Ore Components Research Articles

Understanding Trace Iron and Chromium Incorporation During Gibbsite Crystallization and Effects on Mineral Dissolution.

Incorporation of pollutants, e.g., heavy metals, or critical elements, e.g., lithium, as impurities in mineral phases can significantly affect their mobility or sequestration in the environment. Even when present at low concentrations, impurities can alter the solubility and reactivity of the host mineral. In this study, we investigate the incorporation of trace amounts of iron (Fe3+) and chromium (Cr3+) during the crystal growth of the aluminum (Al3+) hydroxide, gibbsite, a major component of bauxite ores, an important soil mineral, and a dominant mineral phase in stored radioactive wastes. Using a comprehensive suite of analytical techniques, we show that both Cr3+ and Fe3+ can be incorporated into the gibbsite lattice during coprecipitation by replacing Al3+ in octahedral sites. These small amounts are consistent with limited to no structural isomorphism shared between Al3+ and Cr3+/Fe3+ hydroxide precipitates, nor room temperature miscibility of their isostructural M2O3 oxide forms, in contrast with oxyhydroxide forms where Al3+ and Fe3+ share similar structural topologies. Despite the limited uptake of Cr3+/Fe3+, we show that these impurities have significant implications for gibbsite dissolution behavior. The limited uptake of Cr3+/Fe3+ (e.g. 0.43% Cr3+ and 0.4% Fe3+), we show that these impurities have significant implications for gibbsite dissolution behavior and subsequent reactivity in complex environments.

Genesis of the Qingchayuan Flake Graphite Deposit in the Huangling Dome of Yangtze Block, South China

The Qingchayuan flake graphite deposit is located in the Huangling Dome, which represents a part of the Yangtze Block in South China. This deposit is a major and highly typical flake graphite deposit within this metallogenic region. The graphite ores are found within graphite-bearing mica schist and graphite-bearing biotite–plagioclase gneiss. The fixed carbon content varies from 3.52 to 13.78% with an average of 7.83%. The major element analysis shows that the main chemical components of the Qingchayuan flake graphite ore are SiO2, Al2O3, TFe2O3, and K2O. The carbon isotope study of the graphite ore indicates light carbon values ranging from −22.80 to −26.72‰, suggesting that it has a biogenic origin. In addition, the sulfur isotope values of the graphite samples range from −10.67 to −14.58‰, indicating the formation of the graphite deposit is related to biological processes. The presence of traces of migmatization around the graphite deposit indicates that the graphite has undergone ultra-high temperatures during the formation process. The origin of the Qingchayuan flake graphite deposit is explained by a two-stage genetic model, which involves material deposition and regional metamorphism (including migmatization). Firstly, after the deposition of carbonaceous material and its conversion into graphite by regional metamorphism, the graphite might have undergone recrystallization, resulting in the development of big flakes due to migmatization. This model is supported by previous studies and newly collected information.

High precision blood lead radiogenic isotope signatures in a community exposed to Pb contaminated soils and implications for the current Pb exposure of the European population

Our study provides the most comprehensive dataset for high-precision radiogenic isotopes of lead (Pb) in blood for the western European population. It investigates their potential for elucidating the contribution of soil Pb to blood Pb using a human biomonitoring survey involving 81 adults and 4 children living in the urban area of Liège (Belgium). Soils in the area show moderate (median of 360 mg/kg) to high (95th percentile of 1000 mg/kg) Pb concentrations, due to former metal processing activities. Blood lead levels (BLL) measured in the study population are, on average, quantitatively consistent with a ∼ 20 % increase due to the exposure to Pb from soils, as estimated by a single-compartment biokinetic model. Consistently, its isotopic composition does not represent an endmember that fully accounts for the variability of Blood lead isotope (BLI) compositions measured in the study population. While some individuals show more thorogenic BLI ratios (relatively more enriched in 208Pb), which could be consistent with a greater exposure to local soils and/or by their country of birth, the BLI data mostly follow a trend roughly parallel to the European Standard Lead Pollution (ESLP) line, within the European leaded gasoline field, even two decades after the withdrawal of this source. Differences in BLI are probably associated with factors related to the presence of Pb in dwellings (pipes, paint) and drinking water distribution system, suggesting that the anthropogenic Pb in use, relevant to human exposure, may contain ore components of different origins, including the Australian Pb ore signature.

