The geochemistry of titanomagnetite in magnetite layers and their host rocks of the eastern Bushveld Complex

摘要: More than 430 analyses of magnetite separates revealed pronounced differences in composition between from layers and disseminated the host rocks. Magnetite massive is among others enriched elements such as Ti, Mg, Al, Si, which suggests that this crystallized under conditions disequilibrium with magma, i.e., by spontaneous nucleation rapid crystallization. Lower vanadium values magnetites suggest crystallization at higher f (sub O 2 ) rocks containing magnetite.Variation diagrams reveal a cyclicity compositional trends upward sequence related to magma roof zone intrusion, periodic collapse crystal-laden its incorporation base chamber. Deviations normal trend are considered reflect stratification gradual stratified liquid into convecting magma. A increase Cr content tentatively ascribed combination olivine expense pyroxene upper subzones possible partition coefficient chromium spinel decrease temperature.