References

Solid Earth

1869-9529

Copernicus Publications

Göttingen, Germany

10.5194/se-5-339-2014

Magnetic signature of large exhumed mantle domains of the Southwest Indian Ridge – results from a deep-tow geophysical survey over 0 to 11 Ma old seafloor

Bronner

¹ Sauter

¹ Munschy

¹ Carlut

² Searle

³ Cannat

² Manatschal

Université de Strasbourg, Institut de Physique du Globe de Strasbourg (IPGS) UMR CNRS, Strasbourg, France

Sorbonne Paris Cité Université Paris Diderot, Institut de Physique du Globe de Paris (IPGP), UMR CNRS, Paris, France

Durham University, Department of Earth Sciences, Durham, UK

19 05 2014

5 1 339 354

2014

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://se.copernicus.org/articles/5/339/2014/se-5-339-2014.html

The full text article is available as a PDF file from https://se.copernicus.org/articles/5/339/2014/se-5-339-2014.pdf

We investigate the magnetic signature of ultramafic seafloor in the eastern part of the Southwest Indian Ridge (SWIR). There, detachment faulting, continuous over 11 Myr, exhumed large areas of mantle-derived rocks. These exhumed mantle domains occur in the form of a smooth rounded topography with broad ridges locally covered by a thin highly discontinuous volcanic carapace. We present high-resolution data combining deep-tow magnetics, side-scan sonar images and dredged samples collected within two exhumed mantle domains between 62° E and 65° E. We show that, despite an ultra-slow spreading rate, volcanic areas within robust magmatic segments are characterized by well-defined seafloor spreading anomalies. By contrast, the exhumed mantle domains, including a few thin volcanic patches, reveal a weak and highly variable magnetic pattern. The analysis of the magnetic properties of the dredged samples and careful comparison between the nature of the seafloor, the deep-tow magnetic anomalies and the seafloor equivalent magnetization suggest that the serpentinized peridotites do not carry a sufficiently stable remanent magnetization to produce seafloor spreading magnetic anomalies in exhumed mantle domains.

References 1

Bronner, A., Sauter, D., Manatschal, G., Peron-Pinvidic, G., and Munschy, M.: Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins, Nat. Geosci., 4, 549–553, <a href="http://dx.doi.org/10.1038/ngeo1201">https://doi.org/10.1038/ngeo1201</a>, 2011.

Bronner, A., Sauter, D., Manatschal, G., Peron-Pinvidic, G., and Munschy, M.: Reply to "problematic plate reconstruction", Nat. Geosci, 5, 677–677, <a href="http://dx.doi.org/10.1038/ngeo1597">https://doi.org/10.1038/ngeo1597</a>, 2012.

Bronner, A., Munschy, M., Sauter, D., Carlut, J., Searle, R., and Maineult, A.: Deep-tow 3c magnetic measurement: solutions for calibration and interpretation, Geophysics, 78, J15–J23, <a href="http://dx.doi.org/10.1190/geo2012-0214.1">https://doi.org/10.1190/geo2012-0214.1</a>, 2013.

Buck, W. R., Lavier, L. L., and Poliakov, A. N. B.: Modes of faulting at mid-ocean ridges, Nature, 434, 719–723, 2005.

Cann, J. R., Blackman, D. K., Smith, D. K., McAllister, E., Janssen, B., Mello, S., Avgerinos, E., Pascoe, A. R., and Escartin, J.: Corrugated slip surfaces formed at ridge-transform intersections on the mid-atlantic ridge, Nature, 385, 329–332, 1997.

Cannat, M., Bideau, D., and Bougault, H.: Serpentinized peridotites and gabbros in the mid-atlantic ridge axial valley at 15°37' N and 16°52' N, Earth Planet. Sc. Lett., 109, 87–106, 1992.

Cannat, M., Mevel, C., Maia, M., Deplus, C., Durand, C., Gente, P., Agrinier, P., Belarouchi, A., Dubuisson, G., Humler, E., and Reynolds, J.: Thin crust, ultramafic exposures, and rugged faulting patterns at the mid-atlantic ridge (22–24° N), Geology, 23, 49–52, 1995.

Cannat, M., Rommevaux-Jestin, C., Sauter, D., Deplus, C., and Mendel, V.: Formation of the axial relief at the very slow spreading southwest indian ridge (49–69° E), J. Geophys. Res., 104, 22825–22843, 1999.

