Seismic properties of the supra-subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka

Vincent Soustelle (1) , Andrea Tommasi (1)

1 Géosciences Montpellier

This work presents seismic properties derived from a detailed microstructural study of supra-subduction mantle xenoliths extracted by the active Avacha volcano in the southern Kamchatka arc. These peridotites underwent low-stress deformation and syn- to late-kinematic reactive percolation of hydrous melts or fluids leading to local orthopyroxene enrichment and dispersion of the olivine CPO in the shallow mantle wedge. All samples show an axial [ 100] olivine CPO implying fast S-wave polarization parallel to the flow direction in the mantle. Orthopyroxene-enrichment by reactive fluids/melts percolation lowers the Vp/Vs ratio, but cannot explain the Vp/Vs ratios <1.7 mapped in the Japan and Andes forearc mantle. These low Vp/Vs ratios may however be explained by considering the intrinsic anisotropy of the peridotites.

Mots clés: seismic properties; xenolith; subduction

Domaines: Tectonique; Milieux et Changements globaux

Vincent Soustelle, Andrea Tommasi. Seismic properties of the supra-subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka. Geophysical Research Letters, 2010, 37, pp.L13307. ⟨10.1029/2010GL043450⟩. ⟨hal-00512636⟩