(2020) The Reunion Mantle Plume is not Oxidized
Brounce M, Stolper E & Eiler J
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04d: Room 1, Thursday 25th June 23:18 - 23:21
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Hi Maryjo, enjoyed your talk and your findings. I have not ever gone back to look at those papers you cite about OIBs being of high fO2. How were those fO2s determined and were we ever sure that they reflected the source? Are you suggesting that many of the OIB sources might be similar to MORB in terms of fO2? Cin-Ty
Hi Cin-Ty. Thanks for watching! All of the papers I cite are Fe-XANES studies of both submarine pillow glass and melt inclusions in olivine and other phases that document reduction in Fe with volcanic degassing. They all use the "least degassed" samples to constrain the fO2 of the mantle source, but there is some variability in the path the studies take to go from the measured value in the sample and the primary melt. The Moussallam works generally equate the measured values to the mantle source directly. Myself, Shorttle, Hartley attempt to quantify the effects of crystallization from a melt in equilibrium with ~Fo90-92 and the more evolved compositions we measure, but of course this can be tricky to do very precisely so these calculations have uncertainties associated with them. Yes, I am suggesting that the mantle sources of Reunion magmas have similar fO2s to that of MORB. This is different from Hawaii, Iceland, Erebus, and the Canary Islands, which are all hypothesized to have mantle sources with higher fO2s than MORB.
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