Gold Deposits Research Articles

Alteration out of sight: a petrographic and HyLogger study of the McPhillamys gold deposit, east Lachlan Orogen, New South Wales

Lithology, alteration and Au mineralisation characteristics of the McPhillamys gold deposit in central NSW have proved difficult to interpret owing to structural overprinting. Previous models for the genesis of Au mineralisation include syngenetic (late Silurian Au-rich volcanic massive sulfide; VMS) or epigenetic (Carboniferous orogenic Au). We combine extensive new HyLogger spectral data (SWIR and TIR), petrographic analysis, geochronology and isotopic data to determine the alteration/mineralisation paragenesis, alteration zonation and effects of lithological control on mineralisation by using both downhole and broad-scale 3D mineralogical characterisation. The mineralisation at McPhillamys is stratabound within a coarse andesitic/dacitic volcaniclastic package. Alteration involved the development of an initial potassic core (microcline (ex-adularia)–quartz–pyrite) associated with the mineralised volcaniclastic package at the centre of the orebody and extending into the overlying non-mineralised andesitic volcanic/volcaniclastic package north and south of the mineralised zone. Propylitic-style alteration (albite–pyrite–chlorite–carbonate ± epidote) forms an outer shell to the mineralisation, except at the northern and southern extents of the mineralised trend. White mica, chlorite, feldspar and carbonate all display consistent and mappable compositional variation between mineralised and non-mineralised sequences. It is difficult to decipher the early history of the deposit and geochronology (U–Pb and Ar–Ar), presented in this study, is unable to distinguish if mineralisation and alteration developed just after deposition of the host sequences during the latest Silurian (ca 423 Ma) with extensive recrystallisation during both Tabberabberan (ca 390 Ma) and Kanimblan (ca 350 Ma) orogenic events, or if mineralisation developed solely during the Tabberabberan Orogeny (ca 390 Ma) with extensive recrystallisation during the Kanimblan Orogeny (ca 350 Ma). We suggest the mineralogy, broad spatial distribution (700 m long, 250 m width, and up to 700 m depth) and paragenesis of alteration and mineralisation at McPhillamys are consistent with a deformed late Silurian lithologically controlled low-sulfidation epithermal, or potentially a shallow water (subsea-floor) Au-rich VMS system.

Genesis of the Shabaosi Gold Field in the Western Mohe Basin, Northeast China: Evidence from Fluid Inclusions and H-O-S-Pb Isotopes

The Shabaosi gold field is located in the western Mohe Basin, part of the northern Great Xing’an Range, NE China, and contains multiple gold deposits. However, the sources of the ore-forming materials, the fluid evolution, and the genesis of these gold deposits have been disputed, especially regarding the classification of these deposits as either epithermal or orogenic gold systems. Based on detailed field geological investigations and previous research, we conducted systematic research on the Shabaosi, Sanshierzhan, Laogou, and Balifang gold deposits using fluid inclusion and H-O-S-Pb isotope data, with the aim of constraining the fluid properties, sources, and mineralization processes. Fluid inclusion analyses reveal diverse types, including vapor-rich, vapor–liquid, CO2-bearing, CO2-rich, and pure CO2. Additionally, only a very limited number of daughter mineral-bearing fluid inclusions have been observed exclusively in the Laogou gold deposit. During the early stages, the peak temperature primarily ranged from 240 °C to 280 °C, with salinity concentrations between 6 and 8 wt% NaCl equiv., representing a medium–low temperature, low salinity, and a heterogeneous CO2-CH4-H2O-NaCl system. With the influx of meteoric water, the fluids evolved gradually into a simple NaCl-H2O system with low temperatures (160–200 °C) and salinities (4–6 wt%). The main mineralization stage exhibited peak temperatures of 220–260 °C and salinities of 5–8 wt% NaCl equiv., corresponding to an estimated formation depth of 1.4–3.3 km. The δDV-SMOW values (−138.3‰ to −97.0‰) and δ18OV-SMOW values (−7.1‰ to 16.2‰) indicate that the magmatic–hydrothermal fluids were progressively diluted by meteoric water during mineralization. The sulfur isotopic compositions (δ34S = −0.9‰ to 1.8‰) and lead isotopic ratios (208Pb/204Pb = 38.398–38.579, 207Pb/204Pb = 15.571–15.636, and 206Pb/204Pb = 18.386–18.477) demonstrate that the gold predominantly originated from deep magmatic systems, with potential crustal contamination. Comparative analyses indicate that the Shabaosi gold field should be classified as a epizonal orogenic gold system, which shows distinct differences from epithermal gold deposits and corresponds to the extensional tectonic setting during the late-stage evolution of the Mongol–Okhotsk orogenic belt.

