Fe Au Research Articles

Tribological properties of nanostripe surface structures—a design concept for improving tribological properties

The tribological properties of nanostripe surface structures were investigated using a pin-on-plate tribometer in order to propose a design concept for improving the tribological properties. The authors used four kinds of nanostripe structures consisting of different combinations of materials (Fe–Au, C–SiC, Al–Al2O3 and Al–Pt) fabricated by a process they had previously proposed. The frictional properties of the nanostripe structures depended on the materials that constituted the nanostripes. When the sliding direction in friction tests was parallel to the microgrooves, nanostripe structures remained on all surfaces even after friction tests. Based on the friction test results, the authors considered a design concept for nanostripe structures in tribological applications.

Preparation and specific properties of single crystalline metallic nanowires

AbstractDirectional solidification of eutectics is a route to produce iso‐oriented metallic single crystalline nanowires (NWs). Etching or electrochemical oxidation allows selective dissolution of either of the phases to produce NW arrays, isolated NWs, nanopore arrays and also derived structures by combining various process steps.A good understanding of the thermodynamics and the kinetics of the phase transformation and chemical reactions including electrodissolution, passivation, selective etching, complexing of reaction products and electrodeposition in the systems NiAl–X (X = Re, W, Mo), Ag–Cu and Fe–Au was reached. Functional devices based on these NWs, like high aspect ratio NW based STM tips, nanoelectromechanical systems (NEMS), NW pH sensors and sensor arrays were constructed. magnified imageArray of rhenium single crystalline NWs embedded in the NiAl matrix after partial dissolution of the matrix.

SIMS U–Pb zircon geochronology of porphyry Cu–Au–(Mo) deposits in the Yangtze River Metallogenic Belt, eastern China: Magmatic response to early Cretaceous lithospheric extension

The middle-lower reaches of the Yangtze River is one of the most important metallogenic belts in China, hosting numerous Cu–Fe–Au–Mo deposits. Previous chronological and geochemical investigations mostly focused on the magmatic rocks and associated deposits in the lower reaches of the river, but the timing and genesis of the Cu–Au–(Mo) mineralized porphyries in the middle reaches are yet to be well constrained. In this study we carried out precise SIMS U–Pb zircon age determinations for a number of Cu–Au–(Mo) mineralized porphyries and barren granitoid intrusions in the Jiurui and Edong mining districts in the middle reaches of the Yangtze River valley. Our new age results reveal two discrete magmatic and mineralization events at ca. 145–146 Ma and ca. 140 Ma in the study area. The ca. 145–146 Ma granitoids signify the start of the Cretaceous magmatism in the Yangtze River Metallogenic Belt, coinciding temporally with a regional tectonic switching from a Late Jurassic transpressive tectonic regime to an earliest Cretaceous extensional regime in eastern China.

Some features of acetylene hydrogenation on Au-iron oxide catalyst

Hydrogenation of acetylene has been investigated on Au-iron oxide catalysts containing 4.5, 3.0, 5.6 wt% Au prepared by deposition–precipitation (DP) with urea, adsorption of Au sol (SA) and by co-precipitation (CP) of HAuCl 4 and Fe(NO 3) 3, respectively. The latter method produced Au particles supported on 2-line ferrihydrite (Fe 5HO 8·4H 2O). Au/iron oxide catalyst precursors (Au/α-Fe 2O 3 and Au/2-line ferrihydrite) were characterized by BET, TGA, TPR and XRD, and the Au particle size by TEM measurements. The TPR measurements confirm the ease of transformation of 2-line ferrihydrite to magnetite (Fe 3O 4) and that the formation of magnetite from α-Fe 2O 3 depends strongly on the size of the gold and the supporting oxide particles. Particle size effect of gold has been investigated in semi-hydrogenation of acetylene. Temperature of hydrogen treatment has been observed to play a crucial role in the activity and ethylene selectivity. Au/FeO x samples hydrogen treated at 353–473 K prior to introduction of the reactants (H 2:C 2H 2 = 140, 0.11% C 2H 2) show very limited over-hydrogenation (ethane formation is less than ≈1%) and 2–4% selectivity of oligomer (C4+) formation at 353–473 K. Hydrogen treatment of the samples at T > 573 K but lower than the wüstite (FeO) stability point (≈843 K) resulted in partial reduction of Fe 3O 4 and formation of Fe 0. The shift of Au(1 1 1) XRD line to higher 2 Θ provided evidence for the incorporation of Fe 0 into the Au particles. Modification of the Au/Fe 2O 3 perimeter and appearance of Fe 0 co-catalyst and Fe–Au ensembles on the surface increased the hydrogenation activity but decreased the selectivity of ethylene formation.

