Bulk Sulfide Research Articles

Relationship between bulk mineralogy and induced polarisation responses in iron oxide-copper-gold and porphyry copper mineralisation, northern Chile

We have studied the correlation between bulk mineralogy and induced polarisation (IP) responses in iron oxide-copper-gold (IOCG) and porphyry copper mineralised systems in northern Chile. Twelve drillholes (> 5000 m) that intersect IP sections were mapped and sampled to obtain geological characteristics and to quantify metallic minerals concentration in ore bodies. Geological parameters and modelled geophysical responses (electrical chargeability and resistivity) were compared using qualitative and quantitative criteria.Data analyses show that bulk sulphide concentration is the major factor that explains variations in the IP effect, even for IOCG ore bodies associated with magnetite mineralisation (up to 5 vol. %). Electrical chargeability exhibits a direct, but non-linear proportionality with sulphides content, while no clear trend is observed when chargeability is compared to magnetite concentration. In drillhole segments where macroscopic sulphides were not mapped, but IP results suggested high chargeabilities, petrographic studies revealed at least 1 vol. % of pyrite occurring as micro crystals (< 0.125 mm). The apparent resistivity data do not show any direct relationship with chargeability or sulphide contents.

Renal toxicity of nanoparticles of cadmium sulphide in rat

During present investigations, renal toxicity of CdSNPs (cadmium sulphide nanoparticles) (ranged 5–9 nm) was estimated in rat employing specific parameters. Treatment on each alternate day for 45 days with CdSNPs (10 mg/kg b.w.) yielded significant increase in Cd-MT (cadmium metallothionein), lipid peroxidation and H2O2 generation in the kidney of rat in comparison to bulk cadmium. Concentration of creatinine also increased in urine of CdSNPs treated rats. Histopathological observations revealed extensive damage in proximal tubules. Ultrastructural studies showed mitochondrial, nuclear and ER (endoplasmic reticulum) changes. Finally, renal toxicity of CdSNPs was confirmed by loss of alkaline phosphatase from the brush border of proximal convoluted tubules. These observations conclude that CdSNPs manifest greater toxicity in kidney than cadmium sulphide bulk particles. These effects have been attributed to their specific physicochemical properties, greater potential to generate ROS and induction of oxidative stress and impairment of renal structure and function. Present observations suggest that commercial/industrial use of CdSNPs may pose serious renal health problems in man.

Adsorption of hydrogen sulphide over rhodium/silica and rhodium/alumina at 293 and 873\xa0K, with co-adsorption of carbon monoxide and hydrogen

In this study, we have examined the adsorption of hydrogen sulphide and carbon monoxide over rhodium/silica and rhodium/alumina catalysts. Adsorption of hydrogen sulphide was measured at 293 and 873 K and at 873 K in a 1:1 ratio with hydrogen. At 293 K, over Rh/silica, hydrogen sulphide adsorption capacity was similar to that of carbon monoxide; however, over Rh/alumina, the carbon monoxide adsorption capacity was higher, probably due to the formation of RhI(CO)2. Over Rh/silica, the primary adsorbed state was HS(ads), in contrast to Rh/alumina, where the H2:S ratio was 1:1 indicating that the adsorbed state was S(ads). Competitive adsorption between CO and H2S over Rh/silica and Rh/alumina revealed adsorption sites on the metal that only adsorbed carbon monoxide, only adsorbed hydrogen sulphide or could adsorb both species. At 873 K, hydrogen sulphide adsorption produced the bulk sulphide Rh2S3; however, when a 1:1 H2:H2S mixture was used formation of the bulk sulphide was inhibited and a reduced amount of hydrogen sulphide was adsorbed.

SELECTIVE FLOTATION OF SULPHIDES FROM A GOLD MINING OPERATION

This paper presents a study to obtain sulphide as byproducts of a concentrated cleaner of gold generated from the flotation process of sulphide gold ore of mine Morro do Ouro. Chemical analysis of the concentrated of gold showed a content of approximately 22.05% S, in the form of a bulk sulphides. The liberation of the sulphides was measured using a SEM with second generation automated mineralogy (MLA). For the chalcopyrite recovery step, the fraction of liberated gangue particles is above 90%, for galena up to 92% and sphalerite above 96%, in all sizes. Moreover, the fractions of particles of minerals of interest that are completely liberated is ​​below 0.52% for the chalcopyrite recovery step, 0.65% for galena and 0.28% for sphalerite, in all sizes. The use of collectors Aero 3894, 3418A and 5100 allowed greater selectivity in the flotation circuit presented. The recoveries of chalcopyrite, galena and sphalerite in the Rougher steps were 82%, 73% and 62%, respectively.

