贺兰山大战场印支期埃达克型花岗岩及地质意义  

GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL SIGNIFICANCE OF INDO-CHINESE EPOCH IN HELAN MOUNTAIN

作　　者：黄喜峰[1] 钱壮志[1] 白生明 吴文奎[1] 陆彦俊 王成 

机构地区：[1]长安大学资源学院,长安大学成矿作用及动力学国土资源部重点实验室,陕西西安710054 [2]宁夏地质环境监测总站,宁夏银川750021

出　　处：《新疆地质》2010年第3期323-329,共7页Xinjiang Geology

基　　金：国家重点基础研究发展计划(973计划)项目“多种能源矿产共存成藏(矿)机理与富集分布规律”(2003CB214600);1∶25银川幅区域地质大调查(J48C002003)项目资助

摘　　要：大战场花岗岩岩体位于贺兰山中南段,属钙碱性系列,具岛弧花岗岩特征.岩石地球化学分析结果表明,这些岩石富Na2O、贫K2O、Na2O/K2O比值为0.73~1.41,SiO2含量大于56%,Al2O3含量为15.32%~17.23%,多数大于15%,MgO含量均小于3%,低Y和Yb,Sr的含量高,Sr/Y 25.98~97.15,大于20~40.稀土元素含量较低,为47.58×10-6~70.29×10-6,轻重稀土分馏不明显,呈弱的Eu正异常,大离子亲石元素（Rb,Ba,Th,Sr）相对富集,高场强元素（Nb,Ta,Hf）相对亏损.在岩石地球化学特征上,大战场花岗岩类似于C型埃达克质岩石,岩浆产生于增厚地壳物质的部分熔融,表明该花岗岩类可能属埃达克质岩.该套埃达克岩的厘定,对研究贺兰山构造带中生代构造演化、地球动力学特征具重要意义.The granite body of Dazhanchang is located at the middle south section of Helan Mountain,belonging to calc-alkaline series and having the characteristics of island-arc granite.Analyses of rock geochemistry show that the rock is rich in Na2O（2.34%~5.00%）and poor in K2O（3.20%~4.30%）and that the value of Na2O/K2O is from 0.73 to 1.41,the content of SiO2 is larger than 56%,the content of Al2O3 vary between 15.32 and 17.23and most are larger than 15%,and the content of MgO is lower than 3%（0.5%~1.04%）,with low content of Y（from 3.25×10-6 to 13.10×10-6 lower than 18×10-6） and Yb（from 0.47×10-6 to 1.25×10-6 lower than 1.9×10-6）,with high content of Sr larger than 376×10-6 except two samples.The value of Sr/Y is between 25.98 and 97.15 larger than 20-40 and the content of rare earth elements is relatively lower and is from 47.58×10-6 to 70.29×10-6 showing weak fractionation,without Eu anomaly or having weak positive Eu anomaly.Rb,Ba,Th and Sr of the large-ion lithophile elements are enrichment relatively and Nb,Ta and Hf of high field strength elements are relatively depleted.Characteristics of rock geochemistry of Dazhanchang granity is similar to C type adakitic rocks.Magmas were generated by partial melting of thickened crust material,which shows that the granitoid at Indo-Chinese epoch may belong to adakitic rocks.The definition of the series of adakitic rocks has important significance for studying tectonic evolution and geodynamic characteristics in Mesozoic Era in the structural belt of Helan mountain.

关 键 词：贺兰山 埃达克质岩 大战场花岗岩体 地球化学特征 地质意义 

分 类 号：P588.121[天文地球—岩石学]