Massive Sulfide Ore Research Articles

Formation of the Lianhuashan Cu deposit in the southern Great Xing’an Range, NE China: Constraints from fluid inclusions, whole-rock geochemistry, zircon U–Pb geochronology, and H–O–S–Pb isotopes

The medium-sized Lianhuashan Cu sulfide deposit is located in the southern Xing’an Range of Inner Mongolia, NE China. The zoned massive sulfide vein ores are hosted mainly in the Permian Dashizhai Formation, and the ore veins are controlled by NW–NNW-trending structures. The ore-forming process comprises four stages: arsenopyrite–quartz (I); chalcopyrite–pyrite–quartz (II); pyrite–chalcopyrite–sphalerite–galena–quartz (III); and ore-barren sulfide–quartz–carbonate (IV). Three types of fluid inclusions (FIs), namely vapor-rich two-phase (LV-type), liquid-rich two-phase (VL-type), and daughter mineral-bearing three-phase (SL-type), are distinguished. Stage I, II and III contain all types of FIs (LV-, VL-, and SL-type), with homogenization temperatures (Th) of 268–462°C, 230–382°C and 180–340°C and salinities of 3.4–52.3, 3.4–44.5 and 3.7–39.9 wt% NaCl eqv., respectively, whereas stage IV has only VL-type FIs, with Th = 152–232°C and salinity = 3.4–7.9 wt%. Fluid geochemical data show that the Lianhuashan ore fluids were of medium–high temperature (236–382 °C), high-salinity (31.5–44.5 wt%), and relatively oxidizing conditions, typical of a NaCl-H2O system. The microthermometric and H–O isotope data (δ18OH2O = − 9.0 to 6.1 ‰; δD = − 149.0 to − 99.0 ‰) indicate that the ore fluids were initially magmatic with later meteoric water incursion. The sulfide S (δ34S = − 2.9–3.8 ‰) and Pb (206Pb/204Pb = 17.954 − 18.492, 207Pb/204Pb = 15.427 − 15.739, 208Pb/ 204Pb = 37.815 − 38.357) isotopes support that the metals were magmatic-derived. Fluid boiling, cooling, and meteoric water mixing were likely the main ore precipitation mechanism at Lianhuashan.We suggest that Cu minerals at Lianhuashan were precipitated with boiling at ∼ 1km depth. For the ore-forming granodiorite porphyry (zircon U-Pb age: 252.8 ± 1.8 Ma), geochemical data indicate that the primary magma was formed by partial melting of the thickened or delaminated lower crust. Integrating the available age, geological, and geochemical evidence, we suggest that mineralization at Lianhuashan is spatial–temporal and genetically associated with the granodiorite porphyry, and was formed in a volcanic arc setting after the Paleo-Asian Ocean closure.

Mineralogy and sulfur isotopic compositions of sulfides from Yunzang (25.3°S) hydrothermal field, South Mid-Atlantic Ridge: Implications for formation mechanism and maturation of sulfide chimneys

A newly discovered hydrothermal field, named Yunzang and predominantly hosted by mafic rocks, was recently identified at 25.3°S on the South Mid-Atlantic Ridge (SMAR). This is the first report on the sulfide mineralogy and sulfur isotopic composition of sulfide chimney and massive sulfide ores collected from Yunzang field, SMAR. Based on mineralogical morphology, texture, crystallinity, assemblage and zonation, five specific stages of mineralization can be divided for the sulfide chimney at Yunzang. These stages range from low- to high-temperature hydrothermal conditions, along with an additional stage of seafloor weathering. The observed variations in morphology and crystallinity from low- and medium-temperature stages to high- and high- to medium-temperature stages suggest an evolution in the ore-forming conditions. Initially, the environment was characterized by instability and low-temperature conditions, with significant seawater influx. Subsequently, there was a shift towards a more stable regime dominated by high-temperature ore-forming fluid condition. The positive δ34S values of all the sulfides from Yunzang hydrothermal field suggest 79–92 % and 69–79 % of sulfur were generated from the leaching of basalt for sulfide chimney and massive sulfide, respectively, the rest sulfur were from reduced seawater sulfate. The δ34S values of massive sulfide (3.5–6.8 ‰, average = 5.1 ± 0.9 ‰) are mostly higher than that of sulfide chimney (1.1–4.5 ‰, average = 2.8 ± 0.8 ‰) are mainly caused by sub-surface reactions between preexisting sulfate and re-circulating fluid. An incremental increase of δ34S values from the external edge to the interior orifice indicating the Yunzang chimney maturation is relatively lower and the duration of hydrothermal activity was short. These results enrich our comprehension of mineralization in the seafloor hydrothermal system.