Fractal‐like behaviour of the BCC/FCC phase separation in the iron‐gold alloys

Iron-gold alloys with compositions Fe(70)Au(30) and Fe(50)Au(50) were prepared by arc melting. The alloys were investigated by means of the high-resolution scanning electron microscopy (SEM-FEG) in the as-cast state and upon annealing in two steps, i.e. at 250 degrees C for 24 h and subsequently at 500 degrees C for 48 h. The alloys were composed of two phases, i.e. a BCC phase rich in iron and a FCC phase rich in gold. The single-phase regions have equivalent diameter of about 50 nm. SEM images show self-similar structure for the spatial distribution of the above phases on scales ranging from about 1 mm till about 100 nm. The roughness of the images has been used to estimate a fractal dimension of the phase mixture. For larger scales of the as-cast samples one finds fractal dimension of about 1.7 for Fe(70)Au(30) composition, i.e. very close to the dimension of typical diffusion limited aggregation (DLA) fractals. For annealed samples, dimension 1.1 was found.

Laser ablation ICP-MS titanite U–Th–Pb dating of hydrothermal ore deposits: A case study of the Tonglushan Cu–Fe–Au skarn deposit, SE Hubei Province, China

Titanite from the Tonglushan Cu–Fe–Au skarn deposit, Daye district, eastern China, has been successfully dated by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Hydrothermal titanite from both skarn ores and calcite veins cutting the ore bodies are characterized by having much lower REE and Th/U and Lu/Hf ratios compared to their magmatic equivalents from the ore-related Yangxin quartz diorite intrusion and a late-stage albitite dike. Titanite from the Yangxin quartz diorite and an albitite dike, which intrudes both the quartz diorite intrusion and ore bodies, yield weighted mean 206Pb/ 238U ages of 136.0 ± 1.5 Ma and 120.6 ± 2.3 Ma (2σ), respectively, in agreement within analytical uncertainty to their 208Pb/ 232Th ages. In situ analysis of epidote-enclosed hydrothermal titanite in thin sections of a skarn ore sample yields a mean 206Pb/ 238U age of 135.9 ± 1.3 Ma and 208Pb/ 232Th age of 138.2 ± 4.5 Ma, whereas titanite in calcite from a calcite-dominated vein cross-cutting the skarn ore body has consistent 206Pb/ 238U and 208Pb/ 232Th ages of ca. 121 Ma. The data thus reveal two independent hydrothermal events. The earlier event was responsible for the known Cu–Fe–Au skarn mineralization at Tonglushan and throughout the Daye district, and was caused by coeval magmatism that has resulted in the emplacement of the Yangxin quartz diorite. The later event, previously unrecognized, was associated with a second magmatic pulse as represented by the albitite dikes, and provides potential for discovering new mineral deposits at Tonglushan and possibly over the Daye district. This study represents the first direct dating of skarn deposits using titanite U–Th–Pb geochronometer and signifies the utilization of titanite for precise dating of hydrothermal ore formation.

Structure and phonon density of states of supported size-selected F57eAu nanoclusters: A nuclear resonant inelastic x-ray scattering study

We have measured the phonon density of states (PDOS) of isolated bcc and fcc FexAu1−x alloy nanoclusters (NCs) by nuclear resonant inelastic x-ray scattering. Drastic deviations were observed with respect to the PDOS of bulk Fe–Au alloys. Important information on the structure and thermodynamic properties of these NCs was obtained.

