Gold Ore Objects Research Articles

Outlook for the long-term exploitation and development of the gold mineral resource base in the Russian Federation

The current state of the gold mineral resource base of the Russian Federation is considered. The forecast of the mineral resource base development up to 2040 has been performed. Three scenarios is provided for the gold production until 2040. The need is substantiated to intensify early-stage geological exploration in order to reveal new gold ore objects, to prepare the forecasted resources, and to create the “fund of exploration-deserving objects”.

(U,Th)-He age of pyrite from the Karyernoe gold ore occurrence (flank of the Novogodnenskoye ore field, Polar Urals)

In contrast to the developed areas of the Middle and Southern Urals, the hard-to-reach and eroded northern territories of the Ural folded system remain poorly studied, which determines a large number of unevaluated gold ore occurrences and single industrial objects. The Karyernoe gold ore occurrence is located among the Middle Paleozoic volcanic-clastic rocks of the Toupugol-Khanmeishorsky gold ore district on the eastern slope of the Polar Urals. The volcanic rocks show signs of early stratabound pyrite-like mineralization, which is cut by veins and dikes of the Sobsky (D1-2) and Musyur (C1-2) complexes. A new approach – (U,Th)-He pyrite dating – was used in order to determine the age of the sulfide mineralization of the Karyernoe ore occurrence, located on the flank of the Novogodnee ore field. (U,Th)-He pyrite ages (n=7) varies in a wide range from 402 to 425 Ma. Given the petrographic and mineralogical-geochemical observations, obtained data suggest the presence of at least two stages of rock mineralization: wenlock-ludlow – 424±6 Ma; and a later Early Devonian – 402±6 Ma, which is probably associated with the intrusion of Sob complex granitoids into the rocks of the Toupugolskaya formation. The obtained ages of the sulfide mineralization of the Karyernoe ore occurrence are significantly older than the age values established for large gold ore objects of the district: Petropavlovskoye and Novogodnee-Monto deposits (~382 million years). Taking into account the position of the Karyernoe ore occurrence on the flank of the Novogodnee ore field, it can be assumed that the disseminated and layered sulfide impregnation of the volcanic rocks of the Toupugolskaya formation could have acted as one of the sources of sulfur and ore metals for later stages of sulfide mineralization in the Toupugol-Khanmeishorsky district.

Distinguishing of areas for conducting the GDP (GMM)-200 for gold, based on the compilation and analysis of the distribution regularities and forecast maps for the black-shale and epithermal type large-volume gold deposits of the Russian Federation at scale 1:2 500 000

The article is devoted to problems of distinguishing the areas for conducting the GDP (GMM)-200 oriented for the black-shale and epithermal type large-volume gold deposits. The approach is based on compilation of the distribution regularity and forecast maps of the Russian Federation at a scale of 1:2 500 000, specialized for these gold deposits, and their analysis. Regional forecast criteria of the gold ore objects and the character of their manifestation over the territory of the Russian Federation are considered. Recommendations are given for setting up the GDP (GMM)-200 programs for map sheets favorable for localization of areas promising for revealing the large-volume black shale and epithermal gold deposits. The forecasted resources of gold and silver of the Far Eastern Federal District and the Arctic zone of the Russian Federation are presented.

