Assimilation and prolonged suspension of crust-derived sulfide liquid in komatiites are essential to form Ni-rich mineralisation. Evaluating the spatial relationship between komatiite-hosted Ni mineralisation and crustal S sources may thus provide insights into mechanisms of transport, metal enrichment and deposition of assimilated sulfide liquid. This study applied facies analysis and S isotopes to sulfides in Ni-mineralised komatiites and stratigraphically underlying bimodal volcanic-volcaniclastic and sedimentary rocks, which formed during rifting in the Agnew-Wiluna Greenstone Belt, Western Australia. The results revealed a lateral variation from rift-distal sedimentary sulfides, through sulfidic BIF, to rift-proximal VMS-style sulfides, the latter of which was predominantly assimilated by komatiites. Both crustal and komatiite-hosted sulfides were overprinted by granite-related skarn alteration during later basin inversion. Spatial S isotopes correlation revealed that Ni mineralisation in komatiites predominantly formed < 5 km from their crustal S sources, excluding long lateral transport as the main metal enrichment mechanism. Rather, metal enrichment likely happened through multiple cycles of sulfide entrapment and entrainment in lava flow vortices that formed in the wake of topographic steps represented by syn-rift faults. These faults were the main loci for pre-existing crustal weaknesses, hydrothermal fluid circulation, and VMS-style sulfide deposition, which were subsequently utilised by komatiites for enhanced thermo-mechanical erosion and crustal sulfide assimilation. This study shows that proximity to the syn-rift faults was the dominant control on the formation of komatiite-hosted Ni–sulfide mineralisation, regardless of substrate lithology. The S isotope signatures of crustal sulfides may be used as a proxy to identify syn-rift faults in highly deformed terranes.

科马提岩中地壳衍生的硫化物液体的同化和长期悬浮对于形成富镍矿化至关重要。因此，评估科马提岩镍矿化与地壳硫源之间的空间关系可以为同化硫化物液体的迁移、金属富集和沉积机制提供见解。这项研究将相分析和硫同位素应用于镍矿化科马提岩中的硫化物以及地层下的双峰火山-火山碎屑岩和沉积岩，这些岩石是在西澳大利亚阿格纽-威卢纳绿岩带裂谷过程中形成的。结果揭示了从裂谷远端沉积硫化物到硫化物 BIF 到裂谷近端 VMS 型硫化物的横向变化，后者主要被科马提岩同化。在后来的盆地反转过程中，地壳和科马提岩中的硫化物都被花岗岩相关的夕卡岩蚀变所覆盖。空间硫同位素对比表明，科马提岩中的镍矿化主要形成于距离地壳硫源<5公里的地方，不包括长侧向迁移作为主要金属富集机制。相反，金属富集可能是通过在以同裂谷断层为代表的地形台阶之后形成的熔岩流涡流中硫化物截留和夹带的多个循环而发生的。这些断层是预先存在的地壳弱点、热液循环和VMS型硫化物沉积的主要场所，随后被科马提岩利用来增强热机械侵蚀和地壳硫化物同化。这项研究表明，无论基底岩性如何，靠近同裂谷断层是科马提岩镍硫化物矿化形成的主要控制因素。地壳硫化物的硫同位素特征可用作识别高度变形地体中同裂谷断层的代理。