Tectonic paleostress fields evolution and calcite veins formation in the southeastern part of the Ukrainian Carpathians during the cenozoic time
Journal Title: Геодинаміка - Year 2016, Vol 20, Issue 1
Abstract
Purpose. The main purpose of this paper is to study tectonic paleostress field evolution, its influence on the calcite veins formation and fluid flow in the southeastern part of the Ukrainian Carpathians during the Cenozoic time. The objects of our studies are joints parageneses, slickensides and veins in the Cretaceous sandstones located over the Chornohora, Dukla, Porkulets and Rakhiv nappes in the southeastern part of the Ukrainian Carpathians. Methods. To reconstruct the stress-strain state structural-paragenetic and kinematic methods were used. Fabric 8, StereoNett 2.46, and Tensor software was used to process the data and to determine the principal axes of paleostress field (σ1, σ2, σ3). Slickenside data were processed by using kinematic method with some modern modifications for the Carpathian region. Special attention was paid to the veins in the host rocks. Results. Within the study area we found 16 natural outcrops, 850 joints, 300 veins and 50 slickensides. Further, we described veins structural features and paleostress fields that could initiate joints formation. Not at all outcrops calcite veins were found. The statistically reliable number of carbonate veins was identified only at few study points. It is very important to study not only veins structural features but mineralogy, morphology, crystal microdefects, and fluid inclusions as well. Originality. For the first time we reconstructed tectonic paleostress fields evolution in the southeastern part of the Ukrainian Carpathians during the Cenozoic time by using data on joints and slickensides. The most active tectonic movements, deformation and carbonate veins formation are attributed to the strike-slip and tension paleostress fields. Strike-slip paleostress fields are defined as the youngest, and their tension axes are orientated in NE-SW and NW-SE directions. The number of calcite veins within the Dukla and Porkulets nappes is much more greater than that within the Chornohora and Rakhiv ones. Almost all veins strike in north-west direction. Ancient joints could be reactivated and filled with calcite simultaneously with subsequent tension regimes. Practical significance. Paleostress fields originated at the end of folding-faulting stage indicate that the strike-slip deformation regime changed due to tension in two directions (SE and SW tension axes). The detailed study of veins showed that their formation is the result of newly formed and reactivated joints and fractures filled by the matter due to the younger mechanical deformations. Calcite filled shear and tension joints formed as the result of different deformation regimes, starting from the folding-faulting stage. We conclude that intensive migration of fluids, including hydrocarbons fluids, took place at the end of folding-faulting stage of the Ukrainian Carpathian tectonic evolution.
Authors and Affiliations
S. Kril, I. Bubniak, Y. Vikhot
Keywords
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- EP ID EP194399
- DOI 10.23939/jgd2016.01.106
- Views 87
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