内蒙古边家大院铅锌银矿床花岗斑岩及辉石闪长岩特征及对成矿的指示  

Characteristics and metallogenic significance of granite porphyry and pyroxene diorite in the Bianjiadayuan Pb-Zn-Ag polymetallic deposit,Inner Mongolia

作　　者：蒋昊原 赵志丹[5] 祝新友[4] 杨尚松 蒋斌斌[4] 杨朝磊 茅椿伟 JIANG Haoyuan;ZHAO Zhidan;ZHU Xinyou;YANG Shangsong;JIANG Binbin;YANG Chaolei;MAO Chunwei(Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;Key Laboratory of Petroleum Resources,Gansu Province/Key Laboratory of Petroleum Resources Research,Institute of Gelogy and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;University of Chinese Academy of Sciences,Beijing 100049 China;Beijing Institute of Geology for Mineral Resources,Beijing 100012,China;China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国科学院西北生态环境研究院,甘肃兰州730000 [2]甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室,甘肃兰州730000 [3]中国科学院大学,北京100049 [4]北京矿产地质研究院,北京100012 [5]中国地质大学(北京),北京100083

出　　处：《中国地质》2020年第2期450-471,共22页Geology in China

基　　金：国家重点研发计划课题(2017YFC0602403);中国地质调查局项目(DD20160072);国家自然科学基金(41602098)联合资助。

摘　　要：边家大院铅锌银矿床位于中亚造山带东段,属于大兴安岭主峰锡、铅、锌、铜成矿带。通过对边家大院矿区中花岗斑岩和辉石闪长岩进行LA-ICP-MS锆石U-Pb定年、主量元素、微量元素和钠长石电子探针分析,结果表明花岗斑岩与辉石闪长岩锆石U-Pb年龄分别为(138.2±0.8)Ma、(137.4±0.7)Ma,为早白垩世岩浆活动的产物。辉石闪长岩SiO2含量为50.99%~52.89%,CaO含量为7.47%~7.51%,MgO含量为3.64%~4.68%,全碱Na2O+K2O含量为4.91%~5.36%,位于高钾钙碱性系列与钙碱性系列交界线上;花岗斑岩具有晶洞构造、镜下鉴定显示长石全部为碱性长石,新鲜无矿化的花岗斑岩高硅(SiO2=70.34%~74.49%)、富碱(Na2O+K2O=4.83%~9.42%)、A/CNK值为1.13~2.40,属于过铝质花岗岩、贫钙(CaO=0.16%~1.04%),属于高钾钙碱性-钾玄岩系列,稀土元素配分图显示轻稀土富集,具强烈的Eu负异常(δEu=0.12~0.32),富集大离子亲石元素Rb、Th、U、K,明显亏损高场强元素Ta、Nb、P、Ti和过渡元素Sr、Ba等,钠长石An(0.03~4.64)远小于10,显示无矿化花岗斑岩具有高演化的A2型造山后碱长花岗岩特征,推断花岗斑岩岩浆来源于地壳,形成于张性环境中。结合地质特征和前人研究成果,认为边家大院花岗斑岩为成矿地质体,矿区西部深处仍有较大成矿潜力。Located in the southern section of the CAOB(Central Asian Orogenic Belt), the Bianjiadayuan Pb-Zn-Ag polymetallic deposit belongs to the Sn-Cu-Zn-Pb metallogenic belt of Da Hinggan Mountains. In this study, a series of analyses, such as LAICP-MS zircon U-Pb isotopic dating, major element and trace elements testing and electron microprobe analysis of albite, were performed for the granite porphyry and augite diorite. The results show that the age of granite porphyry and pyroxene diorite are ca.138 Ma and ca.137 Ma respectively, indicating that the intrusive rocks are products of the magmatic activities in the Early Cretaceous. The pyroxene diorite belongs to high K calc-alkaline series and calc-alkaline series with SiO2(50.99%-52.89%), CaO(7.4% 7-7.51%), MgO(3.64%-4.68%), and alkali(Na2 O + K2 O) 4.91%-5.36%. Granitic porphyry with miarolitic structure and microscopic identification shows that feldspar is all alkaline feldspar. Non-mineralized granite porphyry is characterized by high SiO2(50.99%-52.89%), alkali(Na2 O+K2 O=4.83%-9.42%), A/CNK(1.13-2.40), LREE enrichment, strong negative Eu anomalies(δEu=0.12-0.32), enrichment of LILE such as Rb, Th, U and K, depletion of HFSE such as Ta, Nb, P and Ti and transition elements such as Sr and Ba. According to the electron microprobe analyses, the An values of the albite in granite porphyry are by far lower than 10(0.03-4.64). These features are similar to the features of typical highly evolved A2 post-orogenic alkali feldspar granite pluton, suggesting that the magma was derived from the lithospheric mantle and formed in the tensional setting. Combined with the geological characteristics and previous research results, the authors hold hat the metallogenic geological body of the Bianjiadayuan area is the granite porphyry pluton, and there is still a great potential for mineralization in the deep part of western mining area.

关 键 词：铅锌银矿床 锆石U-PB测年 燕山期 矿产勘查工程 边家大院 林西 内蒙古 

分 类 号：P597[天文地球—地球化学] P618.42[天文地球—地质学]