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| Titel |
Double-Diffusive Layers and Phase Transitions |
| VerfasserIn |
Sabine Dude, Ulrich Hansen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111313
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| Publikation (Nr.) |
 EGU/EGU2015-11418.pdf |
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| Zusammenfassung |
| Researching the thermal evolution of the Earth’s mantle on numerical base is very
challenging. During the last decade different approaches are put forward in oder to
understand the picture of the today’s Earth’s mantle. One way is to incorporate all the known
features and physics (plate tectonics, phase transitions, CMB-topography, ...) into numerical
models and make them as complex (or ’complete’) as possible to capture Earth’s mantle
processes and surface signals. Another way is, to take a step back and look at less complex
models which account for single processes and their interaction and evolution. With these
’simpler’ models one is able look in detail into the physical processes and dependencies on
certain parameters.
Since the knowledge of slab stagnation in the transitions zone of the Earth’s mantle
the question whether the mantle is or at least has been layered to some degree is
still under debate. On this basis we address two important features that lead to
layered mantle convection and may affect each other and with this the thermal
evolution of the mantle. It is commonly known the main mantle mineral olivine
pass through various phase changes with depth [1]. Detailed numerical studies
had been carried out to ascertain the influence on convective motion and planetary
evolution [2]. It is still heavily discussed whether the endothermic phase change
at 660km depth can lead an isolated lower mantle. Most of the numerical studies
favour a model which has phases of layering that are disrupted by catastrophic
events.
In the last years double-diffusive convection has also been intensively studied with regard to
planetary mantle evolution such as pile formation and core-mantle boundary topography [3].
However, another striking feature still posing open questions are evolving layers
self-organised from a previous non layered state. Considering a chemical component that
influences the density of a fluid in addition to the temperature leads to dynamical phenomena
that have no counterpart in pure thermal convection.
In oder to determine the interaction of double-diffusive layers with a phase transition we
carried out numerical simulations ranging from exothermic to endothermic conditions.
Taking into account a depth and temperature dependence of the phase transition the results
show that on the one hand double-diffusive layering is strongly affected by the presence of
phase transition but on the other hand the equilibrium position of the phase transition is
shifted depending on the properties of the considered transition. In addition to that we
incorporate the chemical dependence of the phase change and determine the influence on the
layer growth and the overall dynamics.
References
[1]ÂÂÂSchubert, G., Yuen, D. A., Turcotte, D. L., Role of Phase Transitions in a Dynamic Mantle. Geophys.
J. Roy. Astron. Soc., 42:705–735, 1975.
[2]ÂÂÂ Christensen, U., Effects of Phase Transitions on Mantle Convection. Ann. Rev. Earth Planet. Sci.,
23:65–88, 1995.
[3]ÂÂÂ Tackley, P. J. Dynamics and evolution of the deep mantle resulting from thermal, chemical, phase
and melting effects. Earth-Sci. Rev., 110:1–25, 2012. |
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