Geophysical Journal | 2009 volume 31 3

Effect of stress-deformed state of medium on formation of weakened zones in the Archean basement of the northeastern part of the Baltic Shield

© Filatova V.T.

This work based on numerical modeling allowed us to distinguish the dependence of the formation of permeable zones in the crust on the natural stresses in the region. The results are presented for the first time (including quantitative estimates and relations between geological factors). They demonstrate the capabilities of the formation of deformation structures in the region and reflect the peculiarities of the tectonic evolution in the region, among which the main one is inherited properties of geodynamic activity in the region from the Early Precambrian. In these studies, the northeastern part of the Baltic Shield is considered a nonuniform elastic body subjected to the influence of three-dimensional forces and stresses specified at the boundary. We solve the boundary problem of stresses using programming codes specially developed for these objectives. The obtained estimates of paleostresses σxx, σyy, σxy and direction of the main stress axes allow us to explain the mechanism of formation of weakened zones in the basement during the Late Archaean, which are linear, and source zones of increased permeability that predetermined the localization of tectonic magmatic processes in the region. It follows from the results that during geological history the contours of the contact boundaries between megablocks did not change essentially and the predisposition to localization of linear and source zones of increased permeability of the Earth's crust in the northeastern part of the Baltic Shield controlling the location of magmatic province was formed already in the Late Archaean.

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