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Article Dans Une Revue Nature Communications Année : 2019

Microbially induced potassium enrichment in Paleoproterozoic shales and implications for reverse weathering on early Earth

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Illitisation requires potassium incorporation into a smectite precursor, a process akin to reverse weathering. However, it remains unclear whether microbes facilitate K+ uptake to the sediments and whether illitisation was important in the geological past. The 2.1 billion-year-old Francevillian Series of Gabon has been shown to host mat-related structures (MRS) and, in this regard, these rocks offer a unique opportunity to test whether ancient microbes induced illitisation. Here, we show high K content confined to illite particles that are abundant in the facies bearing MRS, but not in the host sandstone and black shale. This observation suggests that microbial biofilms trapped K+ from the seawater and released it into the pore-waters during respiration, resulting in illitisation. The K-rich illite developed exclusively in the fossilized MRS thus provides a new biosignature for metasediments derived from K-feldspar-depleted rocks that were abundant crustal components on ancient Earth.
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hal-02157763 , version 1 (17-06-2019)

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Jérémie Aubineau, Abderrazak El Abani, Andrey Bekker, Andréa Somogyi, Olabode Bankole, et al.. Microbially induced potassium enrichment in Paleoproterozoic shales and implications for reverse weathering on early Earth. Nature Communications, 2019, 10, pp.2370. ⟨10.1038/s41467-019-10620-3⟩. ⟨hal-02157763⟩

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