Abstract
New mineral chemistry and wholerock geochemistry of type kamafugites from the East African Toro-Ankole province are compared with Italian and Brazilian kamafugitic rocks showing the diversity of kamafugite compositions. Whereas Brazilian kamafugites are more akin to the Ugandan type rocks in showing a smooth convex -upward trace element abundance curve and similarities in the mineral chemistry, significant chemical differences to the Italian rocks are apparent. The latter are characterized by higher SiO2, Al 2O3 and K2O contents and show negative anomalies for Eu and the high-field strength elements in normalized abundance patterns. This could be due to slightly distinct source compositions as a result of the different nature of mantle metas omatism preceding kamafugite magmatism. Whereas the Ugandan and Brazilian sub continental lithosphere was affected by metasomatizing agents derived from the asthenosphere the lithospheric mantle beneath Italy was probably affected by enrichment processes linked with subducted crust.
| Original language | English |
|---|---|
| Pages (from-to) | 51-77 |
| Number of pages | 27 |
| Journal | Periodico di Mineralogia |
| Volume | 72 |
| Issue number | SPEC. ISSUE 1 |
| Publication status | Published - 2003 |
| Externally published | Yes |
Keywords
- Geochemistry
- Kalsilite
- Melilite
- Rift magnwtism
- Toro-Ankole
- Ultrapotassic rocks