Fabrication of single crystalline gold nanobelts

Well dispersed, single crystalline gold nanobelts, with unique {110} crystallographic facets, were synthesized by a combined method consisting of directional solid-state transformation of an Fe–Au eutectoid and a selective phase dissolution without the presence of any surfactant. They have an average thickness of 25–30 nm, a width of 200–250 nm, and an average length of 20 µm, exhibiting thus extremely high aspect ratios of more than 1500. The obtained gold nanobelts were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectrometry. The well-dispersed gold nanobelts can be selectively assembled onto substrates which have a significant potential for novel electrodes with a large effective surface area and a selective crystal orientation of {110}, less common for gold.

Structural characterisation of gold nanowire arrays

This study is devoted to a thorough crystallographic and microstructural characterisation of gold nanowire arrays. The nanostructures were produced by directional solid-state decomposition of the Fe–Au eutectoid. The system structure and microstructure were investigated using differential thermal analysis (DTA), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM) and scanning Auger electron microscopy (SAEM). The most relevant sample features, with particular attention to the microstructure evolution, morphology and crystallography of the gold nanoarrays, are critically discussed. Gold nanofibres exhibit a faceted morphology with an average width of 20 nm, length of 100 nm and inter-wire distance of 250 nm. HRTEM analysis revealed that the obtained nanostructures are single crystalline and that the fibre-matrix crystallographic orientation relationship is of the Nishiyama–Wassermann type.

Preparation of multilayer targets for g-factor measurement of rotational levels

The three-layer-sandwich targets of 58,60Ni–Fe–Cu, 11B–Fe–Cu and 67 , 68,70Zn–Fe–Au have been prepared for g-factor measurement of rotational levels. The ferromagnetic Fe middle layers of 1.2–1.5 mg/cm 2 Fe have been made by rolling interrupted by annealing against hardening. Thick recoil stopper layers (5–12 mg/cm 2) of Cu and Au on one side of Fe foils have been fabricated by vacuum evaporation. Isotopic Zn, B and Ni layers of 150–400 μg/cm 2 have been deposited on the opposite side of the Fe foil by electron beam evaporation and focused ion beam sputtering, respectively. For better homogeneity the substrates were rotated.

Geogene and anthropogenic controls on the mineralogy and geochemistry of modern alluvial–(fluvial) gold placer deposits in man-made landscapes in France, Switzerland and Germany

Five study areas in the Cévennes, France, the Gotthard Massif, Switzerland, and from the western edge of the Bohemian Massif, Germany, have been selected for an investigation of the natural and human impacts on modern alluvial–(fluvial) gold placer deposits. The current investigation involved the study of grain-related parameters such as morphology, grain size and accessory minerals in gold aggregates in context with a detailed analysis of heavy and light minerals as well as heavy artifacts in the mineral assemblage of the placer deposits. To provide a sound data base, all sampling sites have been selected from areas sharing the same geotectonic and lithological settings. The modern placers are located in the extra-Alpine and Alpine parts of the Moldanubian Zone of the Variscides and they are characterized by a bedrock geology made up of metapsammopelitic rocks with some basic intercalations that were intruded by late Variscan granites. The combination of grain-related and mineral-related parameters in modern gold placer deposits is an effective tool to single out the natural impact (definition of the placer-type, provenance, chemical and mechanical reworking) and human impact (plumbing residues, ceramic goods, automobile devices, Pb–Fe–Au slags and mining residues), which may be of relevance for exploration by providing pathfinder elements or of relevance for the cultural history of the study area in terms of metallurgy and manufacturing. The placer deposits cover the whole range from pure alluvial via reworked alluvial to mixed-type alluvial–fluvial placer deposits (for definition see Introduction). Zirconium is a geomorphic marker element or indicator of the slope gradient of the drainage system. In course of lateritization chemical redeposition of gold that occurred during the Cretaceous and Tertiary (Paleogene and Neogene) times (parautochthonous) does not completely eradicate the characteristics of the primary source of gold. The mechanical reworking with long distance transport in alluvial depositional environments of different flow regimes however, makes attempts to trace the gold back to its source difficult because the intergrowth of gold aggregates with its marker minerals was destroyed by this mechanical transfer. Relics of lateritization in the placer gold assemblage may be deduced from fineness vs. grain size distributions and Fe–Al oxide/hydroxides as well as phyllosilicates intimately intergrown with gold aggregates. Stolzite and gold amalgam are positive indicators for gold enrichment in the catchment area of the placer-bearing drainage system. Lead, iron, tin and antimony are suitable tracers for the human impacts on placer deposits and may assist in characterizing the metallurgical, mining and manufacturing processes through time in a certain area. The results of this study allow to evaluate the gold provenance, the paleoclimatological and palaeogeomorphological controls on modern gold placer formations, the placer-type (alluvial, reworked alluvial, alluvial–fluvial) and the anthropogenic control relevant to exploration of placers. The latter also may provide an insight into the technical history of a region.