The features of the placement of gold deposits in Algeria

Relevance and purpose of the work. In the world market of precious metals, the value of gold is constantly growing, which determines the increase in production volumes and the need to increase resources through the search and exploration of new deposits. Te famous gold deposits in the Algerian People’s Democratic Republic are concentrated in its southern part, known as the In-Uzzali gold mining district. Te search for new deposits can be carried out afer understanding the geological features of the structure of the territory and establishing patterns of the occurrence of gold mineralization to certain geological elements. Research methods. Te research is based on the analysis of the published works of the predecessors. Te paper provides an analysis of the geological structure of the Akhaggar shield region, within which the In-Uzzali gold ore district is located. Results of the work. Te structural and tectonic structure of the district is considered. Te main features of gold-ore objects of the southern part of the Algerian Sahara (Hoggar Shield) were revealed, which allow to attribute the known deposits to three trips by association with groups of rocks: mylonites and ultramylonites (Tirek, Amesmessa); granites and syntectonic granites (Tekoyat); meta-sedimentary rocks (Tiririn, Abeggi). Tey were found to be confned to greenstone belts of Proterozoic age and belonging to the gold-quartz-sulfde formation. Recommendations for further study are given. Conclusions. Gold mineralization was detected in the objects of the In-Uzzali region in the area of the Hoggar shield. Based on the geological structure of the area, its study and conditions of localization of gold mineralization, the investigated area can be considered promising enough for the discovery of gold ore objects and replenishment of the mineral resource base of Algeria.

Geological, Mineralogical, and Geochemical Features of the Ugakhan Gold Ore Deposit of the Sukhoi Log Type (Baikal–Patom Belt)

Abstract —The Ugakhan gold ore deposit is located within the Lena gold ore province, the largest one in Russia. It belongs to the group of deposits of the Sukhoi Log genetic type. We present results of petrological, mineralogical, and isotope-geochemical study of gold mineralization at the deposit. A scheme of the sequence of mineral formation at the deposit has been developed, which includes five stages: (1) the early (syndiagenetic) stage, when framboid pyrite I enriched in Au, Ni, Co, and As formed; 2) the stage of catagenesis of ore-bearing sediments, with recrystallization of early pyrite I and crystallization of pyrite II, also with elevated Au, Ni, Co, and As contents; (3) the stage of progressive metamorphism, with the formation of ore pyrrhotite from a water–CO2 fluid with a high content of H2S; (4) the ore formation stage, marked by an assemblage of pyrite III, galena, sphalerite, chalcopyrite, and native gold at the deposit, which was synchronous with regressive metamorphism in the region; (5) crystallization of post-ore euhedral coarse-grained pyrite IV. The geochemical and isotope (δ34S and Pb–Pb) data rule out the input of mineral-forming components from an additional (external) source during the hydrothermal-metasomatic transformation of ore-bearing rocks. The δ34S values in the early morphotypes of pyrite in the deposit ores vary from +5.7 to +9.1‰ and are close to the δ34S values of the barren rocks of the Buzhuikhta Formation (+4.2 to +16.4‰). The Pb–Pb isotope characteristics and regularities of variations in Pb isotope composition established for gold mineralization indicate a predominant inflow of lead from Neoproterozoic metasedimentary strata. The mineral and geochemical specifics of the Ugakhan deposit are consistent with the concept of the metamorphic origin of gold deposits of the Sukhoi Log type, which confirms that the rocks of the Buzhuikhta Formation are promising for new gold ore objects.

Mineral prospectivity mapping for forecasting gold deposits in the Central Kolyma region (Magadan region, Russia)

A geostatistical predictive and prospecting model of gold mineralization (map of potential resource prospects) for the area of the Central Kolyma region (within the Inyali-Debinsky synclinorium) was built using machine learning methods. Multispectral satellite images, materials of medium- and small-scale geological mapping, data of medium-scale geophysical and lithochemical surveys were used as source data. Based on this data, an exhaustive set of indicators related to the search criteria was calculated. To build a forecast, the Random Forest method was used using random negative samples and averaging the result. The obtained forecast maps allow localizing potential gold ore objects with a spatial resolution of 2 km, which makes it possible to select promising areas for licensing. In addition, the possibilities of using machine learning methods for metallogenic zoning of the territory are shown.

