Z22-3

We analyzed a core with a length of 14.02 m sampled from the northern South China Sea, via multiple methods such as chromium reducible sulfur (CRS) content, δ34S values, Sr/Ca and Mg/Ca, and (Mo/U)EF values, to determine the position of SMTZs. Elevated CRS levels and the increased Mg/Ca ratios indicate the enhancement of SD-AOM, suggesting that the position of SMTZ is located at the depths from 181 to 481 cm below seafloor (cmbsf) and below 1101 cmbsf. Additionally, we apply the four-component endmember models of Sr/Ca-Mg/Ca and (Mo/U) EF, which exhibit similarities to other gas hydrate-bearing sites. Moreover, by using LA-ICP-MS to analyze in-situ trace metals of pyrite at depths influenced by SD-AOM and OSR, we observed both enrichment and depletion of trace metals in pyrite compared to sediment.