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Nowadays, microfluidic synthesis has many advantages over bulk synthesis. By controlling the flow into the microfluidic chip, we can synthesize nanoparticles with defined and precise characteristics. A continuous microfluidics synthesis of CaWO4 was conducted to obtain nanoparticles with a Scheelite structure approximately 10 nm in diameter. The CaWO4 nanoparticles were characterized using elemental composition, chemical structure, particle size distribution, and morphology. Calcium tungstate and its derivatives are well known for their optical properties and have great potential for medical applications. The small diameter of nanoparticles allows the synthesis of composites on their basic for theranostics in cancer treatment. Our work indicates the potential opportunity of a continuous microfluidics technique for the rapid fabrication of Scheelite-type tungstate. Microfluidic synthesis of CaWO4 nanoparticles with a Scheelite structure using a continuous process yielding 10 nm particles. Characterization includes elemental composition, structure, and morphology. This substance has potential applications in photodynamic therapy because of its optical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The origin of newly discovered quartz vein-type W mineralization is confirmed. • The redox conditions of fluids and multistage ore-forming process are revealed. • Vein-type W mineralization occur at proximal and distal part in skarn W system. The Xintianling deposit is one of the largest skarn-type scheelite deposit in China. Recent discoveries of quartz-vein-type scheelite mineralization within the deposit have raised questions about its origin and the evolution of ore-forming fluids, hindering a comprehensive understanding of the ore-forming process. We investigate the microtextures, trace elements, and oxygen isotope compositions of scheelite from different stages in both skarn-type and quartz-vein-type W mineralizations. Combined with apatite geochemistry and U–Pb dating, we determine the timing of quartz-vein-type mineralization and the evolution of magmatic-hydrothermal system. Based on detailed petrological observation, three types (seven subtypes) of scheelite and two types of apatite are identified. The Mo contents and Eu/Eu* ratios of scheelite, along with the Ce/Ce* ratios of apatite indicate the oxygen fugacity of fluids during the skarn metallogenic episode is generally higher than that during the quartz-vein metallogenic episode. Furthermore, the Y/Ho ratios and REE patterns of scheelite indicate the presence of at least three significant stages of fluid influx and fluid-rock interactions throughout entire ore-forming process. The O isotope compositions of scheelite in the quartz-vein-type metallogenic episode reveal that the ore-forming fluids are originated from a magmatic source, and meteoric water was mixed into the system, leading to the precipitation of the latest stage of scheelite. The apatites closely coexist with scheelite, from the early and the late stages of quartz-vein metallogenic episode, yield consistent U–Pb ages within error of 160.4 ± 2.4 Ma and 158.4 ± 1.3 Ma, respectively, indicating a close genetic link between quartz-vein-type W mineralization and the fine-grained porphyritic biotite granite. Our study highlights the significance of pulsed fluid exsolution and the combined effects of multiple mechanisms, including fluid-rock interaction, fluid mixing, and physicochemical condition changes, in the formation of large W deposits. [ABSTRACT FROM AUTHOR]

Nowadays, microfluidic synthesis has many advantages over bulk synthesis. By controlling the flow into the microfluidic chip, we can synthesize nanoparticles with defined and precise characteristics. A continuous microfluidics synthesis of CaWO4 was conducted to obtain nanoparticles with a Scheelite structure approximately 10 nm in diameter. The CaWO4 nanoparticles were characterized using elemental composition, chemical structure, particle size distribution, and morphology. Calcium tungstate and its derivatives are well known for their optical properties and have great potential for medical applications. The small diameter of nanoparticles allows the synthesis of composites on their basic for theranostics in cancer treatment. Our work indicates the potential opportunity of a continuous microfluidics technique for the rapid fabrication of Scheelite-type tungstate. Microfluidic synthesis of CaWO4 nanoparticles with a Scheelite structure using a continuous process yielding 10 nm particles. Characterization includes elemental composition, structure, and morphology. This substance has potential applications in photodynamic therapy because of its optical properties. [ABSTRACT FROM AUTHOR]

This study examines the low‐loss and temperature‐stable Na2O–Ln2O3–MoO3–TiO2 (Ln = Nd, La and Ce) system, synthesized via a solid‐state process at low‐sintering temperatures ranging from 840°C to 900°C The structure, microstructure and microwave properties of the Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce) ceramics as a function of the sintering temperature were studied. The results of XRD patterns and microstructure characterization showed that the main phase in compositions belong to tetragonal scheelite and tetragonal structure. The ceramic composition Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce), sintered at 840°C–900°C for 2 hours, demonstrated excellent microwave dielectric properties, exhibiting relative dielectric constant (εr) of 13.9–14.4, Q × f value of about 31 100 (at 9.66 GHz) – 48 600 GHz (at 9.33 GHz), and temperature coefficient of –8.1 to –1 ppm/°C. Our work designs temperature‐stable microwave dielectric ceramics with low‐sintering temperature for LTCC technology applications. [ABSTRACT FROM AUTHOR]

The Xiaoqinling gold province, located in the Neoarchean-Paleoproterozoic uplifted footwalls of the Xiaoqinling metamorphic core complex (XMCC), is one of China's largest gold producers; however, achieving a consensus regarding their metallogenic model remains elusive. Scheelite is an indicator mineral that commonly occurs in lode gold deposits worldwide used to recognize deposit types and understand hydrothermal evolution and the origin of features. Xenotime, monazite, and rutile are common hydrothermal minerals in association with lode gold deposits worldwide. Here, we provide textual, in situ U-Pb geochronology of xenotime, monazite, and rutile, and in situ elemental and Sr-Nd isotopic compositions of scheelite within different stages from the large Yangzhaiyu lode gold deposit, aiming to elucidate its genesis and, for the first time, establish a holistic correlation between the lode gold mineralization and the evolution of the XMCC. Notably low eNd(t) values (-30.7 to -23.7), high 87Sr/86Sr ratios (0.72659-0.75914), and distinct rare earth elements, Sr, Mo, and As contents of scheelite confirm a metamorphic crustal source. Xenotime U-Pb dating and pre-ore (Stage I) scheelite reveal that ore-barren metamorphic fluids at ca. 140 Ma were oxidized with low Bi contents and buffered by greenschist facies metamorphism when the XMCC initiated. Monazite and rutile U-Pb dating combined with ore-stage scheelite geochemistry indicate a compositional shift in the more reduced auriferous metamorphic fluids, which dominated during major gold deposition periods (stages II and III) from 130 Ma to 120 Ma, characterized by significantly depleted Na and increased Bi contents. This resulted from the prograde greenschist-to-amphibolite metamorphism at mid-lower crustal depths as the result of the XMCC isostatic doming and the lithospheric mantle thinning after 130 Ma. This study highlights the crucial role of metamorphic core complexes in governing the timing, locations, and resources of the lode gold metallogenic system. [ABSTRACT FROM AUTHOR]

