碧口群玻安质岩石地球化学及成岩构造环境  

The Further Study on Geochemical Characteristics and Petrogenesis of the Bininitic Rocks from the Bikou Group,Northern Yangtze Plate

作　　者：李永飞[1] 赖绍聪[1] 秦江锋[1] 刘鑫[1] 王娟[1] 

机构地区：[1]西北大学地质学系,陕西西安710069

出　　处：《东华理工学院学报》2006年第1期43-48,共6页Journal of East China Institute of Technology

基　　金：国家自然科学基金(40234041)

摘　　要：主量及微量元素系统对比表明,碧口南范坝、庙里湾地区的变质玄武岩具有低S、i低Ti、低P、高Mg#和高A l2O3/TiO2的特点,具有玻安质岩的地球化学特点;在N-MORB标准化元素配分图上,亏损高场强元素(Ti,Zr,Y),富集难熔元素(C r,Co,N i),稀土配分模式呈LREE亏损的左倾形式,表明本区岩石可能是早期经历过较高程度部分熔融后亏损难熔地幔楔橄榄岩,在有少量水参与的情况下发生部分熔融形成的。结合本区岛弧拉斑玄武岩的研究,本区玻安质岩石应来自于一个弧前消减环境,这一认识对于确定碧口火山岩系的构造属性具有重要意义。Compared with the major,trace elements of the typical boninite,the metabasalts collected from the Nanfanba-Miaowanli region in the BiKou block can be treated as boninitic characterized by the low-Si ,low-Ti ,low-P, high-Mg^# and High Al2O3/TiO2 ,consistent with geochemical features of boninite;the N-MORB normalized spide diagram display fairly depletion in the HFSE（ Zr,Y, Ti）and enriched in refractory elements（ Cr, Co, Ni） as well as LREE-depletion in Chondrite-normalized REE distribution patterns,both suggesting the boninitic magmas derived from a extremely depletion mantle wedge in the presence of a hydrous fluid, meanwhile signifying the source region had previously ever been undergone a high degree partial melting process yielding primary magmas with enriched LILE. In addition, almost all the samples plotted in the IAB district in the Nb-Zr-Y and Ti-Zr-Y determination diagrams. Consequently, coupled with the island arc tholeiitic basalt（IAT） in the study region,the geochemical characteristics of the study rocks indicate the meta-basalts should be occurred in a fore-arc subduction tectonic setting, which would finally be a great significant to further study on the tectonic background of the Bikou volcanism.

关 键 词：玻安质岩 地球化学 变玄武岩 碧口 

分 类 号：R591[医药卫生—内科学]