Data produced from NERC Grant NE/M001156/1 - Fe speciation data (FeHR/FeT, and FePy/FeHR), collected following methods outlined in Izon et al., 2017, Proceedings of the National Academy of Sciences (PNAS); % Carbonate, determined gravimetrically; d34SV-CDT for sedimentary pyrite, analysed by Iso-Analytical Laboratories, Cheshire, using standard EA-IRMS techniques; d15N of bulk rock, analysed by nano-EA-IRMS, following methods described in Polissar et al., 2009, Analytical Chemistry; d15N of kerogen extracted following the methods described in Zerkle et al., 2017, Nature, analysed by nano-EA-IRMS; d13C of organic carbon, measured on decarbonated rock powders by standard EA-IRMS techniques; %TN and TON % determined by standard EA-IRMS of bulk rock and extracted kerogen, respectively. Drill core samples were taken through the 2.7Ga old Manjeri Formation of the Belingwe Greenstone belt, Zimbabwe, which overlies more ancient gneissic basement with very well-exposed unconformity (Bickle et al. 1975). The Manjeri Formation, typically 50-150m thick, exhibits a deepening succession of facies (Grassineau et al., 2002, Hunter et al., 1998). It is directly overlain by komatiitic basalts and komatiites of the Reliance Fm., dated at 2692±9 Ma (Pb-Pb whole rock; Chauvel et al., 1993). The metamorphic grade of the Manjeri succession is variable, but generally remarkably low (Abell et al. 1981). Three drill cores were taken in the Manjeri Formation. The NERCMAR drill core has been described in detail by Grassineau et al., 2002. Drill cores A and B were collected some km to the north, in the upper Manjeri Formation.