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Off-rift volcanism in rift zones determined by crustal unloading


When continents are stretched over a long period of time, deep elongated rift valleys form at Earth’s surface and zones of ponded magma, centred beneath the rift, form at the crust–mantle boundary1,2. Ascending magma sometimes erupts within the rift valley3,4 or, counterintuitively, at volcanic fields away from the rift valley that are offset by tens of kilometres from the source of magma at depth5,6,7,8. The controls on the distribution of this off-rift volcanism are unclear. Here we use a numerical model of magmatic dyke propagation during rifting to investigate why some dykes reach the surface outside the rift valley, whereas others are confined to the valley. We find that the location of magmatism is governed by the competition between tectonic stretching and gravitational unloading pressure, caused by crustal thinning and faulting along the rift borders. When gravitational unloading dominates over tectonic stretching forces, dykes ascending from the ponded magma are steered towards the rift sides, eventually causing off-rift eruptions. Our model also predicts the formation of stacked magma sills in the lower crust above the magma-ponding zone, as well as the along-rift propagation of shallow dykes during rifting events, consistent with observations of magmatism and volcanism in rift zones globally. We conclude that rift topography-induced stress changes provide a fundamental control on the transfer of magma from depth to the surface.

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Figure 1: Examples of off-rift volcanism.
Figure 2: Set-up for the numerical experiments.
Figure 3: Numerical simulations.
Figure 4: Summary of the numerical results.

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  1. Lubimova, E. A. Heat flow patterns from Baikal and other rift zones. Tectonophysics 8, 457–467 (1969).

    Article  Google Scholar 

  2. Bown, J. W. & White, R. S. Effect of finite extension rate on melt generation at rifted continental margins. J. Geophys. Res. 100, 18011–18029 (1995).

    Article  Google Scholar 

  3. Ebinger, C. J. & Casey, M. Continental breakup in magmatic provinces: An Ethiopian example. Geology 29, 527–530 (2001).

    Article  Google Scholar 

  4. Wright, T. J. et al. Magma maintained rift segmentation at continental rupture in the 2005 Afar dyking episode. Nature 442, 291–294 (2006).

    Article  Google Scholar 

  5. Ellis, M. & King, G. Structural control of flank volcanism in continental rifts. Science 254, 839–842 (1991).

    Article  Google Scholar 

  6. Morton, W. H., Mitchell, J. G., Rex, D. C. & Mohr, P. Riftward younging of volcanic units in the Addis-Ababa region, Ethiopian rift valley. Nature 280, 284–288 (1979).

    Article  Google Scholar 

  7. Kiselev, A. I. Volcanism of the Baikal rift zone. Tectonophysics 143, 235–244 (1987).

    Article  Google Scholar 

  8. Richet, P. Guide des Volcans de France (BRGM Belin, (2003).

    Google Scholar 

  9. Abebe, T., Mazzarini, F., Innocenti, F. & Manetti, P. The Yerer–Tullu Wellel volcanotectonic lineament: A transitional structure in central Ethiopia and the associated magmatic activity. J. Afr. Earth Sci. 26, 135–150 (1998).

    Article  Google Scholar 

  10. Chernet, T., Hart, W. K., Aronson, J. L. & Walter, R. C. New age constraints on the timing of volcanism and tectonism in the northern Main Ethiopian Rift – southern Afar transition zone (Ethiopia). J. Volcanol. Geotherm. Res. 80, 267–280 (1998).

    Article  Google Scholar 

  11. Bosworth, W., Huchon, P. & McClay, K. The Red Sea and Gulf of Aden basins. J. Afr. Earth Sci. 43, 334–378 (2005).

    Article  Google Scholar 

  12. McKenzie, D. Some remarks on the development of sedimentary basins. Earth Planet. Sci. Lett. 40, 25–32 (1978).

    Article  Google Scholar 

  13. Bosworth, W. Off-axis volcanism in the Gregory Rift, east Africa: Implications for models of continental rifting. Geology 15, 397–400 (1987).

    Article  Google Scholar 

  14. Davis, R. & Selvadurai, A. Elasticity and Geomechanics (Cambridge Univ. Press, (1996).

    Google Scholar 

  15. Maccaferri, F., Bonafede, M. & Rivalta, E. A quantitative study of the mechanisms governing dike propagation, dike arrest and sill formation. J. Volcanol. Geotherm. Res. 208, 39–50 (2011).

