show distinct δ 138 Ba and δ 112 Cd fractionation above detrital background and bulk silicate Earth values, but opposing correlation with trace metal concentrations. Authigenic δ 60...