Gold Ore Field Research Articles

Characteristics of Supergene Gold of Karst Cavities of the Khokhoy Gold Ore Field (Aldan Shield, East Russia)

Typomorphic features of supergene gold in karst cavities were studied in the recently discovered Au–Te–Sb–Tl deposit within the Khokhoy gold ore field of the Aldan-Stanovoy auriferous province (Aldan shield, East Russia). Two morphological types of supergene gold, massive and porous, are recognized there. The first type is represented by gold crystals and irregular mass, with the fineness ranging from 835 to 1000‰. They are closely associated with goethite, siderite, unnamed Fe, Te, and Tl carbonates, Tl tellurites/tellurates and antimonates, as well as avicennite with a Te impurity. The second type is represented by mustard gold of two types with different internal structure: microporous and dendritic. The supergene gold is characterized by persistently high fineness. Along with Ag, it invariably contains Hg (up to 5.78 wt%) and Bi, and, rarely, Pb, Cu, and Fe. The supergene gold is chemically homogeneous, and its particles are all marked by high fineness, without any rims or margins. The obtained characteristics made it possible to prove the existence of two genetic types of supergene gold. Mustard microporous gold is the result of the decomposition of the associated minerals—goethite, Tl oxides, tellurium, Fe, Mn and Tl carbonates and antimonates, containing microinclusions of gold. Massive gold and dendrites are newly formed. The decomposition, remobilization, and reprecipitation of residual gold nanoparticles and their aggregation led to the formation of dendrites, and with further crystal growth and filling of pores, to gold of massive morphology. In terms of morphology, internal structure, fineness, and trace element composition, supergene gold of the Khokhoy gold ore field is comparable to gold from the Kuranakh deposit (Russia) and the Carlin-type gold deposits. It also is similar to spungy and mustard gold from Au–Te and Au–Sb deposits, weathering crusts, and placers. Its main characteristic feature is a close paragenesis with Tl minerals.

Genesis of gold deposits in the Wulong orefield, Liaodong Peninsula, North China Craton: Constraints from ore deposit geology, REE, and C–H–O–S–Pb isotopes

The Wulong gold orefield is located in the eastern part of the Liaodong Peninsula, and contains the large Sidaogou and Wulong gold deposits, as well as several small gold deposits with a total of >100 tonnes of gold reserves. These deposits are hosted within Paleoproterozoic metamorphic rocks of the Liaohe Group and Mesozoic granitoids, and are structurally controlled by NNE–SSW‐ and NNW–SSE‐trending faults and interlayer fractures. The Sidaogou deposit is characterized by altered‐rock‐type mineralization occurring within interlayer fracture zones, whereas the mineralization in the Wulong deposit occurs as auriferous quartz veins along subsidiary faults. These two types of gold mineralization are representative of the mineralization in the Wulong orefield. The REE contents of quartz and calcite, together with previous studies of fluid inclusions, indicate that the ore‐forming fluids of the Sidaogou deposit were reduced NaCl–H2O–CO2 fluids. Quartz yielded δ18OH2O‐SMOW, δDSMOW, and δ13CCO2 values of +4.7‰ to +6.6‰, −82.2‰ to −79.0‰, and − 13.1‰ to −6.6‰, respectively, and calcite yielded δ13CCO2 and δ18OV‐SMOW values of −2.3‰ to −2.0‰ and + 7.4‰ to +7.9‰, respectively. These results indicate that the ore‐forming fluids of the Sidaogou deposit were derived primarily from magmatic water, and the C was sourced mainly from deep‐seated magma with a minor contribution from sedimentary organic matter. Pyrite crystals have δ34SCDT values of +4.9‰ to +12.9‰, indicating the S source was a combination of the magmatic system and ore‐bearing metamorphic rocks. Pyrite has 208Pb/204Pb ratios of 38.226–38.336, 207Pb/204Pb ratios of 15.606–15.683, and 206Pb/204Pb ratios of 18.345–18.492, suggesting that the Pb in the Sidaogou deposit was derived primarily from the upper crust, with minor input from the mantle. Taking into account previous studies of the Wulong deposit, we propose a metallogenic model for the Wulong gold orefield. Deep‐seated ore‐forming fluids were released from different intrusions hidden below the Wulong orefield for each of the deposits. The ore‐forming fluids moved through the metamorphic rocks of the Gaixian Formation along interlayer fracture zones, where intensive water–wallrock reactions, and episodic temperature and pressure drops resulted in the formation of altered‐rock‐type Sidaogou deposit. The fluids ascended to the Wulong and Sanguliu intrusions along NNE–SSW‐ and NNW–SSE‐trending faults, where temperature and pressure dropping, water–wallrock reactions, and fluid immiscibility generated the vein‐type Wulong deposit. The gold deposits in the Wulong orefield share many similarities with the Linglong‐ and Jiaojia‐type gold deposits in the Jiaodong Peninsula, including geological setting, mineralization style and age, and sources of ore‐forming fluids and metal.

