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The controversial topic of genetic relationships of shallow magmatogenic ore deposits with associated complexes of small intrusive bodies or separate syn-ore bodies is discussed in this article. Materials of the field study by the authors of four epithermal gold deposits of the Amur region are used. These materials are supplemented by an analysis of published data on the conditions and geological settings of the localization of a number of other epithermal and shallow Cu-Mo-porphyry deposits in various regions of Russia and other countries. The active thermal participation signs of syn-ore stocks and sill in retraction to intrusions and initiation of near-intrusive convection of deep-seated fluids during ore formation at epithermal gold deposits of the Amur region (Pokrovskoe, Pioner, Zheltunak, Bamskoe, and Mnogovershinnoe) have been established and confirmed by model experiments. These signs and zoning of metal deposition are also established at epithermal and porphyry deposits in other regions of Russia (Ural, Transbaikalia, and Kamchatka) and in other countries. Favorable conditions for ore accumulations have been identified. These conditions are associated with shallow syn-ore small intrusions and magma chambers at 11 characteristic deposits, including large and unique ones (Pioner, Mnogovershinnoe, Bingham, and Klaimax). [ABSTRACT FROM AUTHOR]

The research site includes part of the East Asian region within areas of South‐East Russia and the boundary part of North‐East China. The region has abundant precious metal deposits: gold and platinum group elements. The spatial distribution of these deposits is controlled by details of crustal and mantle geodynamics including the presence of faults of different types and kinematics, active plume, as well as by the position of the region above a stagnant oceanic slab. Spatial analysis of position, geodynamics, and synchronous formation of the largest East Asian gold districts (e.g., Aldan, Baley, and Jiaodong) and platinum‐bearing massifs provide insights to their connection with mantle plumes and permeable zones at stagnant slabmargins. The occurrence of ore deposits and mineralization of precious metals inside the slab area is related to disjunctive structures of lower crust and upper mantle, such that their resources are considerably lower. This article considers numerical modeling of permeable tectonic structures exposed into mantle upwelling along active continental margins inside the slab area. Small‐scale structures of this type potentially hold two‐phase alkaline massifs, which control the positions of intra‐slab ore deposits, like the Lazurnoe Au–Mo–Cu porphyry deposit, situated in the southern part of the Sikhote–Alin belt. The small sizes of similar massifs impede their discovery, emphasizing the importance of the proposed prospective model for precious metal‐bearing porphyry deposits in Western Pacific mobile belts. [ABSTRACT FROM AUTHOR]

The Late Albian–Early Cenomanian epoch of Au-Cu porphyry ore mineralization has been distinguished within the Sikhote-Alin. The development of ore mineralization is associated with Albian–Cenomanian granitoids, synchronous to syn-strike-slip orogenesis and the formation of the continental lithosphere in the setting of transform continental margins. The development of Au–Mo–Cu and Cu–Au–W types of ore mineralization in the terrains of the Jurassic accretionary prism and the Early Cretaceous terrain of the epioceanic turbidite basin, correspondingly, was induced with the mantle–crustal synorogenic intrusions of granitoids. The U–Pb zircon dates (100–95 Ma, Albian–Cenomanian) of Au–Cu porphyry Malmyzh granitoids are given for the first time. The similar data available on the age of granitoids in Eastern and Southeastern Asia, which are associated with plutonogenic–hydrothermal deposits of Cu, Au, Sn and other metals, allow us to suggest that there is an Albian–Cenomanian metallogenic megabelt extending along the entire Pacific continental margin of Asia. [ABSTRACT FROM AUTHOR]

[Display omitted] • From 1991 to 2021, Russia produced about 7.5% of total world gold production. • During 30 years, Russian gold production increased 2.3 times vs world's 1.65 times. • In 1991, placers contributed 79.2 % of 143.1 t of Russian gold. • In 2021, the share of placer gold was 24 % from total of 331.1 t. • Hardrock gold production from all sources increased 7.3 times from 34.3 t (in 1991) to 250.9 t (in 2021), with structural change in sources. From 1991 to 2021, Russia produced nearly 6,500 t (209 million ounces) of gold, about 7.5 % of the total world production from a territory equivalent to 11 % of the landmass. Russian gold production increased faster than that of the rest of the world (2.3 times vs 1.65 times). Russian gold was extracted from >100 hardrock deposits and numerous placers in eastern Siberia, Far East and the Urals. The hardrock sources included epithermal, orogenic, Carlin-like(?) and intrusion-related types, with gold as the principal metal. By-product gold was extracted from Cu-Fe skarn, Cu-Zn VMS, magmatic Ni-Cu-PGE sulphide, and recently developed porphyry Cu deposit types. In 1991, placers contributed 79.2 % of 143.1 t of Russian gold. In 2021, their share had decreased to 24 % from the total of 331.1 t Au, approximately 30 % less than in 1991. The most dramatic change was in gold production from hardrock deposits, with a 7.3 times increase from 34.3 t (in 1991) to 250.9 t (in 2021). [ABSTRACT FROM AUTHOR]

