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Palladium mineralization was registered in the Kola superdeep borehole (SG-3) for the first time in samples from deep horizons (in the fault zone at ~10 km). A proper palladium mineral (merenskyite) with the formula Pd1.00(Te1.21Bi0.79)2.00 was detected using the analytical electron microscopy and EBSD methods. The unusually high content of bismuth in the discovered merenskyite crystal most likely indicates the lower temperatures of its formation from a bismuth-rich fluid. This is supported by numerous finds of associated bismuth minerals (native and intermetallic minerals, sulfides, tellurides, and sulfotellurides) as well. A close geochemical association of noble and rare elements was revealed in the composition of the rich and diverse ore mineralization in the samples studied. It can be argued that a new type of mineralization was discovered for the SG-3 rocks: noble metal (Au–Ag–Pd) rare-element (Bi–Te).

In the central Taupo Volcanic Zone, extensive zeolite (mordenite ± clinoptilolite) alteration occurs in late Quaternary rhyolitic vitric tuffs that were deposited in a lake formed by caldera collapse following the ~290 ka Ohakuri ignimbrite eruptions. Glass shards in lacustrine vitric tuffs of the Ngakuru Formation and in the underlying Ohakuri Formation ignimbrite are replaced by mordenite ± clinoptilolite, along with hydrothermal adularia, opal-A, opal-CT, and cristobalite. This mineral assemblage is also found in the outer alteration zones of the nearby Ohakuri and Tahunaatara epithermal gold prospects. Evaluation of whole-rock chemical analyses indicates that the zeolitized vitric tuffs show a slight gain in K, and Na, Ca loss relative to unaltered Ohakuri Formation pumice, which is reflected in the presence of hydrothermal adularia in the alteration assemblage. The mordenite ± clinoptilolite alteration is associated with siliceous sinters and hydrothermal eruption breccias that were formed in recently active (39–1.5 ka) geothermal systems. By analogy with geothermal systems elsewhere in the Taupo Volcanic Zone at Wairakei and Ohaaki, the mordenite ± clinoptilolite alteration was formed from dilute alkali-chloride aqueous liquid at 60° to 150°C. Based on the close association of the mordenite ± clinoptilolite alteration with siliceous sinters and hydrothermal eruption breccias in the central Taupo Volcanic Zone, it is classified as shallow, low-temperature, epithermal alteration. Mordenite ± clinoptilolite alteration has also been identified in Quaternary rhyolitic caldera settings in Japan and the United States, where it is termed “caldera-type zeolitization.” In exploration for epithermal Au-Ag deposits in rifted arc settings, such alteration may be overlooked, given its subtle appearance and distal location relative to veins that mark upflow areas.

The Laowan super-large (208 t Au) gold deposit is located in the Tongbai orogenic belt, along with a newly-discovered molybdenite deposit at its depth in the northern periphery. The gold deposit is a fault-controlled lode gold deposit featuring sulfide quartz vein-type and altered rock-type mineralization hosted within the metamorphic rocks, whereas the molybdenum deposit is a typical porphyry-type deposit. These two deposits have their respective paragenetic sequences and mineralization types without spatial overlapping in the ore field. Here, we present U–Pb dating of zircon, hydrothermal rutile, and REE phosphates, and Re–Os dating of molybdenite to constrain the relationship between the Au and Mo mineralization, and their relation to Mesozoic granitic magmatism. Textural features indicate that rutiles and associated phosphate minerals are of hydrothermal origin, generated by re-precipitation and dissolution of titanite crystals hosted in the metamorphic host rocks due to hydrothermal alteration during Au and Mo mineralization. LA-ICP-MS U–Pb dating of rutile from the auriferous altered rocks yields a 206Pb/238U age of 120.0 ± 6.7 Ma (MSWD = 1.4), consistent with the ages of the associated monazite (125.0 ± 2.4 Ma) and xenotime (126.3 ± 2.0 Ma), representing the timing of the gold mineralization, coeval with Laowan monzogranite (zircon U–Pb: 128.8 ± 0.7 Ma). Rutile from the molybdenum deposit show an older 206Pb/238U age of 141.0 ± 11 Ma (MSWD = 1.1), consistent with the molybdenite Re–Os age (141.5 ± 1.7 Ma; MSWD = 0.27) and the zircon U-Pb age (141.6 ± 0.8 Ma; MSWD = 1.5) of the Songpa porphyry. Hence, the Au and Mo mineralization in the Laowan district represent two episodic mineralization events related to the late Mesozoic granitic magmatism. Our study also suggested that multiple isotopic dating is helpful to precisely constraint the ages for complex hydrothermal deposits.

The Sopcha massif, which is part of the Paleoproterozoic layered Monchegorsk Pluton (Monchepluton), contains an ore horizon with an average thickness of ca. 4 m within the homogeneous orthopyroxenite sequence. This horizon has a layered internal structure with variations in composition from dunite to orthopyroxenite and sulfide mineralization enriched in platinum group elements (PGE). All the rocks of the ore horizon include accessory chrome-spinels, which demonstrate a high variability of the composition and are divided into two groups based on their optical properties and chemical composition. Group I chrome-spinels belong to Al-chromites. They occur as homogeneous grains in fine-to-medium-grained orthopyroxenite at the top of the horizon and form cores of zoned chrome-spinels in the medium-to-coarse-grained orthopyroxenite and harzburgite. Group II chrome-spinels belong to Fe-chromites. They form homogeneous grains in dunite and harzburgite and rims of zoned grains in harzburgite. Chemical compositions of Group I chrome-spinels are characterized by high contents of Al2O3 and Cr2O3, an increased MgO but low contents of FeOtot and values of Cr#= Cr/(Cr + Al) and Fe3+# = Fe3+/Fetot. Group II chrome-spinels have low Al2O3 and MgO contents, and sharply increased values of Cr# and Fe3+#. This variability in the composition of chrome-spinels is caused by decreasing melt temperature in the process of its cooling during two stages of magmatic crystallization. At the first stage, cumulus crystallization of Group I chrome-spinels and subsolidus diffusion between spinel and olivine (“mineral-mineral” reaction) occurred at a temperature of about 1170 °C. At the second stage, reactions between Group I chrome-spinels and intercumulus melt (“mineral-melt” reactions) resulted in the formation of a rims of zoned chrome-spinels and homogeneous Group II chrome-spinels at a temperature of 1070–970 °C.

The gold deposits in the Jiaodong Peninsula constitute the largest gold mineralized province in China. The mineralization shows common characteristics in their tectonic setting, ore-forming fluid and metallogenic system. Sulfidation and fluid immiscibility are two important mechanisms controlling gold precipitation, both of which consume sulfur in the ore-forming fluids. The escape of H2S from the main ore-forming fluids and the decrease of total sulfur concentration not only lead to the efficient precipitation of gold, but also result in the crystallization of reducing minerals such as pyrrhotite and oxidizing minerals such as magnetite. Quartz solubility shows strong dependence on temperature, pressure, and CO2 content. The dependence of quartz solubility on pressure is weak at low temperatures, and progressively stronger at higher temperatures. Similarly, the temperature dependence of quartz solubility is relatively low at low pressures, but becomes gradually stronger at high pressures. The results of solubility modeling can constrain the dissolution and reprecipitation behavior of quartz in the ore-forming veins and the formation mechanism of different types of quartz veins. The multi-stage mineralization fluid activity resulted in the complex dissolution structure of quartz in the Jiaodong gold veins. Pyrite in the main metallogenic period in the Jiaodong gold deposits shows complex microstructure characteristics at single crystal scale. The trace elements (mainly the coupling of As- and Au-rich belt) and sulfur isotope composition also display a certain regularity. The As-rich fluids might have formed by the initial pulse of ore-forming fluids through As-rich metasedimentary strata, while the As-Au oscillation zone at the margin of pyrite grains is related to the pressure fluctuation caused by fault activity and the local phase separation of fluids. There is a temporal and spatial evolution of gold fineness in the Jiaodong gold deposits. Water/rock reaction (sulfidation) was the main ore-forming mechanism of early gold mineralization, forming relatively high fineness gold, while significant pressure drop in the shallow part accompanied by fluid phase separation promoted the late gold mineralization, forming low fineness gold. Under cratonic destruction setting, dehydration of the amphibolite and granulite facies metamorphic lower-crust resulted in the formation of Au-CO2-rich ore-forming fluids, which rose along the deep fault and secondary structure, and formed the largescale fault-controlled gold deposits in Jiaodong.

The central Dodoma region of Tanzania is one of the regions defined by the Tanzania Craton (TC). Although the Craton gold mineralization has been well explored and hosts most of the gold deposits in the country, the understanding of the mineralization potential of the Dodoma region is still an enigma. This study using trace elements geochemistry of soil samples aims basically at providing information for future exploration works in the region by delineating the possible mineralized zones, the pathfinder elements, and the lithological facies to target. Generally, there is an anomalous spatial distribution of a probable Cu-Au deposit in the N, NE, S, and SE parts of the region and are prospective areas worth exploring for gold from the Gaussian variogram models. The multivariate statistics shows that Cu, Pb, Zn, and Fe are the main pathfinder elements while searching for Au mineralization in the region. The gold deposit is most probably a Cu-Au porphyry type, although VMS type of Au deposit cannot be precluded in the area. The mineralization in the area is largely associated with tonalitic orthogenesis, tonalities, granodiorite, and granitic rocks with Cr-Ni-Co-V forming elemental association. This elemental association is similar to other gold bearing greenstone belts. The style of mineralization in the Dodoma region is similar to other gold deposits within the TC; hence, successful exploration methods in these ancient gold deposits like Geita and Kahama gold deposits can be adopted in the event of any further exploration exercise in the central Dodoma region.

