Lakhra CoalField

General Geology
Lakhra coal is associated with the Bara Formation of late Paleocene age. The stratigraphic sequence is predominantly marine, but also includes lacustrine, estuarine, deltaic and lagoonal deposits containing plant fossils and carbonaceous beds at several horizons. The beds have been affected by orogenic movements of different intensities during different times, resulting in the warping, faulting and dislocation of coal seams.
The coal beds at Lakhra have been gently folded into a major Anticline. Nearly all the coal occurs at shallow depths of 50 to 450 metres from the surface in gently dipping strata of the Anticline, dissected at places mostly with normal faults of 1.5 to 9 metres displacement. Although a large number of coal seams have been encountered in bore holes, only three ofthem are significant and have been named as Dhanwari, Lailian and Kath.

Dhanwari Coal Seam
The top seam, named as Dhanwari seam, was encountered in drill holes at variable depths ranging from 43 meters to 90 meters. It covers an area of 17.61 sq. km. The maximum thickness of this seam is 2:94 meters. The coal of this seam contains 39.8 to 47.6% volatile matter, 32.2 to 40% fixed carbon, 14.5 to 24.5% ash and 6.9 to 8.5% sulphur (Ahmed and others, 1984a).

Lailian Coal Seam
The middle seam is the major coal bed and is known as Lailian coal seam. The coal seam was encountered in drill holes at variable depths ranging from 26.82 meters to 122.83 meters. It lies along the crest of the 68.8 km long Lakhra Anticline. For its correlation, the basal limestone bed of Lakhra Formation has been taken as a marker horizon. The maximum thickness of the seam is 3.17 meters. The coal contains 37.3 to 45.1 % volatile matter, 32.3 to 38.3% fixed carbon, 10.8 to 27.4% ash, 2.3 to 8.3% sulphur. The coal has a calorific value of 10,910 Btu/lb (on dry basis, Ahmed and other, 1984a).

Kath Coal Seam
The bottom seam named as Kath seam covers only an area of 6.12 sq km. The maximum thickness of the seam is 1.4 meters. The coal of this seam contains 43.5% volatile matter, 34.6% fixed carbon, 22.1 % ash and 9.8 sulphur (Ahmed and others, 1984a).

Rank of Coal
The Lakhra coal ranges from lignite A to sub-bituminous C, with high volatile matter (26.3 to 42.5%), high sulphur (1.8 to 6.5%) and high ash (7.4 to 25%). The gross calorific value ranges between 2,570 to 4,260 k.cal/kg of coal. Quality varies widely even within a specific seam. Lakhra coal demonstrates high moisture, high sulphur and low fixed carbon.

The Lakhra coal is dull black and contains amber resin flakes. It can be extracted in large lumps, but dries to a moisture content of about 8% when brought to the surface. It tends to crumble on longer exposures and is often susceptible to spontaneous combustion.

Coal Resources
Till 1986 the recoverable resources of Lakhra coalfield had been estimated at 300 million tonnes (Ahmad and others, 1986). The coal resource base of1,350 million tones has been assessed by Kazmi et al. 1989, at the Lakhra coalfield.