Characteristics and application of multiple sulfur isotopes of authigenic minerals in cold-seep environment

Organoclastic sulfate reduction (OSR) exists extensively within normal marine sediments, whereas, sulfate reduction coupled with anaerobic oxidation of methane (SR-AOM) are dominated process in the cold-seep areas. How to distinguish these two sulfate reduction pathways is of great significance to the study of biogeochemical processes in extreme environments. Here, in order to further understand the characteristics of multiple sulfur isotopes of authigenic minerals associated with SR-AOM in the cold seep and their modeling applications, this study conducts extensive investigations into the research results of multiple sulfur isotopes related to SR-AOM at home and abroad, mainly focusing on the multiple sulfur isotopic characteristics of pyrite and barite of SR-AOM. Based on this, the widely used steady-state box model and 1-D diagenetic reaction-transport model are proposed for pyrite and barite respectively. The pyrite of SR-AOM origin has higher δ³⁴S and Δ³³S values than that of OSR. The δ³⁴S and Δ³³S values of pyrite formed by SR-AOM shows a negative correlation, which is different from that of OSR. The negative Δ³³S-δ´³⁴S correlation of barite significantly different from that of OSR-induced pore water sulfate reveals a positive correlation. The multiple sulfur isotopic characteristics of authigenic minerals related to SR-AOM in the cold seep can effectively trace the evolution of sulfur isotopes and assist to distinguish SR-AOM from OSR. This provides an effective basis for further research on biogeochemical processes in extreme environments and for tracing potential gas hydrate deposits.