Abnormal magnetic field. Regional magnetic anomalies

During the last years the abnormal magnetic field has been successfully used for the construction of non-uniformly scaled solid models, the geological environment, which is also an integral part of the estimation of perspectivity of geological structures on different minerals.

The magnetic or geomagnetic field, is a force field caused by electromagnetic processes in a kernel of the Earth (main, or a normal field), in the top layers of the ionosphere (a variation of a geomagnetic field) and magnetisation of earth crust materials. The former factor forms an abnormal magnetic field which displays presence of materials with different concentration of magnetic minerals in earth crust. The most abnormal magnetic field on the territory of Ukraine is represented on NAU map "the Abnormal magnetic field". It is received by an exception of the variations connected with ionospheric processes, and, a so-called, normal field from intensity of the general geomagnetic field. The normal field has no exact analytical image and consequently has several approximating models, one of which is represented on NAU map "the Normal magnetic field".

The abnormal magnetic field, which is found on the territory of Ukraine is differentiated greatly and consists of the regional and local components, which differ in the lateral dimensions of anomalies and the depth of their sources. Regional field component, represented on the map "Regional magnetic anomalies" is conditioned by the heterogeneity of structure of the lower part of earth crust and a relief of the magnetoactive layer bottom, which can be identified with an earth crust bottom (Мохоровічич section) or with an isothermal surface of Curie temperature magnetite as the main carrier of materials' magnetism. It displays regional features of the big geostructures, and particularly of separate blocks of the Ukrainian sheet and the imposed trenches of a platform part of territory, border of the East European platform and heterogeneity of earth crust within Mountainous Crimea and Carpathians. Local component of an abnormal magnetic field is influence of magnetised materials of the top part of the crust and displays its composition and a structure. Use of local magnetic anomalies in the search purposes has begun in Ukraine more than 100 years ago with opening and the further research of Krivorozhsky iron-ore deposit. Now this component of a magnetic field is used as one of the reliable information sources during geological mapping of materials, studying of fold and explosive tectonics, tectonic zoning, and together with the regional component and other geophysical data - for studying of correlations between near-surface and deep lithospheric structures. The former is an important factor in the development of searching criteria for the different types of minerals, including oil-and-gas. From this point of view special value acquires tracing according to abnormal magnetic field data of the so-called through faults and a trance of regional tectonic zones, which are often enough zones of activization and concentration of minerals.

During the last years the abnormal magnetic field has been successfully used for the construction of non-uniformly scaled solid models, the geological environment, which is also an integral part of the estimation of perspectivity of geological structures on different minerals.