Atmosphere and biological impact during sulfide formation in the Archean Central-Vozhma sulfide deposit (Karelia)

Relevance. The need of new knowledge about the early stages of the Earth. Sulfur isotope analysis of sulfide minerals is a powerful tool to understand the processes during the Archaean and Paleoproterozoic. Combined with other data, isotope geochemistry provides an insight into sulfur sources of sulfides from ancient sulfide volcanosedimentary deposits; geochemical factors affecting Archaean sulfide volcanosedimentary ore formation; adjust genetic models and determine the degree of influence of bacteria on the mineral formation. Aim. To identify the sources of sulfur during the formation of sulfide deposits via isotope analysis, and to evaluate bacteria affect mineral formation. Objects. They were obtained from the core of boreholes of Mesoarchaean volcanosedimentary sulfide Central-Vozhma deposit, being a part of the Sumozersko-Kenozersky greenstone belt of the Karelian craton. Methods. Mineralogical studies of rock and ore samples were carried out using optical microscopy; scanning electron microscopy and energy dispersive X-ray spectroscopy. The ratios of four stable sulfur isotopes were analyzed in sulfide minerals of the deposit (33S/32S, 34S/32S, 36S/32S). Results. The results obtained demonstrated the polygenic source of sulfur in sulfides. The sulfides have both positive and negative Δ33S values, indicating the presence of atmospheric sulfur formed under UV photolysis during mineral formation. Sulfide minerals include the following components: Seawater sulfate sulfur of photolytic genesis showed a negative anomaly Δ33S (∼ –0.4‰). It was the source of authigenic pyrite. Sulfides crystallized as a result of biological sulfate reduction demonstrated a narrow range of δ34S values (–2.64‰˂0˂+4.27‰). Elemental sulfur of photolytic genesis mobilized from the host sedimentary rocks by hydrothermal fluids. This sulfur, with a positive Δ33S anomaly (up to +1.6‰) took part in the massive sulfide ores formation.

Extent and survival of zoned pyroxene within intrusions hosting magmatic sulfides: Implications for zoned pyroxene as a prospectivity indicator

AbstractChromium-zoning patterns in pyroxene from the economically significant Ni-Cu sulfide deposits at Nova-Bollinger (Western Australia) and Kevitsa (Northern Finland) were investigated using XRF mapping, automated mineralogy, and EPMA analyses. At Nova-Bollinger, complex Cr-zoning patterns are found widely throughout the cumulus orthopyroxene and clinopyroxene within the Lower Intrusion, a small chonolith that hosts the vast extent of the sulfide mineralisation. Cumulus pyroxenes with visible sector and abrupt zonation patterns have been found up to 150 m vertically away from the massive sulfide ore. Complex zoning patterns are observed throughout the Kevitsa intrusion, in the form of strong oscillatory zoning in cumulus clinopyroxene and sector zoning in idiomorphic orthopyroxene oikocrysts. Kevitsa pyroxenes show varying degrees of hydration, leading to epitaxial replacement by amphibole. Cr zonation is visible through the early stages of this alteration, with preservation enabled by the presence of Cr-rich epitaxial amphibole; however, the remnant zoning is lost as the amphibole alteration progresses. Results suggest that Cr zonation in pyroxene may be an effective indicator of dynamic recharged conduits and therefore an indicator of favourable conditions for metal enriched magmatic sulfide ore formation. Such indicators have significant vertical extent from the ore body and can survive partial alteration, which makes them a useful tool for prospectivity assessment of drilled intrusions. Furthermore, our data show that there is potential for complexly zoned pyroxene to be used as an ex-situ prospectivity indicator in glacial till.

Analytic continuation: A tool for aeromagnetic data interpretation

Extending potential-field data to vertical complex-plane slices provides opportunities, unique to analytic functions, for subsurface imaging. We begin with an existing numerical method for differentiation by integration using Cauchy's integral formula. An example from data over northern Ontario, Canada, illustrates better conditioning compared to derivatives computed using finite differences. Next, these quantities are used for analytic continuation using rational complex-series expansion (Padé approximation). This method provides stable downward continuation to distances that are significantly greater than are achievable by Taylor series and spectral methods. A synthetic test confirms that the rational approximant faithfully reproduces the magnetic response of a thin sheet. A sign reversal of the total field, coincident with the origin of the sheet, features prominently on this example. We also provide synthetic results for sheets with finite depth extent, point sources, thin slabs, and contacts. These also exhibit polarity flips near the source location. Further, these provide a template for interpreting the source geometry using the shape of the approximating function. Additional synthetic tests illustrate an automatic method for locating closely spaced random assemblages of isolated poles. We apply our methods to a deposit-scale heliborne survey over a recently discovered volcanogenic massive sulphide ore deposit in a Canadian greenstone belt. The analytically continued profile over the deposit suggests the presence of a subvertical thin sheet of unknown depth extent. This interpretation coincides with a sulphide ore body that has been previously delimited by several drill holes. Some known prospects near this deposit are also imaged on maps and profiles of the Padé approximant.

