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Pre-collisional extension of microcontinental terranes by a subduction pulley


Terrane accretion is a ubiquitous process of plate tectonics that delivers fragments of subduction-resistant lithosphere into a subduction zone, resulting in events such as ocean plateau docking or continental assembly and orogenesis. The post-collisional extension of continental terranes is a well-documented tectonic process linked with gravitational collapse and/or trench retreat. Here we propose that microcontinental terranes can also undergo a substantial extension before their collision with the upper plate, owing to pull from the trenchward part of the subducting plate. Forward geodynamic numerical experiments demonstrate that this pre-collisional extension can occur over a protracted phase on microcontinents that are drifting towards a subduction zone, which distinguishes the deformation from post-collisional extension on the overriding plate, as is traditionally postulated. The results show that the magnitude of pre-collisional extension is inversely correlated with the size of the microcontinental terrane and imposed convergence velocity. We find that locations along the Tethyan belts, namely, the Sesia zone and Eastern Anatolia, are evidence for this style of pre-collisional extension, as this mechanism reconciles with geothermobarometric data and kinematic analyses. The operation of this subduction pulley reveals that drifting lithospheric plates may undergo substantial tectonic events before the arrival and involvement with regular plate boundary processes.

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Fig. 1: Map showing main orogenic belts in the Alpine–Mediterranean region.
Fig. 2: Model results showing the effect of microcontinent width with 0 cm yr–1 imposed convergence rate.
Fig. 3: Plots showing the magnitudes of pre-collisional extension depending on tested parameters.
Fig. 4: The mechanical analogue demonstrates the fundamental dynamics of the tectonic system.
Fig. 5: The geological evidence for pre-collisional continental terrane extension.

Data availability

The data—the outputs of the numerical experiments—that support the findings of this study are available at

Code availability

The SOPALE modelling code was developed by the Dalhousie University Geodynamics group; this is not a freely available open-source code. Documentation for the code and the address of the developer research group may be found at


  1. 1.

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

    Google Scholar 

  2. 2.

    Şengör, A. M. C. & Burke, K. Relative timing of rifting and volcanism on Earth and its tectonic implications. Geophys. Res. Lett. 5, 419–421 (1978).

    Google Scholar 

  3. 3.

    Turcotte, D. L. & Emerman, S. H. Mechanisms of active and passive rifting. Dev. Geotecton. 19, 39–50 (1983).

    Google Scholar 

  4. 4.

    Royden, L. H. Evolution of retreating subduction boundaries formed during continental collision. Tectonics 12, 629–638 (1993).

    Google Scholar 

  5. 5.

    Jolivet, L. & Faccenna, C. Mediterranean extension and the Africa–Eurasia collision. Tectonics 19, 1095–1106 (2000).

    Google Scholar 

  6. 6.

    Brun, J.-P. & Faccenna, C. Exhumation of high-pressure rocks driven by slab rollback. Earth Planet. Sci. Lett. 272, 1–7 (2008).

    Google Scholar 

  7. 7.

    Compagnoni, R. et al. The Sesia–Lanzo zone, a slice of continental crust with Alpine high pressure-low temperature assemblages in the Western Italian Alps. Rend. Soc. Ital. Mineral. Petrol. 33, 281–334 (1977).

    Google Scholar 

  8. 8.

    Avigad, D. Pre-collisional ductile extension in the internal western Alps (Sesia zone, Italy). Earth Planet. Sci. Lett. 137, 175–188 (1996).

    Google Scholar 

  9. 9.

    Dewey, J. F. Extensional collapse of orogens. Tectonics 7, 1123–1139 (1988).

    Google Scholar 

  10. 10.

    Rey, P., Vanderhaeghe, O. & Teyssier, C. Gravitational collapse of the continental crust: definition, regimes and modes. Tectonophysics 342, 435–449 (2001).

    Google Scholar 

  11. 11.

    Price, R. A. The Cordilleran foreland thrust and fold belt in the southern Canadian Rocky Mountains. Geol. Soc. Lond. Spec. Publ. 9, 427–448 (1981).

    Google Scholar 

  12. 12.

    Nur, A. & Ben-Avraham, Z. Oceanic plateaus, the fragmentation of continents, and mountain building. J. Geophys. Res. 8, 3644–3661 (1982).

    Google Scholar 

  13. 13.

    Coney, P. J., Jones, D. L. & Monger, J. W. H. Cordilleran suspect terranes. Nature 288, 329–333 (1980).

    Google Scholar 

  14. 14.

    Sigloch, K., McQuarrie, N. & Nolet, G. Two-stage subduction history under North America inferred from multiple-frequency tomography. Nat. Geosci. 1, 458–462 (2008).

