Geochemical features and formation conditions of the cupriferous sandstones of the Orenburg Pre-Urals

Object. The article describes a new geological and geochemical data for Permian host rocks and copper sandstones (CS) in Orenburg’s Pre-Urals. Methods . X-ray fluorescence, atomic absorption for Au and Ag, and ICP-MS analysis were used during investigations. Results. The cupriferous sandstones are enriched in a quite broad range of microelements: Cu, Ag, Au, Cd, Сr, Ni, Mn, Co, V, U, Sc, and Pb, compared to the average values of the upper crust. The Co/Ni ratio in the CS is very low, which is typical of low-thermal fluids of meteoric origin. The CS are characterized by a REE spectrum without Eu-minima and maxima, which is close to the chondrite spectrum. Like in the host rocks, the “cerium” group of REE dominates in the CS over the “yttrium” and “scandium” groups. The spectra of REE of the CS and the host rocks have definitely similar morphology. The δCe and δEu combination indicates that CS was formed under oxidizing conditions. On geological and genetic characteristics and geochemical indicators installed the similarity of the CS in the southern Pre-Urals deposits and the Manto-type Cu-Ag deposits of Chile and Iran, and also with the CS of Iran and Cu-shales of Kupferschiefer. Conclusion. Proposed geological-genetic model of CS, points to possible high rise development of the Cu-Ag mineralization at depth as in the fields of the Manto-type copper deposits in Chile and Iran. Geochemical data show that accommodating the Permian strata could serve as a source of REE and other trace elements for ore-forming fluids. Perm CS of Pre Urals can be considered as a very promising new (“old”) source of raw materials for the development of the copper industry of the region. The obtained results can be used to predict new ore fields in the Eastern Russia region.