Appendix 2 Description of the major coalfields of India
Space precludes a detailed field-by-field description of each coalfield, for which the reader is referred to the Coal Atlas of India (1993). However a summary of each of the major coalfields, abstracted from the Coal Atlas of India, is given below and their locations are shown in Figure A2.1.
THE RANIGANJ COALFIELD
This is the easternmost field in the Damodar valley (Figure A2.1). It lies mainly in West Bengal but also partly in Bihar. It is a synclinal basin, the southern boundary of which is marked by major faults. There are ten major seams in the Raniganj Formation, designated RI to RX. Their thicknesses range from 1 m to 11 m and the seams tend to thicken towards the east. There are seven major seams in the Barakar Formation, designated seams BI to BVII. These range in thickness from 1 m to 24 m, the lower seams generally being thicker. The Barakar seams are high in ash.
The coals seams generally dip to the south at angles between 3° and 11°. In places they are affected by igneous sills and dykes, which are more prominent in the Barakar seams, and by faults. About 22 billion tonnes of coal reserves were present in the field in 1993, and there were 109 collieries in operation, producing about 26 million tonnes of coal per annum (Coal Atlas of India, 1993).
THE JHARIA COALFIELD
This coalfield covers an area of 450 km2 in the state of Bihar (Figure A2.1). The coalfield is a half-graben bounded to the SSW by a major fault. The coal-bearing formations dip SSW generally at 10°-15° but close to the bounding fault at up to 70°.
The Barakar Formation contains 18 coal seams (numbered I to XVIII) and the Raniganj Formation contains 12. Additionally there are a number of thin and impersistent seams. Barakar seams XIII and above are thin but of superior quality. The coal seams are affected in places by igneous dykes and sills and to varying degrees by faults.
This coalfield is the only source of prime coking coal in the country. In 1993, total reserves of coal were 19.4 billion tonnes, of which 5.3 billion tonnes were prime coking coal (Coal Atlas of India, 1993).
THE EAST BOKARO COALFIELD
This is located in the Damodar Valley in East Bihar (Figure A2.1). It is separated from the West Bokaro coalfield by Lugu Hill. It covers an area of 237 km2. It is a major source of medium coking coal. It is a westwards-plunging syncline that is structurally disturbed by numerous faults that break it up into a number of smaller blocks with different geological characteristics and mining issues. The coal seams have been affected by igneous intrusives (dykes and sills) in places, particularly in the western part of the field.
There are three coal-bearing Formations; the Karharbari (4 seams), the Barakar (21 seams) and the Raniganj (8 seams). Coal rank increases with depth and also towards the east. The Kargali Seam is 20-50 m thick, contains only a few dirt bands and has superior coking coal properties. In 1993, total coal reserves were estimated to be 5.6 billion tonnes. There were 13 opencast and 10 underground mines operating in 1993, producing nearly 12 million tonnes of coal (Coal Atlas of India, 1993). The coalfield is an important source of medium coking coals. The Bokaro and Chandrapura power stations are nearby.
THE WEST BOKARO COALFIELD
This covers an area of 207 km2 in the state of Bihar (Figure A2.1). It is narrowly separated from the East Bokaro Coalfield and the North Karanpura Coalfield, the latter lying immediately to the west, separated by a narrow belt of metamorphic basement rocks.
Structurally, the western part of the coalfield consists of two E-W trending synclines separated by a central antiform. These three features converge into a single syncline towards the eastern end of the coalfield. The coalfield is cut by numerous faults and coal seams have been affected by igneous dykes and sills in places, particularly in the Tapin and Parej blocks.
The main coal-bearing formations are the Karharbari and Barakhar formations. There are 13 major seams in the Barakar (29 seams in all) and one seam in the Karharbari. Total coal reserves were 4.6 billion tonnes in 1993, when there were 19 mines producing 3.5 million tonnes of coal per annum. Most of the coal production is opencast (Coal Atlas of India, 1993).
