塔里木板块东北缘坡七侵入体金属硫化物矿物学特征及成矿指示作用

Mineralogical Characteristics and Indicative Significance of the Poqi Intrusion in the Northeastern Margin of Tarim Plate

坡七侵入体位于新疆塔里木板块东北缘,是坡北岩体第三期次岩浆作用的产物。该侵入体主要的岩石类型有二辉橄榄岩、橄榄辉石岩、方辉辉石岩、橄长岩、苏长岩、辉长岩以及辉长闪长岩。橄榄岩相和苏长岩相中赋存铜镍硫化物矿(化)体,矿石构造类型有浸染状、稠密浸染状和块状。金属硫化物主要为磁黄铁矿、镍黄铁矿、黄铜矿和黄铁矿,金属矿物生成顺序为:铬尖晶石-(第1世代镍黄铁矿Pn^1、第1世代黄铜矿Ccp^1)-NC型磁黄铁矿-(第2世代镍黄铁矿Pn^2、4C型磁黄铁矿、第2世代黄铜矿Ccp^2、第1世代黄铁矿Py^1)-第3世代镍黄铁矿Pn^3-(第2世代黄铁矿Py^2、第3世代黄铜矿Ccp^3)。其中,磁黄铁矿、镍黄铁矿矿物学特征表明,岩(矿)体侵位过程中,高温阶段温度下降缓慢,低温阶段温度下降较快,晚期有热液作用叠加。成矿期可以划分为岩浆成矿期(岩浆熔离阶段和单硫化物固溶体分异阶段)及热液成矿期。依据矿石结构构造、金属矿物矿物学特征综合分析,坡七侵入体深部硫化物熔离充分,成矿潜力大。

The Poqi marie -ultramarie intrusion, located in the northeastern margin of the Tarim plate, was formed during the third stage of the Pobei magmatism. This intrusion mainly includes harzburgite, olivine pyroxenolite, pyroxenite, olivine gabbro, norite, gabbro and gabbro - diorite, and the peridotite phase and norite phase contain copper - nickel ore bodies. The ores mainly display disseminated, dense disseminated and massive structures. The dominant sulfide minerals are pyrrhotite, pentlandite, chalcopyrite, and pyrite, and their crystallization consequence follows by chromite - （ the first generation pentlandite （Pn1 ） and chaleopyrite （Cep1） ） - pyrrhntite （NC） - （the second generation pentlandite （Pn2） and ehaleopyrite（ Ccp2） , pyr- rhotite （4C） , the first generation pyrite （pyl） ） _ the third generation pentlandite（ Pn3） - （the third generation chaleopyrite（ Cop3） , the second genera- tion pyrite （py2））. The mineral characteristics of pyrrhotite and pentlandite indicate that during the intrusion emplacement, the temperature dropped slowly in high temperature stage and quickly in low temperature stage, and the intrusion underwent hydrothermal process after emplacement. The metallo- genie period can be divided into magmatie metallogenie stage and hydrothermal mineralization stage. Comprehensive analysis based on ore textures and structures, sulfide minerals characteristics and temperature environment during sulfide saturation shows that the process of sulfide segregation in the Poqi intrusion is conducive to form magmatie Ni - Cu deposits.