Wolframite Precipitation Research Articles

Origin of the Narenwula quartz vein-type W deposit, Inner Mongolia, China: Insights from geochemistry of hosting granites, fluid inclusions, H-O-S isotopes, and wolframite trace elements

Wolframite that coexists with quartz is common hydrothermal mineral in tungsten deposits, and its geochemical features can be used to constrain the tungsten mineralization. Here we show that the Narenwula deposit is a typical quartz vein-type W deposit on the northern margin of the North China Craton, Northeast China, and temporally and spatially associated with Early Cretaceous granitoids, provides an opportunity to decipher the W mineralization process. All the orebodies are composed of a series of northeast- trending wolframite-polymetallic sulfides bearing quartz veins accompanied by intense alterations, mainly hosted in the Early Cretaceous monzogranite and porphyraceous monzogranite. Three paragenetic stages were identified: (I) quartz-wolframite, (II) quartz-wolframite-sulfide, and (III) quartz-fluorite-calcite. LA−ICP−MS trace element analyses revealed that both wolframite (I) and (II) have similar trace elements, REEN patterns, and overall consistent Nb/Ta and Y/Ho ratios, indicate a single fluid source and evolution in the W mineralization of the Narenwula deposit. Fluid inclusions microthermometry of quartz and wolframite, coupled with H-O isotopes suggest that the early ore-forming fluids of the Narenwula deposit are mainly magmatic water with relatively moderate-to-high temperature and salinity, while the late ore-forming fluids are mixed with meteoric water, with medium-to low temperature and low salinity. The δ34S values of pyrite (4.63–6.65 ‰, average = 5.44 ‰) further support a magmatic origin for the sulfides. The metallogenic mechanisms at the Narenwula deposit include fluid boiling and fluid-rock interactions were the two major factors controlling the deposition of wolframite and sulfide, while simple cooling and fluid mixing may have also promoted wolframite precipitation.

Unraveling the genesis of wolframite mineralization in the West Qinling Belt, China: Evidence from geochronology, geochemistry, and fluid inclusion study

The West Qinling Belt is a pivotal part of the Central China Orogenic Belt renowned for producing abundant Au-polymetallic deposits. Nonetheless, reports of wolframite mineralization within this region were absent. The Xuehuashan deposit is the premier documented quartz-vein type wolframite deposit in West Qinling, which has significant implications of W mineralizing potential in the West Qinling Belt. The ore bodies are predominantly composed of wolframite-quartz veins and/or veinlets which are proximal or within the Late Triassic Baijiazhuang granitoid. To elucidate the age and genesis of the Xuehuashan wolframite mineralization, we presented analyses of U-Pb dating and chemical composition on wolframite, fluid inclusion study, and hydrogen–oxygen isotopes on wolframite and quartz. The Xuehuashan wolframite U-Pb dating yielded an age of 213.0 ± 6.7 Ma, which is consistent with the age of the Baijiazhuang granitoid. The correlation among trace elements and the Y/Ho vs. Zr/Hf diagram suggests trace elements in wolframite were influenced by crystalline chemical factors and the geochemistry of parental ore-forming fluid. Homogeneous texture and stable chemical composition of wolframite, as well δD vs. δ18O isotopes, suggest a single magmatic fluid from the Baijiazhuang granitoid. Fluid inclusions in wolframite and quartz have high homogenization temperatures and varying salinities of 0.4 – 16.4 wt%, suggesting that intense decompression and fluid boiling during fracture open caused the wolframite precipitation. Compared with the Late Triassic granitoids in the Qinling Belt, the Baijiazhuang granitoid shows higher ratios of Rb/Sr and lower ratios of Zr/Hf, K/Rb, Nb/Ta, LREE/HREE, as well as negative Eu anomalies, which are consistent with the W-related highly evolved granitoids but distinct to W-barren granitoids. Hence, this study highlights W mineralization potential in the Qinling belt associated with the highly evolved Late Triassic granitoids.

