Wolframite Samples Research Articles

U–Pb LA-ICP-MS and Re–Os dating of wolframite and molybdenite: Constraints on multiple mineralization and cooling history (40Ar/39Ar) for the magmatic–hydrothermal system at Borralha, northern Portugal

The Borralha area (Iberian Massif, Portugal) reflects a long-lived and multiphase magmatism (ca. 316 to 300 Ma), characterized by three types of granite emplacement during two different extensional events (E1 and E2) and one compressional event (C3) within the Variscan orogeny. The W (Cu) mineralization styles correspond to veinlets and quartz veins (i.e., São António and Santa Helena), and disseminations in the Santa Helena breccia pipe. Molybdenite coexists with an Fe-bearing wolframite–quartz assemblage in the Venise breccia pipe and quartz veins (i.e., São José and São Paulo).The geochemistry and geochronology of wolframite and molybdenite samples were studied by electron probe microanalysis (EPMA), in-situ U–Pb laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and Re–Os thermal ionization mass spectrometry (TIMS). The wolframite yields a U–Pb age (sample WBV1) of 315.2 ± 4.7 Ma (2σ), representing the first recognized episode of W deposition in the Iberian Massif. Wolframite samples (WBV1, WB1, and WB4) have a ferberite composition with a hübnerite/ferberite ratio of < 29. High amounts of Nb (up to 3703 ppm) with low Ta (up to 123 ppm) and REEs (up to 11.4 ppm) and conversely, low amounts of Nb (up to 471 ppm) with high Ta (up to 190 ppm) and REEs (up to 53.7 ppm) were measured in wolframite samples. The REEs normalized patterns of the wolframite samples record a mixed signature. Large and positive Eu/Eu* and Er/Er* anomalies were identified (sample WBV1), whereas negative Ce/Ce* and Nd/Nd* anomalies were observed in samples WB1 and WB4.Molybdenite Re–Os dating yields absolute ages ranging from 305.1 to 303.8 ± 2.2 Ma (2σ), which are coeval with the emplacement of E2 biotite granite (Penedos; I-type; <305 Ma). Low amounts of Re (<1 ppm), W, Co, Ni, As, Cu, Bi, Fe, Mn V and Se (<0.005 wt%) were detected in the molybdenite structure.Constraints between the timing of W- and Mo-deposition and a protracted cooling history of the host rocks are confirmed by 40Ar/39Ar white mica dating. The 40Ar/39Ar ages obtained for secondary white micas collected from Mo veins (Venise breccia pipe; 277 ± 3 and 287 ± 4 Ma 2σ) and W (Cu) dissemination (Santa Helena breccia pipe; 287 ± 2 and 279.0 ± 6 Ma 2σ) record the isotopic resetting by later hydrothermal overprints and cooling /exhumation history after E2 Gerês biotitic granite emplacement.The W-ore deposition did occurred during the final E1 extensional tectonic stage (315 Ma) and E2 extensional tectonic stage for Mo-ore deposition, where a temporal offset was needed for the adjustment of tectonic conditions after the C3 compressional and E2 extensional stage started.

Contribution discrepancy of two distinct wall rocks to wolframite mineralization from Dongshanwan quartz-vein tungsten deposit, Southern Great Xing’an Range, China

