Arsenocolusite in Pyrite Ores of the Saum Copper–Zinc Massive Sulfide Deposit,North Urals

Geology of Ore Deposits - Pyrite ores on the flanks of the Saum copper–zinc massive sulfide deposit are clastic sediments intensely transformed under conditions of acid diagenesis. Colusite...     

Age and sources of matter for the Kedrovskoe gold deposit,Northern Transbaikal tegion,Republic of Buryatia: Geochronological and isotopic geochemical constraints

The paper presents new geochronological and isotopic geochemical data on gold mineralization of the Kedrovskoe deposit. The deposit is located in the northeastern part of the Transbaikal metallogenic province, Russia’s largest. The Early Permian age (273 ± 4 Ma) of mineralization based on the results of Rb–Sr study of metasomatic rocks is correlated with the age of the final phases of Hercynian magmatism in the Baikal–Muya Foldbelt. The Sr, Nd, and Pb isotopic geochemical characteristics of mineralization show that the host rocks are involved in the formation of the latter. It has been established that ore lead was supplied to the hydrothermal system of the deposit mainly from a geochemical reservoir represented by the Neoproterozoic juvenile continental crust of the Baikal–Muya Foldbelt.     

First Find of Ga-Bearing Minerals in Ores of Ural Massive Sulfide Deposits

Gallium-containing chlorite, mica, and magnetite (up to 14, 13, and 5–7 wt % of Ga) along with Ga hydroxides (oxyhydroxides?) were found for the first time in massive sulfide deposit in the Urals. The minerals identified within the cement of chalcopyrite–sphalerite breccias of the Shemur copper–zinc–massive sulfide deposit (Northern Urals) are associated with Ga-enriched sphalerite, chalcopyrite, and, less commonly, pyrite (33–364, 67–363, and 4–230 g/t, respectively).     

Silver sulfoselenide from ore of the Valunisty Au-Ag deposit,Chukchi Peninsula

Silver sulfoselenide (Ag,Cu)₉Se₂S₄ from ore of the Valunisty Au-Ag deposit on the Chukchi Peninsula is described for the first time. The mineral occurs in mineralized quartz-adularia veins, where it associates with chalcopyrite, sphalerite, galena, and electrum and replaces arsenpolybasite. It forms anhedral grains up to 0.2 mm in size. The reflectivity of sulfoselenide is moderate, no anisotropy is observed, and the microhardness is very low. The chemical composition of the mineral differs from other known members of the Ag-Se-Se-S system: the S/Se ratio of the mineral is 2/1 and the (Ag + Cu)/(Se + S) ratio is about 1.5.     

Mineralogy of oxidized ores at the Ik-Davlyat gold-base-metal deposit,the southern Urals

Three types of oxidized ores are identified in the Ik-Davlyat gold-base-metal deposit in the southern Urals: (1) carbonate-sericite-chlorite mineralized rock, (2) vein-shaped quartz-goethite-illite clay, and (3) limonitized rock related to veins. Heavy concentrate of the first type of ore is composed of goethite, rutile, native gold Au_0.91Ag_0.08Cu_0.01, and chalcophanite Zn_1.02Mn_2.98O₄ · 3H₂O. The second type of ore contains goethite, rutile, Pb-bearing jarosite, native gold Au_0.90?0.93Ag_0.06?0.08Cu_0?0.01Fe_0?0.01, silver amalgamide (schachnerite) Ag_0.75Hg_0.97Au_0.98-Ag_0.75Hg_0.97Au_0.28, coronadite (Pb_1.72Mn_7.51Fe_0.41Cu_0.36)₈O₁₆, a chalcophanite-hydrohetaerolite mixture, and cerussite. Gold of the highest fineness (Au_0.98Ag_0.01Cu_0.01) is associated with silver amalgamide. The third type of ore is quite similar to the first variety but contains a jarosite impurity. The composition of oxidized ores indicates a difference in composition of primary ores, in particular, the presence of lead minerals in primary veins. The first finding of chalcophanite in Russia is confirmed by chemical, optical, and X-ray data.     

Mineralogical and Geochemical Features of Oolitic Ironstones from the Sinara–Techa Deposit,Kurgan District,Russia

The paper discusses the mineralogical and geochemical features of oolitic ironstones from the Sinara–Techa deposit, Transural region, Kurgan district. The ore unit is localized in the lower part of a thick Mesozoic–Cenozoic sequence of sedimentary rocks that fill the West Siberian Basin beneath calcareous clay and overlying beds enriched in glauconite and clinoptilolite. The ironstone consists of goethite ooids in smectite–opal cement. Accessory minerals are pyrite, galena, sphalerite, and monazite. The texture and structure make it possible to suggest the formation of sediments enriched in iron as a result of colloid coagulation. The most probable source of iron is related to inland drift. Deposition of iron took place in the estuaries of subtropical rivers due to mixing of colloidal solution of river water with seawater electrolyte. The chemical features of rocks are controlled by the composition of the adsorbed iron oxi/hydroxide complex.     

