Geophysical Journal | 2003 volume 25 4

Lithosphere of the Ukrainian Shield and the Pripiat' Basin region EUROBRIDGE-97 from gravity modeling data

© T.P. Yegorova, V.I. Starostenko, V.G. Kozlenko, Y. Uliniemi

At the initial stage of the accomplished study, a 3-D regional density model of the Earth's crust was set up for the region of the seismic profile EUROBRIDGE-97 cutting the Pripiat' Trough and the western part of the Ukrainian Shield. The area includes the major part of the Osnitsa - Mikashevichi Volcanic Belt with the superimposed Pripiat' Trough and three domains of the Ukrainian Shield: Volyn' domain with the Korosten' pluton, Podolian domain and Ros'-Tikich domain. The calculations of a 3-D model consisting of three layers: sediments and two layers in the crystalline crust show that the main features of the observed gravity field can be explained by density inhomogeneities to 15 km depth. Below it, the density distribution depends on the Moho topography. The gravity modeling along the EUROBRIDGE-97 profile confirms the existence of three main domains of different evolution in Precambrian. The velocity and density models of the profile were interpreted together with the prognostic composition of the crustal layers according to the estimations of the SiO2 content made using the VP/VS ratio. The modeling confirmed the status of the Podolian domain as the core of the Archean granulitic consolidation. The peculiarity of the Korosten' pluton structure, manifested in the complex lower crust and upper mantle structure, is well explained from the viewpoint of the conception of the formation of the rapakivi-anorthosive massifs as a result of the originating of partial melting chambers in the upper mantle - lower crust. An important role of the South Pripiat' fault repeatedly activized in Late Proterozoic and in Paleozoic times is substantiated. At the subplatform stage the South Pripiat' fault was probably a channel for Korosten' pluton magma. In Paleozoic the fault activized due to Late-Devonian rifting that formed the Pripiat' Basin.

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