Tracing the Fe-enriched quartz vein-type wolframite mineralization: Wolframite U-Pb dating and compositions of wolframite and scheelite from the Anglonggangri and Jiaoxi areas, Xizang, China

Critical factors controlling Fe-enriched wolframite formation in the quartz vein-type wolframite deposit are in controversy. The Jiaoxi and Anglonggangri are typical examples of quartz vein-type wolframite mineralization found in western Lhasa terrane. The Jiaoxi wolframite comprise dominantly early hübnerite with late ferberite, whereas, the Anglonggangri wolframite are mainly ferberite. Wolframite U-Pb dating yields direct timing of 11.0 ± 0.2 Ma and 9.7 ± 0.2 Ma for Jiaoxi and Anglonggangri tungsten mineralization, respectively. Ages together with enrichment of Nb, Ta, Ti, and Sc and depletion of Sr and most Eu anomaly within Anglonggangri wolframite confirm that metals and fluids were mainly derived from the ore-forming garnet-muscovite granite. Iron and Mn mapping of garnet in the garnet-muscovite granite suggests this granite has changed from the early Mn-enriched to late Fe-rich affinity. Therefore, initial ore-forming fluids exsolved from garnet-muscovite granite have Fe-rich composition, that was significantly modified during tungsten mineralization. Positive trend between Mg and Fe/(Fe + Mn) of wolframite indicates biotite breakdown from country rock of biotite-muscovite granite to add Fe and Mg into fluid during greisenization. Meanwhile, decomposition of plagioclase and K-feldspar provided Ca, Sr, and Eu to form late scheelite. Enrichment of Sr with positive Eu anomaly and decline of REE, Nb, and Ta are typical features of the highly evolved and modified fluid. Positive and negative Eu anomalies within the same wolframite grains reveal the oxidized character and fluctuating composition of fluid during wolframite precipitation. By contrast, negative Eu anomaly and low Mo abundance of scheelite indicate the reducing fluid during scheelite crystallization. Identification of metal and fluid sources for Anglonggangri ferberite highlights the evolved granites play more crucial roles on ferberite formation than early hübnerite crystallization and Fe addition from country rocks during hydrothermal interaction.

Tracing metal source of copper-rich tungsten mineralization: Evidence from individual fluid inclusion analysis of the Huangsha Cu-rich W deposit in South China

The Huangsha Cu-rich W deposit, located in the northeast part of the Nanling region, is a typical large-size wolframite-quartz vein-type W deposit with considerable reserves of copper. Wolframite and chalcopyrite usually distribute in the same quartz veins, while field and petrographic observation show that wolframite commonly precipitates earlier than coexisting quartz and sulfides. Veined quartz can be divided into three successive generations (Q1, Q2, and Q3) based on SEM-CL imaging, and only Q2 is strictly coeval with chalcopyrite and other sulfides. Primary two-phase aqueous (type Lw) fluid inclusions are identified from wolframite with homogenization temperatures of 292 to 327 ℃ and salinities of 6.9 to 9.9 wt% NaCl equiv. Pseudosecondary two-phase aqueous (type Lq) and vapor-rich (type Vq) fluid inclusions are recognized from Q2, supporting the occurrence of fluid immiscibility. Homogenization temperatures of type Lq inclusions in Q2 range from 200 to 258 ℃ with salinities of 4.3 to 7.7 wt% NaCl equiv. LA-ICP-MS analysis shows that all inclusions contain Na and K as the major cations. For all the detected elements, type Lw inclusions in wolframite have higher concentration ratios X/Na than type Lq inclusions to varying degrees. The ore-forming fluid in both W and Cu mineralization stages share the same characteristics of high B concentrations, consistent Rb/Cs ratios and evolving nature of ore metals, indicating that W and Cu were sourced from the same magmatic fluid but precipitated in different mineralization stages. The variation of fluid Sr concentration likely indicates fluid-rock interaction during precipitation of wolframite, whereas the deposition of chalcopyrite is possibly influenced by fluid cooling and immiscibility. Compared with typical porphyry Cu systems and W/Sn mineralized systems worldwide, the ore-forming fluid in the W mineralization stage at Huangsha shows considerably higher mineralization potential of Cu, which is consistent with the geological fact. The Cu contents in initial W ore-forming fluids may serve as an indicator in identifying Cu-rich W deposits.

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.

