Heat flow in the Alboran Sea, western Mediterranean

The results of the first regional heat flow survey carried out in the Alboran Basin are presented. The survey consists of 98 heat flow measurements obtained using a violin type probe, 697 nautic miles of gravity profiles, 1446 nautic miles of bathymetric survey, and 22 gravity cores. A remarkable difference in heat flow patterns exists between the western (WAB) and eastern (EAB) parts of the Alboran Basin. The average heat flow in the WAB is 69 ± 6 mWm-2 with a generally increasing trend towards the centre and to the east. In contrast, the heat flow pattern in the EAB shows an average value of 124 ± 8 mWm-2 and it is maintained rather constant for the overall area. Superimposed on this general pattern there are some local thermal anomalies, associated with hydrothermal activity, which have been detected in the central WAB (up to 123 mWm-2), in the South Alboran Basin (SAB) (up to 153 mWm-2) and in the Djibouti Bank (DB) (up to 254 mWm-2). After corrections for thermal refraction, sedimentation and cooling of volcanic bodies, the resulting heat flow distribution in the WAB is smoother, but still shows the increasing trend towards the centre and to the east. In the EAB, the application of these corrections did not lead to any noticeable changes. A 1-D approach that combines heat flow data, crustal structure and elevation shows a dramatic decrease in lithospheric thickness from the WAB (50-90 km) to the EAB (38-40 km). Likewise, the resulting crustal thickness is around 14-16 km in the central part of the WAB, increasing towards the borders of the basin, whereas in the EAB the crustal thickness varies between 12.5 and 14.5 km in its western part, and between 10 and 11.5 km in its eastern part.