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Lithosphere destabilization by melt weakening and crust-mantle interactions : Implications for generation of granite-migmatite belts

Kaislaniemi, L. ; van Hunen, J. ; Bouilhol, P., Tectonics

Lithosphere destabilization by melt weakening and crust-mantle interactions : Implications for generation of granite-migmatite belts

Kaislaniemi, L. ; van Hunen, J. ; Bouilhol, P.

Tectonics, 2018, 37

Abstract :

Orogenic crustal anatexis is a still poorly understood process due to the complexity of the thermal and geodynamical interaction between mantle and crustal processes during and after continental collision. Here we present a novel conceptual model for the formation of granite-migmatite belts : we propose that convective thinning of the lithosphere results in minor amounts of partial melts within the lowermost crust that trigger further instabilities. This will lead to positive feedback effects between melt weakening, mantle upwelling, and wholesale mantle lithosphere removal, causing a strong pulse of mantle and crustal melting. We test this model numerically, and results show that this process, taking between 20 and 50 Myr in total, can explain the temporal evolution of melting in granite-migmatite zones and associated mantle-derived mafic rocks and provides a heat source for crustal melting without the need for other processes, such as slab break-off or increased radiogenic heating. Furthermore, the generation of a refractory residue after mantle and crustal melting is also shown to control the progress of the lithospheric mantle removal, providing another feedback mechanism between melting and lithospheric reequilibration.

Voir en ligne : https://doi.org/10.1029/2018TC005014




publié lundi 24 septembre 2018