Geochemical Characteristics of the Upper Permian Longtan Formation from Northeastern Sichuan Basin:Implications for the Depositional Environment and Organic Matter Enrichment

作     者：XIAO Wei ZHANG Bing YANG Kai WANG Yan WEN Siyu MA Kai CAO Gaoquan XIAO Wei;ZHANG Bing;YANG Kai;WANG Yan;WEN Siyu;MA Kai;CAO Gaoquan

作者机构：Earth Exploration and Information Technology Key Laboratory of Ministry of EducationChengdu University of TechnologyChengdu 610059China State Key Laboratory of Oil and Gas Reservoir Geology and ExploitationChengdu University of TechnologyChengdu 610059China Institute of sedimentary geologyChengdu University of TechnologyChengdu 610059China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2023年第97卷第4期

页      面：1196-1213页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：the General Fund of the National Natural Science Foundation of China(Grant No.42272184) National Natural Science Foundation of China(Grant Nos.42230311 and 91755215)for their support of this paper 

主　　题：geochemical characteristics sedimentary environment organic matter accumulation upper Permian northeastern Sichuan Basin 

摘      要：A set of organic-rich shales of the upper Permian Longtan Formation,which is widely developed in the northeastern part of the Sichuan Basin,is a key formation for the next step of exploration and *** present,most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales,and basic studies on the palaeoenvironment and organic matter(OM)enrichment mechanism have not been fully carried *** this paper,we recovered the sedimentary palaeoenvironment by mineralogical,elemental geochemical and organic geochemical analyses,and explored the enrichment mechanism of OM under the constraints of palaeoenvironmental *** shales can be divided into two stages of sedimentary evolution:compared with the shales of the Lower Longtan Formation,the shales of the Upper Longtan Formation are relatively rich in quartz,poor in clay and carbonate minerals,and the OM type changes from typeⅢto typeⅡ_(2).The depositional environment has undergone a change from sea level rise,from warm and wet climate to dry and cold climate,and from oxygen-poor condition restricted to open reduction environment;the land source input has decreased,the siliceous mineral content has increased,the biological productivity has improved,and the deposition rate has changed from high to low.A depositional model was established for the shales of the Longtan Formation,reflecting the differential reservoir formation pattern of organic *** the Lower Longtan Formation shales,the most important factors controlling OM content are terrestrial source input and deposition rate,followed by paleoclimate and paleooxygen *** the Upper Longtan Formation shales,the most important controlling factor is paleo-productivity,followed by sedimentation *** depositional model constructed for the Upper and Lower Longtan Formation shales can reproduce the enrichment of organic matter and provide a basis for later exploration and deve