Mid-ocean ridges spreading at ultraslow rates of less than 20 mm yr−1 can exhume serpentinized mantle to the seafloor, or they can produce magmatic crust. However, seismic imaging of ultraslow-spreading centres has not been able to resolve the abundance of serpentinized mantle exhumation, and instead supports 2 to 5 km of crust. Most seismic crustal thickness estimates reflect the depth at which the 7.1 km s−1 P-wave velocity is exceeded. Yet, the true nature of the oceanic lithosphere is more reliably deduced using the P- to S-wave velocity (Vp/Vs) ratio. Here we report on seismic data acquired along off-axis profiles of older oceanic lithosphere at the ultraslow-spreading Mid-Cayman Spreading Centre. We suggest that high Vp/Vs ratios greater than 1.9 and continuously increasing P-wave velocity, changing from 4 km s−1 at the seafloor to greater than 7.4 km s−1 at 2 to 4 km depth, indicate highly serpentinized peridotite exhumed to the seafloor. Elsewhere, either magmatic crust or serpentinized mantle deformed and uplifted at oceanic core complexes underlies areas of high bathymetry. The Cayman Trough therefore provides a window into mid-ocean ridge dynamics that switch between magma-rich and magma-poor oceanic crustal accretion, including exhumation of serpentinized mantle covering about 25% of the seafloor in this region.
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Searle, R. Mid-Ocean Ridges (Cambridge Univ. Press, Cambridge, 2013).
White, R. S., Minshull, T. A., Bickle, M. & Robinson, C. J. Melt generation at very slow-spreading oceanic ridges: constraints from geochemical and geophysical data. J. Petrol. 42, 1171–1196 (2001).
Jokat, W. & Schmidt-Aursch, M. C. Geophysical characteristics of the ultraslow spreading Gakkel Ridge, Arctic Ocean. Geophys. J. Int. 168, 983–998 (2007).
Minshull, T. A., Muller, M. R. & White, R. S. Crustal structure of the Southwest Indian Ridge at 66°E: seismic constraints. Geophys. J. Int. 166, 135–147 (2006).
van Avendonk, H. J. A., Davis, J. K., Harding, J. L. & Lawver, L. A. Decrease in oceanic crustal thickness since the breakup of Pangaea. Nat. Geosci. 10, 58–62 (2017).
Dick, H. J. B., Lin, J. & Schouten, H. An ultraslow-spreading class of ocean ridge. Nature 426, 405–412 (2003).
Michael, P. J. et al. Magmatic and amagmatic seafloor generation at the ultraslow spreading Gakkel Ridge, Arctic Ocean. Nature 423, 956–961 (2003).
Sauter, D. et al. Continuous exhumation of mantle-derived rocks at the Southwest Indian Ridge for 11 million years. Nat. Geosci. 6, 314–320 (2013).
Smith, D. K., Cann, J. R. & Escartin, J. Widespread active detachment faulting and core complex formation near 13°N on the Mid-Atlantic Ridge. Nature 442, 440–443 (2006).
Canales, J. P., Tucholke, B. E., Xu, M., Collins, J. A. & DuBois, D. L. Seismic evidence for large-scale compositional heterogeneity of oceanic core complexes. Geochem. Geophys. Geosyst. 9, Q08002 (2008).
Blackman, D. K. et al. Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid‐Atlantic Ridge 30°N. J. Geophys. Res. 116, B07103 (2011).
Dick, H. J. B. et al. A long in-situ section of the lower ocean crust: results of ODP leg 176 drilling at the Southwest Indian Ridge. Earth Planet. Sci. 179, 31–51 (2000).
White, R. S., McKenzie, D. & O’Nions, R. K. Oceanic crustal thickness from seismic measurements and rare earth element inversions. J. Geophys. Res. 97, 19683–19715 (1992).
Grevemeyer, I., Ranero, C. R. & Ivandic, M. Structure of oceanic crust and serpentinization at subduction trenches. Geosphere 14, 395–418 (2018).
Carlson, R. L. & Jay Miller, D. Influence of pressure and mineralogy on seismic velocities in oceanic gabbros: implications for the composition and state of the lower oceanic crust. J. Geophys. Res. 109, B09205 (2004).
