Volatiles and Fluids in Subduction Zones

Eclogite-blueschist transformation in subduction channels

INTRODUCTION

Descending oceanic plates in subduction zones dehydrate and the released fluids are involved in the deep fluid cycle of subduction zones. For a better understanding of this cycle it is necessary to get information I) about the amount and composition of the fluid that will enter the mantle wedge, II) how much may escape during upflow along the slab-wedge interface and III) how much is captured in the subduction channel. The aim of the study is to identify the sources of the fluid, which is flowing through the hydrous subduction channel. The study is focused on metabasic rocks, which underwent prograde dehydration to "dry" eclogite-facies rocks during burial in a subduction zone but experienced subsequently retrograde blueschist-facies rehydration during the ascension in a subduction channel. Key samples are partly rehydrated eclogites, which show sequences of increasing blueschist-facies overprinting.

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Fluid backflow in subduction zones