Letter | Published:

Episodic kinematics in continental rifts modulated by changes in mantle melt fraction

Nature volume 547, pages 8488 (06 July 2017) | Download Citation

Abstract

Oceanic crust is created by the extraction of molten rock from underlying mantle at the seafloor ‘spreading centres’ found between diverging tectonic plates. Modelling studies have suggested that mantle melting can occur through decompression as the mantle flows upwards beneath spreading centres1, but direct observation of this process is difficult beneath the oceans. Continental rifts, however—which are also associated with mantle melt production—are amenable to detailed measurements of their short-term kinematics using geodetic techniques. Here we show that such data can provide evidence for an upwelling mantle flow, as well as information on the dimensions and timescale of mantle melting. For North Island, New Zealand, around ten years of campaign and continuous GPS measurements in the continental rift system known as the Taupo volcanic zone reveal that it is extending at a rate of 6–15 millimetres per year. However, a roughly 70-kilometre-long segment of the rift axis is associated with strong horizontal contraction and rapid subsidence, and is flanked by regions of extension and uplift. These features fit a simple model that involves flexure of an elastic upper crust, which is pulled downwards or pushed upwards along the rift axis by a driving force located at a depth greater than 15 kilometres. We propose that flexure is caused by melt-induced episodic changes in the vertical flow forces that are generated by upwelling mantle beneath the rift axis, triggering a transient lower-crustal flow. A drop in the melt fraction owing to melt extraction raises the mantle flow viscosity and drives subsidence, whereas melt accumulation reduces viscosity and allows uplift—processes that are also likely to occur in oceanic spreading centres.

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References

  1. 1.

    & The volume and composition of melt generated by extension of the lithosphere. J. Petrol. 29, 625–679 (1988)

  2. 2.

    . et al. Volcanic and structural evolution of Taupo Volcanic Zone, New Zealand: a review. J. Volcanol. Geotherm. Res. 68, 1–28 (1995)

  3. 3.

    et al. New Zealand GPS velocity field: 1995–2013. N. Z. J. Geol. Geophys. 59, 5–14 (2016)

  4. 4.

    Geonet (Geological Hazard Information for New Zealand). (2016)

  5. 5.

    , , & High-resolution view of active tectonic deformation along the Hikurangi subduction margin and the Taupo Volcanic Zone, New Zealand. N. Z. J. Geol. Geophys. 59, 43–57 (2016)

  6. 6.

    , & The ups and downs of the TVZ: geodetic observations of deformation around the Taupo Volcanic Zone, New Zealand. J. Geophys. Res. Solid Earth 120, 4667–4679 (2015)

  7. 7.

    , & Principal component analysis and modeling of the subsidence of the shoreline of Lake Taupo, New Zealand, 1983–1999: evidence for dewatering of a magmatic intrusion? J. Geophys. Res. Solid Earth 112, G08406 (2007)

  8. 8.

    , , & Off-axis magmatism along a subaerial back-arc rift: observations from the Taupo Volcanic Zone, New Zealand. Sci. Adv. 2, e1600288 (2016)

  9. 9.

    & The nature of the plate interface and driving force of interseismic deformation in the New Zealand plate-boundary zone, revealed by the continuous GPS velocity field. J. Geophys. Res. 118, 3160–3189 (2013)

  10. 10.

    The kinematics of the plate boundary zone through New Zealand: a comparison of short-and long-term deformations. Geophys. J. Int. 79, 613–633 (1984)

  11. 11.

    Geodetic strain and the deformational history of the North Island of New Zealand during the late Cainozoic. Phil. Trans. R. Soc. A 321, 163–181 (1987)

  12. 12.

    , , & Subduction zone coupling and tectonic block rotations in the North Island, New Zealand. J. Geophys. Res. 109, B12406 (2004)

  13. 13.

    GNS Science Active Fault Database. (2016)

  14. 14.

    Surface deformation due to shear and tensile faults in a half-space. Bull. Seismol. Soc. Am. 75, 1135–1154 (1995)

  15. 15.

    Isostasy and Flexure of the Lithosphere (Cambridge Univ. Press, 2001)

  16. 16.

