Curie point depth (CPD) and thermal anomaly of the Rukwa Rift Basin, SW Tanzania from aeromagnetic data

Curie point depth (CPD) variations across the Rukwa Rift Basin, southwestern Tanzania, were estimated from aeromagnetic data using 2D radially averaged power spectrum analysis. The results reveal pronounced lateral variations in CPD, ranging from 14 km and 33 km, corresponding to estimated surface heat flow values of 51 - 119 mWm -2 . A NW – SE trending zone of shallow CPD (<20 km) and relatively high heat flow (>69 mWm -2 ) is observed in the southern part of the Rukwa Rift Basin, indicating elevated geothermal gradients and surface temperatures. In contrast, deeper CPD values (26 - 33 km) and lower heat flow (51 – 69 mWm -2 ) characterise the adjacent Precambrian basement and the northwestern margin of the basin. These spatial variations are interpreted to reflect spatial differences in crustal thermal structure and the degree of regional thermal demagnetisation, potentially associated with asthenospheric upwelling during crustal and lithospheric extension. The observed thermal anomalies in the southern Rukwa Rift Basin may be linked with inherited lithospheric heterogeneities, including pre-existing basement fabrics that could have acted as preferential pathways for upward migration of hot fluids from the lower lithosphere. If such controls are present, the resulting thermal perturbations may have contributed to localised thermal weakening and strain localisation during rift development. These findings provide new insights into the thermal structure and geodynamic evolution of the Rukwa Rift Basin and suggest that inherited lithospheric heterogeneities may have influenced the spatial distribution of thermal anomalies and the evolution of this segment of the western branch of the East African Rift System, however, further geological and geophysical evidence is required to substantiate this interpretation.