Mineral Composition Of Ores Research Articles

Geology and He-Ar-S-Pb isotope constraints on the genesis of the Sidaogou gold deposit in Liaodong Peninsula, northeastern North China Craton

The large Sidaogou gold deposit in the Liaodong Peninsula is a typical alteration-type gold system, hosted in Paleoproterozoic metamorphic rocks of Gaixian Formation. Ore paragenesis indicates Sidaogou mineralization occurred in four stages: (1) early ore stage S1 (quartz + albite), (2) main ore stage S2 (quartz + sericite + pyrite + gold), (3) secondary ore stage S3 (quartz + polymetallic sulfide ± scheelite ± biotite ± gold), and (4) late ore stage S4 (calcite + ankerite ± quartz ± sulfide). Associated hydrothermal alterations in wall rocks are dominated by albitization (S1), silicification (S1 to S4), sericitization (S2), sulfidation (S2 to S3), and carbonatization (S4), with minor biotitization (S3) developed locally. Gold mineralization was primarily occurred in S2 stage with intensive silicification, sericitization, and sulfidation in metamorphic wall rocks, and occurred to a lesser extent in S3 stage with weak alteration possibly due to fairly weak activity and small fluxes of the ore fluids.At gold precipitation stages (S2 to S3), three generations of ore-related pyrite (Py1, Py2, and Py3) are identified. NanoSIMS in situ S isotope analyses show that both Py1 and Py2 from the S2 stage have relatively broad ranges of δ34S values with significant intra-grain variations (Py1 = 7.7–16.5‰; Py2 = 3.7–14.8‰), varying between those of wall rocks (11.6–20.3‰) and typical magmatic sources, as well as the regional contemporary magmatic-hydrothermal gold system (CMHGS). This can be interpreted by a mixed process formed by magmatic-hydrothermal fluids leaching different proportion of sulfur from wall rocks during extensive fluid-rock interaction. Py3 in the S3 stage has relatively narrow range of δ34S values (Py3 = 0.6–3.7‰) similar to those of adjacent CMHGS, indicating a magmatic origin without notable wall-rock contamination due to weak fluid-rock interaction. The S2 stage gold-bearing pyrite (Py1-dominated) shows 206Pb/204Pb ratios from 17.882 to 18.938, 207Pb/204Pb ratios from 15.592 to 15.825, and 208Pb/204Pb ratios from 37.811 to 39.003, which are between those of nearby Early Cretaceous Sanguliu granitic pluton and wall rocks ((206Pb/204Pb)i = 17.958–20.085, (207Pb/204Pb)i = 15.664–15.976, and (208Pb/204Pb)i = 37.474–40.021), implying that the lead was originated from mixture sources.Ore fluids from the S2 stage pyrite (Py1-dominated) have 3He/4He ratios range from 0.21 ± 0.01 to 0.57 ± 0.03 Ra (average 0.34 Ra), indicating a crustal source with minor mantle contributions. Moreover, the 3He/4He ratios are similar to those of the adjacent CMHGS, demonstrating a similar magmatic origin for the ore fluids. The 40Ar/36Ar ratios range from 547 to 11994, indicating that the ore fluids contained 48 to 98% crust-derived radiogenic 40Ar* which most likely inherited from wall rocks. Combining the geologic evidences and isotopic results, we propose that the Sidaogou deposit was formed by magmatic-hydrothermal fluids exsolved from Sanguliu pluton or its deep magma. During fluid-rock interaction, sulfur, lead, and 40Ar* were partly scavenged from the wall rocks and then sequestered by ore-related pyrite. Nevertheless, gold was mainly of magmatic origin. Our study reinforces the previous conclusion that S-Pb isotope compositions of ore-minerals could be strongly modified by wall rocks during fluid-rock interaction.

