Petrological imaging of an active pluton beneath Cerro Uturuncu, Bolivia

Uturuncu is a dormant volcano in the Altiplano of SW Bolivia. A present day similar to 70 km diameter interferometric synthetic aperture radar (InSAR) anomaly roughly centred on Uturuncu's edifice is believed to be a result of magma intrusion into an active crustal pluton. Past activity at the volcano, spanning 0.89 to 0.27 Ma, is exclusively effusive and almost all lavas and domes are dacitic with phenocrysts of plagioclase, orthopyroxene, biotite, ilmenite and Ti-magnetite plus or minus quartz, and microlites of plagioclase and orthopyroxene set in rhyolitic groundmass glass. Plagioclasehosted melt inclusions (MI) are rhyolitic with major element compositions that are similar to groundmass glasses. H2O concentrations plotted versus incompatible elements for individual samples describe a trend typical of near-isobaric, volatile-saturated crystallisation. At 870 degrees C, the average magma temperature calculated from Fe-Ti oxides, the average H2O of 3.2 +/- 0.7 wt% and CO2 typically 0.5 Ma compared to those