The late Palaeozoic Yong’an–Meizhou depression belt is an important iron (Fe) and polymetallic metallogenic belt in southern China. It has undergone a transformation from Tethys to the circum-Pacific tectonic domain. The Luoyang deposit is one of the typical Fe skarn deposits in the Yong’an–Meizhou depression belt of eastern China. Garnet is a characteristic mineral in the deposit. Two generations of garnets are detected in the deposit based on their textural characteristics and trace-element contents, and are represented by Fe-enriched andradite. The first generation of garnets (Grt1) have two types of garnets (Grt1-A and Grt1-B). Type A garnets of the first generation (Grt1-A) (Adr80-88) replaced by massive diopside-magnetite assemblage exhibit distinct oscillatory zonings and display patterns of enriched light rare earth elements (LREE) to weak heavy rare earth elements (HREE), with weak negative to positive Eu anomalies, and highest U, ΣREE and Sn contents. Type B garnets of the first generation (Grt1-B) are irregular zones (Adr94-96) coexisting with magnetite, in which Grt1-A is generally dissolved, and have obviously LREE-enriched and HREE-depleted patterns, with weak negative to positive Eu anomalies, and moderate U, ΣREE and Zn contents. Garnets of the second generation (Grt2) (Adr96-99) that replaced massive magnetite together with sphalerite show unzoned patterns, with a flat REE pattern and pronounced negative Eu anomalies as well as contents of lowest U and ΣREE, and highest W. The substitution of REEs in garnets occurs as [X2+]VIII –1[REE3+]VIII +1[Si4+]IV –1[Z3+]IV +1in an Al-enriched environment. Luoyang hydrothermal fluids shifted from reducing conditions with relatively high-U and -ΣREE characteristics to oxidizing conditions with relatively low-U and -ΣREE characteristics. The reduced siderophile elements and increased fO2 in fluid during Grt1-B formation caused magnetite mineralization and reduced Zn contents during Grt2 formation, causing the deposition of sphalerite. All garnets formed from magmatic fluid and were controlled by infiltrative metasomatism in an opened system.

Research subject. Large orogenic gold deposits in the fold belts of Central and Northeast Asia.Materials and methods. Geological mapping of various scales on a number of large orogenic gold deposits was conducted using the methods of structural-paragenetic analysis of metamorphic strata, accompanied by obligatory linking of ore mineralization manifestations to specific structures. In a number of cases, various statistical methods were used to geometrize mineralization, identify patterns of its location and determine the paths of paleofluid flows. Available publications on the objects under consideration were reviewed. The geological and structural features of large orogenic gold deposits – Muruntau, Kokpatas, Sukhoi Log and Pavlik – were considered.Results. The Muruntau, Kokpatas and the Sukhoi Log ore deposits are of shariyage-thrust type. Compared to these objects, the Pavlik field is confined to a zone of volumetric fracturing between a series of reverse faults, feathering a large deep fault and belonging to the transpression type. At the Muruntau and Pavlik deposits, the analysis of the location of the most intensive mineralization substantiated the paths of paleofluid flows, along which the fluid migration and ore formation took place.Conclusions. The distribution of ore mineralization in the Muruntau deposit obeys the orientation of planar (cleavage) and linear (orientation of fold hinges) elements. Apparently, the former (main) direction may indicate the orientation and position of the main migration route of ore-bearing fluids, while the latter corresponds to secondary channels, the position of which is due to the intersection of syn-napping structures with favourable lithological horizons. For the Pavlik deposit, the position of ore pillars is compared with the paths of paleofluid flows, the root parts of which are promising for identifying the most powerful and intense mineralization.

Research subject. The petrological and geochemical features of the rocks of the Voznesensky intrusive massif and its dyke series were studied in order to clarify the composition, possible sources and geodynamic settings of magma generation that produced Au- and Cu-porphyry mineralization.Methods. The content of petrogenic oxides was determined by the chemical method, trace elements – by ICP-MS analysis.Results. Among the rocks of the Voznesensky massif, which have the geochemical characteristics of suprasubduction formations, varieties with calc-alkaline and adakite-like properties were established. The main phase of the massif is represented by gabbro-diorites and diorites belonging to the calc-alkaline series. Ore-bearing dykes of gabbro-diorites, diorites and granodiorites of the Au-porphyry Bolshekaransky deposit are of calc-alkaline composition, while the post-ore dykes of granodiorites and plagiogranites of this deposit exhibit adakite-like characteristics.Conclusions. The ore-bearing dyke series of the Voznesensky deposit is represented by calc-alkaline diorites and adakite-like granodiorites and plagiogranites. The metallogenic specialization of the dykes was influenced by the silicic acidity and the redox state of the ore-generating melts. Granitoids with Cu-porphyry mineralization, compared to their gold-bearing varieties, crystallized from more acidic melts with a higher degree of oxidation. It is assumed that the main mantle component of magmas for the Voznesensky rocks were relatively weakly depleted spinel peridotites of the suprasubduction lithospheric mantle. Calc-alkaline magmas were melted from a mantle substrate previously metasomatized by aqueous fluids, and magmas with adakite-like properties – metamorphosed by melts of basalts and sedimentary rocks of slab. Melting of slab rocks may have been associated with additional heating due to friction caused by changes in direction and/or velocity of oblique subduction.

The origin of hypogene alteration and mineralization features in the Escondida 27porphyry Cu deposit resulted from intense overprinting related to three main hydrothermal 28stages. The beginning of each stage is recorded by deposition of bright quartz crystals on 29vein walls that precipitated from high-temperature fluids. In the deepest zones of the 30deposit, the earliest stage started with exsolution of intermediate-density fluids, which 31transported high concentrations of Cu, whereas Mo was not detected. However, in the 32shallow zones, the early stage began with depressurization and unmixing of intermediate-33density fluids, which generated both a hypersaline and vapour-rich fluid phase, producing 34an important geochemical segregation between both phases. The transitional stage also 35started with circulation of intermediate-density fluids but never experienced unmixing. 36These fluids transported the highest Mo concentrations in the deposit; however, Cu displays 37lower concentrations relative to intermediate-density fluids from the early stage. The 38beginning of the late stage was also associated with intermediate-density fluids; however, 39Cu and Mo were below the detection limits in most of the analysed fluids. During the 40evolution of the three stages, the fluids experienced gradual cooling, which promoted the 41precipitation of euhedral and zoned quartz crystals that overgrew the early high-42luminescence quartz generations. Sometimes, sulfide minerals display euhedral crystal 43boundaries with zoned quartz, suggesting that mineralization started during these phases.44The latest events detected in each main stage are linked to cooler and low-salinity fluids, from which dark quartz and hypogene sulfide sprecipitated along microfractures and 46interstitial spaces developed in the earlier quartz generations.

Genesis of magmatic Ni-Cu-(PGE) deposits involves many interconnected and multiple-scale processes in the fields of thermodynamics, kinetics and fluid dynamics. The main focus of quantitative work on magmatic sulfide ore genesis has been on equilibrium thermodynamics since the initial studies over 50 years ago, while the significance of kinetics and dynamics to sulfide mineralization in dynamic magmatic systems has received little attention. Taking the komatiite-hosted Ni-Cu-(PGE) deposits of the Raglan area as an example, we have developed a quantitative model for assimilation of sulfidic substrates during lava emplacement through the consideration of these three fields. We show that the dominant control on the composition of externally derived sulfide xenomelts throughout their residence within the flowing magma is exerted by relative rates of diffusion of sulfur and metals. In rapid channelized flow of komatiites, the kinetically-controlled extraction of chalcophile elements from silicate melt into externally-derived sulfide droplets released from underlying sediments is the quickest way to produce orebodies with economic value, without the necessity of reaching either sulfide saturation throughout the mass of magma or indeed compositional equilibrium in the magmatic system as our long-held understanding would suggest. The kinetic upgrading of initially metal-poor sulfide xenomelts is enhanced for sulfide droplets of smaller size and increasing downstream distance from the source, approaching to equilibrium mass distribution for the fast-diffusing elements such as Cu during prolonged or especially vigorous processes (e.g., chaotic magma mixing). In this kinetically-driven process, differences in diffusivities between Pt and Pd may account for the anomalous excess Pd/Pt ratios (~2) of disseminated ores from many komatiite-related deposits compared with the compositions of the parental magmas. Sedimentation of sulfide on the bottom of the flowing magma terminates this kinetically-controlled process, while the number density of droplets imposes a restriction on sulfide compositions due to mass conservation. Therefore, sulfide mineralization in komatiite-associated deposits is mostly controlled by diffusion kinetics with additional interactions and restrictions from the dynamics of transport and settling of sulfide droplets. By analogy, multiple cycles of dynamic processes predominate in the conduit-type magmatic deposits. A quantitative grasp of the relative importance of these three fundamental mechanisms, i.e., thermodynamic driving forces, kinetics of diffusive equilibration, and fluid dynamics of transport and deposition, is of great value in understanding ore genesis in complex mineral systems and even the origin of igneous rocks in general.

