A reconnaissance of U-Pb zircon ages in the Cerro Galan system, NW Argentina: Prolonged magma residence, crystal recycling, and crustal assimilation

(206)Pb/(238)U ages obtained from Secondary Ionization Mass Spectrometry (SIMS) analyses of zircon crystals in eight ignimbrites from Cerro Galan (Central Andes) reveal insights into magma dynamics and crystallization histories of a sustained (>3.5 Ma), large-volume, crystal-rich magmatic system. This makes the Galan volcanic system an excellent example of repeated large-volume ignimbrite eruptions from a single magmatic system with eruptive recurrence intervals between similar to 50 ka and possibly >1 Ma. (40)Ar/(39)Ar sanidine and biotite ages indicate eruption ages between similar to 2.0 and 5.6 Ma, although biotite results are likely affected by extraneous (40)Ar. In each ignimbrite, interiors of zircon autocrysts frequently crystallized up to several 100 s ka prior to eruption, consistent with long upper-crustal residence times of the pre-eruptive Galan magmas.