摘要：

Compatible behaviour has been considered as a major influence on the behaviour of the platinum-group elements (PGE) in magmatic systems. The authors believe that current models tend to over-emphasize the crystal-chemical compatibilities of the PGE, and that the PGE cannot be modelled as partitioning into sulphides or chromite in the conventional chemical sense. Investigation of data from igneous rocks and ores from the Kaapvaal craton lead the authors to propose a model which relies on the well-documented siderophile nature of the PGE: the PGE might occur in magmas as metallic clusters of 50-100 atoms, rather than as cations or any molecular species. Such clusters could be stabilized by an outside 'envelope' of ligands (e.g. S. As, Sb, Te) and this might lead to their incorporation into a sulphide melt or chromite (if available); however, the association between the PGE clusters and the sulphide would be a mechanical rather than chemical one.Versoenbare gedrag word as 'n groot invloed op die gedrag van die platinumgroep elemente (PGE) in magmatiese stelsels beskou. Die outeurs is van mening dat huidige modelle neig om die kristal-chemiese versoenbaarhede van die PGE oor te beklemtoon, en dat die PGE nie as insluitsels in sulfiedes of chromiet in die gebruiklike chemiese sin gemodelleer kan word nie. Navorsing van die verspreiding van PGE in stollingsgesteentes en ertse van die Kaapvaalkraton het tot die voorstelling van 'n model, wat berus op die goed gedokumenteerde siderofiele aard van die PGE, gelei: die PGE mag as metaliese trosse van 50-100 atome, eerder as katione of enige molekulere spesie, voorkom. Sulke trosse kan deur 'n uiterlike omhulsel van ligande (bv. S, As, Sb, Te) gestabiliseer word en dit mag tot hulle inkorporering in 'n sulfiedsmelting of chromiet (indien beskikbaar) lei; die assosiasie tussen die PGE trosse en die sulfied sou egter meganies eerder as chemies wees.

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