There have been multiple occurrences in the literature in the past several years of what has been referred to as the induced polarisation (IP) effect in airborne time domain electromagnetic (TDEM) data. This phenomenon is known to be responsible for incorrect inversion modelling of electrical resistivity, lower interpreted depth of investigation (DOI) and lost information about chargeability of the subsurface and other valuable parameters. Historically, there have been many suggestions to account for the IP effect using the Cole-Cole model. It has been previously demonstrated that the Cole-Cole model can be effective in modelling synthetic TDEM transients. In the current paper we show the possibility of extracting IP information from airborne TDEM data using this same concept, including inverse modelling of chargeability from TDEM data collected by VTEM, with field examples from Canada (Mt Milligan deposit) and Russia (Amakinskaya kimberlite pipe). [ABSTRACT FROM AUTHOR]

[Display omitted] • Whole-rock (Sr/Y)/Y and 100[(Rb/Sr)/FeO*] ratios as skarn and porphyry fertility indicators. • Whole-rock Sr/Y ratios of > 65 and 10,000*(Eu/Eu*)/Y ratios of > 850 as porphyry fertility indicators. • Whole-rock Sr/Y ratios of > 35 and 10,000*(Eu/Eu*)/Y ratios of > 450 as skarn fertility indicators. Identifying new whole-rock geochemical fertility indicators for porphyry and skarn productive systems is a geological challenge due to a large variety of tectonic settings, magmatic source regions and petrological evolution of the parental intrusions. This is especially true for non-porphyry-related Cu-Au-Fe skarns for which no relevant whole rock or chemical mineral indicators are currently recorded. Our study provides high‐precision whole‐rock data of granitoids from the Kultuma Cu-Au-Fe skarn deposit in Eastern Transbaikalia, Russia, in order to define productive skarn suites. The Kultuma Cu-Au-Fe skarn deposit consists of two contemporaneous (dated at ca. 159–161 Ma and 157–158 Ma using U-Pb methods) pulses of mineralized high-calc-alkaline to shoshonitic I-type granites that were emplaced during the final stage of collision following the closure of the Mongol–Okhotsk ocean. Igneous suites of both skarn-related pulses are high-K (3–5 wt% K 2 O) and range in composition from low-silica and high-magnesian monzonite porphyries to high-silica and high- to moderate-magnesian quartz‐syenite and granite porphyries. They originated from moderately oxidized (zircon Eu/Eu* = avg. 0.24 and ΔFMQ = avg. + 0.4 to + 0.6), moderately hydrous (whole-rock Sr/Y = 40–64; zircon Yb/Dy = avg. 3.6), low to moderately fractionated (whole-rock Eu/Eu* = avg. 0.86) magmas that evolved through substantial interaction with the lower crust (whole-rock La/Yb = 24–54, (Dy/Yb) CN = 1.4–2.0, Yb = 0.5–1.2 ppm) followed by deep-level amphibole and shallow-level plagioclase fractionation, respectively. Based on a comprehensive set of new whole‐rock data, we propose the use of (Sr/Y)/Y and 100[(Rb/Sr)/FeO*] ratios to discriminate between fertile non-porphyry-related skarn and porphyry and porphyry-related skarn suites and unmineralized granite intrusions. Our proposed new discrimination thresholds of (Sr/Y)/Y and 100[(Rb/Sr)/FeO*] are effective in Eastern Transbaikalia, but they could potentially be useful for the geochemical discrimination between intrusions prospective for Cu-Mo-Au-Fe skarn and porphyry mineralization and barren calc‐alkaline granitic suites in other arc‐related mineral belts worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • The early Paleozoic Julia deposit comprises oxidized-type, garnet-dominant skarn with bornite and chalcopyrite followed by quartz-carbonate-sulfide veins with Cu-Au-Bi-Te mineralization. • The deposit is related to a post-collisional high-K calc-alkaline to shoshonitic igneous suite. • U-Pb zircon data indicate the Late Cambrian age of causative igneous rocks. • Long-lasting (20 m.y) magmatic evolution culminated in rapid emplacement (5 m.y.) of mineralizing intrusions. The small but high-grade (average 1.29% to 2.04% Cu and 0.09–0.12% Mo for different orebodies, with also significant Au contents) Julia skarn Cu-Au-Mo deposit is situated some 30 km northeast from the Sorskoe porphyry Mo-Cu deposit in the Kuznetsk Alatau, a Paleozoic terrane in the northernmost part of the Altai-Sayan orogenic system, part of the Central Asian Orogenic Belt. The deposit comprises prograde calcic skarns and later retrograde skarn characterized by abundant andradite-rich garnet defining their oxidized type. These alteration assemblages bear abundant Cu sulfides (chalcopyrite and bornite), which are associated with magnetite and are partially overprinted by weak propylitic and stronger phyllic (carbonate-phyllic) alteration assemblages. Molybdenite is present in these assemblages, and various sulfides and sulfosalts, tellurides, and Bi minerals, as well as native Au are associated with phyllic alteration. The deposit is related to a magnetite-series, I-type, multiphase monzonite-syenite(-quartz syenite)-quartz monzonite-monzogranite igneous complex. Isotopic U-Pb zircon data indicate a Late Cambrian age (∼505 to 485 Ma) of the igneous rocks, whereas their geochemical signatures correspond to high-K calc-alkaline to shoshonitic intrusions emplaced in a post-collisional environment, with possible relationships to a subducted slab break-off. Magmatic evolution included a generation of shoshonitic magma by a low-degree partial melting of the metasomatically-enriched upper mantle, followed by amphibole fractionation in a deep (lower crustal?) magma chamber and then by magma fractionation and emplacement at shallower crustal levels. Although the overall magmatic evolution of the parental intrusions was long-lasting (ca. 20 m.y.), the mineralization is associated with a relatively rapid (ca. 5 m.y.) emplacement of more differentiated granitoid intrusions as well as late mafic dikes. The deposit represents an early Paleozoic (Late Cambrian) Cu-Au(-Mo) mineralization in the Altai-Sayan orogenic system and the broader Central Asian Orogenic Belt, thus confirming the Late Cambrian (to Early Ordovician) Cu-Au-Mo metallogenic event in the region. This, together with the broad regional occurrence of the Cambrian-Early Ordovician igneous complexes and related porphyry/skarn Cu-Au(-Mo) mineralization, emphasizes the early Paleozoic porphyries/skarns as a major regional event prior to much better known late Paleozoic porphyries/skarns in the Central Asian Orogenic Belt. There is a potential of the early Paleozoic terranes to host much more significant Cu-Au(-Mo) mineralization including that of skarn, porphyry and associated types. [ABSTRACT FROM AUTHOR]

