Volcanic Probe of Batholith Assembly and Maturation: Age and Source of Crystal Cargo in the Aucanquilcha Volcanic Cluster, Central Andes

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Intellectual merit. A focused investigation of the Aucanquilcha Volcanic Cluster (AVC) of the central Andes is proposed to understand the roles of crystal recycling and crustal hybridization in controlling the magmatic evolution of long-lived magma systems. The AVC comprises some 15 major andesite and dacite volcanoes that developed over an 11 m.y. period. It is likely that this magmatism is related to evolution of a complex magma reservoir system, but how such systems evolve and how they modify or interact with the crust are unresolved questions. For example, are magmas derived from a single long-lived reservoir or from a sequence of discrete magma bodies? To answer this question, it is proposed to characterize the phenocryst populations of representative eruptive deposits spanning the life of the volcanic field. Ages and sources of crystal populations will be evaluated through multiple analytical approaches including U-Pb dating of zircons, Ti-in-zircon thermometry, in situ Sr isotopic analyses of zoned plagioclase and apatite crystals, and bulk rock Sr-Nd and Pb isotopic compositions. These data will reveal the thermal evolution of magma sources as well as mixing between new and old magma and between magmas and their crustal host rocks.Broader impacts include support of a graduate and several undergraduate students and international collaboration with Chilean geologists from SERNAGEOMIN. The work will be relevant to understanding related porphyry copper mineralization, and will tie in with regional mapping and petrologic studies in the region. In addition to scientific publications, research findings will be incorporated into teaching materials by the PIs.