Plume-plateau interaction: Insight from numerical modelling

In attempt to better understand subduction initiation, several studies have been carried out so far (e.g., McKenzie, 1977; Stern, 2004; Baes et al., 2011; Stern and Gerya, 2017). Most of previous studies have signified the vital role of a pre-existing lithospheric weakness, which is itself the product of plate tectonics, in subduction initiation (McKenzie, 1977; Mueller and Phillips, 1991; Gurnis et al., 2004; Gerya et al, 2008). A recently proposed scenario that is independent of any pre-existing weakness zone is plume-induced subduction initiation, which can explain the appearance of the first subduction zone without the help of plate tectonics (Ueda et al., 2008; Gerya et al., 2015; Baes et al., 2016). According to this scenario, the arrival of a buoyant plume beneath oceanic lithosphere can result in the formation of several retreating slabs around a newly formed plateau. However, many key aspects of this new scenario have not been studied yet. Here, we investigate some of these unexplored scenarios including interaction of plume with strongly heterogeneous oceanic lithosphere (e.g. containing oceanic plateau) and study factors controlling lithospheric deformation. We also investigate the impact of regional extension on this process. The outcomes of this work help us to better understand the deformation mechanisms in natural examples of plume-plateau interaction including deformation at south-western margin of the Caribbean plate, where arrival of a buoyant plume beneath the plateau likely resulted in subduction initiation at 100 Mya (Whattam and Stern, 2015).

Using 3-d numerical models, which are carried out with a thermal-mechanical finite-difference code, we find out that the response of lithosphere to arrival of plume depends on several parameters such as thickness of crust and age of oceanic lithosphere. Besides these parameters, the rate of lithospheric extension plays also a key role in lithospheric deformation.