Seismic wave velocity and anisotropy of serpentinized peridotite in the Oman ophiolite

Dewandel, B., Boudier, F., Kern, H., Warsi, W. and Mainprice, D. (2003) Seismic wave velocity and anisotropy of serpentinized peridotite in the Oman ophiolite Tectonophysics, 370 (1-4). pp. 77-94. DOI 10.1016/s0040-1951(03)00178-1.

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Shallow seismic measurements in harzburgite from the Oman ophiolite performed in a zone where the maximum horizontal anisotropy is expected (vertical foliation and horizontal lineation) point to a dominant dependence of seismic properties on fracturing. Optical microscopy studies show that microcracks are guided by the serpentine (lizardite) penetrative network oriented subparallel to the harzburgite foliation and subperpendicular to the mineral lineation, and that serpentine (lizardite) vein filling has a maximum concentration of (001) planes parallel to the veins walls. The calculated elastic properties of the oriented alteration veins filled with serpentine in an anisotropic matrix formed by oriented crystals of olivine and orthopyroxene are compared with seismic velocities measured on hand specimens. Laboratory ultrasonic data indicate that open microcracks are closed at 100 MPa pressure, e.g. (J. Geophys. Res. 65, (1960) 1083) and (Proc. ODP Sci. Results Leg 118, (1990) 227). Above this pressure, laboratory measurements and modeling show that P-compressional and S-shear wave velocities are mainly controlled by the mineral preferred orientation. Veins scaled with serpentine are effective in slightly lowering P and S velocities and increasing anisotropy. The penetrative lizardite network does not affect directly the geometry of seismic anisotropy, but contributes indirectly in the fact that this network controls the microcrack orientations. Comparison between seismic measurements of peridotite and gabbro in the same conditions suggest that P- and S-waves anisotropies are a possible discriminating factor between the two lithologies in the suboceanic lithosphere. (C) 2003 Published by Elsevier B.V.

Document Type: Article
Keywords: Oman ophiolite seismic wave velocity anisotropy p-wave ivrea zone rocks lithosphere elasticity minerals samples cracks ridges
Research affiliation: Kiel University
DOI etc.: 10.1016/s0040-1951(03)00178-1
ISSN: 0040-1951
Date Deposited: 24 Jan 2012 05:20
Last Modified: 08 Oct 2012 10:34

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