Variation of chalcophile elements in base metal sulfide minerals from the Jinchuan magmatic Ni–Cu sulfide deposit, NW China: Implications for mineral exploration

Magmatic sulfide ores from the western and eastern intrusions of the world's third-largest Jinchuan Ni–Cu deposit are separated into disseminated, net-textured, and massive sulfides, or Fe-rich, transitional, Cu-rich ores. However, the composition of base metal sulfide (BMS) minerals from each intrusion and ore type still lacks investigation. By comparing the variations of chalcophile element composition of BMS minerals from different intrusions, sulfide textures, and ore types, new discriminant diagrams are constructed for subsequent exploration. BMS minerals from the eastern intrusion host more slightly chalcophile elements (Zn As, Sn Cd) because of the higher degree of crustal contamination, and less strongly chalcophile elements (Co, Bi, Se, Re, Ag, Te) due to the lower amount of prior sulfide segregation. R-factor modeling indicates that disseminated sulfides are formed at the highest R-factors, while massive sulfides are formed at the lowest. Correspondingly, R-factor upgrading results in higher concentrations of Se and Ag in BMS minerals from disseminated sulfides compared to net-textured sulfides. Most chalcophile elements in BMS minerals show positive or negative correlations with whole-rock Cu/Nic ratios (Nic represents corrected whole-rock Ni content after deducting Ni in olivine), suggesting extensive chalcophile element fractionation occurred during progressive sulfide fractionation. Furthermore, the elements that are slightly to moderately incompatible with monosulfide solid solution (MSS) while predominately hosted by BMS minerals (e.g., Cd, Se, Ag, and Te in chalcopyrite) show better correlations, making them preferable for tracing the sulfide fractionation. Utilizing the partial least squares-discriminant analysis models, we propose plots of Cd/(Co + As) vs. Bi/(Co + As), Ag vs. Bi/(Ag + Cd), and Co/(Ag + Cd) vs. Bi/(Ag + Cd) to discriminate chalcopyrite from different intrusions, sulfide textures, and ore types, respectively. Additionally, the occurrence of chalcopyrite with increased Bi/(Ag + Cd) and Co/(Ag + Cd) ratios and decreased Ag content presents promising clues for exploring Fe-rich massive sulfide ores.

Paleovolcanism and the prospecting indicators and outlooks for discovery of new economic-grade copper-zinc massive sulfide ore deposits in the Verkhneuralsk ore region, Southern Urals

The principal regularities of distribution of the VMS type mineralization in the Verkhneuralsk ore region in the Southern Urals are characterized. Metallogenic factors of the first kind (stratigraphic, magmatic, lithological, and tectonic) and of the second kind (geotectonic and paleovolcanic) are
 shown. A combined convective-postmagmatic ore formation model for the VMS is briefly described, that takes into account a genetic relationship of the VMS ore formation to silicic magmatism of the basalt-rhyolite (“contrast”) volcanic formation, four types of such relationship being distinguished, the spatial, temporal, energetic, and compositional ones. The geological, geochemical, and geophysical prospecting indicators for the Ural type VMS mineralization are presented separately for various classes of forecasting metallogenic areas (ore regions, ore clusters, and ore fields and deposits). In the southern portion of the ore district, a site promising for revealing a new ore deposit has been identified, for which the category P2 forecasted resources have been estimated and a recommendation has been given for the geological exploration.

Polymetallic tungsten skarn mineralisation related to the Periadriatic intrusion at Lienzer Schlossberg, East Tyrol, Austria

Abstract A regional tungsten anomaly was discovered and explored in the Lienzer Schlossberg area that is part of the crystalline Austroalpine nappe complex of the Eastern Alps in the 1970/80-ties. Tungsten is present as scheelite, which occurs in steeply SSW dipping WNW-ENE oriented quartz veinlets and joints within the porphyritic dioritic to tonalitic/granodioritic host rocks of the Oligocene Lienz/Edenwald intrusion and in the exoskarn, which developed at the contact of the intrusion with Ca-rich lithologies. The skarn system is characterised by two stages: (1) a primary high-temperature calc-silicate stage characterised by grossular, diopside-hedenbergite, vesuvianite, wollastonite and Ca-plagioclase and (2) a retrograde skarn stage including scheelite-bearing massive sulphide ores (pyrrhotite, chalcopyrite, tremolite-actinolite, diopside-hedenbergite) and scheelite-rich fault rocks with calcite, sericite and chlorite. The two ore stages, the mineral paragenesis and composition is like that of a reduced tungsten skarn; i.e., garnet is grossular-rich, clinopyroxene is diopside-hedenbergite. Vesuvianite contains up to 1.8 mass % fluorine. Scheelite has been studied by cathodoluminescence (CL), electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. Three types of scheelite (Scheelite 1–3) are distinguished. In short-wave UV light, all types show blue fluorescence but CL revealed internal micro-textures in scheelite grains which are dominated by oscillatory zoning. Prolonged hydrothermal activity is indicated by dissolution-replacement and overgrowth textures affecting the primary zonation and trace element composition of scheelite. The distribution of rare earth elements (REE) in Scheelite 1 in tonalite-hosted quartz veinlets shows a convex (i.e., middle REE-enriched), heavy REE-depleted pattern with negative Eu anomalies (EuA ). The evolution of REE patterns from skarn-hosted Scheelite 2 and 3 illustrates a gradation of convex REE patterns with high ΣREE and distinct negative Eu anomalies to relatively flat REE patterns with small to no EuA . Scheelite at Lienzer Schlossberg has one of the highest ΣREE+Y contents of all scheelite-bearing ore settings in the Eastern Alps but incorporates minor Mo and the least Sr. High Na and Nb contents together with the positive correlation of REE+Y vs. Na+Nb+Ta suggests that the main exchange vectors for REE incorporation in scheelite is via a combined coupled substitution mechanism. Results of this study confirm the genetic similarity with reduced tungsten skarns and highlight the tungsten potential of this area.

