Geochemical features of the Lower Ordovician deposits at the Podcherem river source (Northern Urals)

The article presents the results of studying the material composition of Lower Paleozoic metaterrigenous rocks in the contact zone between the Riphean-Vendian Preuralide complex and the Caledonian-Hercynian Uralide complex. These deposits are the most promising object for the search for gold and rare-earth-rare-metal mineralization in the northern part of the Northern Urals. Based on geochemical data, it was established that the formation of quartzite sandstones and siltstones composing the section took place in a cold climate in the coastal-marine zone of the passive continental margin. Metaaleurolites and, to a lesser extent, quartzite sandstones contain unchanged volcanoplastics. The siltstones inherited the composition and geochemical features of the acidic volcanites of the Sablegorskaya formation, which are widely developed in the region. Quartzite sandstones are distinguished by the best sorting and maturity of the detrital material, and their composition is dominated by the products of erosion of ancient metamorphic formations. The main factor influencing the formation of the sediment composition was the mechanical destruction of metamorphic and igneous rocks that were slightly weathered in a cold climate. The level of REE contents and the nature of their distribution are typical for sedimentary rocks formed in shallow coastal-marine conditions with low-amplitude fluctuations in sea level. Sediment accumulation took place in a basin with a calm hydrodynamic regime in the immediate vicinity of sources of terrigenous material.