Diverse late‐stage crystallization and storage conditions in melt domains from the Youngest Toba Tuff revealed by age and compositional heterogeneity in the last increment of accessory phase growth

Contributions to Mineralogy and Petrology
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Abstract

The chemical record contained within the nal increment of growth on crystals is utilized to reveal the dynamics and time- scales of magma assembly and storage before eruption of the cataclysmic 2800 km3 Youngest Toba Tu (YTT), Indonesia. In situ U–Th disequilibrium dates and trace element concentrations were obtained via secondary ionization mass spectrometry (SIMS) on unsectioned and unpolished faces of individual zircon and allanite crystals. The six high-silica (> 73 wt% SiO2) pumices from which crystals were derived are among the more evolved and lower crystallinity (< 25 wt%) pumices from the YTT eruption, and likely represent the melt-dominated portion of the magma system. Discrete SIMS measurement cycles were coupled with statistical treatments to detect zircon and allanite surface zoning domains at the ~ 1 μm scale. Coupled r-MELTS and accessory phase saturation modeling indicates that at the granite ternary minimum or ‘eutectoid’ conditions that de ne this portion of the YTT, zircon and allanite crystallization is dependent on and proportionate to major phase crystallization, and is more limited than at pre-eutectoid conditions. A lower proportion of near-eruption zircon surface ages in the comparatively cool and wet YTT relative to other hotter and drier voluminous silicic eruptions could re ect the in u- ence of eutectoid storage conditions on magmatic responses to remobilization-related magmatic recharge.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Diverse late‐stage crystallization and storage conditions in melt domains from the Youngest Toba Tuff revealed by age and compositional heterogeneity in the last increment of accessory phase growth
Series title Contributions to Mineralogy and Petrology
DOI 10.1007/s00410-019-1566-6
Volume 174
Year Published 2019
Language English
Publisher Springer
Contributing office(s) Volcano Science Center
Description 31, 21 p.
Country Indonesia
Other Geospatial Youngest Toba Tuff