The origin and geodynamic settings of the Ust'-Sema Formation and the Barangol Complex are some of the most controversial issues in the Early Paleozoic history of the Altai–Sayan Fold Belt. The Ust'-Sema Formation volcanic rocks are enriched in high-Ca clinopyroxene phenocrysts and were classified as ankaramites and diopside porphyry basalts. In this work, we first present LA-ICP-MS analyses of the clinopyroxenes, along with studies of the petrography, mineral composition, and whole-rock chemistry of the Ust'-Sema Formation and related Barangol Complex rocks. An LA-ICP-MS clinopyroxene study showed a slight depletion of light rare-earth elements (La/Yb)N = 0.1–1.0 (on average 0.4); and strong depletion of the high-field-strength elements (Zr, Hf, and Nb) and large-ion lithophile (Rb) elements. An Sr anomaly showed a positive correlation with Mg#. Major- and trace-element composition of the clinopyroxene cores show that these clinopyroxene grains were not captured from the mantle rocks as previously assumed and that the Ust'-Sema Formation and the Barangol Complex rocks were formed from magma with island arc characteristics. The increased titanium and light rare-earth element contents in the phenocryst rims from Biyka volcano suggest an active interaction of the ankaramitic magma with rocks or melts of OIB type. [ABSTRACT FROM AUTHOR]

The Novogodnee-Monto oxidized Au-(Cu) skarn and porphyry deposit is situated in the large metallogenic belt of magnetite skarn and Cu-Au porphyry deposits formed along the Devonian-Carboniferous Urals orogen. The deposit area incorporates nearly contemporaneous Middle-Late Devonian to Late Devonian-Early Carboniferous calc-alkaline (gabbro to diorite) and potassic (monzogabbro, monzodiorite- to monzonite-porphyry, also lamprophyres) intrusive suites. The deposit is represented by magnetite skarn overprinted by amphibole-chlorite-epidote-quartz-albite and then sericite-quartz-carbonate assemblages bearing Au-sulfide mineralization. This mineralization includes early high-fineness (900-990 ‰) native Au associated mostly with cobaltite as well as with chalcopyrite and Co-pyrite, intermediate-stage native Au (fineness 830-860 ‰) associated mostly with galena, and late native Au (760-830 ‰) associated with Te minerals. Fluid inclusion and stable isotope data indicate an involvement of magmatic-hydrothermal high-salinity (>20 wt.% NaCl-equiv.) chloride fluids. The potassic igneous suite may have directly sourced fluids, metals, and/or sulfur. The abundance of Au mineralization is consistent with the oxidized character of the system, and its association with Co-sulfides suggests elevated sulfur fugacity. [ABSTRACT FROM AUTHOR]

