Keywords: subduction mantle plume analog modelling mantle flow slab rollback We present three-dim... more Keywords: subduction mantle plume analog modelling mantle flow slab rollback We present three-dimensional deep-mantle laboratory models of a compositional plume within the vicinity of a buoyancy-driven subducting plate with a fixed trailing edge. We modelled front plumes (in the mantle wedge), rear plumes (beneath the subducting plate) and side plumes with slab/plume systems of buoyancy flux ratio spanning a range from 2 to 100 that overlaps the ratios in nature of 0.2–100. This study shows that 1) rising side and front plumes can be dragged over thousands of kilometres into the mantle wedge, 2) flattening of rear plumes in the trench-normal direction can be initiated 700 km away from the trench, and a plume material layer of lesser density and viscosity can ultimately almost entirely underlay a retreating slab after slab/plume impact, 3) while side and rear plumes are not tilted until they reach ∼600 km depth, front plumes can be tilted at increasing depths as their plume buoyancy is lessened, and rise at a slower rate when subjected to a slab-induced downwelling, 4) rear plumes whose buoyancy flux is close to that of a slab, can retard subduction until the slab is 600 km long, and 5) slab– plume interaction can lead to a diversity of spatial plume material distributions into the mantle wedge. We discuss natural slab/plume systems of the Cascadia/Bowie–Cobb, and Nazca/San Felix–Juan Fernandez systems on the basis of our experiments and each geodynamic context and assess the influence of slab downwelling at depths for the starting plumes of Java, Coral Sea and East Solomon. Overall, this study shows how slab/plume interactions can result in a variety of geological, geophysical and geochemical signatures.
S U M M A R Y Recent evidence suggests that a portion of the Canary plume travelled northeastward... more S U M M A R Y Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ∼10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab–plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 × 1350 km 2. While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume–Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.
The interaction between mantle plumes and subducting slabs is well accepted, but the influence of... more The interaction between mantle plumes and subducting slabs is well accepted, but the influence of slabs on plumes has more often been portrayed than the reverse. Here we present three-dimensional upper mantle laboratory models in which a compositional plume rises underneath a subducting plate. Slab/plume buoyancy flux ratios ranged between 7 and 18. The models exhibit a two-way interaction. While the plume conduit increasingly tilts away from the trench as a result of slab rollback-induced toroidal mantle flow, the slab subduction rate decreases as a function of the amount of plume buoyancy opposing that of the slab, which gets subducted beneath the slab. We propose that our models apply to the Hainan/Manila system and explain the recently imaged tilt of the Hainan plume by the Manila slab-induced mantle return flow. The Hainan plume could lessen the Manila subduction rate from 8 Ma into the future.
Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench mi... more Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.
Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle 1... more Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle 1-4 , and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subductioninduced flow 3-15 . Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel extent 3,5,6 (that is, two-dimensional) or finite in width but fixed in space 7,16 . Subduction zones and their associated slabs are, however, limited in lateral extent (250-7,400 km) and their three-dimensional geometry evolves over time. Here we show that slab width controls two first-order features of plate tectonics-the curvature of subduction zones and their tendency to retreat backwards with time. Using three-dimensional numerical simulations of free subduction, we show that trench migration rate is inversely related to slab width and depends on proximity to a lateral slab edge. These results are young (#5 Myr), have a short slab (#150 km) and, together with collision zones, have been excluded from the trench migration calculations in . Trench migration rates for incipient subduction zones are presented in .
1] Subduction of tectonic plates limited in lateral extent and with a free-trailing tail, i.e., '... more 1] Subduction of tectonic plates limited in lateral extent and with a free-trailing tail, i.e., ''free subduction,'' is modeled in a three-dimensional (3-D) geometry. The models use a nonlinear viscoplastic rheology for the subducting plate and exhibit a wide range of behaviors depending on such plate characteristics as strength, width, and thickness. We investigate the time evolution of this progressive rollback subduction, measure the accompanying return flow in the upper mantle, and quantify the plate kinematics. Due to the 3-D geometry, flow is allowed to accompany slab rollback around the lateral edges of the slab (the toroidal component), as opposed to 2-D geometry, where material is forced to flow underneath the slab tip (the poloidal component). A simple force balance is provided which relates the speed of backward trench migration to the resistive forces of generating flow and weakening the plate. Our results indicate most of the gravitational energy of the system (i.e., the negative buoyancy of the subducting slab) is converted into a toroidal flow ($69%), a much smaller amount goes into weakening the plate ($18%), and the remaining amount goes into driving flow parallel to displacement of the slab ($13%). For the trench widths (W) we investigate ( 1500 km), a maximum trench retreat rate occurs for trenches 600 km wide, which is attributed to the interaction between a plate of finite width and the induced flow (which has a lengthscale in the horizontal direction). These numerical results quantitatively agree with comparable 3-D laboratory experiments using analogue models with a purely viscous plate material , including correlations between increasing retreat rate with increasing plate thickness, trench width for maximum retreat rate (500 km), and estimated amount of slab buoyancy used to drive rollback-induced flow ($70%). Several implications for plate tectonics on Earth result from these models such as rollback subduction providing a physical mechanism for ephemeral slab graveyards situated above the more viscous lower mantle (and endothermic phase transition) prior to a flushing event into the lower mantle (mantle avalanche).