Comparative mineralogy, geochemistry and petrology of aillikites and carbonatites, ijolites, melteigites and Ne-syenites of Beloziminsky massif- insights to origin

Beloziminsky alkaline ultramafic carbonatite massif (BZM) includes carbonatites, ijolites, meltegites, syenites (CIMS) layers and bodies and aillikites intrusions (∼ 645 - 621 Ma) within massif and Yuzhnaya pipe (YuP), locating in 16 km eastward. Comparisons of mineralogy and geochemistry of 19 CIMS samples (>1100 analyses) and > 16 aillikites (>2300 analyses) locating within the BZM and accounting aillikite minerals from pipes and dykes outside the massif (Ashchepkov et al., 2020) (all together >5400) reveal great difference for rock-forming minerals and less for the accessories. The analyses of the pyroxenes in aillikite correspond to mantle Cr-diopside xenocrysts and megacrystic augites. The low-Na Ti-augites and diopsides as well as aegirines prevail in carbonatites-ijolites-melteigites –syenites intrusive bodies (CIMS suit). Amphiboles show long trend from hornblendes to richterites.The in dolomitic carbonates include also admixtures of Na, K, Ba and Ca- carbonatites often contain Sr, The aillikitic carbonates are rich in Mg or Ca and CIMS rocks together with Ca-Mg carbonatites also often include siderites.Thermobarometry for YuP and Yuzhnaya pipe outside BZM containing Cr-diopsides, Cr-phlogopites, Cr-spinels (P ∼ 4–2 GPa, T ∼ 800–1250°C) and xenocrysts of augites with elevated HFSE, U, Th. Al-augites tracing 90 mW/m2 geotherm.The huge thermal impact of plume produced Rodinia breakdown series of ultramafic-alkaline-carbonatite massifs. Initially aillikites in mantle originated due to melting of carbonated metasomatites containing ilmenite, perovskites, apatites, amphiboles and phlogopites created by subduction related melts. Additional enrichment in ore components may occurred in low crust due to liquation. The aillikites inside BZM contain low-temperature clinopyroxenes tracing steep advective geotherm (0.4–1.5 GPa) and clots related to intermediate magma chambers together with CIMS pyroxenes and amphiboles. This suggests that the liquation of aillikites was accompanied later by density separation and AFC fractionation with the participation of crust material.Trace elements (especially REE) in silicate minerals, carbonates, apatites, and accessories (perovskites, pyrochlores, monazites, columbites zircons, ancylites etc). show general rise of the REE levels and La/Ybn rations from aillikites to ijolites and later to Fe-cabonatites. Presence of zircons, monazites, columbite- tantalites and other Zr-Hf and Ta-Nb minerals (perovskite, tantalites etc) in BZM aillikites occurred due to the mixing with the silicate melts with the carbonate-rich magmas in deep levels and later in massif. In aillikites any of them are of xenocrysts.Apatites and perovskites show high REE levels. The carbonate-silicate magmas passed through the system of polybaric magmatic chambers and liquated carbonatites. Late aillikites captured and mixed all varieties and xenocrysts.

The Chain of Processes Forming Porphyry Copper Deposits—An Invited Paper

Abstract Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies. On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative. Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas. Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization. Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides. Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits. Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels. Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.