Compositional variations of several Early Permian magmatic sulfide deposits in the Kalatongke district, southern Altai, western China: With genetic and exploration implications

A Permian magmatic Ni-Cu sulfide deposit cluster occurs in the Kalatongke district in the Southern Chinese Altai Orogenic Belt, western China. These deposits are associated with the mafic units of the Y1, Y2, Y3, Y9 and G21 mafic-intermediate complexes. In this paper we report the first zircon U-Pb ages for the Y3 and G21 intrusions, which are 283.3±1.3Ma and 281.1±1.5Ma, respectively. Our new age data confirm that the sulfide-bearing mafic units of the Y1, Y2 (connected with Y1 at depth), Y3, Y9 and G21 intrusions all formed in Early Permian between ∼281 and ∼287Ma. New and existing petrological-geochemical data show some important regular variations between these deposits. The host lithologies change from olivine-bearing rocks for the Y1-Y2-Y9 deposits to olivine-free rocks such as norite for the Y3 deposit and leucogabbro for the G21 deposit. The olivine Fo contents of the Y1 deposit are up to 82mol%, which are slightly higher than those of the Y2 deposit (up to 81mol%) and the Y9 deposit (up to 79mol%). The average plagioclase An contents of the olivine-bearing Y1-Y2-Y9 deposits are higher than those of the olivine-free Y3-G21 deposits. Among the three deposits (Y1, Y2 and Y3) that occur closely along the same structural lineament, the Ni/Cu ratios of bulk sulfides decrease from the olivine-bearing deposits (Y1 and Y2) to the olivine-free deposit (Y3). The PGE tenors of these deposits (Y1, Y2 and Y3) and the nearby coeval deposits (Y9 and G21) are extremely low, indicating that their parental magmas are severely depleted in PGEs. The variations of PGE tenors within a single deposit as well as among the different deposits are mainly due to variable R factors. The host rocks of these deposits are all characterized by elevated initial 87Sr/86Sr ratios from 0.7045 to 0.7047, positive εNd values from 4.95 to 6.86, positive εHf values of zircon from 9 to 16, and elevated δ18O values of zircon from 6.15 to 6.7‰. The isotope data indicate that the parental magmas for these deposits experienced up to ∼15wt% crustal contamination. The δ34S values of the sulfide minerals from these deposits are from −3.1‰ to 0.4‰, with a peak at −2.2‰, indicating the involvement of crustal sulfur. The isotope data and mineral chemistry together indicate that both olivine fractional crystallization and addition of crustal sulfur played a role in triggering sulfide saturation in the parental magmas for these deposits. Based on higher Ni/Cu ratios of sulfide mineralization in the olivine-bearing intrusions (Y1, Y2, Y9) than in the coeval olivine-free intrusions (Y3, G21), we recommend that Ni exploration in the region focus on the olivine-bearing intrusions that were emplaced in the Early Permian.

Unsupported trimetallic Ni(Co)-Mo-W sulphide catalysts prepared from mixed oxides: Characterisation and catalytic tests for simultaneous tetralin HDA and dibenzothiophene HDS reactions

Unsupported A-Mo-W (A=Ni or Co) sulphide catalysts were obtained from mixed oxides containing different W:Mo ratios. An in situ liquid-phase sulphidation of the mixed oxides in a batch reactor was followed by catalytic tests in a liquid-phase reaction (at 613K and 70bar), using a mixture of dibenzotiophene (DBT) and tetralin (THN) as the feed. After the catalytic tests, the bulk sulphide catalysts were characterised by nitrogen physical adsorption, XANES/EXAFS, SEM and HR-(S)TEM. The HR-TEM images showed randomly oriented, stacked-layer particles typical of Mo (W) sulphides and an elemental HR-STEM mapping evidenced Mo/W homogeneous distribution in the trimetallic sulphides. The EXAFS results for the trimetallic catalysts are consistent with the presence of nickel or cobalt sulphide domains, and Mo1-xWxS2 solid solutions. The intralayer Mo:W solid solutions were confirmed to be thermodynamically stable with respect to phase separation by DFT calculations, which were also used to aid in the interpretation of the EXAFS results. The effect of the W:Mo ratio on the catalytic properties of the Ni- and Co-containing series was found to be different. For the Ni series, increasing the W content caused an activity increase in THN hydrodearomatization (HDA) relative to DBT hydrodesulphurization (HDS), while it had little influence on the relative contribution of the direct desulphurisation (DDS) route with respect to the previous hydrogenation (HYD) route for DBT HDS. In contrast, for the Co series, the activities and selectivities were essentially insensitive to the W content. Both the Ni and Co series of unsupported sulphides were more selective for the HYD route in DBT HDS than a supported NiMo/Al2O3 catalyst.

