PETROGRAPHIC EVALUATION OF THE RANKS AND TECHNOLOGICAL APPLICATIONS OF SOME COAL DEPOSITS IN THE ANAMBRA BASIN AND MIDDLE BENUE TROUGH OF NIGERIA

The coal resources of Nigeria occur mainly within the Benue Trough which include the Anambra Basin. In the Lower Benue Trough/Anambra Basin, sub-bituminous coals occur within the Maastrichtian Mamu Formation in Enugu (Enugu State), Owukpa (Benue State), Okaba (Kogi State) and Ogboyaga (Kogi State). High-volatile bituminous coals occur within the Turonian - Coniacian Awgu Formation in the Middle Benue Trough around Obi/Lafia (Nasarawa State) with outcrop exposures at Jangwa - Shankodi. Organic petrographic results show that huminites dominate the maceral composition of the Anambra Basin coals and have vitrinite reflectance values that range from 0.40 - 0.63 Ro%. In the coals from the Middle Benue Trough, vitrinite macerals predominate the petrographic composition and Ro values range from 0.81 - 1.25%. Based on the petrographic composition and rank evaluation, the sub-bituminous coals in Okaba and Ogboyaga (Anambra Basin) are optimum for combustion and electric power generation and sub-optimum for liquefaction, while the high-volatile bituminous coals in the Obi/Lafia area (Middle Benue Trough), apart from optimum for liquefaction, are the most suitable as raw material for coke making (carbonization) in steel manufacture and as exploration targets for coal-bed methane gas and liquid hydrocarbons.