珠江口盆地珠江组混积岩中有孔虫的矿化特征与机制  

Mineralization Characteristics and Mechanism of Foraminifera in Mixed Siliciclastic-Carbonate Sediments in Zhujiang Formation of Pearl River Mouth Basin

作　　者：刘娜[1] 吴克强 刘立[1] 于雷[1] 徐思萌 彭晓蕾[1] Liu Na;Wu Keqiang;Liu Li;Yu Lei;Xu Simeng;Peng Xiaolei(College of Earth Sciences,Jilin University,Changchun 130061,China;Research Institute of China National Offshore Oil Corporation Lim ited,Beijing 100028,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中海油研究总院,北京100028

出　　处：《地球科学》2020年第10期3746-3758,共13页Earth Science

基　　金：中海油综合科研项目(No.CCL2015RCPS0150RCN);国家自然科学基金(Nos.41202073,41572082)。

摘　　要：珠江口盆地白云凹陷是我国现今深水油气勘探的重要地区,在其南侧的荔湾X构造的珠江组在3 000~3 281 m以混积岩沉积为主.以荔湾X构造内含有孔虫混积岩为研究对象,通过开展岩石学和同位素地球化学研究,确定了有孔虫宿主岩石类型以及有孔虫矿化的岩相学特征,重点探讨了有孔虫的矿化机制,并最终建立了有孔虫的矿化模式.荔湾X构造珠江组混积岩的生物碎屑以有孔虫碎屑为主,有孔虫壳由刃状、等径状方解石或铁方解石组成.有孔虫的房室可分为未充填、半充填和全充填3种类型.根据有孔虫房室充填的主要自生矿物类型、产状及相互关系,可将有孔虫矿化按其形成的先后分为黄铁矿化、铁方解石化、片钠铝石化和铁白云石化4种类型,其中黄铁矿的形成可能与有孔虫软体组织的生物降解有关,铁方解石可能与有机质热脱羧作用有关,片钠铝石和铁白云石中的"碳"有深部来源的岩浆成因CO2的贡献.The Pearl River Mouth basin is an important area for deep water petroleum exploration in China,within which,the Liwan X structure is mainly composed of mixed siliciclastic-carbonate sediments at the depths between 3000 m and 3281 m.Petrologic and isotopic geochemical characteristics were investigated by polarizing microscope and carbon-oxygen isotopic analysis.The host rock type of foraminifera and the petrographic characteristics of foraminifera mineralization were determined,and the mineralization mechanism of foraminifera was discussed,and finally the mineralization model of foraminifera was established.The bioclast of Zhujiang Formation is mainly composed of foraminiferal clasts,while the foraminiferal shell is composed of blade-,equal diameter calcite or ferrocalcite.There are mainly three filling patterns for the foraminifera’s chamber:unfilled,half-filled and full-filled pattern.According to the types and the occurrences of the main authigenic minerals,the foraminiferal mineralization can be divided into four types,including pyritization,ferrocalcitization,dawsonitization and ankeritization,among which the formation of pyritization may be related to the biodegradation of foraminiferal soft tissue,and the ferrocalcitization may be related to the thermal decarboxylation of organic matter,while the magmatic CO2 provided the carbon sources for the precipitation of dawsonite and ankerite.

关 键 词：矿化机制 混积岩 有孔虫 片钠铝石 幔源CO2 珠江口盆地 沉积 油气 

分 类 号：P588.2[天文地球—岩石学]