RAPID REJUVENATION AND MAGMA STORAGE CONDITIONS AT VOLCÁN OLLAGÜE, ANDEAN CENTRAL VOLCANIC ZONE, CHILE-BOLIVIA

Magma storage and plumbing system architecture play key roles in the differentiation and eruption style of intermediate arc magmas. The depth of magma storage and the complexity of the plumbing system that brings magma to the surface evolves over time. Textural and geochemical analyses of plagioclase feldspar are effective tools in the construction of plumbing architectures, while zircon trace element contents exhibit trends that provide a window in cooling, fractionation and mixing that whole rock geochemistry is too broad to observe. We examine the connected history of dacite-dominant volcanic rocks from Ollagüe Volcano in the Central Andes using zircon U-Pb crystallization ages and trace element contents, Ti-in-zircon temperatures, and plagioclase trace-element contents lavas to determine the connection between the rejuvenation and magma storage during the development of the magma plumbing system. Crystallization ages of zircon from Ollagüe lavas span a ~ 1.2 Ma interval from 0.3 Ma to 1.5 Ma with temperatures between 670 and 850˚C. Coupling these temperatures with Hf and REE contents, U/Yb and Yb/Gd ratios, and Eu/Eu* values suggest rejuvenation of zircon after storage. Trace element ratios of zircon and plagioclase show trends of multiple influences, including crystallization and cooling, amphibole fractionation, and titanite/apatite fractionation. These data reveal rejuvenation conditions and the complexities of the plumbing system of Ollagüe. Ultimately these data confirm that compositional hybridization is being controlled through periodic high-to-low volume injections from an external source. Ollagüe is located on the edge of a regional magma body, it is very likely that the complexities and geochemical constraints of Ollagüe’s magma plumbing system are linked to the interaction with well-homogenized, low percent melt reservoir. We conclude the consistent zircon trace element patterns over time suggest that Ollagüe magma batches originated from a long-lived hot zone of extractable mush within the low percent melt zone of a larger, cool rigid mush.