Prada, M. et al. Mantle exhumation and sequence of magmatic events in the Magnaghi-Vavilov Basin (Central Tyrrhenian, Italy): new constraints from geological and geophysical observations. Tectonophysics 689, 133–142 (2016).
Dean, S. M., Minshull, T. A., Whitmarsh, R. B. & Louden, K. E. Deep structure of the ocean-continent transition in the southern Iberia abyssal plain from seismic refraction profiles: the IAM-9 transect at 40°20′N. J. Geophys. Res. 105, 5859–5885 (2000).
Bullock, A. D. & Minshull, T. A. From continental extension to seafloor spreading: crustal structure of the Goban Spur rifted margin, southwest of the UK. Geophys. J. Int. 163, 527–546 (2005).
Christensen, N. I. Serpentinites, peridotites, and seismology. Int. Geol. Rev. 46, 795–816 (2004).
Carlson, R. L. & Miller, D. J. A new assessment of the abundance of serpentinite in the oceanic crust. Geophys. Res. Lett. 24, 457–460 (1997).
Hayman, N. W. et al. Oceanic core complex development at the ultraslow spreading Mid‐Cayman Spreading Centre. Geochem. Geophys. Geosyst. 12, Q0AG02 (2011).
Rosencrantz, E., Malcom, R. I. & Sclater, J. G. Age and spreading history of the Cayman trough as determined from depth, heat flow, and magnetic anomalies. J. Geophys. Res. 93, 2141–2157 (1988).
Klein, E. M. & Langmuir, C. H. Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness. J. Geophys. Res. 92, 8089–8115 (1987).
Connelly, D. P. et al. Hydrothermal vent fields and chemosynthetic biota on the world’s deepest seafloor spreading centre. Nat. Commun. 3, 620 (2012).
Harding, J. L. et al. Magmatic-tectonic conditions for hydrothermal venting on an ultraslow-spread oceanic core complex. Geology 45, 839–842 2017).
Van Avendonk, H. J. A. et al. Seismic structure and segmentation of the axial valley of the Mid-Cayman spreading centre. Geochem. Geophys. Geosyst. 18, 2149–2161 (2017).
ten Brink, U., Coleman, D. & Dillon, W. P. The nature of the crust under Cayman Trough from gravity. Mar. Pet. Geol. 19, 971–987 (2002).
Cannat, M. et al. Thin crust, ultramafic exposures, and rugged faulting patterns at the Mid‐Atlantic Ridge (22°–24°N). Geology 23, 49–52 (1995).
Lizarralde, D., Gaherty, J. B., Collins, J. A., Hirth, G. & Kim, S. D. Spreading-rate dependence of melt extraction at mid-ocean ridges from mantle refraction data. Nature 432, 744–747 (2004).
Dannowski, A. et al. Crustal structure of the propagating TAMMAR ridge segment on the Mid‐Atlantic Ridge, 21.5°N. Geochem. Geophys. Geosyst. 12, Q07012 (2011).
Früh-Green, G. L., Connolly, J. A. D., Plas, A., Kelley, D. S. & Grobety, B. Serpentinization of oceanic peridotites: implications for geochemical cycles and biological activity. Geophys. Monogr. 114, 119–136 (2004).
Cannat, M., Fontaine, F. J. and Escartín, J. in Diversity of Hydrothermal Systems on Slow Spreading Ocean Ridges (eds Rona, P. A. et al.) 241–263 (AGU, Washington, DC, 2010).
Olive, J.-A., Behn, M. D. & Tucholke, B. E. The structure of oceanic core complexes controlled by the depth distribution of magma emplacement. Nat. Geosci. 3, 491–495 (2010).
Müller, R. D., Sdrolias, M., Gaina, C. & Roest, W. R. Age, spreading rates, and spreading asymmetry of the world’s ocean crust. Geochem. Geophys. Geosyst. 9, Q04006 (2008).
Minshull, T. A., Sinha, M. C. & Peirce, C. Multi-disciplinary, sub-seabed geophysical imaging: a new pool of 28 seafloor instruments in use by the United Kingdom Ocean Bottom Instrument Consortium. Sea Technol. 46, 27–31 (2005).
Korenaga, J. et al. Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography. J. Geophys. Res. 105, 21591–21614 (2000).