Porphyry copper deposits are economically significant sources of Cu and Mo, formed when metal-rich fluids precipitate at shallow levels, exsolving from underlying magmatic reservoirs at depth. However, the origin and evolution of these metal-rich fluids, whether through episodic enrichment from multiple pulses or a single continuous fluid-release event, remain a subject of controversy. To gain deeper insights into these processes, data on cathodoluminescence (CL) imaging, in situ trace elements, and Sr isotopes of newly discovered scheelite (Sch 1, Sch 2, and Sch 3) found in three generations of vein types within the giant Qulong porphyry Cu-Mo mineralization system are presented. The anhedral Sch 1 occurs in quartz + magnetite + anhydrite + chalcopyrite veins, exhibiting no obvious zoning in the CL image. These scheelite samples show high concentrations of Mo, Nb, Ta, and 87Sr/86Sr ratios ranging from 0.70688 to 0.71109. Moreover, they demonstrate enriched rare earth elements (REE) and negative Eu anomalies in the chondrite-normalized pattern, indicative of their formation in relatively oxidized metal-rich fluids during the early high-temperature alteration stage. Among the discovered scheelite varieties, the most volumetrically significant is the subhedral Sch2, which occurs in veins composed of quartz + pyrite + chalcopyrite. In its central region (Sch 2a), Cu-rich cores are dispersed, surrounded by an oscillatory Cu-poor mantle and rim (Sch 2b and 2c), as observed in the CL image. When compared to Sch 1, Sch 2 exhibits lower levels of REE, Nb, Ta, Mo, and 87Sr/86Sr ratios (ranging from 0.70502 to 0.70578), but higher Cu concentration and positive Eu anomalies. The gradual decrease in Cu content from the core to rim in Sch2, along with its rim's intergrowth with sulfide, suggests the precipitation of Cu during the second pulse of fluids. Euhedral Sch 3 is found in relatively moderate-temperature mineral assemblages within quartz + galena + sphalerite + molybdenite veins. It displays an oscillatory pattern with a Mo-rich core (Sch 3a), an extremely Mo-rich mantle (Sch 3b), and a Mo-poor rim (Sch 3c) in the CL image. Sch 3 shows lower REE, Cu, and Pb contents but variable Mo concentrations in different domains while consistently recording 87Sr/86Sr ratios ranging from 0.70498 to 0.70542. These characteristics indicate the precipitation process of Mo and Pb during the third pulse of fluid evolution. The observed shift in mineral assemblages, metal contents, and Sr isotopic components from Sch 1 to Sch 3 reflects the occurrence of different fluid pulses within a cooling porphyry Cu-Mo mineralization system. Overall, the three generations of scheelite found at the Qulong porphyry Cu-Mo deposit indicate the occurrence of multiple pulsed flows of magmatic fluids, revealing a more complex fluid evolution for porphyry Cu deposits than previously recognized. Notably, Sch 1 exhibits relatively high 87Sr/86Sr ratios, similar to the post-ore mafic porphyries, which are higher compared to Sch 2 and Sch 3, showing 87Sr/86Sr ratios similar to the pre- and syn-ore host granite and porphyry. This result implies that mafic magma has significantly contributed to the formation of the first pulse of magmatic fluids, whereas synore granitic magma contributed to the ore fluids responsible for forming the veins containing Sch 2 and Sch 3 in the later stage. Therefore, we propose that volatiles from mafic magma, injected into the porphyry metallogenic system, play a crucial role in the formation of porphyry Cu deposits. Additionally, for the first time, the presence of Cu-Mo-W metal endowment in the porphyry Cu deposits of the Gangdese magmatic belt is identified, providing valuable new insights into the metallogeny of porphyry Cu deposits and offering promising opportunities for tungsten exploration in the collision zone. [ABSTRACT FROM AUTHOR]

We report a detailed study about the correlation between the physicochemical properties of solvothermally synthesized pristine and 1 %, 2.5 %, and 5 % Cu, Mo, and W-doped bismuth vanadate (BiVO 4 , BVO) with its phase composition. The effect of the dopant and the duration of synthesis (8 h and 20 h) on the physicochemical properties of BVO allowed us to tune the ratio of monoclinic scheelite to tetragonal zircon phase in BVO powders. This approach helped us to establish the relationship between the presence of monoclinic scheelite or tetragonal zircon phase with structural, morphological and optical properties of BVO powders, obtained by different physicochemical methods (e.g. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence spectroscopy (PL)). The results indicated that, in addition to XRD, Raman, and DRS, several other methods could distinguish between the two phases. For example, SEM analysis revealed that monoclinic scheelite BVO exhibits either elongated assemblies of cube-like particles or prismatic particles with sizes ∼500 nm. In contrast, tetragonal zircon BVO exclusively exhibited porous spherical particles with diameter ∼2 μm. DRS and Raman spectroscopy indicated that there is a possibility of distinguishing between the two phases if their shares are large enough. For instance, monoclinic BVO showed band gap values in the range of 2.35–2.52 eV, while tetragonal zircon BVO exhibited values in the range of 2.80–3.00 eV. XPS showed a correlation between phase composition and surface chemistry of BVO only for Cu-doped samples, revealing the presence of Cu+ in monoclinic BVO and the presence of both Cu+ and Cu2+ in tetragonal zircon BVO. PL showed that monoclinic scheelite BVO displayed decreased charge recombination compared to tetragonal zircon BVO. Deeper insight into the correlation between the physicochemical properties and phase composition of Cu, Mo, and W-doped bismuth vanadate (BiVO 4 , BVO) was based on water/pentanol medium (2:1 vol%) as a novel synthesis pathway. This may open new avenues for the broader methodological exploration of surface chemistry, particle size, and morphology of BVO particles through the use of diverse functionalization agents. Finally, the established links between phase composition and structural, morphological, and other physicochemical properties provide new and more predictable opportunities for further improvement of BVO properties for various applications. [Display omitted] • Numerous characterization methods elucidate BiVO 4 structure-property relationship • Solvothermal synthesis in water-pentanol offers novel pathways for BiVO 4 engineering • Our study surpasses literature by detailing BiVO 4 synthesis and characterization • Experimental parameters govern the formation of BiVO 4 phases with distinct properties • Identified correlations provide a predictable route to enhance BiVO 4 properties [ABSTRACT FROM AUTHOR]

In this study we illustrate the structural, electronic and optical integrity of Ca 1- x Sm (2/3) x WO 4 (x = 0.00, 0.02, 0.04, 0.06 and 0.08) crystals for optoelectronic applications via experimental and first principles approach. According to our experimental outcomes, CaWO 4 crystallizes in scheelite type tetragonal structure devoid of impurity which depends on the A-site cationic radius and dopant-host compatibility. As a result, the dopant induced lattice distortion occur due to symmetric and asymmetric stretching of (Ca, Sm)—O and W–O bonds within [CaO 8 ] and [WO 4 ] cluster. According to our FT-IR and Raman spectral analysis, the non-centrosymmetric vibration within the [WO 4 ]2- complex gives rise to internal modes while the Ca2+/Sm3+ cationic displacement and rigid molecular ionic group constitutes the external modes which equally impacts the electronic and optical characteristics of the host material. While the forbidden gap extends due to Sm3+ substitution, the delocalization of W-5d orbitals on the other hand occur due to rising distortions within the WO 4 cluster. As a result, the polarization between [WO 4 ] and [CaO 8 ] cluster and difference in the electronic transitions controls the optical characteristics of the host material. According to our experimental and theoretical predictions, a noticeable decrease in the optical band gap (5.96–5.83 eV) occurs due to heterovalent cationic substitution (Sm3+), difference in structural order-disorder and charge carrier density. As a result, a broad photoluminescence (PL) spectrum among acceptor doped samples verifies the impact of multi-phonon or multi-level processes on the luminosity of the host material. [ABSTRACT FROM AUTHOR]

Baoshan is a world-class skarn Cu-polymetallic deposit located at the junction of the Nanling and Qin-Hang metallogenic belts in China. While there has been extensive research on the mineralogy and geochemistry of skarn deposits, studies on the fluid characteristics and evolutionary history from the early to late skarn stages in such deposits are still limited. In this study, we analyzed garnet and pyroxene from the early skarn stage and scheelite from the late skarn stage of the Baoshan deposit. We distinguished two generations of garnet (Grt1 and Grt2), one generation of pyroxene, and three generations of scheelite (Sch I, Sch II, and Sch III) on the basis of mineral assemblages and microscopic characteristics. Grt1 appears coarse-grained, and Grt2 cuts through Grt1 as veinlets. In Grt1, the andradite end-member increases from the core to the rim, while the grossular portion decreases (Ad35–36Gr59–61Sp3–4 to Ad59–61Gr36–37Sp2–3), and in Grt2, the andradite end-member significantly increases (Ad41–73Gr25–55Sp2–3). Grt1 and Grt2 have similar trace element compositions, with enrichment in Zr and depletion in Nb and Hf, depletion in LREE, enrichment in HREE, and weak negative Eu anomalies. Pyroxene coexists with Grt1 and is similarly cut by Grt2, with its composition mainly being diopside (Di82–99Hd0.6–15Jo0–3.2). Sch I and Sch II appear as anhedral to subhedral grains, while Sch III is predominantly found in veinlets. In Sch I and Sch II, most REEs enter the scheelite lattice via the Na-REE coupled substitution mechanism, with a smaller portion substituting Ca vacancies. In Sch III, the substitution mechanism involving Ca site vacancies may dominate. During the early skarn stage, the oxygen fugacity of the fluid gradually decreased from Grt1 and pyroxene to Grt2. In the late skarn stage, fluid oxygen fugacity remains stable from Sch I and Sch II to Sch III in shallow parts but significantly decreases in deeper parts. The garnet and pyroxene from the Baoshan deposit align with typical skarn Cu deposit compositions, while scheelite in the late skarn stage shows Sch I, Sch II, and shallow Sch III as skarn-type and deep Sch III as vein-type scheelite. Early skarn stage fluids were weakly acidic. Sch I, Sch II, and Sch III originated from fluids related to the Baoshan granite porphyry, with Sch III also showing evidence of water–rock interaction. This study reconstructed the fluid evolution history from the early to late skarn stages at the Baoshan deposit, providing insights into the ore-forming processes of other skarn deposits. [ABSTRACT FROM AUTHOR]