Improving the efficiency of the preparation of agglomeration charge

Improving the efficiency of averaging of agglomeration charges containing finely dispersed materials and reducing fluctuations in the chemical composition of the agglomerate is an actual topic since sintering plants do not have enough equipment for the complete preparation of the agglomeration charge, namely averaging. In addition, the supply of finely dispersed components of iron ore concentrate and iron-containing sludge to the warehouse for averaging and the processes of stack formation and disassembly are accompanied by disorganized structure formation. Solving this issue will improve agglomerate quality and increase agglomeration machines' productivity. A method of preparing agglomeration charge is proposed. This method involves averaging the mixture after equalizing its granulometric composition, which minimizes material segregation during stack formation and disassembly. The leveling of the granulometric composition of the mixture is carried out by processing it in mixers at natural humidity, which leads to the destruction of locally over-moistened micro volumes of sludge and concentrate and finishing the mixture at optimal humidity, which contributes to the preferential formation of granules of class 1.6...10.0 mm. A component for crushing is added to the mixture in the amount of 10 ...40 % of the weight of the mixture to intensify the process of crushing in the mixer. Granulation of the charge before averaging and storage in the warehouse contributes to eliminating the phenomenon of caking, the unorganized formation of macrostructures in the process of loading the material. This ultimately improves the quality of the agglomerate in terms of strength indicators. The method will reduce fluctuations in the agglomerate's chemical composition in terms of iron content and basicity while increasing the productivity of sinter machines and strengthening the heat. Taken together, this allows us to conclude about its feasibility and the possibility of its introduction into industry.

Spectral Visualization of Alloy Reactions during Laser Melting

Laser materials processing includes rapid heating to possibly high temperatures and rapid cooling of the illuminated materials. The material reactions can show significant deviations from equilibrium processing. During processing of complex materials and material combinations, it is mainly unknown how the materials react and mix. However, it is important to know which chemical elements or compounds are present in the material to define the alloy. In addition, their distribution after rapid cooling needs to be better understood. Therefore, such alloy changes at rapid heating induced by laser illumination were created as pre-placed and pre-mixed powder nuggets. The energy input and the material ratio between the powder components were varied to identify characteristic responses. For the detection of reaction durations and mixing characteristics, the vapor plume content was assumed to contain the necessary information. Spectral measurements of the plume were used to identify indicators about process behaviors. It was seen that the spectral data give indications about the chemical reactions in the melt pool. The reactions of iron ore components with aluminum seem to require laser illumination to finish completely, although the thermite reaction should maintain the chemical reaction, likely due to the required melt mixing that enables the interaction of the reacting partners at all.

Mineralogy and Distribution of REE in Oxidised Ores of the Mount Weld Laterite Deposit, Western Australia

The Mount Weld rare earth element (REE) deposit, Western Australia, is one of the largest of its type on Earth. Current mining exploits the high-grade weathered goethite-bearing resource that lies above, and which represents the weathering product of a subjacent carbonatite. The mineralogy, petrography, deportment of lanthanides among the different components, and variation in mineral speciation, textures, and chemistry are examined. Microanalysis, involving scanning electron microscope (SEM) imaging, electron probe microanalysis (EPMA) and laser ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS), was conducted on sized fractions of three crushed and ground laterite ore samples from current and planned production, and a representative sample from the underlying carbonatite. High-magnification imaging of particles in laterite samples show that individual REE-bearing phases are fine-grained and extend in size well below the micron-scale. Nanoscale inclusions of REE-phosphates are observed in apatite, Fe-(Mn)-(hydr)oxides, and quartz, among others. These have the appearance, particularly in fluorapatite, of pervasive, ultrafine dusty domains. Apart from the discrete REE minerals and abundant nano- to micron-scale inclusions in gangue, all ore components analysed by LA-ICP-MS contain trace to minor levels of REEs within their structures. This includes apatite, where low levels of REE are confirmed in preserved igneous apatite, but also Fe- and Mn-(hydr)oxides in which concentrations of hundreds, even thousands of ppm are measured. This is significant given that Fe-(Mn)-(hydr)oxides are the most abundant component of the laterite and points to extensive mobility and redistribution of REEs, and especially HREE, during progressive lateritisation. Late-formed minerals, notably tiny grains of cerianite, reflect a shift to oxidising conditions. REE-fluorocarbonates are the main host for REEs in carbonatite and are systematically replaced by hydrated, Ca-bearing REE-phosphates (largely rhabdophane). The latter displays varied compositions but is characteristically enriched in HREE relative to monazite in the same sample. Fine-grained, compositionally heterogeneous rhabdophane is accompanied by minor amounts of other paragenetically late, hydrated phosphates with enhanced MREE/HREE relative to LREE (although still LREE-dominant). Minor, relict xenotime and zircon are significant HREE carriers. Ilmenite and pyrochlore group members contain REE but contribute only negligibly to the overall REE budget. Although the proportions of individual mineral species differ, the chemistry of key ore components are similar in different laterite samples from the current resource. Mineral signatures are, however, subtly different in the lower grade southeastern part of the deposit, including higher concentrations of HREE relative to LREE in monazite, rhabdophane, florencite and Fe-(Mn)-(hydr)oxides.

