Figure 4.

(a) Diversity of melt inclusion trace element composition plotted as a function of the composition of the olivine host (Fo%). Plot adapted from [43] with data from Laki [52]. The data are aggregated from 10 eruptions, and the general pattern of reduced variability at lower host forsterite content is recapitulated within the products of individual eruptions, most notably Borgarhraun. The mean deviation is close to zero, highlighting the strong and systematic relationship between the trace element composition of the olivine-hosted melt inclusions from a given eruption and the composition of the carrier liquid. (b) Variation in the mixing parameter, M, quantifying the mixing process. The grey boxes show the results of petrological barometry for different eruptions. Vigourous mixing of compositional heterogeneity in mantle melts takes place in the lower crust. (Online version in colour.)