Heat Flow Anomalies from the Spectral analysis of Airborne Magnetic data of Nupe Basin, Nigeria

摘要

An estimate of Heat flows in the Northern part of the Sedimentary Nupe Basin, West of Central Nigeria has been made from the spectral analysis of aeromagnetic data. This is in view of increased efforts to explore for new and more energy locations in Nigeria. Airborne magnetometer survey maps covering an area bounded by latitudes 8°30' and 10°00' North and longitudes 4°30' and 6°00' East were used as basic data for determining the nature of magnetic anomalies over the area. The maps were digitised at an equal spacing of 0.875 km, thus imposing a nyquist frequency of 0.57 km~(-1). Regional anomaly was removed from the digitised data by fitting a plane surface polynomial and upward continuation technique was utilized to suppress short wavelength components of the residual data. The resulting residual data were subsequently divided into 81 overlapped blocks for the purpose of spectral analysis. The result of the analysis show that the geothermal gradient varies between 10 and 45°C km~(-1) while the ensuing heat flows varies between 30 and 120 mW In the Southeast and Southwest of the study area heat flows were found to be less than 60 mW m~(-2) while flows more than 100 mW m~(-2) are found in the Northeastern and northwestern parts. The average heat flow in thermally normal continental regions is reported to be above 60 mW m~(-2). Values in excess of about 80-100 mW m~(-2) indicate anomalous geothermal conditions. Anomalous high heat flow values (above 100 mW m~(-2)) have been observed in the study area. Therefore, these areas with such variations maybe recommended for further investigation.