Contamination of the Bushveld Complex (South Africa) magmas by basinal brines: Stable isotopes in phlogopite from the UG2 chromitite

Abstract There is abundant evidence for significant H2O in evolved melts from the platinum-rich UG2 chromitite and Merensky Reef of Bushveld Complex (South Africa), but there no consensus about source H2O. We report triple-oxygen hydrogen isotope ratios interstitial, late-magmatic phlogopite three localities layer. The yielded δD values −43 to −23, which >30 higher than previously known rocks far above mantle ~−75. are first be reported rocks, with Δ′17O0.5305 (17O excess relative reference line 0.5305) –0.069 –0.044 (δ18O 5.2–6.2). oxygen data support existing models as much 30%–40% contamination mantle-derived magmas lower middle crust. However, high require a second step contamination, we attribute brines marine sediments Transvaal Basin at emplacement level.