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| Titel |
Water migration in the subduction mantle wedge: a two-phase flow approach |
| VerfasserIn |
Hongliang Wang, Ritske S. Huismans, Stéphane Rondenay |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148474
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| Publikation (Nr.) |
 EGU/EGU2017-12733.pdf |
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| Zusammenfassung |
| Subduction zones are the main entry points of water into earth’s mantle and play an important
role in the global water cycle. The progressive release of water by metamorphic dehydration
induces important physical-chemical process and may play an important role in the
generation of subduction zone earthquakes. Yet, how water migrates in subduction
zones is not well understood. We investigate this problem by explicitly modeling a
two-phase flow during subduction, in which the fluid migrates through compaction and
decompaction of the solid matrix. Our results show that fluid migration may occur
preferentially along the subduction interface from where it feeds into the mantle
wedge. This process is strongly affected by the dynamics of the subduction process
in our model, which includes in three characteristic phases: (1) an early stage of
subduction initiation; (2) an intermediate stage of gravity-driven steepening of the
slab; and (3) a late stage where the slab becomes supported from the bottom. With
a background porosity of ϕ0= 2x10−4, water is able to migrate horizontally up
to ∼300 km from the subduction trench: the deeper the water releases from the
subducting slab, the further it can migrate horizontally. The models suggest the
mantle wedge may be characterized by a lower permeability zone surrounding
by two high porosity pathways, which is consistent with Vp/Vs ratio anomalies
observed in tomographic models of some subduction zones (e.g., western Greece).
We further find that (de)compaction enhances fluid migration significantly and
water can still migrate into the mantle wedge even under very low background
porosity and permeability (e.g. ϕ0= 2x10−5 and k0=10−25). The feedback of fluid
migration on the solid dynamics, which is not included here, will be subject of
further study and is anticipated to play an important role in the subduction dynamics. |
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