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Agbaja, Itakpe |
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Nigeria |
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Fe
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Agbaja, Itakpe and related iron resources are located in on the Agbaja Plateau of southwestern Nigerian, in the vicinity of Lokoja in Kogi and Kwara states and 180 to 200 km SW to SSW of the Capital Abuja.
This region lies within the Benin-Nigerian shield of west Africa, a region that has undergone intense Neoproterozoic (c. 550 Ma) Pan African reworking of what may have been older Archaean and Proterozoic rocks of the East Saharan craton, separated from the West African craton to the west by the north-south trending Hagger Belt. The Precambrian rocks of Nigeria have been simplistically grouped into i). the ancient gneiss migmatite complex, ii). the schist belts, which contain mica- (quartz-biotite-muscovite and garnet) schist, marble, foliated quartzite, meta-chert and BIFs, and the iii). tectonically deformed plutonic series. Overlying these older assemblages are sedimentary sequences of Cretaceous to Tertiary ages deposited in five large basinal areas.
Iron resources on the Agbaja Plateau and surrounding region occur as BIFs, Cretaceous oolitic ironstones and as cemented laterites.
In general, the BIF layers within the region occur sporadically in narrow bands and lenses interbedded with pelitic and semi-pelitic phyllites and schists. They vary in thickness from about 3 to 500 cm and are commonly found in groups intercalated within surrounding country rocks or as isolated thin units. The bands have variable strike extent with some stretching though discontinuously over several kilometres. The most notable iron occurrences include Itakpe, Ajabanoko, Chocochoco, Ebiya Muro Hill and some others. They occur as bands and lenses of banded and sometimes massive BIF dipping between 20 to 85° and are mostly conformable to the host rocks. The tabular bodies, which are up to 45 m thick, and extend for distances from hundreds of metres to over 5 km, are developed to a depth of more than 300 m, and are often displaced by small to large faults. The mineralisation is mostly magnetite and/or hematite with quartz, biotite and amphiboles in the groundmass. Iron content ranges between 15 and 65% averaging 30 to 36%. Enriched zones exceeding 50% Fe apparently a low proportion of the deposits with the bulk grading between the 30 and 50% Fe. Three main BIF facies are recognised, namely oxide, silicate and sulphide. The oxide facies that is represented by a silica iron oxide assemblage is the most widecomprises a quartz-garnet-grunerite assemblage, whil the sulphide facies has only been identified locally.
The Cretaceous sedimentary oolitic iron formations are overlain by an overburden of cemented laterites and detrital iron mineralisation. Two deposits in the Agbaja Plateau area, Agbaja and Itakpe have been investigated in detail and they include both oolitic iron stones and detrital iron accumulations that grade up to 52% Fe. Sulphur and phosphorous levels are low.
The Itakpe deposit is quoted as containing 310 Mt @ 39% Fe, 0.87 to 0.92% P, while Agbaja has potential to contain >200 Mt @ 45% Fe (Abdulla, 1970).
The most recent source geological information used to prepare this decription was dated: 2007.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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