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Accueil > Documents > Pages personnelles > Benoît ILDEFONSE > Recherche > En mer

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Drilling the Mid-Atlantic Ridge at 15°20’N : ODP Leg 209

Slow-spreading ridge magmatic activity is considered to be focused at segment centers. the Mid-Atlantic Ridge between 14° and 16°N is supposed to be a region of weak magmatic production, where mafic crust is locally absent and peridotites outcrops are common. ODP Leg 209 obejctive was to drill a seris of sites to study the along-axis variability of structure, mantle composition, alteration, ...

We drilled 1187 m of serpentinized peridotite, troctolite, gabbro, and diabase (recovery 30%), showing little along-axis variability. 15°N peridotites are among the most depleted abyssal peridotites ; they are weakly deformed. Deformation associated to mantle uplift/denudation is highly localized, along ductile shear zones, evolving as brittle faults at shallow depth. Very strong hydrothermal alteration affects 60% to 100% of recovered peridotites, and results of varying processes. The large amount of recovered gabbro indicates that these segment ends are not magma-starved. They confirm the heterogeneous nature of slow spreading ocean crust, composed of serpentinized peridotites and gabbros in poorly known proportions.

References :
- Ildefonse, B., Carlson, R.L., Garcés, M., Gee, J.S., Iturrino, G.J., and Ocean Drilling Program Leg 209 Scientific Party, 2003. Physical properties of gabbros and serpentinized peridotites at the MAR, 15°N. Shipboard results from ODP Leg 209. Eos Trans., 84(46), fall Meet. Suppl., Abstract V11E-0545.
- Kelemen, P.B., Kikawa, E., Miller, J., and ODP Leg 209 Shipboard Scientific Party, 2003. Localized Deformation Beginning more than 15 km Beneath the Mid-Atlantic Ridge, 14 to 16 N. Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract T51H-07, 2003.
- Kelemen, P.B., Kikawa, E., Miller, J., and ODP Leg 209 Shipboard Scientific Party, 2003. Igneous Crystallization Beginning at 20 km Beneath the Mid-Atlantic Ridge, 14 to 16 N. Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract V22H-03, 2003.
- Shipboard Scientific Party, 2003. Leg 209 Preliminary Report. ODP Prelim. Rpt., 109.
- Ildefonse, B., Carlson, R.L., and ODP Leg 209 Shipboard Scientific party, 2004. Serpentinisation and physical properties of Mid-Atlantic Ridge peridotites. Shipboard results from ODP Leg 209 (Invited). EGU 2004, Nice, Geophysical Research Abstracts, Vol. 6, 01855, 2004.
- Ildefonse, B., Carlson, R.L., and ODP Leg 209 Shipboard Scientific party, 2004. Serpentinisation and physical properties of Mid-Atlantic ridge Peridotites (15°N) ? Shipboard results from ODP Leg 209. Euroforum IODP-ICDP, Bremen, Germany, March 2004.
- Kelemen, P.B., Kikawa, E., Miller, J., and ODP Leg 209 Shipboard Scientific Party, 2004. Igneous Crystallization and Localized Deformation in the Shallow Mantle beneath Slow Spreading Ridges. Eos Trans. AGU, 85(17), Jt. Assem. Suppl., Abstract V53C-01, 2003.
- Kelemen, P.B., Kikawa, E., Miller, J., and ODP Leg 209 Shipboard Scientific Party, 2004. Igneous crystallization and localized deformation > 15 km beneath the Mid-Atlantic Ridge, 14-16 N. Goldschmidt Geochemistry Conference, June 2004, Copenhagen.
- Miller, J., Kelemen, P.B., Kikawa, E., and ODP Leg 209 Shipboard Scientific Party, 2004. Petrogenesis, alteration, and deformation in mantle peridotite from 14° to 16°N on the Mid-Atlantic Ridge : ODP Leg 209. Goldschmidt Geochemistry Conference, June 2004, Copenhagen.
- Kelemen, P.B., Kikawa, E., Miller, D.J., Abe, N., Bach, W., Carlson, R.L., Casey, J.F., Chambers, L.M., Cheadle, M., Cipriani, A., Dick, H.J.B., Faul, U., Garces, M., Garrido, C., Gee, J.S., Godard, M., Griffin, D.W., Harvey, J., Ildefonse, B., Iturrino, G.J., Josef, J., Meurer, W.P., Paulick, H., Rosner, M., Schroeder, T., Seyler, M. and Takazawa, E., 2004. Proc. ODP, Init. Repts., 209.
- Kelemen, P.B., Kikawa, E., Miller, D.J., and the Leg 209 Scientific Party, 2004. ODP Leg 209 drills into mantle peridotite along the Mid-Atlantic Ridge from 14°N to 16°N. JOIDES Journal, 30, 1, 14-19.
- Bach, W., H. Paulick, C. J. Garrido, B. Ildefonse, W. P. Meurer, and S. E. Humphris, 2006. Unraveling the sequence of serpentinization reactions : petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209, Site 1274), Geophys. Res. Lett., 33, L13306, doi:10.1029/2006GL025681.
- Kelemen, P.B., Kikawa, E. ; Miller, D.J., and Shipboard Scientific Party, 2007. Leg 209 summary : processes in a 20-km-thick conductive boundary layer beneath the Mid-Atlantic Ridge, 14°–16°N. In Kelemen, P.B., Kikawa, E., and Miller, D.J. (Eds.), Proc. ODP, Sci. Results, 209 : College Station, TX (Ocean Drilling Program), 1–33. doi:10.2973/odp.proc.sr.209.001.2007