Paragenesis and composition of xenotime-(Y) and florencite-(Ce) from unconformity-related heavy rare earth element mineralization of northern Western Australia

This study investigates the paragenesis and ore mineral composition of xenotime [(Y,HREE)PO4] and florencite [LREEAl3(PO4)2(OH)6] from heavy rare earth element (HREE) deposits/prospects of the Tanami and Hall Creek regions of Western Australia. Two stages of xenotime-(Y) formation are recognized: (1) early xenotime-(Y) in breccias (breccia-hosted) and in quartz-xenotime-(Y) veins (vein-type); and (2) late xenotime-(Y) that occurs largely as dipyramidal-shaped overgrowths on the pre-existing early xenotime-(Y). Similarly, florencite-(Ce) formed in two stages including: (1) early florencite-(Ce) that coexists with and is enclosed by early xenotime-(Y) within mineralized veins; and (2) late florencite-(Ce) that replaces early xenotime-(Y), or appears as narrow rims on early florencite-(Ce). All xenotime-(Y) types from a number of examined HREE deposits/prospects are characterized by elevated U contents and marked negative Eu anomalies that we interpret to be inherited from the metasedimentary rocks from which REE and P required for the phosphate ore mineralization, were sourced. Compared to the early xenotime-(Y), the late xenotime-(Y) is richer in HREE and depleted in P, owing to the formation of the coexisting late florencite-(Ce). Moreover, early florencite-(Ce) has a near end-member florencite (s.s.) composition similar to those associated with unconformity-related U deposits, whereas late florencite-(Ce) sits on the florencite-svanbergite compositional spectrum. The high U content of xenotime-(Y) and composition of early florencite-(Ce) potentially support a genetic association between the HREE mineralization and the coeval unconformity-related U deposits of northern Australia. Nevertheless, we also urge for caution in using xenotime-(Y) composition in isolation as an indicator of geological setting.

Ognitite, NiBiTe, a new mineral species, and Co-rich maucherite from the Ognit ultramafic complex, Eastern Sayans, Russia

AbstractWe describe the new species ognitite, NiBiTe, and a Co-rich variety of maucherite, hitherto unreported; both were discovered in the Ognit ultramafic complex of Neoproterozoic age in Eastern Sayans, Russia. The mean composition of ognitite (n = 7) is: Ni 17.05, Fe 0.07, Cu 0.14, Pd 0.14, Te 32.53, Bi 49.64, total 99.57 wt.%, corresponding to: (Ni1.11Cu0.008Fe0.005Pd0.005)Σ1.13Bi0.90Te0.97 (Σ atoms = 3 apfu). Ognitite is trigonal, space group P3m1 [R1 = 0.0276 for 81 reflections with Fo > 4σ(Fo)]. The unit-cell parameters derived from the single-crystal X-ray diffraction data are: a = 3.928(1) Å, c = 5.385(1) Å and V = 71.95(4) Å3, with Z = 1. The c:a ratio is 1.37. The powder X-ray diffraction data obtained on the same fragment used for the single-crystal study are: a = 3.9332(4) Å, c = 5.3920(6) Å and V = 72.24(1) Å3. Ognitite exhibits the brucite-type structure with edge-sharing NiTe3Bi3 octahedra forming sheets parallel to (0001). It is related to melonite, but is distinct compositionally by the extreme Bi-enrichment (melonite and its synthetic analogue contain <0.4 Bi apfu), and structurally as Bi and Te are ordered at two distinct sites, leading to the loss of the centre of symmetry in ognitite.At more than 9 wt.% Co, or ~2 apfu Co, the core of Co-rich maucherite [(Ni,Co)11As8] in a zoned crystal, which is surrounded by Co-depleted orcelite, far surpasses the norm (≤1 and up to 3.9 wt.% Co). The unit-cell parameters of the Co-rich maucherite are: a = 6.85(2) and c = 21.83(5) Å, which are based on results of synchrotron micro-Laue diffraction.The host rock consists of serpentine, clinochlore (Mg# 95–97) and skeletal chromite. We favour the metastable crystallisation of fluid-saturated globules of a sulfide–arsenide melt to explain the anomalous compositions of ore minerals at Ognit. These anomalies seem consistent with rapid cooling in a fluid-enriched system, possibly related to late-stage degassing of the magma, as reflected in a prominent metasomatic aureole at the contact with the enclosing gneissic rocks.

