Sn Deposits Research Articles

Metallogeny and Mineralization Potential of the Bazman Granitoids, SE Iran

AbstractThe Mesozoic Bazman granitoids are located in Sistan and Baluchestan province, southeastern Iran. Geology of the study area consists of Carboniferous shale, sandstone, and limestone and Permian siltstone, shale, sandstone, limestone, and dolomite that were intruded by the Bazman granitoids. These granitoids include various phases of granite, granodiorite, quartz‐monzodiorite, monzodiorite, diorite, and gabbro. They are metaluminous to slightly peraluminous, reduced, calc‐alkaline and I‐type, and display geochemical characteristics of continental margin (ensialic) granitoids. In this paper, field, petrography, and geochemical data were used to discriminate the Bazman granitoids either as productive or barren granitoids. Although there are a few skarn‐related mineral occurrences adjacent to the Bazman granitoids, most exposed intrusions are not hydrothermally altered and mineralized. Rb/Sr, Zr/Hf, and K/Rb ratios indicate that the granitic magmas that formed most of the Bazman granitoids indicate that they are moderately evolved and have generally not undergone post‐magmatic hydrothermal activity. The Sm/Eu and Rb/Ba ratios and the concentrations of Rb, Ba, and Sr within the aforementioned granitoids show that the rocks are similar to the averages of granitoids devoid of Li, Be, U, Sn, W, and Ta deposits. The I‐type arc characteristics and other geochemical features of the Bazman granitoids show that they are not typical of parental magmas to Sn, W, Mo, and Zn mineralization, but are mainly fertile for Cu and Fe (Au) skarn‐related granitoids.

A review of developments in the electrodeposition of tin-copper alloys

The deposition of Sn–Cu binary alloys, mainly from aqueous electrolytes, is considered. The importance of tin–copper electrodeposits is summarised and the scope for plating them is highlighted. Sn–Cu (bronze) deposits are important in corrosion protection, decorative finishes, electronics and tribology. The past 20 years have seen a series of developments in the science and technology of bronze plating, including nanostructured deposits, environmentally friendly baths, such as methanesulfonic acid ones, and more ambitious coatings including multi-layers and composites. Among non-aqueous baths, room temperature ionic liquid electrolytes have received increasing attention. Our ability to realise controlled deposit morphology, composition and structure has been improved by newer electrolytes, improved electrolyte additives and pulse plating. The diversity of Sn–Cu deposit applications has extended to lithium batteries by newer layer structures such as composites, multi-layers and nanostructures), electrical control and relative bath/electrode movement. Electrochemical aspects of modern tin and bronze alloy deposition are illustrated by data from the authors' laboratory and elsewhere, which highlights the use of methanesulfonic acid electrolytes in tin alloy deposition due to their versatility and lack of environmental impact. A wide range of deposit composition, colour and surface finish are possible using suitable addition agents and by control of electrolyte flow and operating conditions. This review focuses on electrochemical voltammetry techniques together with morphological information from SEM imaging. Subject areas deserving further research and development are identified.

Hematite Surface Activation by Chemical Addition of Tin Oxide Layer.

In this study, the effect of tin (Sn(4+) ) modification on the surface of hematite electrodes synthesized by an aqueous solution route at different times (2, 5, 10, 18, and 24 h) is investigated. As confirmed from X-ray diffraction results, the as-synthesized electrode exhibits an oxyhydroxide phase, which is converted into a pure hematite phase after being subjected to additional thermal treatment at 750 °C for 30 min. The tin-modified hematite electrode is prepared by depositing a solution of Sn(4+) precursor on the as-synthesized electrode, followed by thermal treatment under the same abovementioned conditions. This modification results in an enhancement of the photocurrent response for all hematite electrodes investigated and attains the highest values of around 1.62 and 2.3 mA cm(-2) at 1.23 and 1.4 V versus RHE, respectively, for electrodes obtained in short synthesis times (2 h). Contact angle measurements suggest that the deposition of Sn(4+) on the hematite electrode provides a more hydrophilic surface, which favors a chemical reaction at the interface between the electrode and electrolyte. This result generates new perspectives for understanding the deposition of Sn(4+) on the hematite electrode surface, which is in contrast with several studies previously reported; these studies state that the enhancement in photocurrent density is related to either the induction of an increased donor charge density or shift in the flat-band potential, which favors charge separation.