Genesis of gold and silver sulfides at the Ulakhan deposit ( northeastern Russia)

Geology and mineralogy of the Ulakhan Au-Ag epithermal deposit (northeastern Russia, Magadan Region) are considered. A four-stage scheme of mineral formation sequence is proposed. Concentrations of Au and Ag in minerals of early and late parageneses were determined. It has been established that uytenbogaardtite is associated with native gold and hypergenesis stage minerals — goethite, hydrogoethite, or limonite replacing pyrite. The compositions of uytenbogaardtite (Ag 3AuS 2), acanthite (Ag 2S), and native gold were studied. The composition of the Ulakhan uytenbogaardtite is compared with those of Au and Ag sulfides from other deposits. Thermodynamic calculations in the system H 2O–Fe–Au–Ag–S–C–Na–Cl were carried out, which simulate the interaction of native gold and silver with O 2- and CO 2-saturated surface waters (carbonaceous, sulfide-carbonaceous, and chloride-sodium-carbonaceous) in the presence and absence of acanthite and pyrite at 25 °C and 1 bar. In closed pyrite-including systems, native silver and kustelite are replaced by acanthite; electrum, by uytenbogaardtite, acanthite, and pure gold; and native gold with a fineness of 700–900‰, by pure gold and uytenbogaardtite. Under the interaction with surface waters in the presence of Ag 2S and pyrite, Au-Ag alloys form equilibrium assemblages with petrovskaite or uytenbogaardtite and pure gold. The calculation results confirmed that Au and Ag sulfides can form after native gold in systems involving sulfide-carbon dioxide solutions (H 2Saq > 10 –4 m). The modeling results support the possible formation of uytenbogaardtite and petrovskaite with the participation of native gold in the hypergenesis zone of epithermal Au-Ag deposits during the oxidation of Au(Ag)-containing pyrite, acanthite, or other sulfides.

Origin of the Tongshankou porphyry–skarn Cu–Mo deposit, eastern Yangtze craton, Eastern China: geochronological, geochemical, and Sr–Nd–Hf isotopic constraints