Geophysical Exploration of Gold Mineralization Zones using Induced Polarization and Electrical Resistivity Imaging Methods at Itagunmodi Area of Ilesha, Osun State, Southwest Nigeria

Gold is a valuable and economically solid mineral due to its unique physical and chemical properties. However, this research investigated the potential zones of gold mineralization at Itagunmodi in Atakunmosa West Local Government Area of Ilesha, Osun State, Nigeria, through the generation of subsurface 2D resistivity and induced polarization models that provide helpful information in determining the depths and lateral distances of suspected gold deposits. The time domain-induced polarization and electrical resistivity imaging (ERI) measurements were carried out along six traverses using dipole-dipole configurations with electrode separations of 5.0 m and profile lengths ranging from 128.0-315.0 m. The apparent resistivity and chargeability data were used to generate 2D subsurface models using RES2DINV software to accurately and effectively interpret the location of gold mineralization potential zones. The results from the 2D ERI and chargeability models along traverses 1 and 2 revealed low resistivity zones ranging from 16.3-669.0 Ωm corresponding to high chargeability zones ranging from 288 to 444 msec on the 2D chargeability section, which were identified at lateral distances of 82.5-102.5, 167.0-187.5, 164.0-260, 95.0-110.0, and 55.0-75.0 m from approximated depths 9.94-26.20, 6.76-36.98, 11.0-23.0, and 6.0-12.0 m beneath the subsurface. These anomalous zones along these traverses weresuspected to harbour minerals such as goldsince they can also be attributed to quartz veins and fractures that may likely be filled with conductive materials like gold and associated base metals. This research has revealed the efficacy of electrical resistivity and induced polarization methods in delineating the suspected regions of gold mineralization.

Investigating the formation and enrichment processes of super-large North Sanshandao gold deposit (Jiaodong Peninsula, Eastern China): an in-depth mineralogical perspective

Abstract The formation processes underlying super-large gold deposits present a captivating area of study, with a particularly enigmatic aspect being the mechanisms by which gold forms and accumulates within undersaturated hydrothermal fluids, notably in the presence of high-grade, thick ore bodies. To address this issue, we conducted comprehensive mineral textural, geochemical, isotopic, and machine learning analyses on gold ore-related sulfides from the North Sanshandao gold deposit (∼562 t @ 4.35 g/t), which is the second-largest deposit in the world-class Jiaodong gold province, and recognized as China's inaugural super-large offshore gold resource. The deposit is hosted in the Jurassic Linglong granite, and has four stages of alteration and mineralization: (I) quartz-pyrite-K-feldspar, (II) quartz-pyrite-chalcopyrite-native Au, (III) quartz-pyrite-galena-sphalerite-native Au, (IV) ore-barren siderite-ankerite-calcite. Four types of auriferous pyrite were distinguished, including (stage II) porous Py2a and its Py2b overgrowth, and (stage III) Py3a and its Py3b overgrowth. The gold in Py2a occurs mainly in nanoparticles, while Py2b, Py3a, and Py3b contain high content of lattice gold and coarse-grained native gold, with the gold and arsenic contents strongly correlated positively. The characteristics of a porous core and a smooth edge suggest the occurrence of coupled dissolution-reprecipitation (CDR) processes during the early mineralization stage. Low melting point chalcophile elements (LMCE, e.g., Bi, Te, Sb), are frequently associated with gold, indicating that the LMCE melt may play a role in the remobilization of gold, in addition to fluids. Combined with the trace element composition, we show that the CDR process had led to the Au-LMCE liberation and the Au remobilization in the ore-fluid and LMCE melt. This process may have significantly upgraded the ore and formed large visible gold grains and local high-grade ore zone. Mineral geochemistry of stage I arsenopyrite suggests that the mineralization temperature = 300–400 °C (concentrate 342–379 °C), logf(S2) = −11.5 to −6.5 (concentrate −9.5 to −7.5), and logf(O2) = −34.9 to −24.7 (concentrate −30.2 to −26.7). Sphalerite composition suggests that the temperature dropped 320 °C in stage III. Both the North Sanshandao gold deposit (δ34SV-CDT = 10.75–13.31‰, n = 61) and the Jiaodong gold province (δ34SV-CDT (1st and 3rd quartile) = 7.1–10.8‰, n = 1646) have high δ34SV-CDT values, implying that sulfate reduction is a key ore-material source. Our study provides a new model for the widespread development of over 80% of the disseminated-type mineralization in the Jiaodong Peninsula, emphasizing Au remobilization as a key factor for the formation of high-grade and high-tonnage ore zones, and shed new light on the multistage ore-material enrichment in large-scale gold mineralization.

