Chemical fractionation in titaniferous clinopyroxene from Bayuda, Sudan
Chemical fractionation in titaniferous clinopyroxene from Bayuda, Sudan
The Canadian Mineralogist (December 1988) 26, Part 4: 1027-1035
- Africa
- alkaline earth metals
- aluminum
- basanite
- chain silicates
- chemical fractionation
- clinopyroxene
- East Africa
- enrichment
- fugacity
- igneous rocks
- iron
- magnesium
- metals
- metamorphism
- mineral composition
- mineralogy
- minerals
- petrography
- petrology
- pyroxene group
- silicates
- silicon
- Sudan
- titanium
- volcanic rocks
- zoning
- Bayuda Desert
- northern Sudan
- titanugite
- Jebel Aiwaysh
Clinopyroxene in basanites and their late residual fractions from the Bayuda Desert, Sudan, shows initial trends of enrichment in Al and Ti accompanied by decline in Si and the Mg/Fe ratio. During the second stage of fractionation (confined to small volumes of residual magma), there was little variation in Mg/Fe, but a continued increase in Al and Ti led to peak values of >11 wt. % Al (sub 2) O (sub 3) and 6% TiO (sub 2) . Hourglass zonation is characteristic of this stage. A third and final stage is marked by a complete change, toward iron enrichment and lower levels of Al and Ti. Although the late residuals from which these pyroxenes crystallized were highly alkaline, there is only negligible increase in the aegirine component. Textures indicate that the third stage began abruptly, and the mineralogical variations seem to require an increase in ferric/ferrous ratio in the system at that point. [Author's abstract]