Cu-sulfde and rare Fe-sulfde nodules up to 2–5 cm in size are found in gray marl siltstones, which occur in a sequence of Permian sandstones of Orenburg Cis-Urals. The Cu-sulfde nodules are characterized by high Cu content (>20 %) and low contents of trace elements (Fe <1.2 %, As, Ag, V, and Pb <130 ppm). They are composed of Cu sulfdes (minerals of the chalcocite group and covellite) with minor barite and mottramite. The Cu sulfdes are transformed to malachite and, to a lesser degree, to chrysocolla and brochantite. The decomposition of Ag-bearing Cu sulfdes leads to the formation of a Ag sulfde. The Fe-sulfde nodules of the Belousovsky mine are composed of pyrite. In the oxidation zone, pyrite is replaced by ferrous opal; single grains of plumbogummite are associated with Fe hydroxides.

Keywords: Cu-bearing sandstones, sulfde nodules, Belousovsky mine, Mikhaylovsky mine, Bronze Age metallurgy.

I.A. Blinov, South Urals Federal Research Center of Mineralogy and Geoecology UB RAS, Institute of Mineralogy, Miass, Chelyabinsk oblast, 456317 Russia; blinov@mineralogy

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