摘要
通过岩心观察、氩离子抛光-场发射扫描电镜、全岩X射线衍射,锆石U-Pb年龄测试等分析方法,对松辽盆地中央坳陷区白垩系青山口组含火山灰的岩石类型、矿物组分、分布特征及年龄进行了分析,从构造环境、火山喷发期次及全球缺氧事件3个角度对古龙页岩中的有机质富集作用进行了分析。研究结果表明:①松辽盆地青山口组以灰色、灰白色凝灰岩为主,单层厚度为0.5~3.0 cm,矿物成分以黏土(伊蒙混层)为主,质量分数超过50%,其次为菱铁矿、长石和石英,部分可见黄铁矿;凝灰岩与上下岩层呈突变接触或者锯齿状接触关系。②研究区火山灰纵向上主要分布于青一段、青二段,其中青一段火山灰厚度更大,平面上,青一段火山灰厚度表现为“西厚东薄”,青二段火山灰表现为“东厚西薄”;火山灰的平均年龄为93.820±0.240 Ma。③研究区青山口组沉积初期,快速热沉降与拉张应力构造背景的双重作用为火山喷发提供了动力,火山灰的喷发为湖相藻类等生物的繁殖及有机质的富集提供了营养物质;青一段、青二段页岩层系至少发育6期火山灰沉积,代表了6期火山喷发事件,青一段Q1层系的火山灰由盆地西部周缘岩浆喷发而形成,青二段火山灰主要来源于盆地东部火山喷发物质。④研究区青山口组火山灰的形成时间与全球缺氧事件OAE2的时间(93.6~94.3 Ma)一致,火山灰带来的营养物质为随后0.04~0.08 Ma的生物勃发和有机质富集提供了重要保障。
Through analyses of core observation,argon ion polishing-field emission scanning electron microscopy,whole rock X-ray diffraction and zircon U-Pb dating,the types,mineral components,distribution characteristics,and zircon U-Pb dating of rocks contained volcanic ash from Cretaceous Qingshankou Formation in the central depression of Songliao Basin were analyzed.The organic matter enrichment influence of Gulong shale was analyzed from tectonic environment,volcanic eruption period,and global hypoxia event.The results show that:(1)Qingshankou Formation in Songliao Basin mainly develop gray and gray white tuff,with a single layer thickness of 0.5-3.0 cm.The mineral composition is mainly clay(illite-montmorillonite mixed layer),with a mass fraction exceeding 50%,followed by siderite,feldspar,and quartz,and some pyrite.The tuff beds exhibit either abrupt contacts or scalloped contact with adjacent layers.(2)Vertically,the volcanic ash in the study area is mainly distributed in the first and second sections of Qingshankou Formation,and the thickness of the volcanic ash in the first section is larger.While in the plane,the thickness of the volcanic ash exhibits“west thick and east thin”in the first section of Qingshankou Formation,and“east thick and west thin”in the second section,the average age of volcanic ash is 93.820±0.240 Ma.(3)In the study area,during the initial stage of sedimentation of Qingshankou Formation,the dual effects of rapid thermal subsidence and extensional stress tectonic background provided the driving force for volcanic eruptions.The eruption of volcanic ash provided nutrients for the reproduction of creatures,such as lacustrine algae,and the enrichment of organic matter.At least 6 periods of volcanic ash beds have deposited in the shale series of the first and second sections of Qiangshankou Formation,representing 6 volcanic eruption episodes.The volcanic ash in Q1 layer of the first section is formed by magma eruption around the western periphery of the basin,while the volcanic ash of the second section mainly originates from volcanic eruption materials in the eastern part of the basin.(4)The formation time of volcanic ash from Qingshankou Formation in the study area is consistent with the time of global hypoxia event OAE2(93.6-94.3 Ma).The nutrient materials brought by volcanic ash are the important guarantee for the sustained biological bloom and organic matter enrichment over the subsequent 0.04-0.08 Ma.
作者
刘丽娟
李军辉
付秀丽
白月
郑强
LIU Lijuan;LI Junhui;FU Xiuli;BAI Yue;ZHENG Qiang(State Key Laboratory of Continental Shale Oil,Daqing 163712,Heilongjiang,China;Exploration and Development Research Institute of PetroChina Daqing Oilfield Co.,Ltd.,Daqing 163712,Heilongjiang,China)
出处
《岩性油气藏》
北大核心
2025年第5期145-154,共10页
Lithologic Reservoirs
基金
黑龙江省自然科学基金项目“古龙页岩层系细粒沉积特征及有机质富集机理研究”(编号:JQ2024D003)资助。
关键词
火山灰
锆石U-Pb定年
全球缺氧事件
拉张构造
快速热沉降
古龙页岩
青山口组
白垩系
松辽盆地
volcanic ash
zircon U-Pb dating
global hypoxia events
extensional structure
rapid thermal subsidence
Gulong shale
Qingshankou Formation
Cretaceous
Songliao Basin
