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Accueil > Documents > Pages personnelles > Benoît ILDEFONSE > Recherche > Propriétés physiques de la croûte océanique

Propriétés physiques de la croûte océanique

Electrical properties of oceanic rocks

Petrological and structural characteristics of gabbros in ODP Hole 735B, together with electrical formation factor, surface conduction fraction, and Vp

Electrical properties of low-porosity crystalline media are extracted from series of sample conductivity measurements at different salinities of the saturating fluid (Revil and Glover, 1998). Electrolytic conduction is seen through the electrical formation factor, which is related to sample porosity via the electrical tortuosity and the cimentation index. Surface conductivity is related to alteration.
The analysis of the porous structure of the gabbroic section in ODP Hole 735B indicates that this section is segmented in two parts, as a result of distinct deformation/alteration histories above and below 850meters below sea floor.
In the Oman ophiolite (GEOman experiment), gabbros and serpentinized peridotites have distinct electrical properties, which, together with the difference in seismic anisotropy, are possible criteria to geophysically distinguish serpentinized peridotite and gabbros in the ocean crust.

References :
- Ildefonse, B., Pezard, P., Wilcock, W.S.D., Toomey, D.R., Constable, S. and Mainprice, D., 2000. Seismic anisotropy of peridotites and gabbros from the Oman ophiolite (GEOman Experiment), EGS 2000, Nice.
- Ildefonse, B., and Pezard, P., 2000. Propriétés électriques et structure poreuse des gabbros du puits 735B (ODP Leg 176), dorsale sud-ouest indienne. Journées Dorsales, Sept 2000, Roscoff.
- Ildefonse, B., Einaudi, F., Pezard, P.A., and Hermitte, D., 2001. Physical properties of crustal oceanic rocks, with implications in terms of nature of seismic boundaries. EGS 2001, Nice.
- Ildefonse, B., Pezard, P.A., Mainprice,D., Wilcock, W.S.D., Toomey, D.R., and Constable, S., 2001. Can we Distinguish Between Serpentinised Peridotites and Gabbros from their Physical Properties ? Insights from the GEOman Experiment. EUGXI, Strasbourg. (LS02:WEpo08:PO). Download poster
- Ildefonse, B., Pezard, P.A., Mainprice, D., Einaudi, F., 2001. Petrophysical properties of the lower crust and upper mantle in the oceanic lithosphere. Petrophysical Properties of crystalline rocks, Geol. Soc. London, Borehole Research Group, London, 10-11 Sept 2001.
- Ildefonse, B., Pezard, P.A., and Einaudi, F., 2002. Electrical properties of slow-spreading ridge gabbrosfrom ODP Site 735, Southwest Indian Ridge. Interridge SWIR (SouthWest Indian Ridge) workshop, April 2002, Southampton, UK.
- Ildefonse, B. and Pezard, P.A., 2001. Electrical properties of slow-spreading ridge gabbros from ODP site 735, Southwest Indian Ridge. Tectonophysics. 330 : 69-92.