One of the pivoting problems in the genesis of magmatic deposits is the role of silicate melt in the origin of sulfide ores. A way of solving this problem is to compare massifs with different mineralization, using contents of major and trace elements in the rocks. However, intrusions of the Norilsk intrusive complex are rarely compared with one another in terms of ore composition and volume in them. This paper is the first geochemical data, all of which were acquired with the application of modern analytical techniques, on the Chernogorsky intrusion in the Norilsk trough. The structure and composition of this intrusion are well comparable to the intrusions of the same complex hosting the uniquely large deposits: Talnakh, Kharaelakh, and Norilsk 1. The weighted mean composition of the Chernogorsky intrusion (wt %) is as follows: 47.2 SiO2, 0.62 TiO2, 16.7 Al2O3, 9.94 FeO, 0.16 MnO, 11.7 MgO, 11.3 CaO, 1.53 Na2O, 0.46 K2O, 0.07 P2O5, and 0.18 Cr2O3,, and the ratios of trace elements (La/Sm)n = 1–2, (Gd/Yb)n = 1.2–1.4, and (Th/Nb)n = 1–4 are same as typical of other rocks of the Norilsk complex. The ores of the Chernogorsky intrusion are close to the ores of Norilsk 1, their Cu/Ni ratio slightly exceeds 1, and the Pt + Pd = 5–6 ppm on average. However, the predicted resources of metals in this massif (0.8 Mt Cu + Ni and 0.5 kt Pt + Pd) are 140 times lower than the resources of the Kharaelakh intrusion (113 Mt Cu + Ni, 17.5 kt Pt + Pd), and 50 times lower than in Talnakh (40 Mt Cu + Ni, 8.3 kt Pt + Pd). This confirms that the ore content in an intrusion does not depend on the composition of its silicate rocks, and hence, the compositions of these rocks cannot be used as an exploration guide for new deposits.

The term “rare metals” refers in this work to metals with a low availability in natural. Based on their chemistry, rare metals were classified into; 1) rare earth elements (La-Lu), 2) trace elements (Nb, Ta, Mo, Cu, Ni, Co, Sn, W, V), 3) noble elements (Au, Ag, and PGE) and 4) fissionable elements (U and Th). In Egypt, rare earth elements occur in the phosphorites, monazite and granites. Trace elements occur in three associations; a) elements in granites and albite granites such as Nb, Ta, Sn, Mo, and W, b) elements associate mafic rocks and ophiolites include Cu, Ni, and Co, and c) V in the black shales. 95 Au localities were reported mainly as vein-type mineralization in the Eastern Desert. PGE are confined to three associations including mafic and ultramafic rocks, chromite and black shales as sulfides, alloys, and organometallic compounds, respectively. Uranium occurs in granites of the Eastern Desert. Thorium was reported at the Um Ara area at the Eastern Desert and in the monazite from the black sands. Although rare metals are quite common in Egypt, processing and beneficiations of the rare metals-bearing rocks did not reflect the abundance and the economic significance of these metals

The results of studying the mineralogy of metamorphic schists from the Pre-Jurassic base of the Arctic part of the West Siberian plate are presented. The accessory and ore mineralization of schists from the Zapadno-Yarotinsky license area located in the southern part of the Yamal Peninsula is studied. The schists was uncovered by the Zapadno-Yarotinskaya No. 300 well at a depth of 2762 m. Above the section, the metamorphic rocks are overlain by a young Meso-Cenozoic cover. The schists are mainly composed of quartz, plagioclase (albite), carbonates (dolomite and siderite), mica (muscovite) and chlorite (donbassite). The discovered accessory and ore minerals in the metamorphic schists of the Zapadno-Yarotinsky area can be divided into two groups. The first group includes minerals that were formed during the metamorphism of schists, or were preserved as detrital matter. These minerals include zircon, fluorapatite, and rutile as the most stable compounds. The remaining mineralization (pyrite, sphalerite, chalcopyrite, cubanite, galena, cobaltite, barite, xenotime-(Y), goyazite, synchysite-(Nd), native silver and copper) is clearly secondary and was formed as a result of superimposed metasomatic processes. Judging from the described mineralogy, the schists underwent changes as a result of superimposed propyllitization. The temperature range of this process is determined by the formation of cubanite in association with chalcopyrite at a temperature of 200-210 оС.

Weakly disseminated sulphide mineralization is present in the outcrops of several mafic–ultramafic intrusions in the Beishan region of the Central Asian Orogenic Belt in western China, but the pote...

Magmatism in northern Colorado beginning in the late Eocene is associated with the formation of Pb-Zn-Ag carbonate-replacement and polymetallic vein deposits, the onset of caldera-forming magmatism, and eventually, the formation of rift-related, F-rich Mo porphyries (“Climax-type” intrusions). We use high-precision U/Pb zircon geochronology to better evaluate the temporal framework of magmatism and mineralization in the region. Our results demonstrate that mineralization in the Leadville area occurred between 43.5 and 39.7 Ma and was followed by mesothermal mineralization in the Montezuma area at approximately 38.7 Ma. Mineralization is associated with a suite of approximately 43 to 39 Ma intermediate magmatic centers that extended from Twin Lakes through Montezuma. The oldest porphyries associated with F-rich Mo prospects and deposits (Middle Mountain; 36.45 Ma) intruded 900 kyr after the start of the ignimbrite flare-up in the region. Spatiotemporal analyses reveal that the pattern of magmatism shifted in orientation between 40 and 35 Ma. We propose a model wherein magmatism before 39 Ma was the result of fluids evolved from the subducted Farallon slab being focused through weak zones in the lithospheric mantle and into the lower crust. This was followed by a more diffuse and higher power melting event that corresponds to a distinct change in the spatial patterns of magmatism. Our data suggest that low-grade Mo porphyry deposits can form close in time to calderas. We hypothesize that the transition from subduction to extensional tectonics in the region was responsible for this more widespread melting and a distinct shift in the style of magmatic-hydrothermal mineralization.

The Kapalagulu intrusion in eastern Tanzania hosts a major, 420-m-thick, stratiform/stratabound platinum group element (PGE)-bearing sulfide zone—the Lubalisi reef—within a prominent, chromititiferous, harzburgite unit close to its stratigraphic base. Several features of the vertical base and precious metal distributions (in a composite stratigraphic section based upon two deep exploration drill holes) display similarities to those of offset-type PGE reefs that formed under the overall control of Rayleigh fractionation: (1) composite layering (at several scales) defined by systematic vertical variations of sulfide and precious metal contents and intermetallic ratios, indicating repeated cycles of PGE enrichment and depletion in the order Pd-Pt-Au-Cu, and (2) in the lower part of the reef, stratigraphic offsets of the precious metal peaks below peak sulfide (Cu) content. The form and geochemistry of the reef are consistent with overturns of basal liquid layers within a liquid layering system (i.e., stable density-driven stratification of a magma chamber), plus at least two minor inputs of parental magma during which the resident magma was recharged with sulfur and metals, and the effective depletion of precious metals in the magma midway through reef development. The Lubalisi reef differs from classic offset-type PGE reefs, however, principally because individual Pd, Pt, and Au enrichment peaks are coincident, not offset. The reef is set apart from other offset-type PGE reefs in three additional ways: (1) its association with olivine cumulates that crystallized soon after initial magma emplacement and well below the first appearance of cumulus pyroxene or plagioclase (implying attainment of sulfide saturation and precious metal enrichment without prolonged concentration of sulfur and chalcophile metals by normal magma cooling and differentiation), (2) the probable role of chromite crystallization in not only triggering sulfide segregation during reef formation but also facilitating precious metal enrichment in the early stages of reef development, and (3) its great width. The early stage of fractionation may also help explain the coincident precious metal peaks through its effect on apparent precious metal partition coefficients.

We present new age constraints for igneous rocks and ore-metasomatic formations of the gold deposits in the Akzhal-Boko-Ashalin ore zone. In terms of their ore formation, these deposits correspond mainly to the orogenic type, which generally reflects specific metallogeny of the West Kalba gold-bearing belt in East Kazakhstan. Gold-quartz veins and mineralized zones of the gold-sulphide formation are confined to fractures feathering regional NW-striking and sublatitudinal faults. Their common features include the following: gold-bearing veinlet-disseminated pyrite-arsenopyrite ores that are localized in carbonaceous-sandy-schist and turbidite strata of different ages; structural-tectonic control of mineralization, numerous dikes of medium-basic compositions in ore-control zones; and the presence of post-orogenic heterochronous granite-granodiorite rocks, although their relation to gold-ore mineralization is not obvious. Igneous rocks of the study area have similar ages in a narrow range from 309.1±4.1 to 298.7±3.2 Ma, which is generally consistent with the previously determined age of granitoid massifs of gold-ore fields in East Kazakhstan. A younger age (292.9±1.3 to 296.7±1.6 Ma) is estimated for felsic rocks of the dyke complex. For the ore mineralization, the 40Ar/39Ar dating of sericite from near-ore metasomatites yields two age intervals, 300.4±3.4 Ma and 279.8±4.3 Ma. A gap between of the ages of the ore mineralization and the igneous rocks is almost 20 Ma, which may indicate that the processes of ore formation in the ore field continued in an impulse-like pattern for at least 20 Ma. Nevertheless, this confirms a relationship between the hydrothermal activity in the study area and the formation and evolution of silicic igneous rocks of the given age interval, which belong to the Kunush complex, according to previous studies. This interpretation is supported by reconstructed tectonic paleostress fields, showing that directions of the main normal stress axes changed during the ore mineralization stage, which is why the ore bodies significantly differ in their orientations. The above-mentioned data are the first age constraints for the study area. Additional age determinations are needed to further improve understanding of the chronology of ore-forming processes. Actually, all the features characterizing the gold mineralization of the Akzhal, Ashalin and Dauba ore fields, including the data on lithology, stratigraphy, structural tectonics, magmatism, isotope geochronology, mineralogy and geochemistry, can be used as criteria when searching for similar ore fields in East Kazakhstan.

