银额盆地居延海坳陷早白垩世断陷期沉积演化特征及其对砂岩型铀矿形成的影响  

Early Cretaceous Sedimentary Evolution of Juyanhai Depression in Yin’e Basin and its Influence on the Formation of Sandstonetype Uranium Deposits

作　　者：杨喆 刘武生[1] 牛霆 纪宏伟 张文东 李伟涛 YANG Zhe;LIU Wusheng;NIU Ting;JI Hongwei;ZHANG Wendong;LI Weitao(Beijing Research Institute of Uranium Geology,Beijing 100029,China;Research Institute No.203,CNNC,Xi’an,Shaanxi 710086,China)

机构地区：[1]核工业北京地质研究院,北京100029 [2]核工业二〇三研究所,陕西西安710086

出　　处：《世界核地质科学》2023年第2期162-173,共12页World Nuclear Geoscience

基　　金：中核集团集中研发项目“砂岩型铀矿多重耦合地质成矿作用与时空定位”(编号:中核科发2021-143号)资助。

摘　　要：银额盆地是我国北方发育砂岩型铀矿的中-新生代断陷湖盆之一,盆地西部居延海坳陷的沉积体系与砂体展布等特征尚不清晰,制约了该地区砂岩型铀成矿的研究。文章在银额盆地居延海坳陷路井-天草凹陷地区,利用野外露头、钻井、地震和测井等资料,结合区域地层特征和构造演化背景,对其断陷期各阶段的沉积体系进行详细研究,探讨了沉积演化过程对砂岩型铀成矿的影响。结果表明,居延海坳陷主要发育一套冲积扇-扇三角洲-湖泊沉积体系:断陷早期,断裂活动形成窄而长形态的凹陷,近物源区,导致凹陷被扇三角洲平原和前缘过渡亚相充填;断陷中期,湖平面升高,扇三角洲沉积面积缩小,开始沉积半深-深湖亚相;断陷晚期,湖水变浅,扇三角洲平原萎缩,扇三角洲前缘向凹陷中央推进。居延海坳陷断陷期经历了一次完整的湖侵-湖退的沉积充填过程,相对于断陷早期和晚期,断陷中期形成的退积型扇三角洲前缘亚相砂体有利于形成层间氧化带和铀矿化,可以作为研究区下一步砂岩型铀矿找矿的重点区。Yin’e Basin is one of the Meso-Cenozoic sedimentary rifting lacustrine basins in the northern China,in which sandstone-type uranium mineralization was discovered.However,the few research was reported on the Early Cretaceous tectonic evolution and depositional filling in the western part of the basin,which constrain the prospecting development of sandstone-type uranium mineralization in this area.In this paper,outcrop,drilling,seismic and logging data were used to study the depositional facies by combining with regional stratigraphic characteristics and tectonic background during each period of syn-depositional faulting activities in the Lujing and Tiancao sags of Juyanhai depression,and the influence of depositional evolution process on sandstone-type uranium mineralization was also discussed.The research results showed that the Juyanhai depression mainly developed an alluvial fan-fan delta-lacustrine depositional system.In the earlyfaulting stage,narrow and long sags were formed due to syn-depositional faulting activities,and were filled by fan-delta plain and front subfacies.During the middle-faulting stage,the fan delta subfacies became smaller and the semi-deep lacustrine subfacies began to be deposited due to the lake-level increase.The shallow lake led to the fan delta plain shranking and the fan delta front gradually pinching out center of sags in the late-faulting stage.Juyanhai depression experienced a depositional process from lacustrine transgression to lacustrine regression during the Early Cretaceous depression faulting.Compared with those in the early and late depression faulting,sand bodies within the fan delta front subfacies formed in the middle depression faulting are conducive to develop interlayer oxidized zones for uranium mineralization,which can be used as the key area for the next sandstone-type uranium prospecting in the study area.

关 键 词：沉积演化 断陷湖盆 下白垩统 砂岩型铀矿 银额盆地 

分 类 号：P619.14[天文地球—矿床学]