Joao Duarte | Monash University (original) (raw)
Papers by Joao Duarte
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.
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.
Marine Geology, Oct 8, 2011
In the Gulf of Cadiz key segment of the Africa–Iberia plate boundary (North-East Atlantic ocean),... more In the Gulf of Cadiz key segment of the Africa–Iberia plate boundary (North-East Atlantic ocean), three main different modes of tectonic interference between a recently identified wrench system (SWIM) and the Gulf of Cadiz Accretionary Wedge (GCAW) were tested through analog sand-box modeling: a) An active accretionary wedge on top of a pre-existent inactive basement fault; b) An active strike-slip fault cutting a previously formed, inactive, accretionary wedge; and c) Simultaneous activity of both the accretionary wedge and the ...
Geophysical Research Letters, 2015
Several lines of evidence suggest that subduction zones are weak and that the unique availability... more Several lines of evidence suggest that subduction zones are weak and that the unique availability of water on Earth is a critical factor in the weakening process. We have evaluated the strength of subduction zone interfaces using two approaches: (i) from empirical relationships between shear stress at the interface and subduction velocity, deduced from laboratory experiments; and (ii) from a parametric study of natural subduction zones that provides new insights on subduction zone interface strength. Our results suggest that subduction is only mechanically feasible when shear stresses along the plate interface are relatively low (less than~35 MPa). To account for this requirement, we propose that there is a feedback mechanism between subduction velocity, water released from the subducting plate, and weakening of the fore-arc mantle that may explain how relatively low shear stresses are maintained at subduction interfaces globally.
The 2005 SISMOMAR expedition explored the crustal structure of the Lucky Strike segment of the Mi... more The 2005 SISMOMAR expedition explored the crustal structure of the Lucky Strike segment of the Mid-Atlantic ridge (MAR) and the three-dimensional structure of its central volcano. This segment is one of the focus points of the InterRIDGE MoMAR (Monitoring of the Mid-Atlantic Ridge) program and has been proposed as a RIDGE2000 collaboration site. The Lucky Strike volcano, situated near the
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.
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.
Marine Geology, Oct 8, 2011
In the Gulf of Cadiz key segment of the Africa–Iberia plate boundary (North-East Atlantic ocean),... more In the Gulf of Cadiz key segment of the Africa–Iberia plate boundary (North-East Atlantic ocean), three main different modes of tectonic interference between a recently identified wrench system (SWIM) and the Gulf of Cadiz Accretionary Wedge (GCAW) were tested through analog sand-box modeling: a) An active accretionary wedge on top of a pre-existent inactive basement fault; b) An active strike-slip fault cutting a previously formed, inactive, accretionary wedge; and c) Simultaneous activity of both the accretionary wedge and the ...
Geophysical Research Letters, 2015
Several lines of evidence suggest that subduction zones are weak and that the unique availability... more Several lines of evidence suggest that subduction zones are weak and that the unique availability of water on Earth is a critical factor in the weakening process. We have evaluated the strength of subduction zone interfaces using two approaches: (i) from empirical relationships between shear stress at the interface and subduction velocity, deduced from laboratory experiments; and (ii) from a parametric study of natural subduction zones that provides new insights on subduction zone interface strength. Our results suggest that subduction is only mechanically feasible when shear stresses along the plate interface are relatively low (less than~35 MPa). To account for this requirement, we propose that there is a feedback mechanism between subduction velocity, water released from the subducting plate, and weakening of the fore-arc mantle that may explain how relatively low shear stresses are maintained at subduction interfaces globally.
The 2005 SISMOMAR expedition explored the crustal structure of the Lucky Strike segment of the Mi... more The 2005 SISMOMAR expedition explored the crustal structure of the Lucky Strike segment of the Mid-Atlantic ridge (MAR) and the three-dimensional structure of its central volcano. This segment is one of the focus points of the InterRIDGE MoMAR (Monitoring of the Mid-Atlantic Ridge) program and has been proposed as a RIDGE2000 collaboration site. The Lucky Strike volcano, situated near the