Fig. 3: Isotopic compositions of porewater Fe and their relationships with each other and with the dissolved Fe concentrations of the Liangjiangkou core.
A δ'57Fed versus δ'56Fed for all data from the top ~25 cm of the core. Group 1 data (hollow) were from depths below the Mn reduction zone (>6.5 cm) and they fall closely along a high-temperature-limit mass-dependent fractionation (MDF) line defined by a slope of 1.475 (solid line). Group 2 data (filled) were from the top 6.5 cm (≤6.5 cm) of the core and display significant deviations from the MDF line. B ∆'57Fed versus δ'56Fed for all data from the top ~25 cm of the core with the ∆'57Fe being more positive with decreasing δ'56Fe porewater values in the top 6.5 cm (R2 = 0.64). The gray horizontal band (±0.14‰, 2 SD) covers samples with no distinct NMD Fe isotope signature. A linear least-squares regression line through samples of Group 2 intersects with samples of Group 1 at a δ'56Fe of −1.3‰. C δ'56Fed versus Fed diagram. Data of Fe-limited porewaters (≤6.5 cm) fall into one cluster with δ'56Fed lower than those of Fe-rich porewaters (>6.5 cm) in another cluster. D ∆'57Fed versus Fed diagram. Data of Fe-limited porewaters (≤6.5 cm) fall into one cluster with positive ∆'57Fed while those of Fe-rich porewaters (>6.5 cm) with no distinct NMD Fe isotope signatures fall into another cluster. Error bars for δ'56Fe, δ'57Fe, and Δ'57Fe are ±0.10‰, ±0.16‰ and ±0.14‰ (2 SD), respectively.
