Marine Geophysical Researches

, Volume 21, Issue 1–2, pp 87–119 | Cite as

Accretionary processes in the axial valley of the Mid-Atlantic Ridge 27° N–30° N from TOBI side-scan sonar images

  • Anne Briais
  • Heather Sloan
  • Lindsay M. Parson
  • Bramley J. Murton


We analyse TOBI side-scan sonar images collected during Charles Darwin cruise CD76 in the axial valley of the Mid-Atlantic Ridge (MAR) between 27° N and 30° N (Atlantis Transform Fault). Mosaics of the two side-scan sonar swaths provide a continuous image of the axial valley and the inner valley walls along more than six second-order segments of the MAR. Tectonic and volcanic analyses reveal a high-degree intra-segment and inter-segment variability. We distinguish three types of volcanic morphologies: hummocky volcanoes or volcanic ridges, smooth, flat-topped volcanoes, and lava flows. We observe that the variations in the tectonics from one segment to another are associated with variations in the distribution of the volcanic morphologies. Some segments have more smooth volcanoes near their ends and in the discontinuities than near their mid-point, and large, hummocky axial volcanic ridges. Their tectonic deformation is usually limited to the edges of the axial valley near the inner valley walls. Other segments have smooth volcanoes distributed along their length, small axial volcanic ridges, and their axial valley floor is affected by numerous faults and fissures. We propose a model of volcano-tectonic cycles in which smooth volcanoes and lava flows are built during phases of high magmatic flux. Hummocky volcanic ridges are constructed more progressively, by extraction of magma from pockets located preferentially beneath the centre of the segments, during phases of low magma input. These cycles might result from pulses in melt migration from the mantle. Melt arrival would lead to the rapid emplacement of smooth-textured volcanic terrains, and would leave magma pockets, mostly beneath the centre of the segments where most melt is produced. During the end of the volcanic cycle magma would be extracted from these reservoirs through dikes with a low magma pressure, building hummocky volcanic ridges at low effusion rates. In extreme cases, this volcanic phase would be followed by amagmatic extension until a new magma pulse arrives from the mantle.

tectonic faulting volcanic constructions oceanic crust side-scan sonar images 


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  1. Allerton, S. and MacLeod, C.J. 1998, Fault-controlled magma transport through the mantle lithosphere at slow-spreading ridges, in R.A. Mills, and K. Harrison (eds), Modern Ocean Floor Processes and the Geological Record, Spec. Pub. 148: Geol. Soc., London, pp. 29–42.Google Scholar
  2. Allerton, S., Murton, B.J., Searle, R.C. and Jones, M. 1995, Extensional faulting and segmentation of the Mid-Atlantic Ridge north of the Kane fracture zone (24°00′ N to 24°40′ N), Mar. Geophys. Res. 17: 37–61.Google Scholar
  3. Allerton, S., Searle, R.C. and Murton, B.J. 1996, Bathymetric segmentation and faulting on the Mid-Atlantic Ridge, 24°00′ N to 24°40′ N, in C.J. MacLeod, P.A. Tyler, and C.L. Walker (eds), Tectonic, Magmatic, Hydrothermal and Biological Segmentation of Mid-Ocean Ridges, No. 118, Geol. Soc. Spec. Pub., pp. 49–60.Google Scholar