History of the study and the principal features of the MVT-type lead-zinc massive sulfide deposits of the Priargunsk minerogenic zone

Two types of ore deposits are distinguished within the Priargunsk minerogenic zone: the lead-zinc massive sulfide ore deposits in the Vendian-Cambrian carbonate sedimentary rocks (MVT type) and the polymetallic massive sulfide ones in the Mesozoic volcanogenic rocks (VMS type). The MVT-type deposits are confined to the volcanogenic-carbonate–terrigenous formation and comprise two genetic types of the ore bodies, the stratiform (stratified) beds and the stockwork-shaped hydrothermal-metasomatic zones in the feeding channels. The stratiform ore bodies occur concordantly with stratification of the host rocks in gentle paleodepressions; they are confined to the contacts of limestones with dolomites and carbonaceous siltstones or are controlled by interlayer tectonic deformations. Ore deposits of this type formed synchronously with sedimentation. At the same time, the mechanism of formation of stratiform or stratified ore bodies could be fundamentally different.

Origin of Archean Pb isotope variability through open-system Paleoarchean crustal anatexis

Abstract Lead isotopic data imply that thorium and uranium were fractionated from one another in Earth’s early history; however, the origin of this fractionation is poorly understood. We report new in situ Pb isotope data from orthoclase in 144 granites sampled across the Archean Yilgarn craton (Western Australia) to characterize its Pb isotope variability and evolution. Granite Pb isotope compositions reveal three Pb sources, a mantle-derived Pb reservoir and two crustal Pb reservoirs, distinguished by their implied source 232Th/238U (κPb). High-κPb granites reflect sources with high 232Th/238U (~4.7) and are largely co-located with Eoarchean–Paleoarchean crust. The Pb isotope compositions of most granites, and those of volcanic-hosted massive sulfide (VHMS) and gold ores, define a mixing array between a mantle Pb source and a Th-rich Eoarchean–Paleoarchean source. Pb isotope modeling indicates that the high-κPb source rocks experienced Th/U fractionation at ca. 3.3 Ga. As Th/U fractionation in the Yilgarn craton must have occurred before Earth’s atmosphere was oxygenated, subaerial weathering cannot explain the apparent differences in their geochemical behavior. Instead, the high Th/U source reflects Eoarchean–Paleoarchean rocks that experienced prior high-temperature metamorphism, partial melting, and melt loss in the presence of a Th-sequestering mineral like monazite. Archean Pb isotope variability thus has its origins in open-system high-temperature metamorphic processes responsible for the differentiation and stabilization of Earth’s continental crust.

Porphyry and Volcanogenic Massive Sulphide Ore Deposit in Canada

Canada is one of the leading countries in ore production that involves variety types of ore deposits. Among the significant ore deposits found in the country, porphyry and volcanogenic massive sulphide (VMS) deposits stand out as major contributors to the production of copper, gold, molybdenite, zinc, lead and many other essential minerals. Porphyry deposits are the major copper production in the country that are predominantly located in British Columbia, where subduction processes occur. While the overall mineral grade of porphyry deposits is relatively low, their immense tonnage makes them the largest reservoirs of copper in Canada. Notable porphyry mines such as Copper Mountain and Highland Valley Copper produce millions of tons of ore annually. On the other hand, VMS deposits, associated with volcanic activities, play a significant role in the production of zinc, copper, lead, gold, and silver. These deposits are distributed across Canada, with concentrations found in the Ontario and British Colombia. VMS deposits make up nearly a quarter of the country's copper production with significant mine sites including Kidd Mine and Windy Craggy. The future of the mining industry in Canada and the whole world should be focusing on sustainability. Sustainable mining recognizes the interconnectedness of environmental, social, and economic aspects and seeks to balance them for the benefit of present and future generations.

The effects of indigenous microorganisms and water treatment with ion exchange resin on Cu-Ni flotation performance

Mineral processing utilizes large amounts of water and aims to reduce water consumption by recirculation and closing the water loops. This results in accumulation of chemical and biological contaminants in process water that may have adverse outcomes on the process performance. To optimize water quality suitable for each process step and plant, knowledge of both chemical and biological effects are needed as well as techniques to best remove the contaminants. This study focused on the consequences of microorganisms, enriched from the actual process earlier, on the flotation performance in the multi-metal Kevitsa mine in Northern Finland and the applicability of ion exchange for the removal of dissolved sulfur species and microorganisms from water. The increase of microbial load from the original 106 to added 107 16S rRNA copies mL−1 affected positively the flotation selectivity, especially in the case of nickel. Two tested water types, process water (PW) and final tailings water (FT), behaved slightly differently. In the Cu flotation phase added microorganisms did not affect the Cu recovery of FT but decreased significantly the recovery of Cu in PW. With equal Cu grade, the recovery was as high as approximately 25 percentage points lower. However, added microorganisms in both water types decreased notably the recovery of Ni in Cu concentrate (18 to 37 %-points). At the same time the amount of Ni recovered in the Ni concentrate increased by 18 to 33 %-points with added microorganisms. Visually the froth layer was higher and more stable in the Ni flotation in experiments with added microorganisms compared to experiments without added microorganisms. The concentrations of dissolved sulfate and thiosulfate ions were low in the studied waters compared to operations treating massive sulfide ores and did not significantly affect the flotation performance. For this reason, the IX water treatment was not required for these ions. However, the IX treatment proved to be effective in removing both sulfur species and microorganisms. The use of dissolved air flotation (DAF) was a successful pretreatment for ion exchange in removal of microorganisms. However, microorganisms are not usually taken into consideration when process performance or water cleaning techniques are designed and optimization could result generally in even better outcome.