The Bayan Obo ore deposit in Inner Mongolia, North China, the largest-known rare earth element (REE) deposit in the world, has attracted considerable attention over the past decades. However, its genesis has been highly debated, especially whether the host dolomite is of sedimentary or igneous origin. In this study, we present a comprehensive study on field geology, petrographic, geochemical, and apatite fission track analyses on REE-mineralized dolomite (H8) and its wall-rock (H9), in an effort to provide additional insights into the formation and preservation of this giant ore deposit. According to field geology and petrology analyses, the ore-hosted dolomite of the H8 unit in/around the Bayan Obo deposit displays the characteristics of sedimentary carbonates and demonstrates complicated deformation and hydrothermal events that resulted in the complex REE mineralization. The parameter of w(As) in pyrite ranging from 100 to 1600 ppm suggesting that the pyrite of the Bayan Obo deposit was mainly formed in a hydrothermal environment, and the thermal event from pyrite at ~440 Ma may represent the mineralization event of the Bayan Obo deposit, or it is an important disturbance event after the mineralization of the deposit. The geochemical research depicts that the evolution process of carbonatite was originated from calcium carbonatites and magnesio-carbonatites to ferro-carbonatite, indicating that the different genesis models of the Bayan Obo deposit that ranging from sedimentary carbonate to volcano-sedimentary and igneous carbonatites are reasonable. The two apatite ages obtained from granite on the east side of the Bayan Obo deposit and the dolomite in the Bayan Obo deposit are ~173 Ma and ~54 Ma, respectively. Time–temperature (t–T) histories of rocks yield new information about the timing of deformation of the Bayan Obo deposit, implying that the east side of the deposit experienced a rapid cooling process between ~300 Ma to ~54 Ma (especially ~300–180 Ma), this reflects the granite underwent a rapid cooling process which coeval with the plate subduction during the closure of the Palaeo-Asian Ocean, while the tectonic movement has little effect on the broken of the H8 dolomite in the mining area. Although the slate of the H9 unit from the east of the Bayan Obo deposit experienced a strong fragmentation in the later tectonic movement, it still made a great contribution to the mineralization for better preservation of REE-rich fluids, leading to the formation of the giant Fe-REE-Nb deposit.

The Hehuashan sediment-hosted Pb–Zn deposit is a large-scale (Pb + Zn＞1 Mt) deposit hosted in the Tongling mining district of the Middle-Lower Yangtze River belt (MLYB). The Pb–Zn ore bodies are composed of two main mineralization types, namely breccia type and massive type. The breccia type ore bodies are hosted by the Triassic limestone and dolostone, while the massive ore bodies are hosted by marble dolostone which are close to the diorite intrusions. The previous research showed that the Hehuashan Pb–Zn deposit is a Mississippi Valley-type (MVT) deposit formed in Middle Triassic and overprinted by late mineralization of magmatic-hydrothermal fluids in Yanshanian period. In this research, we aimed to declare the age of the late mineralization and it's relationship with diorite intrusions. The mineralization age (132.8 ± 3.1 Ma) of the massive ore rocks (late mineralization) is similar to the zircon U–Pb age of the diorite (133–130 Ma), showing that this type mineralization is contemporaneous to the Yanshanian intrusive events. Furthermore, similar initial 87Sr/86Sr values between sphalerite and diorite indicating a magmatic fluid was involved during the mineralization process and the emplacement of diorite also might have provided ore-forming materials. The heavy sulfur compositions (δ34S = +8.6‰ to +12.8‰) of the sphalerite in massive ore rocks indicate that the sedimentary sulfate may have provided reduced sulfur for sulfides precipitation by sulfate thermochemical reduction process. Sr–Nd isotopic compositions of the diorite in the Hehuashan deposit area showed that the massive Pb–Zn mineralization was related to the intrusion of diorite in an extensional tectonic setting. In summary, the Hehuashan Pb–Zn deposit composes a late Yanshanian Pb–Zn mineralization event and represents a younger Pb–Zn mineralization in the Tongling district and MLYB. The Triassic carbonates have the potential for Pb–Zn deposit exploration in the Tongling district and Middle–Lower Yangtze River belt.

The Youjiang Basin is characterized by a wide distribution of Au and Sb deposits. These deposits are mainly hosted by sedimentary rocks from Cambrian to Triassic and are structurally controlled by faults and folds. Three types of Sb mineralization can be distinguished based on geologic characteristics, economic metals, and mineral associations. The first type is dominated by Sb mineralization but contains minor or little Au, similar to the large Qinglong deposit. The second type has a spatial association with the gold deposit but formed independent Sb mineralization, reminiscent of the Badu deposit. In the third type, Sb generally formed as an accompanying element in the Carlin-type gold deposit, and stibnite occurred as euhedral crystals filling the open space and faults in the late stage of gold mineralization, analogous to the Yata deposit. Trace element concentrations and sulfur isotopic ratio of stibnite, and oxygen isotope of stibnite bearing quartz were analyzed to infer the ore source(s) for Sb mineralization and genesis. To distinguish the various types of stibnite mineralization between the deposits, Cu, Pb, and As have recognized most diagnostic, with an elevated concentration in Au and Au-Sb deposits and depleted in Sb deposit. The δ34S isotopic composition of stibnite samples from three deposits show a wide variation, ranging from −6.6 ‰ to + 17.45 ‰. Such isotopic values may indicate the sedimentary sulfur source, introduced by fluid–rock interaction. On the other hand, fluid mixing of several end members cannot be excluded. The calculated δ18O isotopic data of Sb-bearing quartz show the initial ore fluid in Au and Au-Sb deposits most likely have a magmatic or metamorphic origin that enriched during fluid–rock interaction, and Sb deposit characterized by initial meteoric water. From these data, we proposed that different lithologies, fluid–rock interaction, fluid pathways, and different ore fluids controlled the compositional evolution of fluids, which might be the main reason for the diversity of Au or Sb mineralization.

Актуальность исследования обусловлена необходимостью разработки прогнозно-поисковых критериев для выявления стратегически важного типа германиевого сырья - германий-угольных месторождений. Цель: изучить геохимические особенности и условия образования комплексного редкометалльного оруденения в углях месторождения Спецугли (Дальний Восток) и на его примере разработать геолого-геохимическую модель формирования месторождений подобного типа. Объекты: угли, углевмещающие породы, подземные воды и породы фундамента германий-угольного месторождения. Методы: геолого-геохимическое изучение и опробование, масс-спектрометрия с индуктивно связанной плазмой, инструментальный нейтронно-активационный анализ, сканирующая электронная микроскопия, оптическая микроскопия, рентгенофазовый анализ, корреляционный анализ. Результаты. Получены новые данные по геологическому строению и особенностям геохимии углей и углевмещающих пород германий-угольного месторождения Спецугли в Приморье. Обоснован комплексный полиэлементный состав редкометалльного оруденения, согласующийся с особенностями геохимии и минерагении пород фундамента и обрамления Павловской впадины. Для металлоносных углей характерны аномально высокие, превышающие в десятки и сотни раз средние содержания для бурых углей мира, концентрации Ge, Sb, Hg, W, Li, Be, Cs, и As. Менее аномальны уровни накопления U, Mo, Y, Rb, лантаноидов, Zn и Ga. Выполненный комплексный минералого-геохимический и геолого-структурный анализ особенностей состава и строения Ge-угольного месторождения Спецугли позволил пересмотреть принятую гидротермальную модель его образования и обосновать предложенную ранее гипергенную модель, когда источником металлов являются породы фундамента, вмещающие угольные месторождения. Формирование Ge и сопутствующего оруденения в месторождении Спецугли происходило под влиянием формирующейся коры выветривания по редкометалльному граниту вознесенского комплекса, прорванному дайками позднепермского возраста. Месторождение приурочено к возвышенности гранитного состава, образуя концентрически-зональный ореол Ge и сопутствующих элементов вокруг неё. Граниты подвергнуты гидротермальнометасоматическим изменениям докайнозойского возраста с формированием кварц-альбит-микроклиновых метасоматитов и грейзенов, содержащих W-Mo и Hg-Sb-As минерализацию. Образование редкометалльного оруденения в углях связано с формированием каолиновой коры выветривания по гранитам, выносом и переотложением основных элементов в окружающие палеоторфяники в палеогеновое время. The relevance of this research is conditioned by the need to develop predictive and prospecting criteria for identifying a strategically important type of germanium raw material - germanium-coal deposits. The main aim is to study the geochemical features and conditions for the formation of complex rare-metal mineralization in coals of the Spetsugli deposit (Far East) and by this example develop a geological-geochemical model of the formation of deposits of similar type. Objects: coal, coal-bearing rocks, underground waters and basement rocks of the germanium-coal deposit. Methods: geological and geochemical sampling, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis, scanning electron microscopy, optical microscopy, X-ray phase analysis, correlation analysis. Results. New data on the geological structure and geochemistry of coals and coal-bearing rocks in the Spetsugli germanium-coal deposit in the Primorsky Krai were obtained. The complex polyelement composition of rare-metal mineralization in the deposit is explained. It is consistent with geochemistry and minerageny of basement rocks and the framing of the Pavlovsk depression. Anomalously high concentrations of Ge, Sb, Hg, W, Li, Be, Cs, and As are typical in metalliferous coals; they are tens and hundreds of times higher than the average content in lignite worldwide. The accumulation levels of U, Mo, Y, Rb, REE, Zn and Ga are somewhat less anomalous. The complex mineralogical-geochemical and geological-structural analysis of the composition and structure of the Spetsugli Ge-coal deposit made it possible to reevaluate the accepted hydrothermal model of Ge mineralization in coals. It also helped to validate the previously proposed hypergene model, which states that the sources of metals are basement rocks hosting coal deposits. The pre-Cenozoic age of endogenous rare-metal mineralization in granites of the basement was substantiated. The formation of Ge and accompanying mineralization in the Spetsugli deposit was influenced by the forming weathering crust over the rare-metal granite of the Voznesensky complex cut by dikes of the Late Permian age. The deposit is confined to a granite upland, forming a concentric-zonal halo of Ge and associated elements around it. Granites underwent hydrothermal and metasomatic alteration which resulted in quartz-albite-microcline metasomatites and greisens containing W-Mo and Hg-Sb-As mineralization. Rare-metal mineralization in coals is associated with the formation of kaolin weathering crust over granites, removal and redeposition of basic elements in the surrounding peat paleo-bogs in the Paleogene.

