Geophysical Journal | 2005 volume 27 1

The stress field in the northern part of the Ural

© Sim L.A., Yurchenko O.S., Sirotkina O.N.

We have reconstructed the stress field of different orders for the Polar, Subpolar and Northern Ural by a complex of methods. Regions with variations of strained conditions (RVSC) were identified within areas of intersection of faults which are specified by maximum dispersion of Lode-Nadai coefficient. Rock crystal nests are confined to these areas. Stress fields of the 2-nd order were reconstructed for blocks that have been subdivided by geologic criteria. Spatial orientation of quartz veins and schistosity plains strongly correlate with block's axes of the main normal stress. Cycles and phases of deformation were subranged using data base of direction of tectonic movement - we used friction planes (more than 10 000 sampling sites). Unified regional cycle has been established. It is the same for the pre-Riphean metamorphic complex of the axial part of the Ural, the Riphean - Lower Cambrian units, Paleozoic units of west Ural and ofiolites of east Ural. Inside the cycle 6 phases were subdivided, common for units of different ages. This evidences for post-orogenic age of the reconstructed stress field. Correspondence of Hercynian structures to the reconstructed stress field does not conflict with inherited evolution of Ural during post-Hercynian stage.

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