赤峰托河盆地流纹岩年代学、地球化学特征及其地质意义  

Geochronology, Geochemical Characteristics, and Geological Significance of the Rhyolite from Tuohe Basin, in Chifeng

作　　者：姜山[1] 巫建华[2] 王常东[1] 祝洪涛[1] 赵博[1] 刘洋[1] JIANG Shan;WU Jianhua;WANG Changdong;ZHU Hongtao;ZHAO Bo;LIU Yang(NO.243 Geological Party,CNNC,Chifeng 024000,China;State Key Laboratory Breeding Base of Nuclear Resources and Environment,East China Institute of Technology,Nanchang 330013,China)

机构地区：[1]核工业二四三大队,赤峰024000 [2]东华理工大学核资源与环境国家重点实验室培育基地,南昌330013

出　　处：《高校地质学报》2018年第6期896-906,共11页Geological Journal of China Universities

基　　金：国家自然科学基金项目(41372071);中国核工业地质局项目(201614);中国地质调查局矿产地质调查专项(DD2016013606)联合资助

摘　　要：赤峰托河火山盆地位于大兴安岭南端内蒙古赤峰市克什克腾旗境内,处于西拉木伦河—长春缝合带以南、康宝—围场—赤峰—开源断裂带以北的辽源地块,盆地中的长英质火山岩系角度不整合于下二叠统额里图组、于家北沟组之上,并被新近系汉诺坝组玄武岩不整合覆盖。SHRIMP锆石U-Pb年龄表明,盆地火山岩系中流纹岩锆石的206Pb/238U年龄为158.5±1.3 Ma,属晚侏罗世早期岩浆活动的产物,应归入新民组。托河流纹岩具有较高的SiO_2含量(68.6%～72.6%),A/CNK值<1.1,标准矿物刚玉的含量<1%;ΣREE含量较高,轻稀土富集,负铕异常显著;(^(87)Sr/^(86)Sr)i=0.709244～0.713168,ε_(Nd)(t)=-8.76～-8.42,TDM2=1656～1629Ma,(^(206)Pb/^(204)Pb)i=17.271～17.326,(^(207)Pb/^(204)Pb)i=15.401～15.413,(^(208)Pb/^(204)Pb)i=37.614～37.696,δ^(18)OV-SMOW=4.1‰～4.5‰。经对比托河盆地流纹岩与红山子盆地、芝瑞盆地流纹岩、流纹斑岩,它们主量元素、微量元素和Sr-Nd-Pb-O同位素地球化学特征基本一致,指示各盆地的物质来源相同。文章证实赞同前人提出的物质来源既与地壳(特别是下地壳)有关,也与地幔特别是EMI型地幔有关的观点。在(Yb+Ta)-Rb和Y-Nb图解上,托河盆地流纹岩均显示板內拉张的构造环境。类比红山子盆地的岩石组合、地质时代、同位素组成、铀矿化特征等,提出托河盆地条件更优越,认为今后盆地内的铀矿勘查工作可参照红山子铀钼矿床的模式开展。Tuohe volcanic basin is located in the Keshiketeng,Inner Mongolia,southern segment of the Great Xing'an Range.It belongs to the Liaoyuan block,which is located between Xar Moron River-Changchun suture zone and Kangbao-Weichang-Chifeng-Kaiyuan fault zone.The felsic volcanic rocks unconformably overlie the lower Permian Elitu Formation and are overlain by basalts in the basin.The zircon SHRIMP U-Pb ages of rhyolites in the base indicate a^206Pb/^238U age of 158.5±1.3 Ma,suggesting that it is the product of the early stage of Late Jurassic magmatism,belonging to the Xinmin Formation.The Tuohe rhyolites show high content of SiO2 A/CNK<1.1,the content of standard mineral corundum is less than 1%,highΣREE and the LREE are enriched with an negative Eu abnormaly,(^87Sr/^86Sr)i=0.709244~0.713168,εNd(t)=-8.76^-8.42,TDM2=1656~1629 Ma,(^206Pb/^204Pb)i=17.271~17.326,(^207Pb/^204Pb)i=15.401~15.413,(^208Pb/^204Pb)i=37.614~37.696,δ^18OV-SMOW=4.1‰~4.5‰.The main elements,trace elements and Sr-Nd-Pb-O isotopes geochemical characteristics of rhyolite in Tuohe basin are basically the same as those of rhyolite and rhyolite porphyry in Hongshanzi Basin and Zhirui Basin,implying that the material sources of these basins are the same.This paper supports the notion that the material sources are related to both the crust,especially the lower crust,and the mantle,especially the EMI-type mantle.On the diagram of(Yb+Ta)-Rb vs.Y-Nb,the rhyolite in the Tuohe Basin shows that it is an intra-plate tectonic setting.Comparing with the rock assemblages,geological ages,isotopic composition,and uranium mineralization characteristics of the Hongshanzi basin,the mineralization conditions in Tuohe basin are better.This study suggests that future exploration of uranium deposits in the basin should be conducted with the guide from the model of Hongshanzi uranium-molybdenum deposits.

关 键 词：流纹岩 地球化学 Sr-Nd-Pb-O同位素 构造环境 新民组 托河 

分 类 号：P588.141[天文地球—岩石学] P597[天文地球—地质学]