Geophysical Journal | 1999 volume 21 Ή3

Thermal instability near the level of the density inversion of melt and the solid phase: a model based on the Rayleigh-Tailor approximation

© Khazan Y.M.

A model is considered that treats asthenolenses observed at depths of 50-100 km beneath the Central Europe as a result of the thermal instability of a partially melted layer. This layer may be identified with the shear wave low velocity zone (SWLVZ) that is observed at depths of 250-450 km and correlates well with the asthenolenses territorially. The model takes into account that the upper boundary of the SWLVZ lies in the vicinity of a melt - solid density crossover. As a result, only a relatively thin upper part of the layer is unstable, and dimensions of partially melted bodies evolving from the layer and rising to the subcrustal depths turn out to be much smaller than the SWLVZ thickness. The possibility is justified to treat the instability problem as a Rayleigh-Taylor one with additional limitations on the instability increment accounting for the thermal relaxation.

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