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大小:3.32 MB
页数:10页
时间:2020-03-23
《内蒙古赤峰地区泥盆纪晚期火山岩的发现及其地质意义.pdf》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、第33卷第9期地质通报VolI33.No.92014年9月GEoLoGICALBULLETIN0FCHINASep.,2014内蒙古赤峰地区泥盆纪晚期火山岩的发现及其地质意义叶浩,张拴宏,赵越,刘建民,何哲峰YEHao,ZHANGShuan—hong。,ZHAOYue,LIUJian—n'fin,HEZhe—feng。1冲国地质科学院地质力学研究所,北京100081;2.国土资源部古地磁与古构造重建重点实验室,北京100081;3.中国地质博物馆,北京1000341.InstituteofGeomechanics,ChineseAcademyo
2、fGeologicalSciences,Beqing100081,China;2.MLRKeyLaboratoryofPaleomagnetismandTectonicReconstruction,Beijing100081,China;3.GeologicalMuseum,ofChina,Bering100034,China摘要:运用LA—ICP—MS锆石u—Pb测年获得华北地块北缘内蒙古赤峰莲花山地区朝吐沟组2件流纹质熔结凝灰岩的形成时代,分别为366Ma_+2Ma和364Ma_+2Ma。测年结果表明,莲花山朝吐沟组火山岩形成于泥盆纪晚期,
3、而不是早石炭世。同时,这一结果也将赤峰地区朝吐沟组的时代限定为泥盆纪晚期,而非早石炭世。莲花山泥盆纪晚期火山岩总体上以富硅、碱、铝,贫铁、镁、钙、钛及过铝质为特征,与本区晚石炭世一二叠纪钙碱性火山岩(如青凤山组或大石寨组火山岩)的特征明显不同。华北地块北缘泥盆纪晚期火山岩的形成可能与早古生代末期一晚古生代初期白乃庙岛弧和华北克拉通北缘弧一陆碰撞后的伸展环境有关。这一构造环境与华北地块北缘泥盆纪碱性岩及基性一超基性岩侵位背景相似。关键词:泥盆纪晚期火山岩;LA—ICP—MS锆石u—Pb测年;朝吐沟组;中亚造山带;华北地块北缘中图分类号:P534.
4、44;P588.14文献标志码:A文章编号:1671—2552(2O14)09—1274—10YeH,ZhangSH,ZhaoY,LiuJM,HeZF.RecognitionofthelatestDevonianvolcanicrocksinChifengarea,northernNorthChinablock,anditsgeologicalimplications.GeologicalBulletinofChina,2014,33(9):1274—1283Abstract:LA——ICP——MSzirconU——Pbdatingoftwor
5、hyolitictufsamplesfromtheChaotugouFormationinLianhuashanareaofChifengonthenorthernmarginoftheNorthChinablockyieldedweightedmean。Pb/。”Uagesof366Ma-+2Maand364Ma+2Ma.respectively.Thenewgeochrono10calresultsindicatethattheLianhuashanvolcanicrockswereeruptedduringthelatestDevonia
6、ninsteadoftheEarlyCarboniferousaspreviouslyconsidered.BecausethevolcanicrocksarelocatedwithintheChaotugouFormationwhichwaspreviouslyconsideredtObeEarlyCarboniferousinage,theageoftheChaotugouFormationshouldevidendybelatestDe—vonian.TheLianhuashanlatestDevonianvolcanicrocksare
7、characterizedbyhighcontentofSiO2,Na2O+K2O,A12O3,1OWcontentofTFe203(0.36%0.70%),MgO,CaO,TiO2andA/CNK>1.1,quitediferentfromthegeochemicalcharacteristicsoftheLateCar—boniferous—Permiancalc—alkalinevolcanicrocksonthenorthernmarginoftheNorthChinablock.Keywords:LatestDevonianvolca
8、nicrocks;LA——ICP——MSzirconU——Pbdating;ChaotugouFormation;CentralAsianOrogen
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