Olivine trace element geochemistry of volcanics from central and southern Africa

Olivines from mantle derived igneous rocks, specifically kimberlites from the Kalahari craton and alkaline to ultrapotassic mafic volcanics from the western branch of the East African Rift System from two distinct volcanic fields of Toro-Ankole and Virunga, were analysed by LA-ICP- MS to determine their minor and trace element concentrations. 

Olivine trace element geochemistry has gained increasing attention over the last decade as even though olivine has a limited ability to uptake trace elements early crystallization gives it the ability to record the most primitive unaltered compositions of the melt. These minor and trace element characteristics are compared to the growing range of olivine datasets sourced from a range of tectonic environments as to ascertain clues to the composition and conditions of the mantle source of these melts. 

A crustal component is inferred to be present in leucite basanites and potassic trachybasalts from the Virunga field due to the elevated Li concentrations in olivine (9.48 ppm), well above the mantle average of 3 ppm. Elevated V/Sc in one of the ugandites from Toro-Ankole is caused by a phlogopite component in the source, and not variation in oxygen fugacity.