THE GEOLOGIC PLAY AND THE NIGERIA SOLID MINERAL SECTOR
Geology, the study of rocks, minerals and the physical make-up of the solid earth, determines the environment and natural resources and, hence also, the industrial potentials and wealth of a nation. After climate, geological factors exert, perhaps, the greatest impact on economic activities, since soils, water supply and vegetation are, to a large extent, influenced by the nature of the underlying bedrock.
The vast ocean margin that borders Nigeria to the south; the intricate drainage systems that sculpture the physical landscape; the mountainous eastern frontiers; and the wind-swept northern hinterland, with the Great Plains on the Saharan fringe, are all part of the surface geological features that bestow upon Nigeria its unique physical attributes.
It could, perhaps, perplex the ordinary mind that, whereas Nigeria exhibits bewildering cultural diversity, the landscape is a continuum in a seamless physical web that unites the physical entity termed Nigeria, regardless of political differences which are mere human artefact.
For example, the Niger-Benue drainage system, which has, over the long geological period of 55 million years, supplied sediments from the Nigerian hinterland for the construction of the petroleum-rich Niger Delta on the coast, has demonstrated the long-term impact of unifying geological processes in a nation with divergent human interests. Economic self-sufficiency is also feasible in Nigeria, where the diversity of rocks and mineral wealth, combined with cheap sources of renewable and non-renewable energy, create an enormous industrial potential.
Nigeria is richly endowed with a variety of solid minerals ranging from precious metals various stones to industrial minerals such as lead, zinc, copper, pyrite, chalcopyrite, barites, gypsum, kaolin, tin, iron ore, marble, lithium, ilmenite etc. Most of these are yet to be exploited. Statistically, the level of exploitation of these minerals is very low in relation to the extent of deposits found in the country. One of the objectives of the new National Policy on Solid Minerals is to ensure the orderly development of the mineral resources of the country.
The recently created Ministry of Solid Mineral Development has been a major stimulus to the Nigerian mining industry. It offers a viable alternative to petroleum for foreign exchange earnings. Globally, the mining industry has been a close rival to the petroleum industry, although Nigeria earns currently a paltry $89 million per annum from it. With the restoration of democratic government, bright prospects for solid minerals development await the nation.
Several factors stimulate the mining sector. First is the diversity of Nigeria’s metallic and non-metallic minerals. Second, companies are prepared to bear exploration costs and risks, given a favourable policy framework. The new national solid mineral policy of the Federal Government, which replaced the old mining laws and regulations, has offered a competitive environment for solid minerals development.
GEOLOGY OF THE LOWER BENUE TROUGH OF NIGERIA (ABAKALIKI TROUGH)
The Benue Trough has been subdivided into three sections or regions for easier stratigraphic and sedimentological correlation and analysis namely; the Upper Benue Trough, the Middle Benue Trough and the Lower Benue Trough, the study area is located within the Lower Benue Trough.
The oldest sedimentary basin in the Lower Benue Trough of Nigeria, the Benue – Abakaliki Trough, originated in Early Cretaceous as the failed arm of rift-rift-rift (RRR) triple junction associated with the opening of the South Atlantic Ocean.
Structural movement in the Benue-Abakaliki Trough began in Coniacian time and culminated during the Santonian. The Benue-Abakaliki Trough was uplifted to form the Abakaliki Anticlinorium along some NE – SW axis. The structural inversion was accompanied by the formation of depression on either flank- the small Afikpo Syncline on the southeast and the much wither Anambra Basin on the northwest, thus there existed three sedimentary basins from Companian to the Paleocene; the Anambra Basin and the Afikpo Syncline separated by the Abakaliki High.
STRATIGRAPHIC SUCCESSIONS IN THE LOWER BENUE TROUGH
The major controls of sedimentation in the Benue Trough resulted from world-wide eustatic change in sea level and basin tectonics. The earliest sediments in southeastern Nigeria (Lower Benue) were the Aptian-Albian pyroclastics; these formed the basal unit of the Albian-Cenomanian depositional sequence and were overlain by about 3,000m of sediments of the Asu River group. These are the dark, micaceous and sandy Shales and the fine-grained Sandstones. Cenomanian sediments, Sandstones, sandy Shales and fossiliferous Limestones, have been found in the most southeastern part of the trough along the Calabar Flank.
Fig. 1: Geology Map of Nigeria.
During the Turonian and Coniacian times a thick marine sequence of grey, calcareous, fossiliferous Shales were deposited. These Shales called the Eze Aku Shales have been observed to grade laterally into sandy Shales and calcareous Sandstones, the Amasiri Sandstones. During this major transgressive phase, the Eze Aku Shales and the Awgu Shale were deposited. The Eze Aku Shales grade into the marine Awgu Shale. These depositional cycles were interrupted by widespread Santonian movements which resulted in folding of the trough sediments and were also accompanied by magmatic activity and the emplacement of lead-zinc mineralization, lead-zinc mineralization is basically associated with the Benue Trough and occur in a linear stretch of the trough of about 800km from the lower, middle and upper part of the trough. Lead-zinc occurrences in Nigeria are associated with saline water intrusion in the sedimentary basins or fractured / shear zones in crystalline rocks. The mineralisation is often associated with minor to significant amounts of copper and silver, occurring in lodes filing the fractures within the sedimentary rocks in the Benue Trough as well as in crystalline basement rocks as shown in recent studies by Nigerian Geological Survey Agency. Precisely, lead/zinc deposit kind be found in the follow states in Nigeria; Ebonyi, Benue Nasarawa, Taraba, Plateau, Bauchi, Adamawa and Gombe.
Abuja and Ebonyi State play home (Headquarter and branch/field office respectively) to EarthCrust Geo-Tech Exploration Limited, the Nigerian solid mineral sector is in a developing phase with several indigenous geophysical and mining companies contributing a large quota to this greenish investment opportunity and EarthCrust hope to take mining in Nigeria to its next level that will provide a mutual beneficial advantage to the government in terms of tax and returns, host communities in terms of loyalty, workers in terms of good remuneration and the company in terms of return to its investment.