Subduction dynamics and overriding plate deformation

Below is an overview of the work I have done on subduction zone dynamics…


Effects of mantle viscosity on slab folding cyclicity and overriding plate stress regime

In the Andean subduction zone, the overriding plate (OP) has undergone episods of compression followed by periods of extensional/neutral stresses [1]. These variation in the tectonic regime of OP is likely to have been controlled by variations in slab dip through time [2]. In Cerpa et al. [2014] , we proposed that the possible stagnation of the slab at the mantle transition zone might be followed by slab folding episodes. Such phenomenon is likely to generate variations in slab dip and, thus, induce alternatively periods of compression and periods of extension.

slab_folding.gif
Experiment with a uniform mantle viscosity of 1e20 Pa.s. Top : Geometry of the plates and dynamic pressure in the upper mantle. Bottom : Geometry of the plates and the second invariant of deviatoric stresses in the upper mantle.
Geometry and second invariant stresses after 126.8 Myrs for models with different viscosities (modified after Cerpa et al. 2014 [1])
Geometry and second invariant stresses after 126.8 Ma for models with different viscosities (modified after Cerpa et al. 2014 [3]).

Relationship between topography and slab dip in an oblique subduction zone

The building of the Andes is partly due to periods of high compression in the South-American plate that induced shortening and thickening of the continental crust. However, the subsequent elevation in the presen-day orogen is not constant from North to South. For instance, in the Southern Andes we observe a general decrease in the maximum elevation from ~4 km at 33.5˚S to ~2 km at 43˚S. Those latitudinal differences in topography might have been controlled by latitudinal variations in slab dip. In Cerpa et al. [2015] , we showed that the stagnation of the slab at 660 km and slab folding in an oblique subduction is a mechanism that favors such segmentation.

Topography at the surface of the overriding plate and slab dip in an oblique subduction system where the subducting plate is anchored at 660 km of depth.
Topography at the surface of the overriding plate and slab dip in an oblique subduction system where the subducting plate is anchored at 660 km of depth (Cerpa et al. 2015 [4]).
obliqulargebis
Mantle flow around an oblique subduction zone through time. The plates are in gray. The lines represent the streamlines of upper mantle flow.

 
 




[1] Haschke, M., Günther, A., Melnick, D., Echtler, H., Reutter, K. J., Scheuber, E., & Oncken, O. (2006). Central and southern Andean tectonic evolution inferred from arc magmatism. In The Andes (pp. 337-353). Springer Berlin Heidelberg.
[2] Folguera, A., & Ramos, V. A. (2011). Repeated eastward shifts of arc magmatism in the Southern Andes: a revision to the long-term pattern of Andean uplift and magmatism. Journal of South American Earth Sciences, 32(4), 531-546.
[3] Cerpa, N. G., R. Hassani, M. Gerbault, and J.-H. Prévost (2014), A fictitious domain method for lithosphere-asthenosphere interaction: Application to periodic slab folding in the upper mantle, Geochem. Geophys. Geosyst. , 15, 1852–1877, doi:10.1002/2014GC005241.
[4] Cerpa, N. G., R. Araya, M. Gerbault, and R. Hassani (2015), Relationship between slab dip and topography segmentation in an oblique subduction zone: Insights from numerical modeling, Geophys. Res. Lett. , 42, doi:10.1002/2015GL064047.

 
 

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