西藏甲玛铜多金属矿含矿斑岩黑云母和角闪石矿物化学特征  

Mineral chemistry of biotite and hornblende of ore-bearing porphyry from the Jiama porphyry copper-polymetallic deposit

作　　者：张忠坤 陈国良 杨征坤 唐攀 高福太 焦海军 王志超 祁婧 吴纯能 ZHANG Zhong-kun;CHEN Guo-liang;YANG Zheng-kun;TANG Pan;GAO Fu-tai;JIAO Hai-jun;WANG Zhi-chao;QI Jing;WU Chun-neng(Huatailong Mining Development Co.Ltd.,Lhasa 850200,China;Faculty of Geosciences and Environmental Engineering,Southwest Jiaotong University,Chengdu 611756,China;School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China;School of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]西藏华泰龙矿业开发有限公司,西藏拉萨850200 [2]西南交通大学地球科学与环境工程学院,四川成都611756 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《岩石矿物学杂志》2020年第6期685-702,共18页Acta Petrologica et Mineralogica

基　　金：国家重点研发计划-深地专项(2018YFC0604101);中国地质科学院基本科研业务费专项经费项目(SYSCR2019-02);西藏自治区科技计划项目(XZ201901-GB-24);国家自然科学基金项目(41902097);中国地质调查局项目(DD20190167)。

摘　　要：甲玛超大型铜多金属矿床位于冈底斯成矿带东段,矿体主要包括矽卡岩型、斑岩型、角岩型和独立金矿体4种类型。矿床中酸性侵入体中广泛发育岩浆黑云母,部分岩体较发育角闪石。本文在全面开展矿区地质调查和详细的钻孔岩芯编录的基础上,对含矿二长花岗斑岩和含矿花岗闪长斑岩中的岩浆黑云母以及含矿花岗闪长斑岩中的角闪石开展了矿物学及矿物化学研究,以揭示其成岩成矿意义。研究结果表明,二长花岗斑岩和花岗闪长斑岩中的岩浆黑云母为镁质黑云母,具有富镁高钛、高铝低硅、富钾贫钠的特点。与花岗闪长斑岩相比,二长花岗斑岩中的岩浆黑云母具有较低的TiO2、FeOT、MgO、MnO、Na2O、BaO含量,较高的Al2O3和SiO2含量。花岗闪长斑岩中的角闪石属于阳起石,具有高硅低铝钛、富镁钙贫钠钾等特征。黑云母和角闪石温度计计算结果显示,含矿二长花岗斑岩中黑云母结晶温度为740.1~783.8℃,平均为762.4℃;含矿花岗闪长斑岩中黑云母结晶温度为750.3~766.9℃,平均为757.2℃;含矿花岗闪长斑岩中角闪石结晶温度为654.1~698.9℃,平均为680.3℃。黑云母和角闪石矿物化学特征指示,二长花岗斑岩和花岗闪长斑岩为造山带钙碱性岩系、Ⅰ型花岗岩,具有壳幔混源的特征。二长花岗斑岩和花岗闪长斑岩具有较高的氧逸度(NNO以上)及水含量,有利于铜、钼等成矿物质进入成矿流体中。The Jiama superlarge copper-polymetallic deposit is located in the eastern part of the Gangdise metallogenic belt,and mainly includes four types of orebodies: skarn orebody,porphyry orebody,hornfels orebody and independent gold orebody.There are extensive magmatic biotites in the intermediate acid intrusions of the deposit,and hornblende is more common in some intrusions.On the basis of comprehensive geological survey in the mining area and detailed drilling core cataloging,the authors studied mineralogy and mineral chemistry of magmatic biotite in ore-bearing monzogranite porphyry and ore-bearing granodiorite porphyry as well as hornblende in ore-bearing granodiorite porphyry so as to reveal its petrogenic and metallogenic significance.The results show that the magmatic biotite in monzogranite porphyry and granodiorite porphyry is Mg-biotite,which is characterized by higher MgO,TiO2,Al2O3,K2O contents,and lower SiO2,Na2O content.Compared with granodiorite porphyry,magmatic biotite in monzonitic granite porphyry has lower content of TiO2,FeOT,MgO,Mn O,Na2 O,BaO,and higher content of Al2O3,SiO2.Hornblende in granodiorite porphyry belongs to actinolite,which is characterized by higher SiO2,MgO and CaO content,and lower Al2O3,TiO2,Na2O and K2O content.Biotite and hornblende thermometers show that the crystallization temperature of biotite in ore-bearing monzogranite porphyry is 740.1~783.8℃,with an average of 762.4℃,that of biotite in ore-bearing granodiorite porphyry is 750.3~766.9℃,with an average of 757.2℃,and that of hornblende in ore-bearing granodiorite porphyry is 654.1~698.9℃,with an average of 680.3℃.The mineral chemical characteristics of biotite and hornblende indicate that monzogranite porphyry and granodiorite porphyry are calc-alkaline series and I-type granite in the orogenic belt,which has the characteristics of crust-mantle mixed source.Monzogranite porphyry and granodiorite porphyry had higher oxygen fugacity(above NNO) and formed water-rich magmas,which was beneficial for the entry of

关 键 词：角闪石 黑云母 矿物化学特征 甲玛 西藏 

分 类 号：P578.955[天文地球—矿物学] P578.959[天文地球—地质学]