From granite to highly evolved pegmatite: A case study of the Shangkelan rare-metal granite–pegmatite system (Altai, NW China)

The Shangkelan granite–pegmatite is known for its internal zonation and tungsten mineralization in the Chinese Altai. However, the genetic relationship between the granite and pegmatite and the W mineralization mechanism in Shangkelan remains unclear. Here we present monazite U–Pb ages and Nd isotopic composition, and whole-rock and muscovite chemical compositions of each zone of the stock, to address these issues. From bottom to top, the stock mainly consists of alkali-feldspar granite (AFG) and granitic pegmatite (GP). Monazite LA-ICP-MS U–Pb dating and Nd isotopic analyses reveal that the AFG and GP have identical ages and similar εNd(t) values, 189 ± 2 Ma and −0.79–+0.38 and 190 ± 1 Ma and −0.70–+0.01, respectively. Whole-rock geochemical results show that the stock is highly fractionated and has a differential trend characterized by increasing Rb, Cs, and Tl contents, decreasing W, Ba, and Sr contents, and Zr/Hf ratios from the AFG to GP. Both primary (magmatic) and secondary (hydrothermal) muscovites have been recognized in Shangkelan. From the AFG to GP, element concentrations and ratios of primary muscovite form well-defined differentiation trends marked by gradual increases in Rb, Cs, and Nb, and decreases in W, K/Rb, and Nb/Ta. Based on the gradational contacts in field, identical monazite ages, and similar Nd isotopic compositions, together with the differentiation trends of incompatible elements (such as Rb and Cs) in bulk-rock and primary muscovite and alkali metal Rayleigh fractionation modeling results, we consider that the AFG is parental to GP and they were produced by continuous fractional crystallization of a common magma source. Additionally, for the monazites Nd isotopes, their two-stage Nd model ages of 1034–939 Ma and slightly negative to positive εNd(t) values (−0.79–+0.38) indicate that the magma sources were mainly derived from the reworking of the Stenian–Tonian basement. Secondary muscovite precipitated from the fluids that exsolved from the parental AFG melt has high contents of F and W. Tungsten may be dissolved as H3WO4F2− in the fluids. The greisenization caused the destabilization of H3WO4F2− and eventually led to the precipitation of wolframite in Shangkelan.

In-situ trace element and Li-isotope study of zinnwaldite from the Degana tungsten deposit, India: Implications for hydrothermal tungsten mineralization

Zinnwaldite, a Li, Rb-mica is a common magmatic or hydrothermal mineral in many tungsten deposits. In this study, we use the trace element and Li-isotope composition of zinnwaldite from Degana, the largest tungsten deposit of India, to constrain the source and evolution of the ore fluid, the precipitation mechanism of W and the roles of fractional crystallization, fluid exsolution and fluid-rock interaction in the mineralization process. Textural evidence suggests that the mineralization in the Degana rocks involved at least two stages of fluid infiltration. The earlier of the two was multi-pulsed and responsible for the primary tungsten and zinnwaldite mineralization. The second hydrothermal stage caused partial dissolution and reprecipitation of both wolframite as well as zinnwaldite, reflected in the patchy zones that replace both minerals. The ore fluid had high concentration of Li, Rb, Cs, Nb, and Ta as evident from zinnwaldite chemistry. The δ7Li of the ore fluid (+14 to +19 ‰), estimated from the Li-isotope composition of zinnwaldite in mineralized veins (δ7Li = +12 to +17‰), is significantly heavier compared to upper/middle continental crust, ruling out the possibility of a metamorphic fluid source. The high concentration of incompatible elements including Cs, extremely low K/Rb (10–15), is best explained by its growth from fluids exsolved from an enriched, late-fractionated granitic melt. Alteration of the host granite, formation of greisen, large-scale albitization and muscovitization are indicative of fluid-rock interaction, which might have increased the fluid pH, destabilizing fluoride complexes of W, resulting in the precipitation of wolframite. The shift in the chemical and Li-isotope composition from the early mica to late altered ones in the greisen indicates interaction of the hydrothermal fluid with the host rocks. A U-Pb Concordia age of 838 ± 9 Ma retrieved from magmatic domains of zircon from the Degana granite dates it emplacement and represents the maximum age of the W-mineralization.

