Search

Goethite and modified goethites have been found as good photocatalysts because their conduction band can mediate electron transfer in various redox processes. Many kinds of metal elements can be incorporated into the structure of goethite to form solid solutions in nature, but their optoelectronic properties have not been well disclosed. Mn-substituted goethite is one of the potential photocatalysts, which can exhibit high-photocatalytic activity in many Earth’s surface processes. Based on the first-principles calculation, pairwise interaction energies and static lattice energies of goethitegroutite solid solution were computed, and the most thermodynamically stable configurations of Mn-substituted goethite were determined. The results indicate that Mn3+ ion tends to distribute within the cation layer parallel to the (001) plane. Phase relations of goethite-groutite solid solution were derived by subsequent configurational statistics with energies of all 232 configurations of a 2 × 1 × 4 supercell with 32 exchangeable cations. The phase diagram shows that no more than 3 mol% Fe of goethite can be substituted by Mn ions. Therefore, Mn-substituted goethite is thermodynamically metastable or bears groutite-like clusters/lamellae. Furthermore, the effects of Mn substitutions on the band gap were experimentally and theoretically investigated. It is found that a small amount of Mn-substitution can reduce the band gap of goethite significantly, and the decrease ceases when the Mn content is higher than 3–4 mol%. Such a decrease in band gap causes red-shift to the photo response wavelength of goethite and improves the responding capability. This improvement was confirmed in the experiments of photocatalytic degradation of methylene blue (MB). Such kind of photocatalytic reaction probably can happen widely in natural environments. Therefore, the contribution of photocatalysis of natural goethites to geochemical processes on Earth’s surface should be considered.

Understanding the formation of high field strength element (HFSE) mineralization remains a challenge. Processes ranging from melt generation to final crystallization have been invoked to play a key role in the enrichment of HFSEs in magmatic-hydrothermal systems, yet the importance of crystal-liquid fractionation, liquid immiscibility, and/or fluid unmixing remains debated. Here, we present results of a study of granites and HFSE-mineralized glimmerites from the granitic Suzhou pluton, eastern China. We provide whole-rock major and trace element compositions, a description of mineral assemblages, and a detailed description of zircon textures, zircon Raman spectra, zircon major and trace element and δ18O compositions, and U-Pb ages. The granites and glimmerites have been dated at ~126 to 124 Ma and are thus coeval. The granites range from biotite and zircon poor to biotite and zircon rich and are in contact with glimmerites. The glimmerites form lenses and layers close to and along the margin of the Suzhou granite, comprising up to ~37 vol % biotite and up to ~2 vol % zircon and other HFSE-rich accessory minerals. The biotite-poor granites contain a single type of zircon (type-A: single crystals, oscillatory zoned, fully crystallized structure, relatively poor in trace elements, and relatively high δ18O), whereas the biotite-rich granites and the glimmerites contain two zircon types (type-A crystals: same features as in the biotite-poor granites; type-B crystals: clustered, unzoned, partially metamict structure, rich in trace elements, and relatively low δ18O). Both granite types are Si, Al, and Na rich, whereas the glimmerites are Fe, Ti, Mn, Mg, Ca, P, F, and HFSE rich and, compositionally, fall off simple fractionation trends. We interpret the textural, mineralogical, and compositional relationships to indicate that the glimmerites are the products of Fe-, F-, and HFSE-rich immiscible melts that unmixed from an alkali-rich, moderately reducing (~QFM + 0.5 and ~QFM + 1.0; QFM = quartz-fayalite-magnetite buffer) Suzhou magma system at low crustal pressure. In addition, we note that the zircon textures and compositions are important recorders of the processes and conditions that led to the HFSE mineralization.

The Nanyangshan Li-Cs-Ta (LCT) pegmatite is the largest of hundreds of pegmatite dikes in the eastern Qinling orogenic district, North China. The Nanyangshan pegmatite is strongly zoned into a contact zone, border zone, wall zone, intermediate zone, and core, with Li mineralization occurring predominantly in the intermediate zone. Inward through the intermediate zone, Li mineralization is divided into subzones of Spd (spodumene), Mbs (montebrasite), Elb (elbaite), and Lpd (lepidolite). Lithium minerals include spodumene, montebrasite, lithiophilite, elbaite, lepidolite, and possible former petalite. Paragenetic assemblages of Li minerals are variable, with spodumene ± Li-phosphates (montebrasite and lithiophilite), Fe-rich elbaite, lepidolite, and possible former petalite in the Spd subzone; Li-phosphates (main montebrasite and rare lithiophilite) + spodumene + Fe-bearing elbaite + lepidolite in the Mbs subzone; Fe-poor elbaite + lepidolite ± montebrasite in the Elb subzone; and lepidolite ± Fe-poor elbaite in the Lpd subzone. Whole-rock contents of Li2O, P2O5, B2O3, and F are consistent with the high contents of various Li minerals. Spodumene was formed first and dominantly from a Li-saturated melt in the Spd subzone (1.66 wt% Li2O). This subzone graduates into the P-rich Mbs subzone (3.75 wt% P2O5) with montebrasite gradually succeeding Li-aluminosilicates, followed by the appearance of abundant Fe-poor elbaite in the Elb subzone (1.04 wt% B2O3), reflecting the consumption of P in the melt. Lepidolite formed after early-formed Li phases in the F-rich Lpd subzone (2.03 wt% F), as indicated by replacement textures. Among the numerous LCT pegmatites worldwide, the Li mineralization sequence can be suggested as Li-aluminosilicates (commonly spodumene and less commonly petalite) → Li-phosphates (montebrasite-amblygonite and triphylite-lithiophilite) → elbaite → lepidolite, and can be regarded as a general sequence for Li mineralization.

Zinconigerite-2N1S ZnSn2Al12O22(OH)2 and zinconigerite-6N6S Zn3Sn2Al16O30(OH)2 are two new minerals with different numbers and ratios of nolanite (N) and spinel (S) modules. Both phases have been discovered in the Xianghualing skarn, Hunan Province, China. Zinconigerite-2N1S (zn-2N1S) and zinconigerite-6N6S (zn-6N6S) are named for their chemical composition, number, and ratios of N-S modules, according to the nomenclature of the nolanite-spinel polysomatic series of Armbruster (2002). Both phases occur as aggregates, sub-to-euhedral crystals, with maximal dimensions up to 100 μm, within fluorite aggregates, and they are closely associated with phlogopite, chrysoberyl, magnetite, cassiterite, margarite, and nigerite-taaffeite group minerals. They do not show fluorescence in long- or short-wave ultraviolet light. The calculated densities are 4.456 g/cm3 for zn-2N1S and 4.438 g/cm3 for zn-6N6S. Optically, zn-2N1S is uniaxial (+) with ω = 1.83(1), ε = 1.84(2); zn-6N6S is uniaxial (+) with ω = 1.85(1), ε = 1.87(2) (λ = 589 nm). Their chemical compositions by electron-microprobe analyses give the empirical formulas (Zn0.734Mn0.204Na0.122Ca0.063Mg0.044)Σ1.166(Sn1.941Zn0.053Ti0.007)Σ2 (Al11.018Fe0.6903+Zn0.200Si0.092)12O22(OH)2 for zn-2N1S and (Zn1.689Mn0.576Mg0.328Fe0.4073+)Σ3(Sn1.882Zn0.047 Ti0.071)Σ2(Al14.675Fe1.0883+Na0.13Ca0.086Si0.017)Σ15.996O30(OH)2 for zn-6N6S. Both phases have trigonal symmetry; the unit-cell parameters of zn-2N1S (P3m1) and zn-6N6S (R3m), refined from single-crystal X-ray diffraction data, are, a = 5.7191(2) and 5.7241(2) Å, c = 13.8380(6) and 55.5393(16) Å, V = 391.98(3) and 1575.96(12) Å3, and Z = 1 and 3, respectively. The structure of zn-2N1S is characterized by the alternating O-T1-O-T2-O-T1 layers stacked along the c-axis, showing the connectivity of N-S-N. The polyhedral stacking sequence of zn-6N6S is 3 × (O-T1-O-T2-O-T2-O-T1), reflecting a N-S-S-N-N-S-S-N-N-S-S-N connectivity of the polysomatic structure. By contrast, the structure of zn-2N1S shows the elemental replacements of Al → Sn and Al → Zn, suggesting the substitution mechanism of 2Al → Zn + Sn. The complex substitution of Zn by multiple elements (Al, Fe3+, Mn, Mg) in the structure of zn-6N6S, is coupled with the low occupancy of Al5-octahedra. Fe3+ → Al substitution occurs in Al1-tetrahedra of both zn-2N1S and zn-6N6S. The new polysomes, zn-2N1S and zn-6N6S, likely crystallized under F-rich conditions during the late stages of the Xianghualing skarn formation. The discovery of zn-2N1S and zn-6N6S provides new insights into the crystal chemistry of the N-S poly-somatic series and its origin.

