澳大利亚伊尔岗克拉通科马提岩型镍矿成矿作用及找矿方法

    Mineralization and prospecting method of the komatiite-related nickel deposits in the Yilgarn craton, Australia

    • 摘要: 澳大利亚西部伊尔岗克拉通卡尔古利地体是世界上太古宙与科马提岩有关的硫化物镍矿床最为集中的地区。该区科马提岩型硫化镍矿床主要有两大类型:①由高品位的块状、海面陨铁状和网状矿石组成,赋存于科马提岩熔岩流(主要为火山橄榄岩)底部,以卡姆巴尔达矿床为代表;②以低品位的浸染状镍硫化物矿石为主,赋存于厚层纯橄榄岩的中部,以芒特基斯为代表。与镍成矿有关的科马提岩形成于晚太古代(2.70Ga),具铝不亏损(Al2O3/TiO2=15~25)地球化学特征,一般形成于具含硫围岩的动态高岩浆流环境。伊尔岗克拉通科马提岩型镍硫化物矿床形成于经历岩浆作用(结晶、分异和浓集)和地壳硫混染作用的硫不饱和镁铁质—超镁铁质岩浆的熔岩通道或管道中。在矿床成因讨论的基础上,提出该类型矿床的找矿标志和勘查方法。

       

      Abstract: The Kalgoorlie terrane of the Yilgarn craton in West Australia is a unique area in the world where Ni sulfides deposits in Archean komatiites are extremely abundant. Komatiite-hosted Ni sulfide deposits in the Kalgoorlie terrane have been classified into two types: ①deposits consisting of high-grade massive and matrix or net-textured ores on the bottom of komatiite lava flows composed of volcanic peridotites, represented by the Kambalda deposit; ②disseminated nickel sulfides within central zones of thick dunitic bodies, represented by the Mt. Keith deposit. The fertile komatiitic sequences are generally late Archean (2.70Ga) in age, have dominantly Al-undepleted (Al2O3/TiO2=15~25) chemical affinities, and often occur with sulfur-bearing country rocks in dynamic high-magma-flux environments, such as compound sheet flows with internal pathways facies (Kambalda-type) or dunitic compound sheet flow facies (Mt Keith-type). The nickel sulfide deposits were formed in dynamic lava channels or magma conduits by sulfur-undersaturated mafic-ultramafic magmas through magmatic processes (crystallization, differentiation and concentration) and assimilation of crustal sulfur. Based on the discussion on the genesis of the ore deposit, the authors put forward the prospecting criteria and exploration methods for this type of ore deposits.

       

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