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Timescales of magma recharge and reactivation of large silicic systems from Ti diffusion in quartz

DOI: 10.1093/petrology/egs020 DOI Help

Authors: Naomi Matthews (University of Oxford) , Christian Huber (Georgia Tech) , David Pyle (University of Oxford) , Victoria Smith (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Petrology , VOL 53 , PAGES 1385-1416

State: Published (Approved)
Published: April 2012
Diamond Proposal Number(s): 4842

Abstract: Timescales of magma chamber assembly and recharge are investigated here by applying 1D and 2D diffusion modeling techniques to high-resolution maps of titanium in quartz from a large-volume ignimbrite eruption in the Taupo Volcanic Zone, New Zealand. We compare quartz zonation patterns and associated diffusion timescales from the ?340?ka Whakamaru super-eruption (magma volume ?1000?km3) with the Younger Toba Tuff super-eruption, 74?ka (2000?km3), Sumatra, and the smaller volume ?50?ka Earthquake Flat eruption (10?km3), Okataina Caldera Complex, New Zealand. Two principal timescales are presented: that of chamber recharge and eruption triggering events, and that of magma generation (involving long-term assembly, stirring and reactivation). Synchrotron micro-X-ray fluorescence maps of core–rim quartz transects provide a high-resolution record of magma chamber conditions throughout quartz crystallization. Quartz crystals from the Whakamaru magma display complex zonation patterns indicating fluctuating pressure–temperature conditions throughout the crystallization history. Toba and Earthquake Flat, in contrast, display simple quartz-zoning patterns and record slightly longer periods of crystal residence in the chamber that fed the eruption. We apply Lattice Boltzmann 2D diffusion modeling to reconstruct the timescales of quartz crystal zonation, accounting for crystal boundary complexities. Quartz crystal orientation is also accounted for by using geometry constraints from the synchrotron data. Our calculations suggest that crystal-mush reactivation for the main Whakamaru magma reservoir occured over a period of the order of 103–104 years. Both the Earthquake Flat and Toba eruptions experienced a significant recharge event (causing a temperature and pressure change), which occurred within ?100 years of eruption. In comparison, the complex Whakamaru quartz zoning patterns suggest that the magma body experienced numerous thermal and compositional fluctuations in the lead-up to eruption. The final magma recharge event, which most probably triggered the eruption, occurred within ?10–60 years of the eruption. Even though the volume of these systems spans two orders of magnitude, there does not appear to be a relationship between magma volume and diffusion timescale, suggesting similar histories before eruption.

Journal Keywords: Diffusion; Quartz; Rhyolite; Time Scales; Magma Chamber

Subject Areas: Environment, Technique Development

Instruments: I18-Microfocus Spectroscopy

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