Fluid inclusion and H–O–S isotope constraints on the genesis of the Ashawayi gold deposit, Southern Tianshan, Xinjiang, NW China

The Ashawayi gold deposit is situated in the eastern part of the Southern Tianshan Sb–Hg–Au metallogenic belt, a significant source of gold in China. This deposit exhibits typical disseminated mineralization controlled by faults or fractures. This study presents a comprehensive set of petrological, fluid inclusion, and H–O–S isotopic data for the deposit. Fluid inclusions can be classified into three main types, namely, NaCl–H2O, CO2-bearing aqueous solutions, and pure CO2. The quartz from the ore contains fluid inclusions predominantly composed of NaCl–H2O and CO2. The homogenization temperatures of these inclusions range from 200°C to 360°C. Estimates based on fluid inclusion pressures suggest that mineralization occurred at depths of approximately 2–4 km. Mineralization is associated with fault healing and fracturing, which induce secondary fluid immiscibility. Fluid boiling features indicate rapid upwelling of ore fluids from depth, with metal precipitation occurring through decompression at shallower levels. H–O–S isotopes suggest that metals were extracted from the country rock and that the ores were formed through the mixing of metamorphic fluids with meteoric water. A combined analysis classifies the Ashawayi gold deposit as a hypabyssal orogenic gold deposit.

Interaction behavior between coarse-particle pyrite and fine-particle pyrite in flotation

Pyrite is commonly associated with gold deposits and serves as a gold-bearing mineral. The flotation recovery of gold-bearing pyrite generally determines the overall gold recovery. In this study, pyrite from a gold ore in southwestern Guizhou Province was selected to investigate the interaction behavior between coarse-particle pyrite (CPy) and fine-particle pyrite (FPy) during flotation. Flotation tests were conducted in combination with laser particle size analysis, optical microscopy, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and a self-assembled “Particle Attachment Dynamic Observation System.” The results showed that the recovery of FPy (P80 = 26.75 µm) was lower than that of CPy (P80 = 147.89 µm) under the same collector concentration (butyl xanthate). However, the flotation recovery of the CPy-FPy mixture was consistently higher than that of either CPy or FPy alone, particularly at low collector concentrations. Further investigation confirmed that CPy acted as a carrier for FPy, enhancing its recovery into the froth during mixed flotation. Calculations based on the extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) model demonstrated that butyl xanthate increases hydrophobic forces between pyrite particles, promoting agglomeration. This finding explains why the flotation recovery of the CPy-FPy mixture in a butyl xanthate suspension exceeds that of CPy or FPy alone.

