Genesis of precious metal mineralization in intrusions of ultramafic, alkaline rocks and carbonatites in the north of the Siberian platform

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200◦C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested

Ore-forming Сonditions of the Blagodat Gold Deposit in the Riphean Metamorphic Rocks of the Yenisey Ridge According to Geochemical and Isotopic Data

Neodymium and strontium isotopic composition and rare earth elements (REE) distribution pattern have been determined in whole rocks and minerals were separated from host metamorphic rocks and disseminated sulfide ores of the Blagodat gold deposit. Isotopic data are given to construct few isochrones that could be reflected an age of main stages of metamorphic and metasomatic alteration in rocks varieties during a successive accumulation of gold in structural traps. The significant temporal range in the forming of the studied rocks can be interpreted as an evidence of multi-stage tectonic destruction accompanying with trust-folding processes, shear deformations and development of local fracture zones that had place from the Late Riphean to Middle Paleozoic time. According to isotopic data basic ore-forming processes were realized in the relatively narrow interval from 690 to 750 Ma that correspond to a beginning of continental rifting on the western margin of Siberian craton. Chemistry and trace element distribution are closed for host and auriferous schists and mainly showed differences in the composition initial sedimentary units. The middle negative value εNd (from -14 to -16) and very high positive value εSr (from +570 to +725) are mostly corresponded to that of upper continental crust matter. The role of synchronic granite intrusions in the studied area can be only estimated due to a generation of thermal energy and crustal fluids

Composition and Ligand Microstructure of Arsenopyrite from Gold Ore Deposits of the Yenisei Ridge (Eastern Siberia, Russia)

The Mössbauer spectroscopy method was used to study the ligand microstructure of natural arsenopyrite (31 specimens) from the ores of the major gold deposits of the Yenisei Ridge (Eastern Siberia, Russia). Arsenopyrite and native gold are paragenetic minerals in the ore; meanwhile, arsenopyrite is frequently a gold carrier. We detected iron positions with variable distribution of sulfur and arsenic anions at the vertexes of the coordination octahedron {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, {6As} in the mineral structure. Iron atoms with reduced local symmetry in tetrahedral cavities, as well as iron in the high-spin condition with a high local symmetry of the first coordination sphere, were identified. The configuration {3S3As} typical for the stoichiometric arsenopyrite is the most occupied. The occupation degree of other configurations is not subordinated to the statistic distribution and varies within a wide range. The presence of configurations {6S}, {3S3As}, {6As} and their variable occupation degree indicate that natural arsenopyrites are solid pyrite {6S}, arsenopyrite {3S3As}, and loellingite {6As} solutions, with the thermodynamic preference to the formation of configurations in the arsenopyrite–pyrite–loellingite order. It is assumed that in the variations as part of the coordination octahedron, the iron output to the tetrahedral positions and the presence of high-spin Fe cations depend on the physical and chemical conditions of the mineral formation. It was identified that the increased gold concentrations are typical for arsenopyrites with an elevated content of sulfur or arsenic and correlate with the increase of the occupation degree of configurations {5S1As}, {4S2As}, {1S5As}, reduction of the share of {3S3As}, and the amount of iron in tetrahedral cavities

Pilot Study of Isothermal Crystallization of Goethite from Metastable Synthetic Pyrrhotite