The article investigates the upper as well as lower age boundaries of the middle riphean (Ti-Fe-V) intrusions of the Kusinsko-kopanskii Complex in the South Urals. It mentions that Medvedevskoe Fe-Ti deposit is composed of rocks of old rhythmic layer complex consisting of stratified ore melanocratic and barren leucocratic amphibole gabbro, giant-granular gabbro, anorthosite etc. Findings of study done on anorthosite and porphyry granite rocks are also discussed. Also mentioned is the total age range between both the boundaries that is 30-40 Ma and age of sediment diagenesis for the Satkinskaya Suite and metasomatic formations which includes magnesite and phosphorite.

The concentrations of platinum-group elements (PGE) have been analyzed in primary magmatic magnetite samples from the Zhireken, Shakhtama and Aksug porphyry Cu-Mo deposits (Siberia, Russia) by laser ablation-inductively coupled plasma mass spectrometry to determine the range of PGE contents in magnetites and to check whether magnetite from two main rock suites (barren plutonic suite and mineralized porphyry suite) has distinct PGE composition. The results presented here indicate that magnetites are enriched in PGE relative to whole-rocks. Comparison of ore-related porphyry and barren plutonic suites shows that magnetite exhibit relatively similar PGE distribution patterns in both suites. Variations in Rh and Ru contents were controlled by the oxygen fugacity during magma crystallization. [ABSTRACT FROM AUTHOR]

The article discusses the gold-bearing potential and geological-structural characteristics of the Amur Province's Lower Selemdzha cluster in Russia. It states that gold mineralization creates paragenesis with dikes of dioritic porphyrites, porphyries, and granite of the Lower Cretaceous Burinda complex. It says that the Lower Selemdzha cluster is near to gold-polymetallic and gold-ore deposits in the province. It mentions that the gold fineness in the Lower Selemdzha cluster's placers varies from 810% to 950% and gold particles have several shapes including crystalline, platy, and clotty.

Rhenium is one of the rarest elements of the earth crust (abundance ratio 0.7 mg/t). In the Karelian region, Re and accompanying Os were discovered in a copper-molybdenum-porphyry ore formation, represented by the Lobash deposit, the Jalonvaara occurrences etc., and in a noble-metal-Cu-U-vanadium ore formation (Padma Group occurrences). Molybdenites from the above deposits are enriched in Re and Os (Lobash: 13–187 g/t Re, 0.4–6 g/t Os). So far, however, no rhenium minerals proper have been revealed in the Karelian deposits and occurrences of the above formations or elsewhere. As a result of the microprobe study of mineral assemblages of cupreous sandstones from the Voronov Bor deposit (bornite ore) and sulphide-copper-nickel ore from the Rybozero deposit, osmium-cupreous rheniite (Re, Cu, Os, Fe)1S2 that contains 56.53–60.25% Re, 4.61–10.99% Cu, 1.52–3.77% Os and up to 4.75% Fe was revealed and studied for the first time. [ABSTRACT FROM AUTHOR]

The article offers information on the new model of thermal and physicochemical dynamics for volcanogenic epithermal deposits in Asacha deposit located in Kamchatka, Russia. It reveals the features of volcanogenic porphyry deposits especially the thermal loss into wall rocks and emphasizes the determining factor in heterophase mass transfer of components. Moreover, it discusses the potential of the Gibbs or Helmholtz thermodynamics to minimization which shows the ability of the ore-bearing fluids to form substantially different types of ore desposits. It presents the basic features of the mineralogical zoning in the areas of fluid and estimates some spatial time parameters.