In this study, column flotation was used to recover a high-grade concentrate from low-grade WO3 ore. Gas dispersion properties, such as superficial gas velocity, gas holdup, bubble size, bubble surface area flux, carrying rate, and bias, were investigated in two phases (gas–liquid) and three phases (gas–liquid–solid) in the column, and their effects on the grade and recovery of WO3. It was confirmed that the gas velocity significantly affected these factors, with the gas holdup, bubble size, bubble surface area flux, and carrying rate tending to increase as the gas velocity increased. The bias increased with an increase in the wash water velocity. The results showed that the grade and recovery of WO3 could be controlled within a specific range of operating conditions of bias (0.27–0.48 cm/s) and carrying rate (10.53–18.83 g/min/cm2). Correlation plots of grade/recovery versus bias and carrying rate revealed that the optimal separation achievable for a given WO3 concentrate in a flotation column was a 72.16% grade with a 78.3% recovery, satisfying the metallurgical requirement of more than 50% for WO3. [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ U–Pb ages of garnet (∼203 Ma) and vesuvianite (∼145 Ma) indicate two stage skarnization at Nanyangtian. • Scheelite U–Pb ages of 141–146 Ma reveal an Early Cretaceous W mineralization event in SE Yunnan. • The age of 141–146 Ma is likely associated with the subduction of Paleo-Pacific plate. The Nanyangtian W deposit, located in the Laojunshan district, is the largest W deposit in southeastern Yunnan, China. However, before that, the mineralization age of this deposit is still controversial, since the absence of suitable dating minerals and methods. In this study, garnet and vesuvianite, the typical skarn minerals, and scheelite, the dominant ore mineral at Nanyangtian, were selected for LA–ICP–MS U–Pb dating to directly constrain the ages of skarn and W mineralization. As a result, two layered garnet samples together yield a Tera–Wasserburg lower intercept age of 203.2 ± 8.7 Ma, whereas two vein-type vesuvianite samples yield ages of 144.4 ± 3.7 Ma and 145.9 ± 3.1 Ma, identical within error to the ages of 141.5 ± 7.2–145.5 ± 2.9 Ma obtained from micro-disseminated and veinlet-like scheelite. The above dating results and the geological observations that ore-barren layered garnet cut by later quartz–scheelite–(garnet)–(vesuvianite) hydrothermal veins suggest two stages of skarnization in the Nanyangtian deposit (ca. 203 Ma and ca. 141–146 Ma, respectively), whereas the W mineralization occurred during ca. 141–146 Ma. It is inferred that the age of ∼203 Ma is related to Indosinian regional metamorphism and associated migmatization-hydrothermal activity. Nevertheless, the ages of 141–146 Ma, obviously older than those of the adjacent Laojunshan granitic pluton (∼83–97 Ma) and its associated Dulong Sn–Zn polymetallic deposit (∼82–96 Ma), are possibly attributable to another unrevealed magmatic-hydrothermal system at depth, as a result of Paleo-Pacific subduction during the Early Cretaceous period. A two-period superimposed mineralization model is thus proposed at Nanyangtian. Based on all reported age data, four major magmatic-metallogenic episodes ranging from ca. 445–410 Ma, 215–203 Ma, 152–140 Ma to 100–75 Ma have been determined in the Laojunshan district. [ABSTRACT FROM AUTHOR]

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Abstract\nKEY POINTSThe Watershed scheelite deposit is located in an extinct fore-arc basin in the Mossman Orogen of North Queensland. This fore-arc region comprises multiply deformed, Ordovician–Silurian metasedimentary rocks of the Hodgkinson Formation, and it was intruded by Carboniferous–Permian granites of the Kennedy Igneous Association. At Watershed, the Hodgkinson Formation includes strongly deformed skarn-altered conglomerate, psammite and slate units, which record four deformation events that evolved from ductile (D1–3) to brittle–ductile (D4). Early, D1–2 scheelite mineralisation in Carboniferous monzonite and skarn-altered conglomerate formed during regional prograde metamorphism, which reached upper greenschist to lower amphibolite facies conditions. Permian, D4 scheelite mineralisation was deposited in transtensional, shear-related veins, vein haloes and skarn-altered conglomerate during retrograde, lower greenschist facies metamorphism. During D4, four stages of retrograde alteration (retrograde stages 1–4) affected the rocks. Fluid inclusion assemblages in retrograde stage 2, vein scheelite and quartz are characterised by a low-salinity H2O–NaCl ± CH4 fluid (XCH4 <0.01, 1.4–8.0 wt% NaCleq). The fluid inclusions show evidence for fluid mixing between a low (∼0 wt% NaCleq) and a medium (<8 wt% NaCleq) saline fluid. Scheelite mineralisation P–T conditions were determined at ∼300 °C and 1–1.8 kbar (i.e. a depth of 3.7–6.7 km), indicative of a high geothermal gradient (35–75 °C/km), which was likely caused by the heat from the Permian granites. The presence of pyrrhotite and arsenopyrite in D4 veins (retrograde stage 4), plus graphite and methane in the fluid inclusions in scheelite, indicates reduced mineralisation conditions. Oxygen isotope compositions (δ18OVSMOW) of retrograde stage 2 scheelite (+3.8 to +7.3‰), plagioclase (+7.0 to +11.8‰) and quartz (+12.6 to +15.5‰) indicate a fluid temperature of 306 ± 56 °C with δ18OVSMOW values between +4.7 and +8.3‰. Retrograde stage 3 muscovite δDVSMOW (−73.4 to −62.7‰) and δ18OVSMOW (+11.5 to +13.2‰) values were used to calculate the O–H isotopic compositions of the fluids in equilibrium with the minerals at various possible temperatures (250–300 °C). The results are consistent with a metamorphic origin for the mineralising fluid. Sulfur isotope compositions (δ34SCDT between −2.5 and +2.8‰) for vein-hosted, retrograde stage 4 sulfides indicate that sulfur could have come from seawater or seawater sulfate, which is consistent with the local geology, even though this range overlaps with magmatic sulfur isotope compositions. Metamorphic fluids probably originated from devolatilisation reactions in the Hodgkinson Formation during prograde metamorphism. Permian intrusions acted as heat source enhancing metamorphic fluid flow and metal transport.The main economic D4 scheelite mineralisation in veins occur at temperatures of 306 ± 56 °C and depths between 3.7 and 6.7 km.D4 scheelite mineralisation precipitated predominantly from a low- to medium-salinity metamorphic fluid, and with both H2O–NaCl and H2O–NaCl–CH4 compositions.The presence of methane (CH4) plus graphite in some fluid inclusions and the sulfide mineral phases indicates reduced mineralisation conditions.D4 scheelite mineralisation precipitated predominantly from a low- to medium-salinity metamorphic fluid, and with both H2O–NaCl and H2O–NaCl–CH4 compositions.The presence of methane (CH4) plus graphite in some fluid inclusions and the sulfide mineral phases indicates reduced mineralisation conditions. [ABSTRACT FROM AUTHOR]