—A quantitative study of the mineral composition of the Talnakh deposit ores and host rocks from two wells was carried out using polished sections. The values ​​of several physicomechanical, magnetic, and electrical properties were determined. These data were used to calculate the contents of the main ore minerals and useful components in the studied samples as a function of their petrophysical properties, as well as to reveal the near ore petrophysical anomalies in the ore horizons exocontacts. Application of this research methodology will allow an increase in the efficiency of prospecting and appraisal works for the Norilsk type sulfide mineralization.

Numerous silicate, Fe-oxide, and Cu–Au–Ag microspherules are found in Fe ores and pyroclastic rocks of the Kostenga deposit, Lesser Khingan (Far East of Russia). The silicate spherules contain immiscible Fe and Si glasses, vapor voids, and mineral inclusions. The Fe-oxide spherules host magnetite with a small amount of ilmenite and Fe-rich silicate glass. The Cu–Au–Ag spherules contain inclusions with dominant CuO in their composition. These microspherules are considered to form due to rapid uplift and degassing of liquation-differentiated ore-silicate melts. The possible volcanic formation of ores and precious metal mineralization is discussed for these types of the deposits.

A structural interpretation of the first Re–Os dating of pyrite and arsenopyrite from the Malinovsky gold deposit is given. Comparison of the obtained data and the known ages of ore-bearing granitoids from the ore field made it possible to determine the age of mineralization as 100–90 Ma. This age corresponds to the time of completion of the Albian–Cenomanian geodynamic setting of the transform margin of the Asian Continent with significant left-shear dislocations, as is evident from the structural patterns of localization of ore bodies and magmatic rocks. The time interval and geodynamic conditions for the formation of the Malinovka deposit are similar to those of many gold and gold-bearing deposits within the Sikhote-Alin orogenic belt and the south of the Korean Peninsula.

A mechanism is suggested to explain the transport of sulfide material by means of its dissolution and subsequent redeposition under the effect of an ascending infiltrating flow of intercumulus melt during the compaction of cumulates in layered plutons. Evidences of this process are observable in the Burakovo–Aganozero intrusion. Analysis of data on Cu concentrations in rocks of the pluton (more than 10 000 samples of core material from 160 boreholes) reveals two distribution types of the low-sulfide mineralization. The vertical sections of the first type are characterized by mineralization distributed throughout the whole thickness of the lower unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates and the almost absolute absence of sulfides in all overlying rocks. In the second type, Cu mineralization is constrained to the top part of this unit of clinopyroxene–orthopyroxene (Cpx–Opx) cumulates, and the overlying rock sequence of the zone of clinopyroxene–orthopyroxene–plagioclase (Cpx–Opx–Pl) cumulates includes intensely mineralized rocks. Physicochemical analysis within the scope of D.S. Korzhinskii’s theory of acid–basic interaction and numerical simulations of the effects of major components of the melt on the solubility of the sulfide phase indicate that Ca and Mg play an important role in the liquid immiscibility/dissolution of the sulfides. A model is proposed for the origin of the low-sulfide mineralization of this pluton: clinopyroxene emergence on the liquidus resulted in the onset of liquid immiscibility of sulfide and produced Cu distribution of the first type. The infiltration of the intercumulus melt during the compaction of the cumulus material led to the dissolution and upward transport of the sulfide material for hundreds of meters and thus produced Cu distribution of the second type.

The article discusses a novel methodological approach to deciphering the evolution of ore-magmatic systems (OMS), based on the study of geochemical fields associated with different stages of the evolution of the magma chamber, accompanied by ore mineralization. As the material for research, we used the results of geochemical dispersion train surveys within the Kara ore cluster (Eastern Transbaikalia). The analysis of features of the composition and sequence of identification of geochemical fields made it possible to consider in more detail the evolution of the Kara OMS. It was found that we are dealing with a highly eroded rare metal OMS created in two ore formation stages. The first ore formation stage is associated with the evolution of the upper magma chamber (apical part of the Kara–Chacha massif). The main useful component of this OMS was Mo. The second stage is associated with the evolution of the lower magma chamber. This was also rare-metal mineralization; its profiling elements were W and Mo, but the main useful component is Au. It was found that Au is mobile at two evolutionary stages of the late OMS and accumulates when one stage of mineralization overprints the other. Granitoids of the Kara–Chacha massif can be considered the source of Au. No less probable is the hypothesis of its input together with B from the lower levels of the magmatic system, or as part of transmagmatic fluids from without.

In the Angara part of the Yenisei Ridge, a sequential section of the metapicritic–basalt sequence and overlying carbonate rocks of the Gorevskaya Formation is established. This section is considered as a single volcanic–sedimentary complex formed at the Late Mesoproterozoic–Early Neoproterozoic boundary in the riftogenic marginal–continental paleobasin in the southwestern Siberian Craton. It is proposed to introduce the metapicrite–basaltic sequence into the stratigraphic legend of the Shirokaya Group of the western Yenisei Ridge under the name “Nizhnerechinskaya Sequence”. In the studied section, metamorphosed picrobasalts and picrites predominate in the lower part of the Nizhnerechinskaya Sequence, while the middle and upper parts consist mainly of basalts containing Pb–Zn mineralization (Stepanovsky ore occurrence). At the contact with carbonate deposits of the Gorevskaya Formation, an alternation of volcanogenic rocks and terrigenous–carbonate sediments and metabasaltic sills are observed. The petrochemical and trace-element composition of metavolcanic rocks has much in common, which indicates the paragenetic relationship of rocks of this high-Mg rock association. All these rocks are enriched in Fe and Ti, while metabasalts and metagabbros show elevated alkalinity and P2O5 content. In terms of total alkalinity, metabasalt–picrobasalts deviate from the normal petrochemical series towards the subalkaline series, which correlates with their elevated Ti content. Basites enriched in alkalis, especially, in potassium and corresponding to trachybasalts are observed among them. The contents of incompatible trace elements clearly increase from picrites to basalts and reach maximum in trachybasalts, which show 1.5–3 times enrichment in high-field strength elements compared to the basalts. The paragenetic nature of the considered association is supported by the similar REE distribution patterns: (La/Yb)n = 6–7 at Eu/Eu* = 0.9–1. The Late Mesoproterozoic–Early Neoproterozoic rifting of the Earth’s crust in the Angara region led to the opening of the marginal–continental sea basin, where basalt-picrite volcanism occurred simultaneously with accumulation of terrigenous–carbonate sediments, including ore–bearing (Pb–Zn) rocks of the Gorevskaya Formation, which host the Gorevskoye Pb–Zn deposit. The basin under consideration is interpreted as a relict rift-related paleobasin on the western margin of the Siberian craton, while the volcanic–sedimentary Nizhnerechinskaya Sequence is considered as the lower potential stratigraphic level of the base-metal mineralization in the Gorevsky ore field.