    Article  Google Scholar 

  16. Hooper, A. et al. Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geosci. 4, 783–786 (2011).

    Article  Google Scholar 

  17. Deverchere, J. et al. Depth distribution of earthquakes in the Baikal Rift system and its implications for the rheology of the lithosphere. Geophys. J. Int. 146, 714–730 (2001).

    Article  Google Scholar 

  18. Foster, A. N. & Jackson, C. A. Source parameters of large African earthquakes: Implications for crustal rheology and regional kinematics. Geophys. J. Int. 134, 422–448 (1998).

    Article  Google Scholar 

  19. Craig, T. J., Jackson, C. A., Preistley, K. & McKenzie, D. Earthquake distribution patterns in Africa: Their relationship to variations in lithospheric and geological structure, and their rheological implications. Geophys. J. Int. 185, 403–434 (2011).

    Article  Google Scholar 

  20. Thybo, H. & Nielsen, C. A. Magma-compensated crustal thinning in continental rift zones. Nature 457, 873–876 (2009).

    Article  Google Scholar 

  21. Mackenzie, G. D., Thybo, H. & Maguire, P. K. H. Crustal velocity structure across the Main Ethiopian Rift: Results from 2-dimensional wide-angle seismic modeling. Geophys. J. Int. 162, 994–1006 (2005).

    Article  Google Scholar 

  22. Peccerillo, A. et al. Petrogenesis of silicic peralkaline rocks in the Ethiopian Rift: Geochemical evidence and volcanological implications. J. Afr. Earth Sci. 48, 161–173 (2007).

    Article  Google Scholar 

  23. Rooney, T. O., Furman, T., Bastow, I., Ayalew, D. & Yirgu, G. Lithospheric modification during crustal extension in the Main Ethiopian Rift. J. Geophys. Res. 112, B10201 (2007).

    Article  Google Scholar 

  24. Rooney, T. O., Bastow, I. D. & Keir, D. Insights into extensional processes during magma assisted rifting: Evidence from alligned scoria cones. J. Volcanol. Geotherm. Res. 201, 83–96 (2011).

    Article  Google Scholar 

  25. Pagli, C. et al. Shallow axial magma chamber at the slow-spreading Erta Ale Ridge. Nature Geosci. 5, 284–288 (2012).

    Article  Google Scholar 

  26. Nobile, A. et al. Dike-fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia). Geophys. Res. Lett. 39, L19305 (2012).

    Article  Google Scholar 

  27. Grandin, R. et al. Seismicity during lateral dike propagation: Insights from new data in the recent Manda Hararo-Dabbahu rifting episode (Afar, Ethiopia). Geochem. Geophys. Geosyst. 12, Q0AB08 (2011).

    Article  Google Scholar 

  28. Pallister, J. S. et al. Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia. Nature Geosci. 3, 703–710 (2010).

    Article  Google Scholar 

  29. Wolfenden, E., Ebinger, C. J., Yirgu, G., Renne, P. & Kelley, S. P. Evolution of a volcanic rifted margin: Southern Red Sea, Ethiopia. Geol. Soc. Am. Bull. 117, 846–864 (2005).

    Article  Google Scholar 

  30. Dahm, T. Numerical simulations of the propagation path and the arrest of fluid-filled fractures in the Earth. Geophys. J. Int. 141, 623–638 (2000).

    Article  Google Scholar 

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C. Pagli is acknowledged for extracting the SRTM DEM for the CdPs. The work was financially supported by the ERC StG project N. 240583 CCMP-POMPEI. V.A. acknowledges the PRIN 2009 project.

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F.M. and E.R. planned the paper, the numerical experiments and formulated the analytical modelling. F.M. implemented and ran the BE code. D.K. and V.A. compared the numerical results with natural cases. D.K. made Fig. 1 with input from V.A. F.M. made Figs 24 with input from E.R. All authors discussed the results and contributed to writing the manuscript.

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Correspondence to Francesco Maccaferri.

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The authors declare no competing financial interests.

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Maccaferri, F., Rivalta, E., Keir, D. et al. Off-rift volcanism in rift zones determined by crustal unloading. Nature Geosci 7, 297–300 (2014).

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