辽西医巫闾山晚侏罗世伸展事件的时限来自同构造岩脉的年代学证据

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1、2012年l2月，第l8卷，第4期，647—660页高校地质学报December2012，Vo1．18，No．4，P．647-660GeologicalJournalofChinaUniversities辽西医巫闾山晚侏罗世伸展事件的时限来自同构造岩脉的年代学证据张必龙，朱光，谢成龙，柳小明，陈印1．合肥工业大学资源与环境工程学院，合肥230009；2．西北大学大陆动力学国家重点实验室，西安710069摘要：位于燕山构造带东端的医巫闾山变质核杂岩经历了两次地壳伸展活动，早期在NNE-SSW拉伸背景下形成了现

2、今围绕医巫间山岩体周缘分布的拆离韧性剪切带与相应的变质核杂岩，晚期隆升过程中由于拉伸方向转变又叠加发育了瓦子峪伸展韧性剪切带。早期伸展变形中，围绕在拆离韧性剪切带及变形下盘中侵入了大量不同变形样式的同构造花岗岩脉。通过对不同阶段侵入的岩脉进行LA—ICP—MS锆石u—Ph定年，显示该核杂岩的活动时间为157～149Ma。医巫间山地区晚侏罗世伸展活动的确定，暗示华北克拉通北部可能从晚侏罗世已经开始发生破坏，到早白垩世达峰期并遍及整个华北克拉通东部。关键词：医巫间山变质核杂岩；同构造岩脉；锆石u—Ph定年；伸展

3、变形中图分类号：P539．2文献标识码：A文章编号：1006—7493(2012)04—0647—14TimingofLateJurassicExtensionintheYiwulvshanArea，WesternLiaoning：Ge0chr0n0l0gicalEvidencefromSyn-KinematicGraniticDikesZHANGBilong’ZHUGuang’，XIEChenglong’，LIUXiaoming，CHENYin，1．SchoolofResourceandEnvironme

4、ntalEngineering，HefeiUniversityofTechnology，Hefei230009，China；2．StateKeyLaboratoryofContinentalDynamics，NorthwestUniversity，Xi’an710069，ChinaAbstract：Yiwultishanmetamorphiccorecomplex(MCC)，situatedintheeasternYanshanstructuralbelt，hasexperiencedtwoDhasesof

5、erustalextensionalactivities：AnearlydevelopmentofdetachmentductileshearzonearoundtheYiwultishanplutonunderaNNE—SSWextensionalregime，andasubsequenttruncationofitssouthwesternsegmentbylaterWaziyuductileshearzonebecauseofachangeinextensionaldirectionduringdom

6、ing．Intheearlyextensionalperiod，therewereagreatdealofsyn—kinematicgraniticdikeswithdifierentdeformationstylesintrudedinthedetachmentshearzoneanditsdeformedlowerplate．LA—ICP——MSzirconU——PbdatingresultsofthesedikessuggestthatYiwultishanmetamorphiccorecomplex

7、wasformedbetween157Maand149Ma．TheLateJurassicextensionalactivitiesintheYiwultishanareaimplythatdestructionmighthavebeenhappenedinthenorthernpartofNorthChinaCratonsinceLateJurassicandreachedpeakperiodthroughoutthewholeeasternNorthChinaCratonintheEarlyCretac

8、eous．Keywords：Yiwultishanmetamorphiccorecomplex；syn·-kinematicdikes；zirconU——Pbdating；extensionaldeformationFirstauthor：ZHANGBilong．Ph．D．Candicate．E-mail：zhbl一88@126．com收稿日期2011-07—19；修回日期：2011-12—24基金项目国家自然科