THE RAMGARH COALFIELD
This coalfield covers an area of 98 km2 in the state of Bihar (Figure A2.1). The coal-bearing formation is the Barakar Formation.
Structurally, the coalfield is a half graben with major en-echelon bounding faults on its south side. It consists of two E-W-aligned sub-basins known as the main basin and the sub-basin. Dip usually varies from 10° to 12° in the Main basin and 10° to 20° in the Sub-basin. The coals are only slightly affected by dykes and sills in a few places.
The Barakar Formation contains 13 coal seams in the main basin and 11 coal seams in the sub-basin. Seams VIIIA, VIITop and VIIBottom are the most important seams and have moderate ash contents. A total of 970 million tonnes of coal reserves were estimated to be present in 1993, all at depths above 300 m. Production was about 2.9 million tonnes in 1993. All coal is produced by opencast methods (Coal Atlas of India, 1993).
THE SOUTH KARANPURA COALFIELD
This coalfield covers an area of 194 km2 in the state of Bihar (Figure A2.1). Structurally it is a narrow elongated trough with a faulted southern boundary. The Bundu-Basaria metamorphic inlier is a major anticlinal feature that occurs towards the eastern end of the coalfield. The coalfield is cut by several faults and some of the seams have been affected by igneous intrusions (dykes and sills) in places.
The Barakar contains 10 coal horizons and there are two additional important seams in the underlying Karharbari Formation. The Raniganj Formation is present but contains no significant seams. The seams generally dip at 15° to 25° but steeper dips are occasionally present.
The coalfield had coal reserves of 5.7 billion tonnes in 1993, when 15 collieries were producing around 5.25 million tonnes coal per annum (Coal Atlas of India, 1993). The Patratu power station is located on the southern fringe of the coalfield.
THE NORTH KARANPURA COALFIELD
This coalfield covers an area of about 1230 km2 in Bihar (Figure A2.1). Structurally the coalfield is a gently dipping elliptical syncline, with dips ranging from subhorizontal to about 10°. It is affected by a number of normal faults but is not significantly affected by the few dykes and sills that are present.
There are five standard coal horizons in the Barakar Formation and one localised seam in the Karharbari Formation. The Raniganj Formation is present but doesn’t contain any significant coal seams.
The reserves of the coalfield were 13.6 billion tonnes in 1993. Production in 1992-3 was 8.14 million tonnes, of which 7.91 Mt was from opencast mines and 0.23 Mt was from three underground mines (Coal Atlas of India, 1993).
THE DALTONGANJ COALFIELD
This coalfield has a total area of about 250 km2 in the state of Bihar (Figure A2.1). Structurally it is a narrow ESE-WNW-elongated basin. It comprises two sub-basins: the Rajhara/Lohari/Kathautia sub-basin in the north and the Singra-Meral sub-basin in the south.
The coal seams are all in the Karharbari Formation. The dip of the seams is generally from subhorizontal to 6°. There are a few igneous intrusions (dykes and sills) but these are not important. The coalfield is also faulted.
There are two main coal horizons containing up to 7 seams in the northern basin and five thin seams in the southern basin. The semianthracitic seams for which this coalfield is well known are found in Rajhara Colliery.
The total coal reserves in this field in 1993 were 0.14 billion tonnes, when the only active mine was Rajhara Colliery, with production of 0.39 Mt in 1992-3 (Coal Atlas of India, 1993).
THE HUTAR COALFIELD
This coalfield has an area of about 207 km2 and is in the state of Bihar (Figure A2.1). Structurally it is a westerly-plunging E-W-elongated basin. The southern boundary of the field is marked by a major fault. The dip is generally 5°-15° but higher dips of up to 20° have been recorded. The seams are not affected by the few igneous intrusions (dykes and sills) in the coalfield.
The Karharbari Formation contains five significant coal horizons with low ash (Seams 1-5). Three or four impersistent coal seams are also present. The Barakar Formation does not contain significant coal seams.
