南海海马冷泉区沉积物孔隙水地球化学特征对冷泉活动的指示  

Geochemical characteristics of sediment pore water in Haima area of the South China Sea:An indication of cold seeps

作　　者：孙国静 管红香 张志顺 赵彦彦 冯俊熙 杨俊 张广璐 张雅茹 魏浩天 刘盛 SUN Guojing;GUAN Hongxiang;ZHANG Zhishun;ZHAO Yanyan;FENG Junxi;YANG Jun;ZHANG Guanglu;ZHANG Yaru;WEI Haotian;LIU Sheng(Frontier Science Center for Deep Ocean Multispheres and Earth System,Key Laboratory of Submarine Geosciences and Prospecting Techniques,MOE,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Laoshan Laboratory,Qingdao 266237,China;MLR Key Laboratory of Marine Mineral Resources,Guangzhou Marine Geological Survey,Ministry of Land and Resources,Guangzhou 511458,China)

机构地区：[1]中国海洋大学海洋地球科学学院深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,青岛266100 [2]崂山实验室海洋矿产资源评价与探测技术功能实验室,青岛266237 [3]中国地质调查局广州海洋地质调查局,自然资源部海底矿产资源重点实验室,广州511458

出　　处：《海洋地质与第四纪地质》2024年第1期1-14,共14页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目“冷泉系统甲烷消耗过程的氢利用及其生物地球化学记录”(42276053);泰山学者青年专家项目(tsqn202211069);中央高校基本科研业务费专项(202172002,202172003)。

摘　　要：海马冷泉位于南海琼东南海域,是南海迄今发现的两个活动冷泉之一。我们对海马冷泉Rov2和PC3站位两个活塞重力柱沉积物孔隙水的阴阳离子、溶解无机碳(DIC)及其碳同位素组成和Sr、Ba含量等进行了分析。结果表明,两个站位孔隙水DIC含量(Rov2和PC3最大DIC含量分别为27.4、8.5 mM)和δ^(13)CDIC(Rov2和PC3站位最低值分别为-54.63‰和-48.93‰)具有明显的镜像关系。结合孔隙水硫酸盐浓度的变化特征,Rov2和PC3站位的硫酸盐-甲烷界面(SMI)分别位于约485和410 cm。通过模拟估算,Rov2和PC3站位向上甲烷通量分别为67.4和97.2 mol·m^(-2)·ka^(-1),较浅的SMI深度与相对较高的甲烷通量相一致。SMI附近极低的孔隙水δ^(13)CDIC值指示了AOM作用的发生及其对DIC的贡献。在Rov2站位,自生碳酸盐矿物以高镁方解石为主,阳离子Ca^(2+)、Mg^(2+)和Sr^(2+)含量随深度增加并表现出与SO_(4)^(2−)阴离子含量相似的变化特征。在SMI附近,随着SO_(4)^(2−)的消耗、有机质的矿化将大量的Ba^(2+)和PO_(4)^(3-)释放进入孔隙水。因此,冷泉孔隙水地球化学特征的变化能帮助我们有效识别渗漏活动过程,对AOM作用下物质的迁移与转化具有重要的指示意义。The Haima cold seeps are located in the southeastern part of Qiongdongnan Basin,which is one of the two active cold seeps found in the South China Sea.We analyzed the contents of anions and cations,dissolved inorganic carbon(DIC)and its carbon isotopic composition,and Sr and Ba contents of sediment pore water in two piston gravity columns at the Rov2 and PC3 cores in Haima Cold Seeps.Results show that the DIC contents andδ^(13)CDIC values of pore water in the two cores had a significant"mirror"relationship.With the increase of depth,the DIC contents of the two cores gradually increased(Maximum DIC content of Rov2 and PC3:27.4 and 8.5 mM,respectively).In contrast,theδ^(13)CDIC values had a negative excursion(Minimum values for the two cores:−54.63‰and−48.93‰,respectively).Combined with the sulfate depth profile characteristics of pore water,the sulfate-methane interface(SMI)in Rov2 and PC3 cores was located at~485 and~410 cm,respectively.The upward methane fluxes in Rov2 and PC3 cores were estimated to be 67.4 and 97.2 mol m^(−2)ka^(-1),respectively.The very lowδ^(13)CDIC values in pore water near SMI are indicative of the occurrence of AOM(anaerobic oxidation of methane)interaction and its contribution to DIC.In Rov2 core,authigenic carbonate minerals are dominated by high-Mg calcite,and the Ca^(2+),Mg^(2+)and Sr^(2+)showed similar trends to those of SO_(4)^(2−).Near the SMI,with the depletion of SO_(4)^(2−),the mineralization of organic matter released large amounts of Ba^(2+)and PO_(4)^(3-)into the pore water.The geochemical characteristics of pore water could help us effectively identify the early diagenesis in seepage activity area,and are indicative of migration and transformation of materials under the influence of AOM.

关 键 词：甲烷厌氧氧化 冷泉渗漏 孔隙水 中国南海 

分 类 号：P736.4[天文地球—海洋地质]