Magma residence and eruption at the Taupo Volcanic Center (Taupo Volcanic Zone, New Zealand): insights from rhyolite-MELTS geobarometry, diffusion chronometry, and crystal textures

摘要

The Taupo Volcanic Center [TVC; Taupo Volcanic Zone (TVZ), New Zealand] is home to the two most recent silicic caldera-forming eruptions in the TVZ-the giant (530 km(3) DRE) Oruanui supereruption and the large (35 km(3) DRE) Taupo eruption. This offers a unique opportunity to investigate similarities and differences between large and supersized volumes of rhyolitic magma at the TVC and more generally. We combine information from crystal textures (crystal size distributions), crystal compositions (Ti-in-quartz diffusion chronometry), and glass compositions (rhyolite-MELTS geobarometry) to investigate the crustal storage conditions, longevity, and eruption of these magmas. Results show differences between the storage depths of the Oruanui and Taupo magmas consistent with the differences in their glass silica contents but strikingly similar, short crustal residence times for the final crystal-poor, eruptible magma bodies (decades to centuries). Differences in groundmass textures between the two systems also likely reflect differences in ascent durations, decompression paths, and/or amounts of undercooling experienced by these systems due to the differences in their storage depths. Finally, comparing the evolution of storage depths and magma compositions at the TVC with those in a preceding central TVZ ignimbrite 'flare-up' supports the idea that the modern TVC may be flaring up and highlights the evolution of magma storage depths with increasing system maturity in this volcanic region.