Abstract
Interpretation of high-resolution aeromagnetic data over Nasarawa area was carried out to observe near surface source magnetic features that are associated with geological structures in the study area, Prominent lineaments in this study may be related to fractures that were not revealed by previous studies. Some of these lineaments coincide with concealed faults and fractures at Akiri warm spring and vicinity. Because this area has known warm springs, faults or fault intersections at depth can lead to upward movement of warm water that enhances permeability. Thus, mapping concealed fractures provides a focus for follow-up geothermal studies. Fault interpretation was accomplished by synthesizing interpretative maps derived from first vertical derivative and analytical signal along with preliminary depth estimates. Faults were interpreted along linear aeromagnetic anomalies and breaks in anomaly patterns. Many linear features correspond to topographic features, such as drainages. A few of these are inferred to be fault-related. The interpreted faults show criss-crossing pattern of fault zones, some of which appear to step over where they cross, and show zones of west-northwest, north-, and northwest-striking faults that cross west-northwest around Akiri warm spring. North easterly striking faults extend east from this juncture. The associated aeromagnetic anomalies are likely caused by magnetic contrasts associated with rifting of crust beneath the Benue Trough.KEY WORDS: Derivative, Structural Pattern, Rift Zones, Akiri.
Highlights
Active areas around the world are generally associated with rift zones, where deep, hot water is brought to surface through fractures or faults (Duffield and Sass, 2003)
The high resolution aeromagnetic data (HRAM) used for this work was obtained from the Nigerian Geological Survey Agency (NGSA) Abuja, which had acquire digital data for the entire country between 2005 and 2009, The airborne survey was carried out for the Nigerian Geological Survey Agency by Fugro airways services, the surveys was flown at 500m line spacing and at an average flight elevation of 80 m along NW – SE direction, and published in form of grid on 30` by 30` sheets
The (1VD) filter enhance the high frequency and short wavelength part of the data, which allows small and large amplitude responses to be more represented to observe near surface source magnetic features that are associated with geological structures in the study area
Summary
Active areas around the world are generally associated with rift zones, where deep, hot water is brought to surface through fractures or faults (Duffield and Sass, 2003). The magnetic field of an area is influenced by geological structures, geological composition and magnetic minerals, most often due to changes in the percentage of magnetite in the rock. A study of these shapes on a magnetic map can reveal much information about the features that are underground. This information can include the location, size and shape, volume or mass, and depth of the features; in some cases, the age of a feature and its material (stone, soil, metal) may be estimated (Telford et al, 1990).
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