The Iron Ore Resources of Karnataka

Karnataka is endowed with rich deposits of iron ores; with approximately 9.03 billion tonnes or about 41% of India’s estimated total haematitic and magnetitic iron ore resources (Table 1).Iron ore mining industry is on the fast track growth in recent years consequent on high demand for iron ore in the global market especially from China.

Basically there are four mineralogical types of iron ore resources in Karnataka: Haematite (Fe₂O₃), magnetite (Fe₃O₄), titaniferous magnetite (Fe₂O₃ with admixed TiO₂ and/or V₂O₅ impurities) and goethite and limonite (hydroxides of iron and aluminum).Based on the process of ore genesis four genetic types of iron ores can be distinguished.

1. Volcanosedimentary Ores: Banded Iron formations (BIF) are characterized by alternating bands of iron oxides (magnetite/ haematite) and silica (quartz /chert).These are formed by Volcanosedimentary processes. Iron oxides and silica liberated from submarine volcanic sources get precipitated in early Precambrian depositional basins in alternating fine layers due to specific seasonal and chemical variations in Eh- pH conditions. Precambrians of Karnataka, especially of Bababudan and Chitradurga Group of formations abound in BIFs. These have been metamorphosed and occur in magnetite form and contain 45 to 55 % Fe. The Kudremukh iron ores belong to this category.

2. Magmatic Ores: Titaniferous Magnetite bands associated with ultramafic intrusives are formed by magmatic processes. These ores limited in distribution, being confined to layered mafic-ultramafic intrusives. These ores are valued for the associated TiO₂ and V₂O₅ content, since Fe % content as well as the restricted ore abundance is not suitable (uneconomical) for iron ore mining under present day circumstances.

3. Supergene enriched iron ores: Weathering, alteration and enrichment of Precambrian BIFs under surface conditions during Tertiary and Quaternary periods have produced abundant haematite rich supergene iron ores especially in Sandur and Chitradurga schist belts. These ores are friable, powdery and easily extractable form and contain 62 to 68 % Fe. These are the most preferred iron ores at present in domestic as well as export markets.

4. Laterites: Laterites are iron and aluminum enriched products derived from the desilication of weathered rock material under humid tropical conditions. Coastal Karnataka and parts of Bidar and Kolar districts evince extensive laterite formations. However, the iron content in laterites range from 25 to 40% and hence is not suitable for iron extraction under present metallurgical technology.

Iron Ores of Karnataka

Haematitic iron ores: In the spindle shaped Sandur schist belt rich concentration of iron ores are confined to two prominent bands: the western Sandur belt and eastern Copper Mountain belt. The banded iron formations in these ranges have been weathered, altered and have undergone supergene enrichment of ores forming rich haematitic iron ore cappings analyzing 62 to 68% Fe content. Some red oxide bands are also found associated with these enriched ores. The supergene iron ores are associated with manganese ores of similar origin.

Iron Ores of Sandur region encompassing Sandur, Hospet and Bellary taluks of Bellary district can be grouped under eight ranges namely (a) NEB range [includes Bharatarayanaharavu, Gogga property, Ingligi, Jambunathanahalli and Sankalapuram] (b) Ramandurga or Ramgad range [includes Ramandurga, Ramgad and Vyasankere] (c)Timmappangudi range (d)Donimalai range (e) Ettinhatti range [includes Ubbalagandi, Rajapuram and Konanharavu] (f) Devadri range (g) Kumarswamy range [includes Subrayanahalli] and (h) Copper Mountain range [includes Halkundi, Belegal, Vibhutigudda and Haraginadona mines].Total iron ore reserves of Bellary-Sandur-Hospet sector has been conservatively estimated around 1000 million tones, but in reality it could be about 2000 million tonnes considering the deeper unexplored ores.

Table1. Estimated Haematite and Magnetite Iron ore resources of Karnataka (IBM, 2005)

Type of Iron Ore	Reserves in thousand tonnes (as on 1.4.2000)
	Proved	Probable		Total Reserves	Remaining Resources	Total Resources
	STD111	STD121	STD122
Haematite	394839	25865	107263	527967	620357	1148324
Magnetite	202125	-	18375	220500	7663347	7883847
Total	596964	25865	125638	748467	8283704	9032171

In the southern part of Chitradurga schist belt, Chitradurga and Tumkur districts, rich with supergene enriched haematitic iron ores occur. The Megalahalli sector in Chitradurga district and several ranges in Chiknayakanahalli sector like Sondekoppa, Karekurchi, Janehar, Kondli and others in Tumkur district are endowed with massive haematitic iron ores.

In Chikmagalur district some of the Banded Iron Formations have undergone supergene enrichment producing mine-able haematite type of ores. Smaller workable haematitic ore deposits also occur in Bagalkot, Belgaum, Dharwad, Shimoga and Uttara Kannada districts.

Magnetite iron ore: The Kudremukh and partly Bababudan iron ore belts represent massive magnetite type of ores, occurring in the form of banded magnetite quartzites. In banded magnetite quartzites, layers of iron oxides (magnetite) alternate with those of quartz. The Early Precambrian BIFs have been metamorphosed to greenschist to amphibolite facies and the ores occur mainly in the magnetite form. Most of the estimated 7.8 billion tonnes of magnetite ores reserves of Karnataka are in the Kudremukh and Bababudan ranges falling within the limits of Chikmagalur district. Magnetite type iron ores are harder compared to haematitic ores and are amenable for underground type of mining. However, in Kudremukh area, KIOCL designed a large open cast type of mine to extract the low grade magnetite ore.

Table 2.Districtwise Production of iron ores in Karnataka (in metric tonnes)

District/Year		2001-02	2002-03	2003-04	2004-05	2005-06
Bagalkot		60,140	31,045	331,378	882,334	1,150,350
Belgaum		100	0	0	500	450
Bellary		5,955,728	15,925,769	25,413,044	31,494,682	36,301,615
Chikmagalur		5,572,265	5,759,722	5,241,459	4,458,760	2922
Chitradurga		1,281,116	1,277,321	2188942	2,324,037	2,326,454
Dharwad		0	0	13,300	261,827	0
Shimoga		0	900	222,500	0	0
Tumkur		8668	205,222	1,114,005	1,687,638	1,625,481
Total		12,878,017	23,199,979	34,524,628	41,109,778	41,407,272