准确测定镁铁-超镁铁质岩体ppt级铂族元素含量判断铜镍硫化物成矿潜力  

Determination of Platinum-group Element Concentrations in Mafic-ultramafic Intrusions with ppt Level for the Metallogenetic Potentials of Nickel-copper Sulfides

作　　者：任明浩 王伯林 黄肖潇 赵贵章 REN Minghao;WANG Bolin;HUANG Xiaoxiao;ZHAO Guizhang(College of Geosciences and Engineering,North China University of Water Resources and Electric Power,Zhengzhou 450046,China)

机构地区：[1]华北水利水电大学地球科学与工程学院,河南郑州450046

出　　处：《华北水利水电大学学报（自然科学版）》2022年第2期69-76,94,共9页Journal of North China University of Water Resources and Electric Power：Natural Science Edition

基　　金：国家自然科学基金青年项目(41803033,41903034);河南省高校重点科研计划项目(19A170009);华北水利水电大学高层次人才资助项目(20171003)。

摘　　要：岩浆型铜镍硫化物矿床一般都赋存在镁铁-超镁铁质岩体中。镁铁-超镁铁质岩体中岩石的铂族元素(PGE)含量和配分型式是判断岩体含矿性的重要指标之一,准确测定岩石的PGE含量对指导找矿具有重要意义。以东天山大草滩地区铜镍硫化物矿床远景区的一号和二号镁铁-超镁铁质岩体为研究对象,分别利用锍试金预富集常规法和锍试金预富集-同位素稀释法测定了两个岩体岩石中的PGE含量,在此基础上,探讨岩石的PGE含量差异对于岩体含矿性判断的影响。结果表明:锍试金预富集-同位素稀释法能够更准确地反映样品的PGE特征;大草滩一、二号岩体并没有表现出明显的Pt正异常,个别样品中Pt与Pd的含量比值(Pt/Pd)高于地幔值,指示其地幔源区可能并未经历显著的流体交代变质作用;二号岩体的橄榄岩样品的Os、Ir、Ru(IPGE)含量显著高于辉长岩,指示在岩浆分离结晶过程中,硫化物饱和发生得较晚,IPGE进入了早期结晶的橄榄石和铬铁矿中。未被流体交代的岩浆源区以及硫化物饱和发生在岩浆演化过程的较晚阶段,均不利于形成具有经济价值的铜镍硫化物矿床。因此,大草滩一、二号岩体可能不具备较好的成矿潜力。The Ni-Cu-(PGE)sulfide deposits are usually hosted in mafic-ultramafic intrusions.The concentrations and patterns of platinum-group element(PGE)are important indicators for mineralization potentials.Therefore,the accurate determination of PGE content of rock is of great significance to guide the mineral prospecting.Taking the No.1 and No.2 mafic ultramafic rocks in the prospect area of copper nickel sulfide deposit in Dacaotan area of Eastern Tianshan as the research object,the PGE concentrations in the two rocks are determined by sulfide fire assay preconcentration-isotope dilution and traditional sulfide fire assay preconcentration method respectively.On this basis,the influence of PGE content difference of rock on the judgment of ore bearing property of rock mass is discussed.The results are as follows.Compared with traditional sulfide fire assay preconcentration,sulfide fire assay preconcentration-isotope dilution is a better method to determinate PGE content in mafic-ultramafic intrusions with ppt level.The absence of positive Pt anomaly and the rare appearances of high Pt/Pd ratios indicate that the mantle source of the No.1 and No.2 intrusions in the Dacaotan area is not modified by subduction fluids.The higher concentrations of Os,Ir and Ru(IPGE)in peridotite than that in gabbro in No.2 intrusion indicates that the sulfide saturation occurred late in magma evolution process.Most of IPGE were concentrated in the earlier olivine and chromite rather than the later sulfide.Due to the unmetamorphic mantle source and late sulfide saturation,there is little chance to find economic Ni-Cu-(PGE)sulfide deposits in the two intrusions in the Dacaotan area.

关 键 词：锍试金预富集-同位素稀释法 锍试金预富集常规法 镁铁-超镁铁质岩体 铂族元素 成矿潜力 

分 类 号：P595[天文地球—地球化学]