Strontium isotope stratigraphy of the Platreef: a tool for correlation with the rest of the Bushveld Igneous Complex

Strontium isotope stratigraphy throughout the Eastern and Western Limbs of the Bushveld Igneous Complex (BIC) shows a significant shift across the Merensky Reef near the top of the Critical Zone. However, in the Northern Limb, the strontium isotope stratigraphy is incomplete. Available data through the Main Zone of the Northern Limb show similar isotopic stages as the Eastern and Western Limbs, but there are no data through the Critical Zone. Such data are needed for correlation with the rest of the BIC, and in particular to assess whether the Platreef (which has been interpreted by some to be the stratigraphic equivalent of the Merensky Reef) also displays a large isotopic shift. The goal of this study is to expand the strontium isotopic profile of the Northern Limb by analysing a suite of samples collected through the transition between the Main Zone and the Critical Zone (including the Platreef). Anorthite content in plagioclase is a promising proxy as it shows a marked shift at the base of the Platreef.