【摘要】 对西天山尼勒克一带大哈拉军山组流纹岩类研究表明,岩石具富硅（SiO₂=70.78%⁷6.85%）、富铝（Al₂O₃=11.05%¹5.54%）、富碱（K₂O+Na₂O=7.87%⁹.71%）、贫钙（CaO=0.16%¹.42%）、低钛（TiO₂=0.08%⁰.41%）特征,属钙碱性低钛流纹岩类。稀土元素总量较低(∑REE=50.77×10^-688.77×10^-6),稀土分布模式为轻稀土富集右倾型,铕负异常明显（δEu=0.59⁰.81）,相对富集Rb,Th,K等大离子亲石元素,亏损Nb,Ta,Ti等高场强元素,具较高的Rb/Sr、Nb/Ta和Th/Ta比值和较低的Ti/Zr、Ti/Y及Ta/Yb比值,表明其可能为上地壳部分熔融产物,同时具大陆边缘弧亲缘性。结合区域构造演化,认为伊犁地块北缘早石炭世处于大陆边缘弧环境。更多还原

【Abstract】 Geochemical characteristics of volcanic rocks from the Dahalajunshan formation in the Nileke area of western Tianshan are studied in this paper,and the results show that the volcanic rocks from Dahalajunshan formation belong to calc-alkaline rhyolitic rocks with low Ti,which is characterized by high silica（SiO₂:68.94%⁷9.04%）,high aluminum（Al₂O₃:11.05%¹5.54%）,high alkali（K₂O+Na₂O:7.11%⁹.50%）,and low titanium and calcium（TiO₂:0.17%⁰.55%,CaO:0.18%⁰.84%）.The rocks also have relatively low total Rare Earth Element（REE） content(∑REE =80.66×10^-6241.8×10^-6) with LREE-rich patterns and significant negative Euanomalies（δEu=0.59⁰.81）.The rocks enriched in large ion lithophile elements such as Rb,Th and K,strongly depleted high strength field elements such as Nb,Ta and Ti,with relatively high Rb/Sr,Nb/Ta and Th/Ta ratios and low Ti/Zr,Ti/Y and Ta/Yb ratios.The geochemical characteristics indicate that the rocks may be partial melting of the upper crust,also show their affinity with the continental margin arc,and combine the tectonic evolution of this region,we believe that the volcanic rocks from Dahalajunshan formation is belong to the outcome of continental margin tectonic environment.更多还原