东天山路北铜镍钴硫化物矿床铂族元素地球化学特征及意义

Platinum-group Elements Geochemistry and Its Significances of Lubei Cu-Ni-Co Sulfide Deposit in eastern Tianshan,NW China

新发现的路北铜镍钴硫化物矿床位于东天山黄山-镜儿泉铜镍矿带西段,探明的镍金属量6.8×10^(4)t(平均品位0.88%),铜3.9×10^(4)t(平均品位0.50%),钴2317 t(平均品位0.03%),矿床规模已达中型。路北岩体位于康古尔大断裂北侧,侵位于下石炭统小热泉子组凝灰质碎屑岩中,由早至晚依次为辉长岩、橄榄岩、辉石橄榄岩、橄榄辉石岩和闪长岩,其中橄榄辉石岩为最重要的含矿岩石。路北镁铁质岩石的铂族元素(PGE)含量偏低,ΣPGE为3.21×10^(-9)~45.13×10^(-9),平均14.96×10^(-9),IPGE(Os,Ir,Ru)略高于PPGE(Ru,Pt,Pd)含量。在原始地幔标准化图解上,岩石具相似的分布模式,PPGE和IPGE之间分异很弱。综合分析认为,形成路北铜镍钴矿床的母岩浆性质为后造山伸展环境下具交代岩石圈地幔特征的高镁玄武质岩浆,发生硫化物熔离的主要机制是下地壳物质的加入。

The newly discovered Lubei Cu-Ni-Co sulfide deposit located at the western section of Huangshan-Jingerquan copper nickel belt in eastern Tianshan.The proved nickel metal amount is 68000 tons(with average grade of 0.88%),copper 39000 tons(with average grade of 0.50%),cobalt 2317 tons(with average grade of 0.03%),and the deposit scale has reached medium type.The Lubei intrusion located at the north side of Kanggur fault and intruded in tuffaceous clastic rocks of Xiaorequanzi formation of Lower Carboniferous.From early to late,it is consisted of gabbro,peridotite,pyroxenite and diorite,among which olivine pyroxenite is the most important ore bearing rock.The content of PGE in mafic rocks of Lubei Cu-Ni-Co deposit is relatively low,withΣPGE ranging from 3.82×10^(-9)~5.36×10^(-9),with an average of 4.53×10^(-9).IPGE(Os,Ir,Ru)is slightly higher than that of PPGE(Ru,Pt,Pd).On the normalized diagram of the primitive mantle,the rocks have similar distribution patterns,and the differentiation between PPGE and IPGE is very weak.Comprehensive analysis shows that the parent magma of Lubei Cu-Ni-Co deposit is high Mg basaltic magma derive from metasomatic lithospheric mantle in post orogenic extensional environment,and the main mechanism of sulfide segregation is the addition of lower crust materials.