There are approximately 50 distinct segments of subduction zones in the world, of which 40% have ... more There are approximately 50 distinct segments of subduction zones in the world, of which 40% have oceanic lithosphere subducting under oceanic lithosphere. All of these ocean-ocean systems are currently experiencing hinge-rollback, with the exception of 2 (Mariana and Kermadec). In hinge-rollback, the surface trace of the suduction zone (trench) is moving in the opposite direction as the plate is moving
Previous models of subduction (both analogue and numerical) have observed a number of distinct st... more Previous models of subduction (both analogue and numerical) have observed a number of distinct styles of subduction, each with particular subduction motions (partitioned between slab rollback and forward plate advance) and associated slab morphologies. We use 3-D numerical models to investigate subduction dynamics by varying the strength of slabs as well as the buoyancy, and propose a new classification based on these parameters. The slab strength is specified both through the ratio of viscosities between the subducting plate and upper mantle (η plate /η um ) as well as the plate thickness, h plate . Only a very restrictive range of plates ("strong" plates with smaller buoyancy) tend to favor modes of subduction which are exclusively advancing. Plates which have greater negative buoyancy will eventually transition into a retreating style. We find that the flexural strength and the buoyancy determine the subduction style (as distinguished by a characteristic slab morphology), and control several subduction characteristics including the partitioning between slab rollback and plate advance, the trench curvature, and the slab's radius of curvature. Plates that are 80-100 km thick with η plate /η um~1 00-300 are classified here as "weak" and are the only plates to exhibit slab geometry with several recumbent folds atop the more viscous lower mantle. This regime of weak plates with their associated slab morphologies (predominant folding) is argued to be most similar to slabs on Earth based on the presence of folded slab piles in Earth's upper mantle (as interpreted from seismic tomography).
Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench mi... more Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.
1] Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and t... more 1] Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and trench retreat. We investigate how subducting plate velocity, trench velocity and the partitioning of these two velocity components vary for individual subduction zone segments as a function of proximity to the closest lateral slab edge (D SE ). We present a global compilation for 207 trench segments from 17 active subduction zones on Earth and three-dimensional numerical models of progressive free subduction of a single oceanic plate that subducts into a stratified mantle. The results show that the subducting plate velocity is always high (≥5.1 cm/yr (models) and ≥4.2 cm/yr (nature)) and trench velocity is always low (≤2.5 cm/yr (models) and ≤1.7 cm/yr (nature)) in the center of wide subduction zones (D SE > 2200 km). Only in regions close to lateral slab edges (D SE < 1000 km), be it for narrow or wide subduction zones, can the trench velocity exceed 4 cm/yr (models) and 6 cm/yr (nature) and can the subducting plate velocity go below 4 cm/yr (models) and 2 cm/yr (nature). In general, plate velocities, trench velocities and subduction partitioning are much more variable near slab edges than in the center of wide subduction zones owing to other parameters that affect subduction kinematics. We conclude that subduction kinematics can vary considerably along individual subduction zones and that the upper bound values for trench velocity and lower bound values for subducting plate velocity and subduction partitioning at individual subduction zone segments depend critically on D SE .
