Analysis Of High Resolution Aeromagnetic Data Research Articles

Curie-Point Depths, Geothermal Gradients and Sub-Surface Heat Flow Estimation from Spectral Analysis of High-Resolution Aeromagnetic Data over Gongola Basin and Its Environs, Northeastern Nigeria

Geothermal energy resources have been established globally to be among the sustainable and environmentally harmless means of energy generation. Curie-point depths (CPD), temperature gradients, and heat flow data over the study area were computed using a spectral analysis method in order to have a preliminary view of the geothermal implications (prospect) of the current area. Aeromagnetic data acquired by the Nigerian Geological Survey Agency (NGSA) in the year 2009 was used for the research. The results showed the minimum, maximum, and the average CPD values as 8.18 km, 31.48 km, and 13.0 km, respectively. The minimum, maximum and average thermal gradients obtained were 18.42 °C/km, 70.91 °C/km, and 50.2 °C/km, respectively. The heat flow data obtained ranged from 33.15 mW/m2 to 177.28 mW/m2, with an average value of 110.65 mW/m2. Locations depicting shallow CPDs anomalies (Alkaleri, Darazo, Dukku, Misau, Wuyo, Deba, and Tula), also showed conformity with high heat flow areas. As such, they are regarded as areas of promising geothermal prospects and are recommended for further detailed investigation. Locations depicting a high magnetic susceptibility contrast from a generated analytic signal map, as well as high temperature gradients, high heat flow, and shallow CPDs are attributed to crustal thinning along the sedimentary basin and magmatic intrusions along basement areas, respectively. The magnetic depth to the basement calculated for the study area using the source parameter imaging (SPI) method ranges from 0.610 km to 3.055 km. The present study has provided an insight on preliminary information, regarding new areas of possible geothermal prospects for further detailed investigation.

Estimates of Curie point depth, geothermal gradient and near-surface heat flow of Bida and environs, Nupe Basin, Nigeria, from high-resolution aeromagnetic data

The Nupe Basin is a northwest–southeast (NW–SE) trending intracratonic sedimentary basin in the central part of Nigeria with its coordinates defined by longitude 5°00′ to 8°00′ E and latitude 7° 00′ to 11° 00′ N. Spectral inversion of the high-resolution aeromagnetic data was carried out to estimate the Curie point depth (CPD), geothermal gradient and heat flow regime of parts of the Nupe Basin, Nigeria. The estimate of regional temperature distribution and the identification of thermally active regions within the study area were made from the spectral analysis of high-resolution aeromagnetic data which were divided into 16 overlapping spectral blocks to obtain the top and centroid depths of the magnetic sources which were later used to calculate the heat flow characteristics. The estimated Curie point depths range from 21.43–26.71 km with an average CPD value of 24.54 km, while the geothermal gradient ranges between 21.72 °C km−1 and 27.07 °C km−1 with an average value of 24.39 °C km−1. Similarly, the estimated heat flow regime of the study area ranges from 54.30 m Wm−2 to 67.67 m Wm−2 with an average value of 59.41 m Wm−2. The range of estimated geothermal parameters in the study area is an indication that the area is not a volcanic or thermally active region and therefore has little potentials for geothermal energy exploitation. The geothermal play of the area, therefore, was revealed to be of the conduction-dominated play type, typically a combination of the basement and intracratonic basin geothermal play types.

Basement morphology of the middle Benue Trough, Nigeria, revealed from analysis of high-resolution aeromagnetic data using grid-based operator methods

The middle Benue Trough is, the central segment of the Benue Trough, an elongate large intracratonic, Cretaceous to Palaeogene rift basin in Nigeria. This study provides new information about the depth to basement (sediment thickness), basement morphology and tectonics of the middle Benue Trough region through detailed analysis and interpretation of preconditioned high-resolution aeromagnetic data using three grid-based semi-automated depth-estimation methods. Integration of results reveals that the middle Benue Trough region is a moderate to deep, fault bounded rift basin with a maximum sediment thickness (basin fill) of about 6300 m. There are seven deep (>~2500 m) sedimentary sub-basins and several elongated shallow (<~1800 m) basement ridges. These sub-basins and basement ridges exhibit dominant NE-SW tectonic trends. Previously mapped magmatic bodies in the axial region of the Trough occur at depths less than about 1000 m. Most of the imaged subsurface features were previously unknown. Subsurface crustal basement structures show trends predominantly NE-SW, ENE-WSW, NNE-SSW and NW-SE and these generally reflect variations in pre-existing crustal basement structural trends in the area, superimposed by the effects of the regional tectonic stress fields responsible for the Trough's tectonic evolution in the Cretaceous – Palaeogene. The implication of the results in regards to hydrocarbon exploration, particularly when combined with published field geological and organic geochemical studies, is that the middle Benue Trough region is more likely to have moderate to low oil prospects and high gas prospects.