Genesis and Fluid Evolution of the Hongqiling Sn-W Polymetallic Deposit in Hunan, South China: Constraints from Geology, Fluid Inclusion, and Stable Isotopes

The Hongqiling is a vein-type Sn-W polymetallic deposit in southern Hunan (South China). It is geologically located on the northern margin of the Nanling metallogenic belt. Based on the mineral assemblage and vein crosscutting relationship, three mineralization stages were identified: Sn-W mineralization (S1: cassiterite, wolframite, scheelite, arsenopyrite, molybdenite, pyrite, chalcopyrite, and quartz), Pb-Zn mineralization (S2: chalcopyrite, pyrrhotite, galena, sphalerite, pyrite, quartz, and fluorite), and late mineralization (S3: quartz, fluorite, calcite, galena, sphalerite, and pyrite). According to laser Raman probe analysis, H2O dominates the fluid inclusions in the S1 and S2 stage quartz, with CO2 and trace N2 following close behind. The ore fluid has low salinity, low density, and a wide temperature range, as per our microthermometric data: the S1 stage has homogenization temperatures (Th) of 236–377.6 °C (average 305.3 °C) and salinity of 3.5–10.7 wt.% NaCleqv; the S2 stage has Th of 206.5–332 °C (average 280.7 °C) and salinity of 1.6–5.1 wt.% NaCleqv; and the S3 stage has Th of 170.9–328.7 °C (average 246 °C) and salinity of 0.2–5.9 wt.% NaCleqv. Based on the results of the aforementioned investigation, the fluid inclusions in quartz, fluorite, and calcite are mainly H2O-NaCl vapor-liquid two-phase. Additionally, examinations of inclusions in S1 wolframite and coexisting quartz using infrared and microthermometry show that the mineralizing fluid likewise belongs to the NaCl-H2O system. The Th of inclusions in wolframite is ~40 °C higher than that of coexisting quartz. Moreover, the fluid experienced a decrease in temperature accompanied by nearly constant salinity, which indicates that wolframite precipitation is due to fluid mixing and simple cooling, and the precipitation is earlier than quartz. In situ S and H-O isotope data show that the samples have δ34S = −2.58‰ to 1.84‰, and the ore fluids have δD = −76.6 to −51.5‰ (S1 and S2), and δ18Ofluid = −6.6 to −0.9‰ (S1) and −12.9 to −10.2‰ (S2). All these indicate that the mineralizing fluid was derived from the granitic magma at Qianlishan, with substantial meteoric water incursion during the ore stage. Such fluid mixing and subsequent cooling are most likely the primary controls for ore deposition.

Formation and evolution of multistage hydrothermal fluids in the Baishitouwa quartz–wolframite vein‐type deposit in the southern Great Xing'an Range tungsten belt, NE China: Constraints from individual fluid inclusion LA‐ICP‐MS analysis

Revealing hydrothermal evolution from the early oxide to late carbonate stages for quartz–wolframite vein‐type deposits is essential for understanding the ore‐forming process. In this study, we choose the Baishitouwa tungsten polymetallic deposit located in the southern Great Xing'an Range tungsten belt as a case study, and present detailed deposit geology and in situ fluid inclusion (FI) analyses including microthermometry, laser Raman spectra, and LA‐ICP‐MS microanalysis to address this issue. Four stages of hydrothermal activity were identified: (1) quartz–wolframite (I), (2) quartz–wolframite (II)–pyrite–chalcopyrite, (3) quartz–polymetallic sulphides, and (4) quartz–carbonate. Four types of FIs were recognized: CO2‐rich, CO2‐bearing, liquid‐rich, and brine inclusions. Microthermometric data showed that the homogenization temperatures and salinities from the early to late stages are 380–460°C, 7.4–17.3, and 29.3–43.2 wt% NaCl equiv., 300–390°C and 7.1–17.0 wt% NaCl equiv., 220–320°C and 2.7–8.1 wt% NaCl equiv., and 150–250°C and 0.5–4.8 wt% NaCl equiv., respectively, suggesting a decreasing trend. Geochemically, all stage fluids contained high Rb and Mn concentrations, high Rb/Na, Cs/Na, Li/Na, K/Na, Rb/Sr, low K/Rb, and consistent Cs/Rb and Cs/(Na + K) ratios, indicating that the mineralizing fluids originated from a common source—an underlying, geochemically uniform, and highly fractionated granitic magma. Fluid immiscibility and cooling are the main mechanisms for wolframite precipitation, whereas greisenization is subordinate; the incursion of meteoric water into the hydrothermal system initiated at the sulphide stage, and fluid mixing is the dominant mechanism for sulphide precipitation.