A peculiar type of stratabound tungsten mineralization in metacarbonate rocks was discovered and explored at Mallnock (Austria) during the late 1980s. It is the only tungsten occurrence in the Eastern Alps in which scheelite is associated with wolframite (96 mol% ferberite). The tungsten prospect is located in the Austroalpine Drauzug-Gurktal Nappe System recording polyphase low-grade regional metamorphism. Raman spectroscopy of carbonaceous material yield maximum metamorphic temperatures of 296 ± 27 °C and 258 ± 27 °C, which are assigned to Variscan and Eoalpine metamorphism, respectively. Scheelite and ferberite occur as polyphase stockwork-like mineralization in Fe-rich magnesite in the northern ore zone (Mallnock North), whereas in the western ore zone (Mallnock West), scheelite-quartz veinlets are exclusively hosted in dolomitic marbles. LA-ICP-MS analyses of scheelite and ferberite yield low contents of Mo, Nb, Ta, and rare earth elements, but high contents of Na and Sr. Uranium is particularly high in scheelite (up to 200 µg/g) and makes this mineral a suitable target for U–Pb dating. In situ U–Pb dating of scheelite yielded an early Permian age (294 ± 8 Ma) for Mallnock West and a Middle Triassic age (239 ± 3 Ma) for Mallnock North. A monzodioritic dike close to Mallnock yielded a U–Pb apatite date of 282 ± 9 Ma and supports the polyphase formation of this mineralization. The U–Pb scheelite ages indicate that a model for tungsten metallogeny in the Eastern Alps must also consider remobilization of tungsten by metamorphic fluids. In the Alps, the Permian to Triassic period (ca. 290–225 Ma) is characterized by an overall extensional geodynamic setting related to the breakup of Pangea. Lithospheric thinning caused higher heat flow, low-P metamorphism, and anatexis in the lower crust, which led to enhanced crustal fluid flow in the upper crust. These processes were not only responsible for the formation of metasomatic hydrothermal magnesite and siderite deposits in the Eastern Alps but also for this unique magnesite-ferberite-scheelite mineralization at Mallnock. [ABSTRACT FROM AUTHOR]

The Tepsi ultrabasic body is located in the northeastern Fennoscandian Shield close to the junction of the Serpentinite Belt–Tulppio Belt (SB–TB) with suites of the Lapland–Belomorian Belt (LBB) of Paleoproterozoic age. The body is a deformed laccolith that has tectonic contacts with Archean rocks. Its primary textures and magmatic parageneses are widely preserved. Fine-grained olivine varies continuously from Fo90.5 to Fo65.4. The whole-rock variations in MgO, Fe2O3, SiO2, and other geochemical data are also indicative of a significant extent of differentiation. Compositional variations were examined in the grains of calcic and Mg-Fe amphiboles, clinochlore, micas, plagioclase, members of the chromite–magnetite series, ilmenite, apatite, pentlandite, and a number of other minor mineral species. Low-sulfide disseminated Ni-Cu-Co mineralization occurred sporadically, with the presence of species enriched in As or Bi, submicrometric grains rich in Pt and Ir, or diffuse zones in pentlandite enriched in (Pd + Bi). We recognize two series: the pentlandite series (up to 2.5–3 wt.% Co) and the cobaltpentlandite series (~1 to ~8 apfu Co). The latter accompanied serpentinization. The two series display differences in their substitutions: Ni ↔ Fe and Co → (Ni + Fe), respectively. Relative enrichments in H2O, Cl, and F, observed in grains of apatite (plus high contents of Cl in hibbingite or parahibbingite), point to the abundance of volatiles accumulated during differentiation. We provide the first documentation of scheelite grains in ultrabasic rocks, found in evolved olivine-rich rocks (Fo77–72). We also describe unusual occurrences of hypermagnesian clinopyroxene associated with tremolite and serpentine. Abundant clusters of crystallites of diopside display a microspinifex texture. They likely predated serpentinization and formed owning to rapid crystallization in a differentiated portion of a supercooled oxidized melt or, less likely, fluid, after bulk crystallization of the olivine. We infer that the laccolithic Tepsi body crystallized rapidly, in a shallow setting, and could thus not form megacycles in a layered series or produce a well-organized structure. Our findings point to the existence of elevated PGE-Au-Ag potential in numerous ultrabasic–basic complexes of the SB–TB–LBB megastructure. [ABSTRACT FROM AUTHOR]

Co-substitution of Ce3+ at the A-site and Nb5+ at the B-site by smaller Ca2+ and W6+ in (Ce 1- x Ca x)(Nb 1- x W x)O 4 ceramics drives the structure from monoclinic fergusonite (x = 0.1 - 0.3) to tetragonal scheelite (x = 0.4). Adjusting the A-O and B-O bond characteristics could drastically tune the microwave dielectric properties. The ε r decreased from 20.7 to 16.2, and the negative deviations between ε r and ε r (C-M) resulted from the rattling effect of Nb5+/W6+ cations in the octahedron along the b -axis direction. The τ f varied from negative (−11 ppm/°C at x = 0.1) to positive (+87.8 ppm/°C at x = 0.4), mainly attributed to the rattling effect of Nb5+/W6+. Q×f increased from 21,006 to 45,025 GHz (x = 0.3) and then decreased to 36,563 GHZ (x = 0.4), accompanied by increasing packing fraction and decreasing Raman FWHM. The ceramic at x = 0.15 exhibited the optimum microwave dielectric properties of ε r = 19.7, Q×f = 35,450 GHz, and τ f = 0.8 ppm/°C. [ABSTRACT FROM AUTHOR]

The East Kunlun Orogen is a giant magmatic tectonic activity belt and an important part of the Central Orogenic Belt of China. It has superior mineralization conditions and remarkable mineralization phenomena, and has always attracted the attention of some geologists. The Lalangmai Tungsten Mine is located in the Chahanwusu River area in the eastern section of the East Kunlun Orogen and is under the jurisdiction of Huishui township, Dulan county, Qinghai province. It is a newly discovered skarn-type deposit in recent years. This article takes the Lalangmai tungsten deposit as the research target. Purpose: The purpose of the research is to establish a geological-geochemical exploration model to guide the deployment of prospecting for the tungsten deposit in the Lalangmai area. Method: The research method was selected based on the comprehensive analysis of the mineralization geological background, the geological characteristics of the mining areas, and the characteristics of the surface soil geochemical anomalies, and further summarized the geological-geochemical prospecting mark, thereby constructing a geological-geochemical exploration model. Result: The main conclusions obtained from the research include; W-Sn-Mo-Au-Ag-As-Sb elements have a strong correlation, while other elements have a poor correlation. The currently discovered tungsten ore bodies(mineralized bodies) mainly occur in skarn rocks. The contact zone between tonalite diorite and Baishahe formation strata is the most favorable location for finding tungsten ore. The northeast-southwest trending structural fracture zone is an ore-containing structure. The metal minerals in the tungsten ore bodies are mainly scheelite, followed by wolframite. Conclusion: Based on the geological-geochemical exploration model constructed in the article, 3 prospecting target areas were delineated in the Lalangmai area, including 1 Class- I prospecting target area and 2 Class- II prospecting target areas. In addition, it is expected that the deep areas and the peripheral areas of the mining area have great prospecting potential. More geological exploration work arrangements should be implemented. The innovation of this article is the systematically constructed geological-geochemical exploration model, which has achieved good prospecting results in the Lalangmai tungsten mining area and achieved a breakthrough in prospecting for tungsten deposits in the eastern section of East Kunlun Orogen, and has provided a new prospecting and exploration path for searching for the same type of tungsten deposits in the area. [ABSTRACT FROM AUTHOR]

Doping engineering is a feasible strategy to construct highly efficient photocatalysts. Herein, Ce and Fe mono- and co-doped CaWO 4 catalysts were synthesized by precipitation method followed by annealing and the degradation activities were tested for the removal of tetracycline antibiotic under visible light irradiation. The experimental results indicated that the photocatalytic activity was greatly improved by co-doping of Ce and Fe elements, in which Fe ions significantly narrowed the band gap energy while Ce dopant increased the oxygen vacancies of CaWO 4 catalyst. The effects of several experimental conditions (solution pH, initial concentration, co-existing anions, heavy metals, and organic matter) were examined, and the degradation mechanism was explored by radical trapping tests. Furthermore, the photocatalytic efficiency of Ce/Fe–CaWO 4 catalyst was investigated under natural sunlight irradiation and the degradation performance slightly decreased from 98.4% (simulated sunlight) to 86.8% (natural sunlight) following five repeatability tests, indicating the exceptional stability in outdoor environment. This research demonstrated the synergy of Ce/Fe co-doping and provided novel insights to develop visible-light driven efficient catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

