Wolframite Deposition Research Articles

The H/F ratio as an indicator of contrasted wolframite deposition mechanisms

Understanding wolframite deposition mechanisms is a key to develop reliable exploration guides for W. In quartz veins from the Variscan belt of Europe and elsewhere, wolframites have a wide range of compositions, from hübnerite- (MnWO4) to ferberite-rich (FeWO4). Deposition style, source of Mn and Fe, distance from the heat/fluid source and temperature have been proposed to govern the wolframite H/F (hübnerite/ferberite ratio) defined as 100 at. Mn/(Fe + Mn). The Argemela mineralized district, located near the world-class Panasqueira W mine in Portugal, exposes a quartz-wolframite vein system in close spatial and genetic association with a rare-metal granite. Wolframite is absent as a magmatic phase, but W-rich whole-rock chemical data suggest that the granite magma is the source of W. Wolframite occurs as large homogeneous hübnerites (H/F = 64–75%) coexisting with montebrasite, K-feldspar and cassiterite in the latest generation of intragranitic veins corresponding to magmatic fluids exsolved from the granite. Locally, early hübnerites evolve to late more Fe-rich compositions (H/F = 45–55%). In a country rock vein, an early generation of Fe-rich hübnerites (H/F = 50–63%) is followed by late ferberites (H/F = 6–23%). Most Argemela wolframites have H/F ratios higher than at Panasqueira and other Variscan quartz-vein deposits which dominantly host ferberites. In greisens or pegmatitic veins, wolframites generally have intermediate H/F ratios. In those deposits, fluid-rock interactions, either involving country rocks (quartz-veins) or granite (greisens) control W deposition. In contrast, at Argemela, wolframite from intragranitic veins was deposited from a magmatic fluid. Differentiation of highly evolved peraluminous crustal magmas led to high Mn/Fe in the fluid which promoted the deposition of hübnerite. Therefore, the H/F ratio can be used to distinguish between contrasted deposition environments in perigranitic W ore-forming systems. Hübnerite is a simple mineralogical indicator for a strong magmatic control on W deposition.

A Miocene tungsten mineralization and its implications in the western Bangong-Nujiang metallogenic belt: Constraints from U-Pb, Ar-Ar, and Re-Os geochronology of the Jiaoxi tungsten deposit, Tibet, China

The Jiaoxi quartz-vein type wolframite deposit is the first tungsten mineralization discovered in the western part of the Bangong-Nujiang metallogenic belt, which is well-known for the porphyry-epithermal-skarn Cu-Au mineralization. The Jiaoxi deposit is associated with a porphyritic monzogranite that intrudes sandstone and shale in the Shiquanhe ophiolite mélange. The ages of the magmatism and mineralization in the deposit are here constrained by the dates obtained from the porphyritic monzogranite, hydrothermal muscovite and molybdenite. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating of two porphyritic monzogranite samples yields weighted mean 206Pb/238U coincident age of 14 ± 1 Ma. Two samples of hydrothermal muscovite from wolframite-bearing quartz veins yield plateau 40Ar/39Ar ages of 13.4 ± 0.1 and 13.3 ± 0.1 Ma, respectively. Re-Os model ages of five molybdenite samples range from 11.4 ± 0.2 to 11.8 ± 0.2 Ma, with a weighted mean model age of 11.6 ± 0.2 Ma. These dates indicate that the tungsten mineralization at Jiaoxi was formed during the Middle Miocene. This Miocene tungsten mineralization is significantly different from the Early and Late Cretaceous Cu-Au mineralization in the western part of the Bangong-Nujiang metallogenic belt. Our dating results show that there is a Middle Miocene tungsten mineralization in the western part of the Bangong-Nujiang metallogenic belt. The tectonic setting for the tungsten mineralization is here interpreted to be the regional extension associated with the India-Asia continental collision. The discovery of the Jiaoxi deposit has important significance on regional tungsten prospecting.