Role of regional faults in the formation and placement of gold ore objects in western Uzbekistan

The results of the study, the relationship of regional faults with the processes of formation and mixing of gold ore occurrences in Western Uzbekistan are presented. According to researchers, the gold deposits of the region were formed under the influence of regional northwestern and transverse northeastern faults. So that the results of their research could serve as search signs and predictive criteria, they have not been studied enough to date. It is shown that the analysis of data on the location of gold ore occurrences in the network of regional faults in the region showed that 32% of gold ore objects were formed in the zones of northwestern faults. It is noted that the inter-fault space plays an important role in the placement of gold ore manifestations. Another important feature of the relationship between gold manifestations and regional faults has been revealed - this is the morphological feature (curvature area) of the faults, which determines the saturation of the inter-fault zone with manifestations of gold mineralization. The identified features of the relationship between regional faults and ring structures with gold occurrences are recommended to be used in forecasting and prospecting for gold.

Evolution of Gold in the Oxidation Zone of the Kopto Deposit (the Republic of Tuva, Russia)

Abstract —The Kopto deposit (northeastern Tuva) is assigned to gold ore objects with a combination of the Au–Cu–skarn and superposed quartz–gold–sulfide stockwork types of mineralization. From the surface, the ores underwent intense oxidation, which formed a zone of secondary gold enrichment, containing a supergene paragenesis with gold and silver chalcogenides and newly formed gold. The depth of distribution of oxidized ores from the surface is 80–90 m. The Au content varies from fractions of ppm to 150 ppm (on average, 30.8 ppm). Using computer thermodynamic modeling, it is shown how the ore gold–sulfide–quartz association transformed under oxidizing conditions with a decrease in the pH of solutions. Gold becomes more and more high-grade; acanthite appears and disappears; limonite prevails (pH = 1.65; Eh = 0.69 V). The conditions for the stability of pyrite, iron hydroxides, and gold and silver chalcogenides (petrovskaite (AgAuS) and uytenbogaardtite (Ag3AuS2)) have been estimated. It requires weakly acidic solutions with pH = 5–6 and Eh values close to zero, which ensures the stability of thiosulfate and hydrosulfide complexes of noble metals. The main difference between solutions in equilibrium with petrovskaite and uytenbogaardtite is the Ag/Au ratios, which are maximum in the first case and approximately equal in the second. The paper is concerned with a comparative analysis of the morphologic features of gold from primary and oxidized ores of the Kopto gold deposit. The aim of this work is to identify a set of signs of the supergene nature of gold and to assess the extent of its redistribution.

Gold and gold-bearing volcanogenic massive sulphide deposits of the Central Cuba

Background. Volcanogenic massive sulphide deposits (VMS) are the most important sources of Cu and Zn; they account for a large share of the world production of Pb, Ag, Au, Se, Te, Bi and Sb, as well as small amounts of many other metals. The polymetallic VMS deposits of economic value of varying degrees are known in the rocks of the Los Pasos Cretaceous Formation, Cuba.Aim. To show the potential of the Cretaceous volcanic deposits of Central Cuba for gold, silver, copper, zinc and lead deposit prospecting.Materials and methods. The study characterises the San Fernando, Independencia, Antonio, Los Cerros VMS deposits and the Boca del Toro and El Sol ore occurrences located in the Los Pasos Formation. The similarities and differences in the mineral and elemental composition and structures of the ores of these objects are described, which underlie the assessment of their economic importance.Results. The latitudinal zoning of VMS and noble metal mineralisation of the Central Cuban ore region is outlined. In the west, copper-VMS deposits with accompanying gold ore objects prevail. In the east, copper-zinc VMS deposits with barite and gold-silver objects are widespread.Conclusions. It is necessary to assume the different erosional sections corresponding to the blocks of the Cretaceous volcanic arc of Central Cuba, which is larger in the west and smaller in the east. Proceeding from the presence of veinlet gold ores, their confinement to tectonic zones and the lack of correlation between noble and chalcophile metals at the San Fernando deposit, as well as significantly different gold-silver ratios in the considered ore objects, it could be assumed that some of the gold-silver ores were formed after VMS. The obtained Au/Ag ratios are close to the ores of the high sulphidation type (high sulphide ores) from similar ore regions of Venezuela and the Kur-il island arc. In this regard, one can expect hidden gold deposits in the west and gold-silver deposits in the east of the studied area.

