P. Agrinier, R. Hekinian, D. Bideau, and M. Javoy, O and H stable isotope compositions of oceanic crust and upper mantle rocks exposed in the Hess Deep near the Galapagos Triple Junction, Earth and Planetary Science Letters, vol.136, issue.3-4, pp.183-196, 1995.
DOI : 10.1016/0012-821X(95)00159-A

J. Arkani-hamed, Remanent magnetization of the oceanic upper mantle, Geophysical Research Letters, vol.86, issue.1, pp.48-51, 1988.
DOI : 10.1029/GL015i001p00048

J. Arkani-hamed, Thermoviscous remanent magnetization of oceanic lithosphere inferred from its thermal evolution, Journal of Geophysical Research, vol.93, issue.2, pp.17-421, 1989.
DOI : 10.1029/JB094iB12p17421

A. H. Barclay, D. R. Toomey, G. M. Purdy, and S. C. Solomon, FARA microearthquakes experiments III: Results from the Mid-Atlantic Ridge at 35 ? N, AGU Fall meeting, p.601, 1993.

K. Becker, Ground-truth from the young oceanic crust at hole 504B, summary of results from DSDP, Rev. Geophys, vol.69, issue.27, pp.79-102, 1989.

D. Bideau, R. Hébert, R. Hekinian, and M. Cannat, Metamorphism of deep-seated rocks from the Garrett ultrafast transform (East Pacific Rise near 13 ? 25 S), J. geophys. Res, vol.96, issue.10, pp.79-89, 1991.

M. M. Bina and B. Henry, Magnetic properties, opaque mineralogy and magnetic anisotropies of serpentinized peridotites from ODP Hole 670A near the Mid-Atlantic Ridge, Physics of the Earth and Planetary Interiors, vol.65, issue.1-2, pp.88-103, 1990.
DOI : 10.1016/0031-9201(90)90078-C

R. J. Blakely, Fourier-Domain Modeling, Potential Theory in Gravity and Magnetic Applications, pp.258-311, 1996.
DOI : 10.1017/CBO9780511549816.012

U. Bleil and N. Petersen, Variations in magnetization intensity and low-temperature titanomagnetite oxidation of ocean floor basalts, Nature, vol.29, issue.5899, pp.384-388, 1983.
DOI : 10.1038/301384a0

A. J. Calvert, Seismic evidence for a magma chamber beneath the slow-spreading Mid-Atlantic Ridge, Nature, vol.377, issue.6548, pp.410-414, 1995.
DOI : 10.1038/377410a0

J. P. Canales, R. S. Detrick, J. Lin, and J. A. Collins, Crustal and upper mantle seismic structure beneath the rift mountains and across a nontransform offset at the Mid-Atlantic Ridge (35??N), Journal of Geophysical Research: Solid Earth, vol.108, issue.17, pp.2699-2719, 2000.
DOI : 10.1029/1999JB900379

M. Cannat, Emplacement of mantle rocks in the seafloor at mid-ocean ridges, Journal of Geophysical Research: Solid Earth, vol.312, issue.109, pp.4163-4172, 1993.
DOI : 10.1029/92JB02221

M. Cannat, Thin crust, ultramafic exposures, and rugged faulting patterns at the Mid-Atlantic Ridge (22?????24??N), Geology, vol.23, issue.1, pp.49-52, 1995.
DOI : 10.1130/0091-7613(1995)023<0049:TCUEAR>2.3.CO;2

L. J. Caruso and J. V. Chernosky, The stability of lizardite, Can. Min, vol.17, pp.757-769, 1979.

W. P. Chen and P. Molnar, Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere, Journal of Geophysical Research: Solid Earth, vol.88, issue.B5, pp.4183-4214, 1983.
DOI : 10.1029/JB088iB05p04183

N. I. Christensen, Elasticity of ultrabasic rocks, Journal of Geophysical Research, vol.65, issue.22, pp.5921-5931, 1966.
DOI : 10.1029/JZ071i024p05921

R. S. Detrick, H. D. Needham, and V. Renard, Gravity anomalies and crustal thickness variations along the Mid-Atlantic Ridge between 33??N and 40??N, Journal of Geophysical Research: Solid Earth, vol.71, issue.44, pp.3767-3787, 1995.
DOI : 10.1029/94JB02649