Geology and sulphide geochemistry of the Ni-Cu-Co mineralisation of the Espedalen Complex, Norway: Constraints for the distribution of magmatic sulphides within a variably deformed anorthosite suite

The Espedalen Complex is located in the eastern portion of the Jotun–Valdres Nappe Complex, south-central Norway and comprises three main suites (jotunite-charnockite-augengneiss; main anorthosite–ultramafite–norite; and gabbronorite suites) formed between 1520 and 1500 Ma. The anorthosite-ultramafite-norite suite hosts Ni-Cu-Co mineralisations grouped as: i) ‘primary sulphides’ referring to undeformed occurrences with magmatic textures; ii) ‘deformed sulphides’ which include dismembered ore bodies; and iii) ‘remobilised sulphides’ which comprise thin sulphide veinlets indicating remobilisation. The ‘primary sulphides’ characterise the deposits of Dalen, Megrund, Trona, Veslegruva and Melgard, whereas the ‘deformed sulphides’ characterise the deposits of Stormyra, Storgruva, Andreasberg, Niccoline, Gråhøa, Jørstad and Grimstjønna. The largest mineralisations are the Dalen and Stormyra deposits, which host 5.3 Mt @ 0.29% Ni, 0.12% Cu and 0.02% Co, and 1.01 Mt @ 1.09% Ni, 0.48% Cu and 0.04% Co, respectively. This study provides the first systematic characterisation of the different Ni-Cu-Co mineralisations from the Espedalen Complex.Primary sulphides are typically hosted by medium-grained poikilitic olivine-orthopyroxenite, whereas deformed sulphides are hosted within shear zones, commonly within anorthosites. Primary and deformed occurrences comprise disseminated, net-textured and massive sulphides. The disseminated and semi-massive to massive sulphide ores from different localities comprise pyrrhotite and pentlandite with minor chalcopyrite. Post-magmatic sulphide alteration and recrystallisation (notably at Stormyra Deposit) are marked by variable (5 to 30%) development of pyrite, which replaces pyrrhotite-dominated masses. The remobilised sulphide assemblages are associated with retrograde silicates (e.g., chlorite and talc). Overall, primary and deformed sulphides can be divided into three main compositional groups based on metal tenors and the concentration of platinum-group elements (PGE): (i) Stormyra, Andreasberg (both deformed) and Megrund (primary) have the highest Ni and Cu tenors (7 to 8.5% and 3 to 3.5%, respectively) and no IPGE (Ir-group PGE) depletion relative to PPGE (Pt-group PGE); (ii) Dalen, Trona, Melgard (primary), Jørstad, Gråhøa and Grimstjønna (deformed) are similar regarding PGE distribution but have lower Ni and Cu tenors (4 to 5.5% and 1.6 to 3%, respectively); and (iii) Niccoline, Storgruva (deformed) and Veslegruva (primary) have comparable Ni and Cu tenors to group (ii), but are IPGE-depleted relative to PPGE (i.e. fractionated PGE distribution). The tenors vary from 0.3 to 2% Ni and 0.25 to 1.5% Cu in remobilised sulphides. Variations in metal tenors are interpreted to reflect a combination of different, but invariably PGE-depleted, parental magmas and variable R-factor regimes (R-factor varying from 350 to 700) during ore formation. The parental magmas can be modelled as the product of 15% mantle melting followed by approximately 2% crystallisation with sulphide removal, which lead to a PGE-depleted nature. Redistribution of sulphides during deformation of the Espedalen Complex seems to have taken place at large and small scales. Large-scale tectonic displacement has no major geochemical impact, whereas local remobilisation yielded sulphide veinlets with low metal tenors. We support that assessing if other geological domains, previously assigned to the Jotun-Valdres Nappe, are correlated or not with the Espedalen Complex is essential for further expanding this prospective area as these terrains could represent potential targets for Ni-Cu-Co deposits.

Behavior of palladium during fractionation of sulfide liquid: New constraints from the Kalatongke Cu-Ni sulfide-bearing intrusion in the central Asian orogenic belt, NW China

