Where are all the PGEs in the Where are all the PGEs in the Platreef? Platreef? The use of Laser Ablation ICP-MS The use of Laser Ablation ICP-MS in revealing trace element in revealing trace element mineralogy mineralogy David Holwell David Holwell 1,2 1,2 and Iain McDonald and Iain McDonald 1 1 School of Earth, Ocean and Planetary Sciences, Cardiff School of Earth, Ocean and Planetary Sciences, Cardiff University, University, Main Building, Park Place, Cardiff, CF10 3YE, UK. Main Building, Park Place, Cardiff, CF10 3YE, UK. 2 SRK Exploration Services Ltd, 16 Park Grove, Cardiff, CF10 3BN, SRK Exploration Services Ltd, 16 Park Grove, Cardiff, CF10 3BN, UK. UK. [email protected][email protected]
Where are all the PGEs in the Platreef? The use of Laser Ablation ICP-MS in revealing trace element mineralogy. David Holwell 1,2 and Iain McDonald 1 1 School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE, UK. - PowerPoint PPT Presentation
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Where are all the PGEs in the Where are all the PGEs in the Platreef?Platreef?
The use of Laser Ablation ICP-MS in The use of Laser Ablation ICP-MS in revealing trace element revealing trace element
mineralogymineralogy
David HolwellDavid Holwell1,21,2 and Iain McDonald and Iain McDonald11
11School of Earth, Ocean and Planetary Sciences, Cardiff University,School of Earth, Ocean and Planetary Sciences, Cardiff University,
Main Building, Park Place, Cardiff, CF10 3YE, UK.Main Building, Park Place, Cardiff, CF10 3YE, UK.22SRK Exploration Services Ltd, 16 Park Grove, Cardiff, CF10 3BN, UK.SRK Exploration Services Ltd, 16 Park Grove, Cardiff, CF10 3BN, UK.
PGE in BMSPGE in BMS• This study has revealed that in the typical magmatic sulphide assemblage of pyrrhotite, pentlandite and chalcopyrite in the Platreef:
• Pyrrhotite hosts Os, Ir and Ru in solid solution
• Pendlandite hosts Rh and Pd, with some Os, Ir, Ru in ss
• Chalcopyrite hosts no appreciable PGE
• No phases contain Pt in ss, but all contain PGM microinclusions, commonly Pt-Bi phases
• Or:
• Pt occurs as PGM microinclusions and as PGM
• Pd occurs mainly as PGM, but also within pentlandite
• Rh occurs mainly in ss in pentlandite, occasionally as PGM
• Os, Ir and Ru very rarely occur as PGM and are concentrated in ss in pyrrhotite and pentlandite
Chalcopyrite:
no PGE in ss
Pentlandite:
Pd and Rh in ss, some Os, Ir, Ru
Pyrrhotite:
Os, Ir and Ru in ss
Pt only present as discreet PGM
Pt and some Pd PGM present around BMS margins
‘‘Primary’ mineralizationPrimary’ mineralization
•Fractionated polyphase blebs of sulfide
•Formed directly from the in situ fractional crystallization of a PGE-rich sulfide liquid
ConclusionsConclusions
• Pentlandite and pyrrhotite hold virtually all the bulk Os, Ir, Ru and Rh in the Platreef sulfides and formed from the cooling and crystallization of a PGE rich sulfide liquid.
• Some Pd is also locked up in solid solution in pentlandite
• Chalcopyrite contains no PGE
• Pt and Au do not occur in solid solution within sulfides and form discreet PGM (or electrum).
• ‘Primary’ assemblages are present throughout the Platreef pyroxenites, however, they may be altered by hydrothermal activity…