Origin of the granites and related Sn and Pb-Zn polymetallic ore deposits in the Pengshan district, Jiangxi Province, South China: constraints from geochronology, geochemistry, mineral chemistry, and Sr-Nd-Hf-Pb-S isotopes

The Pengshan Sn and Pb-Zn polymetallic deposits are located in the south margin of the Jiujiang-Ruichang (Jiurui) district of the Middle-Lower Yangtze River Metallogenic Belt in South China. Four large deposits include Huangjinwa, Zengjialong, Jianfengpo, and Zhangshiba, the former three are Sn-dominant deposits which occur as stratiform orebodies in the contact zones of the Pengshan granites and within the country rock strata, whereas Zhangshiba consists of stratiform Pb-Zn orebodies within the Precambrian metasedimentary strata. In this study, we present results on zircon U-Pb ages, major and trace elements, and mineral chemistry as well as Sr-Nd-Hf isotope data of the granites, Pb and S isotopes of both the Sn-dominant and Pb-Zn dominant deposits, and U-Pb dating of cassiterite from the Pengshan district. SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the Pengshan granites were emplaced in the Early Cretaceous (129–128 Ma), which is in good agreement with the U-Pb dating (130–128 Ma) of cassiterite from the Jianfengpo Sn deposit. The Pengshan granites consist mainly of weakly peraluminous highly fractionated I-type affinity granitic rocks. Detailed elemental and isotopic data suggest that the granites formed by partial melting of Mesoproterozoic metamorphic basement materials with minor input of mantle-derived melts. The mineral chemistry of biotite demonstrates that the Pengshan granitic magma had a low oxygen fugacity, thereby precluding the tin dominantly partitioning into the rock-forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages. Sulfur isotopes show a relatively heavy sulfur isotopic composition from 5.8 to 17.6 ‰, and no difference for sulfur isotopes between the Sn deposits (5.8–13.4 ‰, Huangjinwa, Zengjialong, Jianfengpo) and the Pb-Zn deposit (mostly 7.1–13.0 ‰, except for one 17.6 ‰, Zhangshiba). The sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher δ34S values of 22.7–28.7 ‰. Lead isotopes indicate that the granites have higher 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios than the host Precambrian metasedimentary rocks, and the sulfide minerals from the orebodies fall in between them. Again, there is no difference for Pb isotopes between the Sn deposits (Huangjinwa, Zengjialong, Jianfengpo) and the Zhangshiba Pb-Zn deposit. The coincidence in S and Pb isotope compositions for Sn and Pb-Zn deposits suggests that similar sources for these mineralization, possibly derived from a mixed source of the granitic magmas and the Precambrian metasedimentary rocks. These data therefore favor of a magmatic-hydrothermal origin for both the Sn and Pb-Zn polymetallic mineralization in the Pengshan district.

Identification of Fluid Inclusion Solid Phases Using A Focused Ion Beam Scanning Electron Microscope With Energy Dispersive Spectroscopy: Implications For Interpreting Microthermometric Data and Composition of Fluids In SN (-W-Mo) Deposits