Chukochenite, (Li0.5Al0.5)Al2O4, is a new mineral species from the Xianghualing skarn, Hunan Province, southern China. It occurs as subhedral to euhedral crystals up to 200 μm across in the green rock of Xianghualing skarn, closely associated with fluorite, phlogopite, chrysoberyl, margarite, chlorite, ferronigerite-2N1S, and zinconigerite-2N1S. The crystals are colorless and transparent with a vitreous luster. Chukochenite is brittle with irregular fracture, has a Mohs hardness of 8, and shows light red fluorescence under 253.7 nm UV radiation and light green fluorescence under 365 nm UV radiation. The calculated density is 3.771 g/cm3. Chukochenite is optically biaxial (–) with α = 1.79(2), β = 1.82(2), and γ = 1.83(2) (589 nm). The calculated 2V is 60°, with the optical orientations X, Y, and Z parallel to the crystallographic a, b, and c, respectively. Electron microprobe analysis (Li by LA-ICP-MS) yielded in wt% Al2O3 80.70, Fe2O3 8.16, Li2O 3.68, ZnO 3.25, MnO 2.49, MgO 1.70, Na2O 0.11, CaO 0.08, TiO2 0.02, K2O 0.01, and Cr2O3 0.01 (total 100.24 wt%), giving an empirical formula [(Li0.355Al0.138Na0.005Ca0.002)Σ0.5(Al0.145Fe0.147+3Mg0.061Zn0.058Mn0.051Si0.001)Σ0.463]Al2O4 on a basis of 4 O atoms per formula unit. Chukochenite is orthorhombic, Imma, a = 5.659 (1), b = 16.898 (1), c = 7.994 (1) Å, V = 764.46 (8) Å3, and Z = 12. The nine strongest lines of powder XRD [d in Å (I) (hkl)] are: 2.405 (53) (231); 1.996 (29) (260); 1.535 (77) (303); 1.413 (100) (264); 1.260 (52) (2 12 0); 1.068 (36) (1 13 4); 1.039 (61) (503); 0.999 (59) (008); and 0.942 (35) (3 13 4). Chukochenite has a framework structure of spinel with low symmetry (orthorhombic Imma) due to the ordering of Li cations over octahedrally coordinated sites, which has not been previously reported for synthetic (Li0.5Al0.5) Al2O4. This structure type is based on a framework of AlO4 tetrahedra, AlO6, and LiO6 octahedra. AlO6 edge-sharing octahedra form chains along the a axis. AlO6 octahedra and LiO6 octahedra in a 2:1 ratio share edges, forming octahedral chains along b. These octahedral chains are connected by AlO4 tetrahedra and each corner of an AlO4 tetrahedron shares with three AlO6 octahedra or two AlO6 + one LiO6 octahedra. The discovery of chukochenite adds a new perspective on the cation ordering and the mechanism of luminescence and magnetism in (Li0.5Al0.5)Al2O4.

Mineral resources are essential to prosperity and security of modern societies. How mineral resources can guarantee sustainable development of economy in countries, especially those developing countries, has long been a focus of attention of international communities. This paper provides a comprehensive summary for major advance of the research on mineral resources in past decades, and proposes some key issues regarding ore-forming mechanism, exploration and utilization of major and critical mineral resources. On the basis of these aspects, we also identify four priority science issues to be addressed in the future, including (1) mechanism of both metal circulation and extremely high concentration, (2) theories and technologies of prospecting deep-earth resources, (3) investigation of mineral resources in seafloor and polar regions, and (4) efficient, clean and recycling utilization of mineral resources. It can be expected that new advances in these four issues would tremendously promote the innovation of mineral resource science, and provide scientific and technologic support to meet the demand of mineral resources for human activities and the harmonious development of both mineral-resource exploration and ecological restoration.

Due to their relatively high Hf contents (i.e., several hundreds to thousands of ppm), columbite-group minerals (CGMs) are suitable for Lu–Hf isotope analysis, which can provide new insights into the source of such minerals in combination with the U–Pb age of rare-metal deposits. However, few studies have reported Lu–Hf isotope data for CGMs. Tantalum is a major element in CGMs (12–48 wt% Ta2O5) and has a significant effect on measurements of Hf isotopes using MC-ICP-MS. This effect was first evaluated in this study by analysis of mixed Hf–Ta standard solutions with different Ta/Hf ratios and LA-MC-ICP-MS analysis of various CGMs. This analytical artifact reflects serious tailing of the large 181Ta signal onto the 180Hf and 179Hf masses during analysis. Therefore, in order to obtain accurate Hf isotope data for CGMs by MC-ICP-MS, we present an improved chemical separation procedure for Hf from Ta, and also a novel analytical protocol for LA-MC-ICP-MS analysis of CGMs. Accurate in situ176Hf/177Hf ratios for CGMs can be obtained by normalization to 178Hf/177Hf = 1.4672, rather than 179Hf/177Hf = 0.7325, using the exponential law. This approach was validated by solution and laser ablation MC-ICP-MS analysis of four CGM samples from China and Africa. The Lu–Hf isotopic composition of CGMs provides a new geochemical tracer for rare-metal deposits.

