川西北地区须家河组古环境分析与沉积演化特征  

Analysis of the paleowater property of the Xujiahe Formation in northwest Sichuan and its geological significance

作　　者：芦刚 王长城[1,2] 邓宾[1,2] 杨荣军 刘四兵[2] 刘重江 金鑫[1,4] 苟明星 LU Gang;WANG Changcheng;DENG Bin;YANG Rongjun;LIU Sibing;LIU Chongjiang;JIN Xin;GOU Mingxing(State Key Laboratory of Oil and Gas Reservoir Geology and Development Engineering,Chengdu University of Technology,Chengdu,Sichuan 610059,China;School of Energy,Chengdu University of Technology,Chengdu,Sichuan 610059,China;China Petroleum Erploration and Development Research Institute,Beijing 100083,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室成都理工大学,四川成都610059 [2]成都理工大学能源学院,四川成都610059 [3]中国石油勘探开发研究院,北京京100083 [4]成都理工大学沉积地质研究院,四川成都610059

出　　处：《矿物岩石》2024年第4期166-177,共12页Mineralogy and Petrology

基　　金：国家自然科学基金青年科学基金项目(批准号:42002122);四川省自然科学基金重点项目(编号:2024NSFSC0008)。

摘　　要：关于川西北地区须家河组古环境特征与沉积演化模式一直存在争议。弄清该问题不仅有助于理解印支运动对川西坳陷形成的控制作用,而且对于须家河组致密砂岩气藏的勘探具有重要的指导意义。本次研究基于野外露头剖面、岩石标本和薄片鉴定等资料,结合主量元素、微量元素及硼锶元素等多种地球化学手段,对川西北地区晚三叠世须家河组沉积环境和沉积特征进行了研究,进而探讨周缘造山带的构造演化对盆内沉积体系的控制作用。结果表明,在晚三叠世,川西北地区须家河组自下向上发育海相-海陆过渡相-陆相沉积,海水逐渐从北向南退出的过程。须一段沉积期,川西北地区与外海相连通,样品古盐度平均值为11.9‰,古水体以咸水-半咸水为主,分析为海相沉积环境。龙门山造山带由北向南逐渐隆升,沉积体系向南迁移。须二段样品古盐度平均值为6.0‰,整体有所降低,但存在3个古盐度值较大的样品,表明该时期盆地仍有海水注入,可能与间歇性的海侵有关,分析为海陆过渡相沉积。龙门山的大规模隆升使得湖盆具有一定的封闭性,盆内逐渐以陆相沉积为主。须三段-须四段样品古盐度平均值为5.7‰,分析为正常陆相沉积环境。龙门山造山带的隆升与古水体性质的变化,影响了川西北地区晚三叠世须家河组的沉积演化过程。This paper examines the debated sedimentary evolution of the Upper Triassic Xujiahe Forma-tion in the western Sichuan Depression,aiming to clarify the impact of the Indo-China movement on the development of the western Sichuan Depression and its role in controlling the Xujiahe Formation tight sandstone gas reservoir.Sedimentary characteristics and paleo-water conditions in the northern part of the western Sichuan Depression were analyzed using sedimentary outcrop data,thin-section petrography,and whole-rock geochemistry.Additionally,the study explores how tectonic evolution in the surrounding oro-genic belts influenced sedimentary systems within the basin.The findings indicate that the sedimentary e-volution of the Xujiahe Formation in the northern western Sichuan Depression was primarily shaped by tec-tonic activity in the Qinling and Longmen Mountain orogenic belts.During the initial sedimentary phase(the first member of the Xujiahe Formation,T_(3)^(x2)),marine sedimentation dominated,with a brackish pa-leo-water body and a restricted lake basin located in the northern study area.In the middle stage(the sec-ond member,T_(3)^(x2))),the paleo-water body transitioned to a mix of brackish and fresh water.The uplift of the Longmen Mountain orogenic belt progressed from north to south,driving rapid southward expansion of the lake basin.In the later stages(the third to fifth members,T^(3)x^(3)-T3x^(5)),the paleo-water body be-came predominantly fresh water.The significant uplift of the Longmen Mountain range eventually led to the complete closure of the lake basin,resulting in a fully continental depositional environment.

关 键 词：川西北地区 须家河组 古环境特征 造山带隆升 沉积演化 

分 类 号：P534.51[天文地球—古生物学与地层学]