Quartz-Hosted Fluid Inclusions in Commercial Ores of Various Type at the Verninskoe Gold Deposit, Bodaibo District, Russia

The paper presents data on quartz-hosted fluid inclusions in commercial ores of various type (veinlet−disseminated and vein) of the Verninskoe gold deposit. The ores of various types were found out to significantly vary in the values of some of their physicochemical parameters of the fluids and in the composition of these fluids. The fluids that formed the gold veins have a somewhat higher initial temperature (356–246°C), a higher density of carbon dioxide in gas inclusions (1.00–0.84 g/cm3), and a higher fluid pressure (3170–1390 bar) than those of the fluids that formed the veinlet–disseminated ores (330–252°C, 0.87–0.54 g/cm3, and 1960–570 bar, respectively). The fluids that formed the gold veins were enriched in CО2, Sr, Ag, Ga, Ge, Mn, Fe, Ni, Sn, Ba, and REE, whereas the fluids that formed veinlet–disseminated mineralization were richer in HCO−3, Br, Sb, V, and Au. This situations may be explained by the interaction of the deep fluid with the terrigenous host rocks in the course of ore deposition. When vein quartz crystallized in relatively wide fractures, the fluid interacted with host rocks and changed not as much as when the veinlet−disseminated ores were formed in narrow fractures. The initial parameters of the fluid that formed the vein quartz were thus the closest to the characteristics of the fluid that transported the ore components, and the comparison of these data with the parameters of the fluids that formed the veinlet–disseminated mineralization demonstrates that they changed in the course of ore deposition. The mineral-forming fluids likely came from a deep-sitting source, and the mineral-forming processes may have involve granitoid-derived fluids.

The Use of Typomorphic Features of Placer Gold of the Anabar Region for Determining Its Sources

Typomorphic features of placer gold of the Anabar region were studied as predictive-exploration criteria. The target of the study was to determine the typomorphic features of placer gold related to the intermediate sources (paleo-placers) and the supposed nearby primary ore occurrences. Two varieties of placer gold were identified. The first variety is well-rounded high-fineness lamellar gold with a highly modified internal structure. This native gold is associated with intermediate sources, Neogene–Quaternary watershed pebble beds. The second type includes slightly rounded gold with a wide variation in fineness (494‰–999‰). Its indicator is a block heterophase internal structure. The set of typomorphic features of this variety of placer gold indicates the vicinity of the primary source, what was the prerequisite for constructing prospecting traverses in order to find ore occurrences. As a result of these studies, hydrothermal-metasomatic formations with gold-sulfide mineralization were identified. The main primary substrate for them is fractured near-fault carbonate rocks of the Cambrian and Vendian–Cambrian age. Along with this, hydrothermalites developed on slightly cemented fine-pebble quartz conglomerates of the Middle Permian age were found in the core of exploration wells. Two types of metasomatic rocks are identified: quartz-potassium feldspar and jasperoid. The main ore minerals were galena and pyrite, different ratios by sites were revealed. Gold was identified in the form of small particles in the carbonate and siliceous substrate of hydrothermal-metasomatic formations. The lithological factor was one of the leading favorable factors for the ore formation due to the presence of near-fault highly permeable fractured carbonate and slightly cemented terrigenous rocks. The structural control of the studied ore occurrences is determined by their localization in the Mayat–Logoy and Dogoy–Kuoy faults of the Molodo–Popigay system of discontinuous faults. We assume a two-stage formation of the gold ore occurrences: during the first stage, the ore components in the form of primary hydrothermal-sedimentary ores in the near-gault zones were formed. The second stage was related to the processes of the Mesozoic tectonic-magmatic activation, when the intrusion of basite dikes initiated the mobilization of ore components the gold-sulfide occurrences were formed in the near-fault zone as a result of silicic-potassic metasomatosis of the carbonate and terrigenous rocks.