The two element pairs Nb-Ta and Zr-Hf have similar geochemical behaviors and are critical mineral resources due to their specialized applications in modern high-technology industries. Globally, based on the type of host rock, Nb, Ta, Zr, and Hf resources can be divided into granite- and granitic pegmatite-type, carbonatite-type, alkaline rock-type, and related exogenic deposits. Low reserves and a high import dependency on these metals are important issues for China. There are ca. 50 Nb-Ta deposits in China, with estimated reserves of Nb2O5 and Ta2O5 of 2.67 × 106 and 0.17 × 106 t, respectively (excluding the Nb reserves in the Bayan-Obo REE-Nb-Fe deposit). Most of these deposits are hosted in aluminous granites, including peraluminous and metaluminous granite types. Examples include the Yichun peraluminous granite-type Nb-Ta deposit in Jiangxi Province, the Guposhan metaluminous granite-type Nb deposit in Hunan and Guangxi and the granitic pegmatite-type Nanping Nb-Ta-Li deposit in Fujian Province. Other minor deposits include the carbonatite-type (e.g., the Miaoya REE-Nb deposit in Hubei Province) and the alkaline rock-type (e.g., the Ba’erzhe REE-Zr-Nb-Be deposit in Inner Mongolia). Niobium-Ta resources in China are located mainly in the western Pacific domain (e.g., the Nanling Range and Jiangnan orogenic belt), the Paleo-Asian Ocean domain (e.g., the Altay Li-Be-Nb-Ta ore belt), the Tethyan domain (e.g., the Songpan-Ganze Li-Be-Nb-Ta and Himalaya Be-Nb-Ta leucogranite ore belts), and at the margins of the Yangtze and North China cratons (e.g., the Nb deposits in the Qinlin orogenic belt). These deposits formed during the Meso-Neoproterozoic (e.g., the Bayan-Obo REE-Nb-Fe deposit during 1.4–1.3 Ga), Paleozoic (ca. 400–380 Ma), early Mesozoic (Paleo-Tethys tectonism; 250–200 Ma), late Mesozoic (the metallogenic explosion in South China; ca. 160–120 Ma), and Cenozoic (Himalaya leucogranite belt; 44–7 Ma). An estimated 500 ´ 103 t of ZrO2 is hosted in both endogenic and exogenic deposits in China. The endogenic Zr-Hf resources are commonly associated with Nb-Ta deposits, due to their similar geochemical behavior. Most of these are hosted in alkaline-peralkaline granites (e.g., the Ba’erzhe REE-Nb-Ta-Zr deposit), along with minor deposits in aluminous granite and granitic pegmatite (e.g., the Koktokay Li-Be-Nb-Ta-Zr-Hf deposit in Xinjiang). There are no occurrences of carbonatite-type Zr-Hf deposits in China. The endogenic Zr-Hf deposits are located primarily along with deep fractures or in rifted regions, including the ore belts of the Tarim and Northern China cratons (e.g., the Boziguo’er alkaline syenite-type deposit in Xinjiang), the western Yangtze Craton (e.g., the Cida alkaline granite-type deposit in Sichuan Province), and the southern Daxing’an mountain range (e.g., the Ba’erzhe alkaline granite-type deposit). These endogenic Zr-Hf deposits formed during the late Paleozoic and Mesozoic. Although endogenic deposits host the main Zr-Hf resources in China, few have been economically exploited due to their low grade and technical challenges. In contrast, domestically available Zr-Hf resources have been exploited from zircon in Quaternary exogenic deposits, including littoral placers (e.g., the Wenchang placers in Hainan Province), fluvial-alluvial placers (e.g., the No. 725 deposit in Guangxi), and weathered crust-type deposits (e.g., the No. 520 deposit in Guangxi). In these exogenic deposits, the ore minerals commonly include zircon, rutile, monazite-(Ce), ilmenite, and other heavy minerals that were derived mainly from Mesozoic granites. Hainan Province is China’s largest region of mined exogenic Zr deposits, which occur mostly in Wenchang, Qionghai, Wanning, and Lingshui counties along its southeastern coastline. In summary, although China hosts diverse types of Nb-Ta-Zr-Hf resources and its reserves are large, most of the deposits are of low grade and difficult to utilize. Therefore, future research should focus on ore formation mechanisms, mineral exploration, and improvements in resource recycling, mineral processing, and industrial efficiency.

Description, Felsic volcanism in South China with Cu, Hg, and S released exacerbated environmental changes that drove the end-Permian extinction., The Siberian Traps large igneous province (STLIP) is commonly invoked as the primary driver of global environmental changes that triggered the end-Permian mass extinction (EPME). Here, we explore the contributions of coeval felsic volcanism to end-Permian environmental changes. We report evidence of extreme Cu enrichment in the EPME interval in South China. The enrichment is associated with an increase in the light Cu isotope, melt inclusions rich in copper and sulfides, and Hg concentration spikes. The Cu and Hg elemental and isotopic signatures can be linked to S-rich vapor produced by felsic volcanism. We use these previously unknown geochemical data to estimate volcanic SO2 injections and argue that this volcanism would have produced several degrees of rapid cooling before or coincident with the more protracted global warming. Large-scale eruptions near the South China block synchronous with the EPME strengthen the case that the STLIP may not have been the sole trigger.

The nepheline syenite pegmatite in the Saima alkaline complex in northeastern China is characterized by REE mineralization, mainly rinkite-(Ce) and associated alteration minerals. As the most abundant REE-bearing mineral in the pegmatite, rinkite-(Ce) closely coexists with microcline, nepheline, natrolite, and calcite. Some rinkite-(Ce) grains show compositional sector-zonation, in which the inner core displays relatively high Ti, Ca, and Sr concentrations, but low Zr, REE, and Na contents. Primary rinkite-(Ce) has undergone multiple episodes of fluid interactions, and accordingly, from weak to strong, three different mineral assemblages of hydrothermal alteration can be summarized: (1) rinkite-(Ce) + secondary natrolite ± K-feldspar ± minor fluorbritholite-(Ce); (2) rinkite-(Ce) relics + secondary natrolite + K-feldspar + fluorbritholite-(Ce) + unidentified Ca-Ti silicate mineral + fluorite and calcite; and (3) pseudomorphs after rinkite-(Ce). The pseudomorphs can be divided into two groups characterized by distinct mineral associations: (1) Ca-bearing strontianite + fluorbritholite-(Ce) + natrolite + fluorite + calcite coexisting with silicate minerals; and (2) calcite + fluorite + fluorbritholite-(Ce) + rinkite-(Ce) relics ± Ca-bearing strontianite ± ancylite-(Ce) associated with a calcite matrix. These alteration mineral assemblages are evidence of magmatic-derived alkali metasomatism due to an alkali-CO2-F-rich fluid and Ca-metasomatism due to a different, externally derived Sr- and Ca-rich fluid. The metasomatic events acted as the potential driving force for the rinkite-(Ce) dissolution and pseudomorph-forming process. The high concentration of rinkite-(Ce) in the nepheline syenite pegmatite results from the fractional crystallization of the Saima CO2-rich alkaline silicate magma, and the successive alterations of rinkite-(Ce) attest to the important role played by hydrothermal fluids in controlling the remobilization of REE and the crystallization of secondary rare earth minerals.

Uncertainty surrounding the Early Cretaceous tectonomagmatic evolution and basin development of the Bangong–Nujiang suture zone (BNSZ) limits understanding of the history of Meso-Tethys Ocean and the initial uplift and large-scale metallogenesis of the Tibetan Plateau during the Mesozoic. Here we present new geochronological, geochemical and isotopic data for the Early Cretaceous volcano-intrusive rocks (including quartz-diorites, tholeiitic andesites, and bajaitic latites) around the western segment of the BNSZ (W-BNSZ). We also report an Early Cretaceous deep-water volcano-stratigraphic section newly identified in this region. Based on these new data and information available for the BNSZ, we propose that the W-BNSZ and surrounding regions had already entered a stage of soft-collisional land-locked basin evolution during the Early Cretaceous. The land-locked basin underwent limited uplift related to the initial soft collision during the earliest Early Cretaceous, resulting in the formation of a regional unconformity between Shamuluo Formation shallow-marine sedimentary rocks and underlying ophiolitic melange. Subsequently, the basin experienced continuous subsidence related to sinking and rollback of the Bangong oceanic slab, leading to the occurrence of deep-water flysch deposits (e.g., the Zhaga Formation). The Bangong oceanic slab was completely detached from the overlying soft-collision zone at ca. 113 Ma, resulting in the strong isostatic uplift of the whole soft-collision zone. Consequently, seawater receded from W-BNSZ and surrounding regions during the late Early Cretaceous–Late Cretaceous. Our study also shows that the western segment of the South Qiangtang terrane experienced long-lived intermediate magmatism (130–104 Ma) under this soft-collision regime. Intermediate magmas of this age originated from partial melting of juvenile lower crust, fractional crystallization of mantle-derived mafic magmas, and partial melting of metasomatized mantle-wedge peridotites, and these processes were driven by the break-off, rollback, and complete detachment of the Bangong oceanic slab, respectively.

