华北克拉通南缘下汤地区古元古代构造热事件——地球化学特征、锆石SHRIMP U-Pb定年和Hf同位素研究  

Paleoproterozoic Tectono—Thermal Events in the Xiatang Area,Lushan County,Southern Margin of the North China Craton——Evidence from Geochemical Features,Zircon SHRIMP Dating and Hf Isotopic Analysis

作　　者：黄道袤[1] 万渝生[2] 张德会[3] 董春艳[2] 赵元艺[1] 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质科学院地质研究所,北京离子探针中心,北京100037 [3]中国地质大学,北京100083

出　　处：《地质论评》2016年第6期1439-1461,共23页Geological Review

基　　金：国家自然科学基金资助项目(编号:41472169);基本科研业务费(编号:K1508);中国地质调查局工作项目(编号:1212011220465;1212011120142;1212010811033;12120113013700)的成果~~

摘　　要：本文报道了华北克拉通南缘鲁山县下汤地区早前寒武纪变质基底岩石的地球化学、锆石定年和Hf同位素组成。上太华岩群两个变质沉积岩样品的变质锆石年龄为1.91～1.93 Ga，由于变质作用强烈改造，碎屑锆石真正的形成年龄难以确定。碎屑锆石εHf（t）和tDM2（CC）（Hf）分别为－0.26～10.41和2244～2958 Ma。一个变质辉长闪长岩样品的捕获锆石年龄为2.32 Ga，变质锆石年龄为1.93 Ga。捕获锆石的εHf（t）和tDM2（CC）（Hf）分别为－1.79～2.22和2695～2940 Ma。两个片麻状奥长花岗岩样品的岩浆锆石和变质锆石年龄分别为1.93 Ga和1.92 Ga，岩浆锆石的εHf（t）和tDM2（CC）（Hf）分别为－3.30～1.30和2481～2764 Ma。一个片麻状正长花岗岩样品的岩浆锆石和变质锆石年龄分别为1.93 Ga和1.92 Ga，岩浆锆石的εHf（t）和tDM2（CC）（Hf）分别为－3.67～2.40和2415～2788 Ma。结合地球化学和前人研究结果，可得出如下结论：①上太华岩群形成时代形成于古元古代早期；②进一步支持了该区存在约2.3 Ga岩浆作用的认识；③发现广泛分布的1.91～1.93 Ga壳源奥长花岗岩和正长花岗岩；④确定1.91～1.94 Ga变质作用在该区广泛发育。Objectives：Xiatang area is located in the southern margin of the North China Craton,where Paleoproterozoic tectono—thermal events widely occur.This paper reports whole-rock geochemistry and zircon ages and Hf isotope compositions of rocks from the early Precambrian basement in the Xiatang area, to understand the early Precambrian magmatism and metamorphism. Methods：Rock geochemical analysis,SHRIMP U-Pb zircon dating and Hf isotope analysis. Results：wo metasedimentary rock samples of the Upper Taihua Group have the ages of 1 .9 1 ～1 .93 Ga for metamorphic zircons, and the ages of detrital zircons are difficult to be determined because of strong recrystallization.The εHf（t）and tDM2（CC）（Hf）of the detrital zircons are -0.26 ～10.41 and 2.24 ～2.96 Ga, respectively.A meta-gabbroic diorite sample has captured and metamorphic zircons of 2.32 Ga and 1 .93 Ga.The captured zircons have εHf（t）values and tDM2（CC）（Hf）ages ranging from -1 .79 to 2.22 and 2.70 Ga to 2.94 Ga, respectively.Two gneissic trondhjemite samples have magmatic and metamorphic zircons of 1 .93 Ga and 1 .92 Ga , the magmatic zircons have εHf（t）values and tDM2（CC）（Hf）ages being -3.30 ～1.30 and 2.48 ～2.76 Ga, respectively.A gneissic syenogranite sample has magmatic and metamorphic zircons of 1 .93 Ga and 1 .92 Ga, respectively,with the εHf（t）and tDM2（CC）（Hf）of magmatic zircon being -3.67 ～2.40 and 2.42 ～2.79 Ga, respectively. Conclusions：Combined with whole-rock geochemical compositions and early study,the main conclusions can be drawn as follows：1 ）The Upper Taihua Group was formed in early Paleoproterozoic;2）this study surppots the conclusion that there was ～2.3 Ga magmatism in the area;3）widespread 1.91 ～1.93 Ga crustally-derived trondhjemtie and syenogranite are identified;4）1.91 ～1.94 Ga metamorphism was well developed.

关 键 词：华北克拉通 古元古代 锆石SHRIMP定年 Hf同位素 表壳岩 岩浆作用 

分 类 号：P597.3[天文地球—地球化学] P534.3[天文地球—地质学]