Ore genesis of the Narenwula quartz-vein type W polymetallic deposit in the southern Great Xing’an Range W belt, NE China: Constraints from wolframite geochronology and individual fluid inclusion analysis

The Narenwula deposit, situated in the southern Great Xing’an Range W belt, is a large-scale quartz-vein type W polymetallic deposit in NE China. The mineralization is spatially associated with Late Jurassic monzogranite and granite porphyry. In this study, we present detailed description of the ore geology, wolframite in-situ U-Pb dating, and fluid inclusion analyses including microthermometry, laser Raman spectra, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) microanalyses to precisely constrain the timing of ore formation, origin and evolution of ore-forming fluids as well as metal precipitation mechanisms. In-situ U-Pb dating of hydrothermal wolframite yields a W mineralization age of 136.4 ± 2.0 Ma (1σ, MSWD = 1.3), which is ∼14 Ma younger than the zircon U-Pb ages of W-bearing granitoids, indicating the W-bearing granitoids are not genetically related to the W mineralization at Narenwula. The hydrothermal process can be divided into four stages: stage I is characterized by abundant wolframite (I), which is the dominant stage of W mineralization; stage II is featured with the development of wolframite (II) together with minor amounts of pyrite and chalcopyrite; stage III is the predominant stage of sulfide mineralization; and stage Ⅳ is characterized by lack of sulfide or wolframite and occurrence of quartz, carbonate, and fluorite. Cathodoluminescence analysis of quartz further revealed four generations of quartz, corresponding to the four hydrothermal stages. Four types of fluid inclusions were distinguished for quartz, including CO2-rich (C1-type), CO2-bearing (C2-type), liquid-rich (l-type), and brine (B-type) fluid inclusions. Fluid inclusion microthermometry shows a decrease in homogenization temperatures and salinities from the early to late stages. The ranges of the homogenization temperature for stages I to Ⅳ are 440–280, 320–240, 260–180, and 200–160 ℃, respectively, and the ranges of salinities for stages II to Ⅳ are 2.9–17.8, 1.4–10.2, and 0.4–6.7 wt% NaCl equiv., respectively. The salinities of fluid inclusions from stage I have a bimodal distribution in the ranges of 9.6–17.4 and 31.1–35.6 wt% NaCl equiv. Individual fluid inclusion LA-ICP-MS analyses suggest a magmatic source for the fluids of all stages, evidenced by the high Rb and Mn concentrations, high Rb/Na, K/Na, Cs/Na, Li/Na, and Zn/Na ratios, which are distinctly different from those of basinal brines. The Rb/Sr and K/Rb ratios of fluid inclusions are similar to those of Late Mesozoic highly fractionated W-mineralized granitoids in NE China, indicating that the metallogenic parent rocks at Narenwula are highly evolved. In combination with evidence of consistent Cs/Rb and Cs/(Na + K) ratios of fluid inclusions from all stages, we suggest that the mineralizing fluids originated from an underlying, geochemically uniform, and highly fractionated granitic magma. Fluid immiscibility and fluid-rock interaction (especially greisenization) are the main mechanisms for wolframite precipitation, whereas natural cooling of fluids may be subordinate. Fluid inclusion data provide evidence that the addition of meteoric water to the magmatic-hydrothermal fluid initiated at the sulfide mineralization stage, and the fluid dilution and cooling due to fluid mixing played an important role in the process of sulfide precipitation. This study highlights that W and base metals (e.g., Cu, Pb, Zn) in ore-forming fluids display different migration and precipitation progresses, the knowledge of which is important for elucidating multi-stage ore-forming processes of quartz-vein type W polymetallic deposits in NE China.

