岩浆铜-镍-铂族元素硫化矿床“深部熔离-贯入”成矿作用与模式——加拿大伏伊希湾和中国金川矿床地质特征对比

    Deep segregation-injection ore-forming process and metallogenetic model for magmatic Cu-Ni (PGE) sulfide deposits—Geological comparative study on two deposits exemplified by Voisey`s Bay (Canada) and Jinchuan (China)

    • 摘要: 通过对金川铜镍矿床地质、矿化特征与加拿大伏伊希湾(Voisey’s Bay)铜-镍-铂族元素硫化物矿床进行系统对比分析,总结出这2个世界级铜镍硫化物矿床形成演化方面的相似性、可比性及其共同特点,即深部岩浆房含矿岩浆沿通道脉动式上侵,到上部表现为“小岩体,成大矿”。成矿作用过程和模式表现为:①含矿岩浆的有序侵位显示岩浆在深部岩浆房停歇过程中曾发生熔离分异,形成岩浆、含矿岩浆、富矿岩浆和矿浆分层结构;②成矿作用是在富有动力的岩浆环境下岩浆不连续(脉动式)上侵过程中发生的,岩浆熔融体富含挥发组分,上侵活动剧烈,围岩角砾化;③含矿岩浆沿相同的通道或越位上侵,在先期侵入岩体下侧或上方不同空间成矿;④岩浆运移过程中与围岩发生相互作用、组分交换和成矿物质的富集。深入阐明了含矿岩浆不连续(脉动式)上侵、后续岩浆补给和混合是镁铁—超镁铁岩体中硫化物被聚集在岩浆流动的通道内形成超大型铜镍硫化物型铂族元素矿床的重要机制。

       

      Abstract: In this paper, geological and mineralization characteristics and metallogenetic model of Jinchuan Cu-Ni (PGE) magmatic sulfide deposit are systematically analysed and compared with Voisey`s Bay Cu-Ni (PGE) deposit (Canada), and the results show that the two world-class Cu-Ni (PGE) deposits have some common geological characteristics, and so, there are similarity and comparability on ore-forming and evaluation of the deposit. That means ore bearing magma at depth pulsating invasion along the magma flow conduit results in a large deposit in upper magmatic room which appears it was generated from a small rock mass. Several key aspects of the characteristics on ore-forming process and metallogenetic model emerged as follows: i) ore-bearing magma pulsating invasion in sequence reveals that segregation and differentiation has occurred during primitive magma staying at a lower magmatic room and resulted in layering structure of magma , ore-bearing magma, sulfide-enriched magma and sulfide mass ; ii)ore forming process occurs in a dynamic magma flow during pulsating invasion, melted magma mass contains volatile composition, acutely invasion results in brecciated wall rocks; iii) ore bearing magma invades along the same conduit or overpass to access to the bottom or upper part of the previous invasions to form ore body; ⅳ) magma interacts with wall rocks , exchanges some components and enrich metallogenetic materials during transportation .It is clarified that ore-bearing magma pulsating invasion and subsequent magma re-supply to be a very important ore-forming mechanism through which sulfide-bearing mafic-ultramafic magma assembles along the magma flowing conduit at depth to form super-larger Cu-Ni (PGE) magmatic sulfide deposits during the process of Magmatic Ni-Cu sulfide deposits forming by “injecting of sulfide-bearing magma segregated at depth”.

       

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