煎茶岭硫化镍矿床矿石组分特征及其赋存状态

Ore composition and hosting condition in the Jianchaling sulfide nickel deposit, Shaanxi province

采用高精度的新一代 ICP MS分析技术,依据新的研究思路和方法,在详细分析研究煎茶岭硫化镍矿床矿石组分特征及其赋存状态的基础上,进一步探讨其成矿作用机制和成因类型。研究认为,煎茶岭硫化镍矿床矿石主要组分为Ni,Cu,Co,Fe,S,PGE等,其高的 Ni/Cu,低的 Cu,PGE含量值反映该矿床为高镁岩浆演化的产物。矿石可分为磁黄铁矿镍黄铁矿型和黄铁矿针镍矿辉镍矿型两类,并以前者为主,表明该矿床的形成至少经历了早期岩浆成矿和晚期热液变质改造成矿两个阶段,应属于岩浆熔离热液改造成因类型。矿石中的镍主要以镍黄铁矿、紫硫镍铁矿、针镍矿和辉镍矿等独立镍矿物存在;镍有3种赋存形式,以硫化镍为主,硅酸镍、硫酸镍少量。在煎茶岭超基性岩上升侵位过程中,随着岩浆的演化分异先于新元古代在岩体边缘或内部形成镍矿床,而后于印支—燕山期在岩体接触带形成金矿床,它们是在统一的与幔源超基性岩有关的成矿系统中形成的具内在成因联系的成矿系列。

On the basis of reserching in composition feature and existing phase of ores from the Jianchaling sulfide nickel deposit by means of new and high-precision ICP-MS analysis technique, its mechanism and type of metallogenesis is futher studied with new thoughts and methods. The main composition of ore in the Jianchaling sulfide nickel deposit includes Ni,Cu,Co,Fe,S,PGE, and so on, its high Ni/Cu value and lower content of Cu,PGE indicate that the formation of the nickel deposit resulted from the evolution of high-Mg magma. The nickel deposit has two typed ores, the pyrrhotite-pentlandite type and pyrite-millerite-polydymite type, and the first type is predominant, which proved that the formation of the nickel deposit at least experienced the former magmatic metallogensis and the later hydrothermal metamorphism reconstructed metallogensis two periods. Therefore, the deposit should be magma melt-hydrothermal reconstructed type. The nickel in ores exsist mostly by simple nickel minerals, such as pentlandite, violarite, millerite and polydymite, and its hosting condition is sulfide-, silisic-, and sulfate nickel three shapes. The first is dominant. During the intrusion process of the Jianchaling ultra-basic rock, the nickel deposit is formed inside or in the margin of rockbody in Neo-Proterozoic, and subsequently the gold deposit was formed in the contacting belt of rockbodies in the Indosinian-Yanshanian time companying the evolution and differentiation of magma. It is a metallogenic series that have inner genic relation in the uniform metallogenic system involved with mantle-sourced ultra-basic rock.