Research dynamics and frontier trends of orogenic gold deposits: a knowledge map based on bibliometrics

Orogenic gold deposits represent a vital component of global gold reserves, functioning as both significant sources of gold and essential indicators for understanding crustal metallogeny within collisional tectonic environments. This study employs bibliometric analysis on 2,476 publications sourced from the Web of Science Core Collection (1995–2025) to delineate the intellectual evolution and emerging frontiers in orogenic gold research. Through systematic examination utilizing Citespace and Vosviewer, we identify publication trends, geographic distribution, institutional contributions, and citation networks of global orogenic gold deposit studies. Key findings reveal concentrated research output from China (1,031 papers), Australia (626 papers), and Canada (326 papers), with the China University of Geosciences and the University of Western Australia emerging as prominent institutional hubs. While Deng Jun and Santosh M. lead contemporary productivity metrics, foundational contributions by Groves DI (3,459 citations) and Goldfarb RJ (4,590 citations) continue to serve as pivotal citation anchors. Based on the analysis, the research frontiers should focus on three key areas: (1) Cross-scale mineralization mechanism studies, including numerical simulations of supercritical fluid (H2O-CO2 ± CH4) phase behavior, four-dimensional visualization reconstruction of lithospheric material cycles, and quantitative analysis of pressure-driven (∼150 MPa) phase transitions and adsorption kinetics in sulfide-mantle fluid coupling mechanisms; (2) Technological and methodological advancements, emphasizing the development of AI-powered three-dimensional orebody prediction models and the establishment of deep exploration technology consortia capable of penetrating up to 8 km; (3) Theoretical paradigm shifts, promoting the integration of micro-area isotopic tracing techniques with deep dynamic models to elucidate the control mechanisms of supercontinent cycles on the spatiotemporal architecture of mineralization systems. This field is transitioning from empirical exploration toward a theory-driven research paradigm.

Is there a specific “timing of mineralization” in gold deposits?

Is there a specific “timing of mineralization” in gold deposits?

Nature and Mode of Occurrences of the Gold Mineralisation in and around Sindauri-Ghanshyampur Area of North Singhbhum Mobile Belt, Singhbhum Crustal Province, Eastern India

ABSTRACT Palaeo- to Mesoproterozoic North Singhbhum Mobile Belt (NSMB) within the North Singhbhum Crustal Province (NSCP) is a metallogenic province, well known for many gold occurrences within the phyllite intercalated with quartzite unit of the Singhbhum Group. The present study has been conducted in and around the Sindauri-Ghanshyampur area, within the Singhbhum Group of rocks, lying along the northern boundary of the Dalma volcano-sedimentary belt of NSMB. The gold mineralisation within the Sindauri-Ghanshyampur area is limited to the quartz veins and veinlets intruded into the phyllite and intercalated quartzite along the east-northeast trending Lungtu-Parasi-Sindauri shear zone. The anomalous gold values within the area are reported from quartz/carbonate veins and veinlets, which are parallel to the S2 foliation along the Lungtu-Parasi-Sindauri shear zone. Gold occurs in association with arsenopyrite, pyrrhotite and pyrites. However, at places, it also occurs as isolated specks. The shearing within the Sindauri-Ghanshyampur area is evident by the mylonitisation within the tuffaceous phyllite intercalated with the quartzite. Shear zones act as a conduit for hydrothermal fluid migration. The present study is the first report of gold deposits within the Sindauri-Ghanshyampur area in Ranchi District, Jharkhand, explored by the Geological Survey of India (GSI). Based on the gold assay results of core samples of boreholes SEB-6 to 10, a total of 1.147 million tons of Inferred Mineral Resource with an average grade of 1.030 ppm were calculated. From borehole SEB-12, the total estimated resource for Au is 0.767 million tonnes with an average grade of 0.81 g/t. The nature and the mode of occurrence of gold mineralisation within the Sindauri area indicate that the gold mineralisation is of orogenic type. Gold was deposited by the hydrothermal fluid to form an epigenetic gold deposit along the S2 foliation and shear planes.