В синтезированных пирротинах после выдержки в атмосфере Земли в течение 29 лет при температуре ~20 ºС исследовались методами рентгеноструктурного анализа кристаллическая структура и фазовый состав образцов. Установлено, что они содержат гетит, который отсутствовал в исходных образцах. Это свидетельствует о том, что гетит образовался из пирротина, находящегося в метастабильном фазовом состоянии. В зависимости от соотношения серы и железа в образцах исследована закономерность образования гетита. Построена диаграмма соотношения фаз гетит - троилит. В статье предложена теоретическая модель фазового перехода пирротина в гетит. Получено хорошее соответствие расчетной кривой диаграммы фазового соотношения гетит - троилит с экспериментальной. Расчеты, осуществленные в рамках предложенной модели вторичного квантования, хорошо согласуются с аналогичными расчетами, проведенными в рамках модели молекулярного поля.The crystal structure and the phase composition of synthesized pyrrhotite after its endurance in the atmosphere of the Earth for 29 years at temperature about 20ºС have been studied using the methods of X-ray structural analysis. Pyrrhotite contained goethite which was absent in initial samples. The analysis of the experimental facts allows to assume that goethite originated from pyrrhotite in a metastable phase. The regularity of goethite formation depending on the percentage of troilite and also on the sulphur and iron ratio in samples has been investigated. The diagram of goethite - troilite phase ratio has been constructed. The theoretical model of phase transition of pyrrhotite into goethite is offered. Good conformity of the calculated curve of the goethite - troilite phase ratio diagram with the experimental one has been obtained. The calculations done in the offered model of secondary quantization cohere well enough with the similar calculations done within the model of a molecular field

Features of a Geological Structure and Localization of ore of the Deposit of Gerfed

В статье приводятся сведения о геологическом строении месторождения «Герфед» (Енисейский кряж). Описана морфометрическая характеристика и представлены условия формирования пород, вмещающих золотое оруденение. Рассмотрены геологические закономерности распределения золота внутри рудных зонThe article deals with the geological structure of the Gerfed deposit (Yenisey Ridge). The geomorphological characteristic and conditions of formation of the breeds containing gold ore is described. Geological regularities of distribution of gold in ore zones are considere

Analysis of the Reserves Estimation Results for the Gerfed Gold Deposit

В статье приводятся сведения о геологическом строении, технологических типах руд месторождения «Герфед» в Красноярском крае. Изложены основные аспекты методики геологоразведочных работ и результаты оценки запасов за более чем 120-летнюю историю геологического изучения месторождения. Исследована экономическая эффективность выполненных геологоразведочных работ методом приведения их стоимости в цены 2011–2012 гг., рассчитаны удельные затраты. Проанализирована динамика оценки запасов по периодамThe article deals with the geology and metallurgic ore types of the Gerfed gold deposit in the Krasnoyarsk Territory. The main aspects of the geological exploration and results of reserves estimation for a 120-year period of the deposit geological study are given. The economic efficiency of the geological exploration performed has been studied using the method of brining the costs of works in compliance with the current prices of 2011-2012. We have also calculated specific costs and have analyzed the dynamics of the reserves estimation by period

Features of a Geological Structure and Localization of ore of the Deposit of Gerfed

В статье приводятся сведения о геологическом строении месторождения «Герфед» (Енисейский кряж). Описана морфометрическая характеристика и представлены условия формирования пород, вмещающих золотое оруденение. Рассмотрены геологические закономерности распределения золота внутри рудных зонThe article deals with the geological structure of the Gerfed deposit (Yenisey Ridge). The geomorphological characteristic and conditions of formation of the breeds containing gold ore is described. Geological regularities of distribution of gold in ore zones are considere

Analysis of the Reserves Estimation Results for the Gerfed Gold Deposit

В статье приводятся сведения о геологическом строении, технологических типах руд месторождения «Герфед» в Красноярском крае. Изложены основные аспекты методики геологоразведочных работ и результаты оценки запасов за более чем 120-летнюю историю геологического изучения месторождения. Исследована экономическая эффективность выполненных геологоразведочных работ методом приведения их стоимости в цены 2011–2012 гг., рассчитаны удельные затраты. Проанализирована динамика оценки запасов по периодамThe article deals with the geology and metallurgic ore types of the Gerfed gold deposit in the Krasnoyarsk Territory. The main aspects of the geological exploration and results of reserves estimation for a 120-year period of the deposit geological study are given. The economic efficiency of the geological exploration performed has been studied using the method of brining the costs of works in compliance with the current prices of 2011-2012. We have also calculated specific costs and have analyzed the dynamics of the reserves estimation by period