To the features of the mechanism of ore formation

To date, there is no doubt that in the Paleozoic the crust of the Urals was formed in a setting of tangential compression as a result of manifestations of several tectonic cycles, each of which was due to the thrust of the oceanic crust on the continental base. As a result, the geochemical interaction of the compositions of volcanogenic-sedimentary formations, which evolved in accordance with the increase in tectonic compression from minimum to maximum values, was determined. Significantly increased tectonic loads lead to squeezing of eruption channels, cessation of magmatic activity, widespread development of flysch and olistostromal strata, massive thrusting and digging of previously formed formations, and the appearance of anatectic granite intrusions. The first half of the tectonic cycle, as a rule, evolutionary, led to the development of igneous rocks — the main carriers of ore components in a dispersed state. The second half is deformation, in addition to the listed processes, it contributed to the concentration of useful components in one way or another in the deposit. In accordance with the model of the formation of the earth’s crust, the epochs of ore formation are simultaneous with the thrusting and are genetically determined by it.

Metal Content of Brown Coals from the Raichikhinskoe Deposit (Priamurie, Far East): Conditions of Accumulation and Distribution and Prospects for Development

The formation of metal-bearing coalfields of the Raichikhinskoe deposit in the conjugation zone of distributive provinces of the Bureya uplift and coal-accumulation areas of the Zeya–Bureya sedimentary basin was studied. It was established that it occurred under conditions of the successive extraction of ore components from weathering crusts of the Bureya uplift, transportation, and unloading in the paleodelta of the Bureya River. These processes proceeded synchronously with volcanic activity in the Sikhote-Alin orogenic belt, which is associated with the supply of volcanic ash. The association of these events made it possible to distinguish two types of enrichment of the Raichikha coals in rare earth elements and yttrium (REY): terrigenous with the supply of REY by surface waters and combined terrigenous volcanogenic associated with the shedding and leaching of acidic and alkaline volcanic ash. The cerium group lanthanides predominate in coals and their combustion products. The largest fraction of REY was contained in fly ash (0.11% on a total weight basis). The mechanisms of accumulation of ore components at the stage of peat deposits are considered from the standpoint of the localization of trace ore components as clastogenic mineral forms and under the conditions of interaction of ore solutions with the organic environment of peat bogs. The quality of REY was assessed, and the most enriched sections of the Verkhnii layer were identified. Prospects for the extraction of lanthanides from coal are considered from the standpoint of the possible recovery of a number of rare, nonferrous, and noble metals in this process.

Physico-chemical studies of technogenic gold-containing wastes of the Aksu deposit

To develop a comprehensive technology for processing technogenic gold-containing waste, a representative sample of technogenic mineral formations of the Aksu deposits was selected. The average representative sample was studied using chemical, X-ray phase, mineralogical, X-ray spectral and electron microscopic analysis methods. The article presents physico-chemical studies of gold-bearing technogenic mineral formations of the Aksu deposit. According to the results of X-ray phase analysis, it was found that the main phase components are the following minerals: α-quartz - 63.2%, barite - 26.8%, muscovite - 6.3% and gypsum - 3.8%. Electron probe scanning revealed the presence of gold in the form of thin inclusions in rock-forming minerals. With the help of rational analysis, it was found that the proportion of free gold in the form of accretions with ore components in them is 7.18%. It was found that the main part of gold - 64.7% - is in the sulfide sample in the form of films coated with quartz, iron hydroxides, carbonates, chlorites and other minerals. According to the results of assay and atomic adsorption, gold in technogenic mineral formations varies from 1.11 to 1.28 g/t. The sieve analysis of technogenic mineral formations of the Aksu deposit showed that the initial sample is mainly represented by a class of -0.25+0.074 mm. Based on the data of analytical studies, it can be seen that the studied samples of stale tails of TMOS are a rather complex object for extracting gold, which is associated with the above-described features of the material composition. As well as the thin inclusiveness of gold in sulfides determine the persistent nature of the raw material under study. The results obtained in the physico-chemical study of technogenic mineral formations of the Aksu deposit will become the basis for choosing the technology for processing this raw material.