    Google Scholar 

  15. 15.

    Fullsack, P. An arbitrary Lagrangian–Eulerian formulation for creeping flows and its application in tectonic models. Geophys. J. Int. 120, 1–23 (1995).

    Google Scholar 

  16. 16.

    Pysklywec, R. N., Beaumont, C. & Fullsack, P. Lithospheric deformation during the early stages of continental collision: numerical experiments and comparison with South Island, New Zealand. J. Geophys. Res. Solid Earth 107, (2002).

  17. 17.

    Gray, R. & Pysklywec, R. N. Geodynamic models of mature continental collision: evolution of an orogen from lithospheric subduction to continental retreat/delamination. J. Geophys. Res. Solid Earth 117, B03408 (2012).

    Google Scholar 

  18. 18.

    Göğüş, O. H., Pysklywec, R. N., Şengör, A. M. C. C. & Gün, E. Drip tectonics and the enigmatic uplift of the Central Anatolian Plateau. Nat. Commun. 8, 1538 (2017).

    Google Scholar 

  19. 19.

    Bodur, Ö. F., Göğüş, O. H., Pysklywec, R. N. & Okay, A. I. Mantle lithosphere rheology, vertical tectonics, and the exhumation of (U)HP rocks. J. Geophys. Res. Solid Earth 123, 1824–1839 (2018).

    Google Scholar 

  20. 20.

    Heron, P. J., Pysklywec, R. N. & Stephenson, R. Lasting mantle scars lead to perennial plate tectonics. Nat. Commun. 7, 11834 (2016).

    Google Scholar 

  21. 21.

    Vink, G. E., Morgan, W. J. & Zhao, W.-L. Preferential rifting of continents: a source of displaced terranes. J. Geophys. Res. 89, 10072–10076 (1984).

    Google Scholar 

  22. 22.

    Wernicke, B. Uniform-sense normal simple shear of the continental lithosphere. Can. J. Earth Sci. 22, 108–125 (1985).

    Google Scholar 

  23. 23.

    Lynch, H. D. & Morgan, P. The tensile strength of the lithosphere and the localization of extension. Geol. Soc. Lond. Spec. Publ. 28, 53–65 (1987).

    Google Scholar 

  24. 24.

    Molnar, P. Continental tectonics in the aftermath of plate tectonics. Nature 335, 131–137 (1988).

    Google Scholar 

  25. 25.

    Ranalli, G. & Murphy, D. C. Rheological stratification of the lithosphere. Tectonophysics 132, 281–295 (1987).

    Google Scholar 

  26. 26.

    Kohlstedt, D. L., Evans, B. & Mackwell, S. J. Strength of the lithosphere: constraints imposed by laboratory experiments. J. Geophys. Res. 100, 17587 (1995).

    Google Scholar 

  27. 27.

    van den Broek, J. M. & Gaina, C. Microcontinents and continental fragments associated with subduction systems. Tectonics 39, e2020TC006063 (2020).

    Google Scholar 

  28. 28.

    Gleason, G. C. & Tullis, J. A flow law for dislocation creep of quartz aggregates determined with the molten salt cell. Tectonophysics 247, 1–23 (1995).

    Google Scholar 

  29. 29.

    Mackwell, S. J., Zimmerman, M. E. & Kohlstedt, D. L. High-temperature deformation of dry diabase with application to tectonics on Venus. J. Geophys. Res. Solid Earth 103, 975–984 (1998).

    Google Scholar 

  30. 30.

    Davies, J. H. & von Blanckenburg, F. Slab breakoff: a model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens. Earth Planet. Sci. Lett. 129, 85–102 (1995).

    Google Scholar 

  31. 31.

    van Hunen, J. & Allen, M. B. Continental collision and slab break-off: a comparison of 3-D numerical models with observations. Earth Planet. Sci. Lett. 302, 27–37 (2011).

    Google Scholar 

  32. 32.

    Freeburn, R., Bouilhol, P., Maunder, B., Magni, V. & van Hunen, J. Numerical models of the magmatic processes induced by slab breakoff. Earth Planet. Sci. Lett. 478, 203–213 (2017).

    Google Scholar 

  33. 33.

    Molnar, P. & Gray, D. Subduction of continental lithosphere: some constraints and uncertainties. Geology 7, 58 (1979).

    Google Scholar 

  34. 34.

    Coward, M. & Dietrich, D. Alpine tectonics—an overview. Geol. Soc. Lond. Spec. Publ. 45, 1–29 (1989).

    Google Scholar 

  35. 35.