The non-ferrous and noble metals deposits’ position and manifestation in North Ossetia-Alania regarding the anomalies of potential fields

The relevance is determined by the need to create a scientific basis for the reassessment of known ore regions for the presence of highly liquid gold ores and the search for the new gold ore objects in previously unexplored territories to diversify the mining and metallurgical industries of North Ossetia (Alania). The purpose is to reveal the geophysical signs of non-ferrous and noble metals’ mineralization and potential gold content of ore-magmatic systems. The applied methods include the results analysis of the geophysical data use when performing the work within the prospective gold territories’ limits. A combined map construction of the gravitational and magnetic fields’ local anomalies based on the analysis of amplitude characteristics using a geophysical database of the Geological map of the Russian Federation on a scale of 1: 1,000,000 according to the sheet K-38.39 (Makhachkala) as well as the analysis of the spatial distribution of deposits and the manifestations of non-ferrous and noble metals relative to geophysical anomalies. The results obtained can be formulated as follows: the experience of using geophysical data when performing the work within the limits of the gold prospective territories in the Amur region is analyzed. The results of processing the data of the geophysical surveys results in the mountainous part of the North Ossetia (Alania) territory using modern methods for converting the potential fields are presented. The compiled maps of the gravitational and magnetic field’s local anomalies have been prepared. Within North Ossetia (Alania), spatial features of the deposits and ore occurrences of non-ferrous and noble metals with respect to anomalies of the gravitational and magnetic fields have been revealed. The confinement of the granitoid type ore-magmatic systems to negative anomalies of gravity has been established. It has been shown that potentially auriferous ore-magmatic systems are located within the limits of positive magnetic field anomalies.

МОДЕЛИРОВАНИЕ МАГМАТОГЕННЫХ РУДНЫХ СИСТЕМ ЗОЛОТОРУДНЫХ МЕСТОРОЖДЕНИЙ ВОСТОЧНОГО КАЗАХСТАНА

The article is devoted to the results of using system-defined geological modeling for forecasting gold deposits on the territory of the oldest gold mining region in the Republic of Kazakhstan – the West Kalba gold belt (East Kazakhstan). Research is aimed at developing forecast criteria and searches for new ore objects in favorable geological structures. The main attention of the conducted research was focused on a system-defined analysis of geological factors, the interaction of which provides a synergy effect and reveals the patterns of formation of gold ore objects. To solve this problem, the authors made a quantitative assessment of the development sustainability of the ore-generating elements of the system according to S.V. Vasiliev methodology. A quantitative assessment of the stability of individual factors and their interaction made it possible to assess the qualitative state of individual sections and define the natural boundaries of the areas of the corresponding hierarchical level, promising for the search of certain mineral deposits. The specific work was carried out to define the areas promising for the search of deposits based on a quantitative assessment of the individual factors stability. Using geological materials, results of geophysical work, space-geological data, the localization of promising areas within the West Kalba structural-formation zone and the Zhumba ore-magmatic system in East Kazakhstan was done.

Mineralogical and geochemical features of bismuth in Proterozoic ore-bearing structures of west part of the Ingul megablok (Ukrainian shield)

