Gravity anomalies and possible formation mechanism of the Dnieper-Donets Basin

Two-dimensional gravity models are presented along several seismic lines intersecting the Dnieper-Donets Basin. These models are based on velocity sections and the experimental data on the relationship between density and P-wave velocity. The detailed gravity modelling of gradient-layered crustal and upper mantle features clearly reveals increased density in the upper mantle explainable by rock eclogitization. Using the gravity models we propose a possible mechanism of the Dnieper-Donets Basin evolution since the Middle Devonian. The mechanism includes accumulation of magmatic melt in the asthenospheric bulge during post-rifting, phase transition to eclogite in the uppermost mantle, and a flow induced by the evolved heavy bodies. We construct a 2-D numerical model of the flow beneath the Dnieper-Donets Basin, compute this flow and the resulting changes in the surface topography. The subsidence curve calculated in the suggested model gives the best fit to the observed tectonic subsidence than curves of thermal subsidence predicted by the stretching model. Numerical results confirm the observed gravity high over the Dnieper-Donets Basin.