华北克拉通乌拉山地区早前寒武纪岩浆作用和变质作用——锆石SHRIMP U-Pb定年及岩石地球化学研究  

Early Precambrian Magmatism and Metamorphism in Ural Mountain Area,North China Craton:SHRIMP U-Pb Zircon Dating and Rock Geochemical Study

作　　者：张琳[1,2] 董春艳[2] 刘守偈[2] 白文倩[2] 任鹏[2] 万渝生[2] 

机构地区：[1]中国地质大学(北京),北京100083 [2]中国地质科学院地质研究所,北京离子探针中心,北京100037

出　　处：《地质论评》2016年第6期1419-1438,共20页Geological Review

基　　金：国家自然科学基金资助项目(编号:41002062);中国地质调查局项目(编号:1212011220465;1212011120142和1212010811033)的成果~~

摘　　要：乌拉山地区位于大青山地区西侧,变泥砂质岩石大范围出露,并有一定数量变质岩浆侵入岩存在。本文对6个变质岩浆侵入岩进行了锆石SHRIMP U-Pb定年。片麻状闪长岩、片麻状英云闪长岩、片麻状花岗闪长岩和片麻状紫苏花岗岩等4个样品的锆石U-Pb数据点沿谐和线分散分布,n(^(207)Pb)/n(^(206)Pb)年龄从约2.5Ga到约1.8 Ga。变质辉长岩和眼球状石英二长岩锆石U-Pb数据点在谐和线上较集中分布,n(^(207)Pb)/n(^(206)Pb)年龄从约2.0Ga到约1.8 Ga。n(^(207)Pb)/n(^(206)Pb)年龄越小的锆石域通常显示越强烈的重结晶。结合已有研究和地球化学资料,可得出如下结论。(1)乌拉山地区存在新太古代晚期(约2.5 Ga)和古元古代中晚期(约2.0 Ga)岩浆侵入岩,后者形成于伸展构造环境。(2)乌拉山地区遭受新太古代晚期一古元古代早期和古元古代晚期两期构造热事件叠加改造。(3)乌拉山地区部分变泥砂质岩石形成于新太古代晚期,大青山地区原认为形成于古元古代早期的"大青山表壳岩"很可能也形成于新太古代晚期。(4)乌拉山地区和大青山具有类似或相同的早前寒武纪地质演化历史。Objectives：Ural Mountain （Wulashan）is located in the west of Daqingshan area,North China Craton, where metapelites widely occur,with some meta-intrusive rocks.We carried out researches on six meta-intrusive samples （granitoids and meta-gabbro）to understand the early Precambrian magmatism and metamorphism. Methods：SHRIMP U-Pb zircon dating and geochemical analysis. Results：Four samples,including gneissose diorite,gneissic tonalite,gneissic granodiorite and gneissic charnockite,have zircon U-Pb analyses scattering along concordia,with n（^207 Pb）/n（^206 Pb）ages ranging from ～1800 Ma to ～2500 Ma.Zircon U-Pb analyses of meta-gabbro and augen granite are concentrated in concordia, with n（^207Pb）/n（^206Pb） ages ranging from ～1800 Ma to ～2000 Ma.It is common that the stronger recrystallization the zircon domains show,the younger the n（^207 Pb）/n（^206 Pb）age are.The granitoids show the general characteristics of Archean continental crust rocks. Conclusions：① There are late Neoarchean （～2.5 Ga）and middle—late Paleoproterozoic （～2.0 Ga） intrusive rocks in the Ural mountain,the latter is considered to form in an extending environment.② Late Neoarchean—earlyPaleoproterozoic and late paleoproterozoic tectonothermal events have been identified.③At least some metapelites in the Ural mountain are Late Neoarchean in formation age,the “Daqingshan supracrustal rocks”in the Daqing mountain,which was once considered to be early Paleoprotetozoic in formation age,should also form in the late Neoarchean.④The Ural Mountain shows similar or same early Precambrian geological evolution with the Daqing Mountain.

关 键 词：岩浆作用 变质作用 早前寒武纪 锆石SHRIMP U-PB定年 

分 类 号：P534.41[天文地球—古生物学与地层学] P584[天文地球—地质学] P597.3