Current and recent projects
A "black box" for magma reservoirs?
For direct access to the article in Science presenting these results, follow one of these links:
Abstract
Reprint
Full Text
Rubin AE, Cooper KM, Till CB, Kent AJR, Costa F, Bose M, Gravley D, Deering C, Cole J (2017) Rapid cooling and cold storage in a silicic magma reservoir recorded in individual crystals. Science 356(6343):1154-1156 doi:10.1126/science.aam8720
Abstract
Reprint
Full Text
Rubin AE, Cooper KM, Till CB, Kent AJR, Costa F, Bose M, Gravley D, Deering C, Cole J (2017) Rapid cooling and cold storage in a silicic magma reservoir recorded in individual crystals. Science 356(6343):1154-1156 doi:10.1126/science.aam8720
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Along with collaborators/coauthors listed above, my former PhD student Allie Rubin and I combined measurements of zircon age with durations of storage at high temperature from Li diffusion in the same zircon crystals to examine thermal conditions of magma storage on a crystal-by-crystal scale. This is an exciting new method to study thermal conditions of storage, and our initial data set from the Kaharoa eruption in New Zealand showed that out of tens to hundreds of thousands of years of storage, each crystal could only have spent years to decades above the rheological lock-up temperature, and decades to centuries above the solidus. This implies that the thermal conditions within this reservoir are highly variable, and that heating and cooling associated with magma recharge - and with the assembly of the magma body prior to eruption - must have been very rapid. The results were published in Science (full reference and links to the paper above) and we plan to follow up with more work to see whether these conditions apply to other eruptions and other systems.
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Thermal histories of magmas: mostly "cold storage"?
One of my most exciting and interesting new research directions involves reconstructing the thermal conditions of magma storage by combining U-series crystal ages with temperature-dependent time scales (e.g. diffusion of trace elements ). The first place where my collaborator Adam Kent (OSU) and I developed this idea was at Mount Hood, OR, and we had a paper in Nature in 2014 presenting the surprising result that Mount Hood's magma reservoir spent <12% (and likely <1%) of the past 21 kyr at temperatures above 750 degrees C. This corresponds to the "lock-up" temperature where the magma transitions from crystals suspended in a liquid at higher temperatures to a locked crystal network with interstitial liquid (a state which is much harder to mobilize than a largely-liquid magma). We also put together a compilation of existing data for other volcanic systems, and the partial data sets suggest that this "cold storage" mode of behavior is common. Adam and I recently teamed up with Chris Huber (Georgia Tech) and have a new NSF award to examine other volcanic systems to determine whether "cold storage" is indeed common, and what the implications are for modeling magma reservoir dynamics - PhD student Kevin Schrecengost will be working on this from the UCD side.
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Mount Hood, OR
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Magma mixing at Lassen Volcanic Center
Magma reservoir processes at Taupo Volcanic Center, New Zealand
Tephra sequence near Rotorua
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Using similar techniques to studies of Yellowstone, we are looking into the magma storage conditions and time scales at Okataina Caldera Complex, Taupo Volcanic Zone, New Zealand. I started this research in 2006 with Mark Jellinek (UBC), Jim Cole (Univ. Canterbury) and Erik Klemetti while he was a postdoc here. We published a paper on initial results combining trace-element analyses with U-series ages of zircon from the Kaharoa eruption of Tarawera Volcano. Since then, PhD student Allie Rubin worked on continuing the zircon work (including adding Hf isotopic data for zircon), and extended the investigation that Erik started on major phases. We are currently collaborating with Adam Kent (OSU), Darren Gravley (Univ. Canterbury), and Chad Deering (Michigan Technical University) to continue various aspects of this work, funded by NSF's GeoPRSIMS program. PhD students Tyler Schlieder and Elizabeth Grant here at UCD have been working on U-series dating and diffusion work.
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U-series dating of carbonates
I have been delving into the world of low-temperature processes by setting up U-series dating of carbonates at UCD. This technique provides critical temporal control for proxy records of climate change recorded by cave deposits (speleothems), and dating soil (pedogenic) carbonate growth can date the formation of geomorphic surfaces that are key markers of structural and geomorphologic events. Initial development was supported by a collaborative NSF award to study speleothems in the Sierra Nevada of CA (with Prof. Isabel Montañez (UCD) and Dr. Warren Sharp (Berkeley Geochronology Center)). Continuing development is being pushed forward by PhD student Barbara Wortham (in Isabel Montañez group).