内蒙古大青山石拐盆地侏罗系元素地球化学特征及沉积环境指示意义  

Elemental Geochemistry characteristics of Jurassic and indication of sedimentary environment of Shiguai Basin,Daqingshan,Inner Mongolia,China

作　　者：梁子若 侯明才[1] 曹海洋 晁晖[1] LIANG Ziruo;HOU Mingcai;CAO Haiyang;CHAO Hui(State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation Chengdu University of Technology,Chengdu 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),成都610059

出　　处：《成都理工大学学报（自然科学版）》2020年第3期307-317,共11页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家973计划项目(2015CB453001)。

摘　　要：研究内蒙古大青山石拐盆地侏罗纪的古气候、古水深和古盐度等环境信息。对石拐盆地侏罗系13件细粒沉积岩样品进行了主元素和痕量元素地球化学测试,分析了古沉积环境演化特征。研究表明:①古盐度指标Li、Sr、Ga和Sr/Ba值指示五当沟组、召沟组和大青山组为淡水沉积环境,长汉沟组为淡水-微咸水环境;②古氧化-还原指标U/Th、V/Cr、Ni/Co和V/(V+Ni)值指示研究区为氧化环境,其中召沟组为弱氧化环境,石拐群向大青山组氧化程度逐渐增强;③古水深计算指示五当沟组、长汉沟组和大青山组为浅水环境,召沟组为浅水-半深水环境;④古气候指标(古气候指数、化学蚀变指数、Rb/Sr和Sr/Cu值)指示古气候由石拐群的暖湿气候向大青山组的半干热气候转变。研究区随着气候变得越加炎热干旱,蒸发作用加强,水体变浅,盐度逐渐升高,氧化作用越来越强。Major and trace element geochemistry of 13 samples of Jurassic fine-grained sedimentary rocks has been analyzed in order to understand the paleoclimate,paleobathymetry,paleosalinity and other environmental information of the Shiguai Basin in Daqingshan area of Inner Mongolia.Accordingly,the evolution characteristics of paleosedimentary environment of the basin have been studied.Analysis of paleosalinity indexes of Li,Sr,Ga and Sr/Ba indicated that the Wudanggou Formation,Zhaogou Formation and Daqingshan Formation were characteristic of freshwater sedimentary environment, and Changhangou Formation was of freshwater brackish water environment.The paleo-oxidation-reduction indexes of U/Th,V/Cr,Ni/Co and V/(V+Ni)revealed that the study area was an oxidizing environment,in which the Zhaogou Formation was in a weak oxidation environment,and the oxidation degree from Shiguai Group to Daqingshan Formation was gradually enhanced.Calculation of ancient water depth showed that the Wudanggou Formation,Changhangou Formation and Daqingshan Formation were in a shallow water environment,while Zhaogou Formation was in a shallow to semi deep water environment.Paleoclimate indexes,such as chemical alteration index(CIA),Rb/Sr and Sr/Cu indicated that the paleoclimate changed from warm and humid climate of Shiguai Group to semi dry and hot climate of Daqingshan Formation.As the climate became hotter and drier in the study area,evaporation intensified,water became shallower,salinity gradually increased,and oxidation became stronger and stronger.

关 键 词：侏罗系 石拐盆地 古环境 古气候 沉积环境 

分 类 号：P595[天文地球—地球化学] P512.2[天文地球—地质学]