Abstract A feature of many granite-related mineral deposits is the presence of highly saline fluid inclusions that contain abundant daughter minerals, the identity and chemistry of which hold important information for the interpretation of the chemistry of mineralizing fluids in such environments. A focused ion beam (FIB) coupled with a scanning electron microscope (SEM) and energy-dispersive spectroscope (EDS) was used to identify daughter minerals within such fluid inclusions in fluorite from the Mount Pleasant Sn (-W-Mo-In) deposits, New Brunswick, Canada. The technique can be used to obtain quantitative compositional information for solid phases in fluid inclusions for which the optical properties have previously been studied, but whose identification remains equivocal. In addition, for solid-rich fluid inclusions, this technique enables identification of solids that are obscured by other solids and are not readily visible using optical microscopy. Methods such as Raman spectroscopy and SEM-EDS analysis of broken surfaces have limited success in mineral identification in these inclusions due to strong fluorescence in fluorite and an inability to correlate solids with their optical properties, respectively. The FIB-EDS analyses of the daughter minerals and precipitates formed by evaporation of the liquid in the inclusions show that the complex inclusions from Mount Pleasant contain brines with high concentrations of Na, Fe, K, Mn, Pb, Zn, and Cl; daughter minerals comprise halite and a variety of Fe-K(-Mn) chloride hydrates, and less frequently, Pb chlorides and Sn-bearing phases. The precipitates contain similar phases, although in general they are more K-rich than the daughter minerals. Unequivocal identification of most solid phases was not possible due to inaccuracies inherent in the FIB-EDS chemical analyses and a lack of Raman spectra for many K-Fe-Mn chloride hydrate minerals. Our data indicate that square (“cubic”) solids in such inclusions are not always halite, and that misidentification of halite could result in erroneous salinity estimates, which could lead to inaccurate interpretations of fluid composition using techniques such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).

Late Cretaceous magmatism and related metallogeny in the Tengchong area: Evidence from geochronological, isotopic and geochemical data from the Xiaolonghe Sn deposit, western Yunnan, China

Xiaolonghe is a poorly studied greisen-type tin deposit that is hosted by biotite granite in the western Yunnan tin belt. The mineralisation-related metaluminous and weak peraluminous granite is characterised by high Si, Al and K and low Mg, Fe and Ca, with an average A/CNK of 1.02. The granite is enriched in LILEs (K and Rb), LREEs and HFSEs (Zr, Hf, Th, U and Ce) and depleted in Ba, Nb, Sr, P, and Ti, with zircon εHf(t)=−10.8 to −7.5 (TDM2=1.61–1.82Ga). These characteristics indicate that the magma was generated by the partial melting of a thickened ancient crust. LA-ICP-MS U–Pb dating of igneous zircon and hydrothermal cassiterite yield ages of 71.4±0.4Ma and 71.6±4.8Ma, respectively. The igneous biotite and hydrothermal muscovite samples show Ar–Ar plateau ages of 72.3±0.4Ma and 70.6±0.2Ma, respectively. The close temporal relationship between the igneous emplacement and hydrothermal activity suggests that the tin mineralisation was closely linked to the igneous emplacement. The δ18O and δD values for the deposit range from +3.11‰ to −4.5‰ and from −127.3‰ to −94.7‰, respectively. The hydrothermal calcite C and O isotopic data show a wide range of δ13CPDB values from −5.7‰ to −4.4‰, and the δ18OSMOW values range from +1.4‰ to +11.2‰. The δ34SV-CDT data range from +4.8‰ to +8.9‰ for pyrite, and the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios range from 18.708 to 18.760, from 15.728 to 15.754 and from 39.237 to 39.341, respectively. The stable isotopic (C–H–O–S–Pb) compositions are all similar to those of magmatic and mantle-derived fluids, which indicate that the ore-forming fluids and materials were mainly derived from magmatic sources that were accompanied by meteoric water. The tin mineralisation in the Xiaolonghe district was closely associated with the Late Cretaceous crustal-melting S-type granites that formed during the subduction of the Neo-Tethys oceanic lithosphere. Combined with the tin deposits in the Southeast Asian tin belt, Tengchong block and Central Lhasa, we interpreted that a giant intermittent tin mineralisation belt should be present along the Asian Neo-Tethys margin.

