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Titolo:
REGULAR VS, CHAOTIC MANTLE MIXING
Autore:
FERRACHAT S; RICARD Y;
Indirizzi:
ECOLE NORMALE SUPER LYON,45 ALLEE DITALIE F-69364 LYON FRANCE ECOLE NORMALE SUPER LYON F-69364 LYON FRANCE
Titolo Testata:
Earth and planetary science letters
fascicolo: 1-2, volume: 155, anno: 1998,
pagine: 75 - 86
SICI:
0012-821X(1998)155:1-2<75:RVCMM>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
TIME-DEPENDENT CONVECTION; CHEMICAL GEODYNAMICS; OCEANIC-CRUST; FLOW; HETEROGENEITIES; STREAMLINES; MECHANICS; MOTIONS;
Keywords:
CONVECTION; MANTLE; MIXING; 3-DIMENSIONAL MODELS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
35
Recensione:
Indirizzi per estratti:
Citazione:
S. Ferrachat e Y. Ricard, "REGULAR VS, CHAOTIC MANTLE MIXING", Earth and planetary science letters, 155(1-2), 1998, pp. 75-86

Abstract

Most quantitative models of mantle mixing have been based on simulations of tracer advection by 2-D flows. The present work shows that the mixing properties of 3-D time-independent flows cannot be understood or extrapolated from previous 2-D models. Steady convective flows appropriate to simulate a uniform fluid with large viscosity are restrictedto poloidal components. They seem to have regular streamlines. However, the existence of plates on the Earth's surface imposes the existence of a strong toroidal field. Flows where both poloidal and toroidal components are present can yield chaotic pathlines which are very efficient in mixing the mantle. Within areas of turbulent mixing where the stretching increases exponentially with time, regular islands of laminar stretching persist in which unmixed material can survive. Our findings indicate that the intrinsic three-dimensionality of convection coupled with plates as much as its time dependence must be included in numerical models to understand the mixing properties of the mantle. As the viscosity is significantly larger in the lower mantle than in the upper mantle, the toroidal component of the flow is confined to the upper mantle, where a more thorough mixing should take place. (C) 1998 Elsevier Science B.V.

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Documento generato il 25/11/20 alle ore 06:39:16