Convective upwelling in the mantle beneath the Gulf of California

Abstract

In the past six million years, Baja California has rifted obliquely apart from North America, opening up the Gulf of California1. Between transform faults, seafloor spreading and rifting is well established in several basins. Other than hotspot-dominated Iceland, the Gulf of California is the only part of the world’s seafloor-spreading system that has been surrounded by enough seismometers to provide horizontal resolution of upper-mantle structure at a scale of 100 kilometres over a distance great enough to include several spreading segments. Such resolution is needed to address the long-standing debate about the relative importance of dynamic and passive upwelling in the shallow mantle beneath spreading centres. Here we use Rayleigh-wave tomography to image the shear velocity in the upper 200 kilometres or so of the mantle. Low shear velocities similar to those beneath the East Pacific Rise oceanic spreading centre underlie the entire length of the Gulf, but there are three concentrated locations of anomalously low velocities spaced about 250 kilometres apart. These anomalies are 40 to 90 kilometres beneath the surface, at which depths petrological studies indicate that extensive melting of passively upwelling mantle should begin2,3. We interpret these seismic velocity anomalies as indicating that partial melting triggers dynamic upwelling driven by either the buoyancy of retained melt or by the reduced density of depleted mantle.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Shear velocity anomalies averaged over a depth of 50 to 90 km beneath the Gulf of California and Baja California region.
Figure 2: Average vertical shear wave velocity profiles.
Figure 3: Schematic interpretation of anomalous mantle velocities along profile AB.

References

  1. 1

    Stock, J. M. & Hodges, J. M. Pre-Pliocene extension around the Gulf of California and the transfer of Baja California to the Pacific Plate. Tectonics 8, 99–115 (1989)

    ADS  Article  Google Scholar 

  2. 2

    Langmuir, C. H., Klein, E. M. & Plank, T. in Mantle Flow and Melt Generation at Mid-Ocean Ridges (eds Morgan, P. J., Blackman, D. K., & Sinton, J. M.) 183–280 (Geophysical Monograph Series 71, American Geophysical Union, 1992)

    Google Scholar 

  3. 3

    Asimow, P. D., Hirschmann, M. M. & Stolper, E. M. Calculation of peridotite partial melting from thermodynamic models of minerals and melts. IV. Adiabatic decompression and the composition and mean properties of mid-ocean ridge basalts. J. Petrol. 42, 963–998 (2001)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Nishimura, C. & Forsyth, D. W. The anisotropic structure of the upper mantle in the Pacific. Geophys. J. 96, 203–229 (1989)

    ADS  Article  Google Scholar 

  5. 5

    Hammond, W. C. & Toomey, D. R. Seismic velocity anisotropy and heterogeneity beneath the Mantle Electromagnetic and Tomography experiment (MELT) region of the East Pacific Rise from analysis of P and S body waves. J. Geophys. Res. 108 2176 10.1029/2002JB001789 (2003)

    ADS  Article  Google Scholar 

  6. 6

    Ritzwoller, M., Shapiro, N. & Zhong, S.-J. Cooling history of the Pacific lithosphere. Earth Planet. Sci. Lett. 226, 69–84 (2004)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Buck, W. R. & Su, W. S. Focused mantle upwelling below mid-ocean ridges due to feedback between viscosity and melting. Geophys. Res. Lett. 16, 641–644 (1989)

    ADS  Article  Google Scholar 

  8. 8

    Parmentier, E. M. & Morgan, P. J. The spreading rate dependence of three-dimensional oceanic spreading center structure. Nature 348, 325–328 (1990)

    ADS  Article  Google Scholar 

  9. 9

    Magde, L. S. & Sparks, D. W. Three-dimensional mantle upwelling, melt generation, and melt migration beneath segmented slow spreading ridges. J. Geophys. Res. 106, 20571–20583 (1997)

    ADS  Article  Google Scholar 

  10. 10

    Choblet, G. & Parmentier, E. M. Mantle upwelling and melting beneath slow spreading centers: effects of variable rheology and melt productivity. Earth Planet. Sci. Lett. 184, 589–604 (2001)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Toomey, D. R. et al. Skew of mantle upwelling beneath the East Pacific Rise governs segmentation. Nature 446, 409–414 (2007)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Clayton, R. W. et al. The NARS-Baja seismic array in the Gulf of California rift zone. MARGINS Newsl. 13, 1–4 (2004)