The role of hydrothermal alteration in tungsten mineralization at the Dahutang tungsten deposit, South China

The giant Dahutang tungsten deposit has total reserves of more than 1.31 Mt of WO3 with a scheelite/wolframite ratio of ∼1 and is mainly hosted by the Neoproterozoic Jiuling granodiorite batholith (∼820 Ma). The deposit is characterized by four types of alteration, including biotite alteration, phyllic alteration, greisenization and silicification. Whole-rock geochemical analyses showed that the elements Ti, Ni, V, Sc, and Lu exhibited immobility during the four alteration processes. The mobile element geochemistry effectively differentiated among four distinct hydrothermal alteration styles. During the biotite mineralization, there were mass gains in Al2O3, Fe2O3, MnO, MgO, K2O, P2O5, and W and depletions in SiO2, CaO, and Na2O. The phyllic alteration exhibited mass gains in SiO2, Fe2O3, MgO, and W and depletions in CaO, Na2O, and K2O, but Al2O3, MnO, and P2O5 were immobile. The weak greisenization exhibited mass gains in SiO2, Fe2O3, K2O, P2O5 and W and depletions in Na2O, MgO, and CaO, whereas Al2O3 and MnO remained immobile. The silicification exhibited mass gains in SiO2 and W and depletions in Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O, but MnO exhibited immobility. These alterations were related to at least three major hydrothermal fluid systems. Firstly, a hydrothermal fluid caused biotitization zones and Fe + Mn ± W mineralization (mostly biotite) at temperatures ranging from 560 to 450 °C, and the magmatic hydrothermal fluids were derived from the Jurassic porphyritic biotite granite (∼150 Ma) and characterized by alkaline, oxidized, moderate-pressure, and low-salinity features. Secondly, a hydrothermal fluid was formed by the mixing of magmatic fluid with meteoric water and was responsible for the phyllic/weak greisenization alteration zones at temperatures ranging from 440 to 450 °C and characterized by alkaline, weakly oxidized, moderate-pressure, and low-salinity features. Thirdly, a hydrothermal fluid caused greisenization and silicification zones at temperatures ranging from 440 to 160 °C, which were characterized by acidic, reduced, high-pressure, and moderate- to low-salinity features, derived from the Cretaceous fine-grained biotite granite (∼144 Ma), and associated with the main W mineralization at Dahutang.The characteristics of Fe-enriched biotite in the biotitized and greisenized rock – decreasing temperature, high pressure, and high log(fH2O/fHCl) – could facilitate the formation of scheelite deposits, but the high F suppressed it. The decreasing temperature and f(O2) and the Fe-Mn released from biotite contributed to the formation and precipitation of wolframite. During alkaline alteration, biotite and apatite acted as storage places for Fe-Mn and Ca, which were subsequently released by acidic alteration to form scheelite and wolframite. There was no enough Ca was released from biotitized rock for the acidic alteration to provide the WO42− to form scheelite. Meanwhile, Fe was added, and Mn was released to form the scheelite + wolframite deposit. Based on all the results, we have developed a genetic model for tungsten mineralization including superimposed alteration processes (alkaline overprinted by acidic alteration), which led to the gain and loss of elements, and corresponding to two magmatic events, the Jurassic porphyritic biotite granite and the Cretaceous fine-grained biotite granite. The superposition of alterations played an important role in the mineralization of the Dahutang giant tungsten deposit.

Hydraulic Fracturing Leads to Wolframite Deposition at Magmatic‐hydrothermal transition

Hydraulic Fracturing Leads to Wolframite Deposition at Magmatic‐hydrothermal transition

Roles of carbonate/CO2 in the formation of quartz-vein wolframite deposits: Insight from the crystallization experiments of huebnerite in alkali-carbonate aqueous solutions in a hydrothermal diamond-anvil cell

Quartz-vein-type wolframite deposits are a primary type of tungsten deposits. Traditionally, F and Cl were considered as important agents in tungsten transportation during ore formation process. However, ore-forming fluids enriched in CO2 were commonly observed in natural fluid inclusions associated with quartz-vein-type wolframite deposits, indicating that carbonate or CO2 could be important for their formation. In this paper, we report experiments of the dissolution and crystallization of huebnerite in the MnWO4-Li2CO3 (or Na2CO3)–H2O system using a hydrothermal diamond-anvil cell (HDAC). The results showed that MnWO4 dissolved in alkali-carbonate aqueous solutions and, in some cases, in associated carbonate melts during heating, and subsequently, huebnerite crystallized into needle and column shaped crystals during cooling. In situ Raman spectra obtained during heating of the experimental charge in the sample chamber of the HDAC showed that WO42− was the only tungsten-bearing ion detected in the carbonate melt or aqueous solution. The dissolution of MnWO4 mainly attributed to the alkaline environment in the alkali-carbonate aqueous solution. Furthermore, the weak alkali condition in the carbonate solutions enhanced the crystallization of huebnerite when the temperature and pressure were decreased. The experimental results indicate that although the crystallization temperature–pressure conditions of huebnerite vary in a wide range, conditions lower than approximately 200 MPa and 450 °C are not favorable for huebnerite crystallization. Our experimental results also suggest that the alkali-carbonate aqueous solution could serve as a medium for the transport of tungsten in the ore-forming process.

