Models of convection and segregation in heterogeneous partially molten crustal roots with a VOF method – I: flow regimes

SUMMARY We investigate numerically some thermomechanical conditions for the development of crustal scale diapirism and convection in a heterogeneous continental crust independently from action regional tectonics. Here, we consider hot crust, with unmolten partially molten domains specific temperature strain-rate dependent power-law rheologies. take advantage volume fluid (VOF) method to capture coalescence separation deformable inclusions domain. The inclusions, several hundred metres size, are more or less dense viscous respect ambient medium (they also behave rheology). restrict our study 20 Myr time scale, during which gravitational dynamics may dominate over lateral tectonics lithospheric thermal re-equilibration. motion these instabilities displays distinct flow regimes that depend on two Rayleigh numbers denoted RaUM RaPM, rock properties, respectively. A ‘suspension’ regime occurs at high most light compositional heterogeneities remain entrained convective cells. In contrast low ‘layering’ is characterized by merging as floating clusters below rigid upper lid. This association sharp viscosity gradient upper-to-middle transitional depths. regimes, accumulate bottom zone. Finally moderate ‘diapiric’ reflects segregation heavy respectively downward upward, without global convection. These numerical experiments lead first order evaluation physical parameters required variable densities convection, provide insights migmatite domes. Geological data indicate processes likely occur large number settings Archean Phanerozoic times, contribute differentiation crust.