The Gol’tsovoe Ag–Pb–Zn-deposit (1600 t silver in ores with an average grade of 1025 g/t Ag) is located on the southeastern flank of the Dukat mining district, at the junction of the Balygychan–Sugoi rift trough and the Okhotsk–Chukotka Volcanic Belt (OCVB). The Dukat district is the largest silver producer in Russia. The Gol’tsovoe deposit is located 2 km north of the Pestraya granitoid intrusion, in the structurally complex zone of a fault contact of the Upper Triassic terrigenous sediments and Late Cretaceous volcanic rocks. The contact consists of a series of fault planes within a 0.5–1 km wide belt, along which the western block, composed of felsic volcanics, has been downthrown more than 1 km. The host Upper Cretaceous rhyolitic and rhyodacitic ignimbrites are intruded by subvolcanic nevadite bodies. A characteristic feature of the deposit is the occurrence of en-echelon galena veins and veinlets with high Ag grades at the upper levels of orebodies. Massive, coarsely banded, and spotted ore structures are predominant. Ore geochemistry agrees well with the mineral composition. The ores are enriched in a wide spectrum of elements: Ag, Sb, Pb, Cd, As, Zn, Bi, In, W, Sn, Mn, Cu, Li, Tl, and Cs. They are characterized by a low total REE abundance (33.34–50.69) and a negative lanthanide distribution type. Commercially significant potential by-products are Cd, In, and Bi. Galena is the main Ag mineral concentrator: the high Ag concentrations in this mineral are due to the occurrence of small inclusions of a large group of independent Ag-bearing minerals, argentotetrahedrite and pyrargyrite especially, and a small amount of myargirite, polybasite, etc. Argentite and native Ag occur in limited amounts. Tin minerals are represented by stannite, canfieldite, and less frequent cassiterite. Oxidation zone has been tracked over the entire mineralization depth and displays a pronounced linear trend. Oxidized ores are dominated by Zn, Pb, Fe, Ca, and Ba sulfates; less abundant Fe, Mn, and Zn oxides; and subordinate carbonates and clays; total sulfides and native metals (Cu, Ag) do not exceed 2%. Ore oxidation degree is 40.3%. The sulfide–quartz–chlorite veins of the Gol’tsovoe deposit formed at moderate temperatures (276–138°С) from low-concentration chloride hydrothermal fluids (4.2–0.2 wt % NaCl eq.), saturated with Na and К cations and Mg in subordinate amount. The obtained data allow the Gol’tsovoe deposit to be classified as an epithermal intermediate sulfidation deposit. A two-stage ore emplacement model is proposed. During the first stage Ag–Pb–Zn ore was emplaced as a result of the functioning of a near-surface hydrothermal system of volcanic origin. During the second stage, imprinted Sn mineralization was emplaced in the Ag–Pb–Zn ore veins as a result of tin-bearing magmatogenic fluid inflow at the lower levels of the deposit.

Mineralogical and geochemical studies of sulfide–platinum metal assemblages of the Khudolaz complex made it possible for the first time to substantiate their polygenetic nature. Three types of sulfide assemblages were distinguished. Their formation is associated with the segregation and fractionation of a sulfide melt, subsequent replacement of primary sulfides at the early hydrothermal stage, and partial redeposition of sulfides at the late hydrothermal stage. It was established (LA-ICP-MS data) that the removal of pla-tinum group elements (PGE) occurred due to primary sulfide alteration with their partial accumulation in newly formed sulfides. The structural position of PGM grains was studied using a scanning electron microscope. Platinum-group minerals (PGM) were crystallized during three stages: (1) from residual highly fractionated sulfide melts or immiscible metalloid melts captured by sulfides; (2) during the segregation of isomorphic impurities of PGE and chalcophile elements due to the exsolution of solid sulfide solutions; (3) during the interaction of antimony-enriched fluids with alternating sulfides.

Large-scale, hypogene iron mineralization systems developed recurrently in the Sao Francisco craton in association with two orogenies. During the ca. 2.1–2.0 Ga Trans-Amazonian orogeny, low...

Tirtomoyo in Wonogiri district is known as an ore mineralization region, in which one of the prospects occurred is Hargosari. No previous studies on the ore characteristucs have been done. A set of study on Hargosari prospect is aimed to characterize gold mineralization covering some aspects such as mineralogy, textures, ore chemistry and ore forming condition. To achieve the objectives, some research methods were performed suh as mapping, sampling and laboratory analyses for selected samples on term of petrography, ore microscopy and ore chemistry. Oligo-Miocene andesitic lava from Panggang Formation is identified as host rock. Opening system of veins is of jogs type to form en-´echelon tension gash veins. Quartz veins are enveloped by argillic and propylitic alteration zones, in association with pyrite, chalcopyrite, sphalerite, galena, gold, silver, chrysocolla, covellite and hematite. The approximately 5 cm thick quartz veins exhibit massive, swarm, low angle veins and stockwork structures, which is characterized by normal banded, crustiform, comb and saccaroidal textures. The quartz veins contain high base metals of up to 5.45% Cu, 9.9% Pb and 12.85% Zn, with significant grade of gold and silver of up to 3.85 g/t Au dan 395 g/t Ag. From mineral assemblages, the veins might be formed at temperatures of about 250-300°C. On the basis of those mentioned characteristics, gold mineralization in Hargosari prospect is categorized into an intermediate sulfidation epithermal. Keywords: characteristics, gold, epithermal, Hargosari, Wonogiri.

In this work, mineralogical and geochemical data are presented for sulfide-rich phoscorites and carbonatites in the Kovdor massif. The PGE and Ag-bearing mineralization of bornite–chalcopyrite and Ag‑bearing mineralization of pyrrhotite–chalcopyrite associations were investigated. In carbonatite stage formation of massif, the noble metal minerals occurred during evolution of alkaline–ultrabasic melt and after separation of primary sulfide melt enriched in PGE, Au and Ag. According to the observed relationships, the minerals of PGE, Au, and Ag in bornite–chalcopyrite association are crystallized sequentially from magmatic to hydrothermal stages. Crystallization of Os, Ir, Pt and Pd minerals (erlichmanite, rustenburgite, isoferroplatinum, mertieite–II, etc.) occurred at temperature close to 480°С, while further decrease in the temperature and an increase in the Cu and Fe activity in the melt leads to the crystallization of Sb, Pb, As, Bi and Te-bearing minerals (sperrylite, tatyanaite, moncheite, stumpflite, etc.). Formation of Au and Ag-bearing minerals (electrum, silver, stromeyerite, lenaite, etc.) occurred at temperatures below 300 °C with relatively low sulfur activity. In carbonatites and phoscorites of the middle and late magmatic stages enriched with magnetite, pyrrhotite–chalcopyrite association with silver-bearing minerals was formed at temperatures below 300°C. Ag-bearing minerals were produced during hydrothermal recrystallization of Cu–Fe–Ni sulfides at temperature close to 150°C.

Exploration and mining success of a bauxite deposit rely greatly on an adequate modelling of spatial characteristics of constituent geo-variables through an understanding of deposit geology, because it is the geology that governs the process of mineralisation and geostatistics provide its meaningful role in spatial characterization of constituent geo-variables. Geostatistical modelling and subsequent study of vertical variation provide an objective means to spatial interpolation of sample values within the mineralization limits of bauxite deposit at specified cutoffs of alumina and silica. On the basis of an adequate understanding of the genesis of bauxite mineralization, an integrated study has been carried out to analyse geological, statistical and geostatistical characteristics of an east coast bauxite deposit of Odisha, India. Due to prolonged residual concentration and lateralization of Precambrian khonadalites and charnokites, the bauxite deposits formed is geologically ferruginous type (high in iron) and spatially heterogeneous. Modelling results from statistical and geostatistical analyses have been interrelated to the process of formation together with an understanding of the vertical variations in the ferruginous bauxite deposit. Spatial correlation of the constituent geo-variables reveal a range of influence varying between 170 to 310 m and ratio of nugget-to-sill variance varying between 0.58 and 0.78. Sequential Gaussian simulation (SGS) has been carried out in respect of Al2O3 and SiO2 to generate multiple realisations. The SGS study revealed that the mean, variance, and semi-variogram of SGS values are consistent with the original sample values, thereby providing an improvement over the block kriging procedure. Vertical effect analyses of kriged estimates of Al2O3 and SiO2 with depth in the bauxite deposit is phenomenally related with the depositional process of residual concentration. The modelling study emphasises the fact that geology is a key factor in mineral deposit evaluation and when combined with statistical and geostatistical procedures provides a cogent deposit appraisal.

This study illustrates the application of a geometric average integration of aeromagnetic, radiometric and satellite imagery data over a region prone to Cu‐bearing mineralization at Chahargonbad area in Kerman province of Iran. Processing aeromagnetic, radiometric and Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite data can provide exploratory insights about favourable zones in association with porphyry‐type ore occurrences, which can be synthesized through a combination of knowledge‐ and data‐driven approaches as a geometric average and be represented in a mineral prospectivity map. The existence of known deposits in a prospect region can facilitate the investigation of significant exploratory footprints extracted from airborne data by calculating each indicator layer's weight by plotting a prediction–area curve accompanied by a concentration–area fractal curve. Among various indicators, the most important ones are determined based on derived weights from the prediction–area plots to be synthesized in a single Cu favorability map. To fulfil this aim, indicator layers from airborne geophysics (magmatic bodies, magnetic lineaments and potassium radiometry) and remote‐sensing data (alterations such as argillic, phyllic, propylitic and iron oxide along with geological lineaments) were prepared and evaluated using the known porphyry Cu mineralization by the simultaneous plot of the concentration–area fractal model and the prediction–area curve to attain the ore prediction rate and the relevant occupied area of each map for weight assignment of indicators. The geometric average prospectivity model was applied to synthesize the leading indicators, and the result was compared with a multi‐class index overlay map. This study's significance lies in improvement of the performance of the mineral prospectivity/potential mapping after running a geometric average by a higher ore prediction rate of 79%, which has occupied 21% of the area as potential zones for further mining investigations.