The first data about the structure and mineral composition of the ores of the Tarakon potential gold ore field (the Far East of Russia)

The obtained original materials, in conjunction with the literature data (hydrochemical contrasting halos), make it possible to predict a new (Tarakonsky) gold ore field within the eastern part of the Argun superterrane. Industrial concentrations of gold are noted in quartz metasomatites from granites and limestones. The amount of ore minerals usually does not exceed 5-10%. They are present in the rocks in micron and submicron size, represented mainly by pyrite, less often galena, sphalerite, chalcopyrite, ilmenite, hematite, magnetite, faded ores, and native high-grade gold. It is assumed that the formation of the Tarakonsky gold ore field, as well as most of the ore objects in the region, is associated with the manifestation of Late Mesozoic magmatism.

Geoelectrical Characteristics of Gold-Ore Deposits of the Upper Priamurye Region

The results of measurements of the electrical properties of rocks and induced polarization surveying are analyzed for three gold-ore deposits including the Bamskoe, Berezitovoe, and Pokrovka in the Upper Priamurye region. The spatial correlation is shown between mineralization zones and contrasting resistivity boundaries mapped within the gold-ore fields. The assumption is validated that the blocks of high-resistivity rocks have minimal permeability and therefore they were able to act as screens affecting the hydrodynamic features of the hydrothermal system at the stages of deposit formation and at the stages of mineralization formation. This makes such geoelectrical boundaries an important element for exploration, which should be accounted for when interpreting electric prospecting data. The induced polarization survey establishes a diverse interpretation of the polarizability anomalies within the gold-ore fields and a lack of correlation between ranges of increased induced polarization values and gold-ore mineralization. Methods for evaluating polarizability anomalies are proposed.

The First Data on the Structure and Mineral Composition of Ores at the Tarakon Potential Gold Field, Russian Far East

The original materials obtained, along with the literature data (hydrochemical contrasting halos), make it possible to predict a new (Tarakon) gold ore field within the eastern part of the Argun superterrane. Commercial gold concentrations are noted in quartz metasomatic rocks after granite and limestone. The amount of ore minerals usually does not exceed 5–10%. They commonly occur in the rocks as micron and submicron particles mainly of pyrite, less often, of galena, sphalerite, chalcopyrite, ilmenite, hematite, magnetite, fahlore, and native high-grade gold. It is assumed that formation of the Tarakon gold ore field, as well as of most ore bodies in the region, is related to Late Mesozoic magmatism.

Localization patterns of mineralization, age, and sources of substance of the Malomyr gold ore field (Eastern part of the Mongolian–Okhotsk fold belt)

To the best of our knowledge, this study is the first to reliably assess the age of gold mineralization in the Malomyr field (eastern part of the Mongolian-Okhotsk fold belt), one of the best known deposits in the Far East. The obtained data confirmed that the age of the hydrothermal ore process that resulted in the formation of the Malomyr deposit was ~ 134–130 million years and that the age of the postore dykes was 110–104 million years. Data related to the occurrence of magmatism within the region under consideration were not available, which made it impossible to link the ore mineralization of the Malomyr deposit with the magmatic processes. Based on the data obtained in this investigation, the dislocation processes accompanied by the hydrothermal activity that was confirmed using the structural examinations results evidently played a significant role in ore mobilization and redistribution as well as the formation of the Malomyr deposit. The first Rb-Sr and δ34S results of this research indicated that both the “crust” and “mantle” sources were available among the ore sources.

