Elevated Fe oxidation states, like H2O and select trace elements, are linked to material recycling in Izu-Bonin-Mariana lavas in space and time

Maryjo Brounce

Thursday, October 22, 2020 - 14:15
Thematic Seminar: Redox Controls on Planetary Processes
Maryjo Brounce

Join us Thursday mornings throughout October for seminars on the theme of redox controls on planetary processes. 

Continuing the series, Maryjo Brounce of UC Riverside will present, "Elevated Fe oxidation states, like H2O and select trace elements, are linked to material recycling in Izu-Bonin-Mariana lavas in space and time".

Abstract:

Elevated water and select trace element concentrations, and higher Fe3+/TFe ratios distinguish arc basalts from mid-ocean ridge basalts. It is broadly accepted that the elevated water contents and certain incompatible trace element abundances are linked to the presence of fluids and/or melts from subjecting oceanic slabs, but recently, the reason for elevated Fe3+/TFe of arc basalts has been more controversial. In this talk, I will show measurements of major, trace, and volatile contents and Fe3+/TFe ratios of submarine glass and olivine hosted melt inclusions from the Izu-Bonin-Mariana system that sample 1) a range of extent of influence from the subducting Pacific plate from the back-arc to the central arc, and 2) various stages of the lifetime of the system, from initiation of the margin ~52 Ma to present day. Despite changes in crustal thickness, major element chemistry of mafic lavas, and dissolved sulfur contents of silicate glass in both space and time, erupted samples with Fe3+/TFe ratios higher than typical MORB always have elevated water and select trace element contents. This coherence for all erupted samples from the Eocene to present day and from the back-arc to well-established arc volcanoes strongly links the production of oxidized, hydrous lavas with the release of fluids and/or melts into the mantle in the IBM system. 


 

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