Florencite-(Sm)—(Sm,Nd)Al3(PO4)2(OH)6: A new mineral species of the alunite-jarosite group from the subpolar urals

Florencite-(Sm), a new mineral species of the florencite subgroup, was found in association with xenotime-(Y) in quartz veins of the Maldynyrd Range of the Subpolar Urals as thin zones within rhombohedral crystals of florencite-(Ce) with faceting by { 01[`1]1}\{ 01\bar 11\} and { 10[`1]2}\{ 10\bar 12\} . The thickness of particular florencite-(Sm) zones is 0.01–0.1 mm, and the total thickness of a series of such zones is 1–3 mm. Florencite-(Sm) is colorless and pale pink or pale yellow with white streaks; its Mohs hardness is 5.5–6.0. Its measured and calculated densities are 3.70 and 3.743 g/cm³, respectively. The mineral is transparent, nonpleochroic, and uniaxial (positive), and ω = 1.704(2) and ɛ = 1.713(2). The electron beam’s fluorescence spectrum was 592 nm (intense green luminescence of Sm³⁺) and 558 nm (yellow luminescence of Nd³⁺). The chemical composition was as follows (microprobe, average of 2 WDS, wt %): 0.62 La₂O₃, 3.29 Ce₂O₃, 1.05 Pr₂O₃, 10.31 Nd₂O₃, 12.62 Sm₂O₃, 0.41 Eu₂O₃, 2.30 Gd₂O₃, 0.13 Dy₂O₃, 0.71 SrO, 0.35 CaO, 29.89 Al₂O₃, 26.14 P₂O₅, 0.85 SO₃, 0.09 SiO₂, 88.76 in total; 10.74 H₂O (meas.). The empirical formula based on 14 oxygen atoms is (Sm_0.38Nd_0.32Gd_0.07Ce_0.10Pr_0.03La_0.02Eu_0.01Sr_0.04Ca_0.03)1.0Al_3.04(P_1.91S_0.05Si_0.01)_1.97O₁₄H_5.92. The idealized formula is (Sm,Nd)Al₃(PO₄)₂(OH)₆. Mineral is trigonal, space group R3m, a = 6.972(4), c = 16.182(7) ?, V = 681.2 ?³, Z = 3. The XRD pattern is as follows: dln (I) (hkl): 2.925 (10) (113), 1.881 (6) (303), 2.161 (5) (107), 5.65 (4) (101), and 3.479 (4) (110). The IR spectrum: 466, 510, 621, 1036, 1105, 1223, 2957, and 3374 cm⁻¹.     

M?ssbauer spectroscopy of Pb-bearing minerals from the jarosite group

The minerals of the jarosite group, including the jarosite-beudantite-segnitite and jarosite-beaverite-osarizawaite isomorphic series, were studied with M?ssbauer spectroscopy. All the samples were collected from the oxidation zones of the South Urals sulfide deposits. In contrast to the jarosite containing one Fe³⁺ doublet in the M?ssbauer spectrum, the Pb-bearing members of the jarosite group—beudantite and beaverite—have two doublets in their spectra. Fe³⁺ is distributed at two sites with similar isomer shifts and different quadrupole splitting. The quantitative ratio of those doublets in the structure is roughly equal. The M?ssbauer spectra of the intermediate jarosite-beudantite and beaverite-osarizawaite members are superpositions of the jarosite and beudantite spectrum types with a prevalent jarosite doublet and larger quadrupole splitting. An admixture of antimony increases the Fe³⁺ content in the doublet with smaller quadrupole splitting. The unequal Fe³⁺ distribution in those two sites may be related to the ordering of cations in octahedrons. The appearance of two different Fe³⁺ sites probably resulted from the local coordinating role of Pb rather than from isomorphic replacement in anion groups.     

Cobalt behavior during natural and technogenic oxidative leaching of Co-containing pyrites (Letnee chalcopyrite deposit,Southern Urals)

Cobalt behavior during the oxidation of sulfide ores, unlike that during the oxidation of Co ores, is poorly known. Moreover, cobalt sulfates are rare in the world. Complex hydrous cobalt-containing and cobalt sulfates have been found in technogenic zones at the Letnee chalcopyrite deposit (Southern Urals). They have been identified at pit bottoms, in the ore stockpile, as well as directly on ore fragments and the evaporation barriers of underdump water puddles. The paper reports the first experimental data on the oxidative leaching of Co-containing sulfide ores in the laboratory. Also, parts of a thermodynamic model for Co behavior in oxidized zones are presented.Experiments have revealed an increase in acidity up to pH = 4.14, along with transport of sulfate sulfur and metals into solution. This suggests acid mine drainage during the development of the Letnee deposit. The published stability diagrams for hydrous Cu, Mg, Zn, Co, and Ni sulfates were analyzed and compared with mineralogical finds in a technogenic oxidized zone. This made it possible to explain the precipitation sequence of minerals from solutions during their concentration by evaporation. As salts of these elements are highly soluble, significant contents of toxic metals will inevitably remain in equilibrium solution, necessitating additional waste-water treatment (for example, creating sorption geochemical barriers). Therefore, the paper describes regularities in Co behavior during its sorption on solid phases.