内蒙古敖汉旗七家金矿闪长玢岩锆石U-Pb年代学、地球化学及地质意义  

Zircon U-Pb geochronology, geochemistry and geological significance of diorite porphyrites in Qijia gold deposit, Aohan in Inner Mongolia

作　　者：王一珅 刘建明[1] 刘红涛[1] 褚少雄[1] 高帅[1,2] 陈永安 许腾[4] 武宗林 高玉友[5] 

机构地区：[1]中国科学院地质与地球物理研究所、矿产资源研究重点实验室,北京100029 [2]中国科学院大学,北京100049 [3]敖汉旗龙武矿业有限责任公司,内蒙古赤峰024313 [4]中国地质大学(北京),北京100083 [5]核工业243大队,内蒙古赤峰024006

出　　处：《地质科学》2016年第2期633-653,共21页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划“973”项目（编号：2013CB429804）和赤峰市人民政府和敖汉旗人民政府项目资助;致谢敖汉旗龙武矿业有限责任公司和敖汉旗国土资源局在本次野外工作中给予我们热情的协助.中国科学院地质与地球物理研究所曾庆栋研究员对本文提出了宝贵的修改意见.匿名审稿人为本文提出了建设性的修改意见和建议,对本文质量的提升起到了重要作用.笔者在此对上述单位和个人表示衷心感谢!

摘　　要：内蒙古敖汉旗七家金矿构造位置上处于兴蒙造山带与华北克拉通北缘的结合部位，靠近兴蒙造山带一侧，是近年来新发现的石英脉型金矿床。区内岩脉以闪长玢岩为主，且与石英脉型矿体空间关系密切。根据岩脉与矿体的穿插关系，将其分为成矿前闪长玢岩和成矿后闪长玢岩。LA—ICP-MS锆石U-Pb年代学表明，成矿前闪长玢岩加权平均年龄为166．3±3．4Ma，成矿后闪长玢岩加权平均年龄为128．6±4．5Ma，与区域上两期构造一岩浆活动时间（分别为160Ma左右和128Ma左右）近似吻合。主量元素特征显示：二者均属于准铝质，高钾钙碱性系列；微量元素特征显示：二者均富集轻稀土元素、大离子亲石元素（Rb、K）和活泼的不相容元素（U、Pb），相对亏损重稀土元素和高场强元素（Nb、Ta、Ti），反映出岩浆来源具壳源特征。主微量元素特征均显示出二者具有岛弧岩浆岩的地球化学属性。另外，成矿后闪长玢岩有较高的Nb／Ta（18．66—20．27）和Zr／Hf（37．16～39．23）比值，暗示其岩浆来源具明显的幔源特征。岩石地球化学特征表明，成矿前闪长玢岩可能起源于太平洋板块俯冲导致的下地壳部分熔融岩浆；成矿后闪长玢岩可能起源于俯冲流体交代的地幔楔熔融岩浆，并在其演化侵位过程中伴有地壳物质的混染。结合闪长玢岩成岩时代、岩石成因及区域构造演化，反映出七家金矿的形成与太平洋板块的西向俯冲密切相关，矿床在地壳由挤压增厚向伸展减薄的转换过程中形成。Qijia gold deposit, which is quartz-vein type gold deposit discovered recently, is located in the binding site between the North China Craton and the Xingmeng orogenic belt. It is near the side of Xingmeng orogenic belt. Diorite porphyrites, which are closely related to quartz-vein type orebody in space, are mainly occurred in this area. According to the interspersed relationship between dykes and orebody, it will be divided into pre-mineralization and post- mineralization diorite porphyrites. LA-ICP-MS zircon U-Pb geochronology shows that the weighted average age of the pre-mineralization diorite porphyrites is 166. 3±3.4 Ma, while the weighted average age of the post-mineralization diorite porphyrites is 128.6±4.5 Ma. The results approximately coincide with the two tectonic-magmatic activity time（ respectively around about 160 Ma and 128 Ma） of this area. Characteristics of the major elements show that both ofthem belong peraluminous and high-K calc-alkaline series. Characteristics of the trace elements show that both of them are enriched in LREE, LILEs （Rb and K）and lively incompatible elements（U and Pb）, while they are relatively depleted in HREE and HFSEs（ Nb, Ta and Ti）. These all reflect that the characteristic of the magma source is crustal source. All of the characteristics indicate that both of them have geochemical affinity of arc magmas. In addition, post-mineralization diorite porphyrites have high Nb/Ta （ 18.66 - 20.27 ） and Zr/Hf（ 37. 1-6 39.23） ratio, which suggests obviously that the magma source is mantle origin. Geochemical characteristics indicate that pre-mineralization diorite porphyrites magma may originate from partical melting of the lower crust caused by the Pacific plate subduction and post- mineralization diorite porphyrites magma may be derived from melting of mantle wedge metasomatized by subduction fluid, accompanied with contamination of crustal material in the process of emplacement. The diagenetic age, petrogenesis of diorite porphyrites, combined with r

关 键 词：七家金矿 闪长玢岩 岩石成因 成矿动力学背景 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]