Introduction to the special issue on convergent plate margin dynamics

Convergent plate margins are arguably the most complicated and dynamic plate boundaries on Earth and have been the subject of many investigations and discussions since the advent of plate tectonic theory. Due to the varied, heterogeneous and complex structure of convergent plate margins, which arises from the multiple geological, physical and chemical processes operating at these zones, and because the largest portion of the system is hidden deep beneath the surface, much remains enigmatic and unknown about these important plate tectonic features. As such, numerous fundamental problems still need to be addressed. The papers presented in this special issue provide many new insights into a variety of geological, geophysical and geodynamical problems. Schellart and Rawlinson (2010-this issue) provide a historical background and a review of the development of geological and geodynamic theories on convergent plate margins. Furthermore, the paper discusses some of the recent advances that have been made in the fields of structural geology, geophysics and geodynamics, which are fundamental to our understanding of convergent plate margins. The paper shows that contributions from structural geologists, geophysicists and geodynamic modellers have been crucial for the development of geological theories of large-scale tectonic processes and for the understanding of convergent plate boundaries. A topic of active research is the initiation of a new subduction zone, which has been suggested to occur at passivemargins due to sediment loading (Cloetingh et al., 1982; Regenauer-Lieb et al., 2001), at fracture zones due to far-field compressive stresses thereby forcing convergence across the lithospheric heterogeneity (Hall et al., 2003; Gurnis et al., 2004), or at passivemargins due to large buoyancy forces across the passivemargin (Mart et al., 2005; Goren et al., 2008). In this special issue, Farrington et al. (2010-this issue) present numerical models that illustrate plate motion-induced edge-driven convection below a lithospheric step at a passive margin. This vigorous convection could facilitate thermal weakening of the passive margin lithosphere and might induce deviatoric stresses across the margin. Such edge-driven convection could thus facilitate and play a role in subduction initiation at passive margins. After a critical amount of subduction (100–150 km) a selfsustaining subduction zone forms (Gurnis et al., 2004). The subsequent kinematic and dynamic evolution of the system will depend on the different physical parameters that control the system. Various controlling parameters have been proposed, including mantle stratification (Kincaid and Olson, 1987; Christensen, 1996), slab strength (Capitanio et al., 2007; Billen and Hirth, 2007; Di Giuseppe et al., 2008; Schellart, 2008a; Funiciello et al., 2008), slab negative buoyancy (Molnar and Atwater, 1978; Schellart, 2004; Morra et al., 2006; Capitanio et al., 2007), subducting plate velocity (Funiciello et al., 2004; Schellart, 2005), overriding plate velocity (Olbertz et al., 1997; van Hunen et al., 2000; Heuret et al., 2007; Guillaume et al., 2009), and