黑龙江五星铜镍-铂钯矿矿床成因及地质意义

Genesis of Wuxing Cu-Ni-PGE deposit in Heilongjiang and its geological significance

五星铜镍-铂钯矿地球化学特征显示,岩体SiO_2含量较低(48.36%~52.68%),Al2O3(1.24%~14.8%)、Fe_2O^T_3(3.67%~11.31%)、CaO(6.63%~21.42%)、MgO(5.52%~19.15%)含量变化较大,各岩相m/f值范围为0.86~8.89,属铁质基性岩。Harker图解显示,五星岩体经历了以单斜辉石堆晶为主的分异作用,且大部分样品遭受了中-上地壳物质的混染。微量元素比值特征显示(La/Nb、La/Ba、Th/Yb、Ba/La、Nb/Yb及Th/Yb)五星岩体起源于亏损的地幔源区,通过自身的分异作用及上升过程中地壳物质的加入,使岩浆中硫达到过饱和状态,硫化物则以熔体形式携带金属元素从硅酸盐熔体中熔离出来,随着岩浆的不断上升,最终在地壳浅部就位成矿。

Geochemical analysis of Wuxing Cu--Ni--PGE deposit indicates that the rock samples have obvious characteristics of low content of SiO2（48.36% - 52.68%） and wide range of Al2O3（1.24% - 14.8%）,Fe2O3T（3.67% - 11.31%）,CaO（6.63% - 21.42%） and MgO（5.52% - 19.15%） with the m/f values range from0.86 to 8.89,falling into the range of ferrous mafic-ultramafic rocks.According to the Harker variation diagrams,Wuxing rocks originated from fractional crystallization dominated by diopside minerals,meanwhile,middle-upper crustal contamination occurred in the same process of the fractional crystallization.Geochemical characteristics of the trace elements show that the original magma came from depleted mantle source.Fractional crystallization and contamination from crustal materials are contribute to the saturation of sulphur element,and the sulfides carry with metal elements liquate from silicate melts in the form of melts.With the increase of magma the Wuxing deposit formed in shallow part of the crust finally.