(2020) Mantle Controls on Kīlauea’s Magmatic and Eruptive Behavior
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05h: Room 2, Saturday 27th June 06:09 - 06:12
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Great presentation, Aaron! I have a couple questions: 1) The 206Pb/204Pb vs 87Sr/86Sr plot and the Nb/Y ratios, is that whole rock data or just glass data for each eruption and suite of rocks for both volcanoes? 2) Besides the 206Pb/204Pb vs 87Sr/86Sr plot and the Nb/Y vs eruption date plots, what evidence for mixing do the minerals from each of the rock suites (Mauna Loa and Kilauea) display for mixing between the "CC", LOA end-member, and KEA end-member compositions?
Thanks Timothy! (1) Most of these samples are "whole rock" (bulk) analyses, although many of them are very glassy (crystals are dominantly olivine). (2) I infer the mixing to occur between mafic olivine-controlled melts/magmas, whether during melt transport/extraction in the mantle or within the volcanic plumbing system. Thus, olivine would be the dominant crystallizing mineral phase. I would not expect to see the record of this mixing process directly in the olivine chemistry, but olivine-hosted melt inclusions might preserve some evidence of the process. Best regards, Aaron Pietruszka
HI Aaron - I found your seventh slide especially fascinating as it seems to indicate that the Mauna Loa and Kilauea plumbing systems are intimately connected at some level. Is that right? And if so, then why doesn't Mauna Kea have periods where it shifts entirely to erupting Kea-trend compositions (and similarly why wouldn't Kilauea erupt Loa-trend compositions)? Or are Kea and Loa trends defined by isotopic extrema? Or do I misunderstand, and your dashed lines in slide 8 indicate non-connecting plumbing systems, from source to surface? -Keith
Hi Keith! Thanks for all the great questions today....! Yes, I think there may be a connection between the volcanoes at the level of the melting region (but not within the lithospheric plumbing system itself). Helge Gonnermann and co-authors (2012) in Nature Geoscience present a model for "coupling at Mauna Loa and Kilauea by stress transfer in an asthenospheric melt layer". They model the interaction between these nearby volcanoes and suggest that they are competing for a common melt supply in the asthenosphere. The mechanism for this is related to the transfer of stress by melt migration through the porous melting region. So, if the total melt supply is relatively constant, then an eruption at one volcano can potentially inhibit the eruptive activity at the other. They show that this can be done without changes in the horizonal flow path of the melt, but that seems to have been a modeling choice in order to preserve the well-known geochemical differences of lavas between the volcanoes. I am suggesting that the two volcanoes may in fact be competing for a common source of melt, likely from the mantle that is undergoing melting in the spatial area that lies between them. This source/melt seems to be compositionally intermediate between Kilauea and Mauna Loa, and both volcanoes have at times mixed towards (or away from) this "common" component. In this way of thinking, the volcanoes might not overlap compositionally because the mixing extent with this common component is insufficient to completely overwhelm the other (larger) compositional differences in the source of each volcano (i.e., Kea vs. Loa end members). Best regards, Aaron
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