Reserves were estimated at 0.25 billion tonnes in 1993, when 0.02 million tonnes were produced from underground mining at Hutar Colliery, the only operating colliery in the field (Coal Atlas of India, 1993).
THE SINGRAULI COALFIELD
The Singrauli coalfield covers an area of about 2200 km2 in the northern most part of the Sonmahanadi Basin in the state of Madhya Pradesh (Figure A2.1). Only 300 km2 in the NE part of the basin – the Moher sub-basin, is well explored. The rest is thought to have very limited economic potential. The Moher sub-basin is a half graben with a faulted northern margin. Dip typically varies from 3° to 5° but becomes steeper towards the northern boundary fault. There are no intrusions in the Moher sub-basin but it is cut by several faults. There are seams in both the Barakar and Raniganj formations. The Raniganj contains the thickest seam in the country, the 134 m Jhingurda seam. The Barakar contains eight coal horizons of which three are important. Most of the coal is high in ash and of power generation quality only. Total coal reserves were 9.21 billion tonnes in 1993, when 10 opencast mines were produced 30.7 million tonnes of coal in 1992-3 (Coal Atlas of India, 1993).
THE SOHAGPUR COALFIELD
This coalfield has an area of about 3000 km2 and lies in Madhya Pradesh, in the Son-Mahanadi basin (Figure A2.1). Structurally it is divided into two parts by the Bamni-Chilpi Fault. All the coal seams are in the Barakar Formation. The number of coal seams varies across the basin; up to 14 seams are present in the Jhagraghand sub-basin. Known resources were 2.46 billion tonnes in 1993, when 28 underground mines and 5 opencast mines were in operation, producing 9.58 million tonnes of coal in 1992-3 (Coal Atlas of India, 1993).
THE KORBA COALFIELD
This coalfield occupies an area of about 520 km2 in the state of Madhya Pradesh. It lies in the Mahanadi basin (Figure A2.1). Structurally the southern boundary of the basin is faulted-bounded. The dip generally varies between 2° and 8°. Faults are generally aligned E-W with subordinate faults in other directions. The coal seams are confined to the upper and lower parts of the Barakar Formation. These two zones are separated by a barren middle barakar section. The Lower barakar contains 3-4 thin seams containing superior quality non-caking coal. The Upper Barakar contains up to 21 thick, interbanded inferior non-caking seams. In 1993 reserves were estimated at 9 billion tonnes. In 1992-3 27.11 million tonnes of coal were mined, comprising 23.55 Mt inferior and 3.56 Mt superior quality coals. Much of the coal goes to mine mouth power plants and the western India power plants (Coal Atlas of India, 1993).
THE IB RIVER COALFIELD
This coalfield occupies an area of about 1375 km2 in the state of Orissa (Figure A2.1). Structurally the coalfield is a half-graben bounded to the SW by a large fault. The coal seams dip gently away from the field margins towards this fault and the basin centre. 6-7 coal horizons are present in the Karharbari and Barakar Formations, of which only two in the Barakar and one in the Karharbari have economic potential. The Barakar coals vary from 20 to 60 m in thickness. They are banded, have high ash content, high moisture and volatile content and are of low rank. The Karharbari seam is 1 to 7 m thick and generally of better quality.
In 1993, reserves in the field were 20.81 billion tonnes. In 1992-3 7.8 million tonnes of coal were mines, mainly from opencast pits. The coalfield is a major supplier to the western India power stations (Coal Atlas of India, 1993).
THE TALCHER COALFIELD
This coalfield occupies an area of about 1815 km2 in the state of Orissa (Figure A2.1). Only the eastern part, about 400 km2 in size contains exposures of coal-bearing Karharbari and Barakar Formations. Structurally it is a broad synclinal basin with dips of around 3° to 7°. The degree of faulting varies across the field. There are no igneous intrusives (dykes and sills) in the coalfield. There are up to 12 seams in the Barakar and one in the Karharbari. They vary in thickness from 1 to 60 m. All except seam 1 are of low quality (F-G grade), being interbanded, with high ash content, high volatile and high moisture content. The only good quality seam is Seam 1, in the Karharbari, which has ash content <20% (Coal Atlas of India, 1993).
