Evaluating tectonic dislocations formation under the action of stresses at the Upper Kama potassium salt deposits

Abstract

Introduction. The studies of the tectonic structure, dynamic behavior and prediction of the areas of the most probable manifestation of hazardous dynamic events at the Upper Kama potassium salt deposits (VKMKS) revealed that active faults, nodal structures, fracture zones and individual fractures in the oversalt, salt and subsalt rocks exercise a decisive influence on the violation of the steady state of geological structure. The regional stress field and a large number of local factors caused by folding, basement tectonics (catagenetic and supergene leaching), exogenous (weathering and unloading) and endogenous (halokinesis) processes in the oversalt strata, the growth of dome structures, etc. cause tectonic dislocations in the VKMKS. Cracks and fissure zones have currently been incidentally mapped and quantitatively studied mainly in mine workings in the productive part of the deposit, to a lesser extent in the oversalt rock, and scarcely in subsalt deposits. A detailed high-precision gravity prospecting along with other geophysical methods is currently the only effective method for tectonic dislocations mapping in the rock mass of the VKMKS. Methods for the widespread and systematic mapping of tectonic dislocations both in plan and in section within the VKMKS have not been developed yet. However, the evaluation of kinematic tectonic dislocations development in bulk can be obtained to some extent by analyzing the qualitative and quantitative characteristics of the natural stress field. It is due to the fact that dislocations are formed only when the acting stress exceeds the limit of the corresponding longterm strength of rocks forming the object under study. Methods of research. Tectonic dislocations of various kinematic types are formed under the action of stresses. Kinematic dislocations depend on the relationships between the stress principal values. Therefore, to solve the problem of kinematic type in the Solikamsk depression (SD) and VKMKS, the data of natural stress field components measurement in Ural mine workings were analyzed, the regularities of its behavior in plan and depth were determined, which served as the basis for two mathematical models, regional and local. Research results. Mathematical modeling was carried out, giving a quantification of stress components behavior regularities with the depth for the tectonic and physical-geological conditions of SD and VKMKS. Conclusions. The data on the change in stress components, obtained from mathematical modeling for two models of the geological environment, made it possible to predict the regularities in formation of tectonic dislocations of various kinematic types at different depths in SD and VKMKS at the regional and detailed scale levels.