黔桂地区泥盆纪富有机质竹节石页岩:一个重要的潜在性页岩气勘探目的层  

Organic-matter-rich tentaculitid shales of the Devonian in the region from the southern Guizhou to central Guangxi of South China:An importantly potential target rock for shale-gas exploration

作　　者：梅冥相[1,2] 岑文攀 Muhammad RIAZ MEI Mingxiang;CEN Wenpan;Muhammad RIAZ(School of Earth Sciences and Natural Resources,China University of Geosciences,Beijing 100083,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China;Guangxi Geological Survey,Nanning,Guangxi 530023,China;Institute of Geology,University of the Punjab,Lahore 54590,Pakistan)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [3]广西地质调查院,广西南宁530023 [4]地质研究所,旁遮普大学,拉舍尔54590,巴基斯坦

出　　处：《地质学报》2025年第4期1332-1352,共21页Acta Geologica Sinica

基　　金：广西重点研发计划项目(编号2021AB30011);广西地矿局重点科研项目(编号GXDK202430)资助的成果。

摘　　要：泥盆纪是地球历史之中碳质页岩的全球性沉积作用一个特别显著的幕。在黔桂地区深水沉积主导的台间盆地相之中,从早泥盆世的埃姆斯期到晚泥盆世的弗拉期,集中发育一套总厚度超过600 m的富有机质竹节石页岩,以下特征表明这些富有机质的竹节石页岩将成为重要的潜在性页岩气勘探目的层:(1)页岩的总有机碳含量(TOC)值多为2%~4%,可以高达5%~6%;(2)从早泥盆世的埃姆斯期至中泥盆世,有机碳多集中富集在三级海平面相对上升期沉积的、而且单层厚度常常超过百米的富有机质竹节石页岩主导的缺氧盆地相沉积之中,相对应的三级海平面下降期则为亏损有机碳的陆棚相沉积;(3)在晚泥盆世弗拉期硅质岩主导的榴江组之中,有机碳多富集在三级海平面下降期的、单层厚度为30~40 m的缺氧盆地相富有机质竹节石页岩之中,所对应的三级海平面上升期则为硅质岩主导的而且亏损有机碳的远洋盆地相沉积。暂时归为缺氧盆地相的富有机质竹节石页岩中的有机质堆积作用,主要受到以下三个因素之间的复杂的非线性相互作用所控制:生产率、保存作用和沉积作用速率;更为特别而且重要的是,基于高密度保存的竹节石化石(含量可以超过30%),研究区的泥盆纪富有机质竹节石页岩,除了这三个因素之外,浮游动物的“生物碳泵(the biological carbon pump)”作用过程,将是这些竹节石页岩富集有机质的另外一个重要机理。The Devonian period is a significant geological time marked by widespread deposition of organic-matter-rich shales.Within an inter-platform basin facies dominated by deep-water deposits in the region from southern Guizhou to central Guxngxi,a remarkable accumulation of organic-matter-rich tentaculitid shales exceeding 600 meters in thickness developed during the Emsian to Frasnian ages.These shales exhibit characteristics that make them a potential target for shale-gas exploration:(1) Relatively higher total organic carbon(TOC) values consistently exceed 2%~4%,reaching up to 5% to 6%.(2) During the early to middle Devonian(Amsian Age),organic carbon content is typically enriched in massive organic-matter-rich tentaculitid shales with the monolayer thickness exceeding 100 meters,formed during periods of third-order relative sea-level rise.Conversely,calcareous shales and muddy limestones of the shelf facies,formed during sea-level falls,exhibit depleted organic carbon content.(3) Within the Frasnian Age Liujiang Formation,dominated by silicalites,organic carbon content is typically enriched in massive organic-matter-rich tentaculitid sales with the monolayer ranging from 30 to 40 m thick,formed during the periods of third-order sea-level fall.This contrasts with silicalites of the pelagic basin facies,which show lower organic carbon content during periods of third-order relative sea-level rise.The accumulation of organic matter in these tentaculitid shales is controlled by complicated,nonlinear interactions between productivity,preservation,and sedimentation rates.Importantly,the high density of tentaculitid fossils demonstrates that the accumulation of organic matter within organic-matter-rich tentaculitid shales is genetically related to the biological carbon pump of zooplankton.

关 键 词：富有机质竹节石页岩 重要的潜在性页岩气勘探目的层 泥盆系 黔桂地区 

分 类 号：P618.13[天文地球—矿床学]