The distribution of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) in base metal sulfides (BMS) of magmatic Ni-Cu-(PGE) sulfide deposits has been extensively studied. However, the origin of Pd in pentlandite and the role of Te, As, Bi, Sb, and Se (TABS) in collecting PGE during fractionation of sulfide liquid have not yet been well constrained. Representative massive sulfide ores of the Kalatongke Cu-Ni sulfide-bearing mafic intrusion in the central Asian orogenic belt (CAOB) were selected to identify platinum-group minerals (PGM) using a scanning electron microscope (SEM) and to investigate the distribution of PGE and TABS in the BMS using in situ laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS). The results show that concentrations of Os, Ir, Ru, Rh, and Pt in the BMS are all below or close to the detection limits and only pentlandite contains 0.1 to 3.6 ppm Pd. Three generations of pentlandite are recognized in the massive sulfide ores; i.e., coarse-grained, granular pentlandite that crystallized earlier from monosulfide solid solution (MSS) prior to crystallization of pyrrhotite, loop-textured pentlandite around pyrrhotite that crystallized after pyrrhotite, and pentlandite that crystallized from evolved Fe-rich MSS and is associated with fine-grained myrmekitic magnetite. Granular pentlandite contains higher Pd (1.4 to 3.6 ppm) than that of loop-textured pentlandite (0.8 to 1.7 ppm Pd) and pentlandite associated with myrmekitic magnetite (0.1 to 0.5 ppm Pd). Given that Pd is incompatible to MSS during fractionation of sulfide liquid and is preferentially concentrated to residual sulfide liquid, we propose that the distribution of Pd in pentlandite may be attributed to rapid diffusion of Pd from the residual sulfide liquid into MSS/pentlandite on cooling and that Pd concentrations in the three generations were likely controlled by their crystallization sequence from MSS. In addition, LA-ICP-MS elemental mapping for BMS shows that TABS are not preferentially concentrated in chalcopyrite and euhedral Ni-merenskyite [(Pd,Pt)(Te,Bi)2] grains are mainly enclosed within pyrrhotite (n = 187) rather than chalcopyrite (n = 19). The random distribution of Ni-merenskyite in the BMS is supportive of an idea that Pt and a portion of Pd were likely stabilized by the presence of Te and Bi ligands in sulfide liquid and Te-Bi-Pd-Pt associations were then randomly distributed in MSS and intermediate solid solution (ISS) during fractionation of sulfide liquid. This study shows that the formation of TABS-bearing PGM in the massive sulfide ores of the Kalatongke intrusion was not controlled by fractionation of sulfide liquid, providing a new case that the behavior of PGE is mainly controlled by TABS rather than their partitioning coefficients in sulfide liquid.

Classification of Polymetallic Ore-Forming Processes and Transitional VMS–SEDEX–MV-type: the Example of the Giant Ozernoe Deposit in Transbaikalia, Russia

This article discusses the general classification approaches and key features of different families of polymetallic deposits, with particular attention to the largest in Eurasia Ozernoe polymetallic deposit located in Western Transbaikalia and thoroughly explored 50 years ago. The main groups (or families) of polymetallic deposits in the English-language literature are identified by brief names: volcanogenic massive sulphide (VMS), sedimentary exhalative (SEDEX), and Mississippi Valley type (MVT). Within these three families of deposits, there are many additional types/subtypes, a large number of which are mostly due to the incompleteness and inconsistency of accumulated knowledge on the genesis of polymetallic deposits. Overall, all Pb–Zn(Ag,Cu) deposits—both those that are considered syngenetic, forming on and near the seafloor (VMS and SEDEX), and epigenetic low-temperature ones (MVT)—demonstrate a wide range of features that distinguish and bring together these families. This also applies to the types and subtypes of mineral deposits identified within them. One of the most complex objects for geological–genetic classification is the Ozernoe deposit studied by the authors, which, in terms of the nature of the host rocks, is intermediate between the end members of all three families: SEDEX, VMS and MVT. The deposit is localized in volcanic–carbonate–terrigenous rocks of the Cambrian Oldynda formation, but the age and stratigraphic affiliation of the ore-bearing series remain a matter of debate. The Ozernoe deposit is a combination of massive sulfide and siderite ore beds, ore breccia horizons, low-carbonate aleuropelite members, limestones, fine detrital tuffites, lavas, and tuffs. The sulfide bodies are confined to several stratigraphic levels, and the main productive unit thickness reaches 230 m. The thickness is comprised of 12 mineral lodes, a series of stratified ore bodies separated by gangue layers of sedimentary and volcaniclastic rocks. The primary ore minerals are pyrite, sphalerite, and galena, while the minor minerals include magnetite, chalcopyrite, marcasite, tetrahedrite, and arsenopyrite. There are two main theories regarding the origin of the ore: volcanogenic–sedimentary and hydrothermal–metasomatic. The hydrothermal–sedimentary theory remains the prevailing hypothesis, but there are many indications that epigenetic hydrothermal–metasomatic and dynamic metamorphic processes have contributed to the formation of the deposit. These include the appearance of sulfide–quartz and quartz–carbonate–sulfide veins and vein zones in fine-grained “layered” ores, with large crystalline sphalerite and galena; multiple signs of ore recrystallization, including the formation of pyrite porphyroblasts and arsenopyrite metacrystals; and the formation of solid pyrrhotite and pyrrhotite–magnetite ores with a lenticular-striped, gneissic structure. These observations suggest that different processes, both hydrothermal–sedimentary and metamorphogenetic–metasomatic, were involved in the formation of the Ozernoe deposit. In other words, primary hydrothermal–sedimentary ores were redeposited by late hydrothermal solutions. Nevertheless, many issues concerning the genesis of the Ozernoe deposit remain unresolved.

