Platinum-group elements in sills of the Jurassic Ferrar Large Igneous Province from Northern Victoria Land, Antarctica

Abstract

Platinum-group element (PGE) abundances were analysed in basaltic andesites and andesites from sills of the Ferrar Large Igneous Province in northern Victoria Land. The strongly fractionated primitive mantle-normalised PGE- patterns show enrichment of the Pt-PGE over the Ir-PGE. The single element abundances exhibit good correlations with the degree of differentiation of the distinctly evolved samples and are interpreted to result mainly from low-pressure in-situ differentiation after magma emplacement in the upper crust. Compared to tholeiitic rocks from other magmatic provinces, only the Ferrar rocks exhibit coupled enrichment of Pd, Pt and Cu even in most evolved samples. The decrease of Pt and Pd in some of the more evolved samples does not necessarily signify sulphide fractionation, but may indicate the formation of other PGE-compounds. The inferred sulphur-undersaturated conditions during differentiation are in agreement with the high degrees of partial melting as well as the refractory nature of the proposed subcontinental lithospheric mantle source beneath this magmatic province