D. J. Dunlop and M. Prévot, Magnetic properties and opaque mineralogy of drilled submarine intrusive rocks, Geophysical Journal International, vol.69, issue.3, pp.763-802, 1982.
DOI : 10.1111/j.1365-246X.1982.tb02774.x

J. Dyment and J. Arkani-hamed, Spreading-rate-dependent magnetization of the oceanic lithosphere inferred from the anomalous skewness of marine magnetic anomalies, Geophysical Journal International, vol.121, issue.3, pp.789-804, 1995.
DOI : 10.1111/j.1365-246X.1995.tb06439.x

J. Dyment, J. Arkani-hamed, and A. Ghods, Contribution of serpentinized ultramafics to marine magnetic anomalies at slow and intermediate spreading centres: insights from the shape of the anomalies, Geophysical Journal International, vol.129, issue.3, pp.691-701, 1997.
DOI : 10.1111/j.1365-246X.1997.tb04504.x

A. T. Fisher, T. N. Becker, M. G. Narasimhan, and M. J. Mottl, Passive, off-axis convection through the southern flank of the Costa Rica Rift, Journal of Geophysical Research, vol.38, issue.52, pp.9343-9370, 1990.
DOI : 10.1029/JB095iB06p09343

A. T. Fisher, K. Becker, and T. N. Narasimhan, Off-axis hydrothermal circulation: Parametric tests of a refined model of processes at Deep Sea Drilling Project/Ocean Drilling Program site 504, Journal of Geophysical Research: Solid Earth, vol.69, issue.B2, pp.3097-3121, 1994.
DOI : 10.1029/93JB02741

T. J. Francis, Serpentinization faults and their role in the tectonics of slow spreading ridges, Journal of Geophysical Research, vol.23, issue.B12, pp.616-627, 1981.
DOI : 10.1029/JB086iB12p11616

J. S. Gee, R. M. Lawrence, and S. D. Hurst, Remanence characteristics of gabbros from the MARK area: implications for crustal magnetization, Proc. Ocean Drill. Program Sci. Results, pp.429-436, 1997.
DOI : 10.2973/odp.proc.sr.153.042.1997

P. Gente, Characteristics and evolution of the segmentation of the Mid-Atlantic Ridge between 20??N and 24??N during the last 10 million years, Earth and Planetary Science Letters, vol.129, issue.1-4, pp.55-71, 1995.
DOI : 10.1016/0012-821X(94)00233-O

N. R. Grindlay, P. J. Fox, and P. R. Vogt, Morphology and tectonics of the Mid-Atlantic Ridge (25?????27??30???S) from Sea Beam and magnetic data, Journal of Geophysical Research, vol.79, issue.B5, pp.6983-7010, 1992.
DOI : 10.1029/91JB02981

E. E. Hooft, R. S. Detrick, D. R. Toomey, J. A. Collins, and J. Lin, Crustal thickness and structure along three contrasting spreading segments of the Mid-Atlantic Ridge, 33, J. geophys. Res, vol.105, pp.5-35, 2000.

H. Horen and C. Fleutelot, Highly magnetized and differentiated basalts at the 18?19 ? S propagating spreading centre in the North Fidji Basin, Marine Geophysical Researches, vol.20, issue.2, pp.129-137, 1998.
DOI : 10.1023/A:1004457812905

H. Horen, M. Zamora, and G. Dubuisson, Seismic waves velocities and anisotropy in serpentinized peridotites from xigaze ophiolite: Abundance of serpentine in slow spreading ridge, Geophysical Research Letters, vol.97, issue.109, pp.9-12, 1996.
DOI : 10.1029/95GL03594

E. Irving, The Mid-Atlantic Ridge at 45 ? N, XIV, oxidation and magnetic properties of basalts: review and discussion, Can, J. Earth Sci, vol.7, pp.1528-1538, 1970.

H. P. Johnson and J. E. Pariso, Variations in oceanic crustal magnetization: Systematic changes in the last 160 million years, Journal of Geophysical Research: Solid Earth, vol.94, issue.52, pp.435-445, 1993.
DOI : 10.1029/92JB01322

T. Juteau, M. Cannat, and Y. Lagabrielle, Serpentinized peridotites in the upper oceanic crust away from transform zones: a comparison of the results of previous DSDP and ODP legs, Proc. Ocean Drill. Program Sci. Results, pp.106-109, 1990.

