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NUMERICAL MODELING OF GEOTHERMAL FIELDS IN BLACK SEA AND ITS GEOLOGICAL INTERPERTATION Simeon Kostyanev1, Georgi Trapov1, Atanas Vasilev2, Velislav Stoyanov1 1 University of Mining & Geology, Sofia, BG; 2Institute of Oceanology, BAS, Varna, BG. ([email protected]; [email protected]; [email protected]; [email protected]) Keywords: Numerical Modeling, Black Sea, Temperature, Heat Flow, Heat Production Numerical modeling of geothermal fields in Black Sea is of great significance when creating integrated geophysical models of the region and their geological interpreting. Temperature calculation requires the solution of the heat conductivity equation with corresponding boundary conditions. This means extrapolating the measured on the sea bottom heat flow in accordance with assumptions concerning the deep structure of the main geological provinces (based on the explosion seismology), the depth distribution of the heat sources, and the thermal conductivity coefficient. Up to now in Black Sea are measured about 700 value of heat flow [1], part of which we used in our models. In this paper a numerical solution of the steadystate heat conductivity equation in an inhomogeneous media was used to calculate temperature distribution in earth’s crust and upper mantle in Black Sea along three profiles (Fig.1): div(KgradT) = -A, where K(x,y,z,T) is temperature dependent thermal conductivity; A(x,y,z) heat production; T(x,y,z) temperature and x,y,z are coordinates. The boundary conditions are: 1) T(x,y,z=0)=To(x,y) - sea bottom temperature; 2) T/ x= T/ y=0 - symmetry of the temperature fields at the vertical boundary; 3) The last boundary condition – the knowledge of temperature or heat flow at the base of the model, is problematic and Fig.1. Scheme of heat flow stations in Black as rule this information is not available. The solution of Sea Basin with profiles I, II, III. the above problem requires the solution of the inverse problem [2, 3]. To define the block crustal structure and the corresponding distribution of heat sources, the results of deep seismic sounding and new seismological tomography were employed. The crosssection along profiles I, II and III presents a 6-layers media [4]. The proper calculation of the temperature field was performed by the program package Solid Works (COSMOS) 2011. The results of temperature modeling are summarized in schemes, which show the calculated temperatures related to 10, 30, 50, and 70 km. The agreement of calculated temperatures at the points of intersection of the investigated profiles is generally good. The corrected bottom sea heat flow due to the effect of sedimentation range from 50 to 70 mW/m2 [1]. The regional variation of the Moho temperature is from 380 to 720oC. The Moho heat flow may range from 15-25 to 30-40 mW/m2. The crustal contribution to the bottom sea heat flow due to radiogenic heat sources amounts to 10-25 mW/m2 The results clearly confirm the possible existence of the astenosphere under the Black Sea basin. Temperature modeling permits assessing the thickness of the thermal lithosphere. An attempt for a new geological interpretation was performed. References [1] Kutas, R., V. Kobolev and V. Tsvyashchenko. Heat Flow and Geothermal Model of the Black Sea Depression: Tectonophysics, v. 291, 91-100, 1998. [2] Kostyanev S. Mathematical Modeling of Geophysical Fields in Gradient Media (Monograph), Sofia, 200 p.,1999. [3] Vassilev A., V. Tsvyashchenko. Thermal Field of the Earth's Crust of the Bulgarian Black Sea Continental Slope - Inverse Problem Theory Interpretation. In: Geological Evolution of the Western Part of the Black Sea Basin in Neogene-Quaternary, BAS, Sofia, 622-630, 1990. [4] Gobarenko V., T. Egorova. Structure of Lithosphere and Geodynamics in Black Sea Basin, Moscow, Journal Physics of Earth, 6, 50-66, 2010