REGIONAL HEAT-FLOW IN WESTERN ANATOLIA USING SILICA TEMPERATURE ESTIMATES FROM THERMAL SPRINGS

Regional trends of variation of heat flow in western Anatolia have been outlined using the silica temperature estimator on thermal springs. Silica heat-flow values from 187 springs have been calculated. The data are corrected for local long-term mean annual surface temperature. A mean value of heat flow for the western part of Anatolia of 107 +/- 45 mW m(-2) has been obtained, which is about 60% above the world average. The silica heat-flow data are compared with available conventional heat-flow values for this region. A general agreement is observed, and new patterns are recognized. A close association exists between areas of high silica heat-flow values (above 100 mW m(-2)), and areas of Tertiary and younger volcanism. High heat flow is also observed in Palaeozoic units of the Menderes Massif which is under tensional stress. The highest heat-flow estimate of 247 mW m(-2) is obtained near Gediz (38 degrees 57'N, 29 degrees 13.2'E). This area is part of a seismically active region and is located near a Middle Eocene subduction zone which is an area of later collision tectonics. The new heat-flow data from western Anatolia improve our knowledge of the thermal conditions within the crust. This information is important for the analysis of various geophysical and geological phenomena including seismicity.