大别山东部含柯石英榴辉岩锆石U-Pb测年——多期超高压变质作用证据  

U-Pb ZIRCON DATING ON COESITE-BEARING ECLOGUES FROM EASTERNDABIE AREA, CENTRAL CHINA-THE EVIDENCE FORMULTIEPISODE ULTRAHIGH PRESSURE METAMORPHISM

作　　者：简平[1] 杨巍然[2] 周惠芳 

机构地区：[1]宜昌地质矿产研究所 [2]中国地质大学 [3]天津地质矿产研究所

出　　处：《华南地质与矿产》1996年第4期14-21,共8页Geology and Mineral Resources of South China

基　　金：地质行业基金(9514);地矿部重大基础(8502206)项目部分成果

摘　　要：大别造山带东段南、北大别两类不同产状的柯石英榴辉岩同位素地质年代学对比研究表明:(1)石马榴辉岩超高压变质事件发生于471±2Ma前,并受到海西斯热事件(榴辉岩重结晶)的迭加;(2)碧溪岭与超镁铁质岩共生的榴辉岩是晚元古代北大别古岛弧(镁铁—超镁铁质堆晶岩系)超高压变质作用的产物,镁铁—超镁铁质堆晶岩系可能形成于914±56Ma;(3)大别地区东部加里东期和印支期超高压变质带并置,反映了造山带形成多期“开”“合”的复杂演化史.Two typical coesite-bearing eclogites have been geochronologically studied by U-Pb zircon dating, one, Shima eclogite from the southern Dabie area, occurring in the garnet-bearing gneisses and the other associated with metamafic-ultramafic rocks at Bixiling from the northern Dabie area.The results show: (1)The ultrahigh pressure event(UHP)occurred 471±2 Ma ago in the southern Dabie area. (2)The peak metamorphism related to subduction has been dated at 263 ± 48Ma-230± 5 Ma from Bixiling eclogite, northern Dabie area, confirming the multiepisode ultra-high pressure metamorphism in Dabie orogen. (3)The mafic-ultramafic protolith of Bixiling eclogite formed 914±56 Ma ago. It is also demonstrated there are a few inherited zircons (1700-2775Ma)in Bixiling eclogite, indicating contamination from old continental crust incorporated during rock-forming process of protolith and/or eclogitization. This is in accordance with the geological setting of continental margin-islands.

关 键 词：大别山 柯石英榴辉岩 铀 铅 榴辉岩 同位素测年 

分 类 号：P588.3[天文地球—岩石学] P578.941[天文地球—地质学]