In
plate tectonics, slab detachment or slab break-off may occur during
continent-continent or
arc-continent collisions. When the
continental margin of the subducting plate reaches the
oceanic trench of the
subduction zone, the more buoyant
continental crust will in normal circumstances experience only a limited amount of subduction into the asthenosphere. The
slab pull forces will, however, still be present and this normally leads to the breaking off or detachment of the descending slab from the rest of the plate.[1] The
isostatic response to the detachment of the downgoing slab is rapid uplift. Slab detachment is also followed by the upwelling of relatively hot
asthenosphere to fill the gap created, leading in many cases to
magmatism.[2]
The uncritical use of the slab-detachment model to explain disparate observations of magmatism, uplift and exhumation in continental collision zones has been criticised.[3][4]
Slab tears
Detachment initiates at a particular point on the slab and will then propagate laterally along the descending slab, forming a slab tear. The propagation of the detachment will be accompanied by lateral migration of both the associated uplift and the magmatism.[5] Such laterally propagating tears have been recognised from several collision zones, such as the
Hindu Kush part of the Himalayan Belt.[6] The Tertiary magmatism in the
Alps observed along the
Insubric Line has been argued to result from a rapidly propagating slab tear following continental collision and the initiation of slab breakoff.[7]
References
^van Hunen, Jeroen; Allen, Mark B. (February 2011). "Continental collision and slab break-off: A comparison of 3-D numerical models with observations". Earth and Planetary Science Letters. 302 (1–2): 27–37.
Bibcode:
2011E&PSL.302...27V.
doi:
10.1016/j.epsl.2010.11.035.
^Huw Davies, J.; von Blanckenburg, Friedhelm (1 January 1995). "Slab breakoff: A model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens". Earth and Planetary Science Letters. 129 (1): 85–102.
Bibcode:
1995E&PSL.129...85D.
doi:
10.1016/0012-821X(94)00237-S.
^Garzanti, Eduardo; Radeff, Giuditta; Malusà, Marco G. (February 2018). "Slab breakoff: A critical appraisal of a geological theory as applied in space and time". Earth-Science Reviews. 177: 303–319.
Bibcode:
2018ESRv..177..303G.
doi:
10.1016/j.earscirev.2017.11.012.
Ferrari, Luca (2004). "Slab detachment control on mafic volcanic pulse and mantle heterogeneity in central Mexico". Geology. 32 (1): 77.
Bibcode:
2004Geo....32...77F.
doi:
10.1130/G19887.1.