Complex fluid-rock interaction and fluid fluctuation in the Jiaodong hydrothermal gold system (North China) revealed by mineral and geochemical analyses of quartz

The formation of hydrothermal gold deposits commonly involves complex fluid-fluid and fluid-rock interaction processes. Here, we investigated the micro-texture and in situ trace elemental and oxygen isotopic composition of different quartz from the Zhaoxian gold deposit, Jiaodong, North China, aiming to constrain the evolution and origin of ore-forming fluids under the complex hydrothermal process. Crosscutting relationships and cathodoluminescence (CL) zoning reveal four discrete quartz generations (Qtz-1 to Qtz-4) corresponding to four distinct vein-filling stages (V1−V4) in the hydrothermal system. The CL lightness of quartz shows a positive correlation with Al content but no relationship with δ18O values, suggesting different controls on trace element incorporation versus oxygen isotope fractionation. The elevated content of trace elements in hydrothermal quartz (such as Al, up to 916 ppm in Qtz-2) is ascribed to water-rock interaction, which increased lithophile-element availability. The seism-induced fluid fluctuation enhanced quartz compositional variability via influencing chemical composition and pH value of hydrothermal fluids. The four quartz generations exhibit distinct δ18O values: Qtz-1 (11.35‰−11.63‰), Qtz-2 (12.46‰−15.07‰), Qtz-3 (12.68‰−14.56‰), and Qtz-4 (13.03‰−14.47‰). Calculated δ18O values of corresponding fluids are 4.46‰−4.74‰, 4.20‰−6.96‰, 2.63‰−4.25‰, and −2.46‰ to −1.02‰ for stage I to stage IV, respectively. The O isotopic compositions of ore-forming fluids were negatively shifted by water-rock reaction. Meanwhile, the nearly constant δ18O values at the mineral scale indicate persistent isotopic compositions of pore fluids due to rock buffering, despite fluid fluctuations. The hydrothermal fluids were initially mantle-derived (δ18O ≥7‰) with incorporation of meteoric water in the post-ore stage. The textural and geochemical signatures of quartz serve as effective tracers for constraining water-rock interaction intensities and fluid fluctuations in hydrothermal gold mineralization systems.

Ambient noise tomography reveals deep ore-forming structures of shear zone-type gold deposits at Dongchuan, Yunnan Province, China

Ambient noise tomography reveals deep ore-forming structures of shear zone-type gold deposits at Dongchuan, Yunnan Province, China

Discrete Paleoproterozoic and Cretaceous mineralization events at the Liyuan gold deposit, central North China Craton

Discrete Paleoproterozoic and Cretaceous mineralization events at the Liyuan gold deposit, central North China Craton

Mineralization processes in the Suoluogou orogenic gold deposit, Sichuan Province, China: evidence from Au occurrence and trace elements

Mineralization processes in the Suoluogou orogenic gold deposit, Sichuan Province, China: evidence from Au occurrence and trace elements

Geological characteristics, fluid inclusion, and isotope systematics of the Zhongshangou gold deposit, northern margin of the North China Craton: A comparative study with the Dongping deposit and implications for regional mineralization

Geological characteristics, fluid inclusion, and isotope systematics of the Zhongshangou gold deposit, northern margin of the North China Craton: A comparative study with the Dongping deposit and implications for regional mineralization

Perkins Discontinuities: structurally controlled grade patterns diagnostic of epigenetic gold mineralisation at the deposit-scale

