摘要
准噶尔盆地东缘喀木斯特地区中侏罗统头屯河组底部砂体是砂岩型铀矿重要的赋矿层位。采用ICP-MS对准噶尔盆地东缘喀木斯特地区中—晚侏罗世西山窑组、头屯河组、齐古组、喀拉扎组不同层位的33件细碎屑岩样品进行微量、稀土元素测试,探讨西山窑组、头屯河组、齐古组、喀拉扎组氧化-还原条件、源区构造背景及古气候演化对铀成矿的影响。研究发现,样品的相对B含量、Sr/Ba、V/(V+Ni)、U/Th、Ni/Co等组合指示,西山窑组、头屯河组、齐古组、喀拉扎组沉积时的古水体介质均为富氧的淡水环境;Fe^(2+)/Fe^(3+)指示西山窑组成煤、成岩形成原生还原层,头屯河组上段与齐古组红层为强氧化环境。西山窑期—喀拉扎期,Sr/Cu、FeO/MnO、Al_(2)O_(3)/MgO等比值总体反映古气候经历了温暖潮湿—干湿交替—半干旱、干旱的转变过程;西山窑组顶部与头屯河组底部为干湿转换的关键时期;CIA、ICV指数反映头屯河组上段、齐古组、喀拉扎组具有构造环境相对稳定的物源区,西山窑期和头屯河早期,准噶尔盆地周缘构造活动性增强。沉积岩构造环境判别图解显示,喀木斯特地区西山窑组、头屯河组、齐古组、喀拉扎组沉积物源主要来自上地壳长英质火成岩源区,同时具有一定量的大陆拉斑玄武岩的混合,其以大陆岛弧构造背景为主,部分物源显示大陆边缘构造背景。综上所述,西山窑期—头屯河期古气候和富氧古水体转变对喀木斯特地区砂岩型铀大规模成矿作用有着重要的指示意义。
The sand body at the bottom of the Middle Jurassic Toutunhe Formation from the Kamusite area in the eastern margin of the Junggar Basin is an important sandstone-type uranium ore bearing horizon.In this paper,thirty-three microclastic rock samples collected from the Middle-Late Jurassic Xishanyao,Toutunhe,Qigu and Kalazha Formations in the eastern margin of Junggar Basin were analyzed for REEs and trace elements by means of ICP-MS.The oxidation-reduction conditions of Xishanyao,Toutunhe,Qigu and Kalazha Formations and tectonic setting of their provenances and paleoclimate change are discussed to understand their implication for uranium mineralization.It is found that the relative B contents,Sr/Ba,B/Ga,U/Th,V/(V+Ni),V/Cr,Ni/Co ratios and other geochemical indices suggest that the the Xishanyao,Toutunhe,Qigu and Kalazha Formations were deposited in the fresh oxygenated water.The Fe^(2+)/Fe^(3+)ratios indicate that the Xishanyao Formation characterized by the appearance of coal seam represent reduced environment,while the red bed in the upper Toutunhe Formation and Qigu Formation indicate a strong oxidation environment.From Xishanyao to Kalazar period,the Sr/Cu,FeO/MnO,Al_(2)O_(3)/MgO ratios indicate that the paleoclimate and paleoenvironment experienced variations from warm-humid to alternated dry-wet,semi-arid and arid.The top of the Xishanyao Formation and the bottom of the Toutunhe Formation are the key periods of dry-wet transformation.The CIA and ICV indexes show that the upper Toutunhe Formation,Qigu Formation and Kalazha Formation have relatively stable provenance.During the Xishanyao and early Toutunhe period,the tectonic activity around the Junggar Basin increased.The discrimination diagram of sedimentary tectonic environment shows that the provenances of the Xishanyao,Toutunhe,Qigu and Kalazar Formations in this study area were dominantly composed by felsic igneous rocks in the upper crust,with certain amount of continental tholeiite.The tectonic background was continental island arc,with part of the prov
作者
程先钰
张天福
程银行
刘行
胡鹏
吴志伟
武志宇
CHENG Xianyu;ZHANG Tianfu;CHENG Yinhang;LIU Xing;HU Peng;WU Zhiwei;WU Zhiyu(Tianjin Center,China Geological Survey,Tianjin 300170,China;Chengdu University of Technology,Chengdu 610059,Sichuan,China;Changqing Industry and Commerce Group,Xi’an 710016,Shaanxi,China)
出处
《地质通报》
CAS
CSCD
北大核心
2022年第11期1950-1966,共17页
Geological Bulletin of China
基金
中国地质调查局项目《京津冀协同发展区暨雄安新区资源环境承载能力监测评价》(编号:DD20221727)
《天山-华北陆块铀钍等矿产资源调查项目》(编号:DD20190813)。
关键词
准噶尔盆地
古环境
中—晚侏罗世
地质调查工程
砂岩型铀矿
地球化学特征
Junggar Basin
paleoenvironment
Middle-Late Jurassic
geological survey engineering
sandstone-type uranium
geological characteristics
