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Introduction
Fig. 1 [Images not available. See PDF.]
Geological map of Benue Trough. Red box shows the study area.
Magnetic measurements and interpretations play an important role in understanding the variations in earth’s magnetic field resulted from the underlying basement rocks’ magnetic properties (magnetic susceptibilities), geological structures and their geometric shapes and sizes (Abdelrahman et al.2007, 2012; Abdelrahman and Essa 2015; Abo-Ezz and Essa 2016; Biswas 2016; Biswas and Acharya 2016; Essa and Elhussein 2017). At short wavelengths, the data reflect the susceptibility changes that could be associated with the sedimentary rocks and at long wavelengths the magnetic anomalies could reflect the susceptibility changes in the underlying basement (metamorphic and basic igneous) rocks (Telford et al.1998). Magnetic data allow us to delineate the lateral changes in susceptibility associated with the underlying structures and by doing so information about the structural trends and its lithological changes can be inferred. To delineate the subsurface structural features from magnetic data, numerous magnetic edge enhancing techniques have been developed and used by many researchers (Nabighian 1972; Cordell and Grauch 1985; Roest et al.1992; Phillips 1998; Verduzco et al.2004; Salem et al.2007).
Gravity method plays a vital role in recognition of sedimentary basins (Rao et al.1994; Ali et al.2014). There are varieties of techniques and methods for the interpretation of gravity anomalies over or due to sedimentary basins (e.g., Rao et al.1993, 1994; Chakravarthi 1995; Chakravarthi and Sundararajan 2005). The structure of the sedimentary basins is often derived from the gravity anomalies with constant density contrast throughout the section of the basins (Bott 1960). However, the density contrast of sedimentary rocks is not practically constant (Rao et al.1993, 1994; Chakravarthi 1995; Chakravarthi and Sundararajan 2005).
Fig. 2 [Images not available. See PDF.]
Sketch of the geological and tectonics of the study area (after Nigerian Geological Survey Agency 2009). The white dots shows the centre of blocks (e.g., B1, B2, ..., B25). The white line (P1P1) shows the location of profile for the 2D gravity inversion.
The Nigerian Benue Trough is of economic importance for its mineralization potential. It is an elongated rift system, which trends roughly in the NE–SW direction. It is bounded to the NE by the Chad...