Lithostructural description and metalogeny of Alagbede gold deposit, West Central Nigeria

Alagbede gold deposit located about 25km northwest of Malete in Moro Local Government Area of Kwara State, West Central Nigeria consists of gold-bearing quartz veins as stringers set in metasediments (quartzites and talc schist) overlying the migmatite gneiss basement. It is a southern extension of the northwestern end of Yauri goldfield, resulting from the development of the intercontinental Anka-Yauri-Iseyin (AYI) transcurrent fault during the Pan-African. Evidence of granitization abounds within the gneisses of the area. Structural features mapped in the area include folds, faults and joints. Discordant and concordant shear planes are partly healed with vein quartz ranging from 2-8m depth. The ongoing study indicates the preponderance of a reducing environment of sulphide association with fine-grained gold in vein quartz and schitose rocks. The general NNE to SSW trends suggest a temporal and spatial correlation with other Nigeria goldfields. Keywords: Gold, Deposit, Metasediments, Transcurrent, Fault, Sulfide

Contrasting styles of lead-zinc-barium mineralization in the Lower Benue Trough, Southeastern Nigeria

In the Lower Benue Trough of Southeastern Nigeria, lead-zinc-barium mineralization occurs as widely distributed epigenetic fracture-controlled vein deposits which are restricted to Albian – Turonian sediments. Detailed field studies carried out in Ishiagu, Enyigba-Ameki-Ameri, Wanikande-Wanakom, and Gabu-Oshina which together constitute the four main areas of mineralization in the Lower Benue Trough, show that mineralization appears restricted to NW-SE and N-S fractures while the more common NE-SW fractures are barren. Apart from the Enyigba area, igneous bodies are found in the vicinity of the ore deposits while in the Wanikande area, barite veins and veinlets were observed to be closely interwoven with intrusive bodies. The host lithologies are highly varied, ranging from shales to siltstones, sandstones and occasionally igneous bodies. The ore assemblage also varies remarkably, with lead:zinc:barium ratios ranging from approximately 3:1:0 at Ishiagu, to 2:1:0 at Enyigba, 1:0:2 at Wanikande and nearly 100% barite at Gabu-Oshina. Thus, there is a remarkable increase in barite content from the southwest (Ishiagu) to the northeast (Gabu). The characteristics of the ore deposits roughly fit the base metal type mineralization known as clastic dominated lead-zinc-barium deposits. This study forms part of a mineral potential database which is invaluable for any detailed exploration venture in the area

Structural architecture of the Middle Niger Basin, Nigeria based on aeromagnetic data: An example of a non-volcanic basin

The Middle Niger Basin is located within the west-central half of Nigeria, as a NW-SE trending Campano-Maastrichtian depo-centre which extends from the southern end of the Sokoto Basin west of Kainji reservoir southwestwards to the convergence of the Benue and Niger Rivers at Lokoja. The aeromagnetic anomaly data of the Middle Niger Basin was interpreted to characterize the structural architecture and depth to the magnetic basement of the basin. This is to expand the current knowledge of the region. The analysis of the data has been facilitated by the application of derivative and source parameter imaging techniques. The results from the application of total gradient to the aeromagnetic data provided here signify a rift origin of the basin and NW-SE trending fault systems in the surrounding basement complex terrain. The absence of magnetic highs on the first vertical derivative of the reduced-to-pole aeromagnetic data reveals lack of volcanic rocks within the sedimentary layers of the basin. Additionally, the consistent NW-SE trending source parameter imaging depth solutions within the basin confirm the internal geometry and NW-SE orientation of the basin with sediments not more than 1100 m thick