Darasun, Teremkyn, and Talatui are neighboring deposits in the Darasun gold district of Transbaikalia (Russia) that are hosted by Middle-Late Jurassic subduction-related porphyry intrusions and dikes. Darason consists of vertically extensive, steeply dipping Au mineralized veins and zones, spatially related to a K-rich granodiorite-porphyry intrusion, within the deposit are also pipelike bodies of tourmaline sulfide hydrothermal breccias. Teremkyn consists of gently and steeply dipping veins and zones, always associated with felsic dikes comagmatic with the Darasun intrusion. Talatui consists of variably shaped mineralized zones systematically associated with dikes of different compositions and with the host Middle-Late Jurassic granite porphyry. A large proportion of both veins and mineralized zones in these deposits consists of sulfide and oxide minerals, with pyrite and arsenopyrite mostly present at Darasun and Teremkyn and pyrite, magnetite, and hematite present at Talaui. The three deposits host also a large number of sulfosalt, bismuth, oxide, and telluride minerals. Gold of variable purity occurs as free nuggets or hosted by opaque phases. The gangue mineralogy, is similar in the three deposits and includes commonly quartz, tourmaline, and calcite. Microthermometry and microchemical analyses of fluid inclusions with petrographic and compositional data on ore minerals constrain the stages of ore deposition in the district. At room temperature, the entrapped fluids are of four compositional types: (1) multiphase, with a vapor bubble, liquid, and one or more solids; (2) liquid-vapor aqueous; (3a) vapor-rich with a small proportion of liquid and rare solids, and also (3b) vapor-rich with a small proportion of aqueous liquid and carbonic liquid. Types (1) and (3) or (2) and (3) coexist within the same assemblages and are present mostly in paragenetically early quartz, whereas the type (2) fluid within later quartz, sphalerite, and calcite shows consistent phase proportions. At Darasun and Teremkyn, type (2) fluid is the main ore fluid, but all fluid types are associated with gold deposition at Talatui. Microthermometric measurements from all fluid types show a range of phase transitions that vary systematically at the deposit scale. At Darasun and Teremkyn, coexisting types (1) and (3) and types (2) and (3) homogenize into the vapor and liquid states, respectively, within the same 290° to 460°C range. The corresponding bulk salinities vary between 0.7 and 44.8 wt percent NaCl equiv. In contrast, at Talatui coexisting types (1) and (3) and types (2) and (3) homogenize into the vapor and liquid phases and show a distribution of Th(total) and bulk salinities between about 300° and 610°C and 0.9 and 48 wt % NaCl equiv, respectively, Mass spectrometric and chromatographic data from bulk samples show that the main-stage orefluid in the three deposits varies compositionally according to location within the district. In detail, Cl, Na, K, Cs, Br, Sr, Rb, Mn, and Tl are relatively enriched in the Talatui fluid, whereas CO2, CH4, HCO, Cu, Pb, Sb, Fe, Hg, and REE are enriched at Darasun and Teremkyn or show no systematic variations. Au concentrations vary within the 0.01-to 3-g/t range at Darasun and Teremkyn, whereas at Talatui values do not exceed 0.4 g/t. The salinities and homogenization temperatures of the main-stage ore fluids types (1), (2), and (3) are typical of the intrusion-related class of gold deposits. This suggests a dominant magmatic component of the ore fluid during the first stages of mineral precipitation and a magmatic derivation of gold itself in the district. Phase separation was active during the early stages of ore deposition and took place between about 600° to 400°C at Talatui and 450° to 300°C at Teremkyn and Darasun at pressures of 10 to 160 MPa (i.e., 1- to 2.5-km depth).… [ABSTRACT FROM AUTHOR]

The article offers information on the geochemical and samarium-neodymium (Sm-Nd) isotope study of the petrogenic relationship of mafic and felsic rocks at the Sora porphyry copper-molybdenum (Cu-Mo) deposit in Kuznetsk Alatau at the northern region of Uibat pluton in Russia. The study revealed an evidence of leucogranite and ore-bearing porphyries formations as a result of partial melting of preceding basites. Further, the study has allowed the authors an estimation on the functions of basic and acid magmas in the formation of ore potential of the Sora magmatic center.

[Display omitted] • The Bystrinsky and Shakhtama deposits are hosted by high-K calc-alkaline intrusions. • Both fertile and non-fertile porphyries show adakitic geochemical signatures. • Porphyries hosting the Shakhtama deposit are more evolved than those at Bystrinsky. • Whole-rock Sr/Y and 10,000*(Eu/Eu*)/Y are fertility indicators on the regional scale. • Zircon Eu/Eu*, Ce/Ce* and Yb/Dy are fertility indicators on the prospect scale. • New MS Excel-based software is developed for calculating the Ce anomalies of zircons. The Bystrinsky Cu-Au-Fe porphyry-skarn and Shakhtama Mo ± Cu porphyry deposits in Eastern Transbaikalia, Russia, are spatially associated with a series of fertile and non-fertile calc-alkaline to shoshonitic I-type granitoid suites, ranging in composition from porphyritic monzonites and granodiorites to granodiorite- and granite-porphyries. The obtained zircon U-Pb geochronological data reveal a narrow age interval of 1–3 Ma for the igneous suites within the Bystrinsky deposit (ca. 159–163 Ma), which is consistent with the short-magmatic activity at the Shakhtama deposit (ca. 164–161 Ma). Within both deposits, the fertile magmatic pulses comprise hybrid, high-silica and high- to moderate-magnesian, oxidized melts with relatively high magmatic water contents. These weakly fractionated melts represent the late-stage magmatic pulses of the Shakhtama Complex. By contrast, the barren magmatic pulses comprise a wide range of compositions, generally with lower magmatic water contents and oxidation states as well as significant plagioclase fractionation and crustal contamination. The Shakhtama Mo-related porphyries are more evolved when compared to the Bystrinsky Cu-Au intrusions reflecting significant crustal assimilation in addition to amphibole-plagioclase fractionation. Both whole-rock geochemistry and zircon mineral chemistry from the Bystrinsky and Shakhtama deposits may be used as fertility indicators in target generation and regional mineral exploration in Eastern Transbaikalia. More specifically, we propose critical thresholds of whole-rock Sr/Y and 10,000*(Eu/Eu*)/Y ratios of > 65 and > 850, respectively, and zircon mineral Eu/Eu*, Ce/Ce* and Yb/Dy ratios of > 0.4, >750 and > 4, respectively. Additionally, we propose an alternative method to calculating the Ce anomalies of zircons using MS Excel-based software which is provided in the Supplementary data of this paper. [ABSTRACT FROM AUTHOR]

