Fig. 4: Evolution of magma composition throughout the eruption compared to past eruptions.
From: Magmatic volatiles control the sub-plinian basaltic eruptions at Ambae volcano, Vanuatu
A Lava and tephra bulk composition obtained in this work (Supplementary Table 2) are plotted (in red) for comparison with the past results of Warden (1970)86, Gordon (1974; 1977)87,88, Eggins (1993)89 and Sorbadere et al. 90. Melt inclusion results (from ref. 20) show a wide range of composition from basaltic trachy-andesite to basalt. The bulk rock and tephra composition from the 2017–2018 show a transition from basaltic andesite and trachy-basalt to basalt compositions. EDP1 corresponds to the onset eruption phase the produces material with relatively high silica content, whilst phase 4 corresponds to the final eruption phase. Phase 2 and phase 3 correspond to intermediate eruption phases. B The Harker diagrams of Ambae samples showing a strong olivine control on the past data87 contrasting with a relatively restricted MgO content in this work. The CaO content is lower than the past data, while the K2O and Na2O are higher, suggesting a relatively evolved source compared to results from past studies86,88,89,90. Of the two series defined from the TiO2 content in the past works88, only the low-TiO2 series is obtained in this work. The trace element concentrations normalized to N-MORB91 indicate a typical subduction arc source. Results are from bulk rock analyses.
