SHORT ERUPTION WINDOWS FOR LARGE VOLUME DOMES IN THE ALTIPLANO PUNA VOLCANIC COMPLEX, CHILE

Volcanism in the waning stages of the Altiplano Puna Volcanic Complex (APVC) of the Central Andes transitioned from large volume ignimbrite eruptions to smaller domes and coulees. Five of these Quaternary silicic domes: the Chao, Tocopuri, Chillahuita, Chascon, and Chanka lava domes, erupted approximately 40 km³ of dacite and rhyodacite over an area of 2000 km². The eruption ages and zircon crystallization ages of these domes are within analytical error, which is more consistent with the modern arc front composite volcanoes, but geochemically, the domes more resemble the ignimbrites. This creates an inconsistency in the magmatic evolution of the APVC and the relationship between the arc volcanoes and the ignimbrites. Aluminum in hornblende pressures and temperatures within the magma chamber of the domes and Volcan Ollagüe suggest the arc volcanoes are stored at higher temperatures than the domes. It is suggested that determining the temporal variation of Hf isotopes in combination with trace element contents can be used to estimate magma flux and homogeneity of the system. We determine Hf isotope ratios and trace element contents and combine these data with existing eruption ages and trace element contents to determine the magmatic storage longevity and magma source variation. We test the hypothesis that the domes are sourced from a similar source to the ignimbrites but were remobilized quickly from a near solidus mush.