These volcanic rocks define two separate geochemical suites, one formed by the basanites-tephrites and the other by the alkali basalts-mugearites. The formation of these two magma suites has been explained with fractional crystallization processes, mixing between different magmas and partial melting. Geochemical patterns indicate that the source magmas of Vesteris have similar sources as the magmas involved in other volcanoes of the North Atlantic north of Iceland. Differences between volcanic rocks erupted earlier in the history of the volcano and more recent products may imply that magma chemistry changed over time.
