Trace element concentrations in magnetite are dictated by the petrogenetic environment and by the physico-chemical conditions during magmatic, hydrothermal, or sedimentary processes. This makes magnetite chemistry a useful tool in the exploration of ore-forming processes. We describe magnetite compositions from Ni-Cu-(PGE)-sulfide mineralized rocks from seven mafic–ultramafic intrusions peripheral to the Mesoproterozoic AMCG (anorthosite-mangerite-charnockite-granite) suite of the Kunene Complex of Angola and Namibia to investigate metallogenic processes through the geochemical characterization of Fe-oxides, which were analyzed in-situ via Electron Probe Microanalysis (EPMA), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We identified magmatic magnetite, segregated from both a silicate liquid and an immiscible sulfide liquid. Elements like Cr, Co and V suggest that the sulfide-related magnetite segregated from a relatively primitive Fe-rich monosulfide solid solution (MSS). Secondary Cr-rich magnetite appears in intrusions with abundant chromite or Cr-spinel. Two types of hydrothermal magnetite were identified, related to the pervasive replacement of sulfides and a late-stage, low-T fluid circulation event. Magnetite replacing sulfides is associated with serpentinized ultramafic rocks and is preferentially observed in the intrusions with the highest base and precious metal tenors. The high concentration of Ni, Co, Cu, Pd, As and Sb in these grains is corroborated by the identification of micron-size PGE mineral inclusions. We infer that serpentinization during hydrothermal fluid circulation was accompanied by desulphurization of sulfides with metal remobilization and reconcentration to generate magnetite carrying Pd microinclusions. We suggest that the highly serpentinized ultramafic rocks in the Kunene Complex region may become a possible target for economic Ni-Cu-(PGE) mineralization.

磁铁矿中的微量元素浓度由成岩环境以及岩浆、热液或沉积过程中的物理化学条件决定。这使得磁铁矿化学成为探索成矿过程的有用工具。我们描述了来自安哥拉和纳米比亚库内内杂岩的中元古代 AMCG（斜长石-锰锰矿-辉绿岩-花岗岩）组周边七个镁铁质-超镁铁质侵入岩的镍-铜-(PGE)-硫化物矿化岩石的磁铁矿成分，以研究成矿过程铁氧化物的地球化学特征，通过电子探针微量分析 (EPMA) 和激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) 进行原位分析。我们鉴定出了岩浆磁铁矿，它与硅酸盐液体和不混溶的硫化物液体分离。 Cr、Co 和 V 等元素表明，与硫化物相关的磁铁矿是从相对原始的富铁单硫化物固溶体 (MSS) 中分离出来的。次生富铬磁铁矿出现在富含铬铁矿或铬尖晶石的岩体中。确定了两种类型的热液磁铁矿，与硫化物的普遍置换和后期低温度流体循环事件有关。取代硫化物的磁铁矿与蛇纹石化超镁铁岩有关，并且优先在具有最高基金属和贵金属品位的岩体中观察到。这些颗粒中含有高浓度的 Ni、Co、Cu、Pd、As 和 Sb，这通过微米级 PGE 矿物夹杂物的鉴定得到了证实。我们推断，热液循环过程中的蛇纹石化伴随着硫化物的脱硫以及金属的再活化和再富集，从而生成携带 Pd 微包裹体的磁铁矿。 我们认为库内内杂岩区高度蛇纹石化的超镁铁岩可能成为经济镍铜（铂族元素）矿化的可能目标。