D. V. Kent, B. M. Honnores, N. D. Opdyke, and P. J. Fox, Magnetic properties of dredged oceanic gabbros and the source of marine magnetic anomalies, Geophysical Journal International, vol.55, issue.3, pp.513-537, 1978.
DOI : 10.1111/j.1365-246X.1978.tb05925.x

L. S. Kong, S. C. Solomon, and G. M. Purdy, Microearthquake Characteristics of a Mid-Ocean Ridge along-axis high, Journal of Geophysical Research: Solid Earth, vol.159, issue.B2, pp.1659-1685, 1992.
DOI : 10.1029/91JB02566

B. Y. Kuo and D. W. Forsyth, Gravity anomalies of the ridge-transform system in the South Atlantic between 31 and 34.5??? S: Upwelling centers and variations in crustal thickness, Marine Geophysical Researches, vol.85, issue.3-4, pp.205-232, 1988.
DOI : 10.1007/BF00310065

L. Douaran, S. Francheteau, and J. , Axial depth anomalies from 10 to 50?? north along the Mid-Atlantic Ridge: correlation with other mantle properties, Earth and Planetary Science Letters, vol.54, issue.1, pp.29-47, 1981.
DOI : 10.1016/0012-821X(81)90066-2

J. Lin and J. Phipps-morgan, The spreading rate dependence of three-dimensional mid-ocean ridge gravity structure, Geophysical Research Letters, vol.71, issue.1, pp.13-16, 1992.
DOI : 10.1029/91GL03041

J. Lin, G. M. Purdy, H. Schouten, J. C. Sempéré, and C. Zervas, Evidence from gravity data for focused magmatic accretion along the Mid-Atlantic Ridge, Nature, vol.344, issue.6267, pp.627-632, 1990.
DOI : 10.1038/344627a0

K. C. Macdonald, Near-bottom magnetic anomalies, asymmetric spreading, oblique spreading, and tectonics of the Mid-Atlantic Ridge near lat 37??N, Geological Society of America Bulletin, vol.88, issue.4, pp.541-555, 1977.
DOI : 10.1130/0016-7606(1977)88<541:NMAASO>2.0.CO;2

A. H. Macdonald and W. S. Fyfe, Rate of serpentinization in seafloor environments, Tectonophysics, vol.116, issue.1-2, pp.123-135, 1984.
DOI : 10.1016/0040-1951(85)90225-2

K. C. Macdonald, J. C. Sempéré, and P. J. Fox, East Pacific Rise from Siquieros to Orozco Fractures Zones: along-strike continuity of axial neovolcanic zone and structure and evolution of overlapping spreading centers, J. geophys. Res, vol.3, pp.211-215, 1984.

K. C. Macdonald, J. C. Sempéré, and P. J. Fox, Reply: The debate concerning overlapping spreading centers and Mid-Ocean Ridge processes, Journal of Geophysical Research, vol.29, issue.B10, pp.10-501, 1986.
DOI : 10.1029/JB091iB10p10501

S. G. Magde and D. W. Sparks, Three-dimensional mantle upwelling, melt generation, and melt migration beneath segment slow spreading ridges, Journal of Geophysical Research: Solid Earth, vol.312, issue.17, pp.571-591, 1997.
DOI : 10.1029/97JB01278

S. G. Magde, D. W. Sparks, and R. D. Detrick, The relationship between buoyant mantle flow, melt migration, and gravity bull's eyes at the Mid-Atlantic Ridge between 33??N and 35??N, Earth and Planetary Science Letters, vol.148, issue.1-2, pp.59-67, 1997.
DOI : 10.1016/S0012-821X(97)00039-3

M. Marshall and A. Cox, Magnetic changes in pillow basalt due to sea floor weathering, Journal of Geophysical Research, vol.20, issue.32, pp.6459-6469, 1972.
DOI : 10.1029/JB077i032p06459

D. Mckenzie, The Generation and Compaction of Partially Molten Rock, Journal of Petrology, vol.25, issue.3, pp.713-765, 1984.
DOI : 10.1093/petrology/25.3.713

