ESTIMATION OF CURIE POINT DEPTH AND HEAT FLOW VALUES FROM AEROMAGNETIC DATA, MALAWI RIFT

Curie point depths (CPDs) and heat flow estimates for the Malawi Rift were determined to identify the thermal regime of the rift. We applied the 2D power density spectral method to the aeromagnetic data to determine the CPDs and used the CPDs to estimate heat flow. Curie point depths ranged between 17.8 and 27.5 km. Shallow CPDs occur around the Rungwe Volcanic Province (CPD of 20km), and the Ruhuhu Trough-(Karoo Sediments). Regions of low CPDs also occur in the center and southern part of the rift. Generally, the CPDs get deeper towards the south and at the edges of the rift. The deepest CPDs occur over outcropping granitic and Precambrian basement highs in the western edge of Karonga (26.7 km). The CPD computed heat flow values for the Malawi Rift gave values ranging between 52 and 81 mW m ^-2. In the northern region, high heat flow values (>75 mW m ^-2) occur in the Rungwe Volcanic Province and around Karonga. High heat flow values occur in the central region around Mzimba. Our results also show high heat flow values in the Ruhuhu Trough extending northward in to south west Tanzania. In the south, high heat flow values (69 mW m ^-2) occur around Chileka. Regions of high heat flow values, have several hot springs, suggesting anomalously high geothermal gradient which may indicate the presence of a magma at intracrustal depth.