Abstract

Gravity and electromagnetic methods were combined to characterize known veins and possibly unveil other concealed veins in Tunga, Northeastern Nigeria. Barite occurs in the study area as vein deposits hosted in clean sandstone rocks.  Laboratory analyses of samples show average specific gravity of the variety to vary between 3.16 and 4.24 while the host sandstone rock is 2.63. The study is focused on an area of 0.5 km² measuring 1.0 km in the strike and 0.5 km in the dip (designated X₁ to X₆ in northwest-southeast azimuth) which appears as the most promising terrain in barite prospectivity. Relatively high Bouguer anomalies were recorded over regions that are presumably underlain by barites. Barite mineralization potential varies from high with gravity values of between 177.507 and 181.072 mGals around western flanks of Traverses X₂ and X₃ to medium values (174.681 and 176.801 mGals) around central areas of Traverse X₃. Areas of low Bouguer anomaly were presumably barren (X₁, X₄, X₅, and X₆). The variations in the Bouguer anomaly values are presumably influenced by the density contrast between the barite and the host rocks. Areas of high gravity values exhibit very low conductivity values (< 10 mS/m) and are presumed underlain by dense materials of low conductivity to which barite mineralization can be associated. Thus, in this study, areas of high gravity values accompanied by low conductivities on the western/southwestern flank of the prospect around Traverses X₂ and X₃ are associated with barite mineralization. The trend of mineralization in the area is southwest-wards in the direction of River Benue. Thus, higher barite mineralization potential probably exists beneath River Benue and its southern flank in Tunga area.

Key words: Barite, vein, bouguer anomaly, conductivity, mineralization.