Abstract—Analyses of aeromagnetic data were carried out in this study to explore the iron ore deposition, delineate the structural settings and estimate the tonnage of iron ore reserve in Birnin Gwari region of Northwestern Nigeria. The data, which covers latitudes 11° 00' N % 11° 30' N and longitudes 6° 30' E% 7° 00' E, was acquired from the Nigeria Geological Survey (NGSA). The aeromagnetic data was filtered using reduction to the equator and upward continuation filters to accentuate anomalies of interest. The resulted filtered residual map showed closely spaced linear sub-parallel orientation of contours at the central portion of the study area, which suggests the possibility of faults and folds passing through the area. Structural analysis was carried on the filtered residual map, using First Vertical Derivative (FVD) and Horizontal Gradient Magnitude (HGM) filtering techniques, to map out geologic linear structures. The inferred lineament map and its rose diagram revealed that the study area is characterized by geologic linear structures that trends in ENE-WSW, NE-SW, WNW-ESE, NW-SE and NNW-SSE directions, with the ENE-WSW trend dominating. Delineation of suspected Banded Iron Formation (BIF) from other magnetic anomalies was achieved using apparent susceptibility filter and pseudogravity transformation. The resulted maps showed anomalous highs, in an approximately N-S direction, along the suspected BIF. Depth analysis, using the Source Parameter Imaging (SPI) technique, revealed that the depth to the magnetic basement across the area varies between 119 and 1304 m. The region around the suspected BIF is characterized by shallow sources (<300 m) surrounded by deep seated sources (>400 m), which suggests that the iron ore mineralization has an anticlinal structure and probably intruded the Birnin Gwari Schist Belt. The 2D magnetic forward modeling across the suspected BIF revealed an overburden thickness <300 m and a contrasting higher susceptibility of 0.009 (cgs unit) than the modelled neighbouring blocks. Estimation of the iron ore reserve was done using Hammer’s mass model equation. The iron ore reserve was estimated to be ~8.97 x 108.The study therefore concluded that the banded iron mineralization in Birnin Gwari exists, cuts across Sofo Birnin Gwari, Malam Mudi and Kwadaga communities in an approximately N-S direction and has an estimate of ~89.7 million metric tons in reserve.

Index Terms—Aeromagnetic data, Iron Ore mineralization, Filtering, Structural and Depth Analysis, Modelling

Cite:M. U. OHWO, A. H. Falade, Prof. A. A. Adepelumi, and Prof. G. O. Asuen, "Aerogeophysical Mapping and Evaluation of the Banded Iron Formation (BIF) Occurrence in Birnin Gwari, Northwestern Nigeria," International Journal of Geology and Earth Science, Vol. 5, No. 1, pp. 21-40, March 2019.