Heat flow and deep temperature in South Portugal

Abstract

Heat-flow density determinations were made in South Portugal. The region of study covers the Algarve Basin, the South Portuguese Zone, part of the Ossa Morena Zone and part of the Lusitanian Basin. Two sets of data were used to obtain heat-flow density values in this region: 13 determinations were made in boreholes under equilibrium conditions and 4 determinations in oil exploration boreholes. Gravity and aeromagnetic data were used to constrain the interpolation of the heat-flow density isolines in the South Portuguese Zone and part of the Ossa Morena Zone. Seismic data were used to model two-dimensional heat transfer through a vertical cross section located in the South Portuguese Zone. The radiogenic heat source distribution was estimated using a relationship between seismic velocity (Vp) and radiogenic heat production (A). A temperature profile was computed taking into account the effect of temperature on thermal conductivity and on the seismic velocity.