开鲁盆地宝龙山地区姚家组物源及铀源分析:来自地球化学特征及碎屑锆石U-Pb年代学证据  

PROVENANCE AND URANIUM SOURCE ANALYSIS OF THE YAOJIA FORMATION IN THE BAOLONGSHAN AREA,KAILU BASIN:EVIDENCE FROM GEOCHEMISTRY AND DETRITAL ZIRCON U-Pb GEOCHRONOLOGY

作　　者：陈梦雅 聂逢君[1] CHEN Mengya;NIE Fengjun(School of Earth Sciences,East China University of Technology,Nanchang,Jiangri 330013,China)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013

出　　处：《矿物岩石》2023年第4期33-48,共16页Mineralogy and Petrology

基　　金：国家自然科学基金项目(批准号:U2244205,U2067202,41772068)。

摘　　要：开鲁盆地位于松辽盆地西南部,是中国北方砂岩型铀矿勘查的重点地区。自钱家店铀矿床发现以来,盆地内上白垩统姚家组中相继发现了一系列具有工业价值的铀矿床,显示其勘探潜力。为查明研究区目的层砂岩的沉积物源和铀源特征,本次研究对开鲁盆地宝龙山地区姚家组砂岩进行了碎屑组分、全岩地球化学和碎屑锆石LA-ICP-MS定年分析。结果表明:研究区砂岩主要为岩屑砂岩,成分成熟度低,具有近物源,沉积较快的特征。样品轻稀土元素(LREE)含量为80.27×10^(-6)~184.67×10^(-6),平均119.21×10^(-6);重稀土元素(HREE)的含量为11.38×10^(-6)~23.31×10^(-6)(平均15.02×10^(-6)),LREE/HREE为6.91~8.93(平均7.92),表明轻稀土富集,重稀土亏损,轻重稀土高度分馏。稀土元素球粒陨石标准化曲线具有明显的右倾及负Eu异常(δEu=0.49~0.84,平均0.57)。CIA指数(58.41~74.80)及CIW指数(74.52~95.74)指示姚家组母岩经历了中等至强烈的风化蚀变。物源主要形成于上大陆地壳活动大陆边缘环境。碎屑锆石U-Pb年龄为126~2501 Ma,具有两个主要的年龄范围:126~155 Ma和245~276 Ma,此外还有少量早古生代及古元古代的锆石。通过区域对比分析,明确了姚家组碎屑物质主要来自大兴安岭南段,少量来自燕山造山带的贡献。母岩主要为物源区广泛出露的长英质火成岩,并混合有少量变质岩组合。除了为研究区提供碎屑物质外,源区富含铀的长英质火成岩还提供了长期、稳定和良好的铀源,表明研究区的铀矿勘探潜力巨大。The Kailu Basin in the southwest of Songliao Basin is an important area for uranium exploration featured by sandstone type in northern China.Since the discovery of Qianjiadian uranium deposit,a series of uranium deposits with industrial value have been discovered successively in Yaojia Formation of Upper Cretaceous in the basin.In this paper,detrital composition,whole rock geochemistry and LA-ICP-MS dating of detrital zircons from Yaojia Formation sandstone in Baolongshan area,Kailu Basin have been studied in order to find out the sediment source and uranium source characteristics of the target sandstone in the study area.The results show that the sandstone in the study area is mainly lithic sandstone with low compositional maturity,having close provenance and fast deposition characters.The content of light rare earth elements(LREE)in the samples ranges from 80.27×10^(-6)to 184.67×10^(-6),with an average of 119.21×10^(-6);the contents of heavy rare earth elements(HREE)range from 11.38×10^(-6)to 23.31×10^(-6)(average 15.02×10^(-6)),and LREE/HREE ranges from 6.91 to 8.93(average 7.92).These suggest the characteristic of enriched light rare earth element,depleted heavy rare earth element and highly fractionated light-heavy rare earth.The normalized curve of rare earth element chondrites shows obvious right-leaning and negative Eu anomaly(δEu=0.49-0.84,mean 0.57).CIA index(58.41-74.80)and CIW index(74.52-95.74)indicate that the parent rock of Yaojia Formation has experienced moderate to strong weathering.The provenance of sandstones is the active continental margin environment of the upper continental crust.The dated U-Pb ages of detrital zircons range from 126 to 2501 Ma,with two main age ranges:126 to 155 Ma and 245 to 276 Ma,with a small number of early Paleozoic and Paleoproterozoic zircons.Regional comparative analysis reveals that the detrital material of Yaojia Formation mainly comes from the southern part of the Great Hinggan Mountains,and a small amount comes from the Yanshan orogenic belt.The parent

关 键 词：开鲁盆地 姚家组 地球化学特征 U-PB年龄 铀源 

分 类 号：P588.2[天文地球—岩石学] P597.3[天文地球—地质学]