D. J. Miller and N. I. Christensen, Seismic velocities of lower crustal and upper mantle rocks from the slow-spreading Mid-Atlantic Ridge, south of the Kane Transform Zone (MARK), Proc. Ocean Drill. Program Sci. Results, pp.437-454, 1997.
DOI : 10.2973/odp.proc.sr.153.043.1997

K. A. Nazarova, Serpentinized peridotites as a possible source for oceanic magnetic anomalies, Marine Geophysical Researches, vol.87, issue.6, pp.455-462, 1994.
DOI : 10.1007/BF01270519

A. Nicolas, Structure of Ophiolites and Dynamics of Oceanic Lithosphere, p.367, 1989.
DOI : 10.1007/978-94-009-2374-4

Y. Niu and R. Batiza, Magmatic processes at a slow spreading ridge segment: 26??S Mid-Atlantic Ridge, Journal of Geophysical Research: Solid Earth, vol.312, issue.B10, pp.719-738, 1994.
DOI : 10.1029/94JB01663

J. Noye and J. Noyes, Finite difference techniques for partial differential equations , in Computational Techniques for Differential Equations, pp.95-353, 1984.

O. Oufi, M. Cannat, and H. Horen, Magnetic properties of variably serpentinized abyssal peridotites, Journal of Geophysical Research, vol.46, issue.14, pp.1-20, 2002.
DOI : 10.1029/2001JB000549

J. E. Pariso and H. P. Johnson, Do lower crustal rocks record reversals of the Earth's magnetic field? Magnetic petrology of oceanic gabbros from Ocean Drilling Program hole 735B, Journal of Geophysical Research, vol.17, issue.B9, pp.16-29, 1993.
DOI : 10.1029/93JB00933

J. E. Pariso, C. Rommevaux, and J. C. Sempéré, Three-dimensional inversion of marine magnetic anomalies: Implications for crustal accretion along the Mid-Atlantic Ridge (28????31???30? N), Marine Geophysical Researches, vol.72, issue.1, pp.85-101, 1996.
DOI : 10.1007/BF00286204

R. A. Pockalny, R. S. Detrick, and P. J. Fox, Morphology and tectonics of the Kane Transform from Sea Beam bathymetry data, Journal of Geophysical Research, vol.23, issue.B4, pp.3179-3193, 1988.
DOI : 10.1029/JB093iB04p03179

R. A. Pockalny, A. Smith, and P. Gente, Spatial and temporal variability of crustal magnetization of a slowly spreading ridge: Mid-Atlantic Ridge (20????24??? N), Marine Geophysical Researches, vol.97, issue.109, pp.301-320, 1995.
DOI : 10.1007/BF01203467

J. P. Pozzi and G. Dubuisson, High temperature viscous magnetization of oceanic deep crustal- and mantle-rocks as a partial source for MAGSAT magnetic anomalies, Geophysical Research Letters, vol.6, issue.1, pp.21-24, 1992.
DOI : 10.1029/91GL02796

M. Ravilly, J. Dyment, P. Gente, and R. Thibaud, Axial magnetic anomaly amplitude along the Mid-Atlantic Ridge between 20 ? N and 40 ? N, J. geophys. Res, vol.103, pp.24-201, 1998.

C. A. Raymond and J. L. Labrecque, Magnetization of the oceanic crust: Thermoremanent magnetization of chemical remanent magnetization?, Journal of Geophysical Research, vol.19, issue.B8, pp.8077-8088, 1987.
DOI : 10.1029/JB092iB08p08077

P. A. Rona, Magnetic signatures of hydrothermal alteration and volcanogenic mineral deposits in oceanic crust, Journal of Volcanology and Geothermal Research, vol.3, issue.1-2, pp.219-225, 1978.
DOI : 10.1016/0377-0273(78)90010-0

D. R. Scott and D. J. Stevenson, A self-consistent model of melting, magma migration and buoyancy-driven circulation beneath mid-ocean ridges, Journal of Geophysical Research: Solid Earth, vol.66, issue.B3, pp.2973-2988, 1989.
DOI : 10.1029/JB094iB03p02973

J. C. Sempéré, G. M. Purdy, and H. Schouten, Segmentation of the Mid-Atlantic Ridge between 24?? N and 30??40' N, Nature, vol.344, issue.6265, pp.427-431, 1990.
DOI : 10.1038/344427a0

J. C. Sempéré, J. Lin, H. S. Brown, H. Schouten, and G. M. Purdy, Segmentation and morphotectonic variations along a slow-spreading center: the Mid-Atlantic Ridge, Mar. geophys. Res, pp.153-200, 1993.

