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Accueil > Documents > Pages personnelles > Benoît ILDEFONSE > Recherche > Structures et Propriétés physiques des magmas

Structures et propriétés physiques des magmas

Modelling the seismic properties of partially crystallized gabbro

A model of seismic velocities in partially cristallized gabbros shows that, taking into account the anisotropy of basaltic melt distribution in the crystalline aggregate (deduced from textural analysis of Oman ophiolite gabbros), the seismic refraction velocity profiles at the EPR axis are compatible with liquid fractions as high as 10-15%. Because of the large scale distribution, controlled by the varying gabbro foliation dip (again, as shown in oman), the model can explain the vertical velocity gradient beneath the ridge axis, without vertical variations of temperature and/or liquid fraction.


P-wave velocity as a function of melt fraction for various melt shapes.
(a) VpZ (perpendicular to the foliation). (b) VpX (parallel to the lineation)


















References
- Lamoureux, G., Ildefonse, B., Mainprice, D. and Nicolas, A., 1996. Modeling the Seismic Properties of Fast-Spreading Ridge Crustal LVZ Using Oman Ophiolite Gabbros. AGU Fall meeting 1996, San-Francisco.
- Lamoureux, G., Ildefonse, B. et Mainprice, D., 1998. Modélisation des propriétés sismiques de la chambre magmatique (LVZ) aux dorsales océaniques rapides à l’aide des gabbros de l’ophiolite d’Oman. RST98, Brest.
- Lamoureux, G., Ildefonse, B. and Mainprice, D., 1999. Modelling the seismic properties of fast-spreading ridge crustal LVZ : insights from Oman gabbro textures. Tectonophysics. 312 : 283-301.