A chilled margin of komatiite and Mg-rich basaltic andesite in the western Bushveld Complex, South Africa

Abstract

and the elevated Sr and S isotopic signatures of the rocks. However, in order to account for the high Pt and Pd contents of the magma, the mantle must have been twice as rich in PGE as the current estimate for PUM, possibly due to a component of incompletely equilibrated late veneer.

The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa: trace element geochemistry, Nd isotopes and high-precision geochronology

“…Based on similarities between the composition of the Uitkomst chilled margins and the high-magnesian andesitic Bushveld B1 magmas, Gauert et al (1995) Yudovskaya et al 2015;Maier et al 2016). The Uitkomst intrusion data are modelled here in terms of prospective mixtures of mantle-derived magma (either a LREE-depleted asthenospheric mantle or an enriched, source-contaminated mantle) and Meso-to Neoarchaean crust consistent with the host rocks to the intrusion (Fig.…”

“…Because the trace element patterns of the Uitkomst and Bushveld cumulates show good overlap with upper crust (Maier et al 2000;Barnes et al 2010;Maier et al 2016) the latter model is favoured here. Additional contamination of the magnesian andesitic parent melt by a small amount (<5-15%) of roof-or wall-sedimentary rocks occurred during final emplacement.…”

“…However, comparison between Bushveld and Uitkomst provides some clues. Maier et al (2016) identified a komatiitic quenched rock in a chilled margin sequence of the Western Bushveld and proposed that the Bushveld B1 magmas were derived largely from the asthenosphere, followed by variable amounts of contamination with upper crust. As Uitkomst and Bushveld show good overlap in εNd and incompatible trace element ratios, we argue that the Uitkomst magma is equally derived from the asthenosphere, followed by contamination with sub-Transvaal Supergroup crustal rocks.…”

Microtextural characterisation of the Lower Zone in the western limb of the Bushveld Complex, South Africa: evidence for extensive melt migration within a sill complex

“…More recent studies by Wilson (2012) and Maier et al (2016a) concluded that the most likely parental magma to the LZ would have been a komatiitic one with 18-19 wt% MgO derived from the asthenosphere, which assimilated some continental crust.…”

“…Per peridotite, Px pyroxenite, No norite, ol olivine, opx orthopyroxene, oth other minerals at the base of the LZ, consisting of a ca. 90-cm-thick chill sequence comprising Mg-rich basaltic andesite and komatiite (Maier et al 2016a). This is overlain by a ca.…”