J. M. Sinton and R. S. Detrick, Mid-ocean ridge magma chambers, Journal of Geophysical Research, vol.3, issue.3, pp.197-216, 1992.
DOI : 10.1029/91JB02508

R. Thibaud, P. Gente, and M. Maia, A systematic analysis of the Mid-Atlantic Ridge morphology and gravity between 15 ? N and 40 ? N: constraints of the thermal structure, J. geophys. Res, vol.103, pp.24-223, 1998.

C. Tisseau and T. Tonnerre, Non Steady-State Thermal Model of Spreading Ridges: Implications for Melt Generation and Mantle Outcrops, Mantle and Lower Crust Exposed in Ridges and Ophiolites, pp.181-214, 1995.
DOI : 10.1007/978-94-015-8585-9_8

M. A. Tivey and B. E. Tucholke, Magnetization of 0?29 Ma ocean crust on the Mid-Atlantic Ridge, 25 ? 30 to 27 ? 10 N, J. geophys. Res, vol.103, pp.17-807, 1998.

M. Tolstoy, A. J. Harding, and J. A. Orcutt, Crustal Thickness on the Mid-Atlantic Ridge: Bull's-Eye Gravity Anomalies and Focused Accretion, Science, vol.262, issue.5134, pp.726-729, 1993.
DOI : 10.1126/science.262.5134.726

D. R. Toomey, S. C. Solomon, G. M. Purdy, and M. H. Murray, Microearthquakes beneath the Median Valley of the Mid-Atlantic Ridge near 23??N: Hypocenters and focal mechanisms, Journal of Geophysical Research, vol.73, issue.B7, pp.5443-5458, 1985.
DOI : 10.1029/JB090iB07p05443

D. R. Toomey, S. C. Solomon, and G. M. Purdy, Microearthquakes beneath Median Valley of Mid-Atlantic Ridge near 23??N: Tomography and tectonics, Journal of Geophysical Research, vol.10, issue.4, pp.9093-9112, 1988.
DOI : 10.1029/JB093iB08p09093

D. R. Toomey, G. M. Purdy, A. H. Barclay, C. J. Wolfe, and S. C. Solomon, FARA microearthquakes experiments IV: implications of Mid- Atlantic Ridge seismicity for models of young oceanic lithosphere, AGU Fall meeting, p.601, 1993.

F. Trutin, Modélisation 3D de l'´ evolution dans le temps de la structure thermique de l'axe d'une dorsale océanique, 1995.

B. E. Tucholke and H. Schouten, Kane Fracture Zone, Marine Geophysical Researches, vol.312, issue.1-2, pp.1-39, 1988.
DOI : 10.1007/BF02424659

C. M. Weiland, K. C. Macdonald, and N. R. Grindlay, Ridge segmentation and the magnetic structure of the Southern Mid-Atlantic Ridge 26??S and 31??-35??S: Implications for magmatic processes at slow spreading centers, Journal of Geophysical Research: Solid Earth, vol.97, issue.16, pp.8055-8073, 1996.
DOI : 10.1029/95JB03535

J. A. Whitehead, H. J. Dick, and H. Schouten, A mechanism for magmatic accretion under spreading centers, Nature, pp.312-146, 1984.

C. J. Wolfe, G. M. Purdy, D. R. Toomey, and S. C. Solomon, Microearthquake characteristics and crustal velocity structure at 29 ? N on the Mid-Atlantic Ridge: the architecture of a slow spreading ridge, J. geophys. Res, vol.100, pp.24-449, 1995.

A. L. Wooldridge, C. G. Harrison, M. A. Tivey, and P. A. Rona, Magnetic modeling near selected areas of hydrothermal activity on the Mid-Atlantic and Gorda Ridges, Journal of Geophysical Research, vol.159, issue.2, pp.911-921, 1992.
DOI : 10.1029/92JB00605

N. N. Yanenko, Méthodè a pas fractionnaire Résolution desProbì emes Polydimensionnels de Physique Mathématique, p.205, 1968.