Research subject. The Lake Sabakty sediments core, as a source of data on the Holocene and Lateglacial environments in the Southern Urals.Aim. To obtain a multiple regression model for quantitative reconstructions of the electrical conductivity of water based on the geochemistry of lake sediments and to reconstruct the Late Glacial and Holocene environments based on the study of the Lake Sabakty geochemical record.Materials and methods. After determination of correlations between the content of chemical elements in lake sediments and hydrochemical parameters of 107 Ural lakes, multiple regression models were obtained. Reconstructions were performed based on the results obtained by accelerator mass spectrometry (AMS 14C), 210Pb activity determination, and an analysis of chemical elements and organic matter contents in the sediment core.Results. Three multiple regression models using the concentrations of Na, Ca, Li, and Sr were obtained for electrical conductivity of water reconstruction. In the cold and dry Lateglacial (>12.0 ka cal BP), Lake Sabakty was a slightly brackish reservoir. During the transition from the Lateglacial to the Holocene (12–11.6 ka cal BP), the Lake Sabakty became more productive. In the Early (11.6–8.2 ka cal BP) and Middle (8.2–4.2 ka cal BP) Holocene, the electrical conductivity of water varied under the action of fluctuations in effective moisture. In the Late Holocene (4.2 ka cal BP – present), the Lake Sabakty became less saline due to an increase in effective moisture.Conclusions. The proposed multiple regression models enable rapid quantitative reconstructions of the electrical conductivity of water, which are particularly relevant for Lateglacial–Early Holocene sediments with a low number of microfossils. The Lake Sabakty geochemical record reflects global and regional climatic fluctuations, being more informative compared to the geochemical records of forest lakes in the Southern Urals. The decrease in the electrical conductivity of water of Lake Sabakty of approximately 7.9 and 4.2 ka cal BP coincides with similar data for several other lakes in the Urals.

Research subject. Rare minerals of tin and antimony – stistaites from natural lead plates from the Severo-Svetlinskaya placer in the Chelyabinsk region and from microspherules of intermetallic compounds in the products of erosion of granites of the Kisegach complex in the Ilmeny Mountains.Materials and methods. Electron probe analysis and laser ablation with inductively coupled plasma were used to study the composition of the predominant minerals of intermetallic compounds in lead plates extracted during the washing of a gold-bearing placer, as well as from metal microspherules in the sandy fraction of eroded granites.Results. Two types of stistaite were identified: lead and arsenic-lead. Lead stistaites is sharply predominant, with its average composition (wt %) being Sb – 47.39, Sn – 38.75, Pb – 13.24, Cu – 0.06. The average composition of arsenic-lead stystaite (wt %) was found to be Sb – 43.89, Sn – 41.06, Pb – 11.02, As – 3.05, Cu – 0.47. Tin-lead microspherules from the destruction products of biotite granites of the Kisegach massif (Ilmeny Mountains) occasionally contain crystals and spotted precipitates of lead stistaite with the composition (wt %) of Sn 53.54, Sb 38.45, and Pb 7.42.Conclusions. It is assumed that, in both cases, the formation of alloys of intermetallic compounds of tin, lead and antimony with inclusions of native copper and iron was associated with granite magmatism.

The paper shows new fluid inclusion and isotopic-geochemical data for minerals from sulphide-carbonate-quartz veins of Vosnesensky Cu-porphyry deposit. Fluid inclusions were analyzed by means Linkam TMS-600 cryostage equipped with Olympus BX 51 optical microscope; trace element amounts were performed used Agilent 7700x and ELAN 9000 mass-spectrometers; sulphur isotopic composition was analyzed on DeltaPLUS Advantagе mass-spectrometer. We determined that fluid inclusions in quartz were homogenized between 215 and 315 ºС, and in latest calcite, they are 230–280 ºС. Fluids are К-Na water chloride with salinity of 3–12 wt % NaCl-eq. Quartz contain high amounts of Al (184–5180 ppm), K (20.1–1040 ppm), Na (30.2–1570 ppm) and Ti (38.4–193 ppm). The REE distribution spectra of pyrite are characterized by light lanthanides accumulation (LaN/YbN = 3.6–6.44), and negative of Ce anomalies (0.7–0.92) and Eu (0.78–0.99). The Y/ Ho ratio in pyrite varies from 27.6 up to 36.8. The δ34S values in pyrite were –1.01…0.8 ‰, in chalcopyrite – 0.9 ‰. The data testify the Cu-porphyry mineralization of Vosnesensky deposit was formed due to magmatic acid high-aluminous К-Na chloride fluid enriched with light REE in mesothermal environment. We identified the geochemical markers of interaction between fluid and host rocks.

The miarolitic dunites of the Nizhny Tagil massif (Central Urals), the structure of miaroles and the principles of co-occurrence of minerals are studied. Garnets from miaroles are characterized in details and are compared with those from chromitites and metasomatites after dunites. The structure of miarolitic dunites and miaroles is described using ontogenic approaches. The structure and composition of garnets are studied by SEM and LA-ICP-MS. Three assemblages of garnets are established in rocks of the Nizhny Tagil massif: Cr-andradite in miarolitic dunites, uvarovite in massive veined chromitites and demantoid in metasomatites after dunites. Garnets from all assemblages belong to the ugrandite group and are characterized by specifc features of chemical composition including higher Cr2O3 content. Garnets are also characterized by contrasting concentrations of trace elements, such as V, Mn and Ti, as well as differences in REE pattern. A paragenetic sequence of formation of major rock-forming minerals is suggested for dunites, chromites and metasomatites after dunites of the Nizhny Tagil massif.