巴音戈壁盆地巴北凹陷G4井火山岩锆石U-Pb年代学及其地质意义
Zircon U-Pb Chronology of Volcanic Rocks From Well G4 in Babei Sag of the Bayin Gobi Basin and Its Geological Significance
张海云 1刘波 1李鹏 1叶茂 1邢亚杰1
作者信息
- 1. 核工业二〇八大队,内蒙古 包头 014010
- 折叠
摘要
巴北凹陷是巴音戈壁盆地西部拐子湖坳陷的一个次级构造单元,近年来凹陷内取得了一定的铀矿找矿成果,但是总体的工作程度较低,地层的划分对比一直存在较大争议,深部火山岩未做过年代学研究,地质年代尚不明确.为了精确划分凹陷内的沉积盖层,明确找矿目的层,本次研究选取了凹陷北部G4线剖面进行细致解剖,系统采取样品进行岩石学、锆石U-Pb年代学研究,以期为以上问题提供证据.分析结果表明,钻井深部玄武岩所测得的锆石年龄有两组,分别为(126±4.2)Ma、(243.5±1.7)Ma,两组锆石均为岩浆成因锆石,第一组年龄代表该套火山岩的形成时代,即早白垩世中期,第二组年龄代表火山活动捕获的早期岩浆锆石年龄.玄武岩的形成时代很好地约束了地层的形成时代,说明该层玄武岩所在地层为下白垩统苏红图组下段.基于火山岩年龄的核定,对区内沉积盖层进行了精细化划分,总结了地层划分标志,结合沉积体系、地层铀含量等综合分析,厘定了下白垩统银根组为主要的铀矿找矿目的层.
Abstract
Babei sag is a secondary structural unit in the western Guaizihu Depression of the Bayingobi Basin.In recent years,certain achievements have been made in uranium exploration within the sag.However,the overall research level is relatively low in the sag and there is a significant controversy in the division and comparison of strata,no chronological study was conducted in the deep volcanic rocks,and the geological age is still unclear.In order to accurately divide the sedimentary cover layer within the depression and clarify the target layer for uranium exploration.In this study,the G4 line section in the northern part of the sag was selected for detailed dissection,and samples were systematically taken for petrological and zircon U-Pb dating studies so as to provide evidence for the above issues.The analysis results indicate that there are two sets of zircon ages measured by drilling deep volcanic rocks,namely(126±4.2)Ma and(243.5±1.7)Ma.Both sets of zircons are magmatic zircons,and the younger age represents the formation age of the set of volcanic rocks,that is,the middle Early Cretaceous.The second set of ages represents the age of early magmatic zircons captured by volcanic activity.The formation age of basalt effectively constrains the formation age of the strata,indicating that the formation of this layer of basalt is located in the lower member of the Lower Cretaceous Suhongtu Formation.Based on the verified volcanic rock age,the sedimentary cover layers in the area have been finely divided and the stratigraphic classification criteria have been summarized.Based on comprehensive analysis of sedimentary system and uranium content in the strata,the Lower Cretaceous Yingen Formation has been determined as the main uranium exploration target layer.
关键词
玄武岩/U-Pb定年/地层划分/苏红图组/巴北凹陷/沉积体系Key words
basalt/U-Pb dating/stratigraphic division/Suhongtu Formation/Babei sag/sedimentary system引用本文复制引用
基金项目
内蒙古巴音戈壁盆地及周缘铀矿资源调查评价与勘查项目(202203)
中核集团集中研发项目(中核科发2021-143号)
出版年
2024
国家科技期刊平台
NSTL
万方数据