The Wedza–Mimosa platinum deposit, Great Dyke, Zimbabwe: layering and stratiform PGE mineralization in a narrow mafic magma chamber

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Abstract
The Wedza–Mimosa platinum deposit is a loosely stratiform PGE-rich sulphide zone (MSZ) set within a complexly layered, shallow synclinal sequence of pyroxenites and gabbros. Both the MSZ and its host rocks display systematic stratigraphic, lithological and compositional variations between the margins and the axis of the deposit. A well preserved marginal facies is characterized by discordant layering, stratigraphic complexity, evidence of non-equilibrium crystallization, magmatic erosion and extensive pegmatoids, as well as by irregular MSZ development and metal contents. The principal transverse variations and marginal phenomena are interpreted in terms of the high transverse heat flux and heat gradient caused by the narrow trumpet-like cross-sectional structure of the original magma chamber, the magma replenishment process, the angular relationship between the chamber floor and the stratified magma, and the increase in magma density caused by the onset of plagioclase crystallization.