The Xingluokeng deposit is the largest granite-related tungsten deposit within the Wuyi metallogenic belt in South China. The Xingluokeng intrusion primarily consists of porphyritic biotite granite, biotite granite, and fine-grained granite. The deposit is represented by veinlet-disseminated mineralization with K-feldspathization and biotitization, alongside quartz-vein mineralization with greisenization and sericitization. This study investigates in-situ analyses of quartz compositions from both the intrusion and hydrothermal veinlets and veins. Trace element correlations indicate that trivalent Al3+ and Fe3+ replace Si4+ within the quartz lattice, with monovalent cations (such as Li+, Na+, and K+) primarily serving as charge compensators. Low Ge/Al ratios (< 0.013) of quartz from granites suggest a magmatic origin. The low Al/Ti and Ge/Ti ratios, accompanied by high Ti contents in quartz, suggest that the porphyritic biotite granite and biotite granite are characterized by relatively low levels of differentiation and high crystallization temperatures. In contrast, the fine-grained granite exhibits a higher degree of fractionation, lower crystallization temperatures, and a closer association with tungsten mineralization. Ti contents in quartz from quartz veins indicate Qz-I formed at temperatures above 400 °C, while Qz-II to Qz-V formed at temperatures below 350 °C. Variations in different generations of quartz, as indicated by Al content and (Al + Fe)/(Li + Na + K) ratio, suggest that Qz-I precipitated from a less acidic fluid with a stable pH, whereas Qz-II to Qz-V originated from a more acidic fluid with notable pH variations. Consequently, alkaline alteration and acidic alteration supplied the essential Ca and Fe for the precipitation of scheelite and wolframite, respectively, highlighting a critical mechanism in tungsten mineralization at the Xingluokeng deposit. [ABSTRACT FROM AUTHOR]

Mineralogy and formation conditions were studied in a newly found vein wolframite mineralization, cutting migmatitized paragneisses in the exocontact of a small Carboniferous granite body in the Pohled quarry, Moldanubian Zone of the Bohemian Massif, Czech Republic. The early stage of the rich mineral assemblage (36 mineral species) involves wolframite, columbite-group minerals, molybdenite, and scheelite hosted by quartz–muscovite–chlorite gangue, which was followed by base-metal sulfides in a quartz gangue, whereas the last stage included calcite gangue with fluorite and minor sulfides. The mineral assemblage points to the mobility of usually hardly soluble elements, including W, Sn, Zr, Nb, Th, Ti, Sc, Y, and REEs. A fluid inclusion study indicates a significant decrease in homogenization temperatures from 350–370 °C to less than 100 °C during vein formation. Fluids were aqueous, with a low salinity (0–12 wt. % NaCl eq.) and traces of CO2, N2, CH4, H2, and C2H6. The δ18O values of the fluids giving rise to quartz and scheelite are positive (min. 4‰–6‰ V-SMOW). The Eh and pH of the fluid also changed during evolution of the vein. Both wolframite and columbite-group minerals are anomalously enriched in Mg. We suggest that the origin of this distinct mineralization was related to the mixing of Mo,W-bearing granite-derived magmatic fluids with external basinal waters derived from contemporaneous freshwater (but episodically evaporated) piedmont basins. The basinal waters infiltrated into the subsurface along fractures formed in the extensional tectonic regime, and their circulation continued even after the ending of the activity of magmatic fluids. The studied wolframite mineralization represents the most complete record of the 'hydrothermal' history of a site adjacent to a cooling granite body in the study area. Moreover, there are broad similarities in the mineral assemblages, textures, and chemical compositions of individual minerals from other occurrences of wolframite mineralization around the Central Moldanubian Plutonic Complex, pointing to the genetic similarities of the Variscan wolframite-bearing veins in this area. [ABSTRACT FROM AUTHOR]

The Glenorchy area of northwest Otago consists of a low-relief Holocene fluvial delta complex below glaciated mountains of Otago Schist basement, and has locally elevated arsenic (As) from two geogenic pathways: Mesozoic hydrothermal processes and Holocene shallow groundwater transport. Soils on the delta complex are primitive and contain abundant sand and silt derived from unoxidised schist basement, with background As contents generally <30 mg/kg. Some soils in wetland areas on the delta have naturally elevated (geogenic) arsenic contents that are locally >300 mg/kg on the cm2 scale. Arsenic enrichment has occurred in the upper 30 cm where dissolved As and Fe from low-redox chemical conditions in shallow groundwater has become oxidised, thereby lowering their solubility. Both As and Fe are being mobilised from background sulfide minerals in schist-derived debris, and groundwater As concentrations up to 0.8 mg/L have been recorded. Historic mining of scheelite for tungsten on the surrounding mountains has exposed small volumes (typically tens to hundreds of m3) of arsenopyrite-bearing mine wastes with spot As contents from <500 to >10 000 mg/kg. Water discharging from mine adits have pH∼8 and dissolved As up to 0.3 mg/L, but these waters are rapidly diluted downstream to <0.02 mg/L. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry ...) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

Multistage tungsten mineralization was recently discovered in the Mamupu copper‐polymetallic deposit in the southern Yulong porphyry copper belt (YPCB), Tibet. This study reports the results of cathodoluminescence, trace element and Sr isotope analyses of Mamupu scheelite samples, undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore‐forming fluids. Three different types of scheelite are identified in the Mamupu deposit: scheelite A (Sch A) mainly occurs in breccias during the prograde stage, scheelite B (Sch B) forms in the chlorite‐epidote alteration zone in the retrograde stage, while scheelite C (Sch C) occurs in distal quartz sulfide veins. The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage. Compared with ore‐related porphyries, Sch A has a similar REE pattern, but with higher ΣREE, more depleted HREE and slightly lower (87Sr/86Sr)i ratios. These features suggest that Sch A is genetically related to ore‐related porphyries, but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition. Sch B shows dark (Sch B‐I) and light (Sch B‐II) domains under CL imaging. From Sch B‐I to Sch B‐II, LREEs are gradually depleted, with MREEs being gradually enriched. Sch C has the highest LREE/HREE ratio, which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE‐rich minerals, such as diopside and garnet, in the early prograde stage. The Mo content in Sch B and Sch C gradually decreased, indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later, the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity. The extensive interaction of magmatic‐hydrothermal fluids and carbonate provides the necessary Ca2+ for the precipitation of scheelite in the Mamupu deposit. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry ...) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

Sodium-cerium molybdate, NaCe(MoO4)2, belongs to the family of double alkaline rare-earth molybdate, and it holds significant importance across various technological domains, such as environmental remediation and energy conversion. Despite its importance, the behavior of NaCe(MoO4)2 under high-pressure conditions remains unexplored. This study uses synchrotron x-ray diffraction and Raman spectroscopy to investigate NaCe(MoO4)2in situ under high-pressure conditions. We observed a pressure-induced phase transition from the scheelite to the M ′ -fergusonite structure type on a double molybdate at approximately 10 GPa. These findings contribute to a deeper understanding of the structural stability of NaCe(MoO4)2 and shed light on the broader field of high-pressure studies of double molybdates. [ABSTRACT FROM AUTHOR]

Sodium-cerium molybdate, NaCe(MoO4)2, belongs to the family of double alkaline rare-earth molybdate, and it holds significant importance across various technological domains, such as environmental remediation and energy conversion. Despite its importance, the behavior of NaCe(MoO4)2 under high-pressure conditions remains unexplored. This study uses synchrotron x-ray diffraction and Raman spectroscopy to investigate NaCe(MoO4)2in situ under high-pressure conditions. We observed a pressure-induced phase transition from the scheelite to the M ′ -fergusonite structure type on a double molybdate at approximately 10 GPa. These findings contribute to a deeper understanding of the structural stability of NaCe(MoO4)2 and shed light on the broader field of high-pressure studies of double molybdates. [ABSTRACT FROM AUTHOR]