Pilot scale microwave sorting of porphyry copper ores: Part 1 – Laboratory investigations

Microwave treatment followed by infrared thermal imaging (MW-IRT) has been proposed as a potential excitation-discrimination technique to facilitate sorting of porphyry copper ores. A continuous, high throughput (up to 100t/h), belt-based microwave cavity operating at up to 100kW has been designed to interface directly with commercially available sorters at industrially relevant scales. In this paper, the fragment-by-fragment thermal response of 16 porphyry copper ore samples following microwave treatment in the bespoke system is evaluated to elucidate key performance criteria and identify likely candidate ores for microwave sorting. Microwave treatment energy dose was found to be the driving force behind the ultimate average temperature fragments experience, with other process variables (e.g. belt speed, power, belt mass loading, thermal equilibration time) having little effect on sortability performance. While fragment mineralogical texture and ore textural heterogeneity were shown to influence the average temperature rise of the fragment surface presented to the thermal camera, in most cases this variability did not adversely affect sortability performance. An abundance of microwave-heating gangue minerals (e.g. iron sulphides, iron oxides and hydrated clays) was shown to be the dominant source of deviation from intrinsic sortability. However, low average moisture content and co-mineralisation of copper and iron sulphides (or bulk sulphide sorting) was found to mitigate the deviation and provide better sortability performance. An attractive separation could be proposed for many of the ores tested, either to remove a large proportion of barren fragments from ore-grade material or concentrate a large proportion of copper values from waste-grade material.

How sulfate-driven anaerobic oxidation of methane affects the sulfur isotopic composition of pyrite: A SIMS study from the South China Sea

Sulfate-driven anaerobic oxidation of methane (SO4-AOM) in marine sediments commonly leads to the precipitation of pyrite. It is, however, frequently challenging to unequivocally unravel the entire history of pyritization, because of the common coexistence of SO4-AOM derived pyrite with pyrite resulting from organiclastic sulfate reduction (OSR). To better understand how SO4-AOM affects pyritization in methane-bearing sediments and how this can be identified, we applied secondary ion mass spectroscopy (SIMS) to analyze the sulfur isotope composition (δ34S) of authigenic pyrite in addition to sulfur isotope measurements of bulk sulfide and hand-picked pyrite aggregates from the two seafloor sites, HS148 and HS217, in the Shenhu seepage area, South China Sea. Authigenic, mostly tubular pyrite aggregates from these sites consist of three types of pyrite: framboids, zoned aggregates with radial overgrowths surrounding a framboidal core, and euhedral pyrite crystals. Framboids with low SIMS δ34S values (as low as −41.6‰ at HS148, and −38.8‰ at HS217) are dispersed throughout the cores, but are especially abundant in the shallow part of the sedimentary column (i.e. above 483cmbsf in HS148; above 670cmbsf in HS217). These patterns are interpreted to reflect the dominance of OSR during early diagenetic processes in the shallow sediments. With increasing depth, both δ34S values of bulk sulfide minerals and hand-picked pyrite aggregates increase sharply at 483cmbsf in core HS148, and at 700cmbsf in core HS217, respectively. Radial pyrite overgrowths and euhedral crystals become abundant at depth typified by high δ34S values for hand-picked pyrite. Moreover, SIMS analysis reveals an extreme variability of δ34S values for the three pyrite types on a small scale in these zones. Besides some moderately 34S enriched framboids, most of the overgrowths and euhedral crystals display extremely high SIMS δ34S values (as high as +114.8‰ at HS148, and +74.3‰ at HS217), representing the heaviest stable sulfur isotope composition of pyrite ever reported to the best of our knowledge. Such an abrupt and extreme increase in δ34Spyrite values with depth is best explained by an enrichment of 34S in the pool of dissolved sulfide caused by SO4-AOM in the sulfate methane transition zone (SMTZ). The increase in δ34S values from framboidal cores to overgrowth layers and euhedral crystals indicates continuous, and finally near to complete exhaustion of dissolved sulfate at the SMTZ following a Rayleigh distillation process. SO4-AOM allowed for subsequent growth of later stage pyrite over the initial framboids, part of which formed earlier and at shallower depth by OSR. The combination of a detailed petrographic study of authigenic pyrite with SIMS analysis of stable sulfur isotopes in organic-rich strata proves to be a powerful tool for reconstructing the dynamics of sulfur cycling in modern and, potentially, ancient sedimentary sequences.