Identyfikacja domieszek V, Co, Ni i Au w minerałach kruszcowych rud Fe-Ti-V (NE Polska) na podstawie analiz mikrosondą rentgenowską (EMPA)

Electron microprobe study of V, Co, Ni and Au admixtures in ore minerals from Fe-Ti-V deposits (NE Poland). A b s t r a c t. The main objective of this study was to quantitatively and qualitatively idenify trace metal admixtures in ore minerals from Fe-Ti-V ore deposits within the Suwa³ki Anorthosite Massif in NE Poland. Chemical composition of ore minerals was determined using the CAMECA SX-100 electron microprobe and scanning electron microscope. The most abundant trace elements were Ti and V hosted in oxides and Co, Ni, Cu, Zn contained in sulphides such as pentlandite, pyrrhotite, chalcopyrite, pyrite, siegenite, millerite. Scarce occurrences of native Bi, hessite and greenockite were identified. Samples, which were depleted in iron oxides were enriched in REE due to the presence of zircon, apatite and monazite.

Genesis of the Huangshaping W–Mo–Cu–Pb–Zn deposit, South China: Role of magmatic water, metasomatized fluids, and basinal brines during intra‐continental extension

The Huangshaping world‐class W–Mo–Cu–Pb–Zn deposit formed during Jurassic intra‐continental extension in the central Nanling region (South Hunan), South China. In order to assess the role of fluids in ore genesis and the origin of polymetallic mineralization, three types of mineralized porphyries (quartz porphyry, granophyre, and granite porphyry) were studied. The multi‐method approach included whole‐rock Sr–Nd isotopic geochemistry and determination of the trace element content and gaseous and aqueous composition of ore minerals from the three stages of intrusion and ore emplacement. Geochemical results show that the Sr–Nd isotopes in these altered porphyries were strongly affected by fluid metasomatism. The 87Sr/86Sr and 147Sm/144Nd ratios for the quartz porphyry and granophyre range from 0.72894 to 0.83093 and 0.1524 to 0.2080, respectively, whereas higher and considerably more variable ratios were determined for the granite porphyry (0.90396 to 1.51943 and 0.2391 to 0.2914). These observations imply that granite porphyry‐associated W–Mo mineralization underwent more intensive fluid–rock interaction. The relatively low REE concentrations and high abundances of CH4 and H2 in the Cu ores associated with the quartz porphyry unambiguously suggest a deep‐sourced magmatic fluid for the Cu mineralization. The high REE concentrations, pronounced negative Eu anomalies, M‐type tetrad effects, and high CO2, H2O, and Ca2+ contents of the W–Mo ores associated with the granite porphyry imply that the W–Mo polymetallic mineralization was formed in a relatively oxidizing, high‐temperature environment with strong metasomatism. In contrast, the slightly negative Eu anomalies, W‐type tetrad effects, low CH4, and high F− and Cl− concentrations of the Pb–Zn ores indicate involvement of a sediment‐derived basinal brine and reducing mineralization conditions. Collectively, a three‐stage genetic model is proposed for the Huangshaping polymetallic deposit. Corresponding to initiation, development, and cessation of Jurassic intra‐continental extension, magmatic water, metasomatized fluids, and basinal brines played key sequential roles in Cu, W–Mo, and Pb–Zn mineralization.

GEOLOGY AND PALEOVOLCANIC CONDITIONS OF FORMATION OF LETNEE DEPOSIT (SOUTHERN URALS)