  4. Appelgate, B. and Shor, A.N. 1994, The northern Mid-Atlantic and Reykjanes Ridges: Spreading center morphology between 55°50′ N and 63°00′ N, J. Geophys. Res. 99: 17,935–17,956.Google Scholar
  5. Arcyana, 1975, Transform fault and rift valley from bathyscaph and diving saucer, Science 190: 108–116.Google Scholar
  6. Ballard, R.D., Holcomb, R.T. and van Andel, T.H. 1979, The Galapagos Rift at 86 W: 3. Sheet flows, collapse pits, and lava lakes of the rift valley, J. Geophys. Res. 84: 5407–5422.Google Scholar
  7. Ballard, R.D. and Van Andel, T.J. 1977, Morphology and tectonics of the inner rift valley at lat. 36° 50′ N on the Mid-Atlantic Ridge, Geol. Soc. Amer. Bull. 88: 507–530.Google Scholar
  8. Batiza, R., Melson, W. and O'Hearn, T. 1988, Simple magma supply geometry inferred beneath a segment of the Mid-Atlantic Ridge, Nature 335: 428–431.Google Scholar
  9. Bruce, P.M. and Huppert, H.E. 1989, Thermal control of basaltic fissure eruptions, Nature 342: 665–667.Google Scholar
  10. Bryan, W.B., Humphris, S.E., Thompson, G. and Casey, J.F. 1994, Comparative volcanology of small axial eruptive centers in the MARK area, J. Geophys. Res. 99: 2973–2984.Google Scholar
  11. Cann, J.R., Blackman, D.K., Smith, D.K., McAllister, E., Janssen, B., Mello, S., Avgerinos, E. Pascoe, A.R. and Escartín, J. 1997, Corrugated slip surfacs formed at ridge-transform intersections on the Mid-Atlantic Ridge, Nature 385: 329–332.Google Scholar
  12. Chen, Y. and Morgan, W.J. 1990a, Rift valley/no rift valley transition at mid-ocean ridges, J. Geophys. Res. 95: 17,571–17,581.Google Scholar
  13. Chen, Y. and Morgan, W.J. 1990b, A nonlinear rheology model for mid-ocean ridge axis topography, J. Geophys. Res. 95: 17,583–17,604.Google Scholar
  14. Crane, K. and Ballard, R.D. 1981, Volcanics and structure of the FAMOUS Narrowgate rift: evidence for cyclic evolution: AMAR 1, J. Geophys. Res. 86: 5112–5124.Google Scholar
  15. De Chabalier, J.-B. and Avouac, J.-P. 1994, Kinematics of the Asal Rift (Djibouti) determined from the deformation of Fieale volcano, Science 265: 1677–1681.Google Scholar
  16. Detrick, R.S., Needham, H.D. and Renard, V. 1995, Gravity anomalies and crustal thickness variations along the Mid-Atlantic Ridge between 33° N and 40° N, J. Geophys. Res. 100: 3767–3788.Google Scholar
  17. Escartín, J., Cowie, P.A., Searle, R.C., Allerton, S., Mitchell, N.C., MacLeod, C.J. and Slootweg, A.P. 1999, Quantifying tectonic strain and magmatic accretion at a slow spreading ridge segment, Mid-Atlantic Ridge, 29° N, J. Geophys. Res. 104: n10,421–10,437.Google Scholar
  18. Escartín, J., Hirth, G. and Evans, B. 1997, Effects of serpentinization on the lithospheric strength and the style of normal faulting at slow-spreading ridges, Earth Planet. Sci. Lett. 151: 181–189.Google Scholar
  19. Flewellen, C.G., Millard, N.W. and Rouse, I.P. 1993, TOBI, a vehicle for deep ocean survey, Elect. Comm. Eng. J. 5: 85–93.Google Scholar
  20. Gràcia, E., Parson, L.M., Bideau, D. and Hekinian, R. 1998, Volcano-tectonic variability along segments of the Mid-Atlantic Ridge between Azores platform and Hayes fracture zone: evidence from submersible and high-resolution sidescan sonar, in R.A. Mills and K. Harrison (eds), Modern Ocean Floor Processes and the Geological Record 148: Geol. Soc. Spec. Pub., London, 1–15.Google Scholar
  21. Gregg, T.K.P. and Fink, J.H. 1995, Quantification of submarine lava-flow morphology through analog experiments, Geology 24: 73–76.Google Scholar
