完达山造山带蛇绿混杂岩中变质基性岩的地球化学特征及其地质意义

完达山造山带蛇绿混杂岩中变质基性岩原岩主要有两种类型:在大顶子山和仙人台附近蛇绿岩带中的变质玄武岩地球化学具有T iO2含量偏高,高场强元素N b,T a,Z r,H f等富集,大离子亲石元素R b,Sr,B a等相对富集;LREE富集,体现出洋岛型玄武岩的特征。在靠近跃进山断裂带的跃进山变质杂岩带中采集的变质基性岩原岩具有洋中脊玄武岩的地球化学特征,但R b,B a,Th相对富集,R b,B a,Th都是活跃于地壳中的元素,这些元素丰度值高,与板块拼贴岩石受到明显的蚀变作用有关。

GEOCHEMICAL CHARACTERISTICS AND TECTONICS MECHANISM OF THE META-BASIC ROCKS FOR OPHIOLITE COMPLEX IN WANDASHAN OROGENIC BELT

The original rock of meta-basic rocks in ophiolite complex of Wandashan orogenic belt can be divided into two sorts.The meta-basalt rocks in ophiolite nappe around the Dadingzishan and Xianrentai show following geochemical characteristics:high content of TiO_2,enrichment in HFSE,such as Nb,Ta,Zr,Hf and enrichment in LILE,such as Rb,Sr,Ba and LREE.The geochemical characteristics Indicate that the meta-basalt rocks belong to the OIB.The geochemical characteristics of the samples of the meta-basic rocks in the Yuejinshan metamorphic complex belt near the Yuejinshan block fault Indicate that the meta-basalt rocks belong to the tholeiite series of MORB,with enrichment in Rb,Ba,Th etc.The fact that the elements of Rb,Ba,Th are rich and active in the crust indicates that the rocks were subjected to erosive metamorphism during the collision of two blocks.