The Tongshankou Cu–Mo deposit, located in the westernmost Daye district of the Late Mesozoic Metallogenic Belt along the Middle-Lower reaches of the Yangtze River, eastern China, consists mainly of porphyry and skarn ores hosted in the Tongshankou granodiorite and along the contact with the Lower Triassic marine carbonates, respectively. Sensitive high-resolution ion microprobe zircon U–Pb dating constrains the crystallization of the granodiorite at 140.6 ± 2.4 Ma (1σ). Six molybdenite samples from the porphyry ores yield Re–Os isochron age of 143.8 ± 2.6 Ma (2σ), while a phlogopite sample from the skarn ores yields an 40Ar/39Ar plateau age of 143.0 ± 0.3 Ma and an isochron age of 143.8 ± 0.8 Ma (2σ), indicating an earliest Cretaceous mineralization event. The Tongshankou granodiorite has geochemical features resembling slab-derived adakites, such as high Sr (740–1,300 ppm) and enrichment in light rare earth elements (REE), low Sc (<10 ppm), Y (<13.3 ppm), and depletion in heavy REE (<1.2 ppm Yb), and resultant high Sr/Y (60–92) and La/Yb (26–75) ratios. However, they differ from typical subduction-related adakites by high K, low MgO and Mg#, and radiogenic Sr–Nd–Hf isotopic compositions, with (87Sr/86Sr)t = 0.7062–0.7067, ɛNd(t) = −4.37 to −4.63, (176Hf/177Hf)t = 0.282469–0.282590, and ɛHf(t) = −3.3 to −7.6. The geochemical and isotopic data, coupled with geological analysis, indicate that the Tongshankou granodiorite was most likely generated by partial melting of enriched lithospheric mantle that was previously metasomitized by slab melts related to an ancient subduction system. Magmas derived from such a source could have acquired a high oxidation state, as indicated by the assemblage of quartz–magnetite–titanite–amphibole–Mg-rich biotite in the Tongshankou granodiorite and the compositions of magmatic biotite that fall in the field between the NiNiO and magnetite–hematite buffers in the Fe3+–Fe2+–Mg diagram. Sulfur would have been present as sulfates in such highly oxidized magmas, so that chalcophile elements Cu and Mo were retained as incompatible elements in the melt, contributing to subsequent mineralization. A compilation of existing data reveals that porphyry and porphyry-related Cu–Fe–Au–Mo mineralization from Daye and other districts of the Metallogenic Belt along the Middle-Lower reaches of the Yangtze River took place coevally in the Early Cretaceous and was related to an intracontinental extensional environment, distinctly different from the arc-compressive setting of the Cenozoic age that has been responsible for the emplacement of most porphyry Cu deposits of the Pacific Rim.

New Hybrid Semiconductor Materials Based on Viologen Salts of Bimetallic Fe–Pt and Fe–Au Carbonyl Clusters: First Structural Characterization of the Diradical π‐Dimer of the Diethylviologen Monocation and EPR Evidence of its Triplet State

The synthesis, structure, spectroscopic characterization and electrical resistivity of the [EtV](2)[Fe(4)Pt(CO)(16)], [EtV][Fe(3)Pt(3)(CO)(15)].THF, [EtV][Fe(4)Au(CO)(16)](2)2.THF (EtV=1,1'-diethyl-4,4'-bipyridilium cation) and [NEt(4)](2)[Fe(4)Au(CO)(16)] is reported. The crystal structure of [EtV](2)[Fe(4)Pt(CO)(16)] is based on infinite stacks of [(EtV)(*+)](2) pi-dimers rotated by 90 degrees and isolated [Fe(4)Pt(CO)(16)](2-) ions. Within each pi-dimer, the [EtV](*+) radical ions are perfectly eclipsed and the distance between their mean planes is 3.275 A. The EPR spectrum of the solid material at room temperature clearly indicates the presence of a significantly populated triplet state of the pi-dimer, by showing signals both at Deltam=1 and Deltam=2. The solid-state structure of [EtV][Fe(3)Pt(3)(CO)(15)].THF is based on the ionic packing of [EtV](2+) and [Fe(3)Pt(3)(CO)(15)](2-) ions, inferred from a comparison of their molecular parameters with literature data. Significant electron transfer could have been expected to give [EtV](*+)[Fe(3)Pt(3)(CO)(15)](*-) on the basis of their formal redox potentials. In spite of their different stoichiometries, the structures of [EtV][Fe(4)Au(CO)(16)](2).2 THF and [NEt(4)](2)[Fe(4)Au(CO)(16)] both contain an isomer of the monoanion [Fe(4)Au(CO)(16)](-) in solution (previously characterized in the solid state as a [NMe(3)CH(2)Ph](2)[Fe(4)Au(CO)(16)]Cl mixed salt). Resistivity measurements on pellets of powdered samples of the above compounds indicate that their tetrasubstituted ammonium salts, and complex [EtV][Fe(4)Au(CO)(16)](2)2.THF, largely behave as insulators. However, the [EtV](2)[Fe(4)Pt(CO)(16)] and [EtV][Fe(3)Pt(3)(CO)(15)].THF samples respectively display resistivities 3 and 4 orders of magnitude less than those of their corresponding ammonium salts and could be classified as semiconductor materials.

