Compositional peculiarities of the primary, mixed, and oxidized copper ores in gabbroids of the Volkovsky massif (Middle Urals, Russia)

The Ural type magmatic copper deposits in gabbro are assigned to a specific type of copper deposits which exploitation substantially depends on the oxidation degree of the ores, that is often not unambiguous. At the Volkovskoe Cu-Fe-V deposit (Middle Urals, Russia), three technological grades of the copper ores are known, the primary, oxidized, and mixed ones, that are distinguished based on the relative content of Cu2+ in the total copper balance. This paper presents petrological, petrochemical, geochemical, and mineralogical characteristics of natural varieties of the copper ores of the Northwestern zone of the Volkovskoe deposit. It is demonstrated that the criterion for distinguishing the technological grades of the copper ores by the relative Cu2+ content does not reflect the real degree of the supergene oxidation for the selected technological varieties. The results of our research suggest a necessity of studying the copper sulfides in more detail to clarify peculiarities of the redox conditions of the ore formation, to correct the indicators of the primary and supergene copper oxidation degree, which may provide new criteria to determine the boundaries between the technological grades of copper ores, using the Volkovskoe ore deposit as an example.