The Southern Great Xing’an Range is a significant polymetallic metallogenic belt in Northeast China. The ages of granite related to tungsten mineralization have been well quantified, however, the timing and mechanism of quartz vein-type wolframite deposition remain unclear. Therefore, our study focused on the Dongshanwan tungsten deposit, representing a typical wolframite-bearing quartz vein-type deposit in the Southern Great Xing’an Range. Quartz vein-type tungsten mineralization was mainly contained in the Early Cretaceous granite porphyry, with few exceptions in the Permian tuff. Representative wolframite samples were collected from intragranitic (Wol-I) and intra-tuff (Wol-II) quartz veins for wolframite U–Pb dating, electron probe microanalysis (EPMA), and trace elemental analysis. Wolframite U–Pb dating recognized an Early Cretaceous mineralization event at 139–141 Ma, consistent with the previous Dongshanwan granite’s ages (∼142 Ma) but much younger than tuff (∼260 Ma). All the wolframite samples belonged to the ferberite series (FeO/MnO = 4.0–6.9), which indicates a link to the highly fractionated granite. Wol-I showed high contents of Nb, Ta, Sc, and HREEs and a strongly negative Eu anomaly (0.02–0.29), while these elements in Wol-II were approximately one order of magnitude lower than in Wol-I and the Eu anomaly was highly variable (0.17–1.02). The redox characteristics reflected by the Eu anomaly of wolframite may correspond to the variations in oxygen fugacity. Based on petrology, geochemistry, and element mass migration, this study suggests that the granite porphyry and tuff in the Dongshanwan deposit contributed differently to the wolframite precipitation even if the ore-forming fluids were of a common magmatic-hydrothermal origin. The exsolved fluid reserved in the closed system interacts with granite to achieve continuous enrichment in Nb, Ta, Sn, and REEs and accepts external Fe supply from granite alteration to precipitate Wol-I. In contrast, the fluids in relatively open and non-granitic systems have lower Nb, Ta, Sn, and REEs than the former, and Fe supply depends on the alteration of tuff. The abundance of fluorite and the non-CHARAC (CHArge-and-RAdius-Controlled) behavior of Y/Ho and Zr/Hf in the wolframite suggested that fluorine plays an important role in the migration and enrichment of tungsten and other elements during tungsten mineralization.

Skarn mineralogy and in-situ LA–ICP–MS U–Pb geochronology of wolframite for the Caojiaba tungsten deposit, southern China: Implications for a reduced tungsten skarn deposit

The Caojiaba tungsten deposit (19.03 Mt@ 0.37 wt% WO3) is hosted in skarn within clastic and carbonate rocks in the Xiangzhong metallogenic province (XZMP), southern China. The deposit is characterized by an early prograde skarn overprinted by a retrograde assemblage, and then by quartz–scheelite–sulfide veins. The Caojiaba skarn is characterized by grossular garnet (Grs65–85Adr7.1–31) and hedenbergitic pyroxene (Hd63–86Di11–33), similar to the well–studied reduced tungsten skarns worldwide. In this paper, we present in-situ laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) analysis of U–Pb isotopes and trace elements of wolframite grains coexisting with scheelite in the quartz–scheelite–sulfide veins. Uranium is correlated positively with Nb5+, tetravalent (Ti4+, Sn4+, Zr4+, Hf4+), and trivalent (Sc3+, V3+, Y3+, REE3+) cations in all wolframite samples, suggesting that the incorporation of U into wolframite is controlled by the coupled substitution mechanisms. Two wolframite samples (CJB–43 and CJB–44) yielded 206Pb/238U ages of 212.4 ± 1.0 Ma (2σ, n = 50, MSWD = 0.92) and 211.8 ± 1.1 Ma (2σ, n = 43, MSWD = 1.4), overlapping with the late Triassic granitic rocks (225.6–204.5 Ma) in the XZMP. Mineralogical and geochronological evidence collectively indicate that Caojiaba is a typical example of the late Triassic reduced tungsten skarn deposits in the XZMP. This study demonstrates the potential of U–Pb dating of wolframite and highlights its importance for directly dating hydrothermal ore–forming processes.