Sputtering Deposition of Sn–Mo-Based Composite Anode for Thin-Film Li-Ion Batteries

The role of electrochemically inactive molybdenum in alleviating the anomalous volume expansion of tin anode upon charge–discharge cycling has been investigated. Tin–molybdenum thin-film composite anodes for Li-ion batteries were prepared using a direct-current sputtering method from a tin metal target incorporating molybdenum element. Results of structural and compositional analyses confirmed the presence of tin and molybdenum. The elemental ratio obtained from energy-dispersive x-ray spectroscopy confirmed the feasibility of tailoring the thin-film composition by varying the ratio of metallic elements present in the sputtering target. Scanning electron micrographs of the samples revealed the occurrence of flower-like open morphology with Mo inclusion in a Sn matrix. The gravimetric discharge capacity for pure Sn, Sn-rich, and Mo-rich samples was 733 mAh g−1, 572 mAh g−1, and 439 mAh g−1, respectively, with capacity retention after 50 cycles of 22%, 61%, and 74%, respectively. Mo inclusion reduced the surface resistivity of the Sn anode after the initial charge–discharge cycle. The charge-transfer resistance after the first cycle for pure Sn, Sn-rich, and Mo-rich samples was 17.395 Ω, 5.345 Ω, and 2.865 Ω, respectively. The lithium-ion diffusion coefficient also increased from 8.68 × 10−8 cm2S−1 for the pure Sn sample to 2.98 × 10−5 cm2S−1 for the Mo-rich sample.

Zircon U–Pb, molybdenite Re–Os and muscovite Ar–Ar isotopic dating of the Xitian W–Sn polymetallic deposit, eastern Hunan Province, South China and its geological significance

The Xitian tungsten–tin (W–Sn) polymetallic deposit, located in eastern Hunan Province, South China, is a recently explored region containing one of the largest W–Sn deposits in the Nanling W–Sn metallogenic province. The mineral zones in this deposit comprise skarn, greisen, structurally altered rock and quartz-vein types. The deposit is mainly hosted by Devonian dolomitic limestone at the contact with the Xitian granite complex. The Xitian granite complex consists of Indosinian (Late Triassic, 230–215 Ma) and Yanshanian (Late Jurassic–Early Cretaceous, 165–141 Ma) granites. Zircons from two samples of the Xitian granite dated using laser ablation-inductively coupled mass spectrometer (LA-ICPMS) U–Pb analysis yielded two ages of 225.6±1.3 Ma and 151.8±1.4 Ma, representing the emplacement ages of two episodic intrusions of the Xitian granite complex. Molybdenites separated from ore-bearing quartz-veins yielded a Re–Os isochron age of 149.7±0.9 Ma, in excellent agreement with a weighted mean age of 150.3±0.5 Ma. Two samples of muscovites from ore-bearing greisens yielded 40Ar/39Ar plateau ages of 149.5±1.5 Ma and 149.4±1.5 Ma, respectively. These isotopic ages obtained from hydrothermal minerals are slightly younger than the zircon U–Pb age of 151.8±1.4 Ma of the Yanshanian granite in the Xitian area, indicating that the W–Sn mineralization is genetically related to the Late Jurassic magmatism. The Xitian deposit is a good example of the Early Yanshanian regional W–Sn ore-forming event (160–150 Ma) in the Nanling region. The relatively high Re contents (8.7 to 44.0 ppm, average of 30.5 ppm) in molybdenites suggest a mixture of mantle and crustal sources in the genesis of the ore-forming fluids and melts. Based upon previous geochemical studies of Early Yanshanian granite and regional geology, we argue that the Xitian W–Sn polymetallic deposit can be attributed to back-arc lithosphere extension in the region, which was probably triggered by the break-off of the flat-slab of the Palae-Pacific plate beneath the lithosphere.

Geochronological and petrogeochemical constraints on the skarn deposits in Tongshanling ore district, southern Hunan Province: Implications for Jurassic Cu and W metallogenic events in South China

