Geochemical characteristics of cold-seep carbonates in Shenhu area,South China Sea  

作　　者：Chongmin CHEN Lifeng ZHONG Zhifeng WAN Chiyu CHENG Wei ZHOU Xing XU 

机构地区：[1]School of Marine Sciences,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering,Sun Yat-sen University,Zhuhai 519000,China [2]Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519000,China [3]MLR Key Laboratory of Marine Mineral Resources,Guangzhou Marine Geological Survey,Ministry of Natural Resources,Guangzhou 510075,China

出　　处：《Journal of Oceanology and Limnology》2022年第3期969-985,共17页海洋湖沼学报（英文）

基　　金：Supported by the Guangdong Province Marine Economic Development(Six Major Marine Industries)Special Fund Project(No.[2021]No.58);the National Key R&D Program of China(No.2018YFC0310000);the National Natural Science Foundation of China(Nos.41776056,42076054)。

摘　　要：Cold seeps spread worldwide along the continental margins,which are closely related to the exploration of gas hydrates.Cold-seep carbonates have been reported to record the nature of seepage,including fluid source,sedimentary environment,and variation of seepage activity.We investigated the morphology,mineralogy,element compositions,and carbon and oxygen isotopes of 15 cold-seep carbonates collected from the Shenhu area,and compared them with 2 carbonates from the Haima cold seep,the South China Sea(SCS),to promote our knowledge of cold-seep system in SCS.Most of the Shenhu carbonates exhibit crust morphology,and some are in the form of chimneys and blocks.Their absolute(20%–65%)and relative carbonate mineral contents(mainly aragonite and calcite,with minor samples containing dolomite)vary significantly,indicating the multi-stage methane leakage in our study area.Some samples show a slight negative Ce anomaly,suggesting either the mixing of seawater or variation of the redox condition during the precipitation;the cooccurrence of strongly enriched U and Mo demonstrates anoxic condition during precipitation.The mixed genetic methane source was interpreted by δ^(13)C of the Shenhu carbonates to range from-22.34‰to-59.30‰Vienna PeeDee Belemnite(VPDB),and the slight ^(18)O-enrichment imprinted on the carbonates suggests the possible influence from hydrate dissociation.The Haima carbonates,with biogenic methane as the main gas source,were presumably formed in a stronger fluid flux by compared with our Shenhu samples.

关 键 词：cold-seep carbonates geochemistry sedimentary environment fluid source Haima cold seep Shenhu area South China Sea 

分 类 号：P618.13[天文地球—矿床学]