The article considers the geological structure and paleovolcanic conditions for the formation of the Letnee pyrite-polymetallic deposit, located within the Dzhailgansky ore field. It is shown that there are three strata in the structure of the ore-bearing volcanogenic complex, the first (lower) of which is composed mainly of large-scale pillow basalts and associated dolerites, the second - small-scale pillow basalts and hyaloclastites, and the third (ore-bearing) - plagiophyric small-scale pillow basalts, doler- ites, basaltic breccias. Analysis of the thicknesses and facies of the volcanogenic complex have allowed to reconstruct various palevolcanic elements within the ore field, including the Dzailgansky shield volcano, the Chiliktinsko-Kiembaisky and Nurundinovsky volcanic-tectonic uplifts, the Kiembaisky volcanic- tectonic depression, and the Chiliktinsky caldera depression. It has been established that within the considered area the location of the ore-bearing volcanic complex is completely determined by the boundaries of the Chiliktinsky caldera. Ore bodies inherit the unevenness of the paleorelief of its bottom, have a lenticular or stratiform shape and usually locate in accordance with the layering of basalts. The ore field is repre- sented by 8 pyrite-polymetallic ore bodies of lenticular form, composed mainly of massive ores, which include pyrite, chalcopyrite, sphalerite and magnetite. Specificity of the mineral composition of ores is the high con- tent of cobalt in them and a significant amount of iron oxide mineraliza- tion, which forms individual magnetite lenses or stratabounds at the base of copper-pyrite ore bodies. Taking into account the above listed features, the genesis of the Letnee deposit should be considered as volcanogenic-sedimentary and attributed to a copper-pyrite formation close to the cyprian (dombarovsky type).

Geological-Structural Position and Formation Conditions of Gold-Containing Porphyry Copper Deposits of Mekhmanian Ore-Magmatic System (Lesser Caucasus, Azerbaijan)

This article focuses on geological-structural position and formation conditions of gold-containing deposits of Mekhmanian ore-magmatic system (OMS) according to tectonic position of deposits, material composition of ore-bearing and ore-hosting intrusive complexes, specifics of mineral composition, quantity and correlation of main and associated components. There is a new data allowing to estimate formation conditions and matter sources of OMS deposits. Productive mineralization has been determined which occurs by two stages: 1) quartz-molybdenite, quartz-chalcopyrite; 2) quartz-chalcosine-pyrite-chalcopyrite, sphalerite-galena-gold-rare-metal. At first stage concentrators of gold are pyrite and chalcopyrite, and its content is non-uniform, and at second stage gold-containing are represented by galena, sphalerite and also fahl ores and tellurides. We distinguish three gold-bearing associations according to mineral composition of ores, they are: quartz-molybdenite-chalcopyrite, quartz-pyrite-chalcopyrite and quartz-galena-sphalerite.

Physicochemical Conditions of Formation of Gold and Silver Parageneses at the Valunistoe Deposit (Chukchi Peninsula)

Abstract —The mineral composition of ores from the Gornyi occurrence of the Valunistoe epithermal Au–Ag deposit (Chukchi Peninsula) has been studied. It has been found that, in addition to native gold, the Au–Ag mineralization comprises chalcogenides (uytenbogaardtite, petrovskaite, acanthite, naumannite, and cervelleite) and minerals of the pearceite–polybasite series, which occur as microinclusions in fine-grained pyrite. The physicochemical conditions of formation of productive mineral assemblages have been estimated based on the chemical composition of Au and Ag minerals and their relationships with other minerals. It is shown that ores were deposited from weakly acid solutions at the late stages, on the background of a temperature decrease from 350 to 100 °C, a decrease in the fugacities of sulfur (logfS2, from −2 to −23), tellurium (logfTe2, from –5 to –27), and selenium (logfSe2, from −16.5 to −28), and changes in the redox conditions (logfO2, from −23 to −48).

