Research subject. The distribution regularities of Al and Li impurities in gold-ore quartz. Materials and methods. The quartz of the Darasun, Teremkinskoye and Talatuy gold deposits of the Darasun ore field was studied. The gross contents of Al and Li impurities in quartz were determined by the LA-ICP-MS method; substitutional Al impurity concentrations were studied by the EPR method. The forms of Al impurity in quartz were determined based on the results of studying its behavior during material recrystallization. The genetic significance of Al and Li impurities in quartz was estimated taking into account the genetic information obtained during the study of the distribution of substitutional Al and Ti impurity concentrations. Results. It was found that Al is present in quartz in two main forms, i. e., as a substitutional Al impurity and Al complexes localized in the areas of high mineral defectiveness. Li+ ions are located in the structural channels of the mineral, serving as compensating ions for both Al impurity forms. The composition of Al complexes is assumed to include three Al 3+ ions and one H + or Li + ion. Two stages of quartz recrystallization occurring at different temperatures of mineral formation were identified. The first, low-temperature stage leads to quartz enrichment with substitutional Al impurities. The second, high-temperature stage causes the decomposition of Al complexes. The recrystallization stages can be identified by the type of relationship between the gross concentrations of Al and Li. The increased content of Al impurity in ore quartz was found to be related to the presence of a large number of Al complexes. An assumption is made that these complexes formed during mineral crystallization from solutions with a high content of metal ions. Conclusions. The results obtained indicate that high Al impurity concentrations can serve as a genetic sign of ore quartz. At the same time, the decomposition of Al complexes during quartz recrystallization should be taken into account. A method for estimating the initial concentration of Al complexes is proposed, which is a more reliable genetic indicator.

Quartz samples taken from the ore veins of the Darasun gold deposit (Eastern Transbaikalia, Russia) were studied using electron paramagnetic resonance (EPR) and laser ablation (LA) methods. The purpose of the research was to clarify the behavior of the Al impurity during quartz crystallization and its subsequent recrystallization. The results of the research were used to determine the genetic informativeness of the Al impurities concentration in ore quartz. A separate study of the regularities of the distribution of Al impurity in the regions of crystalline structure and in the zones of crystal lattice distortions was carried out. In the regions of crystalline structure, the Al impurity concentration NAL was determined by the concentration of paramagnetic Al–O–-centers associated with the presence of substitutional Al3+ ions. The content of the Al impurity in the zones of crystal lattice distortions was judged by the difference between the gross concentrations of aluminum CAl and the values of NAL. It was taken into account that the intensity and direction of the studied processes can be influenced by the temperature of quartz formation and the degree of its recrystallization. The temperature of quartz formation was estimated by the values of Ti impurity concentration, and the degree of recrystallization was estimated by the content of Li impurity CLi in the mineral. It was found that the amount of Al impurity localized in the zones of crystal lattice distortions is an order of magnitude higher than that present in the zones of crystalline structure. It is shown that this phenomenon is explained by the high ability of the zones of crystal lattice distortions to capture of Al impurity during quartz crystallization. The amount of Al impurity trapped by quartz increases sharply with an increase in the temperature of the mineral formation. In areas of regions of crystalline structure, a different picture is observed − impurity capture during crystallization proceeds with low intensity and is not so critically dependent on temperature. It was found that the Al impurity in the considered zones behaves differently during quartz recrystallization. If Al impurity capture continues in the regions of crystalline structure, then Al impurity removal from quartz can occur in the zones of crystal lattice distortions at high CAl values. Based on the data obtained, the areas of use of aluminum impurity contents as a typomorphic feature of ore quartz were determined. The Al impurity concentrations proved to be suitable for use in cases of low ore formation temperatures, and its gross CAl contents have the prospect of wider use. It is noted that a characteristic feature for quartz from high productivity zones is a negative angle of slope of the CAl(CLi) dependence plot.

