西天山尼勒克一带大哈拉军山组火山岩地球化学特征及构造意义  

Geochemical Characteristics of Volcanic Rocks from Dahalajunshan Formation in the Nileke Area of Western Tianshan and its Tcetonic Implications

作　　者：李鸿[1] Li Hong(No.9 Geological Party,BGMERD of Xinjiang,Urumqi,Xinjiang,830009,China)

机构地区：[1]新疆维吾尔自治区地质矿产勘查开发局第九地质大队,新疆乌鲁木齐830009

出　　处：《新疆地质》2017年第2期145-150,共6页Xinjiang Geology

基　　金：新疆尼勒克县胡吉尔台一带1:5万区域地质矿产调查项目(XJQD2007-06)资助

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(SiO_2=70.78%~76.85%)、富铝(Al_2O_3=11.05%~15.54%)、富碱(K_2O+Na_2O=7.87%~9.71%)、贫钙(CaO=0.16%~1.42%)、低钛(TiO_2=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^(-6)~88.77×10^(-6)),稀土分布模式为轻稀土富集右倾型,铕负异常明显(δEu=0.59~0.81),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。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(ΣREE=80.66×10-6～241.8×10-6)with LREE-rich patterns and significant negative Euanomalies(δEu=0.59～0.81).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.

关 键 词：西天山 大哈拉军山组 地球化学 构造环境 

分 类 号：P588.14[天文地球—岩石学]