牛苦头矿床矿石矿物标型特征及成因

The ore mineral typomorphic characteristics of minerals and its genetic significance in Niukutou deposit

牛苦头矽卡岩型铅锌矿床是祁漫塔格成矿带最重要的铅锌多金属矿床之一。前人对牛苦头矿床的成岩成矿年代学、成矿岩体性质、矽卡岩矿物成因、流体包裹体、成矿系统以及矿床成因进行了研究,但对于成矿类型与成矿环境存在不同的认识。牛苦头矿区中典型矿物(磁黄铁矿、黄铁矿、黄铜矿、磁铁矿、闪锌矿及方铅矿)电子探针分析结果表明,黄铁矿与磁黄铁矿均富Co贫Ni,且磁黄铁矿以单斜磁黄铁矿为主,磁黄铁矿多与黄铜矿共生,代表了一种中温特征的矿床;黄铜矿、闪锌矿与方铅矿硫含量较高,且闪锌矿以铁闪锌矿为主,Zn/Cd值较低,代表中高温矽卡岩型矿床成因;且早期磁铁矿较晚期磁铁矿更富集MnO、TiO_(2)、Al_(2)O_(3),均指示矽卡岩型以及岩浆热液型成因。综合各矿物标型特征认为,牛苦头铅锌矿床为具矽卡岩型和热液型特征的中温矿床。

Niukutou Pb-Zn skarn type deposit is one of the most important Pb-Zn polymetallic deposits in Qimantagh metallogenic belt.Predecessors have studied the metallogenic chronology,the nature of metallogenic rock mass,the genesis of skarn minerals,fluid inclusions,metallogenic system and deposit genesis of of Niukutou deposit,but they have different understandings of metallogenic type and environment.The EPMA results of pyr⁃rhotite,pyrite,chalcopyrite,magnetite,sphalerite and galena in Niukutou ore district show that both pyrite and pyrrhotite are rich in Co and poor in Ni,and pyrrhotite is dominated by monoclinic pyrrhotite.Pyrrhotite mostly coexists with chalcopyrite,representing a deposit with medium temperature characteristics;Chalcopyrite,sphalerite and galena have high sulfur content,and sphalerite is dominated by marmatite,with low Zn/Cd values,which represents the genesis of medium high temperature skarn type deposits;Moreover,the early magnetite is more enriched in MnO,TiO_(2)and Al_(2)O_(3) than the late magnetite,indicating the genesis of skarn type and magmatic hydrothermal type.According to the typomorphic characteristics of various minerals,Niukutou Pb-Zn deposit is a medium temperature deposit with skarn and hydrothermal characteristics.