Kahle, R. L., Tilmann, F. & Grevemeyer, I. Crustal structure and kinematics of the TAMMAR propagating rift system on the Mid-Atlantic Ridge from seismic refraction and satellite altimetry gravity. Geophys. J. Int. 206, 1382–1397 (2016).
Tarantola, A. Inverse Problem Theory: Methods for Data Fitting and Model Parameter Estimation. (Elsevier Science: New York, NY, 1987).
Toomey, D. R. & Foulger, G. R. Tomographic inversion of local earthquake data from Hengill-Grensdalur central volcano complex, Iceland. J. Geophys. Res. 94, 17497–17510 (1989).
Johnston, J. E. & Christensen, N. I. Seismic properties of layer 2 basalts. Geophys. J. Int. 128, 285–300 (1997).
Christensen, N. I., Wepfer, W. W. & Baus, R. D. Seismic properties of sheeted dikes from hole 504B, ODP leg 111. Proc. Ocean Drill. Prog. Sci. Res. 111, 171–176 (1989).
Salisbury, M. H. et al. Old oceanic crust: synthesis of logging, laboratory, and seismic data from leg 102. Proc. Ocean Drill. Prog. Sci. Res. 102, 155–180 (1988).
Wilkens, R. H., Christensen, N. I. and Slater, L. in High-Pressure Seismic Studies of Leg 69 and 70 Basalts (eds Cann, J. R. et al.) Initial Reports DSDP 69, 683–686 (US Government Printing Office, Washington, DC, 1983).
Iturrino, G. J., Christensen, N. I., Kirby, S. & Salisbury, M. H. Seismic velocities and elastic properties of oceanic gabbroic rocks from hole 735B. Proc. Ocean Drill. Prog. Sci. Res. 118, 227–244 (1991).
Iturrino, G. J., Miller, D. J. & Christensen, N. I. Velocity behavior of lower crustal and upper mantle rocks from a fast-spreading ridge at Hess Deep. Proc. Ocean Drill. Prog. Sci. Res. 147, 417–440 (1996).
Miller, D. J. & Christensen, N. I. Seismic velocities of lower crustal and upper mantle rocks from the slow spreading Mid-Atlantic Ridge, south of the Kane Tranform Zone (MARK). Proc. Ocean Drill. Prog. Sci. Res. 153, 437–454 (1997).
Christensen, N. I. Elasticity of ultrabasic rocks. J. Geophys. Res. 71.24, 5921–5931 (1966).
Christensen, N. I. The abundance of serpentinites in the oceanic crust. J. Geol. 80, 709–719 (1972).
Christensen, N. I. Ophiolites, seismic velocities and oceanic crustal structure. Tectonophysics 47, 131–157 (1978).
Sandwell, D. T., Müller, R. D., Smith, W. H. F., Garcia, E. & Francis, R. New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure. Science 346, 65–67 (2014).
Talwani, M., Worzel, J. L. & Landisman, M. Rapid gravity computation for two-dimensional bodies with application to the Mendocino Submarine Fracture Zone. J. Geophys. Res. 64, 49–59 (1959).
Funding for this project was obtained from the German Science Foundation (DFG), supporting RV METEOR cruise M115, from the US National Science Foundation (NSF) under grant OCE-1356895, and from the British Natural Environment Research Council (NERC) under grant NE/K011162/1. The authors thank the captain, officers, crew and scientific party of RV METEOR for their assistance during the CAYSEIS cruise.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Grevemeyer, I., Hayman, N.W., Peirce, C. et al. Episodic magmatism and serpentinized mantle exhumation at an ultraslow-spreading centre. Nature Geosci 11, 444–448 (2018). https://doi.org/10.1038/s41561-018-0124-6
Investigating the Goban Spur rifted continental margin, offshore Ireland, through integration of new seismic reflection and potential field data
Constraints on crustal structure of adjacent OCCs and segment boundaries at 13°N on the Mid-Atlantic Ridge
Geophysical Journal International (2019)
Volcanic‐Tectonic Structure of the Mount Dent Oceanic Core Complex in the Ultraslow Mid‐Cayman Spreading Center Determined From Detailed Seafloor Investigation
Geochemistry, Geophysics, Geosystems (2019)
Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre
Geophysical Journal International (2019)
Constraining the maximum depth of brittle deformation at slow- and ultraslow-spreading ridges using microseismicity