Hysteresis and thermomagnetic characteristics of soils and rocks in eastern Botswana

Rock magnetic properties are integral to various applications, including palaeomagnetism, plate tectonics, geological interpretation, geoexploration, mining, forensics, and engineering. This study builds upon previous research on the magnetic susceptibilities of soils in eastern Botswana, focusing on key magnetic parameters such as the Curie temperature (Tc), determined in a nitrogen atmosphere, and hysteresis variables (coercive force: Hc, coercive remanence: Hcr, saturation remanence magnetisation: Mrs, saturation magnetisation: Ms). Thermomagnetic curves, measured from room temperature up to 700 °C, facilitated the classification of magnetic mineralogy and granulometry.

Results

reveal the presence of magnetic minerals such as hematite, magnetite, and pyrrhotite, with Curie temperatures approximately at 600 °C, 580 °C, and 200 °C, respectively. Hysteresis loops further support the dominance of magnetite-like phases in the soil samples. Both hysteresis and thermomagnetic data suggest magnetite as the primary contributor to the magnetic properties. Notably, thermomagnetic analyses of soils along the Ramatlabama to Ramokgwebana transect—crossing the Kaapvaal Craton, Limpopo Belt, and Zimbabwe Craton—offer potential for delineating the boundaries of these cratonic regions and associated orogenic belts. Thus, expanding research coverage across different terrains and geological settings would further enhance our understanding of crustal processes and magnetic mineral distributions invaluable for geological modelling and exploration for raw material deposits.