The molybdenum oxidation rate of a large-scale tungsten molybdenum mine reaches 42. 45%. The intimate association of molybdenum, tungsten, iron, and fluorite minerals, with fine particle size, and high content of calcium-magnesium silicates, carbonates, and clay minerals, distributed extremely uneven, poses challenges in ore-dressing. To address this complexity in processing polymetallic ores, an industrializable and relatively simple crushing and grinding magnetic separation desliming flotation process was adopted. This process yielded molybdenum sulfide concentrate (containing 45.76% molybdenum), molybdenum oxide - tungsten oxide concentrate (containing 15.88% molybdenum and 22.65% tungsten), and iron concentrate (containing 63.11% iron). The recovery rates of molybdenum, tungsten, and iron were 67.75%,51.84%, and 36.44% respectively, achieving effective resource recovery. Pre-desliming before flotation facilitates smooth flotation operations, reduces reagent consumption, and stabilizes the recovery of valuable minerals. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry 4) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078-18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ U-Pb dating of scheelite yields the ages of 30 Ma. • The bulk H-O and in situ Sr isotopies indicate that ore-forming fluid mainly originated from magmatic-hydrothermal fluids. • The in-situ trace element composition of scheelite shows similarity with vein-type W (Au). Scheelite is one of the main ore minerals in tungsten deposits, and its geochemical features can be used to examine and constrain tungsten mineralization. The Yangla deposit is one of the most important Cu-polymetallic skarn-porphyry deposits in the "Sanjiang" polymetallic metallogenic domain, Southwest China, hosting 150 Mt of Cu ores with economic concentrations of Pb, Zn, and Sb. The newly discovered tungsten mineralization in the Yangla deposit remains poorly understood. Hence, in order to ascertain the timing of tungsten mineralization, investigate its genetic relationship with magmatism and ore genesis, and elucidate the source, nature, and evolution of the ore-forming fluids, we performed a combined study of geochronology, in-situ trace elements, fluid inclusions, H-O isotopes, and in-situ Sr isotopic compositions of scheelite. In-situ U-Pb dating of scheelite showed that the timing of tungsten mineralization was 30 Ma. This mineralization age is significantly later than the published Cu mineralization age (∼230 Ma), skarn (∼231 Ma), and granitoid emplacement age (∼230 Ma) in the Yangla ore district. In-situ trace element analyses revealed that scheelite is depleted in Mo, Mn, and Ta and slight enriched in Sr, Y, REEs, and Au. It is also characterized by HREE-depleted chondrite-normalized patterns with strongly positive Eu anomalies. Our data reveal that 3Ca2+ = (2REE)3++□Ca (site vacancy) is the main substitution mechanism that controls REEs in scheelite. The low concentrations of Mo, negative Ce anomalies, and positive Eu anomalies of scheelite indicate a reduced condition. Preliminary REEs features indicate that the genesis of scheelite may be related to vein-type W (Au) deposits. The homogenization temperatures for fluid inclusions present a strongly decreasing trend (328 to 173 ℃), indicate that cooling is the predominant mechanism for the formation of scheelite. The δD and δ18O fluid values from fluid inclusions of scheelite vary broadly from −161.70 ‰ to −133.30 ‰ and from 6.32 ‰ to 9.80 ‰, respectively, indicating a mixture of magmatic and meteoric water, with possible involvement of magma degassing and fluid–rock interaction. The initial 87Sr/86Sr ratios of scheelites (0.71931– 0.72117) are significantly higher than those of the granodiorite (0.71149 – 0.71990) and basalt (0.70562 – 0.70995) in the Yangla ore district, indicating that the Oligocene magmatism and Devonian marble with radiogenic Sr isotopic compositions contributed to tungsten mineralization. The fluid-rock interaction between the ore-forming fluids derived from the concealed granitoids and the Devonian wall rocks may play an important role in tungsten mineralization and provide significant Ca for scheelite precipitation. Thus, the tungsten mineralization should be associated with Oligocene magmatism, ruling out the genetic relationship with Late Triassic magmatism and being significantly different from the skarn-porphyry Cu-Pb-Zn mineralization at Yangla. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry 4) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078-18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

The contradiction between the optical absorption depth and carrier diffusion length has emerged as a significant problem constraining the performance of BiVO4 photoanodes. Fabricating a one-dimensional (1D) structure is considered a promising strategy to address the above problem. However, the synthesis of BiVO4 photoanodes consisting of 1D monoclinic scheelite remains a great challenge. In this study, a 1D molybdenum (Mo) doped BiVO4 photoanode (Mo:1D-BVO) consisting of monoclinic scheelite BiVO4 submicron rods (SMRs) through a phase transition from a 1D tetragonal zircon BiVO4 precursor was successfully prepared. It was found that Mo doping could lower the phase transition barrier from tetragonal zircon to monoclinic scheelite BiVO4. Due to the Mo:1D-BVO photoanode's remarkable light absorption efficiency, efficient carrier separation, and superior conductivity, it yields a photocurrent density of 2.08 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE), which is 3.5 times higher than that of pristine BiVO4. Upon the introduction of the co-catalyst, the photocurrent density of Co–Pi/Mo:1D-BVO attains 3.18 mA cm−2 at 1.23 V vs. RHE, accompanied by a carrier separation efficiency of 91%. Our study introduces a novel approach for the production of remarkably efficient 1D monoclinic scheelite BiVO4 photoanodes. [ABSTRACT FROM AUTHOR]

Metal ores are mineralogically characterised to understand their genesis in order to allow informed decisions on mineral processing and to recognise likely environmental risks upon mining. However, standard mineralogical techniques generate only two-dimensional information at best, which in addition may be subject to sampling and stereological errors. By contrast, computed tomography (CT) is a non-destructive imaging technique that allows three-dimensional analysis of solid materials. In the present study, two ore types of the Kara Fe-W deposit (Australia) were characterised using CT to examine their mineral texture and modal mineralogy as well as scheelite distribution and ore grade (WO3). The results show that scheelite is primarily associated with hydrous phases (e.g., epidote, chlorite, amphibole) and occurs as massive or disseminated mineral as well as vein-fill at minor and trace concentrations. This study demonstrates that CT of scheelite ore enables accurate 3D texture visualisation (volume, grain size distribution) and yields valid quantitative data on modal mineralogy and WO3 grade of individual ore samples. Consequently, CT analysis of scheelite-bearing ore provides information relevant for ore genesis studies and comminution strategies for the possible recovery of scheelite as a by-product from metalliferous ores. [ABSTRACT FROM AUTHOR]

Scheelite (CaWO4) is an economically important W mineral in skarns that form when magmatic fluids exsolved from a granitic intrusion react with carbonate wall rocks. In the Fujiashan W skarn deposit, scheelite formed during four stages of the hydrothermal skarn development. We present cathodoluminescence (CL) images and in situ trace element and Sr-O isotope data of scheelite from these four stages, i.e., scheelite in prograde and retrograde skarn, quartz-sulfide veins, and late calcite replacements. Scheelite from prograde skarn and quartz sulfide veins are homogeneous and show oscillatory zoning textures in CL images, whereas scheelite from retrograde skarn and late carbonate stages display dissolution-reprecipitation and patchy textures. The brightness of CL textures decreases with a higher substitution of Mo. Molybdenum-rich scheelite (up to 2.1 wt%) is characterized by relatively high contents of Nb and Ta (up to 156 and 0.9 ppm, respectively), positive Eu anomalies, high-δ18O values (5.2 to 5.9‰), and relatively low-87Sr/86Sr values (0.70661 to 0.70727), and has grown in a system with a continuous supply of magmatic fluid. Molybdenum-poor scheelite (0.2 wt%) has low contents of Nb and Ta, negative Eu anomalies, low-δ18O values (4.2 to 4.3‰), and relatively high-87Sr/86Sr ratios (0.70748 to 0.70804). This type of scheelite formed in a system with a restricted flow of magmatic fluid during scheelite precipitation became increasingly depleted in elements that substitute into scheelite. The continued reaction of the magmatic fluid with the wall rocks and the precipitation of minerals from the fluid resulted in a systematic change of the δ18O and 87Sr/86Sr ratios. Chemical and isotopic variations in scheelite may reflect the pulsed flow of a magmatic fluid and do not require the involvement of different fluids or contrasting redox conditions. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry \overline{4}) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters.