H+ and Li+ Charge Compensator Ions in Structural Channels of Quartz from Gold Deposits of the Darasun Gold Ore Field (Eastern Transbaikalia, Russia): Electron Paramagnetic Resonance Data

Electron paramagnetic resonance (EPR) is used to study the composition and diffusion mobility of charge compensator ions in structural channels of quartz from the Darasun, Teremkinskoe, and Talatui gold fields of the Darasun ore field. The ion distribution features in quartz are evaluated based on their ability to participate in neutralizing the electrical charge of structural defects occurring in quartz. In accordance with this, the ion composition was assessed from the ratio of concentrations of Ti centers with different charge compensator ions, and their mobility was determined based on the formation rate of these centers under irradiation of quartz. The research shows the presence of two main types of charge compensator ions, H+ and Li+, in structural channels of quartz from the Darasun ore field. It was found that the diffusion mobility of H+ ions in channels are one to two orders of magnitude higher than that of Li+. There is no correlation between the composition of charge compensator ions and the fluid composition. Different ratios between concentrations of H+ and Li+ ions in structural channels of quartz from different deposits were established. The maximum concentrations of H+ ions and the minimum concentrations of Li+ ions are recorded in quartz from the Darasun ore field, and an inverse relation was recorded in quartz from the Talatui deposit. This can be explained by the migration of the gas component of fluid during ore genesis. It was shown that EPR can be applicable to quantitatively estimate the degree of dynamic recrystallization of quartz.

Mapping of fluid, alteration and soil geochemical anomaly as a guide to regional mineral exploration for the Dehua gold orefield of Fujian Province, SE China

The Dehua gold ore-field, located in the central-eastern Fujian Province, SE China, is an important part of the renowned Dehua-Youxi-Yongtai gold ore production area. The ore-field contains several low-intermediate sulphidation epithermal gold deposits and numerous gold-bearing mineralized bodies. The extensive presence of intensely altered rocks, suitable structural environment, acidic intrusions and volcanic-subvolcanic rocks indicates an important potential for epithermal gold mineralization. In this work, fluid inclusion homogenization temperature and alteration mapping was carried out by fluid inclusion microthermometry in quartz and identification of alteration minerals closely related to the known mineralization. The result shows the trend of temperature contour curves as well as the shape of low argillic alteration zones implying that the area north of Qiucun might be profitable for future mineral exploration. The fluid and alteration mapping, in combination with soil geochemical mapping, defines the architecture of the epithermal-porphyry ore-forming system in the Dehua ore-field. Finally, the presence of intensely altered areas, high value zones of hydrothermal fluid flows and combined anomaly areas of multi-element association indicate that the region north of Qiucun has an important potential as a preferred target area for gold prospecting in the Dehua ore-field.

Geology of the Karalon Gold Ore Field in the Mid-Vitim Highlands

The paper present new data on the geology of the Karalon gold ore field in northern Buryatia, including its regional position and a brief description of the mineralization, gold–sulfide and gold–quartz–low-sulfide ore objects, host rocks, and complexes, which are components that make up juvenile Late Neoproterozoic Earth’s crust formed in the course of rifting. Paleozoic dike series are characterized, as well as the ore-controlling complex of beresite–listvenite metasomatic rocks. Regularities in the emplacement of gold objects and their control are generalized. Veins and veinlets of gold–quartz mineralization are hosted in gently and steeply dipping structures in the ore field, which formed prior to the intrusive Dogaldyn massif of subalkaline rocks 252 Ma ago.