  22. Griffiths, R.W. and Fink, J.H. 1992, Solidification and morphology of submarine lavas: A dependence on extrusion rate, J. Geophys. Res. 97: 19,729–19,737.Google Scholar
  23. Griffiths, R.W. and Fink, J.H. 1993, Effects of surface cooling on the spreading of lava flows and domes, J. Fluid Mech. 252: 667–702.Google Scholar
  24. Harper, G.D., 1985, Tectonics of slow spreading mid-ocean ridges and consequences of a variable depth to the brittle/ductile transition, Tectonics 4: 395–409.Google Scholar
  25. Head, J. W., L. Wilson, and D. K. Smith, 1996, Mid-ocean ridge eruptive vent morphology and substructure: Evidence for dike widths, eruption rates, and evolution of eruptions and axial volcanic ridges, J. Geophys. Res. 101: 28,265–28,280.Google Scholar
  26. Humler, E. and Whitechurch, H. 1988, Petrology of basalts from the Central Indian Ridge (lat. 25°23′ S, long. 70°04′ E): estimates of frequencies and fractional volumes of magma injections in a two-layered reservoir, Earth Planet. Sci. Lett. 88: 169–181.Google Scholar
  27. Kappel, E.S. and Ryan, W.B.F. 1986, Volcanic episodicity and a non-steady state rift valley along northeast Pacific spreading centers: Evidence from Sea MARC I, J. Geophys. Res. 91: 13,925–13,940.Google Scholar
  28. Kastens, K.A., Ryan, W.B.F. and Fox, P.J. 1986, Structural and volcanic expression of a fast slipping ridge-transform-ridge plate boundary: Sea MARC I and photographic surveys at the Clipperton Transform Fault, J. Geophys. Res. 91: 3469–3488.Google Scholar
  29. Khodakovskii, G., Rabinowicz, M., Genthon, P. and Ceuleneer, G. 1998, 2D modeling of melt percolation in the mantle: the role of a melt-dependent mush viscosity, Geophys. Res. Let. 25: 683–686.Google Scholar
  30. Kong, L.S., Solomon, S.C. and Purdy, G.M. 1992, Microearthquake characteristics of a mid-ocean ridge along-axis high, J. Geophys. Res. 97: 1659–1685.Google Scholar
  31. Kong, L.S.L., Detrick, R.S., Fox, P.J., Mayer, L.A. and Ryan, W.B.F. 1988, The morphology and tectonics of the Mark area from Sea Beam and Sea MARC 1 observations (Mid-Atlantic Ridge 23° N), Mar. Geophys. Res. 10: 59–90.Google Scholar
  32. Kuo, B.Y. and Forsyth, D.W. 1988, Gravity anomalies of the ridgetransform system in the South Atlantic between 31° and 34.5° S: Upwelling centers and variation in crustal thickness, Mar. Geophys. Res. 10: 205–232.Google Scholar
  33. Langmuir, C.H., Bender, J.F., Bence, A.E., Hanson, G.N. and Taylor, S.R. 1977, Petrogenesis of basalts from the FAMOUS area: Mid-Atlantic Ridge, Earth Planet. Sci. Lett. 36: 133–156.Google Scholar
  34. Lawson, K., Searle, R.C., Pearce, J.A., Browning, P. and Kempton, P. 1996, Detailed volcanic geology of the MARNOK area, Mid-Atlantic Ridge north of Kane transform, in C.J. MacLeod, P.A. Tyler, and C.L. Walker (eds), Tectonic, Magmatic, Hydrothermal and Biological Segmentation of Mid-Ocean Ridges, Geol. Soc. Spec. Publ. 118, Geol. Soc., London, 61–102.Google Scholar
  35. LeDain, A.-Y., Robineau, B. and Tapponnier, P. 1979, Les effets tectoniques de l'événement sismique et volcanique de novembre 1978 dans le rift d'Asal-Ghoubbet, Bull. Soc. géol. France XXII: 817–822.Google Scholar
  36. Lin, J., Parmentier, G.M., Schouten, H., Sempéré, J.-C. and Zervas, C. 1990, Evidence from gravity data for focused magmatic accretion along the Mid-Atlantic Ridge, Nature 344: 627–632.Google Scholar
