珠江口盆地陆丰凹陷文昌组沉积地球化学特征及古环境意义  

Geochemical Constraints on the Sedimentary Environment of Wenchang Formation in Pearl River Mouth Basin and Its Paleoenvironmental Implications

作　　者：高阳东 林鹤鸣 汪旭东 邱欣卫 阙晓铭 李敏 赵泽颖 陈艳[2] GAO Yangdong;LIN Heming;WANG Xudong;QIU Xinwei;QUE Xiaoming;LI Min;ZHAO Zeying;CHEN Yan(CNOOC China Limited,Shenzhen Branch,Shenzhen,Guangdong 518000,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中海石油(中国)有限公司深圳分公司,广东深圳518000 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《现代地质》2022年第1期118-129,共12页Geoscience

基　　金：中海石油(中国)有限公司深圳分公司“南海东部油田上产2000万吨关键技术研究”项目(CCL2019SZPS0494)。

摘　　要：陆源营养物质输入是湖泊成油母质(细菌和藻类、浮游植物等)生长的主要外部营养源。古气候条件影响了陆源输入,湖盆水体沉积环境控制了有机质保存,因此沉积期古气候古水体条件对湖相烃源岩有机质丰度预测至关重要。针对珠江口盆地陆丰凹陷文昌组烃源岩进行环境地球化学研究,运用CIA、V/Cr、Mn/Al、Sr/Cu、Ti/Al等多种元素地球化学指标,综合恢复了陆丰凹陷文昌组沉积期古风化强度与气候温湿度、湖泊古水深、古氧相、古盐度等环境条件,揭示了古环境对文昌组烃源岩的重要控制作用为:(1)珠江口盆地文昌组时期气候温湿度与化学风化强度呈明显分段,文三段下段与文四段高强度对应高有机质含量。(2)珠江口盆地文昌组时期古水深与古氧相对有机质富集起到重要控制作用,古盐度对有机质影响不大。珠江口盆地陆丰凹陷LF-A井文四段与文三段下部烃源岩形成于化学风化较强、气候温暖湿润、营养物质供应充足、湖盆生产力高、水体较深、含氧量较低的水体环境下,有机质富集。Terrestrial input is the main external nutrient source for the growth of oil parent matter(e.g.bacteria,algae,phytoplankton)in lacustrine environment.Paleoclimate conditions affect terrigenous input,and lacustrine sedimentary environment controls organic matter preservation.Understanding the paleo-lacustrine environment is critical to predict organic matter abundance in source rocks.Here,we present new geochemical data from source rocks of the Wenchang Formation in the Lufeng Sag of Pearl River Mouth Basin.Element geochemical indices,e.g.CIA,V/Cr,Mn/Al,Sr/Cu and Ti/Al,altogether reveal the climate,lake-level,paleo-oxygen and paleo-salinity conditions and show that the paleo-environment played an important role in controlling the source rocks.High level of chemical weathering corresponds to high organic matter in the lower part of E_(2)w_(3) and E_(2)w_(4).Lake-level and paleo-oxygen changes are responsible for the organic matter enrichment of E_(2)w.Meanwhile,the paleo-salinity are less relevant.The organic-rich source rocks of the E_(2)w_(4) and E_(2)w_(3)(lower part)of the LF-A well in the Lufeng Sag were likely formed in a deep and reduced lake with strong chemical weathering,under the conditions of warm-humid climate,sufficient nutrient supply,and high productivity.

关 键 词：珠江口盆地 文昌组 沉积地球化学 古环境 烃源岩 

分 类 号：P736.4[天文地球—海洋地质]