Geochronological, Petrological, and Geochemical Constraints on Ni-Cu Sulfide Mineralization in the Poyi Ultramafic-Troctolitic Intrusion in the Northeast Rim of the Tarim Craton, Western China

The Poyi magmatic Ni-Cu sulfide deposit is situated in the Beishan fold belt in the northeastern rim of the Tarim craton. Many Permian magmatic Ni-Cu sulfide deposits, such as those in East Tianshan, are present in the adjacent Central Asian orogenic belt to the north. The Poyi deposit is hosted in a small dike-like ultramafic-troctolitic body that was emplaced into a much larger gabbroic intrusion. Our new zircon U-Pb isotope data reveal that these two intrusions formed ~6 Ma apart. The ultramafic-troctolitic intrusion was emplaced at 269.9 ± 1.7 Ma, whereas the gabbroic intrusion was emplaced at 276.1 ± 1.9 Ma. The results show that the Poyi deposit is the youngest among the major magmatic Ni-Cu sulfide deposits (≥0.2 Mt Ni) of Permian ages in the Beishan-Tianshan region. Sulfide mineralization in the Poyi deposit occurs as steeply dipping disseminated sulfide lenses mostly associated with wehrlites in the center of the dike. Olivine from the Poyi ultramafic rocks has Fo content up to 91 mol %, which is similar to the lower limit of mantle olivine and the most primitive within the Permian Beishan-Tianshan nickel belt. Like other magmatic sulfide deposits in this belt, olivine from the Poyi deposit is depleted in Ca (<1,000 ppm). The estimated parental magma for the Poyi most primitive ultramafic rocks contains 15 ± 2 wt % MgO. Cotectic olivine-sulfide segregation from the Poyi magma is inferred from systematic variation of Fo-Ni contents in olivine from some sulfide-barren ultramafic rock samples, and supported by the occurrence of sulfide droplets as small inclusions in olivine (Fo90 mol %) in these rocks. The involvement of multiple pulses of sulfide-charged magma with different compositions is indicated by the abrupt change of olivine Fo content with depth and the presence of olivine with similar Fo contents but dramatically different Ni abundances in the different parts of the deposit. The (87Sr/86Sr)i ratios and ɛ Nd(total) of the Poyi ultramafic rocks and troctolites range from 0.7042 to 0.7052 and from 4.9 to 6.0, respectively, which are close to the isotope compositions of depleted mantle and within the ranges of major magmatic Ni-Cu sulfide deposits of Permian ages in East Tianshan. No more than 5 wt % of bulk crustal contamination is required to explain the variations of Sr-Nd isotopes in the Poyi ultramafic-troctolitic intrusion. The abundances of incompatible trace elements in whole rocks and clinopyroxene crystals indicate very weak light REE enrichments coupled by significant negative Nb-Ta anomalies in the parental melts. Bulk sulfides in the Poyi deposit are characterized by positive correlations between any pair of platinum-group elements (PGE), indicating that PGE tenor variations in the deposit are mainly controlled by variable R-factors (magma/sulfide mass ratios). The estimated initial concentrations of PGE in the parental magma for the Poyi deposit are almost two orders of magnitude lower than the abundances of PGE in some continental picrites. Given that the parental magma for the Poyi deposit is as primitive as a primary mantle-derived magma, the depletion of PGE in the Poyi deposit is most likely due to previous sulfide segregation at depth. Based on these observations, we conclude that sulfide saturation in the Poyi PGE-depleted, Mg-rich magma was triggered by addition of crustal sulfur during magma ascent and that the Poyi deposit was a dynamic conduit used by multiple pulses of olivine- and sulfide-charged magma.