Structure, morphology and magnetic properties of Fe–Au core-shell nanoparticles

The aim of the present work is the investigation of the core-shell Fe@Au nanoparticles obtained by the inverse micelles method. Also hybrid structures between Fe@Au nanoparticles and the well-known conducting polymer polypyrrole (PPY) were obtained and investigated. The properties of the composites were investigated by TEM, HRTEM, X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS) and magnetization measurements. The TEM, HRTEM measurements show that two categories of core-shell nanoparticles with mean diameters of 5 nm and 25 nm, respectively, are formed. The XPS investigations of the core-shell Fe@Au nanoparticles indicate that besides Fe 0 inside the cores, small amounts of Fe II,III, located onto the gold surface ,were also formed during the samples preparation. The magnetization of the investigated nanocomposites measured versus increasing and decreasing magnetic field shows no hysteresis loop, this behavior being consistent with a superparamagnetic behavior. The behavior of the SQUID magnetization vs. temperature under field cooled (FC) and zero field cooled (ZFC) at 0.1 T magnetic field for Fe@Au nanoparticles confirmed the existence of superparamagnetism. The superparamagnetic model was used to fit the experimental magnetization vs. applied magnetic field as it was measured by SQUID up to 5 T.

Iron–Gold Barcode Nanowires

Nanowires are a focus of research interests as one-dimensional nanosystems and promise exciting applications in nanotechnology, ranging from nanoelectronic devices to cell separation and magnetic labeling in biomedicine. Avariety of methods have been devised to prepare them from magnetic, semiconductor, inorganic, organic, polymer, metallic, and dielectric materials to provide nanowires with novel optical, electrical, catalytic, and magnetic properties. Multilayered or barcode arrangements of nanowires which incorporate different material components are a special case as a result of their spatial arraying, multiple functionalities, and enhanced properties in comparison to those of their single-component counterparts. For instance, Co–Cu barcode nanowires were explored for their high magnetoresistance compared to that of the well-studied thin films, 17] while the coding of magnetic and optical properties in a single wire was targeted for the separation, detection, and transport of cells. Interested in the transport properties and potential applications of nanowires in nanodevices and biomedicine, we have investigated magnetic nanowires by electrodeposition. For biomedical purposes, however, two issues have to be addressed for the implementation of such nanowires, namely surface modification and biocompatibility. In this respect, the synthesis of iron–gold (Fe–Au) nanowires is appealing not only in terms of magnetic properties but also with respect to biological compatibility. On one hand, iron is favored as it is unique in the field of magnetic materials owing to its high magnetization and physicochemical potentiality. It can be easily converted into oxides, which have been thoroughly studied in the form of magnetic nanoparticles in the biomedical field for their magnetic properties and exceptional biocompatibility. On the other hand, gold is a wellestablished material that displays attractive optical properties, biological compatibility, catalytic activity, and excellent surface effects. Thus, it was anticipated that the integration of these two materials into a one-dimensional barcode arrangement on the nanoscale would produce a new nanostructured material that retains the optical and magnetic properties of the respective components, offering synergistically enhanced performance and functionalities which go beyond those of the individual components. Herein, we report the synthesis and characterization of such a kind of multifunctional magnetic–optical Fe–Au barcode nanostructures, that is, nanowires consisting of alternative Fe magnetic and Au optical segments. The Fe–Au barcode nanowires were constructed using anodic alumina oxide (AAO) templates by pulse electrodeposition thus forming iron and gold segments alternatively in a single bath under desired pulse current densities (e.g. 10 mAcm 2 and 0.5 mAcm ) with regulated pulse durations to control the respective segmental lengths (see Experimental Section). The selection of a current density to electrodeposit Fe or Au was based on the evaluation of the composition versus current density profile (Figure 1a), which was acquired from the analysis of the samples each obtained at a given constant current density, by inductively coupled

Positive correlation between the magnetic moment of Fe and atomic volume in the binary Fe–(Cu, Ag, Au) alloys revealed by ab initio calculations

Based on the projector-augmented wave method, ab initio calculations were performed for more than 60 binary metastable Fe–Cu, Fe–Ag and Fe–Au compounds. It was found that the magnetic moment of Fe can be greatly enhanced and could even reach a value beyond 3 μ B in these metastable alloys. A distinct positive correlation between the magnetic moment of Fe and atomic volume was observed in these ferromagnetic alloys, suggesting Fe atoms locating in large-sized structures may possess high magnetic moments.