In-situ elemental and isotopic compositions of apatite and zircon from the Shuikoushan and Xihuashan granitic plutons: Implication for Jurassic granitoid-related Cu-Pb-Zn and W mineralization in the Nanling Range, South China

The Nanling Range, South China, was world-famous for hosting abundant granitoid-related copper-lead-zinc (Cu-Pb-Zn) polymetallic ore deposits and quartz vein-type wolframite (W) ore deposits, both of which have roughly similar formation ages predominately between 150 and 160 Ma with a peak of ca. 156 Ma. In this study, accessory minerals from typical Cu-Pb-Zn-bearing and W-bearing granitic rocks are compared in terms of elemental and isotopic compositions. Apatite from W-bearing granites in the Xihuashan pluton has lower εNd(t) value (−11.9 to −8.6) than that from Cu-Pb-Zn-bearing granitic rocks in Shuikoushan with εNd(t) value of −8.7 to −4.2 and initial 87Sr/86Sr ratio of 0.7097–0.7109. Zircon grains in Xihuashan, yielded εHf(t) value from −14.9 to −11.4, δ18O value from 8.6‰ to 10.4‰, and highly variable and negative δ7Li value (−45.8‰ to −3.8‰), whereas those in Shuikoushan have relatively higher εHf(t) value (−10.6 to −8.1), lower δ18O value (8.4‰–9.7‰), and highly variable δ7Li values from −12.7‰ to +17.6‰. In situ Hf-O-Li isotopic compositions of zircon and Sr-Nd isotopes of apatite, suggesting that the Shuikoushan granitic pluton was likely generated from dehydration melting of amphibolite from a metal-fertile mafic source in the middle-to-lower crust, whereas the Xihuashan granitic pluton could be derived from partial melting of metapelite with minor amphibolite in the middle to upper crust. The geochemical records in accessory minerals fingerprint that the Shuikoushan granitic magma was characterized by high Cl content (0.11–1.44 wt%) and logfo2 value (>ΔFMQ+1), whereas the Xihuashan granitic magma have elevated F (3.51–4.80 wt%) and Li (3.49–42.4 ppm) contents with low logfo2 value (<FMQ+0), which suggested moderately oxidized magmas with high Cl contents are in favor of the formation of magmatic-hydrothermal Cu-Pb-Zn deposits, whereas weakly reduced magmas with high F and Li contents could be involved in the formation of the quartz vein-type wolframite deposits. In conclusion, different source rocks and magmatic evolution processes are the key to the understanding of the Jurassic diverse granitoid-related mineralization in the Nanling Range.

Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China

The giant Yaogangxian tungsten deposit, situated in the central Nanling region of South China, is one of the largest tungsten deposits in China. It comprises both large-scale wolframite–quartz vein-type and scheelite–skarn mineralization. The wolframite–quartz vein-type mineralization can be divided into three successive hydrothermal vein-forming stages, based on mineral paragenesis and crosscutting relationships: stage 1 (early) wolframite–cassiterite–quartz veins, also termed “main-stage” veins, characterized by significant wolframite deposition; stage 2 sulfide–quartz veins, where abundant sulfide minerals were introduced during vein formation; and stage 3 fluorite–carbonate–quartz veins that resulted from the latest hydrothermal event and commonly crosscut earlier veins. Fluid inclusion petrographic, microthermometric and Raman spectroscopic analyses were carried out on wolframite, quartz and fluorite. Three types of fluid inclusions were recognized in wolframite, quartz and fluorite: two-phase liquid-rich (type L), two-phase CO2-bearing (type CB), and CO2-rich fluid inclusions (type C). Secondary type L fluid inclusions were also recorded in wolframite. In main-stage veins, primary type L and CB inclusions occur in both wolframite and quartz crystals, whereas type C only occurs in quartz and coexists with type L. Type L and CB inclusions in wolframite exhibit homogenization temperatures of 280 to 360°C and 321 to 355°C, with salinities of 2.2 to 7.6 and 2.8 to 3.6wt% NaCl equivalent (NaCl equiv.), respectively. Secondary type L inclusions in wolframite have homogenization temperatures of 204 to 256°C, with salinities of 1.4 to 5.7wt% (NaCl equiv.), which similar to type L inclusions in quartz coexisting with sulfides, indicating that the sulfide-forming fluid is preserved as secondary inclusions in wolframite. Coexisting type L and C inclusions in quartz display similar homogenization temperature ranges (244 to 317°C) but contrasting salinity ranges of 4.2 to 7.3 and 0.2 to 2.8wt% NaCl equiv., respectively, suggesting fluid immiscibility during stage 1 quartz formation. In stage 2 veins, type L inclusions in quartz that coexists with sulfides have lower homogenization temperatures (219 to 276°C) and salinities (2.1 to 5.7wt% NaCl equiv.). Type L inclusions in fluorite from stage 3 veins show the lowest homogenization temperatures (183 to 205°C) and salinities (1.1 to 3.0wt% NaCl equiv.). The significantly higher homogenization temperatures of fluid inclusions in wolframite than in coexisting quartz, and their observed paragenesis, indicates that wolframite was precipitated earlier than most of the coexisting quartz. H–O isotopic data, the presence of primary CO2-bearing inclusions in wolframite, and the temperature vs. salinity trends of fluid-inclusion data indicate that wolframite was most likely deposited during cooling from an initial CO2-bearing magmatic fluid; while subsequent fluid immiscibility and mixing resulted in massive quartz precipitation and sulfide mineralization. Combining the spatial distribution characteristics of vein mineralization, our study results provide new guide lines for mineral exploration. The veins containing fluid inclusions that are characterized by high homogenization temperatures and high salinities are dominated by magmatic water. Therefore in the areas where abundant sulfides and carbonates occur, the potential for tungsten-rich ore-veins is in the deeper part of the deposit.

Fluid-rock interaction is decisive for the formation of tungsten deposits

Tungsten mineralization is typically associated with reduced granitic magmas of crustal origin. While this type of magmatism is widespread, economic tungsten deposits are highly localized, with ∼90% produced from only three countries worldwide. Therefore, the occurrence of reduced magmatism, while necessary for tungsten enrichment, seems to be insufficient to form such rare deposits. Here we explore the mechanisms that lead to wolframite precipitation and evaluate whether they may exert a decisive control on tungsten global distribution. Tungsten differs from other rare metals enriched in magmatic-hydrothermal ore deposits because it is transported as an anionic species. Precipitation of the main tungstate minerals scheelite, CaWO 4 , and wolframite, (Fe, Mn)WO 4 , thus depends on the availability of calcium, iron, or manganese. We demonstrate quantitatively that magmatic fluids at Panasqueira, Portugal, provide tungsten in solution, whereas the host rock contributes the iron required to precipitate wolframite. The combination of special source conditions with specific reactive host rocks explains why major wolframite deposits are rare and confined to a few ore provinces globally.

Textural and Chemical Constraints on the Formation of Disseminated Granite-hosted W-Ta-Nb Mineralization at the Dajishan Deposit, Nanling Range, Southeastern China

