Vol 61, No 2 (2019)

South Urals and Rudny Altai: a comparative paleovolcanic and metallogenic analysis
Seravkin I.B., Kosarev A.M.

A comparative paleovolcanic and metallogenic analysis of two massive-sulphide-bearing regions, the Southern Urals and Ore Altai, located in different parts of the Ural-Mongolian folded belt, was performed. Comparison of the geodynamic evolution of these areas, the formation and facies composition of the ore-bearing strata and types of massive-sulphide deposits has led to the conclusion that the regions are similar only in the most general terms. Fundamental differences in the structure and composition of the crust of the regions led to differences in the profile of island-arc magmatism: basaltoid in the Southern Urals and rhyolitoid in Ore Altai. This, in its turn, determined the predominant composition of massive-sulphide mineralization: copper-zinc in the first of the regions and polymetallic — in the second. Opposite tendencies in the evolution of volcanism are also characteristic: homodromic in the Southern Urals and antidromic in the Ore Altai, which resulted in a different position of the types of massive-sulphide deposits in the ore districts: the bottom-up change of copper — massive-sulphide deposits by the massive-sulphide -polymetallic in the Southern Urals and barite polymetallic by massive-sulphide polymetallic and copper- massive-sulphide in the Ore Altai. Significant differences are also in the lateral distribution patterns of mineralization: a more pronounced control of mineralization by paleovolcanic structures of the central type in the Southern Urals and the frequent position of mineralization in intermediate and remote facies of volcanism in the Ore Altai, which is reflected in the prevalence of volcanic sections in the Urals and the majority of the volcanic sections and the larger majority of the volcanic rocks in the Ore Altai, which is reflected in the prevalence of volcanic rocks in the Urals and the majority of the volcanic sections and in the Ore Altai most of the volcanic minerals and the larger majority of the mineral rocks (20–80%) in the strata containing mineralization in the Ore Altai.

Геология рудных месторождений. 2019;61(2):3-22
Mineral types of gold deposits and regularities of their distribution in south-eastern part of the East Sayan
Damdinov B.B.

Based on the mineral composition, gold deposits of the south-eastern part of the East Sayan were typed. The most informative classification criterion for typing is the composition of the gold producing ore mineral associations which are specific to each of the selected types. Whereas using other criteria different structural, composition or genetic characteristics of deposits will necessarily overlap. Eight mineral types of deposits, characterizing the main gold-bearing ore mineral associations were identified: gold-polysulfide, gold-quartz, gold-telluride, gold-tetradymite, gold-stibnite, gold-bismuth-sulfosalt, gold-pyrrhotite and gold-fahlore types. Regional metallogenic divisions such as structural metallogenic zones, differ somewhat in the characteristics of mineralization. Thus, within the Bokson-Garganskaya metallogenic zone, gold-quartz, gold-polysulfide and gold-pyrrhotite types dominate, although gold-telluride and gold-bismuth-sulfosalt types are common in the western part of this zone. In the Ilchir zone, gold-fahlore type deposits are developed. Khamsarinskaya zone is characterized by gold-tetradimite and gold-antimonite deposits existence. It has been established that the mineral types of deposits formation depend on the enclosing rock complexes composition. Thus, gold-quartz, gold-polysulfide and gold-pyrrhotite types are formed in association with the ophiolites and rocks of the Archean crystalline basement. At the deposits associated with granitoid massifs, minerals of metalloids, such as bismuth-bearing sulfosalts, stibnite, tetradimite and tellurides, take a leading role in ores. In the carbonate strata, a gold-fahlore type is formed. The proposed classification allows typing all known gold deposits in the south-eastern part of the East Sayan and can be applied to adjacent regions.

Геология рудных месторождений. 2019;61(2):23-38
Tellurium-bearing minerals in clastic ores of Ybileynoe massive sulfide deposit (South Urals)
Tseluyko A.S., Maslennikov V.V., Ayupova N.R., Maslennikova S.P., Danyushevsky L.V.

At the well preserved Yubileynoe VMS deposit (South Urals), sulfide breccias and turbidites contain abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, calaverite as well as phases of intermediate solid solution tellurobismuthite – rucklidgeite. There is three generation of tellurides were highlighted: 1) primary hydrothermal tellurides in the fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; 2) authigenic tellurides in pseudomorphic chalcopyrite and veins of chalcopyrite after fragments of colloform and granular pyrite; 3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. In sulfide turbidites and gravelites with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts, primary hydrothermal and authigenic tellurides are less common. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, which peripheral parts contain inclusions of epigenetic tellurides. It is assumed that the source of tellurium for authigenic tellurides were fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during post-sedimentation processes. The main concentrators of tellurium in clastic ores are pseudomorphic chalcopyrite, which inherits high contents of Te, Bi, Au, Ag, Co, Ni, As from the substituted colloform pyrite, and varieties of granular pyrite, containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite and hessite (Ag, Te).

Геология рудных месторождений. 2019;61(2):39-71
Impurity elements in quartz from gold deposits of the Darasun ore field (Eastern Transbaikalia, Russia): electron paramagnetic resonance data.
Rakov L.T., Prokofiev V.Y., Zorina L.D.

The distribution of substitutional Al, Ti, and Ge impurities in quartz samples from the Darasun, Teremkinskoe and Talatui gold deposits, located in the Darasun orefield, were studied using the electron paramagnetic resonance method. Relationship between the isomorphic substitution and the dynamic recrystallization of quartz was studied by optical and scanning electron microscopy.

Analysis of the plots of interdependency between the concentrations of various substitutional impurities in quartz (isogens) provided an opportunity to detect isomorphic substitution development trends. Two isomorphic substitution stages were recognized, one associated with mineral crystallization and the other, with its subsequent dynamic recrystallization. The first stage leads to Al impurity incorporation into the quartz crystal lattice, and the second, to Ti impurity incorporation. The Ge impurity is the isomorphic substitution catalyst, and its concentrations vary widely. It is noted that the second stage plays a decisive role, because it accounts for the incorporation of the larger part of substitutional impurities. This process is facilitated by the dynamic recrystallization of quartz.

Four quartz genetic groups, which are described by individual isogens, have been recognized in the Darasun orefield. Two of them correspond to the quartz crystallized from a magmatogenic fluid directly or redeposited with its participation, and the other two correspond to the quartz crystallized from an altered fluid. The facts that substitutional Al concentrations are retained in quartz after redeposition, whereas substitutional Ti impurity concentrations fall dramatically, are demonstrated.

Mineral formation processes at each gold deposit are discussed. Two types of temperature zoning, the normal and the reverse, have been recognized at the Darasun deposit. Each zoning is characterized by an individual quartz genetic group and the extent of mineralization system closedness. The genetically similar magmatogenic quartz samples found at the Darasun and Talatui deposits attest to the uniformity of mineralization process in the Darasun orefield. The established trends of isomorphic substitution in quartz are applicable in the studies of ore formation histories of gold and other ore deposits.

Keywords: Darasun; Teremkinskoe; and Talatui deposits of the Darasun orefield; mineral formation; auriferous quartz; dynamic recrystallization; substitutional impurities; genetic analysis; isogens; isomorphic substitution stages; quartz redeposition; temperature zoning; EPR method; scanning electron microscopy

Геология рудных месторождений. 2019;61(2):72-92

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