A Nd, Os, Pb and Sr Isotopic Study of the Dufek Intrusion, Pensacola Mountains, Antarctica: Re-assessment of Differentiation Mechanisms in Layered Mafic Complexes

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This award supports an isotopic study of the Dufek layered ultramafic intrusion. The objectives of the research are a better understanding of igneous processes in large mafic magma chambers, an accurate determination of the age of the Dufek intrusion, and an assessment of the origin of sulfide and chromite mineralization in the intrusion. The Dufek intrusion is part of the Karoo-Ferrar tholeiitic province, one of the largest such provinces known on Earth. This research will involve high precision mass spectrometric analysis of neodymium, strontium, lead, and osmium isotopes from ultrapure fractions of minerals separated from rock samples. These analyses will be used to trace compositional changes of both the liquid and cumulus (solid) phases during crystallization and crystal segregation processes. Lead and osmium isotopes will be used to tracers to ascertain whether sulfide mineralization resulted from increased silica activity associated with crustal contamination or whether sulfide mineralization was caused only by changes of temperature and oxygen fugacity. This research will help to elucidate processes of magma differentiation and mineralization associated with large ultramafic intrusions in general. Such intrusions are important sources of platinum group elements.