内蒙古额仁陶勒盖银矿区火成岩岩石地球化学特征及锆石SHRIMP U-Pb同位素定年  

Geochemical characteristics and zircon U-Pb SHRIMP age of igneous rocks in Erentaolegai silver deposit,Inner Mongolia

作　　者：许立权[1] 刘翠[2] 邓晋福[2] 李宁[2] 戴蒙[2] 白立兵[1] 

机构地区：[1]内蒙古自治区地质调查院,呼和浩特010020 [2]中国地质大学,北京100083

出　　处：《岩石学报》2014年第11期3203-3212,共10页Acta Petrologica Sinica

基　　金：中国地质调查局项目(1212011121075;1212010911028;12120114020901;1212011220921;1212011121266);国家重点基础研究发展计划(973计划)项目(2011CB808901);科学技术部国际科技合作计划项目(2010DFB23390)联合资助

摘　　要：通过对额仁陶勒盖银矿区的塔木兰沟组中酸性火山岩详细的岩石地球化学特征研究表明,该套火山岩具高硅（Si O2〉57%）、高铝（Al2O3〉16%）、富碱尤其富钾（K2O〉3%）特征,属HKCA系列;稀土含量中等（187×10^-6~240×10^-6）,（La/Yb）N在18.6~27.9,Yb〈1.90×10^-6,Y〈18.0×10^-6,δEu=0.85~0.96,轻重稀土分馏强烈,明显亏损重稀土,无或略具负铕异常;微量元素相对富集Rb、Ba、Th、U、K等大离子亲石元素（LILE）,亏损高场强元素Nb、Ta、Ti、HREE,与活动陆缘火成岩的微量元素特征一致。塔木兰沟组安山质火山岩特征表明,安山质岩浆来源较深（〉50km）,起源于加厚地壳底部,源区残留为石榴石、单斜辉石及角闪石,岩浆在部分熔融及后期演化过程中不曾与斜长石平衡过,可能是蒙古-鄂霍茨克洋闭合后进入碰撞后松弛阶段,钙碱性或高钾钙碱性的中基性变火成岩的部分熔融形成。对与额仁陶勒盖银矿关系密切的石英斑岩（脉）测年,获得SHRIMP U-Pb年龄138.6±2.3Ma,为石英斑岩的成岩年龄,进一步限定该银矿床形成于早白垩世早期。对塔木兰沟组安山岩与石英斑岩成岩年龄、矿床成矿特征等方面进行探讨了,认为该银矿床为岩浆热液成因。Through the study of petrology and geochemistry,the volcanic rocks of Tamulangou Formation in Erentaolegai silver deposit have the characteristics of high Si O2（ 〉 57%）,Al2O3（ 〉 16%）,alkali especially K2O（ 〉 3%） and belong to HKCA series.The content of REE is medium（ 187 × 10^- 6~ 240 × 10^- 6）,（ La/Yb）Nratio is from 18. 6 to 27. 9,Yb values are less than 1. 90 ×10^- 6,Y values are less than 18. 0 × 10^- 6,and δEu is from 0. 85 to 0. 96. REE fractionation is strong,apparently loss of heavy rare earth and No or slightly negative Eu anomaly. Trace element is relative enrichment of LILE such as Rb,Ba,Th,U,K,loss of HFSE such as Nb,Ta,Ti,HREE,and similar to the characteristics of active continental margin. The characteristics of andesitic volcanic rocks in Tamulangou Formation indicate the andesitic magma comes from the base of the thickened crust（ 〉 50km）,the residues are garnet,clinopyroxene and amphibole,partial melting and later evolution process of magma are not equilibrium with plagioclase.Andesitic volcanic rocks in Tamulangou Formation are the partial melting of CA or HKCA metamorphic Okhotsk Ocean. SHRIMP zircon U-Pb age of quartz porphyry,which was considered close with Erentaolegai silver deposit,is 138. 6 ± 2. 3Ma and is the digenetic age.So further restrict Erentaolegai silver deposit formed at early stage of Early Cretaceous. Through the comparison between quartz porphyry and Tamulangou volcanic rocks from forming age and the study of characteristics of deposit,the silver deposit type is magmatic hydrothermal.

关 键 词：额仁陶勒盖银矿 塔木兰沟组火山岩 石英斑岩 岩石地球化学特征 SHRIMP U-Pb年龄 岩浆起源 构造背景 内蒙古 

分 类 号：P588.144[天文地球—岩石学] P597.3[天文地球—地质学]