中祁连东段化隆群中斜长角闪岩地球化学特征及构造意义  

Geochemistry of amphibolites in Hualong Group of eastern Middle Qilian massif and its tectonic significance

作　　者：高晓峰[1] 李文渊[1] 叶美芳[1] 郭周平[1] 

机构地区：[1]西安地质矿产研究所,陕西西安710054

出　　处：《岩石矿物学杂志》2010年第5期507-515,共9页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目(40772062);中国地质调查局资助项目(1212010911032)

摘　　要：中祁连东段化隆群中斜长角闪岩岩相学特征及主、微量元素地球化学分析结果显示,其原岩为碱性玄武岩。斜长角闪岩表现出轻稀土元素富集、Nb-Ta不亏损,与典型洋岛玄武岩(OIB)的微量元素分布模式和特征元素比值(Nb/La=1.24～1.48,Th/Ta=1.19～1.40)类似,但与典型OIB相对亏损高场强元素(如Th、Nb)不同,且在大地构造环境判别图上落入板内大陆玄武岩区,反映了化隆群斜长角闪岩原岩来源于软流圈地幔交代大陆岩石圈地幔熔融源区,为Rodinia超大陆在新元古代汇聚过程中局部裂解或Rodinia大陆整体上汇聚未完成局部地区就开始裂解的产物。Petrologic characteristics and analyses of major and trace elements of the amphibolites in Hualong Group within the eastern segment of Middle Qilian massif are reported in this paper.The amphibolites consist mainly of amphibole （52%） and plagioclase （40%）,with the accessory minerals comprising ilmenite （6%）,aprtite （2%）,quartz and sphene.In the rocks,SiO2=43.78%～48.09 %,TiO2=2.26%～2.5%,Al2O3=14.99%～16.64%,P2O5=0.38%～0.43%,CaO=8.11%～10.93%,FeOt=11.83%～12.54%,and Mg#=0.53～0.54.The amphibolites in Hualong Group crop out in layers,and their protoliths are alkalic basalts characterized by significant LREE[（La/Yb）cn=4.3～8.3）] and HFSE （e.g.,Nb,Ta） enrichment （Nb/La=1.2～1.5,Th/Ta=1.2～1.4） and insignificant Eu anomalies （Eu/Eu=0.90～1.11,with an average of 1.04 ）,as well as trace element patterns similar to those of ocean island basalts.Various geochemical diagrams indicate that these amphibolites mainly formed in an intraplate environment.Compared with OIB,amphibolites have slightly lower LILE （e.g.,Th） concentrations,implying an effect of asthenosphere-lithosphere interactions.The formation of the amphibolites was probably related to the partial breakup of the Neoproterozoic Rodinia Supercontinent in the Qilianshan region or the breakup of Neoproterozoic Rodinia Supercontinent in part of the Qilianshan region.

关 键 词：地球化学 岩石成因 斜长角闪岩 化隆群 中祁连 

分 类 号：P588.3[天文地球—岩石学] P595[天文地球—地质学]