Produção de calor radiogênico e espessura litosférica damargem rifteada entre o sul da Bahia e o sul de Pernambuco, Brasil oriental

A practical methodology to define the initial lithospheric parameters that controlled the tectono-thermal evolution during the syn-and post-rift phases was applied to the Eastern Northeast Brazilian Rift Margin (ENBRM). Those parameters are input data for basin modelling, either in tectonophysical approach or in petroleum systems modelling approach. The ENBRM developed over two domains of the São Francisco Craton (SFC) to the south and two domains of the Borborema Province (BRP) to the north. The average thicknesses of the continental lithosphere of the main tectonic domains adjacent to the ENBRM were calculated by isostatic adjustment to the mantle geoid, obtained from average values of the mid-ocean ridge, considering a tripartite lithospheric model: radiogenic upper crust of 10 km, remaining crust with reduced Radiogenic Heat Production (RHP) and non radiogenic lithospheric mantle. The lithospheric thickness is defined by its temperature profile with depth, the geotherm, analytically determined, whose parameters are the averages elevation, crustal thickness, crustal density and RHP. The average crustal thicknesses of each domain were obtained by gravimetric inversion of the Moho. The average elevations of each tectonic domain were calculated with cells exported from global topographic and bathymetric grid. Field survey in the basement of the studied margin that acquired 2554 samples supported the determination of the average RHP for each domain. The SFC Itabuna-Curaçá Block (ICB) stands out as the lowest RHP domain, with 0.80 W.m-3 average. The BRP Pernambuco-Alagoas Terrain (PAT) stands out as the highest RHP domain, with 2.40 W.m-3 average. Crustal thicknesses of 37 and 39 km were determined for the two tectonic domains of the SCF with crustal density of 2835 kg m-3, while average crustal thickness of 36 km was determined for the two domains of the PBR with crustal density of 2820 kg m-3. Average elevation ranges From 67 m at EBB to 274 m at ICB. Lithospheric thicknesses of 134 and 135 km were calculated for the two SFC domains, while lithospheric thicknesses of 127 and 129 km were calculated for the two PBR domains.