In this paper we summarize the geological information about regional distribution features of bismuth in the Ingul megablok of Ukrainian shield. Different Proterozoic ore sites situated within the Bratsk-Zvenihorodka and the Ingul-Tyasmyn metallogenic zone are considered. They are characterized by the presence of various scale deposits of uranium, rare metals (Li, Rb, Cs, Ta, Nb, W, Sn) and precious metals (Au, Ag). Minerals-concentrators of bismuth and main paragenetic associations comprising native Bi, tellurides, bismutite, maldonite, wittichenite, parkerite, matildite are investigated. It should be noted that within the intrusions of the Korsun-Novomyrgorod pluto and the Novoukraika massif, which spatially separate the Bratsk-Zvenihorodka and the Ingul-Tyasmyn metallogenic zone, there are also deposits of uranium and titanium, but bismuth is practically absent. At a relatively low content (from 5 to 60 g / t) bismuth is a typical metal for ore objects of K-U formation and rare metal pegmatites of Polokhiv and Stankuvatske ore fields. For the first time, mineral forms of bismuth (native bismuth, Pb-bismuth, galenobismuthin) were determined in the Obginnyi ore occurence, where abnormally high content values of bismuth up to 0,8-1,3%. The geochemical feature of numerous gold ore objects is the almost complete dominance of bismuth compounds with tellurium. There are headleite (Ві7Те3), telluric bismuthite (Ві2Те3), tsumoit (ВіТе), pilsenite (Ві4Те3), joseite-B (Bi4(S,Te)3) detected individualized phases in the Bi-Te system. In the skarns of the Bandurkivsky ore occurence the early productive association consists of maldonite + joseite-B + tetradimite, and the late one consists of native gold + bismuth. Bismuth sulfosalts are present in various ore objects as part of sulfide Cu-Ag-Bi and Pb-Ag-Bi mineralization. The study of geochemistry and mineralogy of bismuth was performed in M.P. Semenenko institute of geochemistry, mineralogy and ore formation of NAS of Ukraine, using a scanning electron microscope JSM-6700F (JEOL). Data on the chemical composition of minerals were obtained using microprobe devices JCXA-733, JXA-8200 (Technical Center of the National Academy of Sciences of Ukraine) and Cameca SX-100 (Technical University, Klausstal (Germany)). The data of spectral and atomic absorption analysis of the central laboratory of KP «Kirovgeologiya» were also used in writing the article.

Прогнозная геохимия рудного золота Восточного Забайкалья

The subject of the research is the methods of forecasting the Eastern Transbaikalia - a large mining region of Russia, in which the main internal and external criteria for ore content are established by modern geological mapping at a scale of 1:1,000,000. The article considers endogenous geochemical criteria for gold concentration in the Earth’s crust of the region, which constitute a mandatory methodological method for predicting gold ore objects at any scale. The aim of the work is to clarify the achieved level of knowledge about the mineralogical and geochemical criteria for gold concentration in the course of the evolution of the Earth’s crust up to the formation of industrial deposits and the isolation of ore formations. The methodology of the study is to systematize a huge amount of factual material concerning the processes of natural concentration of gold, to analyze its representativeness, to assess the completeness and reliability of published and stock information used to clarify the mineralogical and geochemical criteria for predicting ore gold. Using the chemical properties of gold, the forms of finding gold, amount of it in the forming geological complexes and natural environments, their evolution, distribution in structural and tectonic zones, some causes of concentration and mineralogical and geochemical prediction criteria are considered. Special attention is paid to the need to study and account for nanoscale (dispersed) gold. As the main ore-formation units of gold mineralization, standardized ore formations are defined with a division into gold ore proper, complex gold-bearing and gold-bearing and geological and industrial types of deposits. There are 15 geological and industrial types, of which 13 are transbaikal deposits standards and two are attracted from other regions. These types of deposits differ in the number of objects related to them. Due to some similarity in the composition of ore matter, geological and industrial types differ in the most important classification characteristics for the forecast. Areas of distribution of direct and indirect mineralogical and geochemical features grouped into mineralogical and geochemical forecast criteria are promising for endogenous concentration of gold mineralization

ЗОЛОТО-СУЛЬФИДНО-КВАРЦЕВОЕ МЕСТОРОЖДЕНИЕ БАРСУЧИЙ (СЕВЕРО-ВОСТОЧНАЯ ТУВА): МИНЕРАЛОГО-ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ И УСЛОВИЯ ОБРАЗОВАНИЯ

