0000000000273377
AUTHOR
Geoff Nowell
L’origine des chevaux du site du Mormont (canton deVaud, Suisse) : l’apport des isotopes de carbone, d’oxygène et de strontium
International audience
Petrogenesis of strongly alkaline primitive volcanic rocks at the propagating tip of the western branch of the East African Rift
Abstract Strongly silica-undersaturated potassic lavas (kamafugites) and carbonatitic tuffs are characteristic of the Toro-Ankole volcanic field in southwestern Uganda, forming the youngest and most northward volcanics of the western branch of the East African Rift. Lavas contain exceptionally low SiO2 (31.8–42.8 wt.%), high CaO (up to 16.6 wt.%) and K2O (up to 7 wt.%). They exhibit moderately enriched correlated Nd (eNd − 0.1 to − 4.7) and Hf (eHf − 0.1 to − 8.8) isotope signatures, indicating time-integrated enrichment in incompatible elements in the source, attributed to mixing between two metasomatic assemblages, a phlogopite-rich MARID-type and a later carbonate-rich assemblage. The re…