Objective The Tongshanling deposit in the western Nanling metallogenic belt of Hunan Province is a skarn Cu polymetallic deposit related to Ⅰ-type granodiorite. Recently, a thick stratiform W-Mo skarn ore body has been found in the limestone of the Qiziqiao Formation far from the granodiorite intrusion. Its geological characteristics, mineral assemblages and genetic types are different from those of the ore bodies in the contact zone of the intrusion. Methods In this study, timing and genesis of the Tongshanling stratiform are analysed, through field investigation, microscopic identification, in situ U-Pb dating of garnet, and LA-ICP-MS trace element analysis of scheelite. Results The following four stages of mineralization are identified: garnet skarn, epidote and chlorite skarn, quartz sulfide and quartz calcite. The U-Pb concordant age of garnet is (160.4±4.2) Ma (MSWD=0.79), is significantly later than that of the granodiorite (~167 Ma) and similar to that of the granite porphyry (~161 Ma). The total rare earth element (ΣREE) distribution pattern of the garnet core is light rare earth element (LREE) enrichment and heavy rare earth element (HREE) flat and is similar to the whole-rock ΣREE model of granite porphyry. The ΣREE distribution pattern of garnet rims is LREE-depleted and is different from that of garnet in contact zone skarns. Scheelite associated with epidote can be divided into three stages. ΣREE modes of the three stages are all LREE enrichment and HREE depletion, but the ΣREE content decreases significantly from the first stage (Sch1-a, 332×10-6-353×10-6) to the second stage (Sch1-b, 144×10-6-301×10-6) and the third stage (Sch1-c, 4.05×10-6-31.8×10-6). Scheelite associated with chlorite (Sch2) shows LREE enrichment and HREE depletion, and their ΣREE content is 51.2×10-6-139×10-6. W-Mo mineralization is mainly concentrated in the retrograde stage. The Sch1-b and Sch2 stages have higher oxygen fugacities are the main stage of W mineralization, while the other stages (Sch1-a and Sch1-c) with lower oxygen fugacities are the main stage of Mo mineralization. Comprehensive analysis reveals that the stratiform skarn and contact zone skarn in the Tongshanling and Weijia deposits are different metallogenic systems. The stratiform skarn may be related to the granite porphyry with a relatively high degree of fractionation. Conclusion More attention should be given to the late granite porphyry in deep within and at the edge of the Tongshanling deposit.

This document is an editorial for a special issue of the journal Minerals, focusing on rare metal ore formations and metallogeny. The editorial highlights the importance of rare metals, such as lithium, rubidium, and rare-earth elements, which are considered critical mineral resources by major economies. The special issue includes 14 research articles that discuss the genesis, geological setting, and characteristics of various rare-metal deposits. The articles cover topics such as the role of volatile components in the migration and enrichment of rare metals, the substitution mechanism of rare-metal elements in pegmatites, and the mineralization processes of different rare-metal deposits. The editorial hopes that this special issue will contribute to further research and exploration of rare-metal deposits. [Extracted from the article]

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This paper proposes luteolin (LUT) as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate (NaOL) system. The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing. At pH = 9, with LUT concentration of 50 mg·L−1 and NaOL concentration of 50 mg·L−1, scheelite recovery reaches 80.3%. Calcite, on the other hand, exhibits a recovery rate of 17.6%, indicating a significant difference in floatability between the two minerals. Subsequently, the surface modifications of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing, Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The study investigates the selective depressant mechanism of LUT on calcite. Adsorption capacity testing and Zeta potential analysis demonstrate substantial absorption of LUT on the surface of calcite, impeding the further adsorption of sodium oleate, while its impact on scheelite is minimal. FT-IR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite, forming strong chemisorption bonds between the hydroxyl group and calcium ions present. AFM directly illustrates the distinct adsorption densities of LUT on the two mineral types. Consequently, LUT can effectively serve as a depressant for calcite, enabling the successful separation of scheelite and calcite. [ABSTRACT FROM AUTHOR]

The Zhazixi deposit hosted in sedimentary rocks is a major Sb-W deposit in South China. The mineral scheelite, which can be dated by the U-Pb method, commonly occurs in both tungsten (W)-dominated and antimony (Sb)-dominated ore veins of the deposit. Cathodoluminescence (CL) images reveal the presence of three distinct stages of scheelite (Sch-I, Sch-II and Sch-III) within the deposit. These three scheelites were dated using in-situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), yielding U-Pb ages of 158.1±5.4 Ma and 157.6 ± 4.9 Ma for Sch-I, 155 ± 11 Ma for Sch-II, and 151.3±6.1 Ma for Sch-III. These data suggest that the Zhazixi Sb-W deposit formed during the Late Jurassic (160–150 Ma) rather than the Late Triassic as previously suggested. Considering the temporal similarity with low-temperature hydrothermal Sb deposits in the Xiangzhong metallogenic province (XZMP), the formation of the Sb-W deposit may have followed a similar genetic model, where meteoric groundwater circulated to depth and extracted metals from fertile basement rocks through fluid-rock interaction, resulting in the generation of ore fluids. This study highlights that Late Jurassic low-temperature hydrothermal Sb-polymetallic mineralization in the XZMP is likely more extensive than previously perceived. [ABSTRACT FROM AUTHOR]

Novel Raman crystals can significantly help to expand the available laser wavelength bands and effectively promote the development of laser technology. Bismuth molybdate and tungstate mixed crystals, Bi2Mo2.6W0.4O12 (BMO), with a scheelite crystal structure, are found to have superior Raman gain characteristics. Large-sized single crystals of BMO with dimensions up to 83 mm × 65 mm × 55 mm were sucessfully grown in the Bi2O3–MoO3 hybrid-flux solutions by the top-seeded solution growth (TSSG) method. Spontaneous polarized Raman spectra of BMO crystals were systematically measured and analyzed based on microvibrations of the composing Raman active ionic groups. Through comparison, it was found that BMO crystals had a large Raman gain coefficient, 1.1 times that of the mostly used YVO4 crystals. Besides, under the pump of a 1064 nm laser, a first-order Raman laser at 1176 nm, and dual-wavelength of both first-order and second-order at 1315 nm, were achieved under the Y(ZZ)Y and Y(XX)Y configurations, respectively. A maximum output power of 1.12 mW, corresponding to an optical-to-optical conversion efficiency of 15.6%, was successfully achieved. This work provides systematic analysis of the polarized Raman spectra of BMO crystals and reveals their great application prospects as novel Raman laser crystals. [ABSTRACT FROM AUTHOR]

The Nuri deposit is the only Cu‐W‐Mo polymetallic deposit with large‐scale WO3 resources in the eastern section of the Gangdese metallogenic belt, Tibet, China. However, the genetic type of this deposit has been controversial since its discovery. Based on a study of the geological characteristics of the deposit, this study presents mineralization stages, focusing on the oxide stage and the quartz‐sulfide stage where scheelite is mainly formed, referred to as Sch‐A and Sch‐B, respectively. Through LA‐ICP‐MS trace element and Sr isotope analyses, the origin, evolutionary process of the ore‐forming fluid and genesis of the ore deposit are investigated. Scanning Electron Microscope‐Cathodoluminescence (SEM‐CL) observations reveal that Sch‐A consists of three generations, with dark gray homogenous Sch‐A1 being replaced by relatively lighter and homogeneous Sch‐A2 and Sch‐A3, with Sch‐A2 displaying a gray CL image color with vague and uneven growth bands and Sch‐A3 has a light gray CL image color with hardly any growth band. In contrast, Sch‐B exhibits a 'core‐rim' structure, with the core part (Sch‐B1) being dark gray and displaying a uniform growth band, while the rim part (Sch‐B2) is light gray and homogeneous. The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore‐forming fluid in the Nuri deposit originated from granodiorite porphyry and, later on, some country rock material was mixed in, due to strong water‐rock interaction. Combining the O‐H isotope data further indicates that the ore‐forming fluid in the Nuri deposit originated from magmatic‐hydrothermal sources, with contributions from metamorphic water caused by water‐rock interaction during the mineralization process, as well as later meteoric water. The intense water‐rock interaction likely played a crucial role in the precipitation of scheelite, leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz‐sulfide stage, while also causing a gradual decrease in oxygen fugacity (fO2) and a slow rise in pH value. Additionally, the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic‐hydrothermal scheelite. Therefore, considering the geological features of the deposit, the geochemical characteristics of scheelite and the O‐H isotope data published previously, it can be concluded that the genesis of the Nuri deposit belongs to porphyry‐skarn deposit. [ABSTRACT FROM AUTHOR]

