华北中部造山带南缘洛宁东部太华变质杂岩sims锆石u―pb年龄及其地质意义

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1、华北中部造山带南缘洛宁东部太华变质杂岩SIMS锆石U―Pb年龄及其地质意义　　文章编号：16726561（2016）06082213　　摘要：太华变质杂岩出露于华北克拉通中部造山带南缘，整体呈近EW向展布。洛宁地区的太华变质杂岩岩性多样，保留了至少3个阶段的变质矿物组合。作为前人研究的补充，报道了该地区东部含榴斜长角闪片麻岩和长英质片麻岩的SIMS锆石UPb定年结果，证实该区太华变质杂岩至少保留了3期地质事件的年龄。其中两期岩浆年龄（2.32～2.33Ga和2.18Ga）表明，太华变质杂岩与华北中部造山带中―

2、北段各杂岩一样，共同经历了华北克拉通的地壳再造过程；另一期变质年龄（1.94～195Ga）表明，太华变质杂岩的变质作用开始时间比该造山带中―北段大部分杂岩区早了约01Ga，变质作用延续时间也长了约01Ga。这再次说明华北中部造山带古元古代末的构造变质事件是一个漫长且复杂的过程。　　关键词：地质年代学；太华变质杂岩；斜长角闪片麻岩；长英质片麻岩；SIMS锆石UPb年龄；构造变质事件；华北中部造山带　　中图分类号：P597文献标志码：A　　SIMSUPbAgesofZirconandTectonicSignifi

3、canceofTaihua　　MetamorphicComplexintheEasternLuoning，theSouthern　　TerminalofTransNorthChinaOrogen　　CHENHongxu，WANGHao，PENGTao，ZHANGHui，WUChunming25　　（CollegeofEarthSciences，UniversityofChineseAcademyofSciences，Beijing100049，China）　　Abstract：Locatedinthesout

4、hernterminalofthePalaeoproterozoicTransNorthChinaOrogen（TNCO），garnetbearingfelsicandamphiboliticgneissesintheeasternLuoningterranewithinthenearlyEWstrikingTaihuametamorphiccomplex，preservethreegenerationsofmetamorphicmineralassemblages，i.e.，theprograde，peak

5、andretrogrademetamorphicstages.Theprogradeassemblages（M1）compriseofhornblende+plagioclase+quartzinclusionspreservedinthegarnetporphyroblasts.Themetamorphicpeakassemblages（M2）arerepresentedbythegarnetporphyroblastsaswellasthematrixminerals（plagioclase+hornbl

6、ende+quartz+zircon±biotite±Kfeldspar）.Theretrogradeassemblages（M3）arethefinegrained“whiteeyesocket”symplectiticassemblagesformedbetweentherelictgarnetporphyroblastsandtheadjacentmatrixminerals，consistingofplagioclase+hornblende+quartz.Inordertocomplementour

7、previousresearch，SIMSUPbdatingresultsofzirconsseparatedfromthefelsicandamphiboliticgneissesarereportedhere，whichshowthat（a）theLuoningcomplexrecordstwomagmaticepisodes（2322.33Gaand2.18Ga），suggestingthatthesouthernmostterminaloftheTNCOisalsoinvolvedinthecrust

8、reworking；and（b）thepeak25metamorphiceventtookplaceat1.941.95GaintheLuoningcomplex，implyingthatthePrecambrianmetamorphismoftheLuoningTaihuacomplexnotonlyoccursearlier（～100Ma）than，butalsolastslongerthant