An Early Cretaceous magmatic-hydrothermal origin of the Shanhou stratabound Pb-Zn deposit in Fujian Province of southeast China: Constraints from hydrothermal titanite U-Pb dating and C-O-S-Pb isotopes

Stratabound base metal sulfide deposits within Neoproterozoic metavolcanic rocks and skarns in the Fujian Province are important Zn-Pb producers in China. To date, the inability to determine absolute ages and proper sources of Pb-Zn mineralization has led to conflicting ore genetic models. These include the metamorphosed volcanogenic massive sulfide (VMS) model, which predicts that the Pb-Zn mineralization was synchronous with submarine volcanic activity, and the Early Cretaceous magmatic-hydrothermal skarn model. The Shanhou deposit (2.56 Mt ore @ 6.8 % Pb + Zn) in the central Fujian Province, the southeastern coastal area of China, consists of twelve stratabound massive Pb-Zn sulfide orebodies hosted in hydrothermally altered metavolcanic rocks of the Neoproterozoic Dongyan Formation. No intrusive body that could have contributed to the formation of the calc-silicate mineral-dominated wall rocks and Pb-Zn ores has been found spatially associated with the Shanhou deposit, and the origin of the mineralizing fluids, sulfur, and metals has not yet been identified previously. Here we present in-situ U-Pb ages of hydrothermal titanite and C-O-S-Pb isotopes of gangue and ore minerals to constrain the timing and origin of the Pb-Zn mineralization. Three hydrothermal stages can be identified: pyroxene (prograde stage I), epidote + chlorite + titanite (retrograde stage II), and quartz + calcite + polymetallic sulfides (quartz-calcite-sulfide stage III). In-situ LA-ICP-MS U-Pb isotopic analyses of hydrothermal titanites coexisting with sulfides in two massive ore samples yield indistinguishable ages of 145 ± 13 Ma and 144 ± 9 Ma, overlapping the 152 to 145 Ma emplacement age of granitic rocks in the central Fujian area. The results show that the Shanhou Pb-Zn deposit is significantly younger than the Neoproterozoic host (meta)volcanic rocks, arguing against a Neoproterozoic VMS genetic model as suggested by some previous researchers. The δ34S (V-CDT) values of pyrrhotite, pyrite, marcasite, chalcopyrite, sphalerite, and galena in the massive sulfide ores range from −2.9 to 6.9 ‰, indicating that the sulfur at Shanhou is mainly of magmatic origin. Sphalerite separates have 206Pb/204Pb ratios of 17.782 to 17.782, 207Pb/204Pb ratios of 15.585 to 15.593, and 208Pb/204Pb ratios of 38.376 to 38.407, which are similar to those of the host rocks, indicating that the ore-forming materials were derived from the host rocks. Calcite in sulfide ores has δ13CV-PDB values of −7.8 to −4.3 ‰ and δ18OV-SMOW values of 6.1 to 9.5 ‰, suggesting a magmatic origin for the ore-forming fluids. It is concluded that the Shanhou stratabound Pb-Zn deposit is a metasomatic skarn-like deposit associated with a possible hidden Early Cretaceous felsic intrusion at depth, rather than a metamorphosed VMS deposit.

Archean Pb isotope variability tracks crust-mantle fractionation, granite production, and ore deposit formation

Various geological processes that affect Earth's crust may be encoded into isotopic tracers preserved in rocks and minerals. The enhanced sensitivity of U, Th, and Pb to crustal fractionation processes allows Pb isotopes to complement information from the Nd and Hf isotope systems. However, melt fractionation, crustal contamination and recycling, hydrothermal fluid flow and fluid-rock interaction, and other processes in the continental crust can lead to mixing of Pb isotopic signatures. Here, we report new Pb isotopic data from granite-K-feldspar and integrate these data with published Pb isotope ratios from granite K-feldspar and Pb-rich ores across the Yilgarn Craton in Western Australia. The aim of this study is to explore how the variability of Pb isotope ratios and derivative parameters can be used to gain information on specific geological processes occurring throughout the crustal column. We develop a model that subdivides different sampling media into chemical process groups and links their initial Pb signatures to Pb source regions and fractionation processes at various locations within the crust and upper mantle. Equilibration of Pb signatures with a primary mantle source reservoir (in part represented by volcanic-hosted massive sulfides) is contrasted with granite formation in the mid to lower crust (granite K-feldspar), and mineralization of ore deposits in the mid to upper crust (Pb-rich ores). Spatial trends similar to those in Nd and Hf isotopic data are recorded by Pb isotopic derivative parameters (μ = source 238U/204Pb, ω = 232Th/204Pb, and Δt - the difference between true sample age and Pb model age) calculated for komatiite-hosted Ni sulfide ores, granite K-feldspar, and volcanic-hosted massive sulfide (VHMS) ores. The significance of subtle differences in absolute values of derivative parameters is supported by the diversity of Pb isotope ratios, Pb model ages, and ∆t as tracked by a statistical metric, quantifying the variability of Pb sources involved in the formation of different chemical process groups. Generally greater variety in an older terrane (Youanmi) documents more ancient and recycled continental crust as compared with more homogeneous Pb isotopic signatures in a younger terrane (Eastern Goldfields Superterrane). The Pb signatures are interpreted, in part, to relate to the timing of source fractionation in the upper mantle with a legacy of this source signal preserved through various depths in the lithospheric section. The least radiogenic VHMS ore samples appear to provide a good approximation of mantle Pb signatures, indicated for example by a deficit in 206Pb and 208Pb relative to the other process groups. A significant heterogeneity recorded in Pb isotopic data from Pb-rich gold ores is explained by the interplay of hydrothermal fluids with diverse sources leading to the mineralization of gold deposits (e.g., leaching of Pb from surrounding rocks or fluid mixing). Such gold ore Pb signatures are distinct from other process groups, which together track sources less heterogeneous in age and/or U and Th.

