摘要:
十字沟蛇绿岩产出于东昆仑西段祁漫塔格结合带东部,主要由蛇纹岩、辉长岩、辉绿岩、基性火山岩及硅质岩等组成。其中,从超基性岩—基性岩—基性火山岩,具稀土总量逐渐增加,轻稀土弱亏损型特征,基性火山岩为洋脊玄武岩,总体岩石化学成分与大洋中脊低钾拉斑玄武岩相当,三者的配分型式基本一致,说明其继承了源区地幔的特征,微量元素显示基性火山岩具弧后盆地玄武岩特点。εNd(t)比值表明玄武岩来自亏损地幔源区,总体地球化学特征显示以N-MORB型为主,兼具有E-MORB型的特征,形成于与俯冲作用有关的弧后盆地环境,形成时代为晚奥陶世。后期至少经历了3期以上构造变形变质作用的叠加改造,于早志留世运移至地表。
Abstract:
The Shizigou ophilite occurs in the western of East Kunlun,that is the eastern of the suture zone in Qimantage.Its L-RRE elements have weakly depleted features,with a gradual increase of the total of REE from ultra-basic rocks to basic rocks and basic volcanic rocks,which belong to MORB and the whole rock chemical compositions of which are consistent with low-Ktholeiite of the MORB.They all inherit the characteristic of the source of the mantle with the same distribution patterns,and their REE show a characteristic of basic volcanic rocks and back-arc basin basalts.The ratio of the εNd (t) shows the source of basalts is from D-mantle,and the overall geochemical features suggest the main composition feature of N-MORB with the characteristic of E-MORB at the same time.They formed at the subduction-related environment of the back-arc basin at Late Ordovician and experienced more than three superposition and transformation of the tectonic deformation and the metamorphism and finally transported to the surface at Early-Silurian.
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