• In placer weakly rounded native gold is significantly present or prevails. • The placer native gold can be divided into 3 types and 1 subtype. • The Cu-bearing native gold can be compare with the porphyry-skarn deposits. • The Hg-bearing placer gold can be link to the eroded levels of the Bystrinsky deposit. Eastern Transbaikalia is one of the oldest gold-producing regions in Siberia, and for over 300 years it has been the largest source of the most important raw minerals in Russia. A large number of gold, gold-bearing complex, antimony, mercury and other mineral deposits are known within this region. The orogenic, intrusion-related, and epithermal deposits are important in the balance of gold reserves and gold production. Au-Cu-Fe-skarn deposits are located mainly in the northeastern and southeastern parts of the area, wherein the skarn Kultuma, Lugokan, and skarn- porphyry Bystrinsky deposits are the largest deposits. Herein, we studied the the Bystraya River gold placers and tributaries, which are located to the east of the Bystrinsky massif near the Bystrinsky deposit. In this study, a microchemical characterization technique was applied to gold grains to facilitate the classification of alluvial gold localities in terms of the style or styles of source mineralization, thereby permitting a comprehensive interpretation of regional gold mineralization. In total, 55 samples were collected from four placers and processed for more than 1500 analyses of the native gold. In the alluvial placers of the Bystrinsky deposit areas, weakly rounded native gold either prevails or is significantly present. A low portion of supergenically transformed of gold grains in the placers indicates that the placers formed directly from endogenous gold mineralization. The native gold from the Bystraya River catchment can be divided into 3 types and 1 subtype: (1) Cu-bearing gold grains with a fineness of 800 − 995‰, and a copper impurity of up to 0.73%; (2) Hg-bearing gold grains with a fineness of 800 − 995‰, and an impurity of Hg up to 4.68%; (2.1) Hg-poor gold grains with a fineness of 800 − 995‰, containing the same mineral microinclusions assemblages as the Type 2 gold grains; and (3) gold with a fineness of 400 − 770‰, containing up to 8.5% Hg. The distinguished types of gold grains are manifested to varying degrees at the Bystraya, Left, and Right placers. At at the Yakovlevsky placer, there is no Hg-bearing low fineness and poorly occurring Cu-bearing native gold. Comparing of the obtained data with gold grain composition data from the hypogene deposits allows us to infer bedrock sources. The Cu-bearing high-fineness type of placer gold can be compared with the Cu-bearing native gold of the Bystrinsky, Lugokan, and Kultuma deposits. Hg-bearing low-fineness placer gold grains related to erosion of the Au-bearing base metal mineralization occurred at the Novoshirokinsky and Kultuma deposits. However, Hg-bearing high-fineness gold grains, which most widely occurring in the studied placers, are absent in the in-situ mineralization. Therefore, we suppose that the bedrock source of this gold grain type is linked to the completely eroded upper levels of the Bystrinsky deposit. Thus, our study shows that it is possible to speculate on the nature of eroded material from the gold particle signature. Hense, this generic approach informs regional metallogeny in a way that even detailed field-based classical geology/geochemistry cannot. [ABSTRACT FROM AUTHOR]

