Exhumation of (U) HP/LT rocks caused by diachronous slab breakoff

• Published in: Journal of structural geology 2018-12, Vol.117, p.251-255
• Main Authors: Boutelier, D., Cruden, A.R.
• Format: Article
• Language: English
• Subjects: Analogue models; Exhumation; Slab breakoff; Subduction
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2018.06.012

Three-dimensional thermo-mechanical analogue models investigate how diachronous slab breakoff may lead to the exhumation of subducted continental crust. Slab breakoff initiates spontaneously in one location and migrates laterally along the plate boundary, causing a transient excess downward pull force on the plate boundary in front of the propagating slab tear. This pull force locally reduces the pressure between the plates, which promotes buoyancy-driven exhumation of subducted crust. However, both the surface area undergoing the pressure reduction and its duration are limited. Our experiments show that the rate of slab breakoff propagation controls both the duration of the pull force and the magnitude of pressure reduction. Our results further demonstrate that exhumation occurs where the slab breakoff propagation rate is lowest, rather than where the pull force is strongest, corresponding to where the slab tear initiates or terminates. •Slab breakoff produces a local transient excess downward pull force on the plate boundary.•Excess downward pull travels along the plate boundary with the slab detachment.•Pressure reduction allows deformation of crust in between the plate.•Exhumation occurs where propagation is slow.