The Dajishan deposit, located in the Nanling Range of southeastern China, is the largest wolframite deposit in the world. Approximately two-thirds of the tungsten resource is contained in large quartz-wolframite-K-feldspar-muscovite-scheelite-sulfide-(beryl) veins, but the remainder occurs as wolframite and lesser scheelite, disseminated through the Nb-Ta mineralized No. 69 granite, which is characterized by abundant snowball quartz crystals. Disseminated granite-hosted wolframite mostly occurs as a replacement after lath-shaped muscovite, although an interstitial variety is present in some samples. The major element chemistry of the disseminated and vein-hosted wolframite is similar, however, the former has one to two orders of magnitude higher concentrations of high field strength elements (HFSE), including Nb and Ta. Disseminated muscovite in the No. 69 granite is Fe and Mg rich. Replacement rims on these muscovite crystals are enriched in Ta, Sn, and Cs, but more depleted in Nb, related to the original phase. Vein-hosted muscovite is characterized by lower Nb, Ta, Rb, and Cs contents than the granite-hosted muscovite, although Sn and W concentrations are comparable. Columbite-(Mn) is the principal Nb-Ta ore mineral and occurs disseminated through the No. 69 granite. Where it is hosted by snowball quartz crystals, some of the columbite has been altered and overgrown by wodginite. The restriction of these altered columbite crystals to within snowball quartz, along with the Ta and Sn enrichment of the alteration rims on muscovite, tie the formation of snowball quartz to a Ta-(Sn) metasomatic event. High Ge/Ti and Al/Ti ratios in the snowball quartz relative to interstitial quartz are also consistent with a late stage of formation for the former variety. The disseminated, granite-hosted W mineralization formed through fluid-rock interaction. The fluids that precipitated the disseminated wolframite were most likely those that formed the veins, but were modified through reaction with the HFSE-enriched No. 69 granite. Nb-Ta mineralization, however, is represented by magmatic columbite and by a later metasomatic stage of wodginite. The low solubility of Ta in aqueous fluids, combined with the evidence for Ta-(Sn) metasomatism, suggests that the Ta-(Sn) metasomatic event was caused by hydrosilicate liquids, a transitional fluid that lies compositionally between silicate magmas and hydrothermal fluids. Whole-rock and mineral chemistry both suggest that deep-level fractional crystallization of the No. 69 granite was required to elevate Ta and Nb concentrations to allow saturation of columbite.

A Preliminary Review of Metallogenic Regularity of Tungsten Deposits in China

AbstractTungsten ore resources are abundant in China with relatively complete types of deposits. Skarn type and quartz vein type deposits are dominated in the tungsten resources, whereas quartz vein type wolframite deposits are most important in terms of exploitation and utilization. Skarn type tungsten deposits are concentratedly distributed in the central Nanling region, such as South Hunan, South Anhui and the eastern Qinling region, while quartz vein type tungsten deposits occur mainly in South China, such as West Fujian, South Jiangxi, North Guangdong and South Hunan. The most important metallogenic epoch of tungsten is the Mesozoic, while the metallogenic tectonic setting is featured by an intracontinental environment after orogeny with sever tectonic movements, deep‐seated faults and frequent magmatic activities, especially Mesozoic granitoids closely related to tungsten‐tin mineralization. 22 metallogenic series of ore deposits characterized by or significantly related to tungsten were defined based on precise statistic information of 1199 tungsten mining areas and thorough the summary of metallogenic regularities. Based on studies of the metallogenic regularity of tungsten deposits, skarn type (or greisen type), quartz vein type and massif‐type of tungsten deposits are thought to be the key prediction types. 65 tungsten‐forming belts and 22 key ore concentration areas were ascertained and a distribution map of tungsten‐forming belts of China was compiled, which provided a theoretical basis for evaluation and prediction of potential tungsten resources.

A predictive model for the PVTx properties of CO2–H2O–NaCl fluid mixture up to high temperature and high pressure

A predictive thermodynamic model is constructed to calculate the pressure–volume–temperature–composition (PVTx) properties of CO2–H2O–NaCl fluid mixtures by the Helmholtz free energy model of CO2–H2O fluid mixtures. The new model uses no other mixing parameters but those of the CO2–H2O system, because the Helmholtz free energy of H2O–NaCl fluid at a given composition is equivalently converted into that of pure H2O by a scaled temperature redefined at the same pressure. In addition, the parameters developed by Driesner (2007) in the PVTx model of H2O–NaCl fluid system are refitted by the IAPWS-95 formulation. Comparisons with experimental data available show that the model can reproduce the single-phase PVTx properties of H2O–NaCl and CO2–H2O–NaCl fluid mixtures of all compositions from 273 to 1273K and from 0 to 5000bar, within or close to experimental uncertainty in most cases (with slightly lower accuracy at 5000–10,000bar). The isochores of CO2–H2O–NaCl fluid can be obtained from this model by a bisection algorithm, and an application example is given to analyze some natural CO2–H2O–NaCl fluid inclusions in quartz from a wolframite deposit. Computer program code for calculation of molar volume of the CO2–H2O–NaCl fluid as a function of temperature, pressure and composition can be obtained from the corresponding author (maoshide@163.com).

