Characteristics of authigenic pyrites in shallow core sediments in the Shenhu area of the northern South China Sea: Implications for a possible mud volcano environment

作     者：XIE Lei WANG JiaSheng WU NengYou WU DaiDai WANG Zhou ZHU XiaoWei HU Jun CHEN HongRen LIN Qi 

作者机构：State Key Laboratory of Biogeology and Environmental Geology (China University of Geosciences) Faculty of Earth Science China University of Geosciences Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou Center for Gas Hydrate Research Chinese Academy of Sciences Guangzhou Institute of Geochemistry Chinese Academy of Sciences 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2013年第56卷第3期

页      面：541-548页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 

基　　金：supported by National Basic Research Program of China (Grant Nos.2009CB21950605 and 2011CB808805) National Natural Science Foundation of China (Grant Nos. 41172102 and 41003010) National Natural Science Foundation of China-Guandong Co-project (Grant No. U0933004) Special Project (Grant No. GZH201100305-06-03) 

主　　题：pyrite distribution sulfur isotope shallow sediment Shenhu area 

摘      要：Distinct pyrites have been recovered from a shallow sediment core from Site 4B in the Shenhu area of the northern South China Sea. Based on the lithology, texture and structure of sediments, the stable sulfur isotope of pyrite and the total organic carbon (TOC) concentration of the sediments, a distinctive sediment interface is identified at a depth of about 1 m below the seafloor in the core sediments. The pyrites only accumulate in the lower part of the core as rods and foraminifera-infillings, and mainly within three intervals marked by high pyrite concentrations. The amount of pyrite in the sediments shows no remarkable correlation with TOC in the Site 4B core sediments. The stable sulfur isotopes of the pyrite have extremely negative values ranging from 41.69‰ to 49.16‰. They are considered to be the mutual product of sulfate bacterial reduction and sulfur bacterial disproportionation. Our research proposes that Site 4B might be located in or near a possible mud volcano sedimentary environment; a large amount of methane could migrate from deep to shallow sediments in an active mud volcano and thereby play a key role in the intensity of sulfate bacterial reduction and the amount of pyrite formed at Site 4B. Further, the variation in flux of deep methane fluid by intermittent mud volcanic eruptions might result in the deposition of authigenic pyrite intervals.