On Electrical Conductivity at Depth in the Shanuch Copper–Nickel and the Aginskoe Gold-Ore Fields, Kamchatka

This paper is concerned with the method of interpretation and with the results of magnetotelluric sounding (MTS) along the line connecting the Shanuch copper–nickel and the Aginskoe gold ore deposit. The interpretation revealed that the upper section divides into two blocks according to the electrical resistivity. The western block has a high resistivity, which is due to the metamorphic and igneous basement rocks that are exposed at the ground surface. The eastern block has a low resistivity, which is due to the presence of a conductive sedimentary–volcanogenic cover involving a wide network of discontinuities. A low resistivity layer was identified at depths of 30–60 km. The deep-seated faults that have been identified by interpretation in the eastern block penetrate through the lithosphere as far as the conductive layer; fluids can move along these faults upward into the upper crust where at lower temperatures they release minerals whose accumulations make up ore deposits of nonferrous and noble metals.

ОСОБЕННОСТИ ВЕЩЕСТВЕННОГО СОСТАВА ПОРОД ВЕРХНЕЯНСКОГО ЗОЛТОРУДНОГО ПОЛЯ (СЕВЕРНОЕ ЗАБАЙКАЛЬЕ)

The mineralogical and geochemical features and the material composition of the ore metaso-matites of the Verkhneyanskoye gold ore field (VGOF) have been studied. VGOF is located in the northern part of the Baikal-Muya belt. Ore bodies are represented by linear stockwork of gold-bearing metasomatites that trace the ore-controlling fault zone. Host rocks are ayulindinskiy metavolcanogenic formation, granitoids and gabbros of the yano-mamakan complex. The rocks in the fault zone have been changed to the ore stage. Аs a result, gold bearing (albite) sericite-quartz-chlorite-carbonate metasomatites and gold-bearing quartz-carbonate vein metaso-matites were formed. At the ore stage, the transformation of enclosing rocks into the fault zone with the formation of gold-bearing (albite) sericite-quartz-chlorite-carbonate metasomatites and gold-bearing quartz-carbonate vein. Gold-bearing pyrite-II and pyrite-III-chalcopyrite-II-galena associations were identified on the territory of the VZRP. Free gold and gold in the form of tellurides (petzite, calaverite) in association with altaite and melonite was found in ore bodies

ЗАКОНОМЕРНОСТИ ФОРМИРОВАНИЯ ФИЗИКО-МЕХАНИЧЕСКИХ СВОЙСТВ ПОРОД ЗОЛОТОРУДНЫХ МЕСТОРОЖДЕНИЙ

ЗАКОНОМЕРНОСТИ ФОРМИРОВАНИЯ ФИЗИКО-МЕХАНИЧЕСКИХ СВОЙСТВ ПОРОД ЗОЛОТОРУДНЫХ МЕСТОРОЖДЕНИЙ

Благородные металлы рудного поля Албынского золоторудного месторождения Верхнего Приамурья

Благородные металлы рудного поля Албынского золоторудного месторождения Верхнего Приамурья

SR-XRFA in Biogeochemical Studies: Elemental Composition of Larch Tissues (Larix cajanderi Mayr.) of the Kuranakh Gold ore Field (Russia, Yakutia)

Technogenic impact on the elemental composition of larch (Larix cajanderi Mayr.) in the Kuranakh Gold ore field (Russia, Yakutia) is considered. Elemental composition of the larch tissues was determined by means of X-ray fluorescence measurements with synchrotron radiation at the “Siberian Synchrotron and Terahertz Radiation Center” based on VEPP-3 of the Budker Institute of Nuclear Physics SB RAS. Comprehensive possibilities of the X-ray fluorescence measurements along with the simple preparation of biological samples, allowed us to carry out valuable biogeochemical studies. New data on the accumulation of macroelements K, Ca, Mn, Fe, biophilic microelements Cu, Zn, chalcophilous Mo, Pb, Ag, As, Sb, Ga, Cd, Tl, rare lithophilous Rb, Sr, Zr, Y, Nb, in the tissues of larch (Larix cajanderi Mayr.) of the natural taiga landscape and the tailing dump in the Kuranakh Gold ore field were obtained. The results allow us to assess both natural and technogenic biogeochemical anomalous aureole of gold mining areas.