Cannat, M., Sauter, D., Mendel, V., Ruellan, E., Okino, K., Escartin, J., Combier, V., and Baala, M.: Modes of seafloor generation at a melt-poor ultraslow-spreading ridge, Geology, 34, 605–608, <a href="http://dx.doi.org/10.1130/G22486.1">https://doi.org/10.1130/G22486.1</a>, 2006.

Cannat, M., Sauter, D., Bezos, A., Meyzen, C., Humler, E., and Le Rigoleur, M.: Spreading rate, spreading obliquity, and melt supply at the ultraslow spreading southwest indian ridge, Geochem. Geophy. Geosy., 9, Q04002, <a href="http://dx.doi.org/10.1029/2007gc001676">https://doi.org/10.1029/2007gc001676</a>, 2008.

Chian, D., Louden, K. E., Minshull, T. A., and Whitmarsh, R. B.: Deep structure of the ocean-continent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect, J. Geophys. Res.-Sol. Ea., 104, 7443–7462, 1999.

Dampney, C.: The equivalent source technique, Geophysics, 34, 39–53, <a href="http://dx.doi.org/10.1190/1.1439996">https://doi.org/10.1190/1.1439996</a>, 1969.

Dean, S. M., Minshull, T. A., and Whitmarsh, R. B.: Seismic constraints on the three-dimensional geometry of low-angle intracrustal reflectors in the southern iberia abyssal plain, Geophys. J. Int., 175, 571–586, 2008.

Dunlop, D. J. and Prévot, M.: Magnetic properties and opaque mineralogy of drilled submarine intrusive rocks, Geophys. J. Roy. Astr. S., 69, 763–802, <a href="http://dx.doi.org/10.1111/j.1365-246X.1982.tb02774.x">https://doi.org/10.1111/j.1365-246X.1982.tb02774.x</a>, 1982.

Flewellen, C., Millard, N., and Rouse, I.: Tobi, a vehicle for deep ocean survey, Electron. Commun. Eng., 5, 85–93, 1993.

Gee, J. S. and Kent, D. V.: Source of oceanic magnetic anomalies and the geomagnetic polarity timescale, in: Treatise on Geophysics, edited by: Schubert, G., Elsevier, 455–507, 2007.

Georgen, J. E., Lin, J., and Dick, H. J. B.: Evidence from gravity anomalies for interactions of the marion and bouvet hotspots with the southwest indian ridge: effects of transform offsets, Earth Planet. Sc. Lett., 187, 283–300, 2001.

Harrison, C.: Marine magnetic anomalies-the origin of the stripes, Annu. Rev. Earth Pl. Sc., 15, 505–543, 1987.

Hosford, A., Tivey, M., Matsumoto, T., Dick, H., Schouten, H., and Kinoshita, H.: Crustal magnetization and accretion at the southwest indian ridge near the atlantis ii fracture zone, 0–25 ma, J. Geophys. Res.-Sol. Ea., 108, 2169, <a href="http://dx.doi.org/10.1029/2001jb000604">https://doi.org/10.1029/2001jb000604</a>, 2003.

Isezaki, N.: A new shipboard three-component magnetometer, Geophysics, 51, 1992–1998, 1986.

Karson, J. A., Thompson, G., Humphris, S. E., Edmon, J. M., Bryan, W. B., Brown, J. B., Winters, A. T., Pockalny, R. A., Casey, J. F., Campbell, A. C., Klinkhammer, G. P., Palmer, M. R., Kinzler, R. J., and Sulanowska, M. M.: Along-axis variations in seafloor spreading in the mark area, Nature, 328, 681–685, 1987.

Korenaga, J.: Comprehensive analysis of marine magnetic vector anomalies, J. Geophys. Res., 100, 365–378, <a href="http://dx.doi.org/10.1029/94jb02596">https://doi.org/10.1029/94jb02596</a>, 1995.

Maffione, M., Morris, A., Plümper, O., and van Hinsbergen, D. J. J.: Magnetic properties of variably serpentinized peridotites and their implication for the evolution of oceanic core complexes, Geochem. Geophy. Geosy., n/a-n/a, <a href="http://dx.doi.org/10.1002/2013gc004993">https://doi.org/10.1002/2013gc004993</a>, 2014.

