湘中及周缘中奥陶统黑色细粒岩系沉积特征及环境  

Sedimentary Characteristics and Environment of the Middle Ordovician Black Fine-Grained Rock Series in Central Hunan and Its Surrounding Areas

作　　者：郭原草[1,2] 郭建华 余烨 黄俨然[2] 蔡灵慧[2] 陈广[3] GUO YuanCao;GUO JianHua;YU Ye;HUANG YanRan;CAI LingHui;CHEN Guang(School of Civil Engineering,Hunan University of Science and Technology,Xiangtan,Hunan 411201,China;School of Earth Sciences and Spatial Information Engineering,Hunan University of Science and Technology,Xiangtan,Hunan 411201,China;School of Geosciences and Info-physics,Central South University,Changsha 410083,China)

机构地区：[1]湖南科技大学土木工程学院,湖南湘潭411201 [2]湖南科技大学地球科学与空间信息工程学院,湖南湘潭411201 [3]中南大学地球科学与信息物理学院,长沙410083

出　　处：《沉积学报》2024年第5期1817-1831,共15页Acta Sedimentologica Sinica

基　　金：国家科技重大专项(2016ZX05026-002);中石化石勘院外部协作项目(GSYKY-B09-33)。

摘　　要：【目的】中奥陶统烟溪组是近年来在湘中地区新查明的一套海相富有机质黑色细粒岩系,具有较好的页岩气勘探潜力,对这套黑色细粒岩系的沉积特征研究亟待加强。【方法】通过野外踏勘、薄片鉴定等开展烟溪组岩性、岩相组合类型识别,结合元素测试判定沉积环境,采用盆地分析技术结合区域构造运动史查明原型盆地性质、形态,确定黑色细粒岩系有利沉积相带、时空展布及沉积模式。【结果】烟溪组岩性以硅质岩和碳质页岩为主,粉砂质页岩、粉砂岩等次之;硅质岩以浅海环境下生物成因为主,碳质页岩形成于安静缺氧的深水滞留环境。在烟溪组内部可识别出四类岩相组合:厚层纯碳质页岩、碳质页岩与硅质岩组合、粉砂质页岩和硅质岩组合和粉—细砂岩夹薄层泥页岩组合;根据岩相组合类型烟溪组在垂向上可分为上、中、下三段,三段在区域上的分布厚度相对稳定,具有较好的对比性,中段厚层碳质页岩是最重要的烃源层系。烟溪组在区内呈东南厚、西北薄之特征,沉积相类型包括深水盆地、深水陆棚、浅水陆棚和浊积扇,各沉积相带在奥陶纪不同时期分布位置有所不同,分区明显,连续变化。【结论】湘中及周缘地区在中奥陶世处于缺氧的滞留水体环境,是一个稳定地块内的坳陷海盆,深水陆棚相和深水盆地相是烟溪组富有机质页岩发育的有利相带。[Objective]The Middle Ordovician Yanxi Formation is a recently identified set of marine organic rich black fine-grained rock series in central Hunan and its surrounding areas,with good shale gas exploration potential.The research on the sedimentary characteristics of this black fine-grained rock series urgently needs to be strengthened.[Methods]The lithology and lithofacies combination types of the Yanxi Formation were identified through field exploration and slice identification,and the sedimentary environment was determined through element testing.Basin analysis technology,combined with regional tectonic movement history,was used to identify the nature and morphology of the prototype basin,determining favorable sedimentary facies zones,spatiotemporal distribution,and sedimentary patterns of the black fine-grained rock series[.Results]The lithology of the Yanxi Formation is primarily siliceous rock and carbonaceous shale,followed by silty shale and siltstone.Siliceous rocks are mainly biogenic in shallow marine environments,and carbonaceous shale is formed in a quiet and anoxic deep water detention environment.Four types of lithofacies combinations can be identified within the Yanxi Formation:thick pure carbon shale,carbon shale and siliceous rock combination,silty shale and siliceous rock combination,and silty fine sandstone with thin layer shale combination.Based on different rock facies combinations,the Yanxi Formation can be vertically divided into three sections:upper,middle,and lower;the distribution thickness of the three sections in the region is relatively stable and has good comparability.The thick layer of carbonaceous shale in the middle section is the most important source rock series.The Yanxi Formation is characterized by a thick southeast and thin northwest distribution in the study area,and the types of sedimentary facies include deep water basins,deep water continental shelves,shallow water continental shelves,and turbidite fans.The distribution positions of each sedimentary facies zone varied

关 键 词：湘中 烟溪组 黑色细粒岩系 沉积特征 沉积环境 原型盆地 

分 类 号：P618.13[天文地球—矿床学]