Curie point depth analysis of aeromagnetic data of Kasane region in northwest Botswana and surrounding regions for geothermal investigation of Kasane Hot Spring

Abstract

The Kasane Hot Spring with discharge temperatures of 43–50 °C is characterized by intermittent bubbling accompanied by white precipitant within its vicinity. The hot spring discharges mainly along Chobe River which meets the Zambezi River at the tip of northwest Botswana. In this study the Curie point depth (CPD) was estimated using the spectral centroid method of aeromagnetic data at Kasane Hot Spring and the surrounding regions. The upward continued aeromagnetic data were analyzed to obtain depths to the bottom (CPD) of the magnetic sources. The CPD values were then used to compute the geothermal gradient, subsurface crustal heat flow including radiogenic heat flow distribution in the region.According to the obtained results, the depth to the magnetic bottom varies from 6 to 22 km. These depths are comparable to those obtained from recent regional study of the Okavango Rift Zone. The areas with shallow CPDs of demagnetized rocks at depth are located around Kasane Hot Spring, where high heat flow values in the range 70–90 mW/m2 were recorded. Moreover, the radiogenic heat production values between 0.50 and 0.60 μWm-3 within the same region may also provide an extra contribution to the geothermal potential of Kasane Hot Spring. The correlation of estimated shallow CPDs with high geothermal gradient, high heat flows, and radiogenic heat flow values at area within Kasane region indicate possible geothermal resource. The CPDs values obtained may be associated with the seismic events in the region and surroundings. The mean earthquake depth of events that occurred within Kasane and surrounding areas from 1987 to 1991 is 10 km, while the mean Curie Point Depth is approximately 11 km. These seismic events in the area could be responsible for possible thermal accumulation at Kasane Hot Spring, resulting in high heat flow values in the area.