金川铜镍硫化物矿床1号矿体矿石成因研究
Ore Genesis of Ore Body #1 of the Jinchuan Ni-Cu Sulfide Deposit
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摘要: 金川Ni-Cu-(PGE)硫化物矿床赋存于超镁铁岩体中,是世界第三大镍矿床.金川岩体中部(1#矿体)Ni金属储量约占整个金川矿床的56.8%,岩石呈同心带状分布,矿体横剖面形态为舌状,中间为网状矿石,周围是浸染状矿石,其网状结构矿石丰度远远高于其他矿石类型.1#矿体不同类型矿石亲Cu元素100%硫化物计算后,原始地幔标准化配分模式指示矿石的IPGE具有、高低2个系列的数值特征,Pt变化很大,大部分样品Pt/(Pt+Pd)值在(0.3～0.7)范围之外.钻孔样品Ni、Cu品位的变化指示富Cu矿石富集于网状矿体中、下部,网状矿石的Ni、Cu品位呈明显的负相关关系,Ni/Cu值在深部变化较大.研究认为,1#矿体遭受热液蚀变作用影响明显,矿石IPGE的变化和小尺度的Ni/Cu值循环变化由MSS分离结晶作用所致,矿体中、下部富集富Cu矿石和深部Ni/Cu值变化较大由MSS分离结晶作用和热液蚀变作用综合所致.Abstract: The Jinchuan Ni-Cu-(PGE) sulfide deposit is hosted by ultramafic intrusions in northwestern China.It is the third-largest Ni deposit in the world.The central part of the Jinchuan intrusion(Ore Body 1) has a "tongue-like" shape in cross section and hosts～56.8% of the known Ni resources.It is characterized by concentrically zoned,with net-textured ore surrounded by disseminated sulfide.Net-textured ore is dominant over other ore types in ore body #1.Based on 100% sulfide recalculation,different types of ore in ore body #1 have high and low value characteristics of IPGE,and Pt vary largely,Pt/(Pt+Pd) ratios of most samples are out of (0.3-0.7).The Ni,Cu content variations of drill hole samples indicate that Cu-rich ores concentrated at base of net-texture ore body,and content of this two elements appears obvious negative relationships,Ni/Cu ratios vary largely in deep.This research reveals that the ore body #1 was affected obviously by hydrothermal alteration.IPGE and small scale variations of Ni/Cu ratios are likely due to fractional crystallization of MSS.Small Cu-PPGE rich lenses and large scale variations of Ni/Cu in the deep part of ore body #1 may be the result of MSS fractionation or hydrothermal alteration.
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