琼河坝矿集区北塔山组火山岩成因及构造环境分析  

ANALYSIS ON BEITASHAN GROUP VOLCANO ROCK FORMATION AND TECTONIC ENVIRONMENT IN QIONGHEBA ORE CONCENTRATION AREA

作　　者：王得权[1,2] 王建国 李培贵 王义忠 刘建朝[2] 张海东[2] 

机构地区：[1]中陕核工业集团公司,陕西西安710054 [2]长安大学,陕西西安710054

出　　处：《矿物岩石》2016年第1期48-56,共9页Mineralogy and Petrology

基　　金：阿尔泰-准噶尔北缘成矿带地质矿产调查研究(1212011120519);中陕核集团公司科技创新项目:黄泥坪;秋树坪地区金成矿规律与成矿预测研究(61150101)

摘　　要：琼河坝矿集区北塔山组火山岩是东准噶尔北缘泥盆纪火山岩的重要组成部分。从玄武岩到安山岩,其Mg~#值为38.74~55.31,暗示母岩浆是经过分异演化的玄武质岩浆。在w(MgO)-w(TiO_2)图解中从玄武岩到安山岩的演化趋势与玄武岩熔体演化趋势线相同。在哈克图解中,从玄武岩到安山岩SiO_2含量与Al_2O_3,MnO,MgO,CaO,Na_2O等主量元素之间,呈较明显的负相关,暗示岩浆在演化过程中,可能发生了Mg,Fe矿物的分离结晶。安山岩ΣREE值为72.50×10^(-6)~98.05×10^(-6),LREE/HREE的值为1.64~4.74;玄武安山岩ΣREE值为68.69×10^(-6)~116.04×10^(-6),LREE/HREE的值为1.51~3.50;玄武岩ΣREE值为65.19×10^(-6)~154.53×10^(-6),LREE/HREE的值为1.59~2.70;总体上表现为稀土含量较低,轻、重稀土分馏不明显,且轻稀土元素较重稀土元素富集。通过对北塔山组火山岩主、微量元素的地球化学特征研究,认为北塔山组形成于火山弧环境,玄武质母岩浆为卡拉麦里洋洋壳向北俯冲到地幔岩石圈区域,在俯冲流体的作用下楔形地幔中的石榴子石橄榄岩-尖晶石橄榄岩发生部分熔融而形成。The Devonian Beitashan Group volcano rocks in Qiongheba of the northern margin of East Junggar consist of basalt and andesite. It reveals the Mg# value of basaltic andesite is 38. 74 -55.31,indicating that the original magma is differentiated from basaltic magma. The evolution trend from basalt to andesite is the same as basalt melting evolution trend line in the w（MgO）-w （TiO2） diagram. SiO2 is obviously negative correlation with MnO, MgO, CaO, NazO and other main elements from basalt to andesite in Harker diagrams, implying that the separation and crystallization of Mg and Fe minerals occurred during the evolution of magma. The EREE value of andesite ranges from 72. 50 × 10^-6 to 98.05 × 10^-6 , and the REE/HREE value from 1.64 to 4.74 the EREE value of basaltic andesite ranges from 68. 69× 10^-6 to 116.04×10^-6 , and the REE/ HREE value from 1.51 to 3. 50; the EREE value of basaltic ranges from 65.19 × 10^-6 to 154.53× 10^-6,and the REE/HREE value from 1.59 to 2.70. Therefore, the Beitashan Group volcanic rocks are characterized by low rare earth content with enrichment of LREE and loss of HREE, while the fractionation of light and heavy rare earth is not obvious. Based on the geochemical characteristics of the trace elements and main elements,it is considered that the Beitashan group volcanic rocks form in volcanic arc environment. The fluid occurred in the northward subduction of Kalamaili oceanic crust to mantle lithosphere results in the partial melting of garnet peridotite and spinel peridotite in the mantle wedge, forming the parent magma.

关 键 词：北塔山组火山岩 微量元素 稀土元素 构造环境 

分 类 号：P597.3[天文地球—地球化学]