    Google Scholar 

  13. 13

    Zhang, X. et al. Surface wave tomography of the Gulf of California. Geophys. Res. Lett. 34 L15305 10.1029/2007GL030631 (2007)

    ADS  Article  Google Scholar 

  14. 14

    Batiza, R. Geology, petrology and geochemistry of Isla Tortuga, a recently formed tholeiitic island in the Gulf of California. Geol. Soc. Am. Bull. 89, 1309–1324 (1978)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Martin, A. et al. Recent volcanism in the northern Gulf of California and the Salton trough: why a preponderance of evolved magmas? AGU Fall Meet. abstr. T11A–1841 (2008)

  16. 16

    Axen, G. Extensional segmentation of the main gulf escarpment, Mexico and United States. Geology 23, 515–518 (1995)

    ADS  Article  Google Scholar 

  17. 17

    Harmon, N., Forsyth, D. W. & Weeraratne, D. S. Thickening of young Pacific lithosphere from high resolution Rayleigh wave tomography: a test of the conductive cooling model. Earth Planet. Sci. Lett. 278 96–106 10.1016/j.epsl.2008.11.025 (2008)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Yang, Y. & Forsyth, D. W. Rayleigh wave phase velocities, small-scale convection, and azimuthal anisotropy beneath southern California. J. Geophys. Res. 111 B07306 10.1029/2005JB004180 (2006)

    ADS  Article  Google Scholar 

  19. 19

    Faul, U. H., FitzGerald, J. D. & Jackson, I. Shear-wave attenuation and dispersion in melt-bearing olivine polycrystals. II. Microstructural interpretation and seismological implications. J. Geophys. Res. 109 10.1029/2003B002407 (2004)

  20. 20

    Hammond, W. C. & Humphreys, E. D. Upper mantle seismic wave velocity: effects of realistic partial melt geometries. J. Geophys. Res. 105, 10975–10986 (2000)

    ADS  Article  Google Scholar 

  21. 21

    Karato, S. & Jung, H. Water, partial melting and the origin of the seismic low velocity and high attenuation zone in the upper mantle. Earth Planet. Sci. Lett. 157, 193–207 (1998)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Stixrude, L. & Lithgow-Bertelloni, C. Mineralogy and elasticity of the oceanic upper mantle: origin of the low-velocity zone. J. Geophys. Res. 110 B03204 10.1029/2004JB002965 (2005)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Yang, Y., Forsyth, D. W. & Weeraratne, D. S. Seismic attenuation near the East Pacific Rise and the origin of the low-velocity zone. Earth Planet. Sci. Lett. 258, 260–268 (2007)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Hammond, W. C. & Humphreys, E. D. Upper mantle seismic wave attenuation: effects of realistic partial melt distribution. J. Geophys. Res. 105, 10987–10999 (2000)

    ADS  Article  Google Scholar 

  25. 25

    Forsyth, D. W. & Li, A. in Seismic Earth: Array Analysis of Broadband Seismograms (eds Levander, A. & Nolet, G.) 81–97 (Geophysical Monograph Series 157, American Geophysical Union, 2005)

    Google Scholar 

  26. 26

    Yang, Y. & Forsyth, D. W. Regional tomographic inversion of the amplitude and phase of Rayleigh waves with 2-D sensitivity kernels. Geophys. J. Int. 166 1148–1160 10.1111/j.1365–246X.2006.02972.x (2006)

    ADS  Article  Google Scholar 

  27. 27

    Zhou, Y., Dahlen, F. A. & Nolet, G. 3-D sensitivity kernels for surface-wave observables. Geophys. J. Int. 158, 142–168 (2004)

    ADS  Article  Google Scholar 

  28. 28

    Zhang, X. et al. 3D shear velocity structure beneath the Gulf of California from Rayleigh wave dispersion. Earth Planet. Sci. Lett. 279, 255–262 (2009)

    ADS  CAS  Article  Google Scholar 

Download references

Acknowledgements

This research was supported by the MARGINS programme of the National Science Foundation.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Yun Wang.

Supplementary information

Supplementary Figures

This file contains Supplementary Figures S1 - S8 with Legends. (PDF 1693 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Wang, Y., Forsyth, D. & Savage, B. Convective upwelling in the mantle beneath the Gulf of California. Nature 462, 499–501 (2009). https://doi.org/10.1038/nature08552

Download citation

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing