鲁东官山榴辉岩与围岩接触关系的新发现及其对年代学的启示  

New Discovery of the Contact Relation between Eclogite and Country Rocks in Guanshan, Eastern Shandong, and Its Enlightenment for Chronology

作　　者：宋明春[1] 金振民[2] 王来明[3] 张希道 李远友 

机构地区：[1]山东省第四地质矿产勘查院 [2]中国地质大学地球科学学院,武汉430074 [3]山东省地质调查院,济南250013

出　　处：《地质学报》2003年第2期238-244,T007,共8页Acta Geologica Sinica

基　　金：中国地质调查局国土资源大调查项目--1:25万日照幅;烟台-威海幅片区修测及1:50万大别造山带编图的成果

摘　　要：鲁东官山榴辉岩呈透镜状包于变质含霓石碱性花岗岩中,榴辉岩的片麻理与主岩片麻理总体呈交切关系,局部可见变质含霓石碱性花岗岩呈细小岩枝状脉贯入榴辉岩中。变质含霓石碱性花岗岩锆石U-Pb法下交点年龄为231±25 Ma,上交点年龄为818±66 Ma。发现了闪长玢岩脉斜切式侵入榴辉岩及变质含霓石碱性花岗岩的接触关系,且闪长玢岩脉中有榴辉岩捕虏体,这种现象指示:闪长玢岩侵位时榴辉岩已折返至地壳较浅部位。研究表明,榴辉岩与变质含霓石碱性花岗岩共同经历了新元古代的超高压变质作用,但变质作用发生时含霓石碱性花岗岩可能处于熔融状态,榴辉岩是其中的固相包体。Lenticular eclogites are surrounded by meta-aegirine-bearing alkali granites in Guanshan. eastern Shandong Province. Gneissosity of the eclogites is dissected by the meta-aegirine-bearing alkali granites and thin apophyses of the latter are locally injected into the eclogites. Zircon U-Pb isotopic ages of the meta-aegirine-bearing alkali granites are 231 ± 25 Ma (lower intercept age) and 818? 66 Ma (upper intercept age). The authors discovered the contact relation for the intrusion of dioritic porphyrite into the eclogite and meta-aegirine-bearing alkali granites, and discovered the xenolith of the eclogites in the dioritic porphyrite. This fact indicates that the eclogites had already exhumed from mantle depth to crustal surface when the dioritic porphyrite intruded itself into the eclogites and country rocks. This study indicates that the eclogites and meta-aegirine-bearing alkali granites experienced the same UHP metamorphism in the Neoproterozoic, but the meta-aegirine-bearing alkali granites were probably in a melting state and the eclogite appeared as solid enclaves in the melts.

关 键 词：榴辉岩 锆石U-PB年龄 花岗岩 超高压变质作用 固相包体 接触关系 同位素年龄 

分 类 号：P588.3[天文地球—岩石学] P597.3[天文地球—地质学]