Золоторудные объекты в скарнах широко распространены в геологических структурах Восточной Тувы, но их промышленная оценка сопряжена со значительными трудностями из-за слабой изученности их минералого-геохимических особенностей. Актуальность исследования обусловлена необходимостью расшифровки генезиса и условий образования золоторудных объектов, локализованных в скарнах. Цель: установление минералого-геохимических особенностей и условий формирования руд месторождения Барсучий в Северо-Восточной Туве. Методы: полевые исследования, детальные минералогические исследования с изучением рудной минерализации в полированных шлифах (аншлифах) с помощью сканирующего электронного микроскопа Tescan Vega 3 sbu с ЭДС Oxford Instruments X-act. Условия формирования минеральных ассоциаций определялись термобарогеохимическими методами. Результаты. Установлено, что золоторудная минерализация на месторождении Барсучий является постскарновой и имеет гидротермальный генезис, образуя прожилково-вкрапленное и прожилковое оруденение штокверкового типа в диоритах, контактовых (роговики, скарны) и гидротермально-метасоматических породах. Околорудные процессы на месторождении выражены в березитизации и лиственитизации кварцевых диоритов, скарнов и карбонатных пород. Отложение самородного золота происходило в две стадии. По составу продуктивных минеральных ассоциаций Барсучий отвечает золото-пирротин-пирит-халькопиритовому типу с калаверитом AuTe2, петцитом Ag3AuTe2, гесситом Ag2Te и минералами ряда теллуровисмутит-теллурантимон. Рудоотложение золота на месторождении происходило из водных растворов с хлоридами Na и K, содержащих CO2 и CH4, с солёностью 1,7−10,5 мас. % NaCl-экв. при изменении окислительно-восстановительного потенциала среды при вариациях f S2, f Se2, f Te2 и снижении температуры рудоносного флюида (первая продуктивная стадия – 360–280 °С, вторая – 320–240 °С). По минералого-геохимическим особенностям месторождение Барсучий относится к малосульфидной золото-сульфидно-кварцевой формации и близко к месторождениям золото-висмутового геохимического типа.

АНОМАЛЬНОЕ ГЕОХИМИЧЕСКОЕ ПОЛЕ ЗОЛОТОРУДНОГО МЕСТОРОЖДЕНИЯ ЧЕРТОВО КОРЫТО (ЛЕНСКИЙ РУДНЫЙ РАЙОН)

Актуальность исследования обусловлена необходимостью повышения эффективности прогнозно-поисковых работ на рудное золото на основе геохимических данных. Цель: создание модели аномальной структуры геохимического поля месторождения Чертово Корыто для выявления дополнительных прогнозно-поисковых критериев золоторудных объектов в углеродисто-карбонатно-терригенных толщах. Методы: статистическая обработка геохимических данных, геохимическое моделирование. Объект: первичный геохимический ореол золоторудного месторождения Чертово Корыто. Результаты. Статистические параметры распределения металлов в крупнообъемном метасоматическом ореоле свидетельствуют об интенсивных гидротермально-метасоматических процессах, выразившихся, в первую очередь, в отложении высококонцентрированных растворов, содержащих Au, As, Ag, Pb. На основе обработки геохимических данных по первичным ореолам рассеяния создана модель геохимической зональности золоторудного месторождения Чертово Корыто. Установлено концентрически-зональное строение аномальной структуры геохимического поля месторождения. Ранняя Ba-Be-Zr-Ti-Y ассоциация элементов, выщелоченных и переотложенных в процессе кислотного метасоматоза (кварц-рутил-пирит-пирротиновый комплекс), окаймляет периферию минерализованной зоны. В промежуточной зоне метасоматического ореола распространена Сr-Ni-Co-Mn-V-Sn-P-(As) геохимическая ассоциация, обусловленная образованием кварц-пирит-арсенопирит-пирротинового комплекса, завершающего березитизацию. Отложение Au-As ассоциации происходило в более позднее время, с образованием арсенопирита в составе кварц-пирит-арсенопиритового с золотом минерального комплекса. Наиболее поздняя ассоциация Au-Ag-Pb-Zn-Сu полиметаллической с золотом стадии рудообразования (золото, галенит, сфалерит, халькопирит) приурочена к центральной части метасоматически измененных пород. Комплекс методов обработки геохимической информации совместно с использованием данных минералого-геохимического картирования обеспечил расшифровку аномальной структуры геохимического поля месторождения. Полученные результаты позволили дополнить существующее представление об аномальной структуре геохимического поля золоторудного месторождения Чертово Корыто.

