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Title: The Year Leading to a Supereruption

Supereruptions catastrophically eject 100s-1000s of km3 of magma to the surface in a matter of days to a few months. In this study, we use zoning in quartz crystals from the Bishop Tuff (California) to assess the timescales over which a giant magma body transitions from relatively quiescent, pre-eruptive crystallization to rapid decompression and eruption. Quartz crystals in the Bishop Tuff have distinctive rims (<200 μm thick), which are Ti-rich and bright in cathodoluminescence (CL) images, and which can be used to calculate Ti diffusional relaxation times. We use synchrotron-based x-ray microfluorescence to obtain quantitative Ti maps and profiles along rim-interior contacts in quartz at resolutions of 1–5 μm in each linear dimension. We perform CL imaging on a scanning electron microscope (SEM) using a low-energy (5 kV) incident beam to characterize these contacts in high resolution (<1 μm in linear dimensions). Quartz growth times were determined using a 1D model for Ti diffusion, assuming initial step functions. Minimum quartz growth rates were calculated using these calculated growth times and measured rim thicknesses. Maximum rim growth times span from ~1 min to 35 years, with a median of ~4 days. More than 70% of rim growth times are less thanmore » 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption. Minimum growth rates show distinct modes between 10-8 and 10-10 m/s (depending on sample), revealing very fast crystal growth rates (100s of nm to 10s of μm per day). Our data show that quartz rims grew well within a year of eruption, with most of the growth happening in the weeks or days preceding eruption. Growth took place under conditions of high supersaturation, suggesting that rim growth marks the onset of decompression and the transition from pre-eruptive to syn-eruptive conditions.« less
 [1] ;  [2]
  1. Vanderbilt Univ., Nashville, TN (United States). Earth & Environmental Sciences
  2. Univ. of Chicago, IL (United States). Dept. of Geophysical Sciences and Center for Advanced Radiation Sources
Publication Date:
OSTI Identifier:
Grant/Contract Number:
FG02-94ER14466; EAR-1151337; EAR-1128799; AC02-06CH11357
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 11; Journal Issue: 7; Journal ID: ISSN 1932-6203
Public Library of Science
Research Org:
Chicago Univ.
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF)
Country of Publication:
United States