Aeromagnetic Investigation of Geologic Structures Associated with Gold Mineralization along Danja, Northwestern Nigeria

摘要

The study area falls within the basement complex of northwestern Nigeria and covers four adjacent quarter degree sheets of Funtua, Malumfashi, Masks and Zaria. Gold occurrence in the area was not reported until the recent discovery by artisanal miners. Previous works have shown that primary gold mineralization within the Nigerian basement complex is controlled by geologic structures where they act as conduits for fluids flow and as loci for mineralization. This paper is aimed at characterizing the major structural controls of gold mineralization in the study area. This was achieved by determining depth to basement, producing a magnetization map showing magnetic susceptibility range across the entire study area, and a model of the shape, location and depth of structures in the study area. The anomalies on the aeromagnetic map were defined by fitting a first order polynomial to the total fields, by the method of least squares to obtain the residual field data. First vertical derivative and analytic signal computed, defined distinct pattern of the magnetic signatures. Depths to the surface of the geologic structures (which appears as lineaments on aeromagnetic maps) were obtained from Euler deconvolution solutions which gives an average depths range of 200.2 m to 2229.1 m, with very few solutions having depths less than 300 m. The most prominent lineament and all major subtle lineaments have a depth range of 200 m to 600 m which shows that the structures are deep seated. The magnetic susceptibility values obtained from the magnetization map ranges from 0.000666 to 0.000996 SI. The lineament expected to be the major conduit for possible fluid flow that emplaced the Gold mineralization in the area is suspected to be the continuation of Kalangai fault which trends NE-SW along Malumfashi in the study area.