The role of F-clinohumite in volatile recycling processes in subduction zones

Grützner T, Klemme, S, Rohrbach, A, Gervasoni, F, Berndt J

Abstract

It is not well understood how much water and other volatiles arereally contained in different mantle rocks or minerals, and how thesevolatiles are transported down into the deeper mantle in subductionzones. Here we present new experimental data showing that a commonmineral found in subduction zone rocks, the hydrated Mg-silicate clinohumite,is much more stable in the mantle than previously anticipated.We show that even small amounts of F- substituting for OH- are sufficientto stabilize clinohumite to temperatures well above the normalmantle geotherm. Based on this finding we propose that in subductionzones, clinohumite effectively transports water and other volatiles fromshallow depths to the transition zone of the mantle. This can drasticallyincrease the amount of fluorine and water recycled into the deep mantle.