[IGPP Everyone] [EPSS Everyone] GEOCHEMINAR: FRIDAY, Oct 20, at Noon

[Kevin McKeegan]

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*GEOCHEMINAR*
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*Dr. M**é**lanie Barboni*

*UCLA*



*Zircon: the magmatic time capsule*



In this talk, I will illustrate how zircon is our premier geochronometer to
understand one of Nature’s most dramatic expressions of magmatic activity:
volcanic eruptions. Recently, the case has been made that volcanic
reservoirs are rarely molten and only capable of eruption for durations as
brief as 1,000 years following magma recharge. If the “cold storage” model
is generally applicable, then geophysical detection of melt beneath a
volcano would likely be a sign of imminent eruption. However, some volcanic
centers have been active for tens of thousands of years and show evidence
for the continual presence of melt. To address this seeming paradox, I have
been coupling zircon geochronology and geochemistry using both high-spatial
resolution and high temporal resolution analytical methods on different
magmatic systems to track the pre-eruptive thermal and chemical history of
sub-volcanic magma reservoirs. The results show that volcanic reservoirs
are generally stored warm and are likely eruptible for periods of several
tens of thousands of years or more with punctuated eruptions during these
periods. Thus, contrary to recently proposed models, the presence of
intra-crustal melt alone is insufficient as an indicator of imminent
eruption, but instead represents the normal state of magma storage
underneath dormant volcanoes.




*3853 Slichter (conference room)*


*Friday, October **20th **at 12:00 noon*

*all are welcome!*

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Kevin D. McKeegan
Professor of Cosmochemistry & Geochemistry
Dept. of Earth, Planetary, and Space Sciences
UCLA
Los Angeles, CA 90095-1567
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mckeegan at epss.ucla.edu
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