Cu and S isotopic signatures of the Erdenetiin Ovoo porphyry Cu-Mo deposit, northern Mongolia: Implications for their origin and mineral exploration

The copper (δ65Cu) and sulfur (δ34S) isotope compositions of ore minerals from the Erdenetiin Ovoo porphyry Cu-Mo deposit in northern Mongolia were measured. The δ65Cu values of Cu (I) sulfide minerals ranged from 0.14‰ to 2.69‰, suggesting that Cu predominantly originated from magmatic sources, whereas Cu (II) minerals such as chrysocolla, malachite and azurite presented much larger variations of δ65Cu values from −1.01‰ to 10.0‰. The small difference between the primary and secondary Cu sulfide minerals indicates an insignificant influence of Cu isotope fractionation processes during their formation, which may be explained by large mass transport and/or the involvement of biogenic activities. The δ65Cu values of primary chalcopyrite suggest source heterogeneity and/or the occurrence of isotope fractionation under a high-temperature environment. The positive ΔCu (II) mineral − Cu (I) mineral values imply little transport of Cu in the deposit, with a rough mass balance and fast redox reaction.The δ34S values of the primary sulfide minerals (pyrite, molybdenite and chalcopyrite) clustered near 0‰, indicating that the sulfur is mainly derived from a homogeneous magmatic source. By contrast, the δ34S values of secondary Cu sulfide minerals ranged from −3.2‰ to −0.3‰, with an average of −1.6‰. The lower δ34S values are likely influenced by either S isotope fractionation processes or input of sulfur with different S isotope compositions during their formation.The measured δ65Cu and δ34S values of these ore minerals suggest a large mass transportation of Cu to an adjacent location, indicating little possibility of a hidden Cu occurrence in the Erdenetiin Ovoo deposit area.

Practical aspects of estimating the quantitative mineral composition of copper-bearing sedimentary rocks on the basis a calculation procedure analogical to the CIPW norm

The paper presents a possibility of estimating the content of ore minerals based on chemical analyses of copper-bearing sedimentary rock samples from the North-Sudetic Synclinorium and from the Fore-Sudetic Monocline using a calculation procedure similar to the CIPW norm. The mineralogical data was obtained by means of an optical microscope and an electron microprobe (EPMA). The quantitative composition of gangue minerals was determined using the XRD method, and of the ores by the computer microscopic image analysis (CAMI). The actual set of gangue and ore minerals, their chemical composition, and proportions of copper ores were determined in the samples. Elements that are the main components of identified minerals were selected. The calculation procedure has been developed in accordance with the mineralogical and chemical data. The set of ore minerals determined based on the calculation of the weight ratios is consistent with the microscopic observations of copper-bearing rocks. The obtained ore contents are similar or slightly higher in poorly mineralized samples and slightly lower in highly mineralized samples in comparison to the results of the CAMI method. These differences may be due to different methods of averaging samples (powdered, averaged rock samples, and a thin section). The calculated ore proportions are consistent with those obtained by the CAMI method. The study calculations of the quantitative ore mineral composition using the calculation procedure analogical to the CIPW norm can be used to a preliminary approximation of the quantity of ores in geological prospection and exploration studies, but they require testing of more variants of the element partition between the set of minerals.

Dvoinoe Au–Ag Epithermal Deposit, Chukchi Peninsula, Russia

The Dvoinoe Au-Ag low-sulfide epithermal deposit is located in the Ilirnei ore district (western Chukotka) within the outer zone of the Okhotsk–Chukotka volcanic belt (OChVB). The paper considers the results of geological–structural, mineralogical–geochemical, and thermobarogeochemical studies of the deposit. The ores of the deposit are characterized by dominant colloform-banded (often combined with brecciated) structures; a high Au/Ag ratio (1: 1 to 1: 2); low sulfidity (<0.5%); the presence of hessite, small sulfide segregations (0.005–0.015 mm), and a larger amount of native gold (0.01–0.07 mm); high Au, Ag, and Sb contents; relatively high As, Cu, Pb, and Cd contents; higher Zn, Bi, and Te contents; a low total REE; and negative Eu and positive Ce anomalies. The geochemical features are consistent with the ore mineral composition. The high Rb/Sr, Th/La, Y/Ho, and U/Th ratios of ores are most likely caused by the position of the deposit in the zone of influence of the Ilirnei granitic pluton. A fluid inclusion study showed that the ores were formed from Na–K–Mg low-saline (5.58–0.2 wt % NaCl-equiv.) hydrothermal fluids with a small amount of CO2, H2S, and CH4 with decreasing temperatures from 370 to 130°C and the following fluid parameters: CO2/CH4 = 217–53, Na/K = 5–2, and K/Rb = 2722–202. The results are compared with original and published data on the Kupol, Moroshka, and Sentyabr’sky deposits. Our data are important for regional forecasting, interpreting metallogeny, and the search for and evaluation of Au–Ag epithermal deposits.

