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关键词： Quartz  

摘要： The Dabaoshan polymetallic deposits in the Nanling Range, South China, consist of porphyry and skarn-type Mo mineralization genetically related to Jurassic porphyritic intrusions and adjacent strata-bound Cu-Pb-Zn mineralization hosted in mid-Devonian limestone. Porphyry Mo mineralization is characterized by the superposition of multiple generations of crosscutting quartz-bearing veins including: barren quartz veins (V1), quartz-molybdenite veins with K-feldspar alteration halos that host the bulk of the Mo mineralization (V2), quartz-pyrite veins with muscovite alteration (V3), and late base metal mineralization with argillic alteration (V4), as well as limestone-hosted strata-bound Cu-Pb-Zn mineralization (VS). Fluid inclusion petrography and microthermometry combined with cathodoluminescent textures and trace elements in quartz reveal changes in pressure and temperature of the hydrothermal system that formed the deposit. V1 and V2 veins are dominated by low-salinity (1-6 wt % NaCl equiv), CO2-bearing (4-10 mol %) two-phase inclusions with about 35 vol % bubble trapped in the one-phase field above the solvus of the fluid. V1 veins are dominated by CL-bright granular quartz mosaics with higher CL intensity than any other vein type. This quartz also contains more Ti than any other vein generation (24-89 ppm), while Al, Ge, and Li concentrations overlap with other vein generations. Molybdenum ore-hosting V2 veins are also dominated by CL-bright granular quartz mosaics, but V2 veins display slightly less CL intensity and correspondingly lower Ti concentrations (10-65 ppm). V3 veins have a broader spatial distribution than V1 and V2 veins, extending from inside the porphyries out into the adjacent limestone. These veins are also dominated by low-salinity (2-6 wt % NaCl equiv), CO2-bearing (4-7 mol %) two-phase inclusions, these containing about 45 vol % bubble trapped above their solvus. V3 veins are dominated by CL-dark quartz with euhedral growth zones of oscillating

关键词： Carbocernaite   carbonatite   isotopic composition   rare earth elements   crystal structure   zoning   Bear Lodge   Wyoming  

摘要： Zoned crystals of carbocernaite occur in hydrothermally reworked burbankite-fluorapatite-bearing calcite carbonatite at Bear Lodge, Wyoming. The mineral is paragenetically associated with pyrite, strontianite, barite, ancylite-(Ce), and late-stage calcite, and is interpreted to have precipitated from sulfate-bearing fluids derived from an external source and enriched in Na, Ca, Sr, Ba, and rare-earth elements (REE) through dissolution of the primary calcite and burbankite. The crystals of carbocernaite show a complex juxtaposition of core-rim, sectoral, and oscillatory zoning patterns arising from significant variations in the content of all major cations, which can be expressed by the empirical formula (Ca0.43-0.91Sr0.40-0.69REE0.18-0.59Na0 18-0.53Ba0-0.08)(Sigma 1.96-2.00)(CO3)(2). Interelement correlations indicate that the examined crystals can be viewed as a solid solution between two hypothetical end-members, CaSr(CO3)(2) and NaREE(CO3)(2), with the most Na-REE-rich areas in pyramidal (morphologically speaking) growth sectors representing a probable new mineral species. Although the Bear Lodge carbocernaite is consistently enriched in light REE relative to heavy REE and Y (chondrite-normalized La/Er = 500-4200), the pyramidal sectors exhibit a greater degree of fractionation between these two groups of elements relative to their associated prismatic sectors. A sample approaching the solid-solution midline [(Ca0.57Na0.42)(Sigma 0.99)(Sr0.50REE0.47Ba0.01)(Sigma 0 98)(CO3)(2)] was studied by single-crystal X-ray diffraction and shown to have a monoclinic symmetry [space group P11m, a = 6.434(4), b = 7.266(5), c = 5.220(3) angstrom, gamma = 89.979(17)degrees, Z = 2] as opposed to the orthorhombic symmetry (space group Pb2(1)m) proposed in earlier studies. The symmetry reduction is due to partial cation order in sevenfold-coordinated sites occupied predominantly by Ca and Na, and in tenfold-coordinated sites hosting Sr, REE, and Ba. The ordering also causes splitti

关键词： island arc magmatism   partial melting   slab components   Louisville seamounts   Tonga arc   high field strength elements  