Southern Hunan Province, South China, is located in the central part of the Qin–Hang metallogenic belt and is characterized by abundant Cu–Pb–Zn and W–Sn polymetallic ore deposits. The Cu–Pb–Zn deposits are associated with Jurassic granodiorite porphyries whereas the W–Sn deposits occur within Jurassic granite porphyries. Here we present geochronologic and geochemical data for the Tongshanling Cu–(Mo)–Pb–Zn deposit and the Weijia W deposit in the district of Tongshanling, southern Hunan. Zircon U–Pb dating and molybdenite Re–Os geochronology indicate that the emplacement of the Tongshanling granodiorite porphyry and the associated Cu mineralization occurred at 162–160Ma, slightly earlier than the formation of the Xianglinpu granite porphyry and associated W mineralization at 159–158Ma. The Tongshanling granodiorite is high-K calc-alkaline, weakly peraluminous, and weakly fractionated with zircon εHf(t) values of −15.1 to −5.6. In contrast, the Xianglinpu granite is alkaline, peraluminous, and highly fractionated, with εHf(t) values of −9.5 to 0.9. Our data indicate that the Tongshanling granodiorite is relatively oxidized and was formed by the partial melting of Paleoproterozoic crustal material with inputs of mafic magma which was derived from a subduction-modified lithospheric mantle. In contrast, the Xianglinpu granite porphyry is relatively reduced and was formed by direct interaction between the crust and asthenospheric mantle. The difference in magma generation and tectonics is considered to have resulted in the different types of mineralization associated with these two intrusive bodies.

Studies on electrodeposition behavior of Sn–Bi alloys in plating baths modified by hydroquinone and gelatin

This work focuses on the investigation of the electrochemical behavior of Sn–Bi plating bath modified by two electrolyte additives, hydroquinone (HQ) and gelatin. Electrochemical studies were carried out by low sweep rate polarization scans, as well as cyclic voltammetry at different scan rates (1–40 mV/s). Polarization scans at sweep rate of 1 mV/s indicate that Bi deposits at about −25 to −45 mV while Sn deposits at about −410 to −420 mV in the plating bath without additives or with either one of the additives. The addition of HQ suppresses hydrogen evolution to more electronegative potentials, showing its adsorption capabilities. On the other hand, gelatin shifts the deposition potential of Bi and is suggested to have a mild complexing effect with Bi ions. The synergistic effect of both HQ and gelatin reduces the potential gap between Bi and Sn from 429 to 255 mV. Investigations on single metallic Sn and Bi plating baths at varying sweep rates reveal different behavior of Sn and Bi ions. The shifting and broadening of Bi cathodic peak potential upon HQ + gelatin addition suggest the formation of HQ–gelatin complex species. Surface morphology and composition analyses were conducted on electrodeposits from each plating bath. Near-eutectic Sn–Bi alloy was successfully electrodeposited from the plating bath modified by HQ + gelatin.

WITHDRAWN: Zircon U–Pb, molybdenite Re–Os and muscovite Ar–Ar isotopic dating of the Xitian W–Sn polymetallic deposit, eastern Hunan Province, South China and its geological significance

The Xitian tungsten–tin (W–Sn) polymetallic deposit, located in eastern Hunan Province, South China, is a recently explored region containing one of the largest W–Sn deposits in the Nanling W–Sn metallogenic province. The mineral zones in this deposit comprise skarn, greisen, structurally altered rock and quartz-vein types. The deposit is mainly hosted by Devonian dolomitic limestone at the contact with the Xitian granite complex. The Xitian granite complex consists of Indosinian (Late Triassic, 230–215 Ma) and Yanshanian (Late Jurassic–Early Cretaceous, 165–141 Ma) granites. Zircons from two samples of the Xitian granite dated using laser ablation-inductively coupled mass spectrometer (LA-ICPMS) U–Pb analysis yielded two ages of 225.6 ± 1.3 Ma and 151.8 ± 1.4 Ma, representing the emplacement ages of two episodic intrusions of the Xitian granite complex. Molybdenites separated from ore-bearing quartz-veins yielded a Re–Os isochron age of 149.7 ± 0.9 Ma, in excellent agreement with a weighted mean age of 150.3 ± 0.5 Ma. Two samples of muscovites from ore-bearing greisens yielded 40Ar/39Ar plateau ages of 149.5 ± 1.5 Ma and 149.4 ± 1.5 Ma, respectively. These isotopic ages obtained from hydrothermal minerals are slightly younger than the zircon U–Pb age of 151.8 ± 1.4 Ma of the Yanshanian granite in the Xitian area, indicating that the W–Sn mineralization is genetically related to the Late Jurassic magmatism. The Xitian deposit is a good example of the Early Yanshanian regional W–Sn ore-forming event (160–150 Ma) in the Nanling region. The relatively high Re contents (8.7 to 44.0 ppm, average of 30.5 ppm) in molybdenites suggest a mixture of mantle and crustal sources in the genesis of the ore-forming fluids and melts. Based upon previous geochemical studies of Early Yanshanian granite and regional geology, we argue that the Xitian W–Sn polymetallic deposit can be attributed to back-arc lithosphere extension in the region, which was probably triggered by the break-off of the flat-slab of the Palae-Pacific plate beneath the lithosphere.

