卡拉麦里地区黑山头组火山岩地球化学特征及构造环境分析  

GEOCHEMISTRY CHARACTERISTICS OF VOLCANIC ROCKS OF HEISHANTOU FORMATION IN KALAMAILI,EAST JUNGGAR,AND TECTONIC SETTINGS IMPLICATION

作　　者：杨高学[1,2] 李永军[1,2] 严镜[1,2] 吴宏恩 杨宝凯[1,2] 闫存兴 

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [2]长安大学地球科学与资源学院,陕西西安710054 [3]新疆维吾尔自治区有色地质矿产勘察院,新疆乌鲁木齐830000

出　　处：《新疆地质》2011年第3期257-262,共6页Xinjiang Geology

基　　金：中央高校基本科研业务费专项资金(CHD2010ZY005);区域地质矿产调查项目(QD200508)联合资助

摘　　要：黑山头组火山岩位于新疆东准噶尔卡拉麦里蛇绿岩带东北缘,主要为玄武岩、玄武质安山岩和安山岩,属钙碱性-高钾钙碱性系列.火山岩Mg#介于8.62～43.90,全碱含量较高(Na2O+K2O为4.19%～9.33%),且Na2O(2.20%～4.93%)>K2O(0.54%～4.40%),TiO2和P2O5含量较高(分别为0.68%～1.28%和0.10%～0.28%),轻稀土元素(LREE)相对重稀土元素(HREE)富集((La/Yb)N=1.06～3.56),无明显重稀土分馏((Gd/Yb)N=0.73～1.54),弱铕异常(δEu=0.60～1.17)和铈异常(δCe=0.89～0.95),强烈富集LILE(如Rb,Th),适度富集Ba,K等,强烈亏损HFSE(如Nb,Ta),弱亏损Zr,Hf和Ti,显示较明显TNT负异常,较高Ba/La(13.30～124.43)、Ba/Nb(11.48～161.29)和La/Nb(0.86～2.37)比值,较低的Nb/Y(0.2～0.4)、Nb/Ta(7～16)和Zr/Hf(17～37)比值.同位素年代学、地球化学特征及构造环境判别图解综合研究表明,卡拉麦里地区早石炭世岩浆活动显示板内岩浆演化特征,具弧火山岩地球化学痕迹,形成于后碰撞期伸展背景下,是软流圈物质上涌并发生部分熔融,形成岩浆在上升和侵位过程中受早石炭世弧组分混染的产物.Carboniferous volcanic rocks mainly composed of basalts, basaltic andesites and andesites occur within Lower Heishantou Formation, north of Kalamaili ophiolite in the eastern Junggar, and are mainly high K calc-alkaline series. The volcanic rocks have moderate Mg^#（8.62-43.90）values,relatively high alkali（（Na2O＋K2O）=4.19%-9.33%）, and Na20（2.20%-4.93%）〉K2O（0.54% -4.40%）, the content of TiO2 and P2O5 is high（TiOE=0.68%-1.28%,P2O5=0.10%-4）.28%）. The rocks are enriched in LREE more than HREE（（La/Yb）N=1.06-3.56）,and with slight fractionation of HREE（（Gd/Yb）N=0.73-1.54）,without significant Eu and Ce anomalies（δEu=0.60-1.17, δCe=0.89-0.95）, strongly enriched LILE（like Rb and Th）, moderate enriched Ba and K, and intensely depleted in HFSE（like Nb and Ta）, weak depleted Zr, Hf and Ti, shows clearly ＂TNT＂ negative anomalies. The rocks have high Ba/La（13.30-124.43）, Ba/Nb（11.48-161.29）, La/Nb（0.86-2.37）,but low Nb/Y（0.2-0.4）,Nb/Ta（7-16）,Zr/Hf（17-37） ratios.Geochronology and geochemistry characteristics, along with the discrimination diagrams, indicate the Early Carboniferous magmas movement not only shows the characteristics of intraplate magmatic evolution, but also has traces of arc volcanic rock geochemistry, they are maybe from extensional settings of post-collisional period. They are produced by the ascending and melting of asthenospheric material, and the magmas were contaminated by the arc component formed before Early Carboniferous in the processes of uplift and emplacement.

关 键 词：新疆 卡拉麦里 黑山头组 地球化学 构造环境 

分 类 号：P588.14[天文地球—岩石学]