GEOCHEMICAL CHARACTERISTICS OF THE MAIN ORE COMPONENTS IN THE GOSHGARCHAY PORPHYRY-EPITHERMAL SYSTEM (LESSER CAUCASUS, AZERBAIJAN)

The article deals with the determining characteristics of ore elements in the Goshgarchay porphyry-epithermal system. The genetic and geochemical characteristics of the main ore components were studied, and close positive and negative relationships between pairs of elements were determined by correlation analysis on the selected elements. According to the results of the cluster analysis, the geochemical associations that allow the localization of the development area of mineralization at different stages of formation of the porphyry-epithermal system were analyzed. The following series of stable elements, which are typical for hydrothermal deposits, are distinguished among the ore elements of the host and ore-bearing intrusive rocks: Cu, Mo, Pb, Zn, Ag, Ni, Co, Mn, Ti, Cr, V, Sr, etc. This group of elements is considered to be the indicator elements of the copper-porphyry deposit within the porphyry-epithermal system. It has been determined that correlations between elements in copper-porphyry mineralization are characterized by a wide range of element impurities. It includes both chalcophile (As, Sb, Cu, Bi, Cd, Ga, In, Ge, Au, Ag, Te) and siderophile (Co, Ni, Mo, Fe, Cr) elements. The range of values of vertical geochemical zonality on individual sections of the deposit allows to assess the level of the erosion truncation of occurrences in the porphyry-epithermal system.

STRUCTURAL AND LITHOLOGICAL CHARACTERISTICS OF ZIRCON-ILMENITE PLASTERS FROM THE MOKRI-YALY GROUP

The article presents the general geological characteristics and paleogeographic conditions of the formation of the Mokri- Yaly group of zircon-ilmenite placers. The studied region is characterized by a complex geological structure and polyfacies composition. The deposits are located in the area of Precambrian folding, that had been complicated by young tectonic shifts. The Tatarske, Manuilske and Zlatoustivske deposits belong to the most promising placers of this group. They represent alluvial and coastal-marine sandy deposits (Oligocene-Miocene). The main placer minerals are ilmenite (17.5—18.2 kg/m3) and zircon (3.3—5.2 kg/m3). The distribution map of ilmenite and zircon over the area of the Tatarske, Manuilske and Zlatoustivske deposits were constracted by modern GIS-technologies. This maps are included: relief of the bottom surface, sole and roof of the ore deposit of the Mokri-Yaly depression, maps of the planar distribution of the contents of ilmenite, zircon, and the thickness of the ore stratum, distribution columns of ilmenite and zircon in the vertical cross section of the wells of each of the deposits. General ore-bearing characteristic of Tatarske deposit are layer thickness — 5 m, overburden thickness — 7.2 m, zircon content 4.2 kg/m3, ilmenite — 15.1 kg/m3; Manuilske deposit are layer thickness — 10 m, overburden thickness — to 20 m, zircon content 5.5 kg/m3, ilmenite — 26 kg/m3; Manuilske deposit are layer thickness — 3.8 m, overburden thickness — 7.2 m, zircon content 3.8 kg/m3, ilmenite — 18.4 kg/m3. The structural (structure of the reservoir, hypsometry of the deposit, relief of the modern surface, tectonic conditions, etc.) and lithological (granulometric and mineralogical features, lithofacies, distribution of ore components, etc.) characteristics were discribed (as the Mokri-Yaly group in general , as specifically the Tatarske, Manuilske and Zlatoustivske zircon-ilmenite deposits).