Труды Ферсмановской научной сессии ГИ

Abstract—For the first time, EPMA and LA-ICP-MS data were obtained for the Kyuchus Au–As–Sb–Hg deposit on variations in the grades and zonal distribution of gold and other impurity elements in gold-bearing sulfides of disseminated ores. Two types of zoning have been found in pyrite: (1) zoning with the central zone depleted in impurities bearing As (1.5–1.9 wt

The study reports petrography, mineralogy and carbonate geochemistry and stable isotopy of various types of ocelli (silicate-carbonate globules) observed in the lamprophyres from the Chadobets Uplift, southwestern Siberian craton. The Chadobets lamprophyres are related to the REE-bearing Chuktukon carbonatites. On the basis of their morphology, mineralogy and relation with the surrounding groundmass, we distinguish three types of ocelli: carbonate-silicate, containing carbonate, scapolite, sodalite, potassium feldspar, albite, apatite and minor quartz ocelli (K-Na-CSO); carbonate–silicate ocelli, containing natrolite and sodalite (Na-CSO); and silicate-carbonate, containing potassium feldspar and phlogopite (K-SCO). The K-Na-CSO present in the most evolved damtjernite with irregular and polygonal patches was distributed within the groundmass; the patches consist of minerals identical to minerals in ocelli. Carbonate in the K-Na-CSO are calcite, Fe-dolomite and ankerite with high Sr concentration and igneous-type REE patterns. The Na-CSO present in Na-rich damtjernite with geochemical signature indicates the loss of the carbonate component. Carbonate phases are calcite and Fe-dolomite, and they depleted in LREE. The K-SCO was present in the K-rich least-evolved damtjernite. Calcite in the K-SCO has the highest Ba and the lowest Sr concentration and U-shaped REE pattern. The textural, mineralogical and geochemical features of the ocelli and their host rock can be interpreted as follows: (i) the K-Na-CSO are droplets of an alkali–carbonate melt that separated from residual alkali and carbonate-rich melt in highly evolved damtjernite; (ii) the Na-CSO are droplets of late magmatic fluid that once exsolved from a melt and then began to dissolve; (iii) the K-SCO are bubbles of K-P-CO2 fluid liberated from an almost-crystallised magma during the magmatic–hydrothermal stage. The geochemical signature of the K-SCO carbonate shows that the late fluid could leach REE from the host lamprophyre and provide for REE mobility.

Xenoliths from the Mir pipe and from Shandong and Liaoning provinces were studied according to electron microbeam analysis and ICP-MS. Their mineralogical, geochemical and genetic features are revealed. Minerals of diamondiferous paragenesis were established in xenoliths of the Mir pipe, but not in xenoliths of China. All xenoliths have secondary changes. They are stronger in the xenoliths of China. The distribution of REE shows the involvement of subduction processes in the formation of xenoliths from the Mir pipe. They are not found in xenoliths from China; the influence of metasomatism is clearly manifested in them. РТparameters were calculated: Т=600700 °С, Р=22,5 GPa. They do not correspond to mantle settings and reflect the conditions of metasomatic processes.

Xenoliths from the Mir pipe and from the Shandong and Liaoning provinces were studied by the methods of EMPA and ICP-MS. Their mineralogical, geochemical, and genetic features were revealed. Minerals of diamondiferous paragenesis were detected in xenoliths from the Mir pipe, while they were not found in xenoliths of China. All xenoliths are characterized by secondary alterations, which are more intense in xenoliths of China. The distribution of REEs shows the involvement of subduction processes in the formation of xenoliths from the Mir pipe. The influence of metasomatism is clearly evident in xenoliths from China. The calculated P–T parameters (Т = 600–700°C, P = 2–2.5 GPa) are not consistent with the mantle environments that correspond to the metasomatic conditions.

