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Postgraduate Students

Mr Robert Knight

PhD Title: Magmatic concentration and secondary redistribution of platinum-group elements in Ni-Cu-deposits

Supervisors: Dr Hazel M. Prichard and Dr Iain McDonald

Nickel and copper ores in mafic and ultramafic igneous complexes host platinum-group elements (PGE). There is much controversy about the magmatic conditions that cause the PGE to fractionate into different base metal sulphides (BMS) and/or form early crystallising platinum-group minerals (PGM). The mobility of PGE during shearing, alteration and weathering of these ores is poorly understood, especially variation in individual PGE mobility during weathering.
The aims of this PhD are to (i) determine what controls PGE fractionation in different BMS (principally pyrrhotite, pentlandite and chalcopyrite) and (ii) understand how individual PGE remobilise during different alteration stages. Three examples of PGE-enriched base metal sulphide deposits, all currently being exploited, have been chosen for comparative study including: (i) Forrestania, a greenstone belt in the arid part of western Australia where both magmatic and remobilised ores are preserved, (ii) Mirabela in Bahia Brazil, a region of tropical rain fall, where undeformed magmatic Ni and Cu sulphides are overlain by deeply weathered laterites and (iii) Jinchuan in the Gobi desert, China, where magmatic ores are variably hydrothermally altered.
Using the scanning electron microscope (SEM) combined with laser ablation-ICP-MS it is possible not only to identify PGM within the ores but also to detect PGE in different BMS down to ppb. It is therefore possible to map the total distribution of the PGE within these ores which in turn allows the magmatic partition of PGE into different BMS and their mobility during alteration to be comprehensively analysed.