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Postgraduate Students

Ms Rhian Jones

PhD title: Micro-Analysis of Early Magmatic Sulphide Inclusions and Metallogenic Variation in the Platreef, Northern Bushveld Complex, South Africa.

Supervisors: I. McDonald, H.M. Prichard (Cardiff University), D.A. Holwell (Leicester University), I.B. Butler (Edinburgh University) and G. Chunnet (Anglo Platinum)

The 2.06 billion year old Bushveld Complex in South Africa is the world’s largest continental magma chamber and is the host for enormous resources of Fe, Cr, Ti, V and platinum-group elements (PGE). This project focuses on the Platreef - a highly complex Ni-Cu-PGE orebody in the northern limb of the Bushveld Complex. The Platreef displays large variations in mineralogy and chemistry that influence the metallurgical characteristics.

This study aims to rigorously test predictions arising from a new model for the Platreef developed by McDonald and Holwell where PGE-Ni-Cu-rich immiscible sulphide droplets were introduced by silicate magma flowing upwards from a deeper magma chamber. As magma emerged from the feeder and intruded laterally between the layers of sedimentary country rock this was assimilated and in some areas extra sulphur (and penalty elements like As and Sb) were added. These modified the sulphide droplets and led to the observed variations in metallurgical characteristics across the orebody.

Key predictions from the new model that will be tested include: (a) any evidence for early metal-rich sulphides; (b) whether any observed early sulphides are chemically different from later modified sulphides; and (c) in order to generate the metal-rich sulphide droplets the model infers the presence of early (pre-Platreef) magma chambers where silicate magma and sulphide droplets were mixed together and Ni, Cu and the PGE were extracted from the magma and concentrated in the sulphides. The project will test for the presence of rocks formed from these characteristically metal depleted magmas.