Intrusion-related gold-bismuth deposits of North-East Russia: PTX parameters and sources of hydrothermal fluids

Intrusion-related Au-Bi deposits of North-East Russia are related to Late Mesozoic orogenic S- and I-type granites of ilmenite series. The studied deposits differ in their position relatively to the plutons, alteration, ore body morphology and sulphide content in ores. Based on mineral composition of ores, studied deposits are divided into bismuth-sulphotelluride-quartz, bismuth-arsenide-sulpharsenide and bismuth-siderite-polysulphide types. Bismuth-sulphotelluride-quartz deposits (Levo-Dybinskoe, Kurum, Ergelyakh, Tuguchak, Basugunya) are characterised by low-sulphide (≤3 vol%) mineralisation. Native gold associates with bismuth minerals (bismuthinite, sulphotellurides and tellurides, maldonite, jonassonite, native bismuth). Bismuth-arsenide-sulpharsenide deposits (Myakit, Chepak, Dubach, Chistoe, Kandidatskoe) host As-rich mineralisation. Löllingite and arsenopyrite are main minerals, and their contents vary from 5 to 60 vol% (commonly ∼10%). The intergrowths of native gold with bismuth minerals (sulphotellurides, tellurides, native bismuth) occur mainly in arsenopyrite. Bismuth-siderite-polysulphide (Arkachan) type is characterised by high-sulphide (5–15 vol%) and high-carbonate (up to 35 vol%) ores. Native gold associates with bismuthinite and other sulphobismuthites. Minerals of tellurium are rare. Fluid inclusion and stable isotope study of samples from eighteen Au-Bi deposits constrains the fluid composition, formation temperatures, pressures, and fluid sources. Four types of fluid inclusions (FI) were revealed: (I) two-phase FI, consisting of H2O liquid and CO2 vapour, and three-phase FI with H2O liquid, CO2 vapour and CO2 liquid; (II) vapour-rich CO2 one- or two-phase FI with minor (rarely dominant) CH4 and N2, sometimes with a thin liquid rim; (III) two-phase liquid-vapour aqueous inclusions; (IV) three- or multiphase FI, consisting of H2O liquid, gas bubble and one or more daughter minerals. Au-Bi mineralisation formed at 437–200 °C (mainly from 400 to 250 °C) and 0.1–1.9 kbar from a H2O-CO2-NaCl fluid, which forms an immiscible brine and CO2-bearing vapour at low pressure (≤1.3 kbar) as well as low- to moderate salinity CO2-H2O mixtures without brines at higher pressure (≥1.3 kbar). The studied deposits formed at shallow (Ergelyakh, Tuguchak, Arbatskoe at 1–2 km, Kurum, Levo-Dybinskoe at 2–3 km) and deep (Chuguluk, Shkolnoe, Arkachan at ∼4 km, Dubach at >5 km) depth. Bismuth-sulphotelluride-quartz deposits commonly occur at shallow depth, whereas bismuth-arsenide-sulpharsenide and bismuth-siderite-polysulphide deposits are mainly formed in deeper environment. The stable isotope data suggest predominantly magmatic source of gold-bearing fluids, but magmatic fluid was enriched in light O, C and S isotopes as a result of fluid immiscibility. The magmatic source is consistent with the overlap in lead isotope compositions of ores and related intrusions, as well as synchronism of magmatism and hydrothermal activity according to geochronology data.