Mallows, C. and Searle, R. C.: A geophysical study of oceanic core complexes and surrounding terrain, mid-atlantic ridge 13°n–14°n, Geochem. Geophy. Geosy., 13, Q0AG08, <a href="http://dx.doi.org/10.1029/2012gc004075">https://doi.org/10.1029/2012gc004075</a>, 2012.

Marshall, M. and Cox, A.: Magnetism of pillow basalts and their petrology, Geol. Soc. Am. Bull., 82, 537–552, 1971.

Mendel, V., Munschy, M., and Sauter, D.: Modmag, a matlab program to model marine magnetic anomalies, Comput. Geosci., 31, 589–597, 2005.

Meyzen, C. M., Toplis, M. J., Humler, E., Ludden, J. N., and Mevel, C.: A discontinuity in mantle composition beneath the southwest indian ridge, Nature, 421, 731–733, <a href="http://dx.doi.org/10.1038/nature01424">https://doi.org/10.1038/nature01424</a>, 2003.

Minshull, T. A., Muller, M. R., Robinson, C. J., White, R. S., and Bickle, M. J.: Is the oceanic moho a serpentinization front?, Geological Society, London, Special Publications, 148, 71–80, <a href="http://dx.doi.org/10.1144/gsl.sp.1998.148.01.05">https://doi.org/10.1144/gsl.sp.1998.148.01.05</a>, 1998.

Minshull, T. A., Muller, M. R., and White, R. S.: Crustal structure of the southwest indian ridge at 66° E: Seismic constraints, Geophys. J. Int., 166, 135–147, 2006.

Nazarova, K. A.: Serpentinized peridotites as a possible source for oceanic magnetic anomalies, Mar. Geophys. Res., 16, 455–462, 1994.

Oufi, O., Cannat, M., and Horen, H.: Magnetic properties of variably serpentinized abyssal peridotites, J. Geophys. Res., 107, 2095, <a href="http://dx.doi.org/10.1029/2001JB000549">https://doi.org/10.1029/2001JB000549</a>, 2002.

Pariso, J. E. and Johnson, H. P.: Do layer 3 rocks make a significant contribution to marine magnetic anomalies? In situ magnetization of gabbros at ocean drilling program hole 735 b, J. Geophys. Res., 98, 16033–16052, 1993.

Patriat, P., Sauter, D., Munschy, M., and Parson, L.: A survey of the southwest indian ridge axis between atlantis ii fracture zone and the indian ocean triple junction: regional setting and large scale segmentation, Mar. Geophys. Res., 19, 457–480, <a href="http://dx.doi.org/10.1023/a:1004312623534">https://doi.org/10.1023/a:1004312623534</a>, 1997.

Patriat, P., Sloan, H., and Sauter, D.: From slow to ultraslow: a previously undetected event at the southwest indian ridge at ca. 24 Ma, Geology, 36, 207–210, <a href="http://dx.doi.org/10.1130/G24270a.1">https://doi.org/10.1130/G24270a.1</a>, 2008.

Reston, T. J. and McDermott, K. G.: Successive detachment faults and mantle unroofing at magma-poor rifted margins, Geology, 39, 1071–1074, <a href="http://dx.doi.org/10.1130/g32428.1">https://doi.org/10.1130/g32428.1</a>, 2011.

Russell, S. M. and Whitmarsh, R. B.: Magmatism at the west iberia non-volcanic rifted continental margin: evidence from analyses of magnetic anomalies, Geophys. J. Int., 154, 706–730, <a href="http://dx.doi.org/10.1046/j.1365-246X.2003.01999.x">https://doi.org/10.1046/j.1365-246X.2003.01999.x</a>, 2003.

Sauter, D., Carton, H., Mendel, V., Munschy, M., Rommevaux-Jestin, C., Schott, J.-J., and Whitechurch, H.: Ridge segmentation and the magnetic structure of the southwest indian ridge (at 55°30'e, 55°30'e and 66°20'e): Implications for magmatic processes at ultraslow-spreading centers, Geochem. Geophy. Geosy., 5, Q05K08, <a href="http://dx.doi.org/10.1029/2003GC000581">https://doi.org/10.1029/2003GC000581</a>, 2004.

