Positive heat flow anomaly in the Carpathian basin

Abstract

Intensive geothermal investigations in the central Hungarian Tertiary sedimentary basin show uniform high temperature gradients between 45 and 70°C/km. New temperature measurements between 3000–5800 m depth confirm previous values between 400–2000 meters. Sixteen heat flow measurements showed values between 2.0 and 3.3 μcal/cm 2 s (84 and 138 mW/m 2 respectively). Sporadic measurements outside the Carpathian basin have shown invariably average or low heat flow and low temperature gradients. The investigation of the crustal structure in Hungary along 5 profiles indicates the depth of the Moho as being between 24.5 and 30.4 km. Comparing the isobaths of the Moho with the temperature gradient map there is an evident relation between high temperature gradients, the consequent high heat flow and the elevated position of the Moho. Areas with high heat flow are found where the Moho is 24.5–26 km deep. The Carpathian basin can be compared with the Black Sea depression where the Moho is 20 km deep. An interesting geothermal similarity exists between the Carpathian basin and the marginal basins of the western Pacific. The Okhotsk, Japan, Shikoku, Parace-Vela basins have a high mean heat flow above 2 μcal/cm 2 s. In the southwestern Pacific, the Fiji plateau and the Lau basin are also characterized by high heat flow. The Japan and Okhotsk seas may represent a subsidence similar to the Carpathian basin, caused by the uplift of the surrounding mountain ranges e.g., Kurili island arc.