GEOLOGY AND PALEOVОLKANIC CONDITIONS FOR FORMATION OF BARSUCHIY LOG DEPOSIT (SOUTHERN URALS)

The article reviews the geological structure and paleovolcanic conditions for the forma-tion of the pyrite-polymetallic deposit Barsuchiy Log, located within the Dzhusinsky ore district. It is shown that four strata participate in the structure of the ore-bearing volca-nogenic complex, the first and third of which are composed mainly of basaltic porphy-rites and their tuffs, and the second and the fourth are effusive and pyroclastic rocks of the dacite and rhyodacite composition. Analysis of the thicknesses and facies of these volcanic complex layers made it possible to reconstruct various palevolcanic elements within the ore field, including: the Karabutak uplift, which is a linear anticlinal structure such as a volcanic ridge; stratovolcano, which is the main element of accumulative structure; a number of paleovolcanic structures of the central type located on the slopes and at the foot of the stratovolcano. It is established that within the area the location of the ore -bearing volcanic complex is completely determined by the boundaries of the Karabutak uplift, the position of the ore field is controlled by the stratovolcano, and its throat determines the structural distribu-tion of the ore bodies of the Barsuchiy Log deposit. The deposit is represented by three stratified ore bodies of lenticular shape, composed mainly of massive ores, which include pyrite, chalcopyrite, sphalerite and galena. Specificity of the mineral composition of ores consists of an increased amount of pale ore in them, a high content of galena and barite. Taking into account the above-listed features, the Barsuchiy Log deposit can be com-pared with the barite-polymetallic objects of the Baimaksky area and referred to the Caucasian type.

The Shah-Ali-Beiglou Zn-Pb-Cu (-Ag) Deposit, Iran: An Example of Intermediate Sulfidation Epithermal Type Mineralization

The Shah-Ali-Beiglou epithermal base metal-silver deposit is located in the Tarom-Hashjin metallogenic province (THMP) in northwestern Iran. This deposit is hosted by quartz monzonite dikes of Oligocene age and surrounded by andesite to trachyandesite volcanic and volcaniclastic rocks of Eocene age. The subvolcanic rocks in the study area vary in composition from quartz-monzonite to monzonite and have metaluminous, calc-alkaline to shoshonitic affinity. These rocks have I-type geochemical characteristic and are related to post-collisional tectonic setting. The mineralization occurs as NE-SW and E-W-trending brecciated veins controlled by strike-slip and normal faults, which are associated to the Late Oligocene compressional regime. The mineral paragenesis of the vein mineralization is subdivided into pre-ore stage, ore stage, post-ore stage, and supergene stage. Pre-ore stage is dominated by quartz, sericite, and subhedral to anhedral pyrite as disseminated form. Ore-stage is represented by quartz, sphalerite (from 0.1 mol % to 4 mol % FeS), galena, chalcopyrite, tetrahedrite-tennantite, minor seligmannite and enargite, as vein-veinlet, cement and clast breccias. Post-ore stage is defined by deposition of quartz and carbonate along with minor barite, and supergene stage is characterized by bornite, chalcocite, covellite, hematite, goethite, and jarosite. The ore mineralization is associated with the silicic alteration. The styles of alteration are silicic, carbonate, sericitic, chloritic, and propylitic. Fluid inclusions in sphalerite have a wide range of salinities between 0.35 wt % and 21.4 wt % NaCl equivalent and homogenization temperatures range from 123 to 320 °C. The isotopic values of sulfides vary from 2.8‰ to 6.7‰ suggesting a magmatic source for the sulfur. In the present study, based on geological setting, alteration style of the host and wall rocks, main textures, mineral assemblages, composition of ore minerals, and structural features, it is suggested that the mineralization in the Shah-Ali-Beiglou is similar to intermediate-sulfidation style of epithermal deposits.

