Vol 61, No 1 (2019)

ARTICLES
Localization patterns of mineralization, age, and sources of substance of the Malomyr gold ore field (Eastern part of the Mongolian–Okhotsk fold belt)
Kadashnikova A.Y., Sorokin A.A., Ponomarchuk V.A., Travin A.V., Ponomarchuk A.V., Eyrish L.V.
Abstract

To the best of our knowledge, this study is the first to reliably assess the age of gold mineralization in the Malomyr field (eastern part of the Mongolian-Okhotsk fold belt), one of the best known deposits in the Far East. The obtained data confirmed that the age of the hydrothermal ore process that resulted in the formation of the Malomyr deposit was ~ 134–130 million years and that the age of the postore dykes was 110–104 million years. Data related to the occurrence of magmatism within the region under consideration were not available, which made it impossible to link the ore mineralization of the Malomyr deposit with the magmatic processes. Based on the data obtained in this investigation, the dislocation processes accompanied by the hydrothermal activity that was confirmed using the structural examinations results evidently played a significant role in ore mobilization and redistribution as well as the formation of the Malomyr deposit. The first Rb-Sr and δ34S results of this research indicated that both the “crust” and “mantle” sources were available among the ore sources.

Геология рудных месторождений. 2019;61(1):3-17
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Conditions of ore formation of the Aunikskoye F-Be deposit (Western Transbaikal)
Damdinova L.B., Damdinov B.B., Rampilov M.O., Kanakin S.V.
Abstract

This study examines the compositions of the ore and the ore formation solutions, conditions of formation, and sources of Be mineralization using the Aunikskoye F-Be deposit, which is an integral part of the Western Transbaikal beryllium-bearing provinces, as a representative example. Further, the main factors responsible for the formation of beryllium mineralization were evaluated. The ore deposits are presented by the feldsparic–fluorspar–phenacite–bertrandite metasomatites formed in the carboniferous limestones during their metasomatic alternation with hydrothermal solutions by introducing F, Be, and other associated elements. The formation of early phenacite–fluorspar association occurred in high-fluorite СО2-containing solutions of elevated alkalinity with a salinity of ~10.5%–12% wt eq. NaCl in a temperature range of ~ 370–260 °С at pressures ranging from 1873 to 1248 bar. More recent fluorite and bertrandite deposits were formed by solutions with a salinity of 6.4%–7.7% wt eq. NaCl in a temperature range of ~156 °C–110 °C and a pressure range of 639–427 bar. The examination of the isotopic signature of the ore association minerals confirmed the apocarbonate nature of the main ore deposit and allowed the determination of the magmatogene nature of the ore-forming paleothermal springs, which are the source of subalkaline leucogranites. The primary factors that influenced the formation of the F-Be ore included the reduction of the F activity in solutions because of the binding of Ca and F in fluorite as well as because of the decrease in temperature during the ore deposition process. The elevated alkalinity of the ore-formation solutions resulted in the low solubility of the Be complexes, which caused a relatively low Be content in the ore and a relatively small amount of mineralization in the deposit.

Геология рудных месторождений. 2019;61(1):18-38
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Isotopic (δ34s, δ13c, δ18o) properties of the disseminated mineralization of plutonic rocks in the Dukat ore field (Northeast of Russia)
Dubinina E.O., Filimonova L.G., Kossova S.A.
Abstract

The variations in the δ34S, δ13C, and δ18O values of the disseminated sulfides and carbonate phase, which occurred in trace amounts in the plutonic rocks controlling the position of the unique Dukat Au-Ag field (Northeast of Russia), were examined. These properties were compared with similar isotopic parameters of the ore associations in the field. The δ34S values of sulfides and jarosite obtained from plutonic rocks were in a relatively narrow range (from −3.4 to +3.6‰) when compared with the range of variation of the δ34S values of sulfides obtained from the ore bodies (from 4.5 to +2.0 ‰). Pyrite sulfur obtained from the early mineralization of K-Na-leucogranite and pyrite obtained from the ore bodies were observed to have the same source. Pyrite formed during the later magmatic stages is characterized by a small amount of lighting based on the sulfur isotopic signature. The carbonate phases of the plutonic ore in the Dukat ore field are characterized by the δ13С values (from 12.8 to 8.8‰). The carbonates are split into groups according to the oxygen isotopic signature: carbonate balanced with the rock silicate matrix at high temperatures and carbonate with abnormally low δ18О values (from −0.8 to +0.9 ‰). The obtained data can be described using the model that assumes that the formation of the isotopic parameters of sulfide sulfur and carbonate carbon occurs during the process of sulfate recovery using organic carbon oxidation (TSR). Further, the calculations revealed that the observed δ34S and δ13С values in the rocks and ore associations in the Dukat field can be obtained during the abiogenic recovery of marine sulfate in a temperature range of 300 °C–450 °C. The comparison of the isotopic parameters of the rock carbonate with those of the ore association carbonate demonstrated that the surrounding/base rocks and fluid that separated during the cooling of the K-Na-leucogranite intrusion bodies, which resulted in a loss of approximately 80% CO2, could serve as the source of the carbonates of the ore bodies.