Froth flotation of a Merensky Reef platinum bearing ore using mixtures of SIBX with a dithiophosphate and a dithiocarbamate

The Bushveld Igneous Complex (BIC) in northern South Africa has the largest deposit of platinum group elements (PGEs) in the world. In trace amounts, these are closely associated with base metal sulphides (BMS). Froth flotation is used as a bulk sulphide recovery to beneficiate these PGEores. To maximise the recovery of the PGEs it is required to improve the recovery of the BMS. The chemical additives used largely determines the performance of the froth flotation process. Consequently, mixtures of collectors were used in batch froth flotation tests in an attempt to improve concentrate grades and recoveries of BMS from a Merensky Reef platinum ore. The mixtures consisted of a xanthate (SIBX) with a dithiophosphate (DTP) or a dithiocarbamate (DTC). Each mixture was tested at mole ratios of 80:20 and 60:40, with the xanthate the major component. An increase in nickel recovery was observed with all mixtures relative to pure SIBX at the expense of concentrate grade. The mixtures of DTC with SIBX increased the cumulative nickel recovery by 11%, while the mixtures with DTP increased it by 10%. Copper recovery increased by 6% with the DTP mixtures. No significant improvements in the copper recoveries and grades were observed with the mixtures of SIBX with DTC compared to pure SIBX.

Mineral associations and major element compositions of base metal sulphides from the subcontinental lithospheric mantle of NE Spain

This study deals with textural types and major element compositions of Cu-Ni-Fe sulphides from spinel lherzolite, harzburgite and olivine websterite xenoliths found in alkali basaltic rocks of the Neogene-Quaternary volcanic zone of Catalonia (NE Spain). Sulphides in harzburgites and websterites are scarce. Four textural types have been distinguished: inclusions in silicates and spinel, trails of small droplets often radiating from inclusions, interstitial grains, and grains related to pyrometamorphic textures. The mineral associations are dominated by one or two low-temperature monosulphide solid solutions: mss1, mss2, occasionally accompanied by pyrrhotite, pentlandite and Cu-rich sulphides. Compositions of mss1 are more Fe-enriched in inclusions and interstitial grains than in grains related to pyrometamorphism. Compositions of mss2 are Ni-rich very close to pentlandite. Sulphide bulk compositions correspond to high-temperature monosulphide solid solution equilibrated with a relatively Cu-Ni enriched sulphide melt at 1100–1000 °C. The breakdown products of these earlier compositions could have been either equilibrated below 600, 300 °C or being at disequilibrium. A restitic origin is consistent with the main sulphide mineral associations, the estimated melt extraction for peridotites (<30 %) and with the fact that lherzolites are less affected by cryptic metasomatism than harzburgites. However, Ni exchange coefficients between olivine and the high-temperature monosulphide solid solution underestimate equilibrium values. This suggests that some lherzolites could derive from pervasive refertilization. The scarcity of sulphides in websterites is explained by S incompatible behaviour during the formation of earlier cumulates from the mafic alkaline magmas which caused the cryptic metasomatism.

Multiple S isotopes, zircon Hf isotopes, whole-rock Sr-Nd isotopes, and spatial variations of PGE tenors in the Jinchuan Ni-Cu-PGE deposit, NW China

Previous geochemical data for the Jinchuan Ni-Cu-(platinum-group elements, PGE) deposit, the single largest magmatic sulfide deposit in the world, are derived primarily from the upper parts of the deposit. This paper reports new PGE and S-Hf-Sr-Nd isotope data for the lower parts of the deposit that have become accessible for sampling by ongoing underground mining activity. New PGE data from this study, together with previous results, indicate that PGE tenors in the bulk sulfide ores of the deposit increase eastward, except for two fault-offset ore zones which occur together within the western part of the deposit. Generally, these two ore zones show depletions in IPGE (Ir, Ru, Rh) but not in PPGE (Pt, Pd) and Cu, and more fractionated olivine and Cr-spinel compositions than the rest of the deposit. These differences can be explained by a more evolved parental magma for the IPGE-depleted ore zones. The eastward increase of PGE tenors in the rest of the deposit can be explained by upgrading of preexisting sulfide liquid in a subhorizontal conduit by a new surge of magma moving through the conduit from west to east, which took place before the formation of the IPGE-depleted ore zones. The Jinchuan ultramafic rocks are characterized by elevated initial 87Sr/86Sr ratios from 0.7077 to 0.7093, negative e Nd values from −9.2 to −10.5, and zircon e Hf values from −4 to −7. These data indicate up to 20 % of crustal contamination in the Jinchuan magma. Four of nine multiple sulfur isotope analyses for the Jinchuan deposit show anomalous ∆33S values varying from 0.12 to 2.67 ‰. These results, together with elevated δ34S values (>2 ‰) for some of the samples analyzed previously by other researchers, indicate the involvement of external sulfur from Archean and Proterozoic sedimentary rocks. Modeling results based on our olivine data and magma compositions estimated previously by other researchers indicate that fractional crystallization did not play a major role in triggering sulfide saturation in the Jinchuan magma and that the parental magma experienced previous sulfide segregation during ascent or in staging chambers.