Mineralogical and geological characteristics of the Nui Phao tungsten deposit and its resource in the Dai Tu area, northeastern Vietnam

Typically, granitic intrusions that document the lengthy and intricate history of the magmatic-hydrothermal system are linked to tungsten deposits. Uncertainty persists about the genetic relationship between tungsten mineralization and magmatic-hydrothermal development. The primary tungsten deposit in the Dai Tu region, known as the Nui Phao deposit, has been the subject of a petrographical and microscopic examination. Tungsten mineralization in the Dai Tu area often occurs in association with the formation of skarn and greisen bodies, and it has drawn much attention from geoscientists. Based on microscopic observations, tungsten ores can be divided into three mineralization stages, namely skarnisation, greisenization, and hydrothermal stage. To examine the geochemical features of the tungsten ores, the SEM-EDS and Microscope analytical methods were performed in this study. Research results indicate that the Nui Phao tungsten deposit was formed due to different tectonic and magmatism episodes. Accordingly, the Nui Phao tungsten deposit is relatively complicated with the multi-sources of ore components. Most of the tungsten ore was accumulated in association with the metasomatism between the Ordovician-Silurian carbonate-terrigenous sedimentary rocks of the Phu Ngu formation and the Cretaceous two-mica granite of the Pia Oac complex. The research results indicate that tungsten resources obtained at levels 122 and 333 are about 227.6 thousand tons. Moreover, the hydrothermal alteration and metasomatism in the study area are influenced by at least three metasomatic episodes, including skarnisation, greisenisation, and the late hydrothermal alteration of medium to a low temperature that is genetically related to fluorite-polymetallic mineralization.

ORE-BEARING OF THE LIVOBEREZHNY ZIRCON-RUTILE-ILMENITE PLACER DISTRICT

The relevance of the presented publication is due to the need to highlight the current state of zirconium-titanium specialization objects, the need to modernize and unify geological information, due to the significant increase in the world community’s interest in minerals that belong to the group of critical raw materials. The article presents generalized data on the ore-bearing zircon-rutile-ilmenite deposits of the Livoberezhniy placer district of the Ukrainian placer province. This area has unique paragenetic characteristics, as it is located in the junction zone of three geostructural units: the Dnipro-Donetsk depression, the northeastern slope of the Ukrainian crystalline shield, and the Kalmius-Toretsk depression of Donbas. The Livoberezhniy placer district includes the Vovchansk, Voskresenivsk, Southern, Nova-Mykolaivka, North-Samarsk, Yuriivsk and Petropavlivsk zircon-rutile-ilmenite deposits. These deposits are located in the sediments of the Bereka and Novi Petrivtsi suites. The Petropavlivsk and Yuriivsk deposits have a two-layer structure, the rest is belongs to the deposits of the only Novi Petrivtsi suite. The genesis of deposits is buried coastal-marine placers. All deposits have a slight dip of the ore sand layers in a north-east direction, which outlines the general slope of the water basin floor. Today, the Vovchansk zircon-ilmenite-rutile deposit is being developed by DEMURINSKY GZK LLC. On the basis of the results of geological prospecting and geological exploration conducted in the 60s and 70s of the last century, maps of the strength of the ore stratum and the distribution of ore components (ilmenite, rutile, zircon) were constructed. The visualization data was built for the Voskresenivsk, Southern, Nova-Mykolaivka, North-Samarsk, Yuriivsk and Petropavlivsk deposits. An analysis of the obtained data was carried out and a number of conclusions were drawn regarding the distribution of ore components for each of the deposits.

