Fig. 5: Plagioclase minor element compositions from Wolf and Fernandina.
From: Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago
Minor elements vs. An# of plagioclase crystals in lava and tephra samples from the 2015 Wolf eruption (blue squares), nodule samples from the 1968 Fernandina eruption (red diamonds) and lava samples from historic Fernandina eruptions (open diamonds). Crystal compositions from historic Fernandina lavas are from Allan and Simkin28. Characteristic 2σ analytical uncertainties for our plagioclase analyses are shown or are less than the size of a data point. The lines in (d) show the MgO contents of plagioclase crystals calculated to be in equilibrium with liquids containing 1, 2, 4, 6 and 8 wt% MgO (at appropriate temperatures from Wolf Rhyolite-MELTS models at 300 MPa; black dashed lines) and with the average 2015 Wolf tephra glass at 1160 °C (the approximate pre-eruptive crystallisation temperature; solid grey line)19, using the MgO partitioning model of Nielsen et al.43. Insets show the general theoretical trends of crystal compositions during growth (i.e. fractional crystallisation; solid lines) and diffusive re-equilibration (dashed lines), after Humphreys39.