Isothermal Crystallization of Szomolnokit from Metastable Synthetic Pyrrhotites

Методами рентгеноструктурного анализа исследована кристаллическая структура и фазовый состав синтезированных пирротинов после выдержки их в атмосфере Земли в течение 29 лет при температуре ~20 ºС. Образцы содержали самольнокит, который отсутствовал в исходных образцах. Анализ экспериментальных фактов позволяет предположить, что самольнокит образовался из пирротина, находящегося в метастабильном фазовом состоянии. Выявлена закономерность образования самольнокита в зависимости от процентного содержания пирротина, а также от соотношения серы и железа в образцах. Построена диаграмма фазового соотношения самольнокит - пирротин. Предложена теоретическая модель фазового перехода пирротина в самольнокит. В результате квантово-механических вычислений получено хорошее соответствие расчетной кривой диаграммы фазового соотношения самольнокит - пирротин с экспериментальной. Расчеты, осуществленные в предложенной модели вторичного квантования, хорошо согласуются с аналогичными расчетами, проведенными в рамках модели молекулярного поля.The crystal structure and the phase composition of synthesized pyrrhotites after their endurance in the atmosphere of the Earth for 29 years at the temperature about 20ºС have been studied using the methods of X-ray structural analysis. Samples contain szomolnokit which was absent in initial samples. The analysis of experimental facts allows assuming that szomolnokit was formed from pyrrhotites in a metastable phase. The regularity of szomolnokit formation depending on the percentage of pyrrhotites and also on the sulfur to iron ratio in samples has been investigated. The diagram of pyrrhotites - szomolnokit phase ratio has been built. The theoretical model of phase pyrrhotite transition into szomolnokit is offered. As the result of quantum-mechanical calculations good conformity of the calculated diagram of pyrrhotite - szomolnokit phase ratio curve with the experimental one has been obtained. The calculations performed in the offered model of secondary quantization cohere well with similar calculations done within the model of a molecular field

Magnetization of a Pyrrhotite of Composition Fe_0.847S in Area of a Curie Point

Проведены рентгеновские, мессбауэровские и термомагнитные исследования пирротинов, обладающих высокотемпературным λ-пиком (Тλ = 310 °С) на кривой зависимости намагниченности от температуры – I (Т). Определен химический состав и условия образования таких пирротинов. Установлено, что образцы с λ-пиком обладали повышенным содержанием серы по сравнению с пирротинами Fe7S8 и соответствовали составу Fe1-nS (n=0.153). Как показал эксперимент, эти пирротины находятся в метастабильном фазовом состоянии и со временем (образцы наблюдались в течение 29 лет) переходят в пирит и пирротин состава Fe7S8 (в присутствии атмосферы образовывался также гетит и самольнокит). В результате квантово-механических вычислений зависимости удельной намагниченности от температурыдля различных подрешеток с различным интегралом обменного взаимодействия получено хорошее соответствие расчетной кривой с экспериментальной. Расчеты производились в рамках модели молекулярного поля для двухподрешеточного ферримагнетика.The x-ray, Mossbauer and termomagnetic researches of pyrrhotites possessing high-temperature λ – peak (Тλ = 310 °C) on curve dependence of magnetization on temperature – I (Т) are lead. The chemical compound and conditions of formation of such pyrrhotites is determined. It is established, that samples with λ – peak possessed the raised maintenance of sulfur in comparison with pyrrhotites Fe7S8 and corresponded to structure Fe1-nS (n=0.153). As has shown experiment, these pyrrhotites are in a metastable phase condition and in due course (samples were observed during 29 years) pass in a pyrite and a pyrrhotite of structure Fe7S8 (at the presence of an atmosphere the Goethite and a szomolnokit was formed also). Because of quantum-mechanical calculations of dependence of specific magnetization from temperature for various underlattices with various integral of exchange interaction good conformity of a settlement curve with experimental is received. Calculations were made within the framework of model of a molecular field for a two-sublattice ferrimagnetic