Abstract Magmatic Ni-Cu-platinum group element (PGE) deposits are commonly located in tectonically active regions that typically undergo significant deformation and metamorphism and subsequent reworking of sulfide. The Munali Ni deposit is hosted by a dynamic intrusive mafic-ultramafic system situated within the Zambezi belt in southern Zambia. The deposit comprises Fe-Ni–dominant magmatic sulfides, present as a number of lenticular massive sulfide bodies that display a variety of magmatic and metamorphic sulfide textures. The sulfide lenses are uniformly deficient in iridium subgroup PGEs (IPGEs), Au, and Cu, with unusual but characteristically high bulk Ni/Cu ratios (~10) and a consistent precious metal mineral assemblage dominated by Pd and Pt tellurides. On a centimeter to meter scale, Cu tenors and Ni/Cu ratios are extremely variable (Ni/Cu between 0.1 and 71.5), while Ni and Pd tenors are consistent, indicative of the high mobility and variable concentrations of Cu sulfide within the deposit. Sulfur isotope signatures of the ore sulfides (δ34S ~6‰; Δ33S ~0‰) indicate a local crustal S contaminant from host marbles yet display S/Se ratios suggestive of a postmagmatic overprint. The consistent geochemical similarities of the bulk sulfide throughout the complex and the absence of primary silicate-sulfide textures suggest that the Munali ores were not sourced from a parental magma directly represented by units within the complex. Instead, it is suggested that the sulfide liquid was introduced from elsewhere in the magmatic system during the later stages of the emplacement of the complex. Fractional crystallization of the sulfide liquid during emplacement resulted in the primary segregation of a Cu-rich residual liquid that migrated away from the bulk of the Fe-Ni sulfide, accounting for the high bulk Ni/Cu ratio, with the potential for the accumulation of a separate and thus far undiscovered Cu orebody. In addition, intense deformation during the Pan-African orogeny and interaction with hydrothermal fluids have locally overprinted some of the primary magmatic textures, resulting in localized sulfide mobilization and the extreme variations of Ni/Cu ratio between sulfide samples. Munali therefore represents a complex dynamic deposit showcasing a variety of mechanisms for sulfide fractionation of an Ni-Cu-PGE orebody by both syn- and postmagmatic processes.

中文翻译：

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岩浆硫化物的流动和分馏：赞比亚 Munali Ni-（Cu-Platinum 族元素）矿床的就位和变形

摘要 岩浆镍铜铂族元素 (PGE) 矿床通常位于构造活动区，通常会经历显着的变形和变质作用以及随后的硫化物再加工。Munali Ni 矿床位于赞比亚南部赞比西带内的动态侵入镁铁质-超镁铁质系统中。该矿床包含以铁镍为主的岩浆硫化物，以许多透镜状块状硫化物体的形式存在，显示出各种岩浆和变质硫化物结构。硫化物透镜普遍缺乏铱亚组 PGE (IPGE)、Au 和 Cu，具有不寻常但特征性的高块体 Ni/Cu 比 (~10) 和以 Pd 和 Pt 碲化物为主的一致贵金属矿物组合。在厘米到米的范围内，Cu 含量和 Ni/Cu 比率变化很大（Ni/Cu 介于 0.1 和 71.5 之间），而 Ni 和 Pd 含量是一致的，表明沉积物中 Cu 硫化物的高迁移率和可变浓度。矿石硫化物的硫同位素特征（δ34S ~6‰；Δ33S ~0‰）表明来自宿主大理石的局部地壳 S 污染物，但显示的 S/Se 比率表明存在后岩浆叠印。整个复合体中块状硫化物的一致地球化学相似性以及原始硅酸盐-硫化物结构的缺失表明，Munali 矿石并非来自复合体中单元直接代表的母岩浆。相反，有人认为硫化物液体是在复合体就位的后期从岩浆系统的其他地方引入的。就位过程中硫化物液体的分级结晶导致富铜残留液体的一次偏析，该残留液体从 Fe-Ni 硫化物的主体中迁移出来，占高的体积 Ni/Cu 比，有可能积累一个单独的、迄今为止未被发现的铜矿体。此外，泛非造山运动过程中的强烈变形以及与热液的相互作用使一些原始岩浆结构局部叠印，导致硫化物的局部流动和硫化物样品之间镍/铜比的极端变化。因此，Munali 代表了一个复杂的动态矿床，展示了通过同岩浆过程和岩浆后过程对 Ni-Cu-PGE 矿体进行硫化物分馏的各种机制。