Plume‐Induced Subduction Initiation: Single‐Slab or Multi‐Slab Subduction?

Abstract

Initiation of subduction following the impingement of a hot buoyant mantle plume is one of the few scenarios that allow breaking the lithosphere and recycling a stagnant lid without requiring any preexisting weak zones. Here, we investigate factors controlling the number and shape of retreating subducting slabs formed by plume‐lithosphere interaction. Using 3‐D thermomechanical models we show that the deformation regime, which defines formation of single‐slab or multi‐slab subduction, depends on several parameters such as age of oceanic lithosphere, thickness of the crust and large‐scale lithospheric extension rate. Our model results indicate that on present‐day Earth multi‐slab plume‐induced subduction is initiated only if the oceanic lithosphere is relatively young (<30–40 Myr, but >10 Myr), and the crust has a typical thickness of 8 km. In turn, development of single‐slab subduction is facilitated by older lithosphere and pre‐imposed extensional stresses. In early Earth, plume‐lithosphere interaction could have led to formation of either episodic short‐lived circular subduction when the oceanic lithosphere was young or to multi‐slab subduction when the lithosphere was old.

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

“…Figure 7 summarizes how the four described geodynamic regimes (i.e., different lithospheric responses to plume-plateau interaction) depend on the initial plume placement, age of the lithosphere, and crustal strength. We note that previous studies have examined the effect of parameters such as plume buoyancy, which depends on volume, temperature, and composition of the plume, strength of the lithosphere, and lithospheric heterogeneities (i.e., the existence of a weak zone within the lithosphere or large extensional/compressional regimes) on the lithospheric response to plume impingement (Baes et al, 2016(Baes et al, , 2020Gerya et al, 2015). Our experiments show that regardless of the crustal strength or age of the lithosphere, oceanic subduction initiates if (1) the plume head is located directly below the plateau border or (2) it impinges the lithosphere at a distance from the plateau edge of less than the plume radius (100 km in our experiments; Figure 7a).…”

“…At this time, the plume penetrated the lithosphere, and the heterogeneity of the crustal thickness helped initiate the subduction of the old (and hence strong) Farallon plate (Figure 9c). We do not, however, exclude other factors that were suggested by previous studies such as interaction of a plume with a lithosphere with normal crustal thickness (i.e.,~8 km) and plume-plateau interaction under extensional regimes (Baes et al, 2020) or the existence of subduction in the northeast margin (Whattam & Stern, 2014) as possible causes of the formation of a curved trench in the western margin of Caribbean.…”

“…The parameters controlling the development of these deformation regimes are brittle/plastic strength and age of the oceanic lithosphere, the presence/absence of lithospheric heterogeneity, and buoyancy of the plume, which depends on the size, composition, and temperature of the plume. Baes et al (2020) conducted a numerical modeling study, in which they investigated the factors controlling the shape of plume-induced subduction zones. They show that the development of single-slab or multi-slab subduction depends on several parameters such as age of oceanic lithosphere, thickness of the crust, mantle temperature, and large-scale lithospheric extension.…”

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

“…Different from drastically reduced yield stresses adopted in models for the oceanic lithosphere that is presumably weakened by intense magmatic activity of the plume (Ueda et al., 2008; Gerya et al., 2015; Baes et al., 2016, 2020a, 2020b), the parameters of elastic‐ductile‐plastic rheology laws for crust and mantle of the continental lithosphere in the study by Burov & Cloetingh (2009, 2010) are based on experimentally derived estimates for the rock mechanical properties (Kirby & Kronenberg, 1987; Kohlstedt et al., 1995), and were not subject to further lowering due to the effects of strain‐ (Brune & Autin, 2013; Gueydan et al., 2008; Huismans & Beaumont, 2003) and/or melt‐related softening (Bahadori & Holt, 2019; Gerya et al., 2015; Gerya & Meilick, 2011; Lavecchia et al., 2016). This means that mantle plume ascent through the entire plate as reproduced in the models for relatively young continents (Figures 2b1 and 2b2) is mostly due to the significantly positive buoyancy of the plume head (Δρ ∼100–120 kg × m −3 ), mainly associated to the high thermal contrast between the plume itself and its surrounding material (up to +1,000°C when emplaced below the lithosphere).…”

“…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.…”