  37. Macdonald, K.C., Fox, P.J., Perram, L.J., Eisen, M.F., Haymon, R.M., Miller, S.P., Carbotte, S.M., Cormier, M.-H. and Shor, A.N. 1988, A new view of the mid-ocean ridge from the behaviour of its discontinuities, Nature 335: 217–225.Google Scholar
  38. Manighetti, I., 1993, Dynamique des systèmes extensifs en Afar, Thèse de Doctorat de l'Univ. Paris 6, Univ. Paris 6, IPGP.Google Scholar
  39. McAllister, E. and Cann, J.R. 1996, Initiation and evolution of boundary-wall faults along the Mid-Atlantic ridge, 25–29° N, in C.J. MacLeod, P.A. Tyler and C.L. Walker (eds), Tectonic, Magmatic, Hydrothermal and Biological Segmentation of Mid-Ocean Ridges, Geol. Soc. Spec. Publ. 118, Geol. Soc., London, 29–48.Google Scholar
  40. McAllister, E., J. R. Cann, and S. Spencer, 1995, The evolution of crustal deformation in an oceanic extensional environment, J. Struct. Geol. 17: 183–199.Google Scholar
  41. Michael, P.J., Forsyth, D.W., Blackman, D.K., Fox, P.J., Hanan, B.B., Harding, A.J., Macdonald, K.C., Neumann, G.A., Orcutt, J.A., Tolstoy, M. and Weiland, C.M. 1994, Mantle control of a dynamically evolving spreading center: Mid-Atlantic Ridge 31–34° S, Earth Planet. Sci. Lett. 121: 451–468.Google Scholar
  42. Murton, B.J., Klinkhammer, G., Dover, C.V., Becker, K. Briais, A., Edge, D., Hayward, N., Millard, N., Mitchell, I., Rouse, I., Rudnicki, M., Sayanagi, K., Sloan, H. and Parson, L.M. 1994, Direct evidence for the distribution and occurrence of hydrothermal activity between 27° and 30° N on the Mid-Atlantic Ridge, Earth Planet. Sci. Lett. 125: 119–128.Google Scholar
  43. Murton, B.J. and Parson, L.M. 1993, Segmentation, volcanism and deformation of oblique spreading centres: a quantitative study of the Reykjanes ridge, Tectonophysics 222: 237–257.Google Scholar
  44. Pariso, J.E., Rommevaux, C. and Sempéré, J.-C. 1996, Three-Dimensional inversion of marine magnetic anomalies: implications for crustal accretion along the Mid-Atlantic Ridge (28°–31°30′ N), Mar. Geophys. Res. 18: 85–101.Google Scholar
  45. Pariso, J.E., Sempéré, J.-C. and Rommevaux, C. 1995, Temporal and spatial variations in crustal accretion along the Mid-Atlantic Ridge (29°–31°30′ N) over the last 10 Ma: Implications from a three-dimensional gravity study, J. Geophys. Res. 100: 17,781–17,794.Google Scholar
  46. Parson, L.M., Murton, B.J., Searle, R.C., Booth, D. Evans, J., Field, P., Keeton, J., Laughton, A., McAllister, E., Millard, N., Redbourne, L., Rouse, K. Shor, A., Smith, D., Spencer, S., Summerhayes, C. and Walker, C. 1993, En échelon axial volcanic ridges at the Reykjanes Ridge: a life cycle of volcanism and tectonics, Earth Planet. Sci. Lett. 117: 73–87.Google Scholar
  47. Patriat, P., Deplus, C., Rommevaux, C., Sloan, H., Hunter, P. and Brown, H. 1990, Evolution of the segmentation of the Mid-Atlantic Ridge between 28° and 29° N during the last 10 Ma: Preliminary results from SARA cruise (R/V Jean Charcot, May 1990) (abstract), EOS Trans. AGU 71, Fall Meeting Suppl., 1629.Google Scholar
  48. Perfit, M.R. and Chadwick, W.W.J. 1998, Magmatism at midocean ridges: Constraints from volcanological and geochemical investigations, in W.R. Buck, P.T. Delaney, J.A. Karson and Y. Lagabrielle (eds), Faulting and Magmatism at Mid-Ocean ridges, Geophys. Monograph 106, Amer. Geophys. Union, Washington, D.C.Google Scholar
