西天山吐拉苏盆地大哈拉军山组火山岩地球化学特征及构造意义  

Geochemical Characteristics of the Dahalajunshan Formation Volcanic Rocks in the Tulasu Basin of Western Tianshan and its Tectonic Implications

作　　者：夏换[1,2] 陈根文[1] 刘群[1,2] 罗勇[1,2] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640 [2]中国科学院研究生院,北京100049

出　　处：《大地构造与成矿学》2011年第3期429-438,共10页Geotectonica et Metallogenia

基　　金：国家305项目(2011BAB06B02-3;2006BAB07B01-04);国家自然科学基金项目(40773014)联合资助

摘　　要：吐拉苏盆地大哈拉军山组由两组火山岩组成,一组为玄武安山岩、安山岩,SiO2含量介于54.8%～59.4%之间,另一组为流纹岩,SiO2含量为70.6%～74.1%,两组岩石具有相似的稀土和微量元素分配型式,均富集U、Th、K、Pb,而亏损Nb、Ta和Ti,同时两组岩石的一些微量元素对比值基本一致,表明流纹岩是本区玄武安山质岩浆结晶分异形成,初始岩浆可能是由受俯冲流体交代的地幔部分熔融,同时岩浆上升过程中受到上覆地壳混染作用。根据岩石地球化学特征,结合区域大地构造位置及大哈拉军山组形成的时间分析,推测吐拉苏盆地大哈拉军山组形成于大陆边缘岩浆弧。The volcanic rocks of the Dahalajunshan Formation in the Tulasu basin are mainly composed of two groups.One group of the volcanic rocks is basaltic andesite and andesite,with SiO2 contents ranging from 54.8% to 59.4%,while the other group is rhyolite,with SiO2 contents between 70.6% and 74.1%.These two group rocks share similar REE patterns,enriched in U,Th,K,Pb,and depleted in Nb,Ta and Ti.Moreover,the two groups have similar Nb/Ta,Th/Ta,Ce/Nb,Zr/Hf ratios,which indicates that the rhyolite was formed through crystallization differentiation of the andesitic magma.The magma might have been derived from partial melting of the metasomatized mantle wedge and contaminated by the overlying crust during ascend.Considering the petrogeochemical characteristics and the regional tectonic evolution when the Dahalajunshan Group was formed,we believe that the Dahalajunshan Group in the Tulasu basin was formed in a back-arc basin.

关 键 词：大哈拉军山组 地球化学 吐拉苏盆地 西天山 

分 类 号：P595[天文地球—地球化学]