This study establishes a robust methodology using raw, desurveyed. uninterpolated drill-sampled 3D-grade data to identify superposed structural symmetries and determine mineralisation timing at the deposit-scale. This methodology has transformative implications for exploration and resource estimation of gold and other structurally controlled commodities. We introduce the concept of Perkins Discontinuities—planar boundaries that abruptly terminate mineralisation continuity, creating asymmetric grade distributions. These features , including fractures, low-displacement faults, veins, dykes or intrusions—define asymmetric mineralisation patterns unrelated to fault displacement. Such asymmetry arises from minor permeability contrasts across fractures intersecting the primary tectonic grains defined by fold axes. Our ‘outside-in’, deposit-scale structural analysis of drill-sampled assay-grade data from five well-established epigenetic gold deposits—Ballarat East (Victorian goldfields), Exodus (Carlin Trend), Bronzewing, Aphrodite from the Bardoc Tectonic Zone and Coolgardie (Yilgarn Craton)—reveals two key structural symmetry axes. A quasi-cylindrical axial symmetry (Axis 1) that parallels early shear zones and folds, while oblique Perkins Discontinuities define a later superposed axial symmetry (Axis 2). If Axis 1 and Axis 2 are parallel, gold mineralisation timing coincides at earliest with the first ductile deformation (syn-folding), although a later timing remains possible. Conversely, if Axis 2 is oblique to Axis 1, mineralisation must post-date folding and fracturing, ruling out syngenetic or syn-fold origins proposed by orogenic shear-zone gold models. Applying this approach to three deposits classified as syngenetic—Haile (South Carolina), Chelopech (Bulgaria) and Vaal Reef (Witwatersrand Basin, South Africa)—demonstrates their epigenetic nature. Using Fast Lagrangian Analysis of Continua finite difference modelling of Darcy fluid flow, we show upward-flowing fluids converge towards antiform apices and diverge from synforms, explaining the prevalence of orogenic gold in antiformal saddle reefs and scarcity in synformal trough reefs. A similar process may occur where fracture networks converge in an A-shaped geometry, as at Chelopech. Recognising Perkins Discontinuities and integrating their geometry with deposit-scale grade data redefines gold emplacement timing as late-orogenic in many goldfields, challenging both crustal-scale shear-zone models of orogenic gold emplacement and syngenetic classifications. This refined structural and fluid-flow framework impacts exploration targeting and resource estimation by highlighting post-fold and post-fracture controls on gold localisation, reshaping our understanding of major gold deposit formation.

Improvement of blasting technology at gold-ore mining enterprises using contour blasting

Purpose. The research purpose is to develop and substantiate recommendations for improving the technology of drilling-blasting operations in open-pit mining of gold-ore deposits. The research is aimed at optimizing the drilling-blasting process parameters taking into account physical-mechanical properties of rocks, conditions of ore mass occurrence and requirements for the quality of rock mass crushing. Methods. Qualitative and quantitative analysis methods are used for the research. The compliance of the drilling-blasting technology with the design solutions is assessed, and the actual condition of the quarry benches and near-wall mass after blasting is analyzed. A numerical model describing the influence of contour blasthole charges on the near-wall mass has been developed, taking into account the parameters of the bench height and charge diameter. Particular attention is paid to the development of recommendations for improving the quality of ore mass breaking, decreasing dilution and reducing the near-wall mass breaking. The effectiveness of the proposed solutions is confirmed by conducting a series of test blasts with subsequent assessment of their results. Findings. The research results have shown that the existing parameters of drilling-blasting operations at the Pustynnoye Mine do not fully comply with the mining-technical conditions, which leads to inconsistency with the design slope angles and dilution of rock mass. Implementation of the presplitting method and optimization of charge parameters make it possible to improve the quality of mass breaking and reduce the seismic impact. The resulting dependences will help to accurately select blast parameters, improving the efficiency of drilling-blasting operations. Originality. The novelty is in the development and implementation of an integrated approach to the optimization of drilling-blasting operations at the Pustynnoye Mine. The research has identified the optimal parameters, including blasthole diameters, charges for splitting, explosive density and stemming material granulometric composition. Practical implications. Implementation of the proposed methods will increase the efficiency of drilling-blasting operations, improve rock mass crushing, stabilize slopes and reduce seismic impact on the near-wall mass. Optimizing parameters such as blasthole diameters, specific explosive consumption and charge densities will reduce costs while maintaining efficiency. The developed passports of drilling-blasting operations will help to adapt the processes to changing conditions and ensure the safety and accuracy of mineral extraction.