摘要： We present a new comprehensive isotope and trace element dataset for north and central Tongan lavas including high-precision High Field Strength Element measurements. The emphasis of our study is on lavas from the northernmost volcanic islands of Tafahi and Niuatoputapu that exhibit unique compositions compared with other Tongan volcanoes, in particular elevated high-precision Nb/Ta ratios as high as similar to 28. These lavas are extremely depleted in incompatible, fluid-immobile elements such as Ti, Zr, Sc and Yb, suggesting about 6% depletion of their mantle wedge source relative to average upper mantle prior to 20-30% partial melting. The extremely depleted mantle wedge was re-enriched in highly incompatible elements including Nb and Ta from the subducting slab. Three slab components-fluids from altered oceanic crust, pelagic sediments, and Louisville Seamount Chain lavas-have contributed to the source region of the magmas. A fluid from the subducted Louisville lavas has been added after the other two slab components and has radiogenic Pb-206/Pb-204. Components from the altered oceanic crust and Louisville sea-mounts exhibit little Nb/Ta fractionation, as demonstrated by the nearly uniform and mid-ocean ridge basalt-like Nb/Ta ratios. We suggest that the apparently large slab fluid flux beneath Tafahi and Niuatoputapu results from focused flow through subducting Louisville Seamount crust that had no or little sediment cover, allowing the fluids to pass through the subducting lithosphere more efficiently. Thus, the high Nb/Ta ratios indicate that the Louisville-derived fluids had probably equilibrated with residual rutile. Our results imply that significant amounts of Nb and Ta can be mobilized from distinct subducting oceanic lithologies-a process that may probably also operate beneath other island arcs. We propose a model in which the appearance of the subducted seamount signatures some 3-4Myr after their actual subduction is explained by storage in shallow met

摘要： The highly organized morphogenesis of bird feathers holds important phylo-and ontogenetic information on the evolution of birds, organogenesis, tissue regeneration, and the health status of individual animals. Altered topobiological patterns are regularly used as retrospective evidence for disturbed developmental trajectories due to the past exposure to environmental stressors. Using the most advanced high-resolution (5-70 mu m) X-ray fluorescence microscopy (XFM), we describe in the feathers from three species of Procellariiformes hitherto unknown, depositions of elements (Zn, Ca, Br, Cu, Fe) that are independent of pigmentation or any underlying variation in density or polymer structure. In the case of Zn, the pattern across several species of Procellariiformes, but not other species, consisted of highly regular bands of Zn numbering 30-32, which may reflect the estimated number of days of active feather growth or the duration of the moult period. Thus, speculatively, the highly consistent Zn pattern might be the result of a so far unknown diurnal systemic regulation rather than local heterogeneity amongst the follicular stem cells.

关键词： scientific community   chemical elements   pyrolysis   Elements   Chlorine   Fate   Pyrolysis products   resource recovery   Biomass   renewable resource  

摘要： Biomass is increasingly perceived as a renewable resource rather than as an organic solid waste today, as it can be converted to various chemicals, biofuels, and solid biochar using modern processes. In the past few years, pyrolysis has attracted growing interest as a promising versatile platform to convert biomass into valuable resources. However, an efficient and selective conversion process is still difficult to be realized due to the complex nature of biomass, which usually makes the products complicated. Furthermore, various contaminants and inorganic elements (e.g., heavy metals, nitrogen, phosphorus, sulfur, and chlorine) embodied in biomass may be transferred into pyrolysis products or released into the environment, arousing environmental pollution concerns. Understanding their behaviors in biomass pyrolysis is essential to optimizing the pyrolysis process for efficient resource recovery and less environmental pollution. However, there is no comprehensive review so far about the fates of chemical elements in biomass during its pyrolysis. Here, we provide a critical review about the fates of main chemical elements (C, H, O, N, P, Cl, S, and metals) in biomass during its pyrolysis. We overview the research advances about the emission, transformation, and distribution of elements in biomass pyrolysis, discuss the present challenges for resource-oriented conversion and pollution abatement, highlight the importance and significance of understanding the fate of elements during, pyrolysis, and outlook the future development directions for process control. The review provides useful information for developing sustainable biomass pyrolysis processes with an improved efficiency and selectivity as well as minimized environmental impacts, and encourages more research efforts from the scientific communities of chemistry, the environment, and energy.

关键词： Acac   Adsorption   Chemical immobilization   PAN   Resource recovery  

摘要： This study was aimed at the investigation of Rare Earth Element (REE) recovery from aqueous solution by silica gels with 1-(2-Pyridylazo) 2-naphthol (PAN) and acetyl acetone (Acac) modifications. The two different methods of silica gel chelation, such as chemical immobilization with the help of silane coupling agents (3-aminopropyl triethoxysilane (APTES) and 3-aminopropyl trimethoxysilane (APTMS) in this study) and direct physical adsorption onto the silica surface, is compared in terms of their REE removal efficiency. A comparative analysis between adsorption of different REEs for different silica gels is performed and the influence of parameters such as pH, contact time, temperature and initial concentration has been reported. The effect of calcined adsorbents on the adsorption process is also investigated. Characterization studies on silica gels by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and zeta potential analysis are performed to better understand the relation between physical/chemical attributes of the adsorbents and their impact on the adsorption process. The experimental results are evaluated and optimal conditions for REE adsorption are identified. Chemically immobilized gels demonstrated immense potential for all the REE under study except Sc, for which, physically, loaded gels seemed to be more efficient. The removal of REEs could be achieved at lower pHs by chemically immobilized PAN/Acac gels, making it suitable for many practical applications. The amine functionalized gels before chemical immobilization step were compared with PAN/Acac chemically immobilized gels in single as well as multi element system and the significance of chemical immobilization after amine functionalization is also stated. (C) 2017 Elsevier Ltd. All rights reserved.