Research subject. The gold-sulphide-quartz deposits of Central Chile are typical prospecting objects, having small ore intervals (from the first tens of centimetres to 1 m), intermittent and nested ore distribution and extremely uneven gold contents.Materials and methods. The patterns of ore mineralization distribution are considered against the background of the results of modern geophysical studies of the lithosphere: the Moho surface, density and thermal regime of the upper mantle. Detailed studies were conducted on the Yapin ore field.Results. It was shown that the faults controlling gold-sulphidequartz mineralization are derivatives of shear tectonics under the conditions of a transpression regime along the Chilean active margin. At an early stage, these faults developed in a right-shift environment, which was accompanied by the introduction of diabase dikes into the northeastern faults, and gold-sulfide-quartz mineralization superimposed on the dikes was deposited during the left-shift stage. The geological structure of the deposits in the ore field Yapin was characterized. It was shown that a diverse mineralization is developed in the ore field - copper-porphyry, IOCG-type and gold-sulphide-quartz. According to geochemical data, the latter is characterized by a clear enrichment of chalcophilic elements (Au, As, Ag, Cd, Cu, Bi, Pb, Zn, Te, Co). The marked enrichment of Bi, Te and Co ores indicates the participation of magmatic fluid in ore formation and the similarity of the mineralization of the Escondida deposit with the type of gold deposits associated with granitoid intrusions. According to geochemical features, gold-sulphide-quartz mineralization in the general zoning pattern occupies a boundary position between IOCG-type objects and copper-porphyry deposits.Conclusions. The conclusion is drawn about the independence of gold-sulphide-quartz mineralization and its difference from epithermal gold deposits. It is noted that, in the volcanic belts of the North-East of Russia, the prospects for discovering unconventional gold-sulphidequartz deposits similar to those of Central Chile are rather real.

The study of lineaments derived from optical imagery provides insights to the location of mineral deposits as they reflect geologic structures. The present study employs lineament extraction from Landsat-8 Operational Land Imager (OLI) to identify possible areas of epigenetic mineralization in the rocks of Dagbala-Atte District. Fifty-one (51) geologically significant lineaments of varying lengths and directions were extracted. Lineament map revealed three promising zones of epigenetic mineralization. These zones are those in the northeastern, central, and southwestern parts of the district. Previous reconnaissance stream sediment geochemical survey in the larger region comprising the district had selected areas that correlate well with these zones as the more prospective for metallic mineralization. Also, pedogeochemical surveys in the district revealed plausible areas underlain by rocks most likely contain different metallic mineralizations that synchronize well with these promising zones. Geological mapping and preliminary lithogeochemical survey in these zones have unveiled uranium bearing pegmatite in the northeastern zone; gold bearing marble deposit and iron oxide-copper-gold-silver mineralized silicified sheared rock along the central zone; and lead-zinc mineralized metaconglomerate in the southwestern zone. Ample geological studies of these mineralized rocks are recommended.

The Baiyangping Cu–Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt, between the Jinshajiang-Ailaoshan and Lancangjiang faults, and the deposit can be divided into eastern and western ore zones. Based upon microscope observation of ore minerals and analysis of zinc, copper, and strontium isotope composition, we conclude that: (1) the zinc isotopic compositions of sphalerite from the eastern and western ore belt of the Baiyangping polymetallic ore deposits are enriched in both the heavy (− 0.09‰ to + 0.15‰) and light (− 0.19‰ to − 0.01‰) zinc isotopes. Rayleigh fractionation is likely the additional factor controlling the observed temporal and spatial variations in zinc isotopes in the two studied ore zones. The zinc isotopic composition in the Baiyangping polymetallic Pb–Zn deposits may have the same fractionation as that of magmatic-hydrothermal, VHMS, SEDEX, and MVT deposits, as demonstrated by geological and other geochemical evidence; (2) the range of δ65Cu in massive tetrahedrite is from − 0.06‰ to + 0.12 ‰ that relates to the early stages of ore-formation, which are higher than that of venial chalcopyrite (from − 0.72‰ to − 0.07‰) formed at a late ore-forming stage in the western ore belt. Different ore-forming stages and alteration or leaching processes are likely the main factors controlling the observed variations in copper isotopes in the western ore zone; (3) the 87Sr/86Sr value of hydrothermal calcite in eastern (0.7080–0.7093) and western (0.7085–0.7113) ore belt suggested that mineralization of early calcite, with 87Sr/86Sr values much higher than in ancient Late Triassic seawater, may be related to recrystallization from a radiogenic Sr-rich or silicifying fluid, either from the strata that the ore-forming fluid flows through or from other fluids.

The recently developed fluorite (U–Th)/He thermochronology (FHe) technique was applied to date fluorite mineralization and elucidate the exhumation history of the Mazandaran Fluorspar Mining District (MFMD) located in the east Central Alborz Mountains, Iran. A total of 32 fluorite single-crystal samples from four Middle Triassic carbonate-hosted fluorite deposits were dated. The presented FHe ages range between c. 85 Ma (age of fluorite mineralization) and c. 20 Ma (erosional cooling during the exhumation of the Alborz Mountains). The Late Cretaceous FHe ages (i.e. 84.5 ± 3.6, 78.8 ± 4.4 and 72.3 ± 3.5 Ma) are interpreted as the age of mineralization and confirm an epigenetic origin for ore mineralization in the MFMD, likely a result of prolonged hydrothermal circulation of basinal brines through potential source rocks. Most FHe ages scatter around the Eocene Epoch (55.4 ± 3.9 to 33.1 ± 1.7 Ma), recording an important cooling event after heating by regional magmatism in an extensional tectonic regime. Cooling of the heated fluorites, as a result of thermal relaxation in response to geothermal gradient re-equilibration after the end of magmatism, or exhumation cooling during extensional tectonics characterized by lower amount of erosion are most probably the causes of the recorded Eocene FHe cooling ages. Oligocene–Miocene FHe ages (i.e. 27.6 ± 1.4 to 19.5 ± 1.1 Ma) are related to the accelerated uplift of the whole Alborz Mountains, possibly as a result of the initial collision between the Afro-Arabian and Eurasian plates further to the south.

А new Vovchansk Uranium Ore district is allocated within the Orikhiv-Pavlohrad structural-metallogenic zone (SMZ) of the Azov metallogenic region. It is represented by Dibrova REE-U-Th deposit and a number of less studied ore occurrences. This deposit, according to ore mineralogy and age, geological and structural features, can be related to potassium-uranium metasomatite type. Dibrova deposit is considered to be possible analogue of mineralization of the Central Ukrainian Uranium Ore district. Among the main diagnostic characteristics of Dibrova deposit are: 1) location within the Mesoarchean trough-like structure superimposed on the Paleoarchean basement. 2) Spacial and genetic association with Paleoproterozoic two-feldspar granitoids of Dibrova type, which are considered to be related to Saltychia intrusive complex. 3) Regional and local faults, favorable for emplacement of numerous bodies of aplite-pegmatitic granitoids and associated intensive metasomatic alterations of rocks. The flexural fold was formed at the intersection of multidirectional faults, which is also favorable for ore mineralization. 4) Mineralization is confined to metasomatically altered aplite-pegmatites, less often to microcline quartzites of Dibrova suite. 5) K2O/Na2O ratio of ore-bearing granitoids reaches 3.5 and thorium-uranium ratio varies from 1.0 to 4.0. 6) Ores are composed by quartz (70–90 %) as predominant mineral and microcline. Minor minerals (up to 10–15 %) are represented by sillimanite, muscovite, biotite. 7) Accessory minerals include monazite, zircon, rutile, nasturan, brannerite, uraninite, molybdenite. 8) Among trace elements are niobium, lead, molybdenum, bismuth, copper, zinc and tin. Economic REE-U-Th mineralization was da­ted at 1.9–2.2 billion years. It is formed through circulation of hydrothermal-metasomatic fluids associated with the emplacement of Paleoproterozoic aplite-pegmatitic granites of the Dibrova type. Study of monazite and uraninite inclusions by the CHIME techniques confirms the Paleoproterozoic age of mineralization, 2085–2115 Ma. At the same time, the influence of Mesoarchean Yanvarske granitoids for the formation of REE mineralization during early pre-ore stage is not excluded.

