Krivoi Rog Iron Ore Basin

a major iron ore basin in the USSR and the main raw material source for ferrous metallurgy in the USSR.

General information. Located in Dnepropetrovsk Oblast, Ukrainian SSR, the basin stretches in a narrow belt (2–7 km wide) from north to south for about 100 km, chiefly along the Ingulets, Saksagan’, and Zheltaia rivers (Dnieper basin). Area, approximately 300 sq km.

Along with the ore-bearing regions of the adjacent oblasts (Zaporozh’e, Kirovograd, Poltava) it constitutes a large iron ore province, the Greater Krivoi Rog.

Geological survey. The Krivoi Rog Basin contains Precambrian sedimentary-metamorphic rocks of the Krivoi Rog series, which is divided into three suites. The middle suite is represented by an iron ore rock formation that is the main ore-bearing stratum. It has a thickness of as much as 2,000 m and contains 7–8 seams of ferruginous quartzites and schists that merge and taper in places. In other parts of the Krivoi Rog Basin the thickness of the iron ore formation is significantly less and it contains only 2–3 seams of ferruginous quartzites. The Krivoi Rog series was subjected to intensive folding and tectonic dislocations, with the formation of a complex folded zone consisting of compressed synclines and anticlines that have been tilted to the east and that are often cut by thrusts and faults. The ferruginous quartzites are represented by hematites, magnetites, and mixed hematitemagnetite varieties. In the upper levels (mainly to a depth of 100 m), an oxidized zone has developed with martitization of the quartzites. The average Fe content in the ferruginous quartzites is 30–45 percent and 25–30 percent in the magnetite varieties. The reserves of magnetite quartzites account for approximately 20 percent of the total quartzite reserves of the Krivoi Rog Basin.

Rich ores of the Krivoi Rog type are widely developed in the ore-bearing formation and on its contact with the schists of the upper suite. These ores form columnar, stock, lenticular, and pocket-like bodies that descend to a depth of 1,000 m and more, and in a number of places the bodies merge into single, thick, sloping ore beds upon reaching the trough bends. In terms of mineral composition the ores are divided into magnetite, martite, hematitemartite (the local name is sin ‘ka), martite-hematite- kraska (the local name is kraska), and hematite-kraska ores; more than 50 percent of the reserves are made up of martite and hematite-martite ores with an average content of Fe = 63.7 percent, P =0.026 percent, and S = 0.043 percent.

A number of researchers believe that rich ores of the sin ‘ka and kraska types were formed as a result of the leaching of quartz from ferruginous quartzites and the oxidation of residual minerals under conditions of ancient weathering. Other researchers think that the loss of the quartz from the ferruginous quartzites initially occurred under the effect of high-temperature metamorphizing solutions and that the rich magnetite ores that were formed in this manner were later subjected to oxidation under conditions of ancient weathering.

Economic and geographic survey. The development of mining works, the mining of the ore, and the commercial development of the Krivoi Rog Basin started in the second half of the 19th century, when the Krivoi Rog Iron Ore Joint-stock Company was founded. In 1881, 37,400 tons of ore were mined. Development on an industrial scale started in 1884 with the opening of the railroad connecting the Krivoi Rog Basin with the Donbas. In the prerevolutionary period the rich ore deposits were exploited rapaciously. A significant part of the enterprises belonged to foreign (mainly French) capital. In prerevolutionary times ore output reached its maximum in 1913 with 6.4 million tons (74 percent of all the iron ore mined in Russia).

During World War I (1914–18), the Civil War, and the foreign intervention of 1918–20, a majority of the mines was flooded and the equipment destroyed. Reconstruction of the basin started in 1921, and by 1931 the level of ore output surpassed that of the prerevolutionary period. During the prewar five-year plans existing mines were reconstructed and new mechanized mines were put into operation. Large metallurgical enterprises were built on the basis of the Krivoi Rog ores, including the S. Ordzhonikidze Zhdanov AzovstaF Plant, the S. Ordzhonikidze ZaporozhstaP Plant, and the V. I. Lenin Krivoi Rog Metallurgical Plant. In 1940 the ore output reached 18 million tons and steel production, 9.6 million tons, having surpassed the 1913 level by a factor of 3.3.

During the Great Patriotic War of 1941–45 the fascist German invaders greatly damaged the Krivoi Rog Basin. Reconstruction work started immediately after the liberation of the Krivoi Rog area on Feb. 22, 1944. By 1948 all the mines had been rebuilt and had begun operating on a new technical base. The Krivoi Rog Metallurgical Plant had also gone into operation. In 1950 the output of iron ore rose by 11 percent in comparison with 1940; in 1955 it rose by 95 percent; and in 1959, by 163 percent. Extensive mine construction was carried out, and effective mining systems and productive mining equipment were introduced. The problem of the dressing and industrial development of ferruginous quartzites was solved. In 1955, for the first time in the USSR, ferruginous quartzites (low-grade ores), which were processed into concentrates, were mined in the Krivoi Rog Basin. Between 1955 and 1965, five mining and dressing combines for ferruginous quartzites were built, including the Southern, New Krivoi Rog, Central, Northern, and Ingulets combines. In 1970, 103 million tons of iron ore were mined (more than 54 percent of the Union output), including more than 54 million tons of concentrates from low-grade ore.

In 1971 the Krivoi Rog Basin had 23 operating mines with a productivity of from 200,000 tons to 6.5 million tons of iron ore per year. Among the largest mines are Gigant-Glubokaia, V. I. Lenin, Saksagan*, Gvardeiskaia, Rodina, and Artem No. 2. Rich ores are mainly mined by the underground method to a depth of 900 m. The ore of the Krivoi Rog Basin is used not only for the needs of ferrous metallurgy in the south but is shipped to other Union republics and exported chiefly to European socialist countries. On the basis of iron ore mining in Krivoi Rog, a specialized industrial complex has formed, including, along with mining and the metallurgical industry, machine building, by-product coke industry, the food-processing industry, light industry, and the building materials industry.

Over the long run the expansion of iron ore mining will be carried out by increasing the productivity of the existing mining and dressing combines and by building new ones.