Surface composition of PdCuAu ternary alloys: a combined LEIS and XPS study

PdCuAu ternary alloy samples with different composition were synthesized on top of ZrO2‐modified porous stainless steel disks by the sequential electroless deposition technique. The structure, morphology and bulk composition of the samples were characterized by X‐ray diffraction (XRD), scanning electron microscopy and energy dispersive X‐ray spectroscopy (EDX). Complete alloy formation with a pure fcc phase for the Pd71Cu26Au3, Pd70Cu25Au5 and Pd67Cu24Au9 samples and a bcc structure for the Pd62Cu36Au2 and Pd60Cu37Au3 samples were obtained upon annealing at 500 °C for 120 h as revealed by XRD. A combination of low‐energy ion scattering (LEIS) and X‐ray photoelectron spectroscopy (XPS) was used to investigate the surface properties of the PdCuAu alloys. XPS results confirmed alloy formation under the annealing conditions. XPS analysis also revealed that the near‐surface regions of the alloys became enriched in Pd with respect to the bulk composition determined by EDX. In contrast, LEIS and angle‐resolved XPS analyses showed that the top‐most surface layers in all samples were copper‐rich compared with the bulk composition. This high Cu surface concentration could impart resistance to bulk sulfide formation to the PdCuAu alloy membranes. Copyright © 2015 John Wiley &amp; Sons, Ltd.

The leaching of sulfide iron (II) with sulfuric acid

The leaching of iron (II) sulfate concentrate from Chaabet El Hamra, Algeria bulk sulphide ore with sphalerite concentrate in presence of sulfuric acid and hydrogen peroxide at low stirring rates (100 rpm). The influence of leaching temperature, leaching time, particle size and sulfuric acid concentration were studied. In this paper we focused our attention on the process of direct leaching of iron (II) sulfate concentrate with sulfuric acid. The results of leaching show that the combination of sulphuric acid and hydrogen peroxide enhances the dissolution of the bulk sulphide ore. The Leaching rate was studied as a function of the leaching temperature, the leaching time, the particle size and the sulfuric acid H2SO4 concentration. The optimal operational conditions were as follows: leaching temperature 100°C; leaching time 2 hours; sulfuric acid concentration 2 mol/L-1; the smaller particle size 63 µm and the solid-toliquid ratio 1:10. In these values the maximum extraction of iron (II) sulfates is 0.0416 mol/L-1.

PdCuAu ternary alloy membranes: Hydrogen permeation properties in the presence of H2S

PdCuAu ternary alloy membranes with different component compositions were synthesized by sequential electroless deposition of components onto porous stainless steel substrates. The ternary with the highest Au content, Pd69Cu14Au17, exhibited the highest hydrogen permeation flux, comparable to that of a Pd91Au9 membrane. Upon exposure to 100ppm H2S/H2 at 673 K for 24h, all PdCuAu membranes experienced flux reductions of ~55%, followed by recovery to ~80% of the initial hydrogen flux upon reintroduction of pure hydrogen at 400°C. Complete flux recovery after H2S exposure required hydrogen treatment at 500°C. X-ray diffraction (XRD) analysis of the H2S-exposed PdCuAu membranes revealed fcc alloy structure with no evidence of bulk sulfide formation. In agreement with the XRD results, sulfur was not detected in the bulk of H2S-exposed samples by energy dispersive spectroscopy (EDS). However, analysis of H2S-exposed PdCuAu alloys by X-ray photoelectron spectroscopy (XPS) depth profiling revealed low, but measureable, amounts of sulfur in the near-surface region, about 10nm in depth. The depth profiles of samples after hydrogen recovery treatment showed significantly reduced sulfur content. These results indicate that H2S exposure causes flux loss in PdCuAu alloys through a surface-poisoning mechanism, and that the surface sulfide can be removed—and flux recovered—by high temperature treatment in hydrogen.