The effects of demineralization, CH3OH-THF mixed solvent swelling, CH3OH-THF swelling coupled with in-situ loading of metal ions (Ca2+, Mn2+, Cu2+ and Co2+) on pyrolysis reactivity and kinetic characteristics of Shendong low rank coal were investigated. The structure of coal samples was characterized by solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR) and Fourier transform infrared spectrometer (FTIR). The pyrolysis characteristics and distribution of pyrolysis products of coal were analyzed by thermogravimetric analyzer/Fourier transform infrared spectrometer (TG-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and the fixed bed reactor. The results show that solvent swelling coupled with in-situ loading of Ca2+, Mn2+, Cu2+ and Co2+ promotes coal pyrolysis, and their net weight losses increase by 2.14 wt%, 0.07 wt%, 6.31 wt% and 6.18 wt%, respectively. Py-GC/MS analysis shows that the treatment of solvent swelling coupled with in-situ loading of metal ions Ca2+, Mn2+, Cu2+, Co2+ can increase the content of aromatic hydrocarbons and decrease the content of acidic compounds in coal tar. The content of benzene increases under the action of solvent swelling coupled with in-situ loading of Cu2+ and Co2+ by 42.73 wt% and 40.98 wt%, respectively. The kinetic calculation shows that the activation energies of the first and second stages of coal pyrolysis are reduced and the reactivity of coal can be improved by swelling coupled with in-situ loading of metal ions.

Granite-related wolframite-quartz veins are the world's most important tungsten mineralization and production resource. Recent progress in revealing their hydrothermal processes has been greatly facilitated by the use of infrared microscopy and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of both quartz- and wolframite-hosted fluid inclusions. However, owing to the paucity of detailed petrography, previous fluid inclusion studies on coexisting wolframite and quartz are associated with a certain degree of ambiguity. To better understand the fluid processes forming these two minerals, free-grown crystals of intergrown wolframite and quartz from the giant Yaogangxian W deposit in South China were studied using integrated in situ analytical methods including cathodoluminescence (CL) imaging, infrared microthermometry, Raman microspectroscopy, and fluid inclusion LA-ICP-MS analysis. Detailed crystal-scale petrography with critical help from CL imaging shows repetition of quartz, wolframite, and muscovite in the depositional sequence, which comprises a paragenesis far more complex than previous comparable studies. The reconstruction of fluid history in coexisting wolframite and quartz recognizes at least four successive fluid inclusion generations, two of which were entrapped concurrently with wolframite deposition. Fluctuations of fluid temperature and salinity during precipitation of coexisting wolframite and quartz are reflected by our microthermometry results, according to which wolframite-hosted fluid inclusions do not display higher homogenization temperature or salinity than those in quartz. However, LA-ICP-MS analysis shows that both primary fluid inclusions in wolframite and quartz-hosted fluid inclusions associated intimately with wolframite deposition are characterized by strong enrichment in Sr and depletion in B and As compared to quartz-hosted fluid inclusions that are not associated with wolframite deposition. The chemical similarity between the two fluid inclusion generations associated with wolframite deposition implies episodic tungsten mineralization derived from fluids exhibiting distinct chemical signatures. Multiple chemical criteria including incompatible elements and Br/Cl ratios of fluid inclusions in both minerals suggest a magmatic-sourced fluid with the possible addition of sedimentary and meteoric water. Combined with microthermometry and Raman results, fluid chemical evolution in terms of B, As, S, Sr, W, Mn, Fe, and carbonic volatiles collectively imply fluid phase separation and mixing with sedimentary fluid may have played important roles in wolframite deposition, whereas fluid cooling and addition of Fe and Mn do not appear to be the major driving factor. This study also shows that fluid inclusions in both wolframite and coexisting quartz may contain a substantial amount of carbonic volatiles (CO2 ± CH4) and H3BO3. Ignoring the occurrence of these components can result in significant overestimation of apparent salinity and miscalculation of LA-ICP-MS elemental concentrations. We suggest that these effects should be considered critically to avoid misinterpretation of fluid inclusion data, especially for granite-related tungsten-tin deposits.

The influences of two kinds of natural mineral zeolite catalysts and the mass ratios of low-temperature coal tar (CT) to natural mineral zeolite on the yield and distribution of volatile products, ...

The low temperature solvent pretreated experiments of vitrinite sorted out from Permo-carboniferous high organic sulfur fine coal were performed to research the effects of solvent pretreatment on the characteristics of pyrolysis products and the composition and distribution of sulfur in the produced coal tar. Six solvents containing hot water, ethanol solution, 1, 2-propanediol solution, KOH solution, KOH-ethanol solution and KOH-1, 2-propanediol solution were employed. The results show that the solvent pretreatment method has little influence on the organic sulfur content of coal, but it results in the increase of coal tar yield and a great variation of volatiles during the pyrolysis of pretreated coals. Six types of thiophenes, containing benzothiophene, dibenzothiophene, naphthothiophene, benzo[b]naphthothiophene, dinaphthothiophene and phenanthro[9,10-b]thiophene, were detected in coal tars. The pretreatments of hot water, ethanol solution and alkaline ethanol solution show the ring opening to large aromatic structures in coal. The generation of benzothiophene, dinaphthothiophene and phenanthro[9,10-b]thiophene may be due to the ring opening effect.

The optimum conditions of toluene insoluble-quinoline soluble fraction (TI-QS) obtained by n-heptane Soxhlet extraction residue of low-temperature coal tar (H-CT) reacted with formaldehyde were det...

The structural features and pyrolysis characteristics of Shendong demineralized coal (DC) and its ethanol swelling coal (EDSC) were investigated by Fourier transform infrared (FTIR), solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C-NMR), thermo-gravimeter-Fourier transform infrared (TG-FTIR) spectroscopy, the self-made steel retort assay, and pyrolysis gas chromatography-mass spectrometer (Py-GC/MS). The pyrolysis product coal tar from the self-made steel retort assay was extracted by n-hexane to obtain the n-hexane solubles (CTHS) as well as the n-hexane insolubles (CTHIS). The composition of CTHS has been explored by the analysis of GC/MS, and CTHIS was investigated by the analyses of TG-FTIR and Py-GC/MS. The analysis data display that the coal tar yield of EDSC increases by 0.42 wt% and the semi-coke yield of EDSC decreases by 1.33 wt%. The intensity of −OH stretching vibration at 3405 cm−1 in the FTIR spectra of EDSC is weakened and the peak moves to the low wave number. Aliphatic carbons and aromatic carbons of EDSC decrease. The content of neutral compounds in EDSC pyrolysis tar increases by 2.01 wt%. CTHIS mainly includes phenols, alkanes, aromatics and pyridine. Phenolic compounds and nitrogen-containing heterocyclic compounds in the pyrolysis volatiles of EDSC-CTHIS increase by 1.12 wt% and 1.46 wt%, respectively.