Records of fluid-rock interactions in the Degana tungsten deposit, India: Inferences from mineral paragenesis, whole-rock and mineral chemistry, and fluid inclusions

The Degana Granite, a F-rich, peraluminous, Neoproterozoic intrusion in NW India hosts the richest tungsten deposit in the country. This study on the Degana W deposit outlines its alteration history, and nature (and evolution) of pre-ore and ore-stage fluids. Moderate salinity (5.4 to 9.6 wt% NaCl equiv.), H2O-CO2 fluids with nearly consistent CO2/(H2O + CO2) ratios of 0.05–0.07 represent the magmatic stage. A pervasive, post-magmatic K (±Na) alteration occurred in a fluid regime dominated by moderate salinity H2O-CO2 fluids. In subsequent alteration stages, the activity of greisen fluids led to the development of steeply-dipping quartz veins (poorly-mineralized), sub-parallel wolframite-bearing greisenized granitic wall-rock (main ore body), and and a late phase of stockwork-type greisen veins. The greisenization is attributed to the incursion of moderate to high salinity (12–22 wt%) H2O-CO2 ore fluids. Such fluids led to K-feldspar and muscovite hydrolysis, and the growth of lithian ferroan muscovite, secondary topaz, and wolframite (±cassiterite, fluorite). Greisenization introduced additional Fe and Li (+W, Sn) in the wall-rock zone and concomitantly leached out Na, K, Cu, Ba, Sr, U, Zr, and Th. Greisen fluids caused Fe leaching along with incorporation of Li in the micas. The compositions of tri- and di-octahedral micas are controlled by distinct substitution mechanisms --VILi1+1IVSi4+2VIAl3+1VIξ1VIFe2+-3IVAl3+-2, and VILi1+4IVSi4+1VIFe2+-1IVAl3+-1VIAl3+-1VIξ-2 (where ξ = vacancy), respectively. We constrain the P-T conditions of W enrichment (380–450 °C and 1.2–1.8 kbar) by means of isochore intersections for coexisting aqueous and carbonic fluid inclusions hosted in greisenized wall rock. The fall in pH of the ore fluid due to fluid-silicate hydrolysis in concomitance with H2O-CO2 immiscibility promoted the decrease in W solubility and subsequent wolframite precipitation. It is surmised that the pervasive, post-magmatic potassic alteration that preceded the ore mineralization acted as a critical pre-conditioning process for ore formation. Both tri- and di-octahedral micas were critical for W enrichment, the former being the likely source for Fe (+W, Sn), and the latter as a reactant for pH-neutralization of greisen fluid, thereby limiting its W solubility.

Co-genetic formation of scheelite- and wolframite-bearing quartz veins in the Chuankou W deposit, South China: Evidence from individual fluid inclusion and wall-rock alteration analysis

The large-scale Chuankou W deposit is located in the north part of the Nanling metallogenic belt, South China. It comprises independent quartz vein-type scheelite and wolframite mineralization, both associated with the underlying granitic intrusion spatially. The scheelite-bearing quartz veins occur invariably in sandstone and slate to the west, whereas the wolframite-bearing quartz veins are mainly hosted by the granite to the east. To reveal the fluid characteristics of the two mineralizing vein systems, detailed petrography, microthermometry, and Raman spectroscopic analyses were carried out on fluid inclusions in scheelite, wolframite and their coexisting quartz. Major and trace element concentrations of fluids were obtained from individual fluid inclusions in quartz via LA-ICP-MS analysis. Wall-rock alteration of both vein systems were evaluated by TESCAN Integrated Mineral Analyser (TIMA) analysis, and based on which the bulk geochemical data of wall-rock as a function of distance from the vein were obtained for scheelite-bearing quartz vein. These data aid elucidation on the nature of fluids in the two types of W mineralization. Fluid inclusions in quartz and its coexisting tungsten minerals share similar homogenization temperature and salinity, suggesting near concurrent formation of quartz and ore minerals. LA-ICP-MS analyses on pseudosecondary fluid inclusions in quartz associated with ore minerals show considerable concentrations of W in both mineralizing fluids, whereas Fe, Mn and Ca are generally absent irrespective of their higher detection limits. This may imply that Ca, Fe, and Mn were not initially derived from the granitic magma. The fluid compositions of both types of W mineralization display similar Rb/Na, K/Na, and Rb/Cs ratios, indicating a similar initial fluid source. The TIMA image shows that the host rock (sandstone) of scheelite-bearing quartz vein contains abundant Ca-rich minerals, such as apatite and calcium feldspar, indicating wall-rock as potential source providing Ca for the precipitation of scheelite. This assumption is strongly supported by bulk geochemical data of wall rock as a function of distance from hydrothermal quartz vein. In contrast, the tourmaline-rich granite hosting wolframite quartz veins may be a potential source of Fe for the precipitation of wolframite. Study on fluid composition combined with wall rock alteration suggest that the magmatic-sourced fluids and fluid–wall-rock interactions exerted primary control on the large-scale variations in mineralization types in the deposit, with scheelite- and wolframite-bearing quartz veins being both genetically and spatially related. Results of this study provide new guidelines for mineral exploration, suggesting a homologous scheelite-dominated deposit being likely to exist in association with a wolframite-dominated deposit, where the lithology of Ca-bearing formations may indicate potential prospecting areas.