Геология рудных месторождений. 2019;61(1):39-51
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Primorskoye epithermal Ag-Au deposit (Northeast of Russia): geologic aspects, mineralogic and geochemical features, and ore formation conditions
Savva N.E., Volkov A.V., Sidorov A.A., Kolova E.E., Murashov K.Y.
Abstract

As a potentially large Ag-Au epithermal deposit, Primorskoye comprises the following three areas: Kholodny, Spiridonych, and Teply. This deposit is located in the Omsukchan district of the Magadan Region, where similar deposits, including Dukat, Lunnoye, Goltsovoye, Arylakh, Tidit, and Perevalnoye, have developed. The deposit can be attributed to the Kalalagian volcano-tectonic depression and is localized in a flat-lying rock mass in the Late Cretaceous ignimbrites and rhyolites having thicknesses of greater than 700 m, which is cut through by numerous dykes of medium and major composition. According to the drilling data, the solid mass of leucocratic granites is located in deposits at a depth of 400–500 m with outcrops in the northeastern part of the ore field. The presence of Bi-containing galena and matildite, the availability of mid and high temperature facies of metasomatites (epidote and actinolite), and the specific physical and chemical conditions during the formation of the epithermal Ag-Au ores indicate the intrusive position above and the role of granitoids as generators of high temperature magmatic fluids, which introduced Bi and heated the rocks enclosing the mineralization. The geochemical features of the ores are well correlated with their mineral compositions. The high concentrations of Mn and Ag, elevated concentration of Au, low concentrations of Cu, Pb, Zn, Sb, As, Bi, and Te, low sum of REE, and negative Eu- and positive Се-anomalies were observed. The high values of the Te/Se, Sr/Ba, Y/Ho, and U/Th indicators in the ores are associated with the deposit location in the zone of granitoid massif effect. Further, the physical and chemical parameters of ore formation in the Teply area are unusual and are characterized by high temperatures, low concentrations of salts, and fluid density, which are indicative of the typical “dry steam” conditions. The obtained results allow the Primorskoye epithermal deposit to be attributed to the intermediate class. The information present in the article is practically valuable for the regional forecast and metallogenic developments as well as for searching and assessing the epithermal Ag-Au deposits.

Геология рудных месторождений. 2019;61(1):52-74
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Compensating H+ and Li+ ions in quartz structural channels of the gold fields of Darasun ore field (Eastern Transbaikal, Russia): electron paramagnetic resonance data
Rakov L.T., Prokofiev V.Y., Zorina L.D.
Abstract

The composition and diffusion mobility of the compensating ions in the quartz structural channels of the gold fields in the Darasun, Teremkinskoye, and Talatuy gold fields of the Darasun ore field were examined using the electron paramagnetic resonance method. The assessment of the properties and peculiarities of the ion distribution in quartz was based on their ability to participate in the neutralization of the electric charges of the structural defects occurring in the minerals. In this regard, the ion composition was evaluated by the ratio of the concentrations of the Ti-centers using various compensators. Their mobility was determined by the center formation rate during the quartz radiation exposure. The research demonstrated the availability of two major compensating ions, H+ and Li+, in the quartz structural channels of the gold fields in the Darasun ore field. The diffusion mobility of the H+ ions in the channels was observed to be 1–2 orders of magnitude higher than that of Li+. The correlation link between the compensating ions in the mineral and fluid compositions was not obtained based on the data analysis. A difference was identified between the ratio of the H+ and Li+ concentrations in the quartz structural channels of different fields. Further, the highest concentration of H+ ions and the lowest concentration of Li+ ions were recorded for the quartz in the Darasun field; the inverse correlation was observed for the quartz in the Talatuy field, which can be attributed to the mixing of the fluid gas component during the ore formation process. The electron paramagnetic resonance method can be used for the quantitative assessment of the degree of quartz dynamic recrystallization.

Геология рудных месторождений. 2019;61(1):75-96
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