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This study firstly presents chemical and initial Os-isotopic compositions of Os-Ir-Ru minerals of two ultramafic formations of Polar Siberia, which are exemplified by Guli clinopyroxene-dunite massif of the Maimecha-Kotui Province and the Kunar dunite-harzburgite massif from the Chelyuskin ultramafic belt of the Taimyr Peninsula. The study employed a range of methods, including electron microprobe analysis, negative thermal ionization mass spectrometry (N-TIMS) and laser ablation attached to an inductively coupled plasma mass spectrometry (LA MC-ICP-MS). The majority of platinum-group minerals (PGM) from the Guli massif are Os-(Ir-Ru) solid solutions or Os-rich minerals. At Kunar, minerals of Ru-Os-Ir system (i.e., osmium, ruthenium, iridium and rutheniridosmine) dominate the PGM assemblage. The ruthenium trend in the mineral compositions is due to the formation of these minerals under high pressures and temperatures at considerable depths. The Os/Os values of Os-rich minerals from the Guli massif range from 0.12309 ± 0.00002 to 0.12606 ± 0.00003 ( n = 168). The initial Os-isotopic composition of PGM from the central block of the Guli massif is characterized by the Os/Os values, varying in the range 0.12404-0.12606. Osmiumrich minerals from the southwestern block of the Guli massif are characterized by the least 'radiogenic' Os/Os values (i.e., 0.12309-0.12341). Low relative to the chondritic universal reservoir (CHUR) Os/Os values are indicative of a near-to-chondritic source of platinum-group elements (PGE). The most 'productive' stage of PGM formation at Guli ( n = 121) is recorded in the time interval of 545-615 Ma. The older model Os/Os ages of osmium minerals are characteristic of the southwestern block of the Guli massif (e.g., 745-760 Ma). The results of the initial Os-isotopic composition for Os-rich alloys are consistent with a model, in which PGM were formed during multi-stage melt depletion events in the mantle. This agrees well with the suggestion that the Guli massif consists of heterogeneous blocks of ultramafic rocks. The Os/Os ratio in the investigated PGM from the Kunar massif varies in a wider range (0.1094-0.1241, n = 28). For the dominant set of PGM samples ( n = 25), regardless of their chemical composition, four groups of the initial osmium isotopic compositions can be estimated, with average Os/Os values of 0.1217 ± 0.0002 ( n = 7), 0.1223 ± 0.0002 ( n = 7), 0.1230 ± 0.0002 ( n = 6) and 0.1238 ± 0.0003 ( n = 6), respectively. The average model Re-Os ages for the defined groups of the Kunar massif are consistent with Late Riphean age interval (e.g., 975 ± 42 Ma, 892 ± 42 Ma, 791 ± 28 Ma and 681 ± 42 Ma, respectively). Significant variations in the Os/Os values and model ages for Ru-Os-Ir alloys at Kunar are close to those from other duniteharzburgite massifs of the Earth, pointing out for their prolonged multi-stage evolution within the upper mantle. [ABSTRACT FROM AUTHOR]

The article reports that mishandling of the used fuel at the Mayak nuclear facility in Ozyorsk in Russia have caused the spread of isotope ruthenium-106 in Europe, according to the scientists from the French Institute of Radioprotection and Nuclear Security (IRSN). Topics include the analysis and interpretation of the computer model base from air-sampling and weather data, the issue of mishap nuclear reactor which resulted to radioactive pollutants, and the experiment on the sterile neutrino.