  49. Purdy, G.M., Sempéré, J.-C., Schouten, H., Dubois, D.L. and Goldsmith, R. 1990, Bathymetry of the Mid-Atlantic Ridge, 24°-31° N: A map series, Mar. Geophys. Res. 12: 247–252.Google Scholar
  50. Ravilly, M., Dyment, J., Gente, P. and Thibaud, R. 1998, Axial magnetic anomaly amplitude along the Mid-Atlantic Ridge between 20° N and 40° N, J. Geophys. Res. 103: 24,201–24,221.Google Scholar
  51. Rommevaux, C., Deplus, C., Patriat, P. and Sempéré, J.-C. 1994, Three-dimensional gravity study of the Mid-Atlantic ridge: evolution of the segmentation between 28° and 29° N during the last 10 m.y., J. Geophys. Res. 99: 3015–3029.Google Scholar
  52. Rouse, I.P., 1991, TOBI: A deep towed sonar system, Civil Applications of Sonar Systems, 71–75.Google Scholar
  53. Rubin, A.M. and Pollard, D.D. 1988, Dike-induced faulting in rift zones of Iceland and Afar, Geology 16: 413–417.Google Scholar
  54. Sauter, D., Whitechurch, H., Munschy, M. and Humler, E. 1991, Periodicity in the accretion process on the Southeast Indian Ridge at 27°40′ S, Tectonophysics 195: 47–64.Google Scholar
  55. Scott, D.R. and Stevenson, D.J. 1984, Magma solitons, Geophys. Res. Let. 11: 1161–1164.Google Scholar
  56. Searle, R.C., Cowie, P.A., Mitchell, N.C., Allerton, S., MacLeod, C.J., Escartín, J., Russell, S.M., Slootweg, P.A. and Tanaka, T. 1998, Fault structure and detailed evolution of a slow spreading ridge segment: the Mid-Atlantic Ridge at 29° N, Earth Planet. Sci. Lett. 154: 167–183.Google Scholar
  57. Sempéré, J.-C., Lin, J., Brown, H.S., Schouten, H. and Purdy, G.M. 1993, Segmentation and morphotectonic variations along a slowspreading center: the Mid-Atlantic Ridge (24°00′ N-30°40′ N), Mar. Geophys. Res. 15: 153–200.Google Scholar
  58. Sempéré, J.-C., Purdy, G.M. and Schouten, H. 1990, Segmentation of the Mid-Atlantic Ridge between 24° N and 30°40′ N, Nature 344: 427–431.Google Scholar
  59. Sempéré, J.C., Blondel, P., Briais, A., Fujiwara, T., Géli, L., Isezaki, N., Pariso, J.E. Parson, L.M., Patriat, P. and Rommevaux, C. 1995, The Mid-Atlantic Ridge between 29° N and 31°31′ N in the last 10 Ma, Earth Planet. Sci. Lett. 130: 45–55.Google Scholar
  60. Shaw, P.R. and Lin, J. 1993, Causes and consequences of variations in faulting style at the mid-Atlantic ridge, J. Geophys. Res. 98: 21,839–21,852.Google Scholar
  61. Shaw, W.J. and Lin, J. 1996, Models of ocean ridge lithospheric deformation: Dependence on crustal thickness, spreading rate, and segmentation, J. Geophys. Res. 101: 17,977–17,993.Google Scholar
  62. Sloan, H., 1993, Les flancs de la dorsale Médio-Atlantique entre 28° et 29° N de 0 à 10 Ma: le rôle de la segmentation axiale dans la fabrique du relief, Thèse de Doctorat, Univ. Paris 6.Google Scholar
  63. Sloan, H. and Patriat, P. 1992, Kinematics of the North American-African plate boundary between 28° and 29° during the last 10 Ma: Evolution of the axial geometry and spreading rate, Earth Planet. Sci. Lett. 113: 323–341.Google Scholar
  64. Smith, D.K. and Cann, J.R. 1992, The role of seamount volcanism in crustal construction at the Mid-Atlantic Ridge (24°–30° N), J. Geophys. Res. 97: 1645–1658.Google Scholar
  65. Smith, D.K. and Cann, J.R. 1993, Building the crust at the Mid-Atlantic Ridge, Nature 365: 707–715.Google Scholar
