浅议四川盆地五峰组—龙马溪组黑色页岩沉积模式与有机质富集规律  

Shale Sedimentary Patterns and Organic Matter Enrichment Patterns of the Wufeng Formation-Longmaxi Formation in the Sichuan Basin

作　　者：毛小平[1] 陈修蓉 李振 李书现 李岁岁 朱启轩 MAO XiaoPing;CHEN XiuRong;LI Zhen;LI ShuXian;LI SuiSui;ZHU QiXuan(China University of Geosciences(Beijing),Beijing 100083,China;Tsinghua University,Beijing 100084,China)

机构地区：[1]中国地质大学(北京),北京100083 [2]清华大学,北京100084

出　　处：《沉积学报》2025年第2期701-733,共33页Acta Sedimentologica Sinica

基　　金：黔科合战略找矿([2022]ZD003)。

摘　　要：【目的】为深入剖析四川盆地五峰组—龙马溪组页岩中有机质富集的沉积环境,【方法】通过类比煤的成矿模式,结合不同水体初级生产力及固碳速率的空间分布,以及沉积相、古地貌、化石发育、盐度等特征,研究了五峰组—龙马溪组页岩与其有机质在空间、时间上的分布特征。【结果】越浅越封闭的水体初级生产力及固碳速率越高;页岩油气与煤层具有相同的成矿模式——马尾模式,距陆地越近有机质越富集,且与煤、蒸发盐岩等共生;水体中碳源、氮源以陆源为主;开阔的陆棚或海湾环境初级生产力低、水动力强,不利于有机质富集;海侵或高水体沉积期不利于有机质富集;四川盆地五峰组—龙马溪组页岩的Sr/Ba值反映为低盐度潟湖环境,离古陆越近有机质丰度越高,而临湘组灰岩和观音桥段介壳灰岩分别为海侵(间冰期)造成的正常盐度开阔海域、中盐度半封闭海湾沉积。【结论】五峰组—龙马溪组富有机质页岩发育于海退环境,为受古陆、水下低隆限制的潟湖、较封闭海湾等浅水海陆过渡相环境;最后建立了水体深度、封闭性二维表来精细刻画有机质的富集规律;提出海相页岩中有机质富集的三大主控因素:浅、封、陆,即浅水水体(<40 m)、靠近陆地和丰富的陆源有机质供给、水体封闭性好。[Objective]The depositional environmental conditions required for the enrichment of organic matter in black shale are not only related to shale oil and gas exploration,but also to other sedimentary minerals and geosciences.For example,bauxite,phosphate rock,manganese ore,and barite ore often coexist with black shale,and the development of black shale is an important environmental or ore prospecting symbol.It is also used as an important reference for paleoclimate,and even the most important evidence of ocean anoxic events is the development of black shale;the current carbon neutralization and carbon sequestration are also required to study carbon burial.Therefore,it is imporatnt to study the development of black shale and the enrichment mechanism of the contained organic matter.It is believed that organic-rich shale develops in deep-water environments,because the deeper the water body,the stronger the reducing environment,making it conducive to the preservation of organic matter.For example,deepwater continental shelves and deep-to-semi-deep lakes can develop high-quality source rocks.However,a large number of exploration practices have proven that these views may have problems and are contrary to modern ecology.[Methods]For this reason,this study took the Wufeng Formation-Longmaxi Formation shale in the Sichuan Basin as an example and fully combined the spatial distribution of primary productivity and the carbon fixation rate of different water bodies.Sedimentary facies and paleogeography,fossil development,salinity and other characteristics,and the distribution characteristics of shale and its organic matter in space and time were studied.[Results]The study found that the development of organic-rich shale requires three characteristics:shallow,continental,and sealed.(1)"Shallow"refers to the shallow water environment.The shallower the water body is,the higher the primary productivity and carbon fixation rate;shale is symbiotic with sapropelite,humic coal,evaporite rock,and other shallow water environments;it ha

关 键 词：页岩气 海相页岩 生态学 深水陆棚 笔石 

分 类 号：P618.13[天文地球—矿床学]