大兴安岭中北段塔尔气地区早白垩世白音高老组火山岩地球化学特征及意义  

Geochemical characteristics and geological implication of volcanic rocks in Early Cretaceous Baiyingaolao Formation from Taerqi area,middle-north part of Da Hinggan mountains

作　　者：王雄[1] 陈跃军[2] 李勇[1] 李森林[1] 王长兵 刘永俊 朱怀亮[5] 吴国学[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林大学古生物学与地层学研究中心,长春130026 [3]云南省核工业209地质大队,昆明650032 [4]辽宁省地质矿产研究院,沈阳110032 [5]天津地热勘查开发设计院,天津300250

出　　处：《世界地质》2015年第1期25-33,共9页World Geology

基　　金：内蒙古呼伦贝尔市阿木辉伊勒特等四幅区域矿产地质调查(NMKD2008-02)

摘　　要：塔尔气地区早白垩世白音高老组火山岩主要由流纹岩、流纹质（含角砾）岩屑晶屑凝灰岩及流纹质岩屑晶屑凝灰熔岩等组成。岩石地球化学研究表明,火山岩具有富铝（Al2O3含量13.37%-15.79%）、富碱（Na2O＋K2O含量6.10%-8.56%）、贫镁钙的特点;稀土元素丰度总量较高,轻、重稀土元素分馏明显[（La/Yb）N=3.72-17.9],且HREE有较明显的凹陷;微量元素以相对富集K、Rb、Ba、LREE等大离子亲石元素,而相对亏损Sr元素以及高场强元素Nb、Ta、Ti为特征。结合前人研究结果表明,塔尔气地区白音高老组火山岩来源于基性下地壳物质的部分熔融。结合火山岩所具有的A型流纹岩的特点,暗示为伸展构造体制下的产物,可能与蒙古—鄂霍茨克洋闭合后的伸展环境有关。The volcanic rocks in Baiyingaolao Formation of Taerqi area are composed of rhyolite,lithic crystal tuff and rhyolitic lithic crystal tuffolava. The geochemical study suggests that the rocks are rich in Al2O3（ Al2O3=13. 37% - 15. 79%） and alkalis（ Na2 O ＋ K2 O = 6. 10% - 8. 56%）,while poor in magnesium and calcium. All samples are characterized by relatively high total REE contents,HREE and LREE have distinct fractionation [（ La /Yb）N= 3. 72 - 17. 9] while the HREE has an obvious sag. The trace element are characterized evidently by enrichment of LILEs（ K,Rb,Ba and LREE）,strong depletion of Sr and HFSEs（ Nb,Ta,Ti）. Combining with the previous studies,we suggest that the volcanic rocks in Baiyingaolao Formation from Taerqi area were originated from partial melting of mafic lower crustal materials,and the rocks have the characteristics of A-type rhyolite,implying they were formed in an extensional setting,which may be caused by the closure of Mongol--Okhotsk Ocean.

关 键 词：塔尔气 白音高老组 地球化学 岩浆来源 酸性火山岩 大兴安岭 

分 类 号：P534.53[天文地球—古生物学与地层学] P595[天文地球—地质学]