鲁西新泰孟家屯2.7Ga变质沉积岩与黑云斜长片麻岩锆石Hf同位素特征  

Hf Isotopic Compositions of Zircons from 2.7 Ga Metasedimentary Rocks and Biotite-Plagioclase Gneiss in the Mengjiatun Formation Complex,Western Shandong Province

作　　者：杜利林[1,2] 杨崇辉[1] 庄育勋[3] 韦汝征 万渝生[1,5] 任留东[1] 侯可军[6] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国地质调查局,北京100037 [4]灵宝黄金股份有限公司,河南灵宝472500 [5]北京离子探针中心,北京100037 [6]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

出　　处：《地质学报》2010年第7期991-1001,共11页Acta Geologica Sinica

基　　金：中国地质科学院地质研究所基本科研业务费项目(编号J0721;J0907);中国地质调查局地质调查项目(编号1212010611802;1212010811033);国家自然科学基金项目(编号40672127)资助成果

摘　　要：对出露于山东新泰孟家屯2.7Ga的孟家屯岩组中石榴石石英岩(M08)、含十字石石榴石黑云母石英片岩(D242-Y2)和黑云斜长片麻岩(M03)(TTG质片麻岩)进行锆石Lu-Hf同位素分析。石榴石石英岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001730～0.002546、0.281249～0.281360,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000123～0.002070、0.281241～0.281318;含十字石石榴石黑云母石英片岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001334～0.002169、0.281226～0.281324,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000445～0.001375、0.281227～0.281309;黑云斜长片麻岩锆石176Lu/177Hf、176Hf/177Hf变化范围为0.000315～0.000847、0.281186～0.281265。孟家屯岩组石榴石英岩、含十字石石榴石黑去母石英片岩中碎屑(岩浆)锆石和黑云斜长片麻岩中岩浆锆石的εHf(t)分别为3.75～7.26、2.31～7.26和3.21～6.27,同时TDM1与其U-Pb年龄非常接近,表明它们起源于新生地壳的部分熔融。结合区域研究资料认为,2.7Ga是鲁西重要的一期构造岩浆热事件,也可能是华北克拉通重要的构造岩浆活动时期。变质沉积岩中许多变质增生锆石相对于核部岩浆锆石低176Lu/177Hf、高176Hf/177Hf,显示变质作用过程中石榴石的存在对锆石的Lu-Hf同位素体系有很大影响。Lu-Hf isotopic compositions of zircons separated from the garnet quartzite（M08）,staurolite-bearing garnet-biotite-quartz schist（D242-Y2）of the Mengjiatun formation complex and biotite plagioclase gneiss（M03）of the TTG gneisses at Mengjiatun village,Xintai City,western Shandong Province,have been analyzed through the La-MC-ICP-MS method.All the rocks mentioned above were formed 2.7Ga ago.Among them,the magmatic cores of detrital origin zircons of the garnet quartzite give the 176Lu/177Hf and 176Hf/177Hf ranges 0.001730～0.002546 and 0.281249～0.281360,respectively,and the zircon rims of the sample have the 176Lu/177Hf and 176Hf/177Hf ranges 0.000123～0.002070 and 0.281241～0.281318,respectively.The magmatic cores of detrital origin zircons from the staurolite-bearing garnet-biotite-quartz schist yield the 176Lu/177Hf and 176Hf/177Hf values 0.001334～0.002169 and 0.281226～0.281324,respectively,and the metamorphic rims of the zircons from the schist 0.000445～0.001375,0.281227～0.281309,respectively.While the ratios of magmatic zircons from the biotite plagioclase gneiss are 0.000315～0.000847,0.281186～0.281265,respectively.εHf（t）values of the magmatic（detrital）zircons from garnet quartzite and staurolite-bearing garnet-biotite-quartz schist of the Mengjiatun formation complex and the orthogneiss are 3.75～7.26,2.31～7.26 and 3.21～6.27,respectively.In addition,the TDM1 ages of the zircons of all the samples are close to the SHRIMP zircon U-Pb ages,suggesting they were derived from partial melting of the juvenile crustal materials.Combining with the regional geology information,the authors deduce that the 2.7Ga magmatism is an important magmatic tectonothermal event in western Shandong Province area,even in the North China Craton.Many zircons in the metasedimentary rocks show the tendency that the metamorphic overgrowing rims have lower 176Lu/177Hf but higher 176Hf/177Hf values than that of the magmatic cores,demonstrating the substantial influence of the metamorphic garnet on the

关 键 词：孟家屯岩组 变质沉积岩 黑云斜长片麻岩 锆石HF同位素 构造岩浆事件 

分 类 号：P597[天文地球—地球化学]