イラン・ザンジャン州の磁鉄鉱-燐灰石鉱床の鉱石および母岩の化学組成とSr-Nd-Fe同位体組成

イラン・ザンジャン州の磁鉄鉱-燐灰石鉱床の鉱石および母岩の化学組成とSr-Nd-Fe同位体組成

Sedimentary exhalative origin for magnetite deposits of the New Jersey Highlands

The New Jersey Highlands and contiguous Hudson (New York) Highlands host hundreds of small, worked-out magnetite mines, and the major zinc-oxide deposits of Franklin and Sterling Hill. The origin of the magnetite ore remains controversial. Two temporally distinct genetic models have been proposed for magnetite: (1) a pre-Ottawan, sedimentary exhalative model in which ores were deposited on the seafloor as precipitates from iron-enriched hydrothermal fluids; (2) a late-Ottawan, fluid alteration model in which the current mineral composition of ores was derived from Fe-rich, alkaline fluids, associated with late episodes of granitic plutonism (low-Ti Kiruna-type deposits), or in which deposits derived from metamorphogenic fluids circulating in a regional shear zone leached metals from host rocks and precipitated them in veins and faults. Detailed mapping of ore deposits and host rocks near Wanaque and Ringwood, New Jersey, and Warwick, New York, reveal that ore bodies are hosted by supracrustal rocks deposited in a back-arc basin. At Wanaque and Warwick, ores are strataform and stratabound. Discordant ore bodies at Ringwood are associated with a feeder zone, presumed to have intersected the paleosurface at a steep angle. Sharply layered quartz–diopside gneiss is spatially associated with ore at Wanaque and Warwick, and massive diopsidite is spatially associated with ore at all three locations. Diopsidite in these rocks is nonaluminous, iron enriched, and shares these characteristics with modern metalliferous sediments. Massive diopsidite and quartz–diopside gneiss are interpreted to be metamorphosed carbonate facies iron formation, and associated magnetite to be metamorphosed oxide-facies iron formation.

MANAGEMENT OF PROCESSES FOR ENRICHMENT OF COPPERMOLYBDENUM ORES USING QUALITY CONTROL QUALITY

In the process of ore beneficiation, applying open control loop systems using ore quality as input parameter, proves very effective. To determine the ore quality, on-line analysis of its material and mineralogical composition, impregnation of valuable components is carried out. Based on the analysis results, ore streams are formed at the processing plant, and effective processing conditions are selected. Modern systems of visual metering analysis of ore create the basis for efficient automated control of beneficiation processes, based on the principle of advanced control of ore grade. To improve the accuracy of determining the ore mineral composition, a special installation has been developed, which provides cleaning of ore from slurry. The installation enables achieving high accuracy of the ore mineralogical composition analysis. Tests of the ore grade visual metering analysis system, carried out using copper-molybdenum ores of the Erdenet GOK, have shown high reliability and efficiency of the system.

Tectono-metallogenic settings of the formation and convergence of disseminated Au–sulfide mineralization

Large Au-sulfide deposits (GSDs) of disseminated ores occur worldwide in metallogenic provinces of various ages (from Precambrian to Pliocene). The studies performed showed that the great genetic diversity of GSD is determined by the similar oregenesis conditions that appear in different tectono-metallogenic settings (TMSs). A GSD is included in a certain TMS by the respective changes in the mineral and geochemical assemblages of ores. However, in the majority of cases, the GSDs of different TMSs are convergent (quasi-identical) in the texture, structure, and mineral composition of ores. All types of the above TMSs are found in Russia, which allows forecasting the discovery of new GSDs in each setting.

Behavior of Zn2+, Cd2+, Ba2+ and Pb2+ cations in ferromanganese crusts from the Marcus Wake seamount (Pacific Ocean) in aqueous solutions of metal salts

The behavior of heavy-metal cations in ore minerals of cobalt-rich ferromanganese crusts from the Marcus Wake seamount in aqueous solutions of metal salts was studied in experiments. The Zn2+ and Cd2+ cations showed high reactivity and Ва2+ and Pb2+ showed low reactivity. It was found that Zn2+ and Cd2+ cations within the ore mineral composition are mainly absorbed (up to 66%) whereas Pb2+ and Ва2+ are chemically bound (up to 70%). Ore minerals in the crusts are characterized by sorption properties and high ionexchange capacity by these cations (1.94–2.62 mg-equiv/g). The capacity values by heavy-metal cations for ore minerals of the crusts from different areas of the Marcus Wake seamount are close to each other.

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

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