海马冷泉区沉积物的地球化学特征:对于甲烷渗漏和沉积物来源的指示  

Geochemical characteristics of sediments in the Haima Cold Seep area:indication for methane seepage and sediment source

作　　者：龙恒叉 席世川 杨慧良 赵俐红 李金洋 栾振东 LONG Hengcha;XI Shichuan;YANG Huiliang;ZHAO Lihong;LI Jinyang;LUAN Zhendong(College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Qingdao Institute of Marine Geology,CGS,Qingdao 266237,China;College of Marine Geosciences,Ocean University of China,Qingdao 266100,China)

机构地区：[1]山东科技大学地球科学与工程学院,青岛266590 [2]中国科学院海洋研究所海洋地质与环境重点实验室,青岛266071 [3]中国地质调查局青岛海洋地质研究所,青岛266237 [4]中国海洋大学海洋地球科学学院,青岛266100

出　　处：《海洋地质与第四纪地质》2024年第6期105-120,共16页Marine Geology & Quaternary Geology

基　　金：崂山实验室科技创新项目“深海探测关键技术及原位理化和动力过程研究”(LSKJ202203101);国家自然科学基金委创新研究群体项目“深海界面过程和化能生态系统”(42221005)。

摘　　要：海底甲烷渗漏会对海洋沉积环境产生重大影响,使得甲烷渗漏区沉积物与正常海域沉积物的矿物学、地球化学等方面产生明显差异,因此冷泉沉积物是记录海底甲烷渗漏事件的重要载体。本文基于“海马”冷泉区ZZY7站位长400 cm的岩芯沉积物研究,对沉积物矿物组成、主量元素、微量及稀土元素地球化学特征进行分析,并结合Bayon模型等,结果表明,该站位沉积物矿物种类较多且成因多样:陆源沉积物约占75%,主要矿物成分为石英、长石、黏土等;生物及自生矿物沉积物约占25%,主要是文石、方解石、高镁方解石等。通过建立以∑REE、LREE/HREE、δCe、CaO、Mo_(EF)、U_(EF)、碳酸盐矿物百分含量为甲烷渗漏识别的指标体系,识别出4个硫酸盐-甲烷过渡带(SMTZ),并初步推断该站位可能出现4次甲烷渗漏事件(MRE):210~300(MRE1)、170~190(MRE2)、80(MRE3)、10~50 cmbsf(MRE4)。结合研究区沉积物风化指数和甲烷渗漏历史,发现新生代早期地层受钾元素交代造成钾含量高,而研究站沉积物未受成岩作用影响。这一发现对运用“海马”冷泉区沉积物风化指数研究甲烷渗漏历史和渗漏成因有一定的指导意义。Seabed methane seepage can have a significant impact on the marine sedimentary environment,causing differences in mineralogy,geochemistry,and other aspects between sediments in methane seepage areas and those in normal sea areas.Therefore,cold seep sediments are important carriers for recording methane seepage events on the seabed.A 400-cm sediment core was analyzed that located at Station ZZY7 in the newly discovered"Haima"Cold Seep area in the Qiongdongnan Basin,South China Sea.The mineral compositions and geochemical characteristics of major elements,trace and rare earth elements of the core sediments were studied with which the Bayon model was combined.Result show that terrigenous sediments were accounted for 75% of the total sediments,consisting of mainly quartz,feldspar,clay minerals etc;and biological and authigenic mineral deposits took 25%,and composed of mainly aragonite,calcite,and high magnesium calcite.The sediment minerals at the site are numerous and have diverse origins.An indication system was established using indices ofΣREE,LREE/HREE,δCe,CaO,Mo_(EF),U_(EF),and carbonate mineral percentages,with which methane seepage could be detected.Four sulfate methane transition zones(SMTZ)were recognized,from which four methane seepage events(MRE)in the cold seep area at 210~300 cmbsf(MRE1),170~190 cmbsf(MRE2),80 cmbsf(MRE3),and 10~50 cmbsf(MRE4)were inferred.Combining the sediment weathering index and methane seepage history in the study area,it was found that the potassium content of the early Cenozoic strata was high due to potassium metasomatism,while the sediments at the station were not affected by diagenesis.This discovery has certain guiding significance for using the sediment-weathering index of the Haima cold seepage area to study the history and causes of methane seepage.

关 键 词：甲烷渗漏 稀土元素 沉积环境 氧化还原敏感性元素(RSE) 海马冷泉区 

分 类 号：P736.4[天文地球—海洋地质]