P-wave anisotropy in eclogites and relationship to the omphacite crystallographic fabric
Résumé
Measurements of P-wave velocity at room temperature and confining pressures up to 500 MPa were carried out on three eclogite mylonites collected from a shear zone in the Monviso area (Western Alps). P-wave velocities at a pressure of 400 MPa range from 7.7 km/s to 7.9 km/s, yielding to a maximum anisotropy of 6%. From the CPO of omphacite we estimated a maximum contribution of omphacite to the P-wave anisotropy of only 1.3%. These results suggest that primarily the compositional layering and secondary the fabric of minor constituent minerals significantly contribute to the seismic anisotropy. Because of the anisotropy, the seismic reflectivity of subduction zones may vary with the direction of observation.
Domaines
Géophysique [physics.geo-ph]Origine | Fichiers produits par l'(les) auteur(s) |
---|---|
Licence |