Kursk Magnetic Anomaly KMA

the largest iron ore basin in the USSR, in Kursk, Belgorod, and Orel oblasts of the RSFSR.

The magnetic anomaly was discovered in the late 18th century by P. B. Inokhodtsev during the preparation of the general land survey, and it was extensively studied by Professor E. E. Leist of Moscow University. The borders of the anomaly and the depth of the ore beds were investigated from 1896 to 1918, and on instructions from V. I. Lenin the work was resumed in 1919. In 1920 a special decree was promulgated calling for a comprehensive study of the KMA, and that year the Special Commission for the Study of the KMA, headed by I. M. Gubkin, was established. After the Great Patriotic War of 1941–45 work was resumed on a broader scale. Exploratory drilling based on data from magnetic, gravitational, and seismic research revealed enormous reserves of high-grade ores and easily concentrated magnetite quartzites.

The KMA lies in the Voronezh anticlise of the East European Platform. The lower structural stage is assigned to the Precambrian foundation of the platform, and the upper stage is made up of gently sloping sedimentary beds of the platform mantle.

The iron ores occur in the crystalline foundation at average depths of 60 m to 650 m. Two main types of ore—low-grade and high-grade—are well developed. Most of the low-grade ores, containing 32–38.8 percent iron, 0.0–0.32 percent sulfur, and 0.0–0.28 percent phosphorus, can be profitably concentrated. The high-grade ore contains 53.6–61.6 percent iron, 0.08–0.4 percent sulfur, and 0.02–0.03 percent phosphorus. The low-grade ores are represented by ferruginous quartzites of the Kursk series and range in thickness from a few meters to 700 m (in the southwestern part of the KMA); they are magnetite, magnetite-hematite, and hematite ores. Most of the high-grade ores are associated with the ancient weathering crust of the ferruginous quartzites and are products of their oxidation and natural concentration. They are chiefly martite, hematite, limonite, and siderite. The high-grade ores occur in two forms: horizontal mantle-like beds on the upper edges of the ferruginous quartzites and sharply dropping beds which sometimes extend to 500–700 m.

The main beds of ferruginous quartzites and the high-grade ores associated with them emerge on the ancient eroded surface of the Precambrian foundation in two runs—a northeastern and a southwestern band. The largest deposits of high-grade ore are found in the southwestern run. The KMA’s total commercial reserves of iron ore are estimated at 44.6 billion tons, including 26.1 billion tons of high-grade and 18.5 billion tons of ferruginous quartzites.

The KMA basin encompasses four iron ore regions: Belgorod, Staryi Oskol, Novyi Oskol, and Kursk-Orel. The Belgorod region has 90.5 percent of the KMA’s high-grade ore reserves in categories A + B + C₁ and 96.9 percent in categories A + B + C₁ + C₂. It includes the Iakovlevskoe, Gostishchevskoe, Bol’shetroitskoe, and other deposits unique in terms of reserves and quality of high-grade ores. The average iron content of the ores exceeds 60 percent, with negligible amounts of sulfur and phosphorus. The ore vein is located at depths that permit shaft mining only. The deposits are waterlogged (there are several water-bearing horizons) and thus must be drained before being mined. Shafts are sunk by the freezing method.

Industrial development of the KMA deposits began in 1952 with the opening of the experimental Gubkin Mine at the Korobkovskoe deposit. In 1959–60 mines went into operation at the Lebedinskoe and Mikhailovskoe deposits, and in 1969 a mine was opened at the Stoilenskoe deposit. These deposits have high-grade ores occurring at shallow depths and are less waterlogged. In 1972, 20.5 million tons of commercial iron ore was extracted in the KMA.

It is anticipated that the KMA will become the basis of a new industrial complex of national importance. The extraction of iron ore is expected to increase to many tens of millions of tons through expansion of open-pit mining and a sharp increase in the proportion of ferruginous quartzites in total extraction.

Industrial deposits of bauxite have been discovered in the weathering crust of Precambrian rock and in the younger sedimentary layers of the platform mantle within several iron ore deposits in the southwestern band. Moreover, significant reserves of cement raw material (Belgorod and other regions), phosphorites (near Shchigry), molding and construction clay, and sand have been identified in the deposits of the platform mantle.