西天山乌孙山地区大哈拉军山组火山岩形成的构造背景  

The Tectonic Setting of Volcanic Rocks for DahalaJunshan Formation in Wusun Mountain Region,West Tianshan Mountain

作　　者：程春华[1,2] 张芳荣[2] 余泉[2] 楼法生[2] 

机构地区：[1]中国地质大学(武汉),湖北武汉430074 [2]江西省地质调查研究院,江西南昌330030

出　　处：《东华理工大学学报（自然科学版）》2010年第1期22-28,共7页Journal of East China University of Technology(Natural Science)

基　　金：新疆中央专项资金项目(ZYZXKD200607)

摘　　要：大哈拉军山组火山岩是以火山碎屑岩为主夹少量熔岩的陆相火山岩,属海陆交互相沉积环境。火山岩中的玄武岩具有低硅、高Al,Ca,K2O/Na2O比值及富铁镁矿物质矿物特征,属碱性玄武岩系列。玄武岩的Mg#0.34～0.69,平均为0.53,低于原生岩浆Mg#的范围而大于地壳物质Mg#值。微量元素含量大于下地壳平均值而高于上地壳平均值,总体表现为富集Rb,Th,U,Ta,P,Ti,而过渡金属元素Cr,Ni,Co含量低,岩浆形成过程中有地壳物质的参与。研究表明,大哈拉军山组玄武质岩浆形成于板内裂谷环境,其形成可能与古天山洋俯冲板片在早石炭世垮塌有关。Dahalajunshan formation volcanic rocks are mainly volcaniclastic rocks of the continental,clipping a small amount of volcanic lava,and transitional land-sea sedimentary environment.Basalt volcanic rocks are alkaline basalt sequence,with low silica,high-Al,Ca,K2O/Na2O ratio and rich iron-magnesium mineral.Mg values of the Basalt are 0.34~0.69,averaging 0.53,lower than the primary magmatic but greater than its scope of crustal material.Trace elements is greater than the averaging value of the lower crust but higher than the upper crust.On the whole,the basalt volcanic rocks have the feature of enriching Rb,Th,U,Ta,P,Ti,with the lower content of transition metal elements of Cr,Ni,Co,showing that there had been involved in crustal material during the process of forming magma.The studies have shown that dahala Junshan Formation basaltic magma formed in the intraplate rift environment,maybe related to the slab collapsing of the ancient Tianshan ocean during the early Carboniferous.

关 键 词：构造背景 火山岩 大哈拉军山组 乌孙山地区 西天山 

分 类 号：P588.14[天文地球—岩石学]