Two significant quartz-wolframite-veining mineralization events in the Jiangnan Orogen, South China: Constraints from in-situ U–Pb dating of wolframite in the Dongping and Dahutang W-(Cu-Mo) deposits

The Jiangnan Orogen of South China is a world-class tungsten (W) metallogenic belt. Although the ore-forming ages of porphyry-skarn scheelite deposits in the Jiangnan Orogen are well quantified, the timing of quartz-vein type wolframite deposition is still ambiguous. Two typical quartz-vein type wolframite deposits, the Dongping and Dahutang deposits, were chosen for analysis. For the Dongping W deposit, a lower intercept 206Pb/238U age of 129.5 ± 5.4 Ma (1σ, MSWD = 0.75) was obtained for wolframite, which agrees well with the zircon weighted average mean 206Pb/238U age of 129.8 ± 0.3 Ma (2σ, MSWD = 0.4) from samples of the three granite units (biotite granite, muscovite granite and two-mica granite of the hidden pluton). This indicates that the quartz-wolframite-vein mineralization in the Dongping deposit has a genetic relationship with the hidden Dongping pluton. The wolframite samples from the Dahutang W deposit yielded a lower intercept 206Pb/238U age of 137.3 ± 4.8 Ma (1σ, MSWD = 1.9), which corresponds to previously reported scheelite Sm–Nd, molybdenite Re–Os and muscovite 40Ar–39Ar ages from the Dahutang deposit (142–138 Ma), as well as to monazite and zircon U–Pb ages for the ore-related biotite granite, biotite granite porphyry and granite porphyry (143–138 Ma). In combination with previous studies, these results constrain two significant quartz-wolframite veining events at ∼130 Ma and ∼140 Ma in the Jiangnan W metallogenic belt.

Timing and tectonic setting of tin mineralization in southern Myanmar: constraints from cassiterite and wolframite U–Pb ages

The southern Myanmar tin ore district is an important part of the well-known Southeast Asia tin belt (SATB), and hosts numerous economically important primary tin-tungsten ore deposits. However, the timing of formation of these deposits is unclear due to the scarcity of robust age data. The tectonic setting of tin mineralization in this area also needs to be further constrained. Most of the primary tin-tungsten ore deposits in southern Myanmar are typical hydrothermal quartz vein–type, with cassiterite and wolframite as the main ore minerals. Here, we present in situ U–Pb ages of cassiterite and wolframite from nine granite-related hydrothermal Sn–W deposits in southern Myanmar. Cassiterite samples from the Hermyingyi, Thitkhatoe, Thaling Taung, Kalonta, Taungphila, Pagaye, Bawapin, Kanbauk, and Letha Taung deposits yield common lead-corrected weighted mean 206Pb/238U ages of 61.6 ± 0.8 Ma, 61.9 ± 0.6 Ma, 60.4 ± 0.9 Ma, 63.0 ± 0.6 Ma, 62.9 ± 0.6 Ma, 69.5 ± 0.5 Ma, 63.6 ± 0.6 Ma, 61.3 ± 0.6 Ma, and 84.9 ± 0.5 Ma, respectively. Wolframite samples collected from these deposits also yield consistent ages with the cassiterite samples. These ages, combined with available tin mineralization ages from other deposits in the western part of the SATB, define three epochs of Sn metallogeny related to three contrasting geodynamic settings: (1) Early Cretaceous (~ 125–110 Ma) mineralization is related to post-collision slab break-off after collision between the West Burma terrane and the Sibumasu-Tengchong terrane; (2) Late Cretaceous to Paleocene (~ 90–60 Ma) mineralization developed in an Andean-type accretionary setting during subduction of the Neo-Tethys oceanic lithosphere; (3) Early Eocene (~ 50–40 Ma) mineralization may have formed in a post-collision setting after the India-Asia collision.

