Rare-Earth Elements from Modern Mineral–Organic Associations in the Zone of Sulfide Ore Hypergenesis

The REE composition of modern mineral–organic associations in the sulfide ore hypergenesis zone of the Berezitovoe deposit in the Russian Far East was studied for the first time. It is shown that the mineral–organic associations widely abundant in the valley of Konstantinovskii Creek and represented by bright brown crusts on the surface of deluvial deposits were formed at the expense of the influence of acid highly mineralized mine waters from the Berezitovoe deposit. The mineral–organic associations found in the Creek valley may be considered as a new indicator for evaluation of the geoecological state of modern technogenic landscapes.     

High-alumina titanite in mineral assemblages of the Berezitovy gold-base-metal deposit, Upper Amur Region

Grothite—a rare Al- and F-rich variety of titanite—was identified in two different gold-bearing mineral assemblages of the Berezitovy gold-base-metal deposit, Upper Amur Region, Russian Far East. Grothite is associated with quartz, orthoclase, chlorite, muscovite, tourmaline, almandine-spessartine garnet, ilmenite, pyrophanite, magnetite, fluorapatite, and sulfides. Grothite forms numerous scattered lamellar aggregates 20–100 μm in size with a relatively homogeneous structure. The lamellae grow in chlorite or between chlorite and orthoclase. According to microprobe analyses, variations in major elements of grothite are as follows (wt %): 30.56–34.07 SiO₂, 7.91–12.71 Al₂O₃, 22.83–28.29 TiO₂, 23.55–29.21 CaO, 0.52–4.25 FeO, and 2.19–6.16 F. It is suggested that grothite appeared in the gold-bearing mineral assemblages of the Berezitovy deposit due to the specifics of the primary composition of the host rocks and physicochemical conditions of the fluid regime at the final stage of deposit formation.     

Physicochemical crystallization conditions of Al-F sphene in metasomatic rocks with ore mineralization at the Berezitovoe Deposit

Al-F sphene (grothite) was found in mineralized rocks at the Berezitovoe Deposit in the Russian Far East. The paper is devoted to the mineral assemblages and composition of the mineral and its thermodynamic crystallization conditions. The average Al and F concentrations (p.f.u., microprobe data) in the grothite are 0.45 and 0.42 in sample 1374, 0.32 and 0.32 in sample 1306, and 0.35 and 0.33 in sample 96. Grothite was found in the rocks in association with chlorite, ilmenite (pyrophanite), and magnetite, and this mineral assemblage was obviously overprinted on the primary garnet-biotite assemblages. We estimated the temperature of grothite crystallization at 400–500°C. With regard for available experimental data on the mineral equilibrium between Al-F sphene, fluid, and anorthite, a tool is proposed for evaluating F concentrations in fluids by the equilibrium of Al-F sphene with plagioclase, rutile, and F-bearing aqueous fluid. Our model simulations indicate that the maximum F concentration in fluid during the crystallization of Al-F sphene richest in F at the temperatures and pressures of metasomatic rocks at the Berezitovoe deposit could reach 300–500 mg per kg of the aqueous solution. The level of F concentration in the fluid during the crystallization of Al-F sphene at the deposit is comparable with the F concentration in fluid during the development of greisens and rare-metal pegmatites, but these high F concentrations were reached only during the final evolutionary stages of the deposit.     

Geochemistry of carbonated mineral waters from the Fadeevskoe deposit of the Primorye region

The geochemical study of bed rocks, underground and surface waters, and associated gases in the Fadeevskoe deposit of carbonated waters (Sikhote Alin, Primorye region) revealed that the chemical composition of these waters is formed in the zone of active water exchange in the limited area of the discharge zone, where hydro carbonate calcic waters with mineralization of up to 1 g/1 are formed in largely potassic-sodic rocks. Calculations of the saturation indices show that the mineral waters are characterized by the early stage of Ca saturation, being undersaturated with carbonates and aluminosilicates. The main factors that influence the water mineralization are the excess carbon dioxide in water and the circulation time. The oxygen and carbon isotope ratios indicate the atmospheric genesis of the aqueous component (δ²H = —117; δ¹⁸O = —15.4%o) and the carbon isotope content in the CO₂ implies the mantle nature of the carbon dioxide (δ¹³C = -9.9%o).     

Malinovka deposit—A new type of gold mineralization in Primorye,Russia: Geology,mineralogy, and genesis

Original data on the ore composition are obtained by studying samples from mining workings. In terms of mineral composition, gold-productive veinlets are subdivided into three types: sulfide–quartz, sulfide–carbonate–quartz, and sulfide. The wall-rock metasomatites and typomorphic features of the minerals are studied and the genetic problems of the ores and deposit are discussed. It is established that the Malinovka deposit is ascribed to the gold–tourmaline type (gold–quartz formation), which is identified for the first time in Primorye. In terms of many parameters, the ores of this type are close to those of the large deposits from the Transbaikalian and Amur regions (Klyuchevsky, Kariy, Kirov, Darasun, and others), which are genetically related to granitoid magmatism.     

Excess of Rare-Earth Elements in Plant Foods as a Cause of Geophagy among Ungulates in Gornyi Altai

Doklady Earth Sciences - Geological and hydrobiogeochemical studies carried out in two areas of active geophagy among herbivorous animals in the area of Teletskoye Lake in the Altai Mountains...     

U-Pb isotopic geochronologic investigations of zircons from granites and ore-bearing metasomatites of the Berezitiovoe gold-polymetallic deposit (Upper Amur region)

The results of the U-Pb geochronologic studies of zircons from the ore-bearing metasomatites of the Berezitovoe deposit in the Upper Amur region and the porphyroid biotite-hornblende host granites of the Khaikta-Orogzhan massif, which were previously considered as Early Proterozoic magmatic formations of the Late Stanovoi Complex, are examined. The SHRIMP-II and LA-ICP-MS methods were used for this purpose. It was revealed that the mass spectrometer method coupled with a laser ablation system yields precise U-Pb rock dating, and its results are comparable with the data obtained by the SHRIMP-II method. The weighted average isotopic ages are 344–355 and 323–366 Ma as established for the zircons from the porphyroid granites of the Khaikta-Orogzhan massif and from the ore-bearing metasomatites of the Berezitovoe gold-polymetallic deposit, respectively. The data definitely indicate that the metasomatites were developed after the granitoids of the Khaikta-Orogzhan massif and belong most likely to an autonomous Late Paleozoic magmatic complex. Coeval Paleozoic magmatic complexes are widespread within the Selenga-Stanovoi superterrane in the eastern and western Transbaikal regions.     

Aluminum-fluorine sphene (Titanite) as an indicator of fluorine fluid

Doklady Earth Sciences -