    Rosenbaum, G. & Lister, G. S. The Western Alps from the Jurassic to Oligocene: spatio-temporal constraints and evolutionary reconstructions. Earth Sci. Rev. 69, 281–306 (2005).

    Google Scholar 

  36. 36.

    Manzotti, P., Ballèvre, M., Zucali, M., Robyr, M. & Engi, M. The tectonometamorphic evolution of the Sesia–Dent Blanche nappes (internal Western Alps): review and synthesis. Swiss J. Geosci. 107, 309–336 (2014).

    Google Scholar 

  37. 37.

    Babist, J., Handy, M. R., Konrad-Schmolke, M. & Hammerschmidt, K. Precollisional, multistage exhumation of subducted continental crust: the Sesia Zone, western Alps. Tectonics 25, TC6008 (2006).

    Google Scholar 

  38. 38.

    Oberhänsli, R., Hunziker, J. C., Martinotti, G. & Stern, W. B. Geochemistry, geochronology and petrology of Monte Mucrone: an example of EO-alpine eclogitization of Permian granitoids in the Sesia–Lanzo Zone, Western Alps, Italy. Chem. Geol. Isot. Geosci. 52, 165–184 (1985).

    Google Scholar 

  39. 39.

    Zucali, M., Spalla, M. I. & Gosso, G. Strain partitioning and fabric evolution as a correlation tool: the example of the eclogitic micaschists complex in the Sesia–Lanzo Zone (Monte Mucrone–Monte Mars, Western Alps, Italy). Schweiz. Mineral. Petrogr. Mitteil. 82, 429–454 (2002).

    Google Scholar 

  40. 40.

    Regis, D. et al. Multiple metamorphic stages within an eclogite-facies terrane (Sesia zone, Western Alps) revealed by Th–U–Pb petrochronology. J. Petrol. 55, 1429–1456 (2014).

    Google Scholar 

  41. 41.

    Rubatto, D. et al. Yo-yo subduction recorded by accessory minerals in the Italian Western Alps. Nat. Geosci. 4, 338–342 (2011).

    Google Scholar 

  42. 42.

    Hsü, K. J. Time and place in Alpine orogenesis—the Fermor Lecture. Geol. Soc. Spec. Publ. 45, 421–443 (1989).

    Google Scholar 

  43. 43.

    Hunziker, J. C., Desmons, J. & Martinotti, G. Alpine thermal evolution in the central and the western Alps. Geol. Soc. Spec. Publ. 45, 353–367 (1989).

    Google Scholar 

  44. 44.

    Torsvik, T. H. et al. Phanerozoic polar wander, palaeogeography and dynamics. Earth Sci. Rev. 114, 325–368 (2012).

    Google Scholar 

  45. 45.

    van Hinsbergen, D. J. J. et al. Tectonic evolution and paleogeography of the Kirsehir Block and the Central Anatolian Ophiolites, Turkey. Tectonics 35, 983–1014 (2016).

    Google Scholar 

  46. 46.

    Okay, A. I. & Şahintürk, Ö. in Regional and Petroleum Geology of the Black Sea and Surrounding Region (ed. Robinson, A. G.) 291–311 (American Association of Petroleum Geologists, 1997);

  47. 47.

    Schleiffarth, W. K., Darin, M. H., Reid, M. R. & Umhoefer, P. J. Dynamics of episodic Late Cretaceous–Cenozoic magmatism across Central to Eastern Anatolia: new insights from an extensive geochronology compilation. Geosphere 14, 1990–2008 (2018).

    Google Scholar 

  48. 48.

    Agard, P., Omrani, J., Jolivet, L. & Mouthereau, F. Convergence history across Zagros (Iran): constraints from collisional and earlier deformation. Int. J. Earth Sci. 94, 401–419 (2005).

    Google Scholar 

  49. 49.

    Okay, A. I., Zattin, M. & Cavazza, W. Apatite fission-track data for the Miocene Arabia–Eurasia collision. Geology 38, 35–38 (2010).

    Google Scholar 

  50. 50.

    Rolland, Y. et al. Evidence for ~80–75 Ma subduction jump during Anatolide–Tauride–Armenian block accretion and ~48 Ma Arabia–Eurasia collision in Lesser Caucasus–East Anatolia. J. Geodyn. 56–57, 76–85 (2012).

    Google Scholar 

  51. 51.

    Topuz, G., Candan, O., Zack, T. & Yılmaz, A. East Anatolian plateau constructed over a continental basement: no evidence for the East Anatolian accretionary complex. Geology 45, 791–794 (2017).

    Google Scholar 

  52. 52.

