康滇古陆西侧早志留世古海洋氧化-还原环境及优质烃源岩发育模式--以盐源地区CYD2井为例  

Paleo-marine redox conditions and development model of high-quality source rocks of the Early Silurian on the West side of Kangdian Oldland:a case study of CYD2 well in Yanyuan area

作　　者：程锦翔[1,2] 邓敏 王正和[1,2] 余谦 张海全[1,2] 刘伟 赵安坤[1,2] 杨贵来 CHENG Jinxiang;DENG Min;WANG Zhenghe;YU Qian;ZHANG Haiquan;LIU Wei;ZHAO Ankun;YANG Guilai(Chengdu Center,China Geological Survey,Chengdu 610081,Sichuan,China;Key Laboratory of Sedimentary Basin and Oil and Gas Resources,Ministry of Natural Resources,Chengdu 610081,Sichuan,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]自然资源部沉积盆地与油气资源重点实验室,四川成都610081

出　　处：《地质通报》2022年第10期1813-1828,共16页Geological Bulletin of China

基　　金：中国地质调查局项目《四川盆地下古生界海相页岩气基础地质调查》(编号:DD20160176);《滇东北地区页岩气地质调查》(编号:DD20190080)。

摘　　要：在系统的地质调查和沉积学、地球化学研究的基础上,以康滇古陆西侧盐源盆地南缘CYD2井龙马溪组为研究对象,探讨早志留世古氧化还原环境、古水文条件、热液影响及有机质富集因素,总结优质烃源岩发育模式,为该区优质烃源岩预测提供基础。研究表明:盐源地区优质烃源岩发育于龙马溪组下部(L1~L3),经历了由初期(L1)滞留程度较高的硫化环境到晚期(L5)较开阔氧化环境的演化过程;且在志留纪早期古海洋遭受了强烈的热液活动影响,表现为轻稀土元素显著富集,Ce略有亏损,Eu显著富集。康滇古陆早期构造演化造成了强烈的热液活动和差异隆升,控制盐源地区龙马溪初期古海洋氧化还原特征及海盆局限程度,与海平面持续上升共同控制了盐源地区志留纪龙马溪期古海洋环境及优质烃源岩的形成和分布。Based on the systematic geological survey and sedimentology study of the Longmaxi Formation.in the large area of Yanyuan Basin and the detailed geochemical analysis on the core of CYD2 well drilled in its southern margin,an organic matter enrichment model of the Early Silurian Longmaxi Formation.is proposed.This model gives a good explanation for the mechanism of organic matter accumulation under several influences,and the well understanding of this mechanism will provide a good basis for further high-quality source rock evaluation of shale gas in this area.In this study,the influences including paleo-redox environment,paleo-hydrological conditions,hydrothermal influence,and the factors that affect organic matter enrichment are all discussed.The high-quality source rocks are developed at the bottom(L1~L3)of Longmaxi Formation.in Yanyuan area.It has undergone an evolutionary process from the vulcanization environment with high retention in the early stage(L1)to the open and oxidic environment in the late stage(L5).In the early Silurian,the ancient oceans were strongly influenced by hydrothermal activities evidenced by the obvious LREE enrichment,slight Ce loss and significant Eu enrichment.The early tectonic evolution of the Kangdian Oldland resulted in the intense hydrothermal activities and crustal differential uplifts.It controlled the Paleo-redox condition of seawater and the extend of basin limitation of Yanyuan area during the Early Silurian.The early tectonic evolution of the Kangdian Oldland,together with the continuous rise of sea level,controlled the distribution of ancient marine environment and high-quality source rocks during the Longmaxi period of Silurian in the Yanyuan area.

关 键 词：优质烃源岩 氧化还原环境 志留系龙马溪组 盐源地区 

分 类 号：P534.43[天文地球—古生物学与地层学] P618.13[天文地球—地质学]