South China hosts many Nb–Ta deposits that show evidence for episodic mineralization, which were generated during the emplacement of composite granites. To constrain the spatio-temporal distribution of Nb–Ta mineralisation in the region and to identify future targets for mineral exploration, we used in situ laser ablation-inductively coupled plasma-mass spectroscopy to date 23 columbite-tantalite group mineral (CGM) samples from 14 Nb–Ta deposits. Our CGM U–Pb data, supplemented by previous results, reveal five distinct Nb–Ta mineralisation events in South China as follows: (1) Late Silurian–Middle Devonian (ca. 424–391 Ma; e.g., the Xigang and Nanping deposits in eastern Jiangxi and western Fujian Provinces); (2) Triassic (ca. 248–204 Ma; e.g., the Houxi, Cunxin, Dongtounan, Shenkeng, Limu and Gaoling deposits in western Guangdong Province and northeastern Guangxi Zhuang Autonomous Region; (3) Late Jurassic (ca. 160–150 Ma; e.g., the Gedongping, Yichun, Laiziling, Jianfengling and Jinzhulong deposits in Guangxi, Jiangxi and Hunan Provinces); (4) Early Cretaceous (ca. 130 Ma; e.g., the Huangshan and Songshugang deposits in northeastern Jiangxi province); and (5) Late Cretaceous (ca. 90 Ma; e.g., the Jiepailing deposit, located along the boundary between Hunan and Jiangxi Provinces). We show that Nb–Ta mineralisation in South China was controlled by multiple tectono-magmatic events. Our CGM samples yielded Caledonian (ca. 424–391 Ma), early Indosinian (ca. 248 Ma) and late Yanshanian (ca. 130 Ma) ages, indicating that Nb–Ta mineralisation was abundant during these times and should form the focus for future studies of mineralisation in the region. Early Triassic granite in the Guangning Nb–Ta metallogenic district in western Guangdong Province, Indosinian and early Yanshannian granites in the Miao’ershan–Yuechengling batholith in northeastern Guangxi, and the Late Cretaceous Lingshan batholith in northern Jiangxi Province are identified as targets for future Nb–Ta exploration.

Crystallization is one of the most fundamental processes for both solid inorganic and organic materials in nature. The classical crystallization model mainly involves the monomer-by-monomer addition of simple chemical species. Recently, nanoparticle attachment has been realized as an important mechanism of crystallization in comparatively low-temperature aqueous natural and synthetic systems. However, no evidence of crystallization by particle attachment has been reported in petrologically important melts. In this study, we described spherical (Mg,Fe)-oxides with a protrusion surface in a shock-induced melt pocket from the martian meteorite Northwest Africa 7755. Transmission electron microscopic observations demonstrate that the (Mg,Fe)-oxides are structure-coherent intergrowth of ferropericlase and magnesioferrite. The magnesioferrite is mainly present adjacent to the interface between (Mg,Fe)-oxides spherules and surrounding silicate glass, but not in direct contact with the silicate glass. Thermodynamic and kinetic considerations suggest that development of the spherical (Mg,Fe)-oxides can be best interpreted with crystallization by particle attachment and subsequent Ostwald ripening. This indicates that crystallization by particle attachment can also take place in high-temperature melts and has potential implications for understanding the nucleation and growth of early-stage crystals in high-temperature melts, such as chondrules in the solar nebula, erupted volcanic melts, and probably even intrusive magmas.

Although Rb/Sr ratio and Sr isotopes are routinely modeled to determine petrogenetic processes and sources for granitic systems, the post-magmatic path and crystallization of Sr in granitic systems have not been thoroughly elucidated to date. In this study, we present the petrography, chemical composition and isotopic 87Sr/86 of Sr-bearing phosphates from the Nanping No. 31 pegmatite in Southeastern China, helping to characterize post-magmatic stages and geochemical recirculation of Sr in granitic systems. K-feldspar and primary apatites occur as major &ldquo, primary Sr minerals&rdquo, the occurrences of secondary Sr phosphates (strontiohurlbutite, palermoite and goyazite) and Sr-rich phosphates (apatites, hurlbutite, bertossaite and fluorarrojadite-(BaNa)) reflect the transport, concentration and recrystallization of Sr in granitic systems. The mobilization and recrystallization of Sr in granitic systems are mainly controlled by the variation in alkalinity of hydrothermal fluids. Two post-magmatic recirculations of Sr are proposed in the Nanping No. 31 pegmatite: (1) breakdown of the &ldquo, primary Sr mineral&rdquo, (K-feldspar and primary apatites) and crystallization of secondary Sr-bearing phases, and (2) replacement of secondary Sr-bearing phosphates and direct precipitation of later palermoite and goyazite from later Sr-rich fluids at low temperatures. The Sr isotope features of Sr-bearing phosphates suggest that the emplacement and consolidation processes of the Nanping pegmatite involved the participation of externally derived fluids.

There are four episodes (Neoproterozoic, early Paleozoic, early and late Mesozoic) of Sn-W-Nb-Ta mineralization in South China, accounting for more than 50% W and 20% Sn reserves of the world and hosting considerable Nb and Ta resources. The genesis for such large-scale mineralization that may have seen multiple phases of recycling of ore elements is not well unterstood. The study of the earliest mineralized granites in South China, however, may be helpful to better understand the mechanism of mineralization. We present detailed mineralogical, geochemical, and isotopic data from two typical Neoproterozoic, mineralized intrusions, i.e., the Fanjingshan and Yuanbaoshan tourmaline leucogranites. There is a characteritstic mineral succession of diverse magmatic (columbite group minerals [CGMs], Nb-Ta-bearing cassiterite) and hydrothermal (wolframite, wolframoixiolite, Nb-Ta-poor cassiterite) Sn-W-Nb-Ta oxides. Hydrothermal cassiterite and W-bearing oxides (wolframite, wolframoixiolite) in the Yuanbaoshan intrusion were deposited separately by two types, i.e., Sn-rich and Nb-W-rich fluids. In-situ U-Pb dating of zircon, columbite and wolframoixiolite yields ages of 830 ± 5, 832 ± 5 and 821 ± 5 Ma, respectively. Whole-rock eNd(t) values of −2.5 to −6.4 correspond to crustal Nd model ages of 1.6–1.9 Ga. Paleoproterozoic model ages (~1.6–2.2 Ga) for most episodes of W-Nb-Ta mineralization in South China indicate that (i) Paleoproterozoic or older sediments may have been involved in the formation of W-Nb-Ta bearing granites and (ii) contributions of juvenile material was not important for these W-Nb-Ta mineralization. Neoproterozoic peraluminous granites along the Jiangnan Orogen formed in post-collision environments, but only those in the western part show Sn (-W-Nb-Ta) mineralization. The mineralized Neoproterozoic granites of the western part have experienced more extensive fractional crystallization (lower Nb/Ta, Zr/Hf ratios and more depleted in Fe, Mg, Ca, Sr, Ba, Eu, Ti) and are richer in volatiles (H2O, B) than the barren peraluminous intrusions of the eastern part. As similarly evolved Mesozoic metaluminous granites of the Nanling area have considerably more important tin mineralization than the mineralized Neoproterozoic granites, fractionation is not the only factor controlling mineralization. Instead, other factors, such as protolith and conditions of partial melting may account for the more important Mesozoic tin mineralization.

International audience; The W-Sn Maoping deposit and related W-Sn deposits from the world-class Nanling Range in Southeast Chinaformed at ca. 160 Ma and experienced several phases of metal addition and metal redistribution between 160and 130 Ma. Isotopic dating of ore mineral (wolframite) of Maoping demonstrates that W was deposited first,during a hydrothermal event at ca. 160 Ma. Successive fluid episodes, at ca. 156 Ma (Mo and Sn-rich fluid) and152 Ma (REE-rich fluid), resulted in the formation of REE- and Fe-Cu-Zn-sulfide minerals. A last fluid eventoccurring at ca. 130 Ma was responsible for the deposition of Zr-REE-Nb-Ta minerals that are attributed tomagmatic fluids derived from unexposed magmatic bodies. The three episodes of fluid circulation post-dating Wdeposition resulted in partial to complete resetting of the isotopic systems (mica, wolframite, xenotime), whichare conventionally used for dating such deposits. We show that W and Sn mineralization in the Nanling Rangeformed during a unique fluid event at ca. 160 Ma. Later fluid episodes redistributed the previously depositedmetals and sequentially introduced additional metals, including Mo-Sn, Fe-Cu-Zn, and Zr-REE-Nb-Ta. Directdating of paragenetically well-constrained minerals is therefore critical for determining the age and the durationof mineralizing processes and for characterizing the fluid evolution of magmatic-hydrothermal systems, as exemplifiedin the Nanling Range.

