Subduction Initiation by Plume‐Plateau Interaction: Insights From Numerical Models

Abstract

It has recently been demonstrated that the interaction of a mantle plume with sufficiently old oceanic lithosphere can initiate subduction. However, the existence of large lithospheric heterogeneities, such as a buoyant plateau, in proximity to a rising plume head may potentially hinder the formation of a new subduction zone. Here, we investigate this scenario by means of 3‐D numerical thermomechanical modeling. We explore how plume‐lithosphere interaction is affected by lithospheric age, relative location of plume head and plateau border, and the strength of the oceanic crust. Our numerical experiments suggest four different geodynamic regimes: (a) oceanic trench formation, (b) circular oceanic‐plateau trench formation, (c) plateau trench formation, and (d) no trench formation. We show that regardless of the age and crustal strength of the oceanic lithosphere, subduction can initiate when the plume head is either below the plateau border or at a distance less than the plume radius from the plateau edge. Crustal heterogeneity facilitates subduction initiation of old oceanic lithosphere. High crustal strength hampers the formation of a new subduction zone when the plume head is located below a young lithosphere containing a thick and strong plateau. We suggest that plume‐plateau interaction in the western margin of the Caribbean could have resulted in subduction initiation when the plume head impinged onto the oceanic lithosphere close to the border between plateau and oceanic crust.

Plume‐Induced Sinking of Intracontinental Lithospheric Mantle: An Overlooked Mechanism of Subduction Initiation?

“…Under the condition that the continent is relatively young (Cenozoic‐Mesozoic, LAB <150 km), subduction initiation occurs only when the mantle plume is sufficiently hot (and therefore buoyant) to penetrate through the entire lithosphere, and dragging its broken segments into the mantle with a downward motion (Burov & Cloetingh, 2009, 2010). This mechanism is consistent with findings from numerous studies of intra‐oceanic settings (Ueda et al., 2008; Gerya et al., 2015; Baes et al., 2016, 2020a, 2020b), where subduction develops exclusively in combination with preceding break‐up of the lithosphere by ultra‐fast (<0.1 Myr) uplift of plume material to the surface. If, however, the strength of oceanic lithosphere above the plume anomaly overcomes its thermal and/or compositional buoyancy, “plume underplating” (i.e., lateral spreading of the plume head beneath the plate) without subduction initiation becomes the dominant mode (e.g., Baes et al., 2016).…”

“…A radically different conceptual framework for understanding subduction triggering processes has come from studies investigating mantle plume-lithosphere interactions. As shown in 2D (Ueda et al, 2008;Burov & Cloetingh, 2009 and 3D (Gerya et al, 2015;Baes et al, 2016Baes et al, , 2020aBaes et al, , 2020b modeling studies, the emplacement of a thermo-(chemical) mantle plume anomaly beneath an oceanic (Ueda et al, 2008;Gerya et al, 2015;Baes et al, 2016Baes et al, , 2020aBaes et al, , 2020b or continental (Burov & Cloetingh, 2009 plate appears to trigger self-sustained subduction, even in the absence of both kinematic boundary conditions and initially pre-defined intra-lithospheric heterogeneities/weaknesses. According to the scenario first proposed by Ueda et al (2008), a hot and positively buoyant plume rises to the oceanic lithosphere ( Figure 2a1) and then quickly passes through it, ultimately leading to crustal break-up ( Figure 2a2).…”

“…Plume‐induced subduction initiation within oceanic lithosphere has received significant attention in modern geodynamic research (Ueda et al., 2008; Gerya et al., 2015; Lu et al., 2015; Baes et al., 2016, 2020a, 2020b) unlike a paucity of studies in continental settings. Since the studies by Burov & Cloetingh (2009, 2010), no new attempts have been made to investigate plume‐lithosphere interaction as the driving mechanism for subduction‐like downward movements of the continental lithosphere.…”

“…Despite numerous intra‐oceanic “hot‐spots” (Courtillot et al., 2003), only one of them has triggered subduction around the Caribbean plate in the Late Cretaceous (Whattam, 2018; Whattam & Stern, 2015), whereas in all other cases no proven hot spot‐related ocean‐ocean subduction has been detected so far. One of the most prominent “negative” examples is the North Atlantic Igneous Province (Saunders et al., 1997) associated with the Iceland plume that 1) produces melt during most of the past 60 Myr (e.g., Kerr, 2003), thus contributing to melt‐induced magmatic weakening of the overlying plate, which is typically the most important condition for plume‐induced subduction (Ueda et al., 2008, Gerya et al., 2015; Baes et al., 2016, 2020a, 2020b); 2) has presumably triggered the opening of the North Atlantic Ocean at ∼60 Ma (Beniest et al., 2017b) and caused the active spreading axis to jump from the Aegir ridge to the Kolbeinsey ridge at ∼30–35 Ma (Koptev et al., 2017), thus attesting a sufficiently high buoyancy of the plume to overcome the strength of not only oceanic but even continental lithosphere; 3) channeled along the thin‐lithosphere corridors underneath continental lithosphere and the mid‐oceanic ridges (Steinberger et al., 2019); 4) presently extends not only along the mid‐oceanic ridge but also in perpendicular directions (see seismic tomography by Rickers et al., 2013 and laboratory and numerical experiments by Schoonman et al., 2017 and Koptev et al., 2017, respectively), thus impinging oceanic lithosphere of ages older than 20 Ma as required for the formation of stable subduction zones in numerical experiments (Baes et al., 2016; Lu et al., 2015). For these reasons, the Iceland plume seems to satisfy all principal model prerequisites for the initiation of stable subduction within the North Atlantic oceanic lithosphere: 1) intensive plume‐induced magmatism likely lowering the strength of the overlying plate, 2) sufficient buoyancy of the thermo‐(chemical) plume anomaly, and 3) interaction with oceanic lithosphere of ages exceeding 20 Ma.…”

“…Originally, given a lack of known present-day analogs, significant weakening of the lithosphere caused by upward migration of the melts extracted from the plume was not thought to be feasible in the Phanerozoic Earth, limiting the applicability of this mechanism to the hotter Archean lithosphere and circular corona structures on Venus (Gerya et al, 2015;Gülcher et al, 2020;Ueda et al, 2008). However, Whattam and Stern (2015) recently provided compelling evidence for plume-induced subduction initiation along the southern margin of the Caribbean and northwestern South America in the Late Cretaceous, thus inspiring new numerical studies to explore this mechanism in the context of modern Earth as well (Baes et al, 2016(Baes et al, , 2020a(Baes et al, , 2020b).…”