Carbon encapsulated magnetic nanoparticles produced by hydrothermal reaction

Carbon encapsulated magnetic nanoparticles (CEMNs) were synthesized by heating an aqueous glucose solution containing Fe–Au (Au coated Fe nanoparticles) nanoparticles at 160–180 °C for 2 h. This novel hydrothermal approach is not only simple but also provides the surface of CEMNs with functional groups like OH. The formation of carbon encapsulated magnetic nanoparticles was not favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by H 2O during the reaction and, therefore, the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance. TEM, XRD, XPS and VSM measurments characterized that they were uniform carbon spheres containing some embedded Fe–Au nanoparticles, with a saturation of 14.6 emu/g and the size of the typical product is ∼350 nm.

Re–Os molybdenite and Ar–Ar phlogopite dating of Cu–Fe–Au–Mo (W) deposits in southeastern Hubei, China

The Cu–Fe–Au–Mo (W) deposits in southeastern Hubei are an important component of the Middle–Lower Yangtze River metallogenic belt. Molybdenite from the Fengshandong Cu- (Mo), Ruanjiawan W–Cu- (Mo), Qianjiawan Cu–Au, Tongshankou Cu–Mo and Tonglushan Cu- (Fe) deposits yielded Re–Os ages of 144.0 ± 2.1 Ma, 143.6 ± 1.7 Ma, 137.7 ± 1.7 Ma, 142.3 ± 1.8–143.7 ± 1.8 Ma and 137.8 ± 1.7–138.1 ± 1.8 Ma, respectively. Phlogopite from the Tieshan Fe- (Cu) deposit yielded an Ar–Ar age of 140.9 ± 1.2 Ma. These data and other published isotopic ages (Re–Os molybdenite and Ar–Ar mica ages) for the Cu–Fe–Au–Mo (W) deposits in the Middle–Lower Yangtze River metallogenic belt show that Cu–Fe–Au–Mo (W) mineralisation in the Tongling, Anqing, Jiurui and Edong ore districts developed in a narrow time span between 135.5 and 144.9 Ma, reflecting an important regional metallogenic event. An integrated study of available petrological and geochronological data, together with relationships to magmatism and the regional geodynamic framework, indicate that the Cu–Fe–Au–Mo (W) mineralisation in the Middle–Lower Yangtze River belt occurred during a regime of lithospheric extension. This extension is probably related to Late Mesozoic processes of lower crustal delamination and lithospheric thinning in East China.

CO2-rich fluid inclusions with chalcopyrite daughter mineral from the Fenghuangshan Cu–Fe–Au deposit, China: implications for metal transport in vapor

CO2-rich fluid inclusions containing opaque mineral crystals were found in the Fenghuangshan skarn-porphyry Cu–Fe–Au deposit in Tongling, Anhui, China. These inclusions show variable CO2 contents and are accompanied by aqueous inclusions, both occurring as secondary inclusions in quartz and being locally associated with chalcopyrite mineralization. Laser Raman microspectroscopic analyses confirm the predominance of CO2 in the vapor and the presence of H2S as high as 8 mol%, and identify the opaque mineral with yellow reflectance color in the inclusions as chalcopyrite. More than half of the CO2-bearing inclusions contains chalcopyrite, whereas few of the associated aqueous inclusions do so. The chalcopyrite, occupying less than 1% (volume) of the inclusions, is interpreted to be a daughter mineral, and calculated Cu concentrations in the inclusions range from 0.1 to 3.4 wt%. Copper is inferred to have been transported in CO2-dominated fluids as HS− complexes. The occurrence of chalcopyrite daughter crystals in CO2-rich fluid inclusions indicates that CO2-rich vapor has the capacity of transporting large amounts of Cu, and possibly Au. This finding has significant implications for metal transport and mineralization in hydrothermal systems enriched in CO2, such as orogenic-type and granitic intrusion-related gold deposits.