There are approximately 50 distinct segments of subduction zones in the world, of which 40% have ... more There are approximately 50 distinct segments of subduction zones in the world, of which 40% have oceanic lithosphere subducting under oceanic lithosphere. All of these ocean-ocean systems are currently experiencing hinge-rollback, with the exception of 2 (Mariana and Kermadec). In hinge-rollback, the surface trace of the suduction zone (trench) is moving in the opposite direction as the plate is moving
Subducting slabs provide the main driving force for plate tectonics and flow in the Earth&amp... more Subducting slabs provide the main driving force for plate tectonics and flow in the Earth&amp;amp;amp;amp;amp;amp;#39;s mantle. Geodynamic modeling provides insight into the kinematics and dynamics of subduction. Many previous numerical studies modeled subduction either in 2D space or in 3D space with essentially static models. Many early laboratory simulations of subduction only focused on 2D aspects of the modeling. In
ABSTRACT Subduction of tectonic plates into the Earth&#39;s mantle is accommodated by subduct... more ABSTRACT Subduction of tectonic plates into the Earth&#39;s mantle is accommodated by subducting plate motion and trench migration. How these two modes contribute to the subduction velocity and what controls their partitioning remain unsolved. Here we present a global compilation for 17 active subduction zones and three-dimensional numerical models of progressive free subduction showing that slab width (W) provides a first-order control on subduction partitioning, subducting plate velocity and trench velocity. In nature, subducting plate velocity increases progressively from -1 to 3 cm/yr for W = 300-600 km to 5-7 cm/yr for W = 7000 km, while the models show an increase from 2.5-3 cm/yr to 6 cm/yr. Furthermore, trench velocity decreases from 1-7 cm/yr for W = 300-600 km to -1 to 1 cm/yr for W = 7000 km in nature, whilst the models show an decrease from 6-7 cm/yr to ~1.5 cm/yr. The subduction zone data, numerical models and a scaling formulation for sinking of slabs in the upper mantle show that subducting plate velocity scales with ~Wexp(2/3), while trench velocity scales with ~1/W. Correlation coefficients for the numerical models with respect to the scaling formulation are in the range 0.95-0.99 for subducting plate velocity, trench velocity and subduction partitioning, while those for the natural data are in the range 0.70-0.72. It is thus found that slab width provides a first-order control plate velocity, trench velocity and subduction partitioning. Comparison of slab age and subduction kinematics for natural subduction zones gives significantly lower correlation coefficients (0.29-0.38), indicating that slab age provides a second-order control on trench velocity and subducting plate velocity. Our findings provide an explanation for the Cenozoic progressive decrease in subducting plate velocity and subduction partitioning of the Farallon plate, which we interpret as resulting from the progressive decrease in trench-parallel width of the Farallon slab during the Cenozoic from ~14000 km to only 1400 km at present. This decrease in slab width also explains the change from Sevier-Laramide orogenesis to Basin and Range extension in North America in the Eocene to Miocene. Shortening took place during wide-slab subduction and overriding-plate-driven trench retreat (push-back), whilst extension took place during intermediate to narrow-slab subduction and slab-driven trench retreat (pull-back).
Keywords: subduction mantle plume analog modelling mantle flow slab rollback We present three-dim... more Keywords: subduction mantle plume analog modelling mantle flow slab rollback We present three-dimensional deep-mantle laboratory models of a compositional plume within the vicinity of a buoyancy-driven subducting plate with a fixed trailing edge. We modelled front plumes (in the mantle wedge), rear plumes (beneath the subducting plate) and side plumes with slab/plume systems of buoyancy flux ratio spanning a range from 2 to 100 that overlaps the ratios in nature of 0.2–100. This study shows that 1) rising side and front plumes can be dragged over thousands of kilometres into the mantle wedge, 2) flattening of rear plumes in the trench-normal direction can be initiated 700 km away from the trench, and a plume material layer of lesser density and viscosity can ultimately almost entirely underlay a retreating slab after slab/plume impact, 3) while side and rear plumes are not tilted until they reach ∼600 km depth, front plumes can be tilted at increasing depths as their plume buoyancy is lessened, and rise at a slower rate when subjected to a slab-induced downwelling, 4) rear plumes whose buoyancy flux is close to that of a slab, can retard subduction until the slab is 600 km long, and 5) slab– plume interaction can lead to a diversity of spatial plume material distributions into the mantle wedge. We discuss natural slab/plume systems of the Cascadia/Bowie–Cobb, and Nazca/San Felix–Juan Fernandez systems on the basis of our experiments and each geodynamic context and assess the influence of slab downwelling at depths for the starting plumes of Java, Coral Sea and East Solomon. Overall, this study shows how slab/plume interactions can result in a variety of geological, geophysical and geochemical signatures.
S U M M A R Y Recent evidence suggests that a portion of the Canary plume travelled northeastward... more S U M M A R Y Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ∼10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab–plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 × 1350 km 2. While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume–Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.
The interaction between mantle plumes and subducting slabs is well accepted, but the influence of... more The interaction between mantle plumes and subducting slabs is well accepted, but the influence of slabs on plumes has more often been portrayed than the reverse. Here we present three-dimensional upper mantle laboratory models in which a compositional plume rises underneath a subducting plate. Slab/plume buoyancy flux ratios ranged between 7 and 18. The models exhibit a two-way interaction. While the plume conduit increasingly tilts away from the trench as a result of slab rollback-induced toroidal mantle flow, the slab subduction rate decreases as a function of the amount of plume buoyancy opposing that of the slab, which gets subducted beneath the slab. We propose that our models apply to the Hainan/Manila system and explain the recently imaged tilt of the Hainan plume by the Manila slab-induced mantle return flow. The Hainan plume could lessen the Manila subduction rate from 8 Ma into the future.
Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench mi... more Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.
Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle 1... more Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle 1-4 , and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subductioninduced flow 3-15 . Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel extent 3,5,6 (that is, two-dimensional) or finite in width but fixed in space 7,16 . Subduction zones and their associated slabs are, however, limited in lateral extent (250-7,400 km) and their three-dimensional geometry evolves over time. Here we show that slab width controls two first-order features of plate tectonics-the curvature of subduction zones and their tendency to retreat backwards with time. Using three-dimensional numerical simulations of free subduction, we show that trench migration rate is inversely related to slab width and depends on proximity to a lateral slab edge. These results are young (#5 Myr), have a short slab (#150 km) and, together with collision zones, have been excluded from the trench migration calculations in . Trench migration rates for incipient subduction zones are presented in .
1] Subduction of tectonic plates limited in lateral extent and with a free-trailing tail, i.e., '... more 1] Subduction of tectonic plates limited in lateral extent and with a free-trailing tail, i.e., ''free subduction,'' is modeled in a three-dimensional (3-D) geometry. The models use a nonlinear viscoplastic rheology for the subducting plate and exhibit a wide range of behaviors depending on such plate characteristics as strength, width, and thickness. We investigate the time evolution of this progressive rollback subduction, measure the accompanying return flow in the upper mantle, and quantify the plate kinematics. Due to the 3-D geometry, flow is allowed to accompany slab rollback around the lateral edges of the slab (the toroidal component), as opposed to 2-D geometry, where material is forced to flow underneath the slab tip (the poloidal component). A simple force balance is provided which relates the speed of backward trench migration to the resistive forces of generating flow and weakening the plate. Our results indicate most of the gravitational energy of the system (i.e., the negative buoyancy of the subducting slab) is converted into a toroidal flow ($69%), a much smaller amount goes into weakening the plate ($18%), and the remaining amount goes into driving flow parallel to displacement of the slab ($13%). For the trench widths (W) we investigate ( 1500 km), a maximum trench retreat rate occurs for trenches 600 km wide, which is attributed to the interaction between a plate of finite width and the induced flow (which has a lengthscale in the horizontal direction). These numerical results quantitatively agree with comparable 3-D laboratory experiments using analogue models with a purely viscous plate material , including correlations between increasing retreat rate with increasing plate thickness, trench width for maximum retreat rate (500 km), and estimated amount of slab buoyancy used to drive rollback-induced flow ($70%). Several implications for plate tectonics on Earth result from these models such as rollback subduction providing a physical mechanism for ephemeral slab graveyards situated above the more viscous lower mantle (and endothermic phase transition) prior to a flushing event into the lower mantle (mantle avalanche).
There are approximately 50 distinct segments of subduction zones in the world, of which 40% have ... more There are approximately 50 distinct segments of subduction zones in the world, of which 40% have oceanic lithosphere subducting under oceanic lithosphere. All of these ocean-ocean systems are currently experiencing hinge-rollback, with the exception of 2 (Mariana and Kermadec). In hinge-rollback, the surface trace of the suduction zone (trench) is moving in the opposite direction as the plate is moving
Previous models of subduction (both analogue and numerical) have observed a number of distinct st... more Previous models of subduction (both analogue and numerical) have observed a number of distinct styles of subduction, each with particular subduction motions (partitioned between slab rollback and forward plate advance) and associated slab morphologies. We use 3-D numerical models to investigate subduction dynamics by varying the strength of slabs as well as the buoyancy, and propose a new classification based on these parameters. The slab strength is specified both through the ratio of viscosities between the subducting plate and upper mantle (η plate /η um ) as well as the plate thickness, h plate . Only a very restrictive range of plates ("strong" plates with smaller buoyancy) tend to favor modes of subduction which are exclusively advancing. Plates which have greater negative buoyancy will eventually transition into a retreating style. We find that the flexural strength and the buoyancy determine the subduction style (as distinguished by a characteristic slab morphology), and control several subduction characteristics including the partitioning between slab rollback and plate advance, the trench curvature, and the slab's radius of curvature. Plates that are 80-100 km thick with η plate /η um~1 00-300 are classified here as "weak" and are the only plates to exhibit slab geometry with several recumbent folds atop the more viscous lower mantle. This regime of weak plates with their associated slab morphologies (predominant folding) is argued to be most similar to slabs on Earth based on the presence of folded slab piles in Earth's upper mantle (as interpreted from seismic tomography).
Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench mi... more Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.
1] Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and t... more 1] Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and trench retreat. We investigate how subducting plate velocity, trench velocity and the partitioning of these two velocity components vary for individual subduction zone segments as a function of proximity to the closest lateral slab edge (D SE ). We present a global compilation for 207 trench segments from 17 active subduction zones on Earth and three-dimensional numerical models of progressive free subduction of a single oceanic plate that subducts into a stratified mantle. The results show that the subducting plate velocity is always high (≥5.1 cm/yr (models) and ≥4.2 cm/yr (nature)) and trench velocity is always low (≤2.5 cm/yr (models) and ≤1.7 cm/yr (nature)) in the center of wide subduction zones (D SE > 2200 km). Only in regions close to lateral slab edges (D SE < 1000 km), be it for narrow or wide subduction zones, can the trench velocity exceed 4 cm/yr (models) and 6 cm/yr (nature) and can the subducting plate velocity go below 4 cm/yr (models) and 2 cm/yr (nature). In general, plate velocities, trench velocities and subduction partitioning are much more variable near slab edges than in the center of wide subduction zones owing to other parameters that affect subduction kinematics. We conclude that subduction kinematics can vary considerably along individual subduction zones and that the upper bound values for trench velocity and lower bound values for subducting plate velocity and subduction partitioning at individual subduction zone segments depend critically on D SE .
There are approximately 50 distinct segments of subduction zones in the world, of which 40% have ... more There are approximately 50 distinct segments of subduction zones in the world, of which 40% have oceanic lithosphere subducting under oceanic lithosphere. All of these ocean-ocean systems are currently experiencing hinge-rollback, with the exception of 2 (Mariana and Kermadec). In hinge-rollback, the surface trace of the suduction zone (trench) is moving in the opposite direction as the plate is moving
Subducting slabs provide the main driving force for plate tectonics and flow in the Earth&amp... more Subducting slabs provide the main driving force for plate tectonics and flow in the Earth&amp;amp;amp;amp;amp;amp;#39;s mantle. Geodynamic modeling provides insight into the kinematics and dynamics of subduction. Many previous numerical studies modeled subduction either in 2D space or in 3D space with essentially static models. Many early laboratory simulations of subduction only focused on 2D aspects of the modeling. In
ABSTRACT Subduction of tectonic plates into the Earth&#39;s mantle is accommodated by subduct... more ABSTRACT Subduction of tectonic plates into the Earth&#39;s mantle is accommodated by subducting plate motion and trench migration. How these two modes contribute to the subduction velocity and what controls their partitioning remain unsolved. Here we present a global compilation for 17 active subduction zones and three-dimensional numerical models of progressive free subduction showing that slab width (W) provides a first-order control on subduction partitioning, subducting plate velocity and trench velocity. In nature, subducting plate velocity increases progressively from -1 to 3 cm/yr for W = 300-600 km to 5-7 cm/yr for W = 7000 km, while the models show an increase from 2.5-3 cm/yr to 6 cm/yr. Furthermore, trench velocity decreases from 1-7 cm/yr for W = 300-600 km to -1 to 1 cm/yr for W = 7000 km in nature, whilst the models show an decrease from 6-7 cm/yr to ~1.5 cm/yr. The subduction zone data, numerical models and a scaling formulation for sinking of slabs in the upper mantle show that subducting plate velocity scales with ~Wexp(2/3), while trench velocity scales with ~1/W. Correlation coefficients for the numerical models with respect to the scaling formulation are in the range 0.95-0.99 for subducting plate velocity, trench velocity and subduction partitioning, while those for the natural data are in the range 0.70-0.72. It is thus found that slab width provides a first-order control plate velocity, trench velocity and subduction partitioning. Comparison of slab age and subduction kinematics for natural subduction zones gives significantly lower correlation coefficients (0.29-0.38), indicating that slab age provides a second-order control on trench velocity and subducting plate velocity. Our findings provide an explanation for the Cenozoic progressive decrease in subducting plate velocity and subduction partitioning of the Farallon plate, which we interpret as resulting from the progressive decrease in trench-parallel width of the Farallon slab during the Cenozoic from ~14000 km to only 1400 km at present. This decrease in slab width also explains the change from Sevier-Laramide orogenesis to Basin and Range extension in North America in the Eocene to Miocene. Shortening took place during wide-slab subduction and overriding-plate-driven trench retreat (push-back), whilst extension took place during intermediate to narrow-slab subduction and slab-driven trench retreat (pull-back).
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Papers by W. Schellart