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| Our work on South East Asia Tectonics
constrain the magnitude and timing of some of the strike-slip
deformations related to the India/Eurasia collision. We have
confirmed that in Indochina such deformations are very important
with respect to internal deformations within the blocks. We have
constrained the sense, timing, amount and rate of the largest
strike-slip shear zone: the ASRR. Indochina deformations follow
the northward progression of the Indian indenter with creation
of left-lateral faults at its front and reactivation of these
faults in the opposite sense behind him. This conclusions have
implications on the continental lithosphere mechanics. (1) In the middle crust, ductile strike-slip deformations are localised in narrow shear zones that can absorb large movements of more than some hundreds km (at least 500 and probably more than 700 km for the ASRR). (2) Such shear zone last for several Ma (at least 16 Ma for the ASRR) and are not transient structures. (3) One of these structures may absorb a significant part of the continental deformation by extruding laterally large continental blocks. (4) Such shear zone probably affects the whole lithosphere and create a new oceanic basin. (5) At the scale of the collision zone such deformation follow a simple logic where deformation are discontinuous in space and time. (6) The model that best explains SE Asia deformations is the two stages extrusion model proposed by Tapponnier et al. (1986) on the basis of deformation of a strain softening medium (plasticine). Such experiment are however over-simplified and probably give a picture of the mantle-lithosphere deformation. |
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