Pripyat trough as a possible channel of mantle degassing: deep structure and position in the junction zone of Sarmatia and Fennoscandia

Abstract

The Pripyat Trough, representing the northwestern end of the Pripyat-Dnieper-Donetsk Basin, is located in the junction zone of the Precambrian terrains of Fennoscandia and Sarmatia, controlled by the Osnitsk-Mikashevichy Igneous Belt. The ancient tectonic suture was reactivated during subsequent episodes of Meso-Neoproterozoic and Devonian rifting. The lithosphere structure of the Pripyat Trough is generalized according to published geophysical data and new interpretation of the velocity-density model of the lithosphere structure on Eurobridge-97 profile is given. The structure of the lithosphere at the southern flank of the Pripyat Trough and the Korosten pluton, consisting of rapakivi granites — gabbro-anorthosites, is associated with the existence of a mantle magma chamber, inflow of mantle melts into the crust, partial melting, magmatic differentiation and transformation of the substance throughout the crust under the pluton. Within the Pripyat Trough, a special role belongs to the South Pripyat fault, which limits the Pripyat Trough from the south, and the Korosten pluton from the north, and is associated with an inclined seismic boundary (reflector) in the mantle. The South Pripyat fault, being a deep fault zone, controlled the intrusion of magmatic melts and mantle fluids throughout its evolution. At present it controls seismicity and, obviously, is a conduit for hydrocarbons and a mantle degassing channel. Significant features of the structure and evolution of Pripyat Trough are: (I) origination in an ancient zone of weakness that undergone repeated tectonic and magmatic activations, (II) position at the intersection of four major zones of heterogeneity: Osnitsk-Mikashevichy Igneous Belt of NE strike, N-S-trending Odessa—Gomel zone, W-E-oriented Brest—Pripyat, and the Dnieper—Donets Basin of the NW orientation, (III) the spatial relationship of the limiting listric faults with mantle heterogeneities; (IV) recent activation and confinement of hydrocarbon deposits to it. These criteria make it possible to consider the Pripyat Trough as a possible channel of mantle degassing.