New toxic-metal-free sustainable yellow pigments have been developed in scheelite-type solid solutions: [(Li0.33Ca0.33La0.33)xBi1-x][MoxV1-x]O4. The developed pigments show a structural transition from monoclinic to tetragonal scheelite-type structures upon the substitution of LiCaLaMoO4 into the BiVO4 system. The absorption edge is gently blue-shifted from the parent BiVO4 by widening the bandgap upon the incorporation of various metal ions such as Li, La, Ca, and Mo into the lattice, allowing different intense yellow hues to be produced. The typical pigment [(LiLaCa)0.198Bi0.8][Mo0.2V0.8]O4 showed the most vivid yellow hue with a b* value of 78.32, which is comparable to the commercial Sicopal yellow (b* = 76.9). Further, the developed toxic-metal-free pigments have high near-infrared reflectance, making them sustainable as eco-friendly cool colorants for paint and plastic formulations. [ABSTRACT FROM AUTHOR]

Scheelite, one kind of common REE-rich and U-bearing hydrothermal mineral, is extensively developed in various types of gold deposits, which can be used to record nature and timing of metallogenesis. The Zhaishang Carlin-like gold deposit in the Qinling Orogen is a giant Au deposit, hosting 127t of Au @ 2.67 g/t with economic concentrations of tungsten and antimony. The study reports two types of scheelite based on the characteristics of petrography and geochemistry. Sch A shows significant oscillatory zoning with dark gray cathodoluminescence (CL) response, whereas Sch B displays patchy textures with brighter CL response. Systematic LA-ICP-MS U–Pb dating of Sch A and Sch B yields ages of 227.1 ± 3.2 Ma and 226.2 ± 6.9 Ma, respectively. The new dates, constraining the Zhaishang Au–W mineralization to ~ 227Ma, coincide well with the western Qinling magmatism, metallogenic and tectonic events. There are significant variations in concentration, the Sch A has low REE content (mean = 41.3 ppm), negative Eu-anomaly with slightly positive Ce-anomaly, whereas Sch B, with small negative or positive Eu-anomaly, has higher REE content (mean = 247 ppm) and higher positive Ce-anomaly. The positive correlation of EuN and EuN* records oxidizing condition during the whole W mineralization event. Additionally, Sch B intergrown with selenides with an increase in the Ce-anomaly supports that the latter has higher oxygen fugacity environment. The Sr isotope signature for scheelite supports that ore-forming metals mostly inherited the host rock component, while the proportion of magma-derived Sr increased in the Sch B. Fluid–rock interactions co-precipitated Au and W caused by the release of Fe and Ca cations and the increase of pH. The study highlights that scheelite as a recorder can help in deciphering the nature and timing of metallogenesis of the studied Au–Sb–W deposit, and thus other similar Au–W deposits. [ABSTRACT FROM AUTHOR]

In this work, a reliable and robust in situ non-matrix-matched calibration method is proposed for element composition determination in scheelite samples. With external calibration against the silicate glass standard reference material NIST SRM 610, the concentrations of both major elements (Ca and W) and trace elements (Si, Fe, Mo, Y, rare earth elements, etc.) in scheelite are determined using an ArF 193 nm excimer nanosecond laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). Here, the ablation was performed by hole drilling under a helium (He) environment using a laser spot size of 35 μm and a laser repetition of 5 Hz, and the aerosols were then transported to a quadrupole ICP-MS by a mixture of He and make-up gas argon (Ar) with a total gas flow rate of 1.6 L/min. Results showed that there was no apparent matrix effect between the NIST SRM 610 and scheelite by this proposed method. With internal standardization against W, the obtained concentrations of CaO and WO3 were found to yield an average matrix CaO/WO3 mass fraction ratio of 0.245 (2σ = 0.003, n = 19), which agreed well with the value of 0.243 (2σ = 0.002, n = 15) from electron probe microanalysis (EPMA). Furthermore, the accuracy of trace element analyses with this proposed non-matrix-matched calibration in situ method was evaluated by comparing the concentration results with those from bulk analysis by solution nebulizer ICP-MS (SN-ICP-MS). It was found that the quantification results from LA-ICP-MS and SN-ICP-MS were comparable, in particular showing a relative concentration bias of the total ∑REE+Y contents of less than 2%. This confirmed that scheelites can be accurately analyzed in situ by LA-ICP-MS without matrix-matched calibration standards. By using this developed in situ method, the element compositions in a series of scheelite samples from different W-associated deposits in China were successfully quantified, promising further genetic process investigation and associated geologic activities of the polymetallic resources. [ABSTRACT FROM AUTHOR]

Featuring subtle lithological alterations in the host rocks and containing colossal gemstone crystals, the scheelite deposit at Xuebaoding in the Pingwu region of Sichuan Province exhibits characteristics typical of a vein-like hydrothermal-type deposit. The scheelite from the Xuebaoding region is renowned for its high saturation of color, perfect crystal shape, and pure color. In this study, its crystal structure and mineralogical, geochemical, and in situ Sr-Nd isotope characteristics are all systematically characterized. Our objective is to determine the source of ore-forming materials, the timing of the mineralization, and the chemical composition of scheelite, including major elements, trace elements, and rare earths elements (REE). The scheelite samples were analyzed with a variety of methods such as polarizing microscopy, X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), electron probing, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In addition, conventional gemological tests were performed using instruments including gemstone microscopes, GI-UVB ultraviolet fluorescent lamps, grating spectroscopy, etc. The results demonstrate that scheelite exhibits a high refractive index, excellent crystallinity, and a granular structure. Clear color bands and ring structures are observed within the minerals, accompanied by interference colors of light blue, blue, and yellow. Additionally, the mineral components are relatively concentrated, with muscovite and illite serving as accessory minerals. Furthermore, the chemical composition of scheelite reveals a WO3/CaO mass ratio that approaches or exceeds the ideal value. Moreover, it exhibits a wide range of variations in total rare earth element (∑REE) content, which is characterized by an enrichment of light rare earths (LREE), significant negative Eu anomalies, and insignificant Ce anomalies. In addition, the metallogenic formation of scheelite can be estimated to have occurred during the Toarcian stage in the Lower Jurassic Epoch period, approximately 183 Ma. The study further revealed that A-type granite serves as the genesis type of scheelite, with most of the ore-forming materials originating from the upper crust and a few derived from younger crustal sources. [ABSTRACT FROM AUTHOR]

An overview of the composition of wolframite ores of the Akchatau deposit and the technologies for processing concentrates using NaOH and Na2CO3 by hydro- and pyrometallurgical methods is given, and the disadvantages associated with both the technology and the equipment are noted. To develop a technology for processing Akchatau wolframite concentrates, samples of ore materials were taken, the chemical and mineralogical composition of the samples was studied, and enrichment was carried out to obtain rich concentrates. The kinetics of the sintering of the wolframite concentrate with soda was investigated, the dependences of the degree of transformation of the tungsten minerals into sodium tungstate were obtained, and the rate constants, the order of the reaction, and the values of the apparent activation energy were calculated. The results of sintering an enlarged sample of wolframite concentrate with soda in a muffle furnace are presented. After the subsequent leaching, studies were carried out to purify the obtained solutions of sodium tungstate from the impurities while eliminating the operations of the neutralizing solutions through the use of electrodialysis with an MK-40 cation-exchange membrane. The scheme of processing the wolframite ores of Akchatau is proposed. [ABSTRACT FROM AUTHOR]

The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement. The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12°C. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures. [ABSTRACT FROM AUTHOR]