Figure 2.
(A) Post-glacial variation of magma temperature. Temperatures associated with 40Ar/39Ar or estimated eruption ages are determined by two-oxide thermometry (Ghiorso and Evans, 2008) while zircon 238U/230Th ages are associated with Ti-in-zircon temperatures (Ferry and Watson, 2007). (B). SiO2 content of Laguna del Maule lavas for the past 160 k.y.; note the different x-axis scale versus the other panels. Previously common mafic eruptions are rare and peripheral since the 19 ka Espejos eruption. (C) The cumulative volume of post-glacial silicic lava. Plotted data and rates are minimums because they do not account for tephra fall preserved in Argentina. (D–F) Trace element compositions of the post-glacial lavas display spatially independent, temporally coherent chemical evolution consistent with an integrated, relatively homogeneous source reservoir. Symbols are as listed in panel E. (G) Quenched basaltic andesite inclusion in the rhyodacite of Colada Dendriforme (rdcd). (H) 230Th/238U equiline plot of data from euhedral surfaces of zircon in Nieblas rhyolite pumice. The red 2 ka isochron corresponds to the estimated eruption age. Black 30 and 50 ka isochrons are for reference. Isochrons calculated using the whole-rock Nieblas rhyolite 238U/230Th composition.