AUTHOR=Chen Chongmin , Wu Xuewan , Wan Zhifeng , Shang Jiujing , Huang Wei , Zhang Wei , Liang Jinqiang , Xiao Zebang , Zhou Wei , Zhong Lifeng 

TITLE=Geochemical characteristics of sediment and pore water affected by cold seeps in southern South China Sea

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1167578

DOI=10.3389/fmars.2023.1167578

ISSN=2296-7745

ABSTRACT=Cold seep, characterized by active material circulation and methane seepage, is of great importance to reconstruct the paleo-marine environment and trace the origin of life and the occurrence of minerals. Southern South China Sea (SCS) with ample oil and gas resources is an ideal platform for cold seep study, but information and researches on cold seeps here are rather deficient. We studied the geochemical characteristics of sediment cores and pore water combined with seismic profile information in the Beikang Basin, aiming to further understand the nature of cold seeps in this area. The extremely low δ13CDIC of pore water at each core indicates a strong anaerobic oxidation of methane (AOM) function and a major source of biogenic methane. The sulfate methane transition zone can be characterized by profiles of SO42-, the high content of inorganic carbon (DIC) and the corresponding minimum δ13CDIC in pore water. The kink-type depth profiles of Sr, Ba and Ni enrichment factors and Sr/Mg in the sediments of BH-CL37 indicate the depth of the paleo SMTZ, denoting a past enhanced methane flux or the modern weakened cold seep activity. The features of Mo, U and REE constrain the reducing sedimentary environment. Combined with the seismic profiles, we conclude that fluid fluxes and tectonic settings greatly influence the sedimentary environment and geochemistry, leading to the manifest regional differences in the properties and activities of cold seeps. This study of cold seep in southern SCS proves the variation of cold seep in time and space, stressing the necessity of further region-specific analysis towards different cold seeps; and the complex conditions of SCS do function well in offering multiple types of cold seeps.