Krivoy Rog, Krivoi Rog - Ingulets, Saksagan, Pervomaisk, Annovsk, Zheltorechensk and Popelnostovsk


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The Krivoi Rog Iron ore deposits, within the Krivoi Rog Iron Basin (Krivbass), is located approximately 330 km southeast of Kiev and 150 km north of the Black Sea in the Ukraine.

It lies within the valley of the Ingulets River and its tributaries, the Saksagan and the Zheltaya, and extends in a NNE direction over an interval of about 100 km. The basin is developed within the crystalline basement of the Kurainian massif, comprising Archaean gneisses, granites, migmatites, amphibolites and schists exposed to the west and east of the 2200-2000 Ma Palaeoproterozoic Krivbass geosyncline. The Proterazoic Krivoi Rog Series within the Krivbass is divided into three sections:
i). a lower arkose-quartzite and phyllitic sequence, with a horizon of talc schists,
ii). a middle, ore-bearing ferruginous quartzite (banded iron formation - BIF) and slate sequence, which includes includes nine BIF horizons intercalated with quartz-sericite, chlorite-sericite, slates and microquartzites; and
iii). an upper, quartzite-sandstone-slate sequence with lenses of marble.

The Krivoi Rog Series is folded itno a complex synclinorial structure of synclinal and anticlinal folds with dips on the limbs of 45 to 80°, for the most part with a keel shaped synclinal closure plunging at up to 40° northwards. The limbs of the major synform has been intruded by Proterozoic granite and are cut by longitudinal faults or overthrusts, resulting in the ore-bearing units being segregated along the north-south strike of the basin to form the: i).  southern-most Ingulets, ii). the Saksagan or Main, iii). the Pervomaisk, iv). Annovsk, and the northern v). Zheltorechensk and Popel'nostovsk ore fields. The largest reserves of high grade ores are concentrated in the Saksagan ore field where the ore-bearing middle unit attains a thickness of up to 2000 m and contains up to eight BIF seams.

The BIFs (ferruginous quartzites) comprise magnetite, magnetite-hematite, and hematite varieties, the most economically significant being the unoxidized magnetite and magnetite-hematite varieties. The high grade ores consist mainly of iron oxides and hydroxides which form column-like, less commonly stock-, and lens-like, and more rarely layer-like segregations and bodies within the BIF units, the characteristics of which vary from location to location within the basin. This high grade ore was formed by the leaching of quartz and oxidation of iron silicates within the BIFs.

The high grade segregations are commonly localised on the limbs of the major folds where those limbs are deformed by tranverse cross-folds and 'crumpling', accompanied by the development of cleavage and interstratal movements, strike-slip faulting, fracture intersections and in zones of fracturing, crushing and jointing. They form chains with larger or smaller accumulations, with the individual ore bodies apparently merging at depth in the keel of the syncline to form large ore columns coinciding with the fold keels.

The richest concentrations of ore in the main Saksagan ore field are associated with the fifth and sixth BIF units, which contain higher grade primary mineralisation, and have thinner bedding which contributed to the development of the deformation.   The ore segregations are located totally within the BIF units, on the limbs and within the keels of the synclines.   In the Southern ore fields, concordant planar ore layers are localised in the unconformable contact between the middle and upper sections of the Krivoi Rog Series.   In the Northern ore fields, the ores have been hydrothermally-metasomatically altered.

Four principal types of enriched ores have been recognised in the Krivbass group, as follows:

i). Martite and hematite-martite - in addition to martite and relict hematite, relict magnetite, dispersed hematite, chlorite, sericite, pyrite, carbonates, clay minerals, quartz, and apatite have been observed in small amounts. The average content of this ore style is recorded at 63.7% Fe, 0.26% P, 0.043% S;
ii). Martite-hematite-hydrohematite-hydrogoethite - in addition to the assemblages listed above, there are also dispersed hematite, martite, sericite, quartz, clay minerals, alunite and sphene in small and accessory amounts. The average content of this ore style is recorded as 62.3% Fe, 0.08% P, 0.03% S;
iii). Hematite-hydrohematite-hydrogoethite - in addition to the main ore minerals, there is kaolinite, clay minerals, chlorite and carbonates. The average content of this ore style is recorded as 57.5% Fe, 0.088% P, very low S;
iv). Magnetite and magnetite-specularite - in addition to the dominant magnetite and specularite, amphiboles (curnmingtonite, grunerite, and riebeckite), aegirine, biotite, albite, quartz, carbonates, chlorite, grains of pyrite, pyrrhotite and chalcopyrite, have been recorded. The average content of this ore style is recorded as 54.0% Fe, 0.04% P, 0.15% S.

The original resource of high-grade iron ore within the Krivbass totalled 19.6 Gt (including 4 Gt @ 57.6% Fe), and 18 Gt of unenriched BIF averaging 35.9% Fe (Smirnov 1977).

Most of the higher grade ore had been exhausted by1990 when the annual production was 186 Mt @ 35.2% Fe.

The most recent source geological information used to prepare this summary was dated: 1993.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Alexandrov E A,  1973 - The Precambrian banded iron formations of the Soviet Union: in    Econ. Geol.   v68 pp 1035-1062
Findlay D,  1994 - Diagenetic boudinage, an analogue model for the control on hematite enrichment iron ores of the Hamersley Iron Province of Western Australia, and a comparison with Krivoi Rog of Ukraine, and Nimba Range, Liberia: in    Ore Geology Reviews   v9 pp 311-324

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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