This study discusses the presentation of rare-earth elements (REEs) in the rocks of the Kivakka Olivinite-Gabbronorite Layered Intrusion in North Karelia. It aimed to provide a detailed petrographic description of the mineral parageneses that are present in the studied section of the massif. We found that the same minerals can manifest in both intercumulative and cumulative positions, depending on the degree of melt fractionation. At the same time, their quantity, which determines both the petrographic characteristics and the name of the rock, is not a criterion for their presence during the cumulus phases. We analyzed the concentrations of REEs in rocks and rock-forming minerals in the Kivakka massif, considering the REE concentration vertically and in the critical zones of contrast interbedding. In the study area, REEs are present as incoherent elements and accumulate in the residual melt, together with U, Th, Zr, and other incoherent elements, which make them a useful indicator of the degree of melt fractionation. In some cases, they can reflect different structural and genetic characteristics, such as the degree of cumulus density in a specific type of cumulative paragenesis. The presence of hydrothermal changes is best reflected by a change in Ce concentration. The preservation of the stability of the configuration and the slopes of the lines on the spider diagrams for REE indicate that the process of crystallization differentiation took place in a closed system.

Работа посвящена исследованию поведения редкоземельных элементов в породах Киваккского оливинит-габбро-норитового расслоенного интрузива (Северная Карелия). В статье приведена подробная петрографическая характеристика минеральных парагенезисов, слагающих разрез массива. Показано, что одни и те же минералы в породах могут занимать либо интеркумулятивную, либо кумулятивную позицию в зависимости от степени фракционирования расплава. При этом их количество, определяющее петрографические характеристики и название породы, не является критерием их присутствия в ассоциации кумулусных фаз (кумулятивной фазе). Представлены результаты анализа концентрации редкоземельных элементов в породах и породо­образующих минералах массива. Рассмотрено изменение концентрации РЗЭ в вертикальном разрезе, а также в критических зонах контрастного переслаивания. Показано, что в Киваккском массиве РЗЭ являются некогерентными элементами и накапливаются в остаточном расплаве совместно с U, Th, Zr и другими некогерентными элементами, что позволяет считать их индикатором степени фракционирования расплава. В некоторых случаях они могут отражать различные структурно-генетические особенности, такие как степень плотности кумулуса в однотипных кумулятивных парагенезисах. Наличие гидротермальных изменений наилучшим образом отражается в изменении концентрации Ce. Сохранение стабильности конфигурации и угла наклона линий на спайдер-диаграммах для РЗЭ свидетельствует о закрытости системы в процессе кристаллизационной дифференциации массива.

Рассмотрены первые результаты изучения (методы минераграфии, катодолюминесценции (CL), рентгеноспектрального микроанализа (EPMA) и масс-спектрометрии с индуктивно-связанной плазмой и лазерным пробоотбором (LA-ICPMS)) шеелита из кварц-молибденитовой и кварц-карбонат-сульфидной жильно-прожилковой (порфировый тип), а также кварц-магнетит-сульфидной гнездово-вкрапленной (скарновый тип) минерализаций скарново-порфирового Cu-Au-Fe-месторождения Быстринское (Восточное Забайкалье) – одного из наиболее крупных золотомедных порфировых объектов России. Установлено, что шеелит, не являясь главным минералом руд месторождения, встречается практически повсеместно, что дает возможность выявлять его ключевые признаки, отражающие специфику генезиса, как разнотипной минерализации, так и месторождения в целом. Показано, что шеелит из разных типов рудной минерализации обладает четко детерминированными индивидуальными характеристиками, отчетливо различаясь распространенностью, ансамблями ассоциированных минералов, цветом катодолюминесценции и флуоресценции в УФ-свете, составом и концентрациями макро- и микроэлементов, а также характером спектров РЗЭ. Эти отличительные особенности свидетельствуют о существенном несходстве условий формирования изученных типов руд и обнаруживают зависимость от физико-химических и композиционных параметров минералообразующей среды, что позволяет рассматривать шеелит как принципиально важный генетический индикатор эволюции обстановок минералообразования. Ключевое значение при этом имеют концентрации в шеелите Mo, тип и форма РЗЭ-спектров, которые в целом определяются как унаследованием химизма минералообразующих флюидов и особенностями изоморфного вхождения РЗЭ в структуру минерала, так и вариациями окислительно-восстановительных свойств минералообразующего флюида.

