Geochemical data for CL6

Recently, the redox sensitive behaviour and associated isotope fractionations of molybdenum in various marine geological environments has received much attention, but the characteristics of δ98Mo in cold-seep system are still not fully understood. Therefore, we conducted a series of geochemical analyses including Mo isotopes on the sediment samples (CL6) obtained from the “Haima” cold-seep deposit area in the South China Sea. The results show that the 373–403cm in CL6 is obviously affected by methane seepage with a light δ98Mo signature. Comprehensive analysis shows that sulfidic dissolution of Fe and Mn (oxy)hydroxides is the fundamental reason for this phenomenon. This not only deepens our understanding of Mo geochemical cycles, but also reminds us to be more rigorous when using δ98Mo for paleo-redox environment reconstruction.