In recent decades, the bioleaching of chalcopyrite has been successfully developed and employed in copper hydrometallurgy. Understanding the decomposition mechanism of chalcopyrite is also of great significance for environmental remediation because the microbial oxidation of metal sulfides in mining waste and outcrop rocks commonly causes serious environmental contamination. This study investigates the influence of Acidithiobacillus ferrooxidans (A. ferrooxidans) and added Fe2+ ions on the oxidation of chalcopyrite. The results show that A. ferrooxidans and added Fe2+ ions can collaboratively promote the recovery of Cu from chalcopyrite. In the bioleaching system with added Fe2+ ions, A. ferrooxidans prefer to oxidize soluble Fe2+ ions rather than decompose chalcopyrite to acquire energy, which inhibits the release of Cu at the first stage but enhances the growth of A. ferrooxidans. After reacting for 18 days, however, the produced Fe3+ ions greatly promote decomposition and release more Cu than the bioleaching system free of Fe2+, which remained in the rest experiments. Both the oxidation of chalcopyrite and the release of Cu in the bioleaching system are greater than what occurs in the chemical leaching system. Chalcocite, covellite, bornite, and elemental sulfur were identified as intermediate products, and a sulfur transforming route of S2−/S22− → Sn2−/S0 → SO32− → SO42− can be recognized by X-ray photoelectron spectroscopy. As the principle end product, jarosite covered the chalcopyrite grains and consequently inhibited further oxidation. It is noteworthy that the released Cu2+ ions barely suppressed the growth of A. ferrooxidans because they tended to be enriched only in extracellular polymeric substance (EPS), while Fe3+ ions could be found on both the cell surfaces and the EPS, which implies a potential mechanism for the survival of cells in a high Cu2+ solution. Collectively, an integrated model of chalcopyrite oxidation, collaborated by both chemical and microbial oxidation, has been proposed to elucidate the bioleaching mechanisms and to give a perspective on its hydrometallurgical and environmental applications.

In this study, the structures and acidity constants (p Ka's) of uranyl arsenate complexes in solutions have been revealed by using the first principle molecular dynamics technique. The results show that uranyl and arsenate form stable complexes with the U/As ratios of 1:1 and 1:2, and the bidentate complexation between U and As is highly favored. Speciation-pH distributions are derived based on free energy and p Ka calculations, which indicate that for the 1:1 species, UO2(H2AsO4)(H2O)3+ is the major species at pH 12.1, respectively.

The Laiziling granitic pluton, located in the Xianghualing district, Hunan Province, China, comprises typical rare-metal granites with a pronounced vertical lithological zonation. This pluton includes three granitic phases comprising, from base to top, medium-grained (MG) alkali feldspar granite, fine-grained (FG) alkali feldspar granite and albite granite. Here we report the results of textural and chemical analyses of W–Nb–Ta oxide minerals from the Laiziling granitic pluton. The chemical compositions of whole-rock samples, rock-forming minerals and zircon have allowed us to identify the magmatic–hydrothermal processes that operated during the formation and rare-metal mineralization of the Laiziling pluton. The granites are slightly peraluminous to peraluminous, highly evolved and fractionated, as inferred from whole-rock geochemical and mineralogical (micas and zircon) signatures. All the micas in different granitic phases are classified into the zinnwaldite group. Li concentration in the primary micas (∼2.6–4 wt% Li2O) and Hf concentration (∼1–8 wt% HfO2) in the zircon increase for the base to the top granitic phases. Both alkali feldspar granites contain oxide mineral aggregates including columbite-group minerals, wolframoixiolite, qitianlingite, wolframite and cassiterite. The columbite-group minerals, wolframite and cassiterite also occur as isolated grains within the albite granite. The presence of the oxide minerals suggests that the W–Nb–Ta mineralization developed during the latter stages of the magmatic evolution, related to fluids that were compositionally evolved from the granites. The composition of the fluids controls the aggregate of the oxide minerals. The wolframite and cassiterite that precipitated within the Laiziling skarn-type deposit are chemically different from those within the granite, indicating a hydrothermal origin for the oxide minerals that formed as a result of pervasive alteration.

Most tin deposits worldwide are inferred to have formed from fluids derived from evolved (granitic) magma systems. Neoproterozoic silicate- and sulfide-stage Sn deposits at Jiumao of South China, in contrast, have been thought to be derived from metasedimentary and mafic-ultramafic host rocks. The Sn deposit may thus have formed by components and processes distinct from those that commonly contribute to Sn deposits, although spatially associated greisen-hosted Sn deposits also occur. To characterize in detail the formation of the Jiumao ore deposits, which contain ∼28,000 t of Sn, we present new field and petrographic observations, major- and trace-element compositions for silicate and ore minerals, and U-Pb age data of cassiterites and zircons for the deposits and granites. Our research shows that (1) the granite-greisen system formed at ∼830 Ma, which is the earliest Sn mineralization event in South China; (2) the silicate- and sulfide-stage ores in the country rocks formed at an fO2 of ∼NNO with temperatures of 350 °C and 170 °C, respectively; (3) all vein-type Sn ores at Jiumao were formed by Sn-F-B-rich fluids that were derived from the Yuanbaoshan granite magma system rather than ultramafic rocks; (4) the Fe-rich character of the ores hosted by the metasedimentary rocks and the Mg-rich character of the ores hosted by the ultramafic rocks largely controlled the reactions and efficacy of cassiterite precipitation and thus ore grade. We highlight that differences in mineral assemblages largely relate to differences of the protolith compositions and fluid-rock reactions (e.g., B- and tourmaline deposition in the ores hosted by the metasedimentary rocks, but not in the ores hosted by the ultramafic rocks). Cassiterite and titanite trace-element compositions reflect fluid composition, protolith composition, and intensive parameters of crystallization.

Troilite-orthopyroxene intergrowths are present as a common material in the brecciated diogenite Northwest Africa (NWA) 7183. In this study, we report on the petrographic, mineralogical, and rare earth element abundances of the troilite-orthopyroxene intergrowths to constrain their origin and assess their implications for the diverse petrogenesis of diogenites. Two groups of troilite-orthopyroxene intergrowths with various grain sizes and mineral chemistry have been observed in NWA 7183. One group of intergrowths contains fine-grained (

Magmatic-hydrothermal ore-forming processes play an important role in the transport, enrichment and mineralization of Li. In this study, first principles molecular dynamics (FPMD) and classical molecular dynamics (CMD) techniques were employed to investigate the speciation of Li in silicate melts and hydrothermal fluids. FPMD results show that Li does not form stable ion pair with F or Cl in silicate melts, but forms four-fold Li O coordination. Association constants of Li—F/Cl ion pairs in hydrothermal fluids under a wide range of T-P conditions (i.e., temperatures up to 1273 K and fluid densities ranging from 0.1 g/cm3 to 1.0 g/cm3) derived with constrained CMD show increasing stability with temperature increasing or fluid density decreasing. Together with previous studies on Na/K—F/Cl ion pairs, an association constant database is provided for alkali halides ion pairs. It is found that Li F ion pair is dominant in geological vapors.

