秦岭-大别勉略缝合带湖北随州周家湾变质玄武岩地球化学及其大地构造意义

GEOCHEMICAL FEATURES AND ITS TECTONIC SIGNIFICANCE OF THE META-BASALT IN ZHOUJIAWAN AREA,MIANLUE SUTURE ZONE,  QINLING-DABIE MOUNTAINS,HUBEI PROVINCE

周家湾变质玄武岩岩片位于秦岭－大别微板块与扬子板块的分界断裂构造混杂带内，形成于印支期。岩石为一套亚碱性拉斑系列火山岩，具扁平型稀土配分型式；Ｔｈ／Ｙｂ，Ｔａ／Ｙｂ，Ｔｉ／Ｚｒ，Ｔｉ／Ｙ，Ｚｒ／Ｙ比和Ｎｂ，Ｔｈ丰度表明其形成于初始型小洋盆的大地构造环境。该岩片可能是秦岭勉略缝合带在大别南缘出露的岩石学证据。

The metabasalts in Zhoujiawan area are located at the boundary tectonic melange between QinlingDabie microplate and Yangtze plate.The rocks were formed during IndoChinese epoch and belong to subalkaline tholeiite association.They show a flat REE distribution pattern and a slight LREE enrichment.The ratios of Th/Yb,Ta/Yb,Ti/Zr,Ti/Y,Zr/Y and Nb,Th mass density indicate that the metabasalts in this region are very similar to the MORB originated from depletive mantle of asthenosphere and imply a small initial ancient ocean tectonic setting between QinlingDabie and Yangtze plates during middle PaleozoicEarly Mesozoic era.This metabasalt block should be a important evidence which indicate that the MianxianLueyang suture zone had extended to the south of Dabie mountain. 