Unexpected solution phase formation of hollow PtSn alloy nanoparticles from Sn deposition on Pt dendritic structures

Hollow nanoparticles with a high surface-to-volume ratio have found various applications in catalysis, sensors, and energy storage, and thus new synthetic routes to these structures are of great interest. One of the best-known synthetic routes to hollow nanostructures is the utilization of the Kirkendall effect, which, however, is not useful for systems with a slow diffusing-out core such as Pt and fast diffusing-in surface elements such as Sn. Herein, we report a counterintuitive formation of hollow PtSn nanostructures by reacting dendritic Pt nanostructures with Sn precursors.

Geological, geochemical, and geochronological characteristics of Caledonian W–Sn mineralization in the Baiganhu orefield, southeastern Xinjiang, China

The newly discovered large-scale Baiganhu W–Sn orefield, consisting of the Kekekaerde, Baiganhu, Bashierxi, and Awaer deposits, is located in Ruoqiang County, southeastern Xinjiang, China. These deposits comprise mainly three types of W–Sn mineralization: early-stage skarn-type, middle-stage greisen-type, and late-stage quartz-vein-type. In this study, we classified seven major vertical zones on the basis of petrographic characteristics, roughly from the bottom of the parental granitic intrusions upward, as (A) fresh syenogranite, (B) argillic alteration, (C) muscovite-dominated greisenization, (D) tourmaline-dominated greisenization, (E) marginal facies (including K-feldspar pegmatite and fine-grained granite), (F) aplitic apophysis, and (G1) skarn or (G2) infilled silification zones. According to the alteration–mineralization assemblages and cross-cutting relationships, five stages of mineralization are recognized in the orefield (I, skarn stage; II, greisen stage; III, quartz vein stage; IV, argillic alteration stage; and V, supergene stage), and reverse alteration zonation in the altered intrusion is also observed.The W–Sn deposits are spatially associated with syenogranite, which is part of the Caledonian Bashierxi magmatic series. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U–Pb dating of the syenogranite yields a weighted mean 206Pb/238U age of 413.6±2.4Ma (MSWD=0.36, n=30). Hydrothermal muscovite from three samples associated with W–Sn mineralization yields plateau 40Ar/39Ar ages of 411.7±2.6Ma (MSWD=0.21), 412.8±2.4Ma (MSWD=0.22), and 413.8±2.6Ma (MSWD=0.22), which is consistent with the zircon U–Pb age, thus indicating a temporal link between the emplacement of the syenogranite and the W–Sn mineralization. Our age data and previously published ages, along with geochemical data, for the granitoids in the Bashierxi magmatic series show a nearly contemporaneous evolution of A- and S-type granites, which were emplaced in a post-orogenic setting at ca. 432–413Ma. As compared with the A-type granites, the syenogranites with S-type affinities probably resulted from a lower degree of partial melting of metagreywackes, which was more likely to be enriched in the ore-forming elements W and Sn, as well as volatiles such as B and H2O. In addition, the syenogranites exhibit low oxidation states and underwent high degrees of factional crystallization, both of which favor post-magmatic W–Sn mineralization. We suggest that more attention should be given to buried syenogranites of S-type affinities during mineral exploration in this area, and that the proposed model of a vertical alteration zoning can act as a guide to the targeting of similar ore systems.

