Mineral Composition of the Productive Formation and Features of Chromites of the Lukoyanovsky Placer Area (Nizhny Novgorod Region)

As a result of geological exploration within the Lukoyanovsky placer district (Nizhny Novgorod region), increased contents of chrome spinel reaching an industrial level of up to 100 kg/m were established in complex coastal-marine rare metal-titanium placers, while their source is not obvious. In addition to chrome spinel, industrial components of placers are ilmenite, zircon and rutile. Morphological features of ore minerals make it possible to assume several sources of ore material transportation, both proximal and distant. Moderately mature mineral composition of the heavy fraction (increased amount of minerals unstable during weathering) indicates that the formation of Permian-Jurassic deposits of this region occurred without the participation (or with weak participation) of chemical weathering crusts. During the mobilization of detrital material in the source zone and during the formation of intermediate reservoirs (Permian and Early Mesozoic complexes of the sedimentary cover of the Ural part of the East European platform), mechanical processes prevailed with a subordinate influence of crust formation. The study of the chemical composition of chrome spinel of the most studied and promising Itmanovskaya placer showed that they are mostly similar to the same-name minerals of the ophiolite formation, as well as concentrically zoned platinum-bearing massifs. It seems that with the general influence on the formation of the sedimentary cover of the central and eastern parts of the East European platform at the Permian-Triassic boundary of the Ura-lide paleoorogen, the Puchezh-Katunka ring structure, located to the north of the Lukoyanov dome, had a noticeable effect on the composition of the heavy fraction of sediments in the region.