The first results of the study (methods of mineragraphy, cathodoluminescence (CL), electron-probe microanalysis (EPMA) and laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICPMS)) of scheelite from quartz-molybdenite and quartz-carbonate-sulfide vein-veinlet (porphyry type) are considered, as well as the magnetite-sulfide massive, veinlets and disseminated (skarn type) mineralization of the skarn-porphyry Cu-Au-Fe deposit of Bystrinskoye (East Transbaikalia) one of the largest gold-copper porphyry ore-fields in Russia. It has been established that scheelite, being not the main mineral of the deposit ores, is found almost everywhere, which makes it possible to identify its key features reflecting the specific features of the genesis, both of different types of mineralization and the deposit as a whole. It is shown that scheelite from different types of ore mineralization has clearly determined individual characteristics, differing in prevalence, ensembles of associated minerals, color of CL and fluorescence in the UV-light, composition and concentrations of macro- and microelements, as well as the nature of REE-spectra. These distinctive features testify to a significant difference in the conditions for the formation of the studied ore types and reveal the dependence on the physicochemical and compositional parameters of the mineral-forming medium, which makes it possible to consider scheelite as a fundamentally important genetic indicator of the evolution of mineral formation patterns. Concentrations of Mo in scheelite, the type and form of REE-spectra, which are generally, determined both by the inheritance of the mineral-forming fluid chemistry and the peculiarities of isomorphic occurrence of REE in the structure of the mineral, and variations in the redox properties of the mineral-forming fluid, are of key importance.

Abstract—This work is devoted to the examination of REE behavior in rocks of the Kivakka olivinite–gabbronorite layered intrusion (Northern Karelia). The paper reports detailed petrographic characteristics of mineral assemblages throughout the massif section. It is shown that the same minerals are present as both intercumulus and cumulus phases depending on the degree of melt fractionation. Their contents which determine the petrographic characteristics and rock name are not indicative of their presence in cumulate assemblage (cumulus phase). REE contents in rocks and rock-forming minerals are analyzed, including their variations in the vertical section as well as in the critical zones of contrasting intercalation. REE in the Kivakka massif behave as incompatible elements, are accumulated in a residual melt together with U, Th, Zr, and other incompatible elements, and can be used as indicator of the degree of melt fractionation. In some cases, they could reflect different structural–genetic features such as the cumulus density in the similar cumulus assemblages. Hydrothermal alteration strongly affects the Ce content. The similar shape of REE patterns indicates the close-system crystallization differentiation of the massif.

Zoned scheelite crystals from the Yubileinoe porphyry gold deposit were studied by EMPA and LA-ICP-MS. The MoO3 content decreases from 10–13 wt % in the crystal center to less than 2 wt % in the rim. Scheelite is enriched in LREE with respect to HREE and has negative Eu and Ce anomalies. Early scheelite has a flat REE distribution pattern with a negative slope, while the latter has asymmetrical convex REE spectra due to the lower La content and higher Nd, Sm, and Gd concentrations. The REE distribution in early scheelite has been established as inherited from ore-bearing granitic rocks, while this distribution in later generations of the mineral was determined by hydrothermal fluid.

The distribution of REEs and some minor elements in tourmalines of different associations and deposits of the Russian Far East is studied by the methods of ICP-MS, ICP-MS with laser ablation and scanning electron microscopy. The duality of REE speciation in tourmaline is established: in high-temperature varieties, most REEs (mainly HREEs) are incorporated in rare minerals (monazite, xenotime, zircon, and F–Ce–Y carbonate), whereas hydrothermal ores are characterized by isomorphic incorporation of LREEs in the mineral structure, as well as by a fine admixture of zircon at the expense of detrital clasts in flyschoid rocks with the zones of tourmalinization.