Fluid Evolution and Ore Genesis of the Juyuan Tungsten Deposit, Beishan, NW China

The newly discovered Juyuan tungsten deposit is hosted in Triassic granite in the Beishan Orogen, NW China. The tungsten mineralization occurred as quartz veins, and the main ore minerals included wolframite and scheelite. The age, origin, and tectonic setting of the Juyuan tungsten deposit, however, remain poorly understood. According to the mineralogical assemblages and crosscutting relationships, three hydrothermal stages can be identified, i.e., the early stage of quartz veins with scheelite and wolframite, the intermediate stage of quartz veinlets with sulfides, and the late stage of carbonate-quartz veinlets with tungsten being mainly introduced in the early stage. Quartz formed in the two earlier stages contained four compositional types of fluid inclusions, i.e., pure CO2, CO2-H2O, daughter mineral-bearing, and NaCl-H2O, but the late-stage quartz only contained the NaCl-H2O inclusions. The inclusions in quartz formed in the early, intermediate, and late stages had total homogenization temperatures of 230–344 °C, 241−295 °C, and 184−234 °C, respectively, with salinities no higher than 7.2 wt.% NaCl equiv (equivalent). Trapping pressures estimated from the CO2-H2O inclusions were 33−256 MPa and 36−214 MPa in the early and intermediate stages, corresponding to mineralization depths of 3–8 km. Fluid boiling and mixing caused rapid precipitation of wolframite, scheelite, and sulfides. Through boiling and inflow of meteoric water, the ore-forming fluid system evolved from CO2-rich to CO2-poor in composition and from magmatic to meteoric, as indicated by decreasing δ18Owater values from early to late stages. The sulfur and lead isotope compositions in the intermediate-stage suggest that the Triassic granite was a significant source of ore metals. The biotite 40Ar/39Ar age from the W-bearing quartz shows that the Juyuan tungsten system was formed at 240.0 ± 1.0 Ma, coeval with the emplacement of granitic rocks at the deposit. Integrating the data obtained from the studies including regional geology, ore geology, biotite Ar-Ar geochronology, fluid inclusion, and C-H-O-S-Pb isotope geochemistry, we conclude that the Juyuan tungsten deposit was a quartz-vein type system that originated from the emplacement of the granites, which was induced by collision between the Tarim and Kazakhstan–Ili plates. A comparison of the characteristics of tungsten mineralization in East Tianshan and Beishan suggests that the Triassic tungsten metallogenic belt in East Tianshan extends to the Beishan orogenic belt and that the west of the orogenic belt also has potential for the discovery of further quartz-vein-type tungsten deposits.