    , , & 3-D seismic velocity and attenuation in the central Taupo Volcanic Zone, New Zealand: imaging the roots of geothermal systems. In Proc. World Geothermal Congr. (Melbourne, April 2015) 19–25 (International Geothermal Association, 2015)

  17. 17.

    et al. Magnetotelluric imaging of upper-crustal convection plumes beneath the Taupo Volcanic Zone, New Zealand. Geophys. Res. Lett. 39, L02304 (2012)

  18. 18.

    , , & Geophysical evidence on the structure of the Taupo Volcanic Zone and its hydrothermal circulation. J. Volcanol. Geotherm. Res. 68, 29–58 (1995)

  19. 19.

    , , & Three-dimensional electrical resistivity image of magma beneath an active continental rift, Taupo Volcanic Zone, New Zealand. Geophys. Res. Lett. 37, L10301 (2010)

  20. 20.

    et al. Imaging the deep source of the Rotorua and Waimangu geothermal fields, Taupo Volcanic Zone, New Zealand. J. Volcanol. Geotherm. Res. 314, 39–48 (2016)

  21. 21.

    Asymmetric back-arc spreading, heat flux and structure associated with the Central Volcanic Region of New Zealand. Earth Planet. Sci. Lett. 85, 265–276 (1987)

  22. 22.

    & Wide-angle seismic imaging beneath an andesitic arc: Central North Island, New Zealand. J. Geophys. Res. 116, B09308 (2011)

  23. 23.

    & Rift valley/no rift valley transition at mid-ocean ridges. J. Geophys. Res. 95, 17571–17581 (1990)

  24. 24.

    , & Mechanisms for the origin of mid-ocean ridge axial topography: implications for the thermal and mechanical structure of accreting plate boundaries. J. Geophys. Res. 92, 12823–12836 (1987)

  25. 25.

    & A self-consistent model of melting, magma migration and buoyancy-driven circulation beneath mid-ocean ridges. J. Geophys. Res. 94, 2973–2988 (1989)

  26. 26.

    & Geodynamics: Applications of Continuum Physics to Geological Problems (John Wiley, 1982)

  27. 27.

    Rheology of the Earth (Springer, 1995)

  28. 28.

    & in Inside the Subduction Factory (ed. ) 83–105 (Wiley, 2003)

  29. 29.

    Volcano spacing and rigidity. Geology 19, 397–400 (1991)

  30. 30.

    , & ITRF2008 plate motion model. J. Geophys. Res. 117, B07402 (2012)

  31. 31.

    Kinematics to dynamics in the New Zealand plate boundary zone: implications for the strength of the lithosphere. Geophys. J. Int. 201, 552–573 (2015)

  32. 32.

    , , , & Generic Mapping Tools: improved version released. Trans. AGU 94, 409–410 (2013)

  33. 33.

    , & , Basin formation behind an active subduction zone: three-dimensional flexural modelling of the Wanganui Basin, New Zealand. Basin Res. 4, 197–214 (1992)

  34. 34.

    & Simple 2-D models for melt extraction at mid-ocean ridges and island arcs. Earth Planet. Sci. Lett. 83, 137–152 (1987)

  35. 35.

    On the dynamics of mid-ocean ridges. J. Geophys. Res. 93, 429–436 (1988)

  36. 36.

    et al. A comparison of numerical surface topography calculations in geodynamic modelling: an evaluation of the ‘sticky air’ method. Geophys. J. Int. 189, 38–54 (2012)

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Acknowledgements

This paper is part of a wider project funded through the New Zealand Marsden Fund, the Earthquake Commission, and Victoria University of Wellington graduate scholarships. J.D.P.M. was supported by the National Research Foundation of Singapore (award NRF-NRFF2013-04) at the Earth Observatory of Singapore.

Author information

Affiliations

  1. Institute of Geophysics, Victoria University of Wellington, Wellington, New Zealand

    • Simon Lamb
    • , Euan Smith
    •  & Tim Stern
  2. Earth Observatory of Singapore, Nanyang Technological University, Singapore

    • James D. P. Moore

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Contributions

S.L. led the research, carried out the kinematic and flexural analysis, developed the mantle force model and wrote the manuscript. J.D.P.M. developed the viscous flow finite-element models. E.S. calculated horizontal and vertical continuous GPS velocities and their uncertainties. T.S. provided advice and help with all aspects of the study. All authors commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Simon Lamb.

Reviewer Information Nature thanks C. Beaumont, E. Calais and C. Faccenna for their contribution to the peer review of this work.

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https://doi.org/10.1038/nature22962

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