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| Titel |
The fate of subducted continental material: Results from coupled thermodynamic-thermomechanical numerical modelling |
| VerfasserIn |
Juan Carlos Afonso, Sergio Zlotnik |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037999
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| Zusammenfassung |
| It is now accepted that relatively large sections of continental crust were subducted to depths
> 100 km and exhumed at numerous locations worldwide (e.g. Kokchetav massif, Otrøy
Island, etc). The possibility of even deeper subduction and the existence of a “depth of no
return" for subducted continental material has also been hypothesized based on a number of
experimental and geochemical/isotopic observations. However, the effects of such a “depth of
no return" on the dynamics of ultra-deep continental subduction (> 200 km depth) and the
ultimate fate of different subducted continental rocks (e.g. sedimentary, volcanic, igneous,
etc) have not been thoroughly studied with coupled thermodynamic-thermomechanical
models, but only estimated based on mass balance calculations from high-pressure
experimental studies.
In this contribution we present results of a numerical study of an arc-continent collision
setting using an internally consistent combination of mineral physics and thermodynamic
calculations into fully dynamic simulations (i.e. no velocity conditions imposed). For this we
have developed a new internally-consistent thermodynamic database capable of modelling all
important UHP phases in continent-like compositions (e.g. K-hollandite, CAS phase,
majorite, etc). Hydration/dehydration reactions, fluid migration, and hydrous melting are also
accounted for. Based on the results of these simulations we address: i) the dynamic
effects of the compositional/thermal structure of the subducted lithosphere (crust +
mantle), ii) the influence of rheological layering on the system’s dynamics, iii) the
possibility of continental material stalling indefinitely within the transition zone
(440-660 km depth), iv) its effects on the physical properties of the transition zone,
and v) the possibility of continental material subducting down to lower mantle
depths. |
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