Mineralogy and geochemistry of platinum-group elements in the zoned mafic-ultramafic intrusions of the Uralian Platinum belt, Russia

Three styles of platinum-group element mineralization occur within the Ural-Alaskan type complexes of the Uralian Platinum belt: chromite-platinum, noble metal, and noble metal-copper ones. They are associated with dunite and chromitite (chromite-platinum), pyroxenite (noble metal) and gabbro (noble metal-copper). Three common platinum group element distribution patterns are observed for dunite and chromitite: (1) M-shaped (defined by positive Ir and Pt anomalies); (2) with positive Ir-Rh(Pt) anomalies; and (3) W-shaped with positive Os and Pt, or Os and Rh anomalies. In contrast, pyroxenite and gabbro are enriched in Pd and Au. The PGM assemblages correlate to the PGE + Au distribution patterns as exemplified by the predominance of Ir-rich Pt-Fe alloys within dunite and chromitite. The noble metal assemblages of pyroxenite and gabbro comprise tellurides, arsenides, and various Pd minerals, as well as native gold and Au-Ag alloy. An indicative Pd/Ir ratio in a succession dunite-chromitite-gabbro increases from 0.04 to 148 with a maximum value of ~5000 in massive sulfide ore of the Volkovsky that is attributable to the contrasting magma compositions defining chromite vs sulfide controls over PGE concentration.

The improvement of sparsity gravity inversion using an adaptive lanczos bidiagonalization method

Inversion of gravity data is one the important steps in the interpretation of practical data. The detection of sharp boundaries between anomalous bodies and host rocks is an interesting point in the geological frameworks. The gravity inversion with sparsity constraint is a useful method to recover block subsurface density distribution, which is efficiently used for the quantitative interpretation of gravity data. The reweighted regularized method is a useful method to solve the inverse problem. However, in this type, we must face the updating gravity forward matrix and large matrix operation. The application of Lanczos bidiagonalization method can reduce the size of data and matrix in the inversion to resolve the large scale inversion problem. However, a very important problem is not resolved, which is update of reweighted forward matrix and new Lanczos bidiagonalization matrix. Here, an adaptive Lanczos bidiagonalization method is studied to select the Lanczos bidiagonalization factor. And a new projected method with adaptive Lanczos bidiagonalization method is study to avoid the updating sparsity reweighted function. We calculate the reweighted forward matrix and Lanczos bidiagonalization matrix only one time, which can essentially reduce the computational complexity. The inversion results of synthetic data show that the new improved method is faster and better than common reweight regularized Lanczos bidiagonalization method to produce an acceptable solution for focusing inverse problem. The improvement of adaptive Lanczos bidiagonalization in sparsity gravity inversion is also tested on gravity data collected over the Mobrun massive sulfide ore body in Noranda, Quebec, Canada. The inversion results indicate a remarkable correlation with true structure of the ore body that is achieved from drilling data.

Study of the effects of roasting and sodium thiosulfate on the extraction of silver from Volcanic Massive Sulfide ore

The main objectives of this article were to firstly decrease the amount of sulfide in the (Volcanic Massive Sulfide –VMS) in the eastern Sudan (Ariab) area through a roasting pretreatment, secondly determine the best and optimum (thiosulfate concentration – ammonia concentration – copper sulfate concentration - leaching time – pH) for extracting silver sulfide metal (Ag2S) also known as argentite from the same ore, thirdly using sodium cyanide concentration equal to the optimum thiosulfate concentration obtained from the experiments to determine which solvent is better at the same concentrations thiosulfate or cyanide.The leaching process took place at different concentrations, times, following a roasting pre-treatment at (300–400-500–600-700 °C), The Analytics of (ICP) and (XRF) showed that silver concentration is (10.91 PPM), iron is (15.76 PPM) and copper is (119.16 PPM), and the (SEM) analysis showed that Sulfur is present in the proportion of (26 %) in the ore, and from the study of fractions it became clear that the highest presence of silver was at the size (-106 + 75) micron.It was found that the best roasting temperature was (700 °C), and the best extraction using sodium thiosulfate was (61.06 %) at thiosulfate concentration (0.2 M) and ammonia concentration (0.2 M), time (6) hours, copper sulfate concentration (0.05 M), pH (10) and pulp density (25 %) at room temperature. As for sodium cyanide at the same concentration (0.2 M), it was found that the extraction was (49.47 %) at time (6) hours, pH (10), and pulp density (25 %). At room temperature, it was clear that cyanide was less efficient at (0.2 M) concentration than thiosulfate in dissolving silver.