A.A. KOKOVKIN (ITiG FEB RAS)

Specific features of oxidative epigenesis in the margin-continental structure of the southern far east, Russia, and prospects of the region for hydrogenic uranium

Specific features of oxidative epigenesis in the continental margin structure (CMS) in the south of the Russian Far East are described. The productivity of the epigenesis for hydrogenic uranium is estimated. Mesozoic-Cenozoic depressions of the region are represented as relict structures, an integral part of the Holocene orogenic system of the CMS. It is shown that all depressions were upthrown in the Holocene, deformed by upthrow-shift tectonics and eroded, with a cutoff of up to hundreds of meters. A model of uranium mineralization formation in the surface oxidation zone evolving at the incrementally decreasing front of areal erosion, is presented. The evidence is given that the high rate of erosion in the CMS and a number of other factors prevent the ore genesis in this zone. The compression, which is typical of the orogenic CMS system, caused the formation of an exfiltration regime in the groundwater of its depressions. This prevents the formation of large stratal oxidation zones in them. At the same time, the presence of local, uranium-productive stratal oxidation zones in relict paleovalleys is justified in the region. Features of the evolution of uranium-productive fractured infiltration systems are shown.
Keywords: oxidative epigenesis, hydrogenic uranium, Holocene activation, orogeny, tectonics, erosion.