GRAVITY-ANOMALIES AND POSSIBLE FORMATION MECHANISM OF THE DNIEPER-DONETS BASIN

Two-dimensional gravity models are presented along several seismic lin es intersecting the Dnieper-Donets Basin. These models are based on ve locity sections and the experimental data on the relationship between density and P-wave velocity. The detailed gravity modelling of gradien t-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-Done ts Basin evolution since the Middle Devonian. The mechanism includes a ccumulation of magmatic melt in the asthenospheric bulge during post-r ifting, phase transition to eclogite in the uppermost mantle, and a fl ow induced by the evolved heavy bodies. We construct a 2-D numerical m odel of the flow beneath the Dnieper-Donets Basin, compute this flow a nd the resulting changes in the surface topography. The subsidence cur ve calculated in the suggested model gives the best fit to the observe d tectonic subsidence than curves of thermal subsidence predicted by t he stretching model. Numerical results confirm the observed gravity hi gh over the Dnieper-Donets Basin.