Constraining the genesis of tungsten mineralization in the Jiaoxi deposit, Tibet: A fluid inclusion and H, O, S and Pb isotope investigation

The Jiaoxi deposit, located in the western part of the Lhasa terrane, is the first discovered Miocene (ca. 13 Ma) quartz vein-type tungsten deposit in this belt. Ore bodies mainly occur as wolframite-bearing veins hosted in the shales and granite. Three stages were identified for the formation of the Jiaoxi deposit, including the oxide stage (dominated by wolframite and quartz), the sulfide stage (quartz-sulfides veins) and the fluorite stage (late veins comprising fluorite, calcite, and quartz). Here, we investigate the genesis of this deposit based on fluid inclusion and H-O-S-Pb isotope studies. Fluid inclusion microthermometry and oxygen isotope data reveal that the wolframite precipitated from a moderate temperature (340–380 °C), low salinity (2.1–7.5 wt% NaCl equivalent) hydrothermal fluid at a depth of ∼ 6 km. The sulfides from the oxide and sulfide stage have uniform δ34SCDT values (+2.5 to + 3.7‰), and consistent Pb isotope compositions with the coeval granites (206Pb/204Pb: 17.866–18.789; 207Pb/204Pb: 15.555–15.743; 208Pb/204Pb: 37.157–39.335). The δ18OVSMOW value of the hydrothermal fluid decreased from the oxide (δ18OVSMOW = +7.2 to +14.2‰) to the fluorite stage (δ18OVSMOW = +2.1 to +5.7‰), indicating that the exsolved magmatic hydrothermal fluid mixed with meteoric water. This is also suggested by the positive correlation between the salinity and homogenization temperature of the aqueous fluid inclusions. LA-ICP-MS analysis of individual fluid inclusion reveals that the W concentrations of ore-forming fluid in the oxide stage (1.2–70.2 ppm) are much higher than those in the sulfide and fluorite stage (1.1–2.2 ppm) and show positive correlations with the homogenization temperatures and the Cl concentrations. We propose that fluid dilution and cooling due to fluid mixing played an important role during the wolframite precipitation in the Jiaoxi deposit.

Episodic Precipitation of Wolframite during An Orogen: The Echassières District, Variscan Belt of France

Monazite and rutile occurring in hydrothermally altered W mineralizations, in the Echassières district of the French Massif Central (FMC), were dated by U-Pb isotopic systematics using in-situ Laser ablation-inductively coupled plasma–quadrupole mass spectrometry (LA-ICP-MS). The resulting dates record superimposed evidence for multiple percolation of mineralizing fluids in the same area. Cross-referencing these ages with cross-cutting relationships and published geochronological data reveals a long history of more than 50 Ma of W mineralization in the district. These data, integrated in the context of the Variscan belt evolution and compared to other major W provinces in the world, point to an original geodynamic-metallogenic scenario. The formation, probably during the Devonian, of a quartz-vein stockwork (1st generation of wolframite, called wolframite “a”; >360 Ma) of porphyry magmatic arc affinity is analogous to the Sn-W belts of the Andes and the Nanling range in China. This stockwork was affected by Barrovian metamorphism, induced by tectonic accretion and crustal thickening, during the middle Carboniferous (360 to 350 Ma). Intrusion of a concealed post-collisional peraluminous Visean granite, at 333 Ma, was closely followed by precipitation of a second generation of wolframite (termed “b”), from greisen fluids in the stockwork and host schist. This W-fertile magmatic episode has been widely recorded in the Variscan belt of central Europe, e.g. in the Erzgebirge, but with a time lag of 10–15 Ma. During orogenic collapse, a third magmatic episode was characterized by the intrusion of numerous rare-metal granites (RMG), which crystallized at ~310 Ma in the FMC and in Iberia. One of these, the Beauvoir granite in the Echassières district, led to the formation of the wolframite “c” generation during greisen alteration.

Nature of the mineralizing fluids in the Balda and Motiya W-prospects, western India: Constraints from chemical and B-isotope composition of tourmaline

In the Proterozoic tungsten belts of Balda and Motiya in western India, tungsten mineralization is hosted in tourmaline-bearing quartz veins intrusive into pelitic schists and granites. Tourmaline is a ubiquitous phase in all rock types, and in this study, we use its major, trace element and B-isotope composition to constrain the nature of the tungsten (W)-bearing hydrothermal fluid and the processes involved in the precipitation of wolframite. We have also reconstructed the compositions of the W-precipitating fluids from mineral-fluid trace element partition coefficients that were extrapolated using the Lattice Strain Model. The tourmalines from both belts are of schorl composition and have high alkali, low Ca content, and moderate X-site vacancies. High Li, Mn, Zn, and Sn in the fluid in Motiya is suggestive of relatively saