Pd-Pt Fractionation: Hydrothermal or magmatic processes; Lac des Îles complex in Ontario, Canada

Tafadzwa Gomwe, Ph.D. thesis.

Ph.D. thesis in mineral ressources under the supervision of Dr. Sarah-Jane Barnes.

Project description

Lac Des Îles Complex is a mafic-ultramafic intrusion of Archaean age host to significant Pd and Pt deposit. The ore is unusual in that the ratio between Pd and Pt is exceptionally high (averaging 10), and in some ore types as high as 23. Mantle derived magmas have ratios between 1 and 3 and it is expected that in a closed system weighted Pd/Pt total ratio of a cumulate rock assemblage should remain around these values, for example the Pd/Pt ratio within the Merensky Reef of the Bushveld Complex and the J-M reef of the Stillwater complex are 0.68 and 3.64 respectively. Magmatic processes alone cannot account for the fractionation of Pd from Pt. The pegmatitic rock types, the lack of correlation between S and Pd or Pt and the presence of hydrous silicate minerals have been interpreted as indicative of PGE mobility. Low temperature experimental data available shows that mobility of PGE by fluid to create an ore deposit such as the Lac Des Îles Complex is very unlikely. Formation of insoluble Pt-alloys and the subsequent transport of Pd in a fluid form part of two models that have been applied to the Bushveld Complex in an attempt to explain Pd and Pt fractionation. This project will contain a petrographic study and geochemical analysis of rocks from both the high grade ore and low grade ore zones, to bring new insight as to the fractionation of Pd from Pt and the possible role of fluid in the ore-forming processes of the LDIC.


Papers, talks and other

Gomwe, T.E.S. 2004. Comparaison des élements du groupe du platine des zones Roby et Twilight, Complexe du Lac des Îles, Nord-ouest Ontario. Montreal, Québec. Premières journées De Launay.

Maier, W.D., Gomwe, T.E.S., Barnes, S.-J. and Theart, H., 2004. Platinum Group elements in the Uitkomst Complex: Economic Geology 99: 499-516


Question or commentary contact me: tgomwe@uqac.ca.