Up-dated ore composition data (Central ore-field, Kuznetsk Alatau)

Applying scanning electron microscope (SEM), energy-dispersive microanalyzer and X-ray ray fluorescence microscope the ore mineral composition in Central gold-ore field ore field (Kuznetsk Alatau) was investigated. Eleven new minerals were detected in this ore field. The differentiated behavior of mineral formation stages in veinsand near-veined beresites was determined. The composition of native gold was studied, as well as the distribution of trace elements in pyrite.

Rank-Size Statistical Assessments of Undiscovered Gold Endowment in the Bendigo and Stawell Zones (Victoria) and the Mossman Orogen (Queensland), Australia: Comparison with Three-Part Assessment Results

The Bendigo and Stawell zones in Victoria and the Mossman Orogen in north Queensland host numerous orogenic gold deposits and are likely to contain significant undiscovered gold resources. This paper discusses applications of Zipf’s law to estimate the scale of residual gold endowment in each of the regions. Testing various plausible scenarios on whether or not the largest deposit in each region has been discovered and its endowment adequately evaluated provided some measure of uncertainty of assessment results. The Bendigo and Stawell zones are estimated to host 12 undiscovered ore fields with >31 t (1 Moz) of contained gold and another 35 undiscovered ore fields with >10 t (0.32 Moz) of gold, containing in total 1600 t (51 Moz) of gold. The total residual orogenic gold endowment of the Mossman Orogen is estimated to be between 3 and 30 t of gold, contained in extensions of known deposits and up to six significant undiscovered gold ore fields each containing >1 t of gold. These estimates are comparable to results of recent three-part quantitative mineral resource assessments for those areas.

Hydrothermal alteration mapping of Siberian gold-ore fields based on satellite spectroscopy data

The mapping of the hydrothermal alterations in Urjahskoe and Fedorov-Kedrov gold-ore fields was conducted by applying channel relationship method (band ratio) based on ASTER spectral-zonal satellite image data. It was determined that the calculated mineral indices in ore-bearing structures are zonal. Outer ore-bearing structures revealed increased ferric mineral index values, while inner - high epidote- chlorite- calcite and muscovite- siderite mineral index values. Detected regularities could be used in identifying potential gold-ore bearing areas within identical fields based on remote sensing survey data.

Crystal morphology and thermal EMF of pyrites in the western flank of Sukholozhsky gold ore field (Lenski ore area)

The investigated crystal morphology and thermal EMF of pyrites in the western flank of Sukholozsky ore field showed that the pyrite crystals have cubic habitus with a weakly-developed face {210}. The crystal faces {100} and {210} are covered with multiple irregular-oriented growth laminae. It has been determined that pyrites have such a property as p-type conduction and embrace insignificant thermal EMF variations. The results of the research indicated the fact of upper ore zone erosion in the western flank of Sukholozhsky ore field and its area potential at depth.

Methodological approaches in estimating anomalous geochemical field structure

Mathematical statistic methods were applied to analyze the core samples from vertical expendable wells in Chertovo Koryto gold ore field. The following methods were used to analyse gold in samples: assay tests and atomic absorption method (AAS), while emission spectrum semiquantative method was applied to identify traces. The analysis of geochemical association distribution in one central profile demonstrated that bulk metasomatic aureoles are characteristic of concentric zonal structure. The distribution of geochemical associations is correlated to the hydrothermal stages of mineral formation identified in this deposit. It was proved that the processed geochemical data by factor and cluster analyses provided additional information on the anomalous geochemical field structure in gold- bearing black-shale strata. Such methods are effective tools in interpretating specific features of geochemical field structures in analogous potential ore-bearing areas.

Re‐Os Dating of Molybdenite from Hadamengou Gold Ore Field in Inner Mongolia and Its Geological Significance

Re‐Os Dating of Molybdenite from Hadamengou Gold Ore Field in Inner Mongolia and Its Geological Significance