The article encompasses the analysis of the mineral composition and geochemistry of weathering crusts of the Svetloborsky and Nizhnetagilsky massifs of the Ural Platinum Belt. Weathering crusts are represented by a partial profile and composed of disintegrated lizardite-chrysotile and loose leached lizardite serpentinite, which are overlapped by clays of nontronite zone at the Svetloborsky massif. The supergene process reveals accumulation of trace elements and rare earth elements (REE) upwards within the weathering profile. Rocks of the Svetloborsky massif con-tacting with dike complexes show high levels of REE content and their accumulation coefficients. In weathering profile of the Svetloborsky and Nizhnetagilsky massifs, the average content of precious metals is low; palladium and platinum prevail, in contrast to primary substrate rocks, where the main platinum group metals are platinum and iridium.
The article encompasses new data on geochemistry of dunites forming the Svetloborsky and Nizhnetagilsky ultramafic massifs of the Ural Platinum Belt. Petrogenesis of both massifs is discussed based on their interpretation. The research establishes that both massifs are petro-chemical equivalents of alpinotype complexes and zonal massifs, but at the same time they have their own particularities. Thus, dunites of the Svetloborsky massif are enriched in almost all rare elements compared to the Nizhnetagilsky massif that may be caused by their redistribution during subsequent processes due to intrusion of mafic dykes.