Common neoproterozoic–early paleozoic evolution of ore-bearing sedimentary complexes in the southern Siberian craton

A comparison of the lithological-geochemical parameters for the deposits of the Dalnetaiga series of the Bodaibo synclinorium (the Buzhuikhta and Khomolkho suites) and the Olokit structural-formation zone (the Itykit and Ondok suites), hosting polymetallic deposits (Kholodnin, Ioko-Rybach’e), along with the obtained geochronological LA-ICP-MS U–Pb age estimates of the Ondok suite (~600 Ma), indicates their similar stratigraphic position in the Neoproterozoic in Southern Siberia. At the first stage of formation of polymetallic and gold-ore objects, the siderochalcophylic trend is considered to have appeared synchronously in the two structural zones, which could have been caused by the hydrothermal activity in the backarc basin of the Olokit structure.

ТИПОМОРФИЗМ ПИРИТОВ ОЛЬХОВСКО-ЧИБИЖЕКСКОГО ЗОЛОТОРУДНОГО ПОЛЯ (ВОСТОЧНЫЙ САЯН)

Актуальность работы вызвана необходимостью комплексного минералого-геохимического изучения золоторудных месторождений для создания прогнозно-поисковых моделей рудных объектов. Цель: изучение типоморфных свойств пирита (кристалломорфологии, элементов-примесей, термо-эдс) из разнотемпературных минеральных ассоциаций и генераций рудных тел и околорудных метасоматитов золоторудных месторождений Ольховско-Чибижекского рудного поля. Методы: кристалломорфология, термо-эдс, статистическая обработка геохимических данных, пространственное моделирование типоморфных свойств пирита. Результаты. Типоморфные свойства пирита – кристалломорфология, элементы-примеси, термо-эдс – закономерно изменяются в объёме рудных тел месторождений Ольховско-Чибижекского рудного поля и от ранних высокотемпературных минеральных ассоциаций к заключительным этапам формирования месторождений. Пириты месторождений рудного поля представлены в основном кристаллами кубического габитуса, количество кристаллов которого закономерно уменьшается с запада на восток (и волнообразно с глубиной рудных тел с амплитудой волны 200…240 м) от Лысогорского к Медвежьему и Константиновскому месторождениям. Наибольшая комбинационная устойчивость кристаллов пирита у {100}+{210}, {100}+{210}+{111}, а на Лысогорском месторождении – {100}+{321} (более 50 %), где грань {321} в комбинациях кристаллов слабо развита и характерна для низкотемпературных минеральных ассоциаций и верхних частей рудных тел. Пириты рудных тел месторождений обогащены Ag, Pb, Zn, Pt, As и особенно Au, весьма характерных для многих золоторудных объектов Сибири и других регионов. При этом в пиритах верхних частей рудных зон и надрудных ореолов содержатся повышенные концентрации Ag, Ва, Sb, Hg, а пириты средних частей рудных тел и рудных столбов резко обогащены Au, Ag, Cu, Pb, Zn, Bi, Pt, в прикорневых участках и в местах их выклинивания по простиранию и падению в пиритах накапливаются Ni, Cо, U, нередко As. Впервые в пиритах месторождений рудного поля и эфелях Ольховской обогатительной фабрики выявлены повышенные концентрации Pt и Pd. Пириты рудных тел и околорудных метасоматитов месторождений рудного поля имеют преобладающую электронную (Константиновское), электронно-дырочную (Медвежье) или дырочную (Лысогорское) проводимость. С глубиной рудных тел и с запада на восток рудного поля от Лысогорского к Медвежьему и Константиновскому месторождениям закономерно увеличивается электронный тип проводимости пиритов как из продуктивных минеральных ассоциаций, так и из околорудных метасоматитов. На основании выявленных типоморфных признаков пиритов: кристалломорфологии, элементов-примесей и термо-эдс, закономерно изменяющиеся в пространстве и во времени, можно судить об уровне эрозионного среза рудных тел и месторождений, их перспективности на глубину и фланги. Минералогическое картирование по пириту на золото необходимо проводить (в комплексе с другими методами исследования) на всех стадиях геологоразведочных работ.

