中文摘要：

底坎儿组火山岩是东天山石炭纪火山岩的重要组成部分，其分布范围北至吐-哈盆地南缘，南至沙泉子断裂，其地球化学特征对于探讨觉罗塔格地区的构造环境演化具有重要的意义。本文对底坎儿组火山岩的主量、微量及sr—Nd同位素进行了研究，以探讨岩石成因及其形成的构造环境。结果表明，底坎儿组火山岩为一套钙碱性的玄武岩-安山岩-流纹英安岩组合，为石榴石-尖晶石橄榄岩地幔部分熔融的产物。玄武岩经历了橄榄石和单斜辉石的结晶分异，安山岩和流纹英安岩则经历了斜长石和磁铁矿的结晶分异。火山岩相对富集轻稀土元素和大离子亲石元素，亏损高场强元素，玄武岩的微量元素配分型式与弧玄武岩相似，而部分安山岩及流纹英安岩的微量元素配分型式与上地壳相似。底坎儿组火山岩的Nd同位素特征[eNd（t）=-0．14～5．69]及微量元素地球化学特征显示其具有中等亏损地幔源区特征，岩浆来自于俯冲流体交代的地幔，岩浆演化过程遭受了有限的地壳混染。基性火山岩微量元素配分型式及构造环境图解表明其可能形成于弧后盆地环境。

英文摘要：

As an important part of Carboniferous volcanic rocks in eastern Tianshan Mountains, the volcanic rocks of the Dikan＇ er Formation have great constraints on the tectonic evolution of the Juoluotage belt. These volcanic rocks are bounded by the southern margin of Tu-Ha basin in the north and the Shaquanzi fault in the south. The major and trace elements and Sr-Nd isotopes of the volcanic rocks are discussed in this paper to con- strain the petrogenesis and tectonic settings. The volcanic rocks are composed of calc-alkali basalt, andesite and rhyodacite assemblages, which are products of partial melting of garnet-spinel lherzolite mantle. The primary magma has experienced crystallization differentiation of olivine and clinopyroxene for basalt, and that of plagio- clase and magnetite for andesite and rhyodacite. They are relatively enriched in large-ion-lithophile elements and light rare-earth elements, and are depleted in high-field-strength elements. The patterns of trace elements of basalt are similar to those of arc basalt, while the trace element patterns of intermediate-acid rocks are similar to those d the upper crust. Neodymium isotopic characteristics [eNd（t）=-0.14～5.69] the volcanic rocks indicate derivation from a moderately depleted mantle source which was metasomatized by subduc- tion-related fluid and involvement of minor crustal contamination. The trace element patterns of basalt and the plots for tectonic setting suggest that the volcanic rocks were probably formed in a back-arc basin environment.