Phosphate minerals are key indicators for understanding the processes of diagenesis and mineralization in granitic systems. More importantly, these minerals provide constraints on the post-magmatic behaviour of Li in pegmatite systems that remain to be explored, although Li from early-crystallized Li phosphates is known to leach into hydrothermal fluids. In this study, we performed a detailed petrographic and compositional analysis of phosphate minerals from the Nanping No. 31 pegmatite in southeastern of China, which provides new evidence of Li circulation in granitic systems. Primary phosphate minerals evolved from xenotime and monazite to Mn-rich fluorapatite and then to triphylite and montebrasite, with large amounts of montebrasite in the intermediate zones of the pegmatite, reflecting the increasing activities of both Li and P in peraluminous granitic melts. Montebrasite experienced stages of both high-temperature (360–273 °C) and low-temperature (273–100 °C) hydrothermal alteration. The high-temperature hydrothermal alteration of montebrasite by Fe- and Mg-rich fluids resulted in the formation of a series of Fe-, Mg-bearing phosphates; the replacement of montebrasite under low-temperature alteration generated amounts of Ca-, Sr-, Ba-bearing phosphate minerals, muscovite and akdalaite (Al2O3)4·H2O. The formation of micro-networks of akdalaite from montebrasite indicate the low mobility of Al in hydrothermal fluids. A four-stage scenario of post-magmatic Li transport in the Nanping No. 31 pegmatite is proposed: (1) Li derived from the breakdown of primary montebrasite was locally recrystallized and produced secondary montebrasite (Mtb-1); (2) hydrothermal alteration by Fe- and Mg-bearing fluids leached Li from montebrasite to form secondary triphylite and simferite; (3) Li derived from the alteration of montebrasite by Sr-, Ca-rich fluids was involved in the formation of secondary palermoite and bertossaite; and (4) the replacement of secondary triphylite, montebrasite, palermoite and bertossaite by later phases (apatites, ludlamite, anapaite, augelite and fine-grained muscovite) reflect the leaching of Li back into hydrothermal fluids. The re-enrichment of Li during the post-magmatic stage most likely increased the solubility of Ta in the hydrothermal fluids of the granitic pegmatite.

This introduction outlines the papers collected in the special issue “Mesozoic magmatism and mineralization in Southeastern China”. These papers focus on the spatiotemporal distributions, petrogenesis, geochronology, mineralization and tectonic settings of the Mesozoic granitic rocks in SE China, and they represent the new research progress and further understanding on the granitic magmatism and associated mineralization. After the overview of the all papers, we propose the insights for future studies on the granitoids and associated mineralization in SE China.

In the pursuit of understanding the aqueous chemistry of oxythioarsenites (i.e., H 3 AsO 2 S and H 3 AsOS 2 ) on a microscopic scale, first principles molecular dynamics (FPMD) simulations were performed to investigate the hydration structures, acidity constants, and metal-complexing properties of these species in aqueous solutions at temperatures up to 573 K. The simulations showed that the oxythioarsenite species are stable and have trigonal pyramidal structures in both low- and high-temperature fluids. Their solvated structures were characterized in detail and it was found that the S or H atoms of the SH ligands form very weak H-bonds with the solvating water molecules and the OH ligands form H-bonds with water as both donors and acceptors. Furthermore, the dangling S or O sites act as strong acceptors to form H-bonds. Their acidity constants were calculated by using the FPMD-based vertical energy gap method. Together with our previous work (Liu et al., 2015, Chemical Geology , 411, 192–199), we found that in the arsenite-thioarsenite series (i.e., H 3 AsO 3 − x S x for x varying from 0 to 3), the p K a values of the oxythioarsenite species (H 3 AsO 2 S and H 3 AsOS 2 ) were always located between those of the end members, H 3 AsO 3 and H 3 AsS 3 , and decreased with the increasing temperature up to 573 K. Based on the calculated acidity constants, the speciation versus pH distributions were obtained at temperatures ranging from ambient temperature to 573 K. It was found that both H 2 AsO 2 S − and H 2 AsOS 2 − are the predominant species at near neutral pH for H 3 AsO 2 S and H 3 AsOS 2 species, respectively. In addition, the structures and the dissociation free energy of the oxythioarsenite-metal complexes at 573 K indicated that these As-S moieties are effective ligands for complexing with ore-forming metals in geological fluids.

The Nanling and adjacent regions of South China host a series of tin deposits related to Mesozoic granites with diverse petrological characteristics. The rocks are amphibole-bearing biotite granites, or (topaz-) albite-lepidolite (zinnwaldite) granites, and geochemically correspond to mealuminous and peraluminous types, respectively. Mineralogical studies demonstrate highly distinctive and critical patterns for each type of granites. In mealuminous tin granites amphibole, biotite and perthite are the typical rock-forming mineral association; titanite and magnetite are typical accessory minerals, indicating high f O2 magmatic conditions; cassiterite, biotite and titanite are the principal Sn-bearing minerals; and pure cassiterite has low trace-element contents. However, in peraluminous tin granites zinnwaldite-lepidolite, K-feldspar and albite are typical rock-forming minerals; topaz is a common accessory phase, indicative of high peraluminity of this type of granites; cassiterite is present as a uniquely important tin mineral, typically rich in Nb and Ta. Mineralogical distinction between the two types of tin granites is largely controlled by redox state, volatile content and differentiation of magmatic melts. In oxidized metaluminous granitic melts, Sn4+ is readily concentrated in Ti-bearing rock-forming and accessory minerals. Such Sn-bearing minerals are typical of oxidized tin granites, and are enriched in granites at the late fractionation stage. In relatively reduced peraluminous granitic melts, Sn2+ is not readily incorporated into rock-forming and accessory minerals, except for cassiterite at fractionation stage of granite magma, which serves as an indicator of tin mineralization associated with this type of granites. The nature of magma and the geochemical behavior of tin in the two types of granites thus result in the formation of different types of tin deposits. Metaluminous granites host disseminated tin mineralization, and are locally related to deposits of the chlorite quartz-vein, greisen, and skarn types. Greisen, skarn, and quartz-vein tin deposits can occur related to peraluminous granites, but disseminated mineralization of cassiterite is more typical.

Mengxianminite, ideally Ca 2 Sn 2 Mg 3 Al 8 [(BO 3 )(BeO 4 )O 6 ] 2 , is a new borate mineral from Xianghualing skarn, Hunan Province, southern China. It occurs in the hsianghualite vein of Xianghualing skarn, associated with fluorite, phlogopite, hsianghualite, magnetite, dravite, magnesiotaaffeite-2 N ′2 S , and calcite. Mengxianminite forms subhedral to euhedral green crystals from 20 to 200 μm long, translucent to transparent, with a vitreous luster. The crystals show perfect cleavage on {100} and good cleavage on {010}, and do not fluoresce in long- or short-wave ultraviolet light. The estimated Mohs hardness is 8, and the tenacity is brittle with irregular fracture. The calculated density is 4.170 g/cm 3 . Optically, mengxianminite is biaxial (−), with α = 1.80(2), β = 1.83(2), γ = 1.84(2) (589 nm). The mean chemical composition of mengxianminite is Al 2 O 3 40.00, SnO 2 25.96, MgO 6.57, CaO 8.56, FeO 4.83, B 2 O 3 6.53, BeO 4.37, ZnO 1.81, MnO 1.23, Na 2 O 1.13, TiO 2 0.10, SiO 2 0.04, sum 101.12 with a corresponding empirical formula calculated on the basis of 26 O atoms of (Ca 1.64 ,Na 0.39 ) ∑2.03 (Sn 1.85 ,Zn 0.24 ) ∑2.09 (Mg 1.75 , Fe 0.72 ,Al 0.42 ,Mn 0.19 ,Ti 0.01 ) ∑3.09 Al 8 [(B 1.01 O 3 )(Be 0.94 O 4 )O 6 ] 2 . (Be and B were measured by secondary ion mass spectrometry, average of six electron microprobe analyze points and in wt%.) The strongest eight lines of the powder XRD pattern [ d in A ( I )( hkl )] are: 3.000 (35)(16.2.0); 2.931 (100)(17.1.1); 2.475 (29)(022); 2.430 (30)(13.3.1); 2.375 (100)(14.0.2/640); 2.028 (52)(21.3.1); 1.807 (35)(913); 1.530 (98)(14.6.0/15.3.3). Mengxianminite is orthorhombic, space group Fdd 2; unit-cell parameters refined from single-crystal X-ray diffraction data are: a = 60.699(4), b = 9.914(1), c = 5.745(1) A, V = 3457.4(4) A 3 , and Z = 8. The structure of mengxianminite is characterized by the alternating O-T1-O-T2-O′-T2 layers stacked along the a axis, which are equal to two alternating modules: the module A (O-T1-O) corresponding to the spinel module with an additional O layer (AlO 6 octahedra layer), and the module B (T2-O′-T2) showing the simplified formula CaSnAl(BeO 4 )(BO 3 ), where SnO 6 octahedra are isolated in the T2 layers, connected via BeO 4 and CaO 11 groups, and AlO 6 edge-sharing octahedra in the O′ layer form chains running along the {011} or {011} direction, connected in the c direction by the BO 3 triangular groups. Mengxianminite is the first borate mineral with both Sn and Be, likely crystallized under F-rich conditions at late stages of the Xianghualing skarn.

