Graphite mineralization in Paleoproterozoic khondalites of the North China Craton: A carbon isotope study

Highlights
- High precision carbon isotope study of graphites from the North China Craton.
- Stratabound graphite ores show δ13C values of ca. −25.5‰ corresponding to biogenic origin.
- Graphite in veins and melt pockets show 13C enrichment with heaviest δ13C up to −15.8‰.
- Evidence for microbial life flourishing in the Paleoproterozoic oceans.
- Implications for fluid mixing with CO2 from sub-lithospheric sources.