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Subduction zone evolution and interaction with an intracratonic suture

St4d is showed in the video
 
 St4d 


This models shows a subduction setting with an inclined weak post-collisional suture zone positioned ~400 km to the right of the trench in the overriding plate.  The suture zone is inclined away from the subduction zone at 45°.  The lithosphere to the right of the trench has continental crust; that the to left has oceanic crust.  Subduction initiation in the model is facilitated via a narrow shear zone at the trench. The far field stresses correspond to 4cm/yr pushed from the left.  During the onset of the model, the shear zone initiates subduction of the oceanic crust under the continental to the right.  Conventional subduction-related processes occur within the subduction area including slab rollback, devolitization and release of fluids from the slab.  This results in the upward migration and propagation of the cold plumes along the base of the overriding lithosphere. Delamination of the mantle lithosphere at the base of the inclined suture zone commences after ~3Ma, accompanied by localised horizontal extension within the suture zone.  Delamination of the mantle lithosphere is complete after ~14Ma.  Local bulk extension in the suture leads to decompression melting and the opening of a new ocean floor, with extensive melt production. Simultaneously, strong melting of the mantle wedge and slab products occurs in the subduction zone, which are enhanced by subduction of an oceanic plateau arriving at the trench after ~18My.



Subduction Weak_zone1

This models show the evolution of a similar subduction scenario to that in model st4d; here with a weak suture zone ~400km to the right within the overriding plate that is inclined towards the subduction zone.  During the onset of the model, the shear zone initiates subduction of the oceanic crust under the continental to the right.  Conventional subduction-related processes occur within the subduction area including slab rollback, devolitization and release of fluids from the slab.  This results in the upward migration and propagation of the cold plumes along the base of the overriding lithosphere.  Delamination of the base of the mantle lithosphere in the inclined suture zone commences after a similar timeframe to that in st4d, but completes far more rapidly after ~6Ma.  As the melts released from the downgoing slab underplate the mantle lithosphere, they cause further delamination of the base of the overriding lithosphere.  The melts migrate along the lithosphere base towards the weak zone and concentrate there, forming a potentially very interesting magma source ~400 km away from subduction zone.  Similar to st4d, an oceanic plateau interacts with the trench after ~18Ma, enhancing melt generation in the subduction zone area.