• The prospect is related to an island-arc shoshonitic series. • The prospect geology is interpreted toward initially subvertical mineralized intrusions, then tilted. • Fluid inclusion data indicate a homogenous low-salinity aqueous fluid. • The prospect represents a deep level of a silica-undersaturated alkalic porphyry Cu-Au system. The Kirganik prospect is a silica-undersaturated, shoshonite-related, alkalic, porphyry Cu-Au system developed within the Late Cretaceous island arc of Central Kamchatka. It is associated with a potassic volcano-plutonic suite of rocks that range from monzogabbro- and monzodiorite- to monzonite- and syenite-porphyry, followed by a second, compositionally overlapping magmatic cycle of trachytic syenite-porphyry, and possibly other, more differentiated monzonitic phases. The rocks exhibit a subduction-related, island arc rock affinity, with the magma generation involving low degree (~1–3 vol%) partial melting of metasomatized, K-rich lithospheric mantle, followed by amphibole fractionation in a deep, probably lower crustal, magma chamber, with subsequent fractionation of accessory minerals, clinopyroxene and possibly biotite in shallower magma chambers. An early calc-potassic alteration assemblage of K feldspar-pyroxene-apatite-magnetite is closely related to small syenite intrusions. This stage is overprinted by more extensive potassic alteration zones of similarly quartz-free biotite-K feldspar-magnetite, some of which contain abundant Cu-sulfides (mostly bornite and chalcopyrite, with minor chalcocite), minor native gold and PGE minerals. Subsequent sodic-potassic to calcic-sodic-potassic alteration comprising albite-magnetite-calcite-epidote, and propylitic assemblages of chlorite-magnetite-epidote ± pyrite are much more weakly developed. These hydrothermal alteration assemblages form lens-shaped, replacement-style zones, rather than stockworks of well-defined veinlets/stringers, particularly quartz-sulfide veinlets, which are absent. Apatite from calc-potassic and potassic alteration assemblages contains low salinity (5–10 wt% NaCl-eq.) liquid-gaseous fluid inclusions indicating a homogenous, low salinity, supercritical aqueous fluid exsolved directly from a cooling and degassing pluton, with no boiling and unmixing into hypersaline and gaseous phases. Under inferred high temperatures of calc-potassic and potassic alteration (450–550 to 400–420 °C) and significant (2.1–2.2 to 1.5–1.8 kbar) pressure, this suggests a deep (>5 km?), possibly root-level of a larger, shallower, since eroded, porphyry Cu-Au system. The current geological setting and distribution of alteration and mineralization can be explained by a sharp, up to 90°, post-mineral tilting of the initial narrow, subvertical, 'finger-like' intrusions and related mineralized system, followed by deep exhumation. As a consequence, a significant part (>1.5 km) of the deep porphyry system is currently exposed at surface. [ABSTRACT FROM AUTHOR]

The geochemical features of the ores present in the oxidation zone of the gold-copper Malmyzh mineral deposit are characterized. This deposit is located in the the Nanaian region of the Khabarovsk Territory in the Russian Federation, and a technological assessment of ores present was carried out. The initial gold content in the oxidized ore is 0.1–1.2 ppm, and the leachability of gold from different size fractions by hot cyanide revealed the fact that the ore is not refractory and characterized by increased cyanide consumption. The results demonstrated a high gold content in fine size fractions. Different leaching reagents were applied for oxidized ore testing. These reagents were used both for oxidative pretreatment and leaching process. Activation of solutions was carried out by electrolysis and UV radiation. Different reagent combinations were tested in laboratory with the highest gold recovery (94%) provided by the chloride system with peroxide-sulfuric pretreatment of the oxidized ore. The same reagent combination resulted in 91–94% gold recovery during the column leaching of crushed (−10 mm) ore. [ABSTRACT FROM AUTHOR]

• The deposit becomes the largest Cu-Au porphyry deposit in the NW Pacific. • The deposit is situated at a continental transform margin. • Causative pluton belongs to low- to medium-K calc-alkaline series. • Most productive mineralization formed during transition from propylitic to phyllic alteration. • Fluid evolution included high- and low-salinity sodic-potassic to sodic-calcic fluids. The Malmyzh porphyry Cu-Au deposit cluster (>10 Mt Cu-eq.) is the largest in eastern Russia. It is located in the turbidite terrane and was formed in a transform continental margin setting. The deposit is related to a magnetite-series, dominantly low-K calc-alkaline diorite-tonalite igneous suite, with a higher potassium content in the younger (quartz monzonite to granodiorite) intrusive phases. These metaluminous to peraluminous I-type igneous rocks exhibit slightly elevated Sr/Y and have combined subduction-related to post-subduction geochemical signatures. The magma was emplaced in a series of separated local magmatic "porphyry centres" that vary in petrologic features and relative abundance of different igneous rocks as well as in the dominant development of different hydrothermal alteration and mineralization types. The deposit comprises quartz-K-feldspar ± biotite ± chalcopyrite stockworks in zones of potassic alteration, followed by quartz-magnetite ± chlorite and then by quartz-sulfide-magnetite (with chalcopyrite and bornite) stockworks in zones of propylitic alteration. The latter is partially overprinted by quartz-sericite-chalcopyrite and quartz-sericite-pyrite stockworks formed during phyllic alteration stage. The most productive Cu mineralization is related to a later (quartz-sulfide-magnetite) hydrothermal event during the propylitic alteration stage, and to an early (quartz-sericite-chalcopyrite) event during the phyllic alteration stage. Further development of phyllic alteration caused a dilution of Cu grades. Minor Au, Bi and Te mineralization accompanied Cu mineralization. Potassic alteration assemblages formed from a homogenous high-salinity (57–78 wt% NaCl and 13–12 wt% KCl), high-temperature (>525–535 °C), sodic-potassic aqueous-chloride fluid, under a pressure of 500 ± 100 bars. At the propylitic stage, the early quartz-magnetite-chlorite assemblage was formed from a lower temperature (480 ± 5 °C), sodic-dominant aqueous-chloride fluid, under near-critical conditions, and at a similar pressure (~500 bars). This was followed by two episodes of the most intense Cu and Au deposition that occurred under overlapping temperatures (~380 to 250 °C) but from compositionally distinct (sodic-potassic- to sodic-calcic-dominant) boiling to homogenous fluids during the end of the propylitic alteration stage and the beginning of the phyllic alteration stages, respectively. The different cycles of fluid exsolution likely corresponded to degassing of different magmatic intrusions during a multistage magmatic evolution. Corresponding fluid pressure decrease (to ~250 bars and lower) indicates a transition from lithostatic to hydrostatic conditions. [ABSTRACT FROM AUTHOR]