U-Pb calcite geochronology indicates episodic amagmatic free-convection over tens of millions of years in Carlin-type gold deposits

U-Pb calcite geochronology indicates episodic amagmatic free-convection over tens of millions of years in Carlin-type gold deposits

Ore Genesis of the Jurassic Granite-Hosted Naizhigou Gold Deposit in the Jiapigou District of Northeast China: Constraints from Fluid Inclusions and H–O–S Isotopes

The Jiapigou mining district (>180 t Au) is an important gold district in China. For a long time, the ore genesis of the gold deposits in the Jiapigou district has been a subject of controversy and differing opinions, which has severely hindered metallogenic theories and mineral exploration. Here we present a comprehensive investigation including geology, fluid inclusions (FIs), and H–O–S isotopic data for the Naizhigou deposit in the Jiapigou district to elucidate the sources of orefluids and metals, as well as the metallogenic mechanism. The results show the following: (1) The Naizhigou deposit is characterized by quartz vein-type ores and is hosted in the Middle Jurassic granitic pluton. Native gold and sulfides were mainly deposited in the second stage (quartz–polymetallic sulfides) compared with the first (quartz–pyrite–molybdenite) and third (quartz–calcite) stages. (2) The FI studies indicated that the orefluids evolved from the early–main-stage CO2–H2O–NaCl system to the late-stage H2O–NaCl system and have homogenization temperatures of 289–363, 210–282, and 124–276 °C and salinities of 4.1–20.9, 5.8–16.4, and 6.1–12.7 wt% NaCl equivalent, respectively. Fluid boiling and fluid mixing collectively controlled the precipitation of gold and ore-forming elements. (3) The δD values of the FIs hosted in quartz from the three stags range from −81 to −75 ‰, from −99 to −86 ‰, and from −110 to −101 ‰, while δ18Owater values of these FIs range from 5.3 to 5.9 ‰, from 1.1 to 5.2 ‰, and from −2.1 to −0.7 ‰, respectively. Pyrite samples from the three stages in the Naizhigou deposit have δ34S values of 2.1 to 2.5 ‰, 3.1 to 4.3 ‰, and 3.8 to 3.9 ‰, respectively. The stable isotopes indicate that the orefluids and metals mainly originated from magma. A comparative study of regional observations reveals that the Naizhigou deposit is a magmatic-related mesothermal gold deposit, rather than a metamorphism-related orogenic gold deposit. The estimated ore-forming depths are 4.0–20.7 km, with exhumation depths of 4.1–5.5 km, which indicated that the deposit has been well preserved. Regionally, the new exploration strategies should place greater emphasis on work concerning ore-related plutons, ore-controlling faults, and hydrothermal alteration.

Техногенные россыпи золота и проблема их освоения на примере Дальневосточного региона

The article provides a description of technogenic gold placers within the Far East region. The ability of ore elements to migrate and the process of formation of electrochemical fields as well as, various barrier phenomena with gold deposition on them are presented. A new method for the rapid assessment of the prospects of technogenic placers using electrochemical, geochemical, and geophysical methods is proposed, which significantly reduces the time and cost of work.

Why gold deposits are not caused by fluids from the mantle

Any model invoking gold fluids coming through crustal rocks at granulite facies grade or coming from the mantle is built on a misunderstanding of the way aqueous fluids interact with rocks at high temperature, above their solidus. It is not currently explained in such models how aqueous fluids pass through rocks at granulite facies grade without being involved in melting. At temperatures above 650–750 °C, crustal rocks melt in the presence of an aqueous fluid with the latter being consumed, the amount of melt generally being proportional to the amount of fluid involved. This means auriferous hydrothermal fluids are unable to infiltrate hot lower crust from the mantle. An alternative model exists that avoids this problem, at least for typical gold-only deposits, for example Kalgoorlie. It involves fluid generation by metamorphic devolatilisation in the mid-crust at the greenschist–amphibolite facies transition, at around 450 °C. This process generates significant volumes of aqueous fluid during prograde metamorphism. In the presence of carbonate and sulfide minerals, the resulting fluid is H2O–CO2–H2S dominated by low salinity, a composition conducive to gold dissolution. A strength of this model is that the fluid will become gold-bearing as it is generated. As more or less all mineral grains in the rock are involved in the devolatilisation, gold present at parts-per-billion level in grains as well as on grain boundaries is accessible to the fluid.