Ancient organic matter in graphite-rich metasediments as a potential carbon source for deep subsurface life

This dataset supports a study investigating the origin of methane in deep subsurface environments within the Palaeoproterozoic bedrock of the Fennoscandian Shield, with a particular focus on black schist formations. Through integrated geochemical analyses and microbiological methods—including methane isotopologue measurements and microcosm experiments—the study provides evidence supporting a predominantly abiotic origin of methane in these settings.
The findings reveal the theoretical suitability of graphitic carbon as a microbial carbon source in deep bedrock, based on thermodynamic calculations, and observational evidence of graphitic carbon conversion to CO₂ by intrinsic deep biosphere microbial communities. Additionally, the study discusses the potential of graphitic black schists as a carbon and energy source in deep crystalline bedrock subsurface environments.
These results offer novel insights into carbon cycling in deep bedrock ecosystems, especially highlighting the role of graphitic carbon as a substrate in deep biosphere ecosystems. The dataset contributes to ongoing discussions about the origin and source of methane in ancient crystalline rock formations and the interplay between biotic and abiotic processes in extreme environments.
This dataset comprises comprehensive environmental and experimental data collected for the study of water chemistry and microbial processes. It includes two primary components:
1) Data from field monitoring and samples of intrinsic groundwater fluids from two study sites, including geospatial and temporal sampling details, water chemistry parameters (major, minor cations and trace elements, anions and other chemical species), total dissolved solids, pH, alkalinity and electrical conductivity, stable isotope measurements (δD-H₂O, δ¹⁸O-H₂O, d-excess, δ¹³C-DOC, δ¹³C-DIC, δ¹³C-CO₂, δ¹³C-CH₄, δ¹³C-C₂H₆, δD-CH₄, ¹⁴C-CH₄), dissolved organic carbon and C1/C2+ gas ratios. In addition, this data contains also the number of viable microbial cells in each groundwater sample and microbial diversity indices (fungal and bacterial communities) of these.
2) Data from microcosm experiment conducted with different carbon sources and inocula in the laboratory. This includes microbial diversity (fungal and bacterial) in microcosms, headspace CO2, CH4, N2O, O and N concentrations in the end of the experiment in microcosms, and d13C isotope values of CO2 and CH4 after the incubation with 13C-labeled graphite as added carbon source.

This dataset supports research in hydrogeochemistry, biogeochemical cycling, and microbial ecology, providing valuable insights into the interactions between chemical parameters and microbial communities in deep crystalline bedrock subsurface environments.