Common Neoproterozoic–Early Paleozoic Evolution of Ore-Bearing Sedimentary Complexes in the Southern Siberian Craton

A comparison of the lithological–geochemical parameters for the deposits of the Dalnetaiga series of the Bodaibo synclinorium (the Buzhuikhta and Khomolkho formations) and the Olokit structural-formational zone (the Itykit and Ondok formations), hosting polymetallic deposits (Kholodnin, Ioko-Rybach’e), along with the obtained geochronological LA-ICP-MS U–Pb age estimates of the Ondok Formation (~600 Ma), indicates their similar stratigraphic position in the Neoproterozoic in Southern Siberia. At the first stage of formation of polymetallic and gold-ore objects, the siderochalcophylic trend is considered to have appeared synchronously in the two structural zones, which could have been caused by the hydrothermal activity in the back-arc basin of the Olokit structure.

New Promising Gold-Ore Objects in the Strelna Greenstone Belt, Kola Peninsula

Data on gold ore objects in the Strelna Greenstone Belt in the southeastern Kola Peninsula are presented in the paper. The studied Vorgovy and Sergozero ore occurrences are localized in the zone of tectonic contact of the Neoarchean complexes making up the greenstone belt and the volcanic–sedimentary sequences of the Paleoproterozoic Imandra–Varzuga Zone. The Vorgovy gold occurrence is related to stockwork of carbonate–quartz veins and veinlets hosted in a biotite gneiss transformed into chlorite–sericite–quartz metasomatic rock with pyrrhotite–arsenopyrite dissemination. The Sergozero occurrence is localized in amphibolites corresponding to komatiitic and tholeiitic basalts hosted in biotite gneiss (metapelite). Mineralization is confined to the zone of tectonized contact between komatiitic and tholeiitic basalts, where it is controlled by a strip of metasomatic biotite–calcite rock with gersdorffite–arsenopyrite dissemination. The native gold grains medium to high in fineness are up to 0.1 mm in size and mainly localized at the contact of arsenopyrite and gersdorffite with gangue minerals. Gold mineralization is of superimposed character, and, as indicated by isotopic geochronology, was formed at the retrograde stage of the Svecofennian regional metamorphism. Comparison of ore occurrences localized in the Strelna Greenstone Belt with gold deposits in greenstone belts of the western Fennoscandian Shield and the Superior Province in Canada allows us to suggest a high perspective of the entire Strelna Belt for gold.

Natural electric fields in Siberian gold deposits: structure, origin, and relationship with gold orebodies

Characteristics of the constant natural electric field in the Siberian gold ore areas are given. The regularities of spatial variations in the electric-field potential and the parameters and properties of anomalies have been established. The cause of the natural electric field in deposits of major genotypes has been elucidated. It is shown that the electric field is induced mainly by physicochemical processes running in electron-conducting syn-ore metasomatites and by circulation of groundwaters. Orebodies do not influence significantly the structure of the observed electric fields. We give recommendations on application of the electric-field method at various gold ore objects.