Dynamics on the Formation of Quartz‐Vein Wolframite Deposits In the Dajishan Area, Jiangxi Province, China

Dynamics on the Formation of Quartz‐Vein Wolframite Deposits In the Dajishan Area, Jiangxi Province, China

Degana (Rajasthan, India) and Tigrinoe (Primorye, Russia) tungsten and tin-tungsten deposits: Composition of mineral-forming fluids and conditions of wolframite deposition

Formation conditions of orebodies and conditions of wolframite deposition at the Degana tungsten deposits in Rajasthan, India and the Tigrinoe tin-tungsten deposit in the Russian Far East were studied. Differences in the composition and state of fluid systems were established by microthermometric study of fluid inclusions (FI) and thorough petrographic examination of FI. At the Degana deposit, the ore veins in granite were formed from K-Na-Ca-(Mg, Fe, etc.) chloride solutions with a salinity up to 36 wt % NaCl equiv at a temperature of >420 to 120°C and under a pressure reaching 1550 bar. The formation temperature of the orebodies hosted in breccia reached 450°C and pressure was below 400 bar. The salinity of mainly Nachloride aqueous solutions was no higher than 18 wt % NaCl equiv. At the Tigrinoe deposit, the temperature during formation of quartz-wolframite-cassiterite veins varied from 420 to 240°C and the pressure was no higher than 300 bar. The salt concentration of Na-chloride solutions was 7-3 wt %. Wolframite crystallized at the very beginning of ore deposition. Probable sources of fluids are discussed. It is suggested that the factors controlling wolframite deposition could have been different even at the same deposit.

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.

Geology, geochemistry and age of the Hukeng tungsten deposit, Southern China

The Hukeng tungsten deposit, located in the Wugongshan area in central part of Jiangxi province, South China, is a large-scale quartz-vein wolframite deposit. It is hosted in the Hukeng granitic intrusion. Based on the mineral assemblage and crosscutting relationship of the veins, three mineralization stages are identified, including: (1) quartz–wolframite stage, (2) quartz–fluorite–wolframite stage, and (3) quartz–pyrite–sphalerite–wolframite stage. The homogenization temperatures of fluid inclusions in vein quartz vary from 220 to 320 °C, and the salinities are from 0 to 10 wt.% NaCl equiv.; corresponding densities range from 0.7 to 1 g/cm 3. These features indicated that the ore-forming fluids in the Hukeng tungsten deposit have medium temperature, low density and low salinity. The δ 18OSMOW values of quartz range from 10.8‰ to 14.4‰, with corresponding δ 18O fluid values of 3.7‰ to 7.7‰, and δD values of fluid inclusions of between − 70‰ and − 55‰. The combined isotopic data indicate that the ore-forming fluids of the Hukeng tungsten deposit were mainly derived from magmatic water, with some minor input from meteoric water. We have carried out molybdenite Re–Os and muscovite 40Ar/ 39Ar dating to constrain the timing of mineralization. Re–Os dating of six molybdenite samples yielded model ages ranging from 149.1 ± 2.0 to 150.7 ± 3.7 Ma, with an average of 150.0 Ma. The Re–Os analyses give a well-defined 187Re/ 187Os isochron with an age of 150.2 ± 2.2 Ma (MSWD = 0.60). Hydrothermal muscovite yields a plateau 40Ar/ 39Ar age of 147.2 ± 1.4 Ma. 40Ar/ 39Ar age is in good agreement with the Re–Os age. These ages show that the timing of tungsten mineralization occurred at about 150 Ma. Our new data, when combined with published geochronological results from the other major deposits in this region, suggest that widespread W mineralization occurred in the Late Jurassic throughout South China.

Infrared microthermometric and stable isotopic study of fluid inclusions in wolframite at the Xihuashan tungsten deposit, Jiangxi province, China

The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO2-rich inclusions, two-phase pure CO2 inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239–380°C, 3.8–13.7 wt.% NaCl equiv) compared with those in quartz (177–329°C, 0.9–8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy–salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δ34S values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δ18O values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite.

