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The possibility of applying a combined concentration and metallurgical method for processing low-grade and refractory copper–nickel ores was considered. The resulting rougher and scavenger flotation concentrate contained 2.07% nickel and 0.881% copper at a recovery of 85.44% and 89.91%, respectively. The concentrate was then roasted with ammonium sulfate, followed by aqueous leaching of clinker to dissolve nickel and copper. The roasting temperature, the ratio of concentrate to (NH4)2SO4 in the mixture, and the temperature were varied. Based on the study findings, the following process conditions were found to be optimal: roasting temperature 400 °С, rougher concentrate to ammonium sulfate ratio 1:7, and grinding size −40 μm. A roasting temperature of 400 °C is significantly lower than the temperature applied in conventional pyrometallurgical processes. The possibility of collecting off-gases allows the reagent to be regenerated and makes the process even more cost-effective. End-to-end recovery into pregnant solution was 81.42% for nickel and 82.81% for copper. The resulting solutions can be processed by known hydrometallurgical methods.

A gusher from accident well 37 at the Tengiz oilfield (Kazakhstan) led to a catastrophic fire and produced melt combustion metamorphic rocks in its thermal halo (aureole). According to the obtained data on the mineralogy and petrology of the combustion metamorphic rocks and inferred thermal conditions of metamorphism, the protolith sand and clay can become fully molten at a temperature no lower than 1200 C. Four models have been tested for the thermal effect of the Tengiz fire on the country rocks: (a) a single straight-flow vertical gas flare, (b) a single vertical gas flare with oil droplets, (c) a single oil-gas flare with lateral wind load, and (d) a composite oil-gas flare consisting of one vertical and two horizontal spouts. Modeling with SigmaFlow software takes into account the spatial turbulent airflow mechanics of the flare, convective, and radiative heat transfer, burning of gas and oil droplets, as well as conductive heat flux in soil. Model 4 simulates the best the Tengiz fire in the period from 26 June 1985 to 05 September 1986. As the model predicts, a flare with the parameters as in the Tengiz case can cause partial melting of sedimentary material (1100 C) in a local zone but cannot maintain its bulk melting which requires higher temperatures (1200-1400 C). Additional heat may have come from ignition of oil spilled over the surface. The heat from a single oil-gas flare from a wellhead with a 0.5-m stickup turns out to be insufficient for combustion metamorphism (T ¼ 1000-1400 C).

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The relevance of the work is conditioned by the need for a comprehensive study of the mineralogical and microbiological parameters of the Shulgan-Tash (Kapova) cave, which is an archeological monument of universal importance. The purpose of the work: to describe findings of subaquatic stalactites in the Shulgan-Tash cave and to solve mineralogical and genetic issues. Research methodology: hydrochemical, electron microscopic and microbiological techniques of research were used in the present work. Results. This article describes subaqueous stalactoids for the first time in Russia. In the foreign literature they are called "Pool Fingers". They are the carbonate forming with the origin, which is not yet definitely installed. They are emerging in the coastal zones of the cave waters. Subaqueous stalactoids were found in the Dal'nee Verkhnee lake on the second floor of the Shulgan-Tash cave 700 meters from the entrance. Subaqueous stalactoids are widespread along the Eastern and Western shores of the lake. They are thin and elongated aggregates of cream-colored up to a length of 30 cm, composed of calcite. They were formed in the lake of calcium bicarbonate type water with total mineralization of 390-510 mg/l, their hydrogen index is close to neutral (pH 6.8-7.3) and minor (not more than 5 mg/l) magnesium, sulfates and chlorides. Stalactitical surfaces are covered with the biofilm of the extracellular polymeric substances (EPS) and microorganisms. In their environment, the crystallization of calcite takes place. The "filaments", whose taxonomic affiliation is not clear are found inside the units in the flattened strands of biological origin. Calcite is a block crystal subindividuals, which possess the elements of splitting. Their size is about 200-300 µm. The manifestation of skeletal crystal growth happens rather often. Researches prove the participation of microorganisms in the origin of subaqueous stalactoids. Apparently, filamentous bacterial mats play the role of the primers and a "framework", which provides a gravity-oriented growth of the aggregates. Extracellular polymeric substance (EPS) has the ability to form complex compounds with ions of Ca 2+ . It may indirectly lead to the precipitation of calcite. Conclusions. The microbial mediated genesis, similar to that described in the literature of the North American counterparts, was substantiated for the subaqueous stalactoids (Pool Fingers).Keywords: subaqueous stalactoids, Pool Fingers, secondary mineral formation, the carbonates, the calcite skeletal crystals, bacteria, Shulgan-Tash cave. IntroductionThe relevance and purpose of the work The subject of our research is the microclimate and gas composition of the atmosphere [1, 2]. The subject consequently includes modern mineral formation, the study of rare mineral species [3], and the isotopic Geochemistry of elements in the minerals of caves. One of the objects of our research is the cave Shulgan-Tash in Bashkortostan. It is famous for its Paleolithic paintings. To preserve them, the monitoring and study o...