The main aspects of perspectives and ways to create the gold mining industry of Ukraine as a source of replenishment of gold and foreign exchange reserves and an integral part of high-tech production have been considered. The latest EU trends in the mining industry, which have led to an increase of investment in geological exploration and, as a consequence, discovery and exploitation of new gold deposits, have been described. Brief information on the gold-bearing Archean-Proterozoic complexes of the world, which indicates a high concentration of deposits within the gold ore areas, has been given. The concentration of deposits is observed in zones of tectonic disturbance and metasomatic change of rock complexes, contrasting in composition. The geological characteristics of the most studied gold ore manifestations of the Ukrainian Shield (USh), where after additional studies it is possible to indicate industrial concentrations with significant increase of gold resources and start the production, have been presented. Similarities between USh manifestations and known Precambrian gold ore deposits of the world have been demonstrated. These are gold ore deposits of Precambrian green-stone belts and metamorphogenic-hydrothermal systems, so-called shear-zones of orogenic mesothermal type. Gold deposition is generally associated with sulfidization and associated quartzization and/or carbonation, the mineralization stage is preceded by albitization. Gold deposits were formed in several episodes over 2,1–1,8 billion years. Mostly native gold has a high proof quality, inherent associations with arsenic, tellurium and bismuth. The process of ore formation is multi-stage. The state of exploration and commercial attractiveness of USh gold ore objects for further works have been described by the example of the Maiske deposit. Methodological approaches to geological and economic assessment of gold ore objects have been considered. It has been demonstrated that determination of the gold content has been performed without taking into account the presence of gold particles of significant size and therefore its average content cannot be considered proven. Lack of information obtained during mining exploration leaves room for significant changes in the spatial and qualitative parameters of mineralization. Main unresolved problems, detected during researches, and ways to solve them have been outlined. Mining exploration of certain deposits will highlight the prospects of previously established gold ore areas.

The Dahongliutan rare-metal pegmatite deposit, associated with the pegmatite dikes hosted by Dahongliutan pluton and metasedimentary rocks, is a new discovered Li–Be deposit in the the West Kunlun ...

Marmato, Colombia, has been an important centre of gold mining since before the first Spanish colonizers arrived in 1536. The Marmato deposit is hosted in a dacite and andesite porphyry stock as sheeted sulphide-rich veinlet systems. The district is currently experiencing a surge in both major mining projects and artisanal mining, driven by sustained high gold prices. Ore from small-scale and artisanal gold mining is processed in numerous small mills (entables) around Marmato, which impact surface water quality through the discharge of milled waste rock slurry, highly alkaline cyanide-treated effluent, and high dissolved metal loads. To investigate the impact of artisanal mining and ore processing, water samples were collected in January 2012 from streams around Marmato. The average dissolved metal concentrations in impacted streams were Zn, 78 mg L−1; Pb, 0.43 mg L−1; Cu, 403 µg L−1 Cd, 255 µg L−1; As, 235 µg L−1; Ni, 67 µg L−1; Co, 55 µg L−1; Sb, 7 µg L−1; and Hg, 42 ng L−1, exceeding World Health Organization drinking water guidelines. In addition, arsenic speciation was conducted in-situ and indicated that 91–95% of inorganic arsenic species is in the form of As(V). Spatial analysis of the data suggests that entables processing ore for artisanal miners are the main contributor to water pollution, with high sediment loads, alkalinity and elevated concentrations of dissolved arsenic, cadmium, mercury and lead, caused by the processing of gold-bearing sulphides in the entables. Geochemical data from surface water were compared to a comprehensive data set of whole rock analyses from drill core and channel samples from the deposit, indicating that the deposit is significantly enriched in gold, silver, lead, zinc, arsenic, antimony, and cadmium compared to crustal averages, which is reflected in the surface water geochemistry. However, elevated mercury levels in surface water cannot be explained by enrichment of mercury in the deposit and strongly suggest that mercury is being added to concentrates during ore processing to amalgamate fine gold.

The article describes Reza gold deposit of Ugur exploration area located in Geda- bek Ore District of the Lesser Caucasus in NW of Azerbaijan. It is established that main mineralization in the Reza gold deposit consists of hematite-barite-quartz-kaoline veins- veinlets and breccia, pyrite stock-stockverk and quartz-sulfide veins. On the main orebody surface center secondary quartzites with vein-veinlets barite-hematite mineralization have occured over which remain accumulations of hydrous ferric oxides cementing breccias of quartz and secondary quartzites. “Reddish mass” is also observed in erosion parts, being an oxidation product of stock and stockverk limonite-hematite ores. Representing typical gossans, these accumulations by the data of trenches for thickness about 5-10 m contain gold 0.3-3.5 ppm and silver 1.0-45.0 ppm. There are three zones of gold mineralization within the Reza gold deposit: oxide mineralization; transition zone mineralization; sulfide mineralization. The oxide gold mineraliza- tion consists of clay-gravel weathering crust of kaolinite type. The gold-bearing mineralization has been oxidized to a depth of ap- proximately 50-100 meters. Typically, the gold mineralization is coarser and a minor increase in gold grade occurs within the oxides compared to the original rocks. The nugget effect increase in the gold grade of the oxides does not exceed approximately 10%. Deposit alteration signature has characteristics which suggest the current outcrop level may be near the top of a mineralized, gold-bearing high sulfidation epithermal (HSE) system. The gold mineralization at the deposit is interpreted as forming in shallow high sulfidation epith- ermal systems. The mineralization has been noted in well-confined hydrothermal breccia and associated with pyrite stock-stockwork. The majority of the deposit material and current estimates are formed within the barite-hematite-quartz-kaoline mineralization in the secondary quartzite rocks. The main brecciation and stockwork are hosted within secondary quartzite, sometime massive silicified andesite porphyritic rocks.

Magmatic processes occurred during the Miocene period caused the formation of epithermal gold deposits in Cibaliung area. The deposit has previously been investigated through geological surveys which basically only covers the surface aspect, so in this study a subsurface analysis was carried out through magnetic and IP surveys to determine the distribution and continuity of the gold deposits. The magnetic survey was conducted over an area of about 3 km2 with sampling interval 20 m east and 100 m north. The magnetic data were processed using Oasis Montaj with magnetic intensity map as an output, which was then interpreted to determine the presence of structures and magnetite destruction zones as mineralization clues. The IP survey was conducted on 20 east-west oriented lines with length of about 1.2 km. The electrode configuration used is Wenner with 25 m spacing. IP data were processed using RES2DINV software to eliminate bad datum points and invert the apparent chargeability values into the true ones. IP data are then interpreted to clearly determine the position, direction, and distribution of gold mineralization body by detecting the presence of sulfide minerals as ligands carrying gold. Magnetic data analysis shows that gold mineralization tends to occur at low magnetic anomaly, ranging from 37 nT to 240 nT and generally associated with northwest-oriented structures. The mineralization zone is found in four main vein zones with resistivity and chargeability values < 51 Ωm and > 50 ms.

The first data of U–Pb isotopic study (LA–ICP–MS method) of zircon from tonalite–granodiorite forming a dominant part of the “trondhjemite” intrusive massif at the giant Tyrnyauz W–Mo deposit (North Caucasus) is presented. The concordant zircon isotopic U–Pb age obtained (302 ± 4 Ma) indicates a Late Paleozoic (Late Carboniferous–Early Permian) age of crystallization of these rocks. This is consistent with the Late Paleozoic epoch of W-bearing magmatism and related W mineralization in the North Caucasus (Peredovoi Ridge) and allows the possibility of the Late Paleozoic age of the large bodies of altered skarn with W mineralization at the Tyrnyauz deposit.

In this paper, the east ore section of the Pulang porphyry copper deposit is selected as the research object. The micro-thermometer and laser Raman spectroscopic technique are utilized to study the parameters of ore-forming fluids such as pressure, temperature, and compositions. In the meantime, the fractal models, including the perimeter-area (P-A) model and number-size (N-S) model, are introduced to quantify the shape of fluid inclusions, and distinguish the stages of ore-forming fluids, respectively. The results show that the types of fluid inclusions are diversified, namely two-phase liquid-rich type, two-phase vapor-rich type, three-phase CO2-rich type, three-phase halite-bearing type and pure liquid type. The fluids of main mineralization stage are characterized by medium-high temperature (170.2–421.4 °C), medium-high salinity (9.3 wt.%–33.3 wt.%), and low density (0.73–1.06 g/cm3). With the migration and evolution, the temperature, salinity, and pressure of ore-forming fluids gradually decrease, while the density of fluids increases. The liquid-phase compositions mainly include H2O, and the vapor-phase compositions consist of H2O, CH4, N2, and CO2, indicating the characteristics of reducing fluids and the mixing of atmospheric precipitation. In general, the characteristics of ore-forming fluids in the east ore section are similar to those of the first mining area, suggesting that the ore-forming fluids in the east ore section may not migrate from the first mining area. And the east ore section may be a relatively independent metallogenic system. Moreover, the fractal analysis results demonstrate that the shape of fluid inclusions formed in the same hydrothermal activity features self-similarity. The DAP values of fluid inclusions in B veins, ED veins, and D veins are 1.04, 1.06 and 1.10, respectively, showing a gradually increasing trend from the main stage to the late stage of mineralization. Meanwhile, the shape of fluid inclusions ranging from B veins to D veins becomes increasingly irregular. It also reveals that the homogenization temperature satisfies fractal distribution with four scale-invariant intervals, suggesting that all B veins, ED veins, and D veins have experienced at least four hydrothermal activities. Compared with histogram, the N-S fractal model is able to describe the distribution characteristics of the ore-forming fluids’ homogenization temperature more precisely. Therefore, it presents a potential tool for the stage division of ore-forming fluids. This research provides information about the characteristics of ore-forming fluids in the east ore section of the Pulang porphyry copper deposit, which is beneficial for further exploration in this region, and the extension of the application of fractal models in the study of fluid inclusions. However, further testing of fractal models on the fluid inclusion study is warranted to fully determine the universality.