Sauter, D., Cannat, M., and Mendel, V.: Magnetization of 0–26.5 ma seafloor at the ultraslow spreading southwest indian ridge 61–67° E, Geochem. Geophy. Geosy., 9, Q04023, <a href="http://dx.doi.org/10.1029/2007GC001764">https://doi.org/10.1029/2007GC001764</a>, 2008.

Sauter, D., Sloan, H., Cannat, M., Goff, J., Patriat, P., Schaming, M., and Roest, W. R.: From slow to ultra-slow: How does spreading rate affect seafloor roughness and crustal thickness?, Geology, 39, 911–914, 2011.

Sauter, D., Cannat, M., Roumejon, S., Andreani, M., Birot, D., Bronner, A., Brunelli, D., Carlut, J., Delacour, A., Guyader, V., MacLeod, C. J., Manatschal, G., Mendel, V., Menez, B., Pasini, V., Ruellan, E., and Searle, R.: Continuous exhumation of mantle-derived rocks at the southwest indian ridge for 11 million years, Nat. Geosci., 6, 314–320, 2013.

Searle, R. C. and Bralee, A.: Asymmetric generation of oceanic crust at the ultra-slow spreading southwest indian ridge, 64° E, Geochem. Geophy. Geosy., 8, Q05015, <a href="http://dx.doi.org/10.1029/2006GC001529">https://doi.org/10.1029/2006GC001529</a>, 2007.

Seyler, M., Cannat, M., and Mevel, C.: Evidence for major-element heterogeneity in the mantle source of abyssal peridotites from the southwest indian ridge (52 ° to 68 ° E), Geochem. Geophy. Geosy., 4, 9101, <a href="http://dx.doi.org/10.1029/2002gc000305">https://doi.org/10.1029/2002gc000305</a>, 2003.

Sibuet, J. C., Srivastava, S., and Manatschal, G.: Exhumed mantle-forming transitional crust in the newfoundland-iberia rift and associated magnetic anomalies, J. Geophys. Res.-Sol. Ea., 112, B06105, <a href="http://dx.doi.org/10.1029/2005jb003856">https://doi.org/10.1029/2005jb003856</a>, 2007.

Srivastava, S. P., Sibuet, J. C., Cande, S., Roest, W. R., and Reid, I. D.: Magnetic evidence for slow seafloor spreading during the formation of the newfoundland and iberian margins, Earth Planet. Sc. Lett., 182, 61–76, <a href="http://dx.doi.org/10.1016/s0012-821x(00)00231-4">https://doi.org/10.1016/s0012-821x(00)00231-4</a>, 2000.

Tisseau, J. and Patriat, P.: Identification des anomalies magnétiques sur les dorsales à faible taux d'expansion: Méthode des taux fictifs, Earth Planet. Sc. Lett., 52, 381–396, <a href="http://dx.doi.org/10.1016/0012-821X(81)90191-6">https://doi.org/10.1016/0012-821X(81)90191-6</a>, 1981.

Tucholke, B. E., and Sibuet, J.-C.: Leg 210 synthesis: Tectonic, magmatic, and sedimentary evolution of the newfoundland-iberia rift, in: Proceedings of the ocean drilling program, scientific results, edited by: Tucholke, B. E., Sibuet, J.-C., and Klaus, A., Ocean Drilling Program, College Station, TX, 1-56, 2007.

Tucholke, B. E. and Sibuet, J.-C.: Leg 210 synthesis: tectonic, magmatic, and sedimentary evolution of the newfoundland-iberia rift, in: Proceedings of the ocean drilling program, scientific results, edited by: Tucholke, B. E., Sibuet, J.-C., and Klaus, A., Ocean Drilling Program, College Station, TX, 1–56, 2007.

Tucholke, B. E. and Sibuet, J.-C.: Problematic plate reconstruction, Nat. Geosci., 5, 676–677, <a href="http://dx.doi.org/10.1038/ngeo1596">https://doi.org/10.1038/ngeo1596</a>, 2012.

Zhao, X., Turrin, B. D., Jackson, M., and Solheid, P.: Data report: Paleomagnetic and rock magnetic characterization of rocks recovered from leg 173 sites., in: Proc. Odp, sci. Results,, edited by: Beslier, M.-O., Whitmarsh, R. B., Wallace, P. J., and Girardeau, J. (Ocean Drilling Program), College Station, TX, 1–34, 2001.