Copper-sulfides within carbonatites and phoscorites of the Phalaborwa Igneous Complex, South Africa, have been investigated since the middle of the 20th Century. However, aspects of ore formation have remained unclear. This study examines the mechanisms involved in Cu-sulfide mineralisation by micro-focus X-ray computed tomography as applied to sulfide-rich drill core samples. Several texturally distinct assemblages of magmatic sulfides can be identified, including: (1) <500 μm rounded bornite and chalcopyrite grains disseminated within the gangue; (2) elongated mm-scale assemblages of chalcopyrite and bornite; and (3) mm-to-cm thick chalcopyrite cumulates. Chalcopyrite veins were also observed, as well as late-stage valleriite, documenting late-stage fluid circulation within the pipe, and alteration of magmatic and hydrothermal sulfides along fractures within the gangue, respectively. The results of micro-focus X-ray computed tomography indicate that magmatic sulfides are sub-vertically aligned. Spatial variability of the sulfide assemblages suggests that textural changes within sulfide layers reflect fluctuating magma flow rate during emplacement of carbonatite–phoscorite magmas, through coalescence or breakup of sulfide liquid droplets during ascent. Modal sulfide abundances, especially for disseminated assemblages, differ from one carbonatite–phoscorite layer to another, suggesting a strong control of the mechanical sorting in the formation of Cu-sulfide textures within the Loolekop carbonatite. The alternation of carbonatite and phoscorite within the intrusion suggest that the Loolekop Pipe was emplaced through a series of successive magma pulses, which differentiated into carbonatite and phoscorite by melt immiscibility/progressive fractional crystallisation and pressure drop. Three-dimensional textural analysis represents an effective tool for the characterisation of magma flow and is useful for the understanding of magmatic processes controlling sulfide liquid-bearing phoscorite–carbonatite magmas.

碳酸盐和帕拉博鲁瓦火成岩复杂，南非phoscorites内铜的硫化物，已自20中旬调查日世纪。然而，矿石形成的各个方面仍不清楚。本研究通过应用于富含硫化物的钻芯样品的微焦点 X 射线计算机断层扫描检查铜硫化物矿化的机制。可以识别出几种结构不同的岩浆硫化物组合，包括： (1) <500 μm 圆形斑铜矿和黄铜矿颗粒散布在脉石内；(2) 细长的毫米级黄铜矿和斑铜矿组合；(3) 毫米到厘米厚的黄铜矿堆积。还观察到黄铜矿脉，以及后期的铅锌矿，记录了管道内的晚期流体循环，以及岩浆和热液硫化物沿脉石内裂缝的蚀变。微焦点 X 射线计算机断层扫描的结果表明，岩浆硫化物是亚垂直排列的。硫化物组合的空间变异性表明硫化物层内的结构变化反映了碳酸岩-亚磷铁矿岩浆侵位过程中岩浆流速的波动，通过上升过程中硫化物液滴的聚结或分解。模态硫化物丰度，特别是对于弥散组合，从一个碳酸盐-亚磷铁矿层到另一个不同，表明在 Loolekop 碳酸盐岩内形成 Cu-硫化物结构时，机械分选受到强烈控制。侵入体中碳酸岩和亚磷铁矿的交替表明 Loolekop Pipe 是通过一系列连续的岩浆脉冲进入的，通过熔体不混溶/渐进分步结晶和压降分化为碳酸岩和亚磷铁矿。三维结构分析是表征岩浆流的有效工具，有助于理解控制含硫化物液体的亚磷铁矿-碳酸岩岩浆的岩浆过程。