PbBiO ₂Cl Perite from the Zakharovskoe deposit (NW Altai): first find in Russia

In Russia, PbBiO2Cl perite was first found in the oxidized ores of the Zakharovskoe base-metal VHMS deposit in North-Western Ore Altai. Its chemical composition (wt %, electron microprobe data) is: Pb 43.71, Bi 41.44, O 7.34, Cl 7.57, Br 0.62, total 100.68. The empirical formula is: Pb0.97Bi0.91O2.10Cl0.98Br0.04. The dimensions of its orthorhombic cell are: a = 5.604(1), b = 5.574(1), c = 12.437(2) A, V = 388.5(2) A3. The Zakharovskoe deposit is located in the Rubtsovsk ore region in the North-Western part of Ore Altai. The ores are concentrated in the sedimentological rocks of the Nizhnekamenevskaya subsuite of the Middle Devonian (D2gv2km1) near its border with the underlying Davydovskaya suite which consists of acid volcanic rocks. The main ore minerals are sphalerite, galenite, pyrite and chalcopyrite. The ores are classified as rich if the summary content of copper, lead and zinc exceeds 18 wt %. The Bi content in the ores ranges from 0.006 to 0.014 wt %. Distinct bismuth minerals have not been found. Bismuth occurs as an isomorphic impurity in galenite; its content may reach 0.3 wt %, while the average content is several hundredth parts of percent. Ancient oxidation zone is developed on the field. The type of the zone is copper-zinc with distinct zonation. Perite was found in oxidized ores in the lower parts of the oxidation zone. The mineral is limited to fractures in tuffogenic rocks at a depth ranged from 105 to 109 m. It forms accumulations of thin tabular curved individuals with a typical size of tenth parts of millimeter, up to 0.5 mm. The mineral color is light-yellow with strong adamantine luster. Calcite with native silver and copper was found in the other fractures of this interval. The chemical composition of perite was estimated by the Jeol JSM-6480LV scanning electron microscope (SEM) equipped with the INCA-Wave 500 wave spectrometer (Laboratory of Local Methods of Investigation of Substances of the Petrology Department of Moscow State University). X-ray picture was captured on the Rigaku R-AXIS Rapid II monocrystal diffractometer equipped with a cylindrical IP detector (Debye-Scherrer method, sample to detector distance 127.4 mm, CoKa radiation). The gained results strongly satisfy the reference data for perite. Perite of the Zakharovskoe deposit refers to the bromine-containing variety of the mineral.

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