Thermodynamic model of the formation of ore bodies at the Akchatau wolframite greisen-vein deposit

The Akchatau wolframite deposit in central Kazakhstan is a typical greisen deposit. Extensive geological and geochemical data, including those on numerous geochemical signatures (isotopic composition of O, H, C, noble gases, data on fluid inclusions, REE, and others) allowed us to decipher the physicochemical conditions and main factors that caused metasomatism and ore formation. Physicochemical modeling by the HCh program package (designed by Yu.B. Shvarov) was applied to reconstruct the composition of the greisenizing solution, cooling, boiling, interaction with granites; condensation of the gas phase; and fluid mixing. The predominant species of W transfer, (NaHWO4 aq0), and precipitation factors were determined. In small ore bodies, precipitation was caused by a temperature decrease. The precipitation of wolframite in near-vein greisens is related to the interaction of boiling highly mineralized solutions with host granites. Boiling does not affect wolframite precipitation but increases the content and ore potential of the greisenizing fluids, facilitating the formation of high-grade wolframite ores. In the filling veins of these bodies, ore precipitation is related to the dilution of solutions by weakly mineralized exogenic waters and the condensate of the gas phase. Tungsten mineralization of the Akchatau deposit was formed in an oxidizing environment, which is controlled by granite minerals during mobilization of ore components.

Unit-cell intergrowth of pyrochlore and hexagonal tungsten bronze structures in secondary tungsten minerals

Structural relations between secondary tungsten minerals with general composition A x [(W,Fe)(O,OH) 3] · y H 2O are described. Phyllotungstite ( A=predominantly Ca) is hexagonal, a = 7.31 ( 3 ) Å , c = 19.55 ( 1 ) Å , space group P6 3/ mmc. Pittongite, a new secondary tungsten mineral from a wolframite deposit near Pittong in Victoria, southeastern Australia ( A=predominantly Na) is hexagonal, a = 7.286 ( 1 ) Å , c = 50.49 ( 1 ) Å , space group P-6 m2. The structures of both minerals can be described as unit-cell scale intergrowths of (111) py pyrochlore slabs with pairs of hexagonal tungsten bronze (HTB) layers. In phyllotungstite, the (111) py blocks have the same thickness, 6 Å, whereas pittongite contains pyrochlore blocks of two different thicknesses, 6 and 12 Å. The structures can alternatively be described in terms of chemical twinning of the pyrochlore structure on (111) py oxygen planes. At the chemical twin planes, pairs of HTB layers are corner connected as in hexagonal WO 3.

Geochemistry and Tungsten Metallogeny of the Balda Granite, Rajasthan, India

Balda granite occurs along the western margin of the middle Proterozoic South Delhi Fold Belt. It is a medium grained leucogranite associated with tungsten mineralisation. Wolframite mineralisation is confined to pneumatolytic quartz veins and greisenised pegmatites located mainly along shear zones within Balda granite and neighbouring metasediments. Geochemistry of Balda granite suggests that it is highly evolved, peraluminous and volatile -rich granite formed from the melt derived by partial melting of metasediments. Borates and fluorides in various complexes favoured the concentration of W in the melt, whereas sodium cations, chlorides and phosphates were the carrier of tungsten in fluid. The shear zones developed within Balda granite and neighbouring metasediments provided the channelways for fluid movement and deposition of wolframite.

Wolframite - stibnite mineral assemblages from Rizana Lachanas, Macedonia, Greece and their possible use as flux agent in the manufacturing of clinker

In the current study it is investigated the possibility of use of wolframite and stibnite ore from Lachanas area, Northern Greece, as flux agent in the production of cement. The stibnite and wolframite deposits of that area are typical of the Sb-W type of mineralization. The Sb ore occurs more massive and volumetrically more extended than W ore. The ore bodies have been partially altered to secondary minerals of oxidation zone. The neoformed minerals have affected the original Sb and W content of the ore. However the oxidation of the deposit does not affect its use as flux agent in cement industry. It is well known that the most energy demanding stage in the cement industry is the sintering process. It has been found that certain additives may accelerate the sintering reactions and improve the reactivity of the cement raw mix. The minerals, iron rich wolframite, stibnite and a wolframite-stibnite assemblage were selected in order to introduce W, Sb and S in the cement raw mix. One reference sample and 12 test samples prepared by mixing the reference sample with the above minerals in 0.5,1.0,1.5 and 2.0% w/w were studied. The effect on the reactivity of the raw mix is evaluated on the basis of the un-reacted lime content in samples sintered at 1000, 1100, 1200, 1300, 1350, 1400 and 1450°C. It is concluded that minerals containing Sb promote the consumption of the free lime, in the most effective way. The XRD studies, performed in samples that were burned at 1450°C, showed that the diffraction patterns correspond to a structure of a typical clinker, obtained at the above temperatures.