The Himalayan leucogranite occurs as two extensive (>1000 km) E-W trending belts on the Tibetan Plateau with the unique features. The leucogranite comprised biotite granite, two-mica/muscovite granite, tourmaline granite and garnet granite, which have been identified in previous studies, as well as albite granite and granitic pegmatite that were identified in this investigation. Fifteen leucogranite plutons were studied and 12 were found to contain rare-metal bearing minerals such as beryl (the representative of Be mineralization), columbite-group minerals, tapiolite, pyrochlore-microlite, fergusonite, Nb-Ta rutile (the representative of Nb-Ta mineralization), and cassiterite (the representative of Sn mineralization) mainly based on the field trip, microscope observation and microprobe analysis. The preliminary result shows that the Himalayan leucogranite is commonly related to the rare-metal mineralization and warrants future investigation. Further exploration and intensive research work is important in determining the rare-metal resource potential of this area.

We report on the petrography and mineralogy of three types of silicate veinlets in the brecciated eucrite Northwest Africa (NWA) 1109. These include Fe-rich olivine, Mg-rich olivine, and pyroxene veinlets. The Fe-rich olivine veinlets mainly infill fractures in pyroxene and also occur along grain boundaries between pyroxene and plagioclase crystals, in both nonequilibrated and equilibrated lithic clasts. The host pyroxene of Fe-rich olivine veinlets shows large chemical variations between and within grains. The Fe-rich olivine veinlets also contain fine-grained Fe3+-bearing chromite, highly calcic plagioclase, merrillite, apatite, and troilite. Based on texture and mineral chemistry, we argue that the formation of Fe-rich olivine was related to fluid deposition at relatively high temperatures. However, the source of Fe-rich olivine in the veinlets remains unclear. Magnesium-rich olivine veinlets were found in three diogenitic lithic clasts. In one of these, the Mg-rich olivine veinlets only occur in one of the fine-grained interstitial regions and extend into fractures within surrounding coarse-grained orthopyroxene. Based on the texture of the interstitial materials, we suggest that the Mg-rich olivine veinlets formed by shock-induced localized melting and recrystallization. Pyroxene veinlets were only observed in one clast where they infill fractures within large plagioclase grains and are associated with fine-grained pyroxene surrounding coarse-grained pyroxene. The large chemical variations in pyroxene and the fracture-filling texture indicate that the pyroxene veinlets might also have formed by shock-induced localized melting and rapid crystallization. Our study demonstrates that silicate veinlets formed by a range of different surface processes on the surface of Vesta.

Fe-As mineral solubility and associated aqueous species have been intensively studied because of the environmental need to immobilize arsenic. The thermodynamic data for aqueous iron-arsenic species are inadequately characterized, however. The Gibbs free energy, enthalpy, entropy, and heat capacity and activity coefficients were refined in the Fe(II)-Fe(III)-As(V)-HClO4-H2O and Fe(II)-Fe(III)-As(V)-HCl-H2O systems using redox potential measurements from 5 to 90 °C. The association constants for FeHAsO4+ and FeH2AsO42 + at 25 °C were 1010.28 and 104.02 and the corresponding association reaction enthalpies and heat capacities were 25.74 and 8.73 kJ mol− 1 and 843.1 and − 529.6 J K −1mol− 1, respectively. Activity coefficients for H+, ClO4−, Fe2 +, Fe3 +, HAsO42 −, and H2AsO4− at 25 °C in the form of the Huckel equation were derived for ionic strengths up to 1 mol− 1 kg− 1. Newly derived activity coefficients and thermodynamic data were incorporated into PHREEQCI to calculate the Eh of laboratory solutions. The differences between calculated and measured Eh were all within 10 mV and relative differences were all lower than 1.5%.

International audience; The Middle-Late Jurassic Cu-Pb-Zn-bearing and W-bearing granites in the Nanling Range have distinctly different mineralogical and geochemical signatures. The Cu-Pb-Zn-bearing granites are dominated by metaluminous amphibole-bearing granodiorites, which have higher CaO/(Na2O+K2O) ratios, light/heavy rare earth element (LREE/HREE) ratios, and δEu values, lower Rb/Sr ratios, and weak Ba, Sr, P, and Ti depletions, exhibiting low degrees of fractionation. The W-bearing granites are highly differentiated and peraluminous, and they have lower CaO/(Na2O+K2O) ratios, LREE/HREE ratios, and δEu values, higher Rb/Sr ratios, and strong Ba, Sr, P, and Ti depletions. The Cu-Pb-Zn-bearing granites were formed predominantly between 155.2 and 167.0 Ma with a peak value of 160.6 Ma, whereas the W-bearing granites were formed mainly from 151.1 to 161.8 Ma with a peak value of 155.5 Ma. There is a time gap of about 5 Ma between the two different types of ore-bearing granites. Based on detailed geochronological and geochemical studies of both the Tongshanling Cu-Pb-Zn-bearing and Weijia W-bearing granites in southern Hunan Province and combined with the other Middle-Late Jurassic Cu-Pb-Zn-bearing and W-bearing granites in the Nanling Range, a genetic model of the two different types of ore-bearing granites has been proposed. Asthenosphere upwelling and basaltic magma underplating were induced by the subduction of the palaeo-Pacific plate. The underplated basaltic magmas provided heat to cause a partial melting of the mafic amphibolitic basement in the lower crust, resulting in the formation of Cu-Pb-Zn mineralization related granodioritic magmas. With the development of basaltic magma underplating, the muscovite-rich metasedimentary basement in the upper-middle crust was partially melted to generate W-bearing granitic magmas. The compositional difference of granite sources accounted for the metallogenic specialization, and the non-simultaneous partial melting of one source followed by the other brought about a time gap of about 5 Ma between the Cu-Pb-Zn-bearing and W-bearing granites.

Aiming at an atomistic mechanism of heavy metal cation complexing on clay surfaces, we carried out systematic first principles molecular dynamics (FPMD) simulations to investigate the structures, free energies and acidity acidity constants of Ni(II) complexes formed on edge surfaces of 2:1 phyllosilicates. Three representative complexes were studied, including monodentate complex on the SiO site, bidentate complex on the Al(OH)2 site, and tetradentate complex on the octahedral vacancy where Ni(II) fits well into the lattice. The complexes structures were characterized in detail. Computed free energy values indicate that the tetradentate complex is significantly more stable than the other two. The calculated acidity constants indicate that the tetradentate complex can get deprotonated (pKa = 8.4) at the ambient conditions whereas the other two hardly deprotonate due to extremely high pKa values. By comparing with the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) model, the vacant site has been assigned to the strong site and the other two to the weak site, respectively. Thus a link has been built between atomistic simulations and macroscopic experiments and it is deduced that this should also apply to other heavy metal cations based on additional simulations of Co(II) and Cu(II) and previous simulations of Fe(II) and Cd(II)). This study forms a physical basis for understanding the transport and fixation of heavy metal elements in many geologic environments.