新疆塔吾尔别克金矿区赋矿火山岩地球化学特征与构造意义

GEOCHEMICAL CHARACTERISTICS OF VOLCANIC ROCKS IN THE TAWUERBIEKE GOLD DEPOSIT,XINJIANG AND ITS TECTONIC IMPLICATION

针对塔吾尔别克金矿区赋矿火山岩展开的岩相学和主量、微量及稀土元素地球化学研究,结果显示:该区火山岩w(SiO_2)为48.93%~62.24%,w(K_2O)在1.05%~4.03%,w(TiO_2)为0.55%~0.86%,w(MgO)为2.28%~7.98%,w(Al_2O_3)介于12.04%~17.52%,w(Na_2O+K_2O)值为3.39%~5.59%,里特曼指数σ变化于1.49~2.45,显示钙碱系列火山岩;在TAS图解中该区火山岩样品分布在玄武安山岩—安山岩—英安岩区域;微量元素分析表明,岩石轻稀土相对富集、重稀土元素相对亏损的特点(LREE/HREE=4.72~6.55),且具有明显的的Eu负异常(δEu=0.35~0.67);火山岩整体富集LREE,U,Th,大离子亲石元素Rb,K;亏损高场强元素Nb,Ta,P,Ti;是岛弧岩浆作用的典型地球化学标志。在火山岩La/Yb-Sc/Ti判别图解上,表明火山岩的构造环境与大陆边缘弧密切相关。结合区域构造背景和岩石地球化学特征,推测构造背景可能为俯冲带大陆边缘弧环境。

The study on the petrography, major elements, trace elements and rare earth elements of the volcanic rocks in the Tawuerbieke gold deposit shows that the SiO2 contents are in the range of 48.93%-62.24%, K2O and TiO2 contents are in the range of 1.05%-4.03% and 0.55%-0.86%,MgO and Al2O3 contents are in the range of 2. 28%-7. 98% and 12.04%- 17.52%,respectively. The contents of Na2 O＋K2 O display calc-alkaline characteristics based on the Rittmann index,in the range of 3.39%-5.59%. On the TAS diagram,the volcanic rocks plot in the field of the basalt andesite-andesite-dacite. The trace elements analysis shows that the rocks are enriched in LREE and depleted in HREE（LREE/HREE is 4. 72-6.55） with significantly negative Eu anomaly （δEu=0.35-0. 67）. The rocks all show enrichment in LREE,U,Th,LIFE（ such as Rb,K） and depletion in HFSE （including Nb, Ta, P, Ti）, which is a typical geochemical feature of island arc magmatism. It is revealed that the tectonic setting of the volcanic rocks is closely related to the continental margin arc in the La/Yb-Sc/Ti diagrams. On the basis of the re- gional tectonic background and the geochemical characteristics of the rocks, presumably, the tectonic setting most likely was the continental margin arc in the subduction zone.