Barite Veins in the Benue Trough: Field Characteristics, the Quality Issue and Some Tectonic Implications

Abstract

The Benue trough is Nigeria's main, but not exclusive source of barite mineralisation. There are at least ten barite fields in the trough, each containing swarms of veins or concordant stratiform minerals flats of hydrothermal origin. There are only two vein trends in the trough: the NW-SE trend, which tends to be orthogonal to the axis of the trough; and the N-S to NNE-SSW trend, which is younger than the former. Both vein sets are formed from ac tension joints reflecting different post-sedimentary deformation phases in the trough. The NW-SE veins are also more frequent than the N-S veins, almost in the ration of 2:1. Although 86 veins have been studied, not one was found oriented parallel to the axis of the trough, a good indication of structural control on mineral vein orientations. The dips of the veins tend to be high (>80 o ), a condition that favours manual mining. Veins tend to display a simple block profile and their widths vary from a few centimetres to as much as 6m, though the most frequently occurring widths are between 50cm and 1m. The implication of this is that BaSO 4 concentrations in hydrothermal fluids in the trough were probably low during the Cretaceous period. In many veins, there is barite quality contrast between the top part and the lower portions. Higher quality barite tends to come from the lower portions. Hence it is expected that much of the low quality stigma associated with Nigerian barite from the trough would be relieved when mining gets down to good depths. For this reason, mining in those veins of low quality barite should proceed by vertical stripping.

Existence of subsurface structures from aeromagnetic data interpretation of the crustal architecture around Ibi, Middle Benue, Nigeria

“…The interpreted fault may in fact be attributed to the Giza fault suggested by Ajayi and Ajakaiye [43] around the study area. Additionally, the occurrence of this anomaly is consistent with vein structures which stretch for 5 to 6 km at Bukuyu village in Ibi [42,44].…”

“…Such intrusions have been confirmed and established by drilling to exist around the region [43]. Also, Chukwu [46,47] confirmed the existence of such volcanic intrusions through field geologic mapping around the area, while Oden [42] suggested sediment-hosted barite occurrences of hydrothermal origin in Gidanwaya of Ibi area.…”

“…The minor N-S and NW-SE trends are more visible on the 3D analytic signal map shown in Fig. 7b; this pattern has been documented to be associated with barites mineralization [42,43]. The NE-trending structural features are almost elliptical in shape, and its magnitude is higher than the associated structural features.…”

“…7a, b: the broad NE-SW-trending structural features which are the dominant trends and the minor N-S and NW-SE trends which occur as associated structures to the former. This domain is suspected to be associated with vein barite mineralization [42]. The minor N-S and NW-SE trends are more visible on the 3D analytic signal map shown in Fig.…”

Baryte mineral exploration in parts of the lower Benue Trough, Nigeria

“…According to the works of Oladapo andOladapo (2011), Luaano et al (2012), Oden (2012), Akpan et al (2014) and Obi et al (2014), high resistivity/low conductivity anomalous values are diagnostic of baryte mineralized veins to which barytes can be associated. The resistivity of baryte mineralized veins ranges from 1300-3999 Ωm, which may likely vary within a wide margin dependent on impurities and BaSO 4 content.…”