New ternary compounds containing Zn–Cu and Zn–Ag from single molecular source precursors

Heterobimetallic complexes [(PPh3)Cu(SCOPh)3Zn(PPh3)] and [(PPh3)2Ag(SCOPh)2Zn(SCOPh)(0.5H2O)] were used as single molecular sources for the syntheses of ternary compounds. These complexes upon pyrolysis at 350 °C in the solid state yielded ZnS/CuS and ZnS/Ag2S alloys respectively. In oleylamine solution decomposition of the complexes took place at 165 °C only leading to the formation of the corresponding sulfide nanoparticles. The bulk sulfide materials have been characterized by SEM-EDX, XPS and powder X-ray diffraction techniques. The nanoparticles have been characterized by EDS-elemental mapping and HRTEM.

Simultaneous tetralin HDA and dibenzothiophene HDS reactions on NiMo bulk sulphide catalysts obtained from mixed oxides

Large selectivity differences were found between supported and unsupported NiMoS catalysts in dibenzothiophene HDS and tetralin HDA.

PGE and Isotope (Hf-Sr-Nd-Pb) Constraints on the Origin of the Huangshandong Magmatic Ni-Cu Sulfide Deposit in the Central Asian Orogenic Belt, Northwestern China

Many magmatic Ni-Cu sulfide deposits have been found to be associated with Permian basaltic magmatism in the Central Asian orogenic belt, Xinjiang, China. The style of basaltic magmatism and the origin of associated Ni-Cu sulfide deposits in the region are highly debated. The Huangshandong mafic-ultramafic intrusion is at the center of the debate mainly because it hosts the largest magmatic Ni-Cu sulfide deposit in the region. In this paper we report integrated petrological and geochemical data for the Huangshandong Ni-Cu sulfide deposit. The host intrusion consists of a massive gabbronorite unit and a layered sequence, which is composed of two to three ultramafic layers overlain by gabbroic rocks with visible modal layering. Important sulfide mineralization in the intrusion is associated with the ultramafic rocks and massive gabbronorite. The ultramafic rocks and massive gabbronorite are characterized by moderate enrichments in light rare earth elements (LREE), pronounced negative Nb-Ta anomalies relative to Th and La, positive eNd (t = 274 Ma) values (6.6−8.3), low initial 87 Sr/ 86 Sr ratios (0.7031−0.7038), low initial 206 Pb/ 204 Pb ratios (17.7−18), and positive eHf values of zircon (14−17). These data are consistent with mixing between a depleted mantle-derived magma and a granitic melt formed by partial melting of a juvenile arc crust as a result of mafic magma underplating. Olivine crystals enclosed in large clinopyroxene and plagioclase crystals from the ultramafic rocks have Fo contents up to 83 mol %. The contents of Ni in the olivine crystals decrease rapidly with Fo contents, indicating sulfide segregation from magma during olivine crystallization. Numerical modeling using bulk sulfide compositions and constraints from olivine-liquid relationships reveals that the parental magma of the intrusion was significantly depleted in PGE and contained <7 wt % MgO. Depletion of PGE in the magma can be explained by previous sulfide segregation possibly due to magma mixing in a staging chamber. Fractional crystallization and addition of external sulfides from juvenile arc crust appear to have played a critical role in triggering the second event of sulfide segregation to form the deposit. We believe that the Huangshandong sulfide ore-bearing intrusion formed by basaltic magmatism related to postsubduction delamination and asthenosphere upwelling instead of a deep-seated mantle plume.

