Fluid systems including Moab Khotsong brines (95 (red) and 101 (green) levels), other fracture fluids previously sampled from the Witwatersrand Basin (DreifonteinDR548, MponengMP104, KloofKL739) 2 , and fluids from the Canadian Shield (Copper CliffCCS4546) 2 including fluids from Kidd Creek Mine (KC7792) where residence times of over 1 Ga were identified (Sherwood Lollar et al. 1 ). Error bars represent 0.5 and 5 relative to Vienna Pee Dee Belemnite (V-PDB) and Vienna Standard Mean Ocean Water (V-SMOW) for 13C and 2H, respectively. Specific isotopic values and gas compositional data for C 1-4 hydrocarbons are included in Supplementary Material Table S1.
