金川铜镍矿床隐伏富铜矿体成因研究及其深部找矿意义

金川矿床赋存于富橄榄石超镁铁质岩中,是目前世界第三大在采铜镍硫化物矿床.经过多年开采,如何在深、边部找到新的替代资源问题显得越来越重要.通过对金川矿床富铜隐伏矿体的矿体特征、矿石特征和矿石特殊地球化学特性等方面进行分析研究,特别是从空间立体对其矿化规律进行总结,并与其附近Ⅱ1#主矿体进行对比,指出该类型矿体既有岩浆熔离作用的特点,又有后期改造作用的特征,其形成经历了三个阶段:富含Cu、PGE岩浆深部熔离-脉动贯入、构造活化富集和后期热液叠加.同时探讨了来源于地幔深部的高镁玄武质岩浆,在深部岩浆房和阶段岩浆房熔离分异过程中,富镍岩浆和矿浆之间存在富铜岩浆.此外,Pb同位素表明,该隐伏富铜矿体形成时间为8亿年左右,早于块状特富矿;Pb、S同位素表明,该矿体主要来源于地幔,但曾被少量地壳物质混入.最后指出铜镍硫化矿床的成因是复杂多样的,在金川矿床深边部寻找新型矿体,尤其是富铜矿体的前景很大,而F_6断层可能是富铜隐伏矿体岩浆通道和Ⅱ1#主矿体岩浆的深部侵位通道之一.

Study on genesis of the concealed Cu-rich ore body in the Jinchuan Cu-Ni deposit and its prospecting in depth

The Jinchuan deposit is hosted by the olivine-rich ultramafic rock-body, which is the third-largest being exploited magmatic sulfide Ni-Cu deposit in the world. After it has been exploited for about fifty years, the problem that seeking new relaying resources in its deep and border becomes more and more important. The characteristics of ore body, ore and geochemistry of concealed Cu-rich ore body are researched. Through spatially analyzing and comparing with neighboring Ⅱ1 main ore body, the mineralization-rule of concealed Cu-rich ore body is summed up. Meanwhile, it is implied that there may exist a Cu-rich magma between Ni-rich magma and ore-pulp during liquation-differentiation in deep stage-chambers, which derives from deep mantle high-MgO basahs magma. It is concluded that the ore body has the feature of both magmatic liquation and late reconstruction action; it has experienced three stages: first, deep-liquation and pulsatory-injection of the Cu- and PPGE-rich magma; second, concentration of tectonic activation; third, the later magma hydrothermal alteration. In addition, the data of Pb isotope shows the forming age of I6 Concealed Cu-rich ore body is about 800Ma, which is earlier than that of massive Ni-rich ore bodies; the Pb and S isotope indicate the magma of Ⅰ6 Concealed Cu-rich ore body originates predominantly from mantle, however it is interfused by minute crust material. Finally, it is inferred that the genesis of Cu-Ni sulfide deposit is complex, and the prospect of seeking new deep ore bodies in deep and border of Jinchuan Deposit is promising, especially seeking Cu-rich ore bodies; the F6 fault may be the emplacing conduit of I6 Concealed magma, and one of the emplacing conduits of Ⅱ1 magma.