THE PENCH-KANHAN-TAWA VALLEY COALFIELD
This coalfield occupies an area of about 600 km2 in Madhya Pradesh (Figure A2.1). It forms the southern fringes of the Satpura Basin. It can be divided into three parts: Pench, Kanhan and Tawa. The coalfield has a high degree of structural disturbance, particularly in the Pench-Kanhan Valley.
Up to five seams are present in the Pench are, but these deteriorate westwards until only one with any economic importance is present in much of the Kanhan valley. The coals in the Pench area are generally of low rank but in the western part of the Kanhan area rank improves. In the Tawa Valley there are 2-4 seams with economic potential. The upper two seams are generally of inferior grade whereas the highest one has lower ash. In 1993 reserves were estimated at 2.369 billion tonnes. There were 24 mines in the Pench-Kanhan valley, producing 3.6 million tonnes of coal in 1992-3. In the Tawa valley, 7 mines produced 2.47 million tonnes of coal in 1992-3 (Coal Atlas of India, 1993).
THE WARDHA VALLEY COALFIELD
This coalfield covers an area of about 4130 km2 in the state of Maharashtra (Figure A2.1). About 620 km2 is considered to have economic potential at present. Some of the remainder may contain concealed Coal Measures at depth. The degree of faulting in the productive area is low and dips generally vary between 3° and 11°. A single seam, which varies in thickness between 10 and 20 m, occurs over most of the coalfield, although it splits into two in several places. It is highly banded, of low rank and is high in moisture and ash.
In 1993, reserves were estimated at 4.42 billion tonnes. In 1992-3, 15.26 million tonnes of coal were produced, largely from opencast mines. The coalfield feeds the pithead power stations at Chandrapur (Coal Atlas of India, 1993).
THE RAJMAHAL GROUP OF COALFIELDS
This group of coalfields consists of five relatively small coal basins (Hura, Chuperbhita, Pachwara, Mahuagarhi and Brahmani) exposed along the western flank of the Rajmahal Hills (Figure A2.1). In general, the beds dip 5° to 10° to the east, and the coal-bearing formations extend below the Rajmahal traps to the east. The coals are of low rank and high ash content (up to 545). In 1993 reserves were estimated to be 11 billion tonnes of which about 2 billion tonnes are proven. Only the Hura and Chuperbhita fields are mined – the others are untouched. Hura is an important field, producing 3.9 million tonnes in 1992-3 (Coal Atlas of India, 1993).
THE GODAVARI VALLEY COALFIELD
This coalfield covers an area of about 17000 km2 in Andhra Pradesh (Figure A2.1). It consists of discontinuous patches of Coal Measures occurring in the Godavari rift basin. The Barakar Formation contains 3-10 coal seams of which four or five are usually persistent and workable. The coals have high ash and high volatile matter and are of low rank. Generally the lower seams are of better quality. Total reserves were estimated to be 10.8 billion tonnes in 1993, of which 6.1 billion tonnes are considered proved (Coal Atlas of India, 1993).
COALFIELDS IN NORTH-EASTERN INDIA
Although most are very small, there are 67 individual coal fields in the states of Assam, Arunachal Pradesh, Nagaland and Meghalaya (Figure A2.1). These can be divided into: isolated small Gondwana coal deposits along the foothills of the Himalaya (which are not economically important) and at Singrimari in Assam/Meghalaya; Eocene coal deposits along the southern margin of the Mikir Hills and Meghalaya; and Oligocene coal deposits in the thrust belt along the southern side of the Assam valley. Generally, all these coal seams are <1 m thick. They are low in ash (<15%) high in volatile matter and high in sulphur (2-6%).
Total reserves in the northeast region were estimated in 1993 to be 865 million tonnes (Coal Atlas of India, 1993). In terms of production, the most important of these fields is the Makum coalfield in southern Assam.