• The deposit is situated at a continental transform margin. • Causative plutons belong to high-K calc-alkaline to shoshonitic series. • Early "porphyry cycle" mineralization was overprinted by late auriferous quartz-sulfide veins. • Three major stages of sulfide deposition occurred during "porphyry cycle". • Fluid evolution included incursions of high-salinity fluids during "porphyry cycle". • Late auriferous quartz-sulfide veins formed by boiling highly carbonic fluids. The Lazurnoe porphyry Cu-Au-Mo deposit (>1Mt Cu-eq.) in the Mesozoic Central Sikhote-Alin orogenic belt (Eastern Russia) is located in an Early Cretaceous turbidite basin associated with a crustal-scale strike-slip fault zone, and was formed under the continental transform margin regime after the cessation of active subduction. The deposit is related to a magnetite-series, high-K calc-alkaline to shoshonitic, Early Cretaceous igneous suite that occurred in this tectonic setting, possibly due to asthenospheric mantle upwelling. The fertile magma was sourced from a subduction-modified mantle, under a low degree of partial melting, and was subjected to intense amphibole fractionation during its crystallization, the latter facilitating water and metal saturation. The parental igneous suite at Lazurnoe was coeval to ilmenite-series calc-alkaline igneous suites accompanied by reduced intrusion-related Au(±W) to W-Au deposits as well as to ilmenite-series, high-K calc-alkaline to shoshonitic suites accompanied by Sn-polymetallic mineralization. The deposit comprises magnetite-rich, quartz-K-feldspar to quartz-K-feldspar-biotite (potassic) alteration assemblages, containing bornite and chalcopyrite, which evolve to quartz-chlorite ± epidote ± amphibole (propylitic) assemblages, containing dominant pyrite with magnetite and chalcopyrite. Molybdenite-chalcopyrite-pyrite paragenesis dominates in quartz-sericite (phyllic) alteration assemblages that overprint and replace potassic and propylitic alteration. Potassic alteration assemblages formed from hot (~530–510 °C), high-salinity (45–48 wt% NaCl and 9–10 wt% CaCl 2), sodic-calcic aqueous-chloride fluid. Gradual fluid cooling and dilution (from 29 to 31 wt% NaCl and 18–19 wt% CaCl 2 through 24–25 wt% NaCl and 16–17 wt% CaCl 2 to 12 ± 0.5 wt% NaCl and 12 ± 0.5 wt% CaCl 2) is recorded for propylitic alteration assemblage. Another cycle of fluid exsolution from crystallizing magma can be suggested for phyllic alteration assemblages formed from a cooler (~390–310 °C), high-salinity (30–37 wt% NaCl and 5 ± 0.5 wt% CaCl 2) aqueous-chloride fluid. The porphyry-style mineralization was overprinted by the late auriferous quartz-sulfide veins containing arsenopyrite, pyrrhotite and other sulfide minerals, together with native gold (locally > 100 g/t Au) and tellurides. These veins were formed from boiling aqueous-carbonic fluid that was characterized by elevated CO 2 and CH 4 contents, with subsequent separation of high-carbonic and aqueous-chloride phases, and the fluid cooling from ~390 to 250 °C. These veins can be related to another, more reduced, plutonic suite, which crystallized at a greater depth. [ABSTRACT FROM AUTHOR]