  66. Smith, D.K., Cann, J.R., Dougherty, M.E., Lin, J., Spencer, S., MacLeod, C., Keeton, J., McAllister, E. Brooks, B., Pascoe, R. and Robertson, W. 1995, Mid-Atlantic Ridge volcanism from deep-towed side-scan sonar images, 25°–29° N, J. Volcanol. Geotherm. Res. 67: 233–262.Google Scholar
  67. Smith, D.K., Tivey, M.A., Schouten, H. and Cann, J.R. 1999, Locating the spreading axis along 80 km of the Mid-Atlantic Ridge south of the Atlantis Transform, J. Geophys. Res. 104: 7599–7612.Google Scholar
  68. Solomon, S.C., Huang, P.Y. and Meinke, L. 1988, The seismic moment budget of slowly spreading ridges, Nature 334: 58–61.Google Scholar
  69. Stakes, D.S., Shervais, J.W. and Hopson, C.A. 1984, The volcanictectonic cycle of the FAMOUS and AMAR valleys, Mid-Atlantic Ridge (36°47′ N): Evidence from basalt glass and phenocryst compositional variations for a steady state magma chamber beneath the valley midsections, AMAR 3, J. Geophys. Res. 89: 6995–7028.Google Scholar
  70. Stein, R.S., Briole, P., Ruegg, J.-C, Tapponnier, P. and Gasse, F. 1991, Contemporary, Holocene, and Quaternary deformation of the Asal Rift, Djibouti: Implications for the mechanics of slowspreading ridges, J. Geophys. Res. 96: 21, 789–21,806.Google Scholar
  71. Tarantola, A., Ruegg, J.C. and Lepine, J.P. 1979, Geodetic evidence for rifting in Afar: A brittle-elastic model of the behavior of the lithosphere, Earth Planet. Sci. Lett. 45: 435–444.Google Scholar
  72. Tarantola, A., Ruegg, J.C. and Lepine, J.P. 1980, Geodetic evidence for rifting in Afar, 2. Vertical displacements, Earth Planet. Sci. Lett. 48: 363–370.Google Scholar
  73. Thatcher, W. and Hill, D.P. 1995, A simple model for the faultgenerated morphology of slow-spreading mid-oceanic ridges, J. Geophys. Res. 100: 561–570.Google Scholar
  74. Thibaud, R., Dauteuil, O. and Gente, P. 1999, Faulting pattern along slow spreading ridge segments: a consequence of along-axis variation in lithospheric rheology, Tectonophysics 312: 157–174.Google Scholar
  75. Thibaud, R., Gente, P. and Maia, M. 1998, 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. 103: 24,223–24,243.Google Scholar
  76. Tolstoy, M., Harding, A.J. and Orcutt, J.A. 1993, Crustal Thickness on the Mid-Atlantic Ridge: Bull's Eyes Gravity Anomalies and Focused Accretion, Science 262: 726–729.Google Scholar
  77. Tucholke, B.E., Lin, J., Kleinrock, M.C., Tivey, M.A. Reed, T.B., Goff, J. and Jaroslow, G.E. 1997, Segmentation and crustal structure of the western Mid-Atlantic Ridge flank, 25°25′–27°10′ N and 0–29 m.y., J. Geophys. Res. 102: 10,203–10,223.Google Scholar
  78. Wolfe, C.J., Purdy, G.M., Toomey, D.R. and Solomon, S.C. 1995, Microearthquake characteristics and crustal velocity structure at 29° N on the Mid-Atlantic Ridge: The architecture of a slow spreading segment, J. Geophys. Res. 100: 24,449–24,472.Google Scholar
  79. Zervas, C.E., Sempéré, J.-C. and Lin, J. 1995, Morphology and crustal structure of a small transform fault along the Mid-Atlantic Ridge: the Atlantis fracture zone, Mar. Geophys. Res. 17: 275–300.Google Scholar

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Anne Briais
    • 1
  • Heather Sloan
    • 2
  • Lindsay M. Parson
    • 3
  • Bramley J. Murton
    • 3
  1. 1.CNRS UMR5566Observatoire Midi-PyrénéesToulouseFrance
  2. 2.American Museum of Natural HistoryNew YorkUSA
  3. 3.Southampton Oceanography CentreSouthamptonUK

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