Research progress on reconstruction method of redox conditions in submarine seafloor cold seeps

Cold seep is one of the seafloor extreme environmental systems, it has important scientific significance in gas hydrate exploration and global climate change for extreme environmental life activities. Reconstruction of redox conditions in cold seep is an important way to study the biogeochemical processes and reveal the characteristics of methane seepage. In recent years, many mineralogical and geochemical indicators have been successfully used in the study of the recovery of redox conditions in cold seep systems. Based on previous studies, the responding mechanisms of different redox indicators were summarized, such as autogenetic mineralogical characteristics, rare earth elements, redox sensitive elements (Mo, U, and Fe), and stable isotopes (δ⁹⁸Mo, δ⁵⁶Fe, and δ³⁴S). The influencing factors and existing issues of each index were discussed from the aspects of test and analysis methods, diagenetic alteration, and non-uniqueness in using a single index. At last, the key research direction in this field in the future was proposed.