Magnetic susceptibility experimental study of the rocks from north-western part of Dnieper-Donets depression

Complete text of publication follows. Magnetic susceptibility χ of the sedimentary and effusive Devonian and Carbonian rocks from 8 bore-holes of north-western part of Dnieper-Donets depression was investigated. There are argillits, aleurolites, sandstones, limestones, anhydrites, salt, tuff breccias, tuff sandstones, marls, dolomitic limestones, basalts. The crystalline basement (Precambrian) is presented by gneisses and granite-gneisses from Stroyivska bore-hole (2976-3803m). Oil and gas perspectives are connected with Devonian deposits. Magnetic susceptibility values of the rocks vary in wide interval: from 5,4 x 10-5 Si (Zorkivska) to 921 x 10-5 Si (Borkivska) for argillites; from 7 x 10-5 Si (Nizhynska) to 11450 x 10-5 Si (Borkivska) for aleurolites; from 3,9 x 10-5 Si to 207 x 10-5 Si for limestones; about 0 (Zorkivska) for anhydrite; from 1,7 x 10-5 Si (Guzhivska) to 11666 x 10-5 Si (Borkivska) for sandstones. Tuff breccias are characterized by χ of only 13 x 10-5 Si and 80 x 10-5 Si. Magnetic susceptibility of basalt is high enough - 11110 x 10-5 Si. Low values of magnetic susceptibility characterize gneisses (from 17 x 10-5 Si to 51 x 10-5 Si) and granite-gneiss (about 41 x 10-5 Si). The temperature influence on magnetic susceptibility of the rocks was researched. We made a pair from each sample for laboratory experiments. One of them was saturated by gasoline during 1 month the other remained dry. Samples magnetic susceptibility in dependence on temperature with the purpose of accelerating any processes taking place in them was measured. Step of heating was 50 deg C (from 100 deg C to 350 deg C). Magnetic susceptibility was measured on the astatic magnetometer and on the magnetic susceptibility bridge. As a result graphs of absolute values of magnetic susceptibility in dependence on the temperature were received. After experiment we can confirm that only in a small number of gasoline-saturated samples magnetic susceptibility increase (argillites, aleurolites, tuff breccia, sandstone). Some samples displayed no changes of χ or changes are similar in dry and in gasoline-saturated samples. In some occasions we can see reduction of magnetic susceptibility values of gasoline-saturated samples. It seems that the cause of such conduction of magnetic susceptibility may depend on the initial composition of the rocks and Fe-contained minerals. It needs the supplementary magnetic-mineralogical investigations to solve this problem.