Selective Neodymium Enrichment of Sulfides as a “Fingerprint” of Late Processes of Ore-Formation: Insight into Sm-Nd Isotopes for Sulfides from Magmatic Cu-Ni-PGE Complexes and Hydrothermal Pb-Zn, Au-Mo, and Gold Deposits

The effect of enrichment with Nd in sulfides from magmatic Cu-Ni-PGE complexes and sulfide ores from hydrothermal Pb-Zn, Au-Mo, and gold deposits was found and characterized. This paper concerns the report and analysis of isotopic geochemical data on the sulfide ores from the large Paleoproterozoic mafic–ultramafic magmatic Cu-Ni-PGE complexes of Fennoscandia and the literature data on sulfide ores from the Qingchengzi Pb-Zn deposit (northeastern China), Tokuzbay gold deposit (southern Altai, northwestern China), and Dahu Au-Mo deposit (central China). The mineral/rock partition coefficients for Nd and Sm (the DNd/DSm ratio) are defined as a prospective tool for the reconstruction of the sulfide mineral formation and geochemical substantiation of possible sources of ore-forming fluids for deposits of various genetic types. The observed selective Nd accumulation indicates either hydrothermal or metamorphic (metasomatic) impact, which is associated with increased Nd mobility and its migration or diffusion. Due to this process, there is a relative Nd accumulation in comparison with Sm and a consequent increase in the DNd/DSm ratio. At the isotopic system level, this leads to a sufficient decrease in the Sm/Nd ratio for the secondary sulfides of such kind. The revealed effect may serve as an isotopic geochemical marker of recent processes. These processes are quite frequently associated with the most important ore formation stages, which bear the commercially valuable concentrations of ore components. Sulfides from magmatic Cu-Ni-PGE complexes are more characterized by the selective accumulation of Nd in the sequential sulfide mineral formation. For sulfides from hydrothermal deposits, the effect of Nd enrichment is more intense and closely related to ore-forming fluids, under the influence of which sulfide mineralization is formed in multiple stages. The study aims at expanding the knowledge about fractionation and the behavior of lanthanides in ore-forming processes and allows the development of additional criteria for the evaluation of the ore potential of deposits with different geneses, ages, and formation conditions.

Sulfur isotope, fluid inclusions, and quartz solubility model decipher multistage hydrothermal fluids evolution and ore precipitation mechanism at the Nantai porphyry Mo deposit, Qinling, Central China

Qinling orogenic belt hosts many porphyry Mo deposits, which were formed by ore-forming fluids exsolved from oxidized magmas. Detailed processes of ore fluids evolution and metal deposition mechanisms of porphyry Mo deposits remain unclear. The quartz solubility model and cathodoluminescence (CL) images combined with fluid inclusions (FIs) and isotope analyses at the Nantai Mo deposit provide new insights into processes and physicochemical conditions for Mo mineralization. Based on field and microscopy of ore and alteration assemblages together with CL images, four types of hydrothermal veins (i.e., A, B, C, and D veins) have been identified. The quartz in A veins intergrown with K-feldspar precipitated from high-temperature and low- to intermediate-salinity fluids under near-lithostatically conditions. B vein comprises quartz and K-feldspar and forms at 336–466 °C, pH from 6.30 to 11.02, and oxygen fugacity (fO2) of −30.81 to −24.26. Hydrothermal fluids during this stage underwent phase separation under ductile to brittle transition. C veins include muscovite and most molybdenite without quartz, indicating that they formed in the retrograde quartz solubility field at 353 to 398 °C. Thermodynamic calculation suggests molybdenite mainly precipitated under fO2 from −32.37 to −29.05 and pH from 2.68 to 6.54. Quartz in D veins formed from low-temperature and low-salinity fluids. Sulfur isotopic analyses suggest that the ore components are derived from the old crust. The main factors controlling Mo mineralization at Nantai are the decreases in fO2 and pH values of hydrothermal fluids.

Processes of hydrothermal vein lead-zinc ore formation: geochemical data and thermodynamic models

For the Dzhimidonsky vein polymetallic deposit (North Ossetia, Russia), formed in the Middle Jurassic time, it was established by the nature of the distribution of rare-earth elements in the veins and rocks that the sources of REE and ore components were a combination of host rocks of different composition (PR3–PZ1, PZ3) and were replaced in time. Geochemical data served as the basis for the development of new methods of equilibrium-dynamic modeling and assessment of the influence of the change in time and space of fluid flows from different sources on the processes of ore formation.