The Origin of Ni-Cu-PGE Sulfide Mineralization in the Margin of the Zhubu Mafic-Ultramafic Intrusion in the Emeishan Large Igneous Province, Southwestern China

The Zhubu magmatic Ni-Cu-PGE sulfide deposit is hosted in a mafic-ultramafic intrusion which is part of the Emeishan large igneous province in southwest China. The Zhubu intrusion is composed of a layered sequence (750 X 400 X 600 m) with subhorizontal modal layering and a subvertical marginal zone of <40 m across. The marginal zone is composed of Iherzolite and olivine websterite with minor gabbroic rocks. The layered sequence is composed of Iherzolite, websterite, gabbro, and gabbrodiorite from the base to the top. The Zhubu intrusion can be explained by two stages of formation, an early conduit stage for the marginal zone and a late in situ differentiation stage for the layered sequence. Most important Ni-Cu-PGE mineralization in the intrusion occurs as disseminated sulfides within the marginal zone. Olivine crystals from the marginal zone contain 81 to 84 mol % Fo and 1,600 to 1,900 ppm Ni. The rims of zoned olivine phenocrysts in the Emeishan picrites have similar Fo contents but significantly higher Ni contents (2,300-2,600 ppm). The olivine data indicate that the parental magma of the Zhubu ultramafic rocks is similar to the transporting magma of the Emeishan picrites in MgO/FeO ratios but depleted in Ni due to sulfide segregation before olivine crystallization. The initial concentrations of PGE in the Zhubu magma, estimated from bulk sulfide compositions, are 7 ppb Pd, 9.3 ppb Pt, and 0.8 ppb Ir, similar to the values in the Emeishan picrites. Like the Emeishan picrites, the Zhubu intrusive rocks are characterized by light REE enrichments. Negative Nb anomalies relative to Th and Ta, which are rare in the Emeishan picrites, are present in the Zhubu samples. The (Sr-87/Sr-86)(i) and epsilon(Nd) values of the Zhubu intrusive rocks vary from 0.709591 to 0.710692 and from -2 to -3, respectively. The trace element and isotope compositions indicate that the Zhubu magma was contaminated by crustal materials, supporting the interpretation that sulfide saturation in the magma was triggered by crustal contamination. The area where the lower part of the conduit may have been brought up by faulting should be the focus of future exploration at Zhubu.

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

The ~216 Ma Hongqiling No. 7 intrusion is located in the southern margin of the Central Asian orogenic belt, northeastern China. It was the second largest Ni producer after Jinchuan in China. The intrusion crops out in an area of ~0.013 km2 on the surface. It intruded gneisses and marbles of the Paleozoic Hulan Formation. The intrusion is mainly composed of orthopyroxenite (~95 vol %), with minor harzburgite and norite. Over 90 vol % of the intrusion contains disseminated, net-textured or massive sulfides. The bulk sulfide ores (recalculated to 100% sulfide) have low average PGE concentrations (5.6 ppb Os, 3.1 ppb Ir, 4.7 ppb Ru, 2.2 ppb Rh, 31 ppb Pt, and 11 ppb Pd) and high Cu/Pd ratios (3 × 105–3 × 107), consistent with the compositions of sulfide liquids segregated from PGE-depleted magma. Olivine composition (Fo <86 mol %) indicates a fractionated parental magma. Back calculation shows that the parental magma was possibly derived by olivine fractionation from a primary magma containing ~16 wt % MgO. Numerical modeling indicates that PGE depletion in the parental magma of the Hongqiling No. 7 intrusion was due to previous sulfide segregation in the staging chamber. Whole-rock data show light rare earth element (REE) enrichments, negative Nb-Ta anomalies, and positive ɛ Nd ( t = 216 Ma) values from 3 to 5, which can be explained by mixing of a mantle-derived magma with a granitic melt formed by magma underplating in the crust. The γ Os ( t = 216 Ma) values of sulfide ores vary from 50 to 187. The highly variable γ Os( t ) values coupled with similar ɛ Nd( t ) values indicate preferential assimilation of crustal sulfides during magma rock interaction. Based on the observations, we propose that the parental magma of the Hongqiling No. 7 intrusion formed by contamination of mantle-derived, S-undersaturated magma by crustally derived granitic melt, together with olivine crystallization, in a staging chamber. The contaminated magma became PGE depleted due to sulfide segregation in response to crustal contamination. The PGE-depleted magma became S undersaturated again during ascent due to the negative effect of pressure on the maximum solubility of sulfur in magma. Upon arrival near the present level of the Hongqiling No. 7 intrusion a second event of sulfide segregation took place due to addition of crustal sulfides from immediate country rocks. The immiscible sulfide liquids and orthopyroxene crystallizing from the magma were retained in a dynamic conduit to form the ore-bearing intrusion while much of the magma left the conduit to form some of the nearby sulfide-poor intrusions. We suggest future exploration in the region to focus on olivine-bearing and orthopyroxene-dominant intrusions with ages similar to that of the Hongqiling No. 7 intrusion.