Re–Os Geochronology of Molybdenite from Yinyan Porphyry Sn Deposit in South China

AbstractThe Yinyan Sn deposit, one of the three typical porphyry Sn deposits in China, is located in the western Guangdong province of the Cathaysia Block. Rhenium and osmium isotopes of molybdenites from the Yinyan deposit were first used to constrain the age of mineralization. Rhenium concentrations in molybdenite samples range from 0.13 to 1.3 µg g−1, indicating a crustal source for the ore‐forming materials. The Re–Os dating yield model ages ranging from 78.1 to 79.52 Ma, with an average of 78.65 ± 0.98 Ma, and give an isochron age of 78.8 ± 2.6 Ma. Evidently, isochron age is consistent with model ages in the error within the allowable range, so we can constrain the precise age of Yinyan Sn deposit at the Late Cretaceous. Based on the geological history and spatial‐temporal distribution of the Sn deposits, it is proposed that the formation of Sn deposits in the Cathaysia Block were related to lithospheric extension that are associated with a change in the polarity of the subduction of the Paleo‐Pacific Plate from oblique subduction to parallel the eastern margin of the Eurasian Plate after 135 Ma.

Composition and evolution of accessory mineralization of Li–F granites in the Far East as indicators of their ore potential

The ore potential of Pacific Li–F granites is considered on the basis of original and published data on composition of these granites and related metasomatic rocks in the Badzhal (Amur region) and Kuiviveem–Pyrkakai (Chukchi Peninsula) ore districts. The accessory mineralization in rare-metal granites is compared with that in W–Sn deposits. The main features in evolution of magmatic and hydrothermal mineralization are pointed out. A conclusion on the similarity between mineralization of the zwitter–tourmalinite type and accessory minerals in Li–F granites is drawn. It is established that magmatic and hydrothermal types of mineralization belong to the same evolutionary sequence. Genetic links between Li–F granites and the large ore deposits in the East Asian tungsten–tin zone are suggested.

A Versatile Precursor System for Supercritical Fluid Electrodeposition of Main-Group Materials.

For the first time, a versatile electrolyte bath is described that can be used to electrodeposit a wide range of p-block elements from supercritical difluoromethane (scCH2 F2 ). The bath comprises the tetrabutylammonium chlorometallate complex of the element in an electrolyte of 50×10(-3) mol dm(-3) tetrabutylammonium chloride at 17.2 MPa and 358 K. Through the use of anionic ([GaCl4 ](-) , [InCl4 ](-) , [GeCl3 ](-) , [SnCl3 ](-) , [SbCl4 ](-) , and [BiCl4 ](-) ) and dianionic ([SeCl6 ](2-) and [TeCl6 ](2-) ) chlorometallate salts, the deposition of elemental Ga, In, Ge, Sn, Sb, Bi, Se, and Te is demonstrated. In all cases, with the exception of gallium, which is a liquid under the deposition conditions, the resulting deposits are characterised by SEM, energy-dispersive X-ray analysis, XRD and Raman spectroscopy. An advantage of this electrolyte system is that the reagents are all crystalline solids, reasonably easy to handle and not highly water or oxygen sensitive. The results presented herein significantly broaden the range of materials accessible by electrodeposition from supercritical fluid and open up the future possibility of utilising the full scope of these unique fluids to electrodeposit functional binary or ternary alloys and compounds of these elements.

Fractal analysis of geochemical landscapes using scaling noise model

Fractal/multifractal concepts have facilitated the description and analysis of complex geochemical data in both mineral exploration and environmental studies. Scaling (1/fβ) noise has been ubiquitously found in geosciences but lack in-depth studies for geochemical distribution pattern in mineral exploration. In the present paper, the 1/f scaling natures of geochemical landscapes are investigated using spectral method through geochemical samples in stream sediments from Nanling Range, China. The results show explicit differences in scaling exponent (β) between major elements and trace elements, between highly enriched elements (e.g., W, Sn, Mo and Bi) and relatively low enriched elements (e.g., Au, Ag and Cu), where β measures the strength of persistence (or the degree of roughness) of geochemical landscapes. Furthermore, fractal mapping of geochemical patterns (W and Sn element) is undertaken to reveal the spatial association between local fractal dimension and mineralization. The finding is that most of the W and Sn deposits in study area exhibit rough geochemical patterns with fractal dimension ranging from 2.3 and 2.7 (2.6≤β≤3.4). We proposed to recognize the complex geochemical anomalies containing both stochastic (irregular) and deterministic (regular) components from fractal noise perspective.

Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Method.

We have achieved significant improvements for the oxygen reduction reaction activity and durability with new SnO2-nanoislands/Pt3Co/C catalysts in 0.1 M HClO4, which were regulated by a strategic fabrication using a new selective electrochemical Sn deposition method. The nano-SnO2/Pt3Co/C catalysts with Pt/Sn = 4/1, 9/1, 11/1, and 15/1 were characterized by STEM-EDS, XRD, XRF, XPS, in situ XAFS, and electrochemical measurements to have a Pt3Co core/Pt skeleton-skin structure decorated with SnO2 nanoislands at the compressive Pt surface with the defects and dislocations. The high performances of nano-SnO2/Pt3Co/C originate from efficient electronic modification of the Pt skin surface (site 1) by both the Co of the Pt3Co core and surface nano-SnO2 and more from the unique property of the periphery sites of the SnO2 nanoislands at the compressive Pt skeleton-skin surface (more active site 2), which were much more active than expected from the d-band center values. The white line peak intensity of the nano-SnO2/Pt3Co/C revealed no hysteresis in the potential up-down operations between 0.4 and 1.0 V versus RHE, unlike the cases of Pt/C and Pt3Co/C, resulting in the high ORR performance. Here we report development of a new class of cathode catalysts with two different active sites for next-generation polymer electrolyte fuel cells.

Fluid sources and metallogenesis in the Baiganhu W–Sn deposit, East Kunlun, NW China: Insights from chemical and boron isotopic compositions of tourmaline

Tourmaline is widespread in the Baiganhu W–Sn deposit, Xinjiang Province, NW China. In this study, electron microprobe analysis reveals that tourmaline in the Baiganhu deposit belongs to the alkali and X-site group with low Ca and moderate X site vacancy, all beyond the confines of schorl–dravite series, with Na/(Na+Ca) and Fe/(Fe+Mg) ratios ranging from 0.769 to 0.965 and 0.518 to 0.822, respectively. In chemical discrimination diagrams, the tourmaline samples plot in the fields of Li-poor granite, associated with Al-saturated metapelites and metapsammites. The tourmaline cores are depleted in Mg, Ca, Ti, but enriched in Al and Fe compared to the rims. Substitution mechanisms for the compositional variations are dominantly due to MgFe−1, □Al(NaFe)−1, □Al(NaMg)−1, and AlO(Fe−1(OH))−1 exchange vectors. The δ11B values of the tourmalines range from −12.9 to −7.9‰, with a slight variation between cores and rims, which reflect a common boron source, and also indicate that the tourmaline crystallized during a single magmatic-hydrothermal event related to monzogranite. Tourmaline is a valuable prospecting indicator of W–Sn mineralization.

Synthesis, characterization and field emission properties of tin oxide nanowires

Tin oxide (SnO2) nanowires are synthesized by Au catalyzed chemical vapor deposition of Sn and C mixture at 900 °C by employing a continuous flow of Ar: O2 (10:1) for an hour. X-ray diffraction and Raman spectroscopy studies indicate that the as-grown SnO2 nanowires are crystalline in nature with tetragonal rutile phase. Electron microscopy studies reveal towards high aspect ratio of nanowires. The field emission studies show that SnO2 nanowires grown on Si substrate exhibit low turn-on field of 1.75 V/μm (at 0.1 μA/cm2) and long-term emission stability over a period of more than 50 h with a current density of 4 μA/cm2 at a constant electric field of 2.25 V/μm. Hardly any considerable degradation in the emission current is noticed even after 50 h which may be attributed to the high crystallinity of SnO2 nanowires.