    England, P. & Houseman, G. Extension during continental convergence, with application to the Tibetan Plateau. J. Geophys. Res. 94, 17561 (1989).

    Google Scholar 

  53. 53.

    Uyeda, S. & Kanamori, H. Back-arc opening and the mode of subduction. J. Geophys. Res. 84, 1049 (1979).

    Google Scholar 

  54. 54.

    Heuret, A. & Lallemand, S. Plate motions, slab dynamics and back-arc deformation. Phys. Earth Planet. Inter. 149, 31–51 (2005).

    Google Scholar 

  55. 55.

    Göğüş, O. H. Rifting and subsidence following lithospheric removal in continental back arcs. Geology 43, 3–6 (2015).

    Google Scholar 

  56. 56.

    Ryan, W. B. F. et al. Global multi-resolution topography synthesis. Geochem. Geophys. Geosyst. 10, Q03014 (2009).

    Google Scholar 

  57. 57.

    Göğüş, O. H. & Pysklywec, R. N. Near-surface diagnostics of dripping or delaminating lithosphere. J. Geophys. Res. 113, B11404 (2008).

    Google Scholar 

  58. 58.

    Göğüş, O. H. Geodynamic experiments suggest that mantle plume caused Late Permian Emeishan Large Igneous Province in Southern China. Int. Geol. Rev. (2020).

  59. 59.

    Memiş, C. et al. Long wavelength progressive plateau uplift in Eastern Anatolia since 20 Ma: implications for the role of slab peel‐Back and Break‐off. Geochem. Geophys. Geosyst. 21, e2019GC008726 (2020).

    Google Scholar 

  60. 60.

    Buiter, S. J. H. et al. The numerical sandbox: comparison of model results for a shortening and an extension experiment. Geol. Soc. Lond. Spec. Publ. 253, 29–64 (2006).

    Google Scholar 

  61. 61.

    Buiter, S. J. H. et al. Benchmarking numerical models of brittle thrust wedges. J. Struct. Geol. 92, 140–177 (2016).

    Google Scholar 

  62. 62.

    Chopra, P. N. & Paterson, M. S. The role of water in the deformation of dunite. J. Geophys. Res. Solid Earth 89, 7861–7876 (1984).

    Google Scholar 

  63. 63.

    Hirth, G. & Kohlstedt, D. L. Water in the oceanic upper mantle: implications for rheology, melt extraction and the evolution of the lithosphere. Earth Planet. Sci. Lett. 144, 93–108 (1996).

    Google Scholar 

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This research was enabled in part by support provided by SciNet and Compute Canada ( A modified version of the SOPALE (2000) software was used to run numerical models. The SOPALE modelling code was originally developed by P. Fullsack at Dalhousie University with C. Beaumont and his Geodynamics group. We used Ö. F. Bodur’s script to plot the PTt paths. Funding for this research was provided by an NSERC Discovery Grant (RGPIN-2019-06803)-RNP and TÜBİTAK grant (114Y226) to G.T.

Author information




E.G. designed and carried out the numerical experiments and interpreted the results with R.N.P. O.H.G. and G.T. helped with the geological background of the Alpine–Mediterranean region. E.G. and R.N.P. developed ‘the subduction pulley’ hypothesis and wrote the manuscript with inputs and comments from all the authors.

Corresponding author

Correspondence to Erkan Gün.

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The authors declare no competing interests.

Additional information

Peer review information Nature Geoscience thanks Wim Spakman and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Stefan Lachowycz.

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Extended data

Extended Data Fig. 1 Initial conditions of model EXP-2.

The figure shows dimensions, geometry, materials, geotherm, Eulerian and Lagrangian grid dimensions, and convergence velocity direction. The upper left side of the model box is fixed. The imposed velocity, if present, is applied at the location of the blue arrow by introducing new oceanic lithosphere into the box. Orange arrows show evenly distributed outward flux to compensate inward flux. The red line on the right shows the change of geotherm with depth. The inset table lists experiment numbers according to microcontinent widths and convergence rates.

Extended Data Table 1 The rheological parameters used in experiments EXP-1 to EXP-8

Supplementary information

Supplementary Information

Supplementary Figs. 1–3, Table and Discussion.

Supplementary Video

Supplementary Video illustrates how the subduction pulley operates and yields pre-collisional microcontinent extension using the plots of the EXP-5. The video pauses briefly before the collision to highlight the pre-collisional microcontinent extension.

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Gün, E., Pysklywec, R.N., Göğüş, O.H. et al. Pre-collisional extension of microcontinental terranes by a subduction pulley. Nat. Geosci. 14, 443–450 (2021).

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