ИСТИНА

Precambrian continental shields such as the Anabar, Baltic and Canadian, are the structurally stable areas for at least the last 1.6 Ga. Deeply eroded structures of the shields formed in the process of multistage tectonic evolution, including horizontal shortening and collision, expose at the surface middle to the lower crustal rocks uplifted along the faults from the depths 20-40 km. Thermal and deformation structures formed by the crustal thickening and shortening determine to a considerable extent the further evolution of a tectonic unit, subjected to compression. The results of thermal and mechanical modeling of evolution of collision belts during and after the convergence process have been compared for main governing parameters. Thermal evolution of continental orogens essentially results from the geometry and topography due to thrusting itself and postcollision stage. Analysis of thermal calculations for different heat generation rates and thermal conductivity values of the upper crust shows maximum heating of the area under the maximum uplift. The early postcollision evolution shows some heat flow increase due to the thickening of the upper crust with maximum heat generation rate. Further history leads to the stable heat flow values because additional loading redistribution resulting from the denudation of surface uplift and corresponding sedimentation is small due to the local erosion in our model. It was shown that surface heat losses after the termination of horizontal shortening depend to a greater extent on radiogenic heat generation rather than thermal conductivity value in the upper crust.