Most models of melt generation beneath mid-ocean ridges1,2,3 predict significant reduction of melt production at ultraslow spreading rates (full spreading rates <20 mm yr-1) and consequently they predict thinned oceanic crust. The 1,800-km-long Arctic Gakkel mid-ocean ridge is an ideal location to test such models, as it is by far the slowest portion of the global mid-ocean-ridge spreading system, with a full spreading rate ranging from 6 to 13 mm yr-1 (refs 4, 5). Furthermore, in contrast to some other ridge systems, the spreading direction on the Gakkel ridge is not oblique and the rift valley is not offset by major transform faults. Here we present seismic evidence for the presence of exceptionally thin crust along the Gakkel ridge rift valley with crustal thicknesses varying between 1.9 and 3.3 km (compared to the more usual value of 7 km found on medium- to fast-spreading mid-ocean ridges). Almost 8,300 km of closely spaced aeromagnetic profiles across the rift valley show the presence of discrete volcanic centres along the ridge, which we interpret as evidence for strongly focused, three-dimensional magma supply. The traces of these eruptive centres can be followed to crustal ages of ∼25 Myr off-axis, implying that these magma production and transport systems have been stable over this timescale.
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Reid, I. & Jackson, H. R. Oceanic spreading rate and crustal thickness. Mar. Geophys. Res. 5, 165–172 (1981)
Bown, J. W. & White, R. S. Variation with spreading rate of oceanic crustal thickness and geochemistry. Earth Planet. Sci. Lett. 121, 435–449 (1994)
Su, W., Mutter, C. Z., Mutter, J. C. & Buck, W. R. Some theoretical predictions on the relationships among spreading rate, mantle temperature, and crustal thickness. J. Geophys. Res. B 99, 3215–3227 (1994)
Karasik, A. M. The Eurasia Basin of the Arctic Ocean from the point of view of plate tectonics. Nauchno-Issled. Inst. Geol. Avktiki, 23–31 (1974)
Vogt, P. R., Taylor, P. T., Kovacs, L. C. & Johnson, G. L. Detailed aeromagnetic investigation of the Arctic Basin. J. Geophys. Res. B 84, 1071–1089 (1979)
Duckworth, G. L. & Baggeroer, A. B. Inversion of refraction data from the Fram and Nansen basins of the Arctic Ocean. Tectonophysics 114, 55–102 (1985)
Jackson, H. R., Reid, I. & Falconer, R. K. H. Crustal structure near the Arctic Mid-Ocean Ridge. J. Geophys. Res. B 87, 1773–1783 (1982)
Kristoffersen, Y., Husebye, E. S., Bungum, H. & Gregersen, S. Seismic investigations of the Nansen Ridge during the FRAM I experiment. Tectonophysics 82, 57–68 (1982)
Jackson, H. R., Forsyth, D. A., Hall, J. K. & Overton, A. in The Arctic Ocean Region (eds Grantz, A., Johnson, L. & Sweeney, J. F.) 153–170 (The Geology of North America Vol. L, Geological Society of America, Boulder, 1990)
Coakley, B. J. & Cochran, J. R. Gravity evidence of very thin crust at the Gakkel Ridge (Arctic Ocean). Earth Planet. Sci. Lett. 162, 81–95 (1998)
Weigelt, E. & Jokat, W. Peculiarities of roughness and thickness of oceanic crust in the Eurasian Basin, Arctic Ocean. Geophys. J. Int. 145, 505–516 (2001)
Michael, P. J. et al. Magmatic and amagmatic sea-floor generation at the slowest-spreading Arctic Gakkel ridge. Nature 423, 956–961 (2003)
Jokat, W., et al. in Polarstern ARKTIS XVII/2 Cruise Report: AMORE 2001 (ed. Thiede, J.) 165–206 (Reports on Polar and Marine Research 421, Alfred Wegener Institute, Bremerhaven, 2002)
Zelt, C. A. & Smith, R. B. Seismic traveltime inversion for 2-D crustal velocity structure. Geophys. J. Int. 108, 16–34 (1992)
Klingelhöfer, F., Géli, L., Matias, L., Steinsland, N. & Mohr, J. Crustal structure of a super-slow spreading centre: a seismic refraction study of Mohns Ridge, 72°N. Geophys. J. Int. 141, 509–526 (2000)
Muller, M. R., Minshull, T. A. & White, R. S. Segmentation and melt supply at the Southwest Indian Ridge. Geology 27, 867–870 (1999)
Jakobsson, M., Cherkis, N. Z., Woodward, J., Macnab, R., & Coakley, B. New grid of Arctic bathymetry aids scientists and mapmakers. Eos 81, 89, 93, 96 (2000).
DeMets, C., Gordon, R. G., Argus, D. F. & Stein, S. Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions. Geophys. Res. Lett. 21, 2191–2194 (1994)
White, R. S., Minshull, T. A., Bickle, M. J. & Robinson, C. J. Melt generation at very slow-spreading oceanic ridges: Constraints from geochemical and geophysical data. J. Petrol. 42, 1171–1196 (2001)
We thank the officers and crews of PFS Polarstern and USCGC Healy for their technical and logistical support, and the helicopter teams and all the members of the AMORE scientific party for their efforts. This work was supported by the Deutsche Forschungsgemeinschaft and the U.S. National Science Foundation.
The authors declare that they have no competing financial interests.
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Jokat, W., Ritzmann, O., Schmidt-Aursch, M. et al. Geophysical evidence for reduced melt production on the Arctic ultraslow Gakkel mid-ocean ridge. Nature 423, 962–965 (2003). https://doi.org/10.1038/nature01706
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