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Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption

Journal of Geophysical Research B: Solid Earth

By:
, , , , and
DOI: 10.1029/2009JB007195

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Abstract

We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 80–90% closed-system crystal fractionation over a temperature interval from 1279°C to 719°C at 100 MPa, with an implied volume of parental basalt of ∼65 km3. Numerical models suggest, for wall rock temperatures appropriate to this depth, that 90% of this volume of magma would cool and crystallize over this temperature interval within a few tens of kiloyears. However, the range in 87Sr/86Sr, (230Th/238U), and (226Ra/230Th) requires open-system processes. Assimilation of the host sediments can replicate the range of Sr isotopes. The variation of (226Ra/230Th) ratios in the basalt to andesite compositional range requires that these were generated less than several thousand years before eruption. Residence times for dacites are close to 8000 years, whereas the rhyolites appear to be 50–200 kyr old. Thus, the magmas that erupted within only 60 h had a wide range of crustal residence times. Nevertheless, they were emplaced in the same thermal regime and evolved along similar liquid lines of descent from parental magmas with similar compositions. The system was built progressively with multiple inputs providing both mass and heat, some of which led to thawing of older silicic material that provided much of the rhyolite.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption
Series title:
Journal of Geophysical Research B: Solid Earth
DOI:
10.1029/2009JB007195
Volume
115
Year Published:
2010
Language:
English
Publisher:
American Geophysical Union
Publisher location:
Washington, D.C.
Contributing office(s):
Volcano Science Center
Description:
22 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth
First page:
B12201
Country:
United States
State:
Alaska
Other Geospatial:
Katmai