Direct dating of hydrothermal tungsten mineralization using in situ wolframite U–Pb chronology by laser ablation ICP-MS

The wolframite series may contain relatively high U and low common Pb contents, and thus has been used for direct U-Pb dating of hydrothermal W mineralization. In this paper, we present in-situ laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analysis of U–Pb isotopes and trace elements of wolframite crystals from the giant Yaogangxian and Piaotang W deposits in the extensive Nanling metallogenic belt, South China. The objective of this work is to directly constrain the timing of hydrothermal W mineralization in these two deposits. Wolframite crystals from both deposits show textural evidence for two generations. Early wolframite (Wol-1) has higher Fe and lower Mn contents relative to those in the late wolframite (Wol-2). Uranium is correlated positively with Nb5+, tetravalent (Ti, Sn, Zr, Hf), and trivalent (Sc, V, Y, REEs) cations in all wolframite samples, suggesting that the incorporation of U into wolframite is controlled by the coupled substitution mechanisms. The early and late wolframite domains from the Yaogangxian deposit yielded U–Pb ages of 159.1 ± 2.0 Ma (2σ; MSWD = 0.7) and 153.7 ± 0.7 Ma (2σ; MSWD = 0.5), respectively. Similarly, two wolframite generations from the Piaotang deposits yielded U–Pb ages of 159.5 ± 1.3 Ma (2σ; MSWD = 0.3) and 152.1 ± 0.9 Ma (2σ; MSWD = 0.5). The obtained U–Pb ages confirm two successive episodes of hydrothermal W mineralization at ~159 Ma and ~153 Ma in the Yaogangxian and Piaotang deposits. This study demonstrates the potential of U–Pb dating of wolframite by LA-ICPMS and highlights its importance for directly dating hydrothermal ore-forming processes.

Geochemical wolframite fingerprinting \u2013 the likelihood ratio approach for laser ablation ICP-MS data

Wolframite has been specified as a ‘conflict mineral’ by a U.S. Government Act, which obliges companies that use these minerals to report their origin. Minerals originating from conflict regions in the Democratic Republic of the Congo shall be excluded from the market as their illegal mining, trading, and taxation are supposed to fuel ongoing violent conflicts. The German Federal Institute for Geosciences and Natural Resources (BGR) developed a geochemical fingerprinting method for wolframite based on laser ablation inductively coupled plasma-mass spectrometry. Concentrations of 46 elements in about 5300 wolframite grains from 64 mines were determined. The issue of verifying the declared origins of the wolframite samples may be framed as a forensic problem by considering two contrasting hypotheses: the examined sample and a sample collected from the declared mine originate from the same mine (H1), and the two samples come from different mines (H2). The solution is found using the likelihood ratio (LR) theory. On account of the multidimensionality, the lack of normal distribution of data within each sample, and the huge within-sample dispersion in relation to the dispersion between samples, the classic LR models had to be modified. Robust principal component analysis and linear discriminant analysis were used to characterize samples. The similarity of two samples was expressed by Kolmogorov-Smirnov distances, which were interpreted in view of H1 and H2 hypotheses within the LR framework. The performance of the models, controlled by the levels of incorrect responses and the empirical cross entropy, demonstrated that the proposed LR models are successful in verifying the authenticity of the wolframite samples.Graphical abstractGeochemical wolframite fingerprinting

Zircon U–Pb and Wolframite Sm–Nd Dating of the Bayinsukhtu Tungsten Deposit in Southern Mongolia and its Geological Significance

AbstractThe Bayinsukhtu tungsten deposit is a newly discovered quartz‐vein tungsten deposit in the Xing'an–Mongolia Orogenic Belt (XMOB) in southern Mongolia, hosted by the Bayinsukhtu granite porphyry. The granite porphyry is located mainly south of the study area, over 3 km2. The rock consists of quartz and feldspar phenocrysts in a fine‐grained matrix, also mainly composed of feldspar and quartz. The granite porphyry samples demonstrate high SiO2 and high alkalinity. All samples also straddle the high‐potassium calc‐alkaline series. In a plot of the molar ratios of A/NK versus A/CNK, the granites are metaluminous. The chondrite‐normalized REE patterns are characterized by large negative Eu anomalies and fractionated LREEs. The U–Pb age of zircons from the granite porphyry is 298.8 ± 1.8 Ma, and the Sm–Nd age of the five wolframite samples from the tungsten deposit is 303 ± 19 Ma. The cooling age of the granite porphyry and tungsten mineralization is within the error of measurement and is of the Late Carboniferous age. Geological and geochronological evidence shows that the tungsten mineralization and the granite porphyry at Bayinsukhtu are genetically closely related and that they are results of Carboniferous magmatism. Their tectonic setting is related to the accretion of the Central Asian Orogenic Belt during the late Paleozoic era.

Tracing metal sources in peribatholitic hydrothermal W deposits based on the chemical composition of wolframite: The example of the Variscan French Massif Central

We present a complete dataset for major, minor and trace elements in wolframite ([Fe,Mn]WO4) based on the example of several peribatholitic hydrothermal W deposits located in the Variscan French Massif Central (FMC). The wolframite samples were characterized down to the micrometer scale by combining scanning electron microscopy observations and in situ chemical analysis by electron probe microanalyzer and laser ablation – inductively coupled plasma – mass spectrometry. Most samples are Fe-dominated wolframites and are characterized by variable Fe/(Fe+Mn) values for the studied deposits (from 0.36 to 0.86) without significant alteration features. Wolframites present intracrystalline variations for concentrations of several minor and trace elements, principally for Nb, Ta, and Sn, which reflect growth zoning. The minor and trace element compositions of the different wolframite samples show at first order similar enrichments in Ta, Nb, Sn, Zn, and In, as well as depletions in LREE, Li, Th, Ti, Zr, Hf, Pb, V, Co, and Mg, compared to the upper continental crust. Second order compositional variations are observed between the studied deposits, which can be separated in four main regional geochemical groups. This work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary hydrothermal fluid. The regional variations observed in the geochemical signatures of wolframite reflect local variations in the composition of the hydrothermal fluid, i.e. variable metal sources. Therefore, this suggests that the minor and trace element contents in wolframite likely represent direct markers of the source of the hydrothermal fluid and ultimately of the metals. The comparison between the trace element compositions of wolframite with the compositions of regional granitic rocks and worldwide shales suggests that evolved peraluminous granites represent the main source of metals in peribatholitic hydrothermal W deposits from the FMC, whereas metasedimentary rocks have a limited to no influence on the metal budget.

40 Ma of hydrothermal W mineralization during the Variscan orogenic evolution of the French Massif Central revealed by U-Pb dating of wolframite

We present U-Pb thermal ionization mass spectrometer (TIMS) ages of wolframite from several granite-related hydrothermal W±Sn deposits in the French Massif Central (FMC) located in the internal zone of the Variscan belt. The studied wolframite samples are characterized by variable U and Pb contents (typically <10 ppm) and show significant variations in their radiogenic Pb isotopic compositions. The obtained U-Pb ages define three distinct geochronological groups related to three contrasting geodynamic settings: (i) Visean to Namurian mineralization (333–327 Ma) coeval with syn-orogenic compression and emplacement of large peraluminous leucogranites (ca. 335–325 Ma), (ii) Namurian to Westphalian mineralization (317–315 Ma) synchronous with the onset of late-orogenic extension and emplacement of syn-tectonic granites (ca. 315–310 Ma) and (iii) Stephanian to Permian mineralization (298–274 Ma) formed during post-orogenic extension contemporaneous with the Permian volcanism in the entire Variscan belt. The youngest ages (276–274 Ma) likely reflect the reopening of the U-Pb isotopic system after wolframite crystallization and may correspond to late hydrothermal alteration (e.g. ferberitization). Our results demonstrate that W(±Sn) mineralization in the FMC formed during at least three distinct hydrothermal events in different tectono-metamorphic settings over a time range of 40 Ma.

Estimation of applicability of scattered radiation for XRF

The applicability of coherently and incoherently scattered radiation was investigated on the example of quantifying the Nb content in wolframite. The calculated and experimental intensities of Nb K a -line for binary and multicomponent mixtures of Nb 2 O 5 with various matrices have been compared. The major oxides MgO, SiO 2 , CaO, Fe 2 O 3 , and a typical component of tungsten ore (Fe, Mn)WO 3 were used as the main matrices. Measurements were carried out using the energy dispersive X-ray spectrometer with Si(Li)-detector and radioactive isotope source 109 Cd. The analysis of data shows that when using the ratio of the intensities of coherently and incoherently scattered X-radiation of the excitation source the dependence of the analytical line intensity of niobium on the content of W in the samples is taken into account. The experimental results confirm the conclusions of the theoretical consideration. This technique was successfully used to study wolframite samples from the deposits of the Eastern andWestern Mongolia. A procedure for the determination of Cu, Mo and Fe concentrations in ores, copper and molybdenum concentrates, and enrichment waste was developed to control the process of enrichment at the mining company Erdenet,Mongolia. This procedure was based on using regression equations. The form of regression equations was chosen based on the theoretically calculated intensities. The comparison results of measurements using the newly developed technique and the standard-background method are presented. Keywords : X-ray spectral fluorescence analysis of ores and enrichment products, method of standard-background, theoretical simulation of matrix effects DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.001 P.Zuzaan 1 , D.Bolortuya 1 , S.Davaa 1 , A.G.Revenko 2 1 Nuclear Research Center, National University of Mongolia , Sukhbaatar District, Ulaanbaatar, Mongolia 2 Institute of the Earth’s Crust, SB RAS , Irkutsk, Russian Federation

He–Ar Isotope Composition of Pyrite and Wolframite in the Tieshanlong Tungsten Deposit, Jiangxi, China: Implications for Fluid Evolution

AbstractThe Tieshanlong tungsten‐polymetallic deposit is a large wolframite deposit of quartz vein type located in southern Jiangxi, South China. It is genetically related to a high‐K S‐type granite. Seven pyrite and two wolframite samples, selected for He and Ar isotope analyses, yielded 3He/4He values of 0.04–0.98 Ra, 40Ar/36Ar ratios of 293.5–368.0, and 38Ar/36Ar ratios of 0.176–0.193. These data indicate that the ore‐forming fluids associated with the deposit did not result from a simple mixing of the crustal‐ and mantle‐derived end‐member fluids, but that primeval meteoric fluids were also involved in the generation of the associated granitic magma by partial melting of crustal metasedimentary rocks. Further investigations show that only minimal He from the mantle was added during generation of the associated granitic magma. It is postulated that boiling and second mixing with “new” meteoric fluids took place during migration of magmatic‐hydrothermal fluids into wall‐rock fractures, resulting in a drastic decrease of their metal transport capacity, which triggered the tungsten‐polymetallic mineralization.

Physicochemical characterization of the chlorination of natural wolframites with chlorine and sulphur dioxide

The chlorination of natural wolframites (Mn x Fe 1− x WO 4) with chlorine and sulphur dioxide was studied in a vertical reactor with a static bed and upward flow of reactive gases. Wolframite samples collected from five different deposits of Argentina were carefully purified by hand under a binocular microscope. Upgraded specimens with this methodology had a variable ratio of divalent metals (0.06 < x < 0.84) for similar tungsten content (WO 3 = 72.4–73.3%). Experimental conditions more appropriate to make chlorinations were established using the iron-rich wolframite. Under these conditions, the tungsten extraction was determined as a function of the ratio of iron(II) and manganese(II) present in each sample. Physicochemical characterization of the system involved measurement of wolframite cell dimensions, identification of reaction products formed from metallic elements (tungsten, iron and manganese) and reactivity evaluation of both divalent metals by means of thermodynamic parameters. Results obtained show that iron-rich wolframites had higher reactivity with respect to other solid solution specimens. Reaction products identified were all volatile, except manganese(II) chloride found in liquid state. Thermodynamic analysis confirmed that formation of iron oxychloride (FeOCl) as an intermediate chlorination product would be feasible, although it was not possible to observe any evidence of this reaction under experimental conditions used. Finally, it is indicated that the highest reactivity of iron-rich wolframites was attributed to the volatile nature of all their reaction products, to iron(II) oxidation easiness if compared with manganese(II) and to possible formation of iron oxychloride.

In-situ precise isotopic analysis of tungsten using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) with time resolved data acquisition

Measurements of 182W/183W, 184W/183W and 186W/183W ratios in solid geological samples have been carried out using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). A time resolved analysis (TRA) data acquisition technique was used to minimise integration losses in transient signals and also to minimise the risk of lowering the precision and accuracy of the measurements due to integration of low signal intensity data. The resulting precisions of the 182W/183W, 184W/183W and 186W/183W measurements were about 0.015%, 0.031% and 0.039% (2σ) when an optimised integration area and an expansion stabiliser were used. These values are only 3-times worse than those achieved by conventional solution nebulisation measurements. However, the total amount of W used for isotopic analysis using the laser ablation technique was only 20 ng, which is much less (0.1–0.01) than the typical amount required for the solution nebulisation method. Measured W isotopic ratios in a pure W filament and wolframite samples showed excellent agreement with those from chemical reagents: 182W/183W = 1.85147 ± 0.00022, 184W/183W = 2.14169 ± 0.00022 and 186W/183W = 1.98764 ± 0.00021 (2σ) normalised to 186W/184W ≡ 0.92805, obtained by conventional nebulisation. The internal precision using LA-MC-ICP-MS was sufficient to detect the natural variations in the 182W/183W isotopic ratio originating from radiogenic contributions of 182Hf (typically 0.04– 0.2%).

Oxygen isotope studies of wolframite in tungsten ore deposits of south China

Based on the oxygen isotopic compositions of 133 wolframite samples and 110 quartz samples collected from 30 tungsten ore deposits in south China, in conjunction withδD values and other data, these deposits can be divided into four types. (1) Reequilibrated magmatic water-hydrothermal tungsten ore deposits. Theδ18O values of wolframite and quartz samples from this type of tungsten ore deposits are about +5–+12‰, respectively. The calculatedδ18O\(O_{H_2 O} \) values of ore fluids in equilibrium with quartz are about +6.5‰, and theδ\(D_{H_2 O} \) values of fluid inclusions in quartz range from −40 to −70‰ (2) Meteoric water-hydrothermal tungsten ore deposits. Theδ18O values of wolframite in this type of tungsten deposits are around −1‰ (3) Stratiform tungsten ore deposits. In these deposits, theδ18O values of quartz and wolframite are about +17 and +3‰, respectively. It is considered that these stratiform tungsten ore deposits are genetically related to submarine hot-spring activities. (4) Complex mixed-hydrothermal tungsten ore deposits. These tungsten ore deposits are characterized by multi-staged mineralization. Theδ18O values of early wolframite are around +5‰, but of later wolframite are lower than +4‰, indicating that the early wolframite was precipitated from reequilibrated magmatic water-hydrothermal solutions and the late one from the mixture of hydrothermal solutions with meteoric waters or mainly from meteoric waters.

Étude mineralogique, chimique et diffractometrique de quelques wolframites du Brésil

Ten wolframite samples from nine Brazilian mines and occurrences and one from Portugal were mineralogically and chemically studied and X-Rayed in order to determine their characteristics and the relations between them . A short description of the mineral deposits and the samples is given. Measured gravities, reflectivities and microhardnesses show continuous variations, generally however without correlation. On the contrary, chemical analysis (determination of MnO/FeO ratio or Hubnerite/Ferberite) and diffractometric measurements (angle 2o(512)) demonstrate a good linear graphical correlation within the limits of experimental precision. As a result, this graph enables one, with a fast diffractometric determination, to locate an unknow wolframite in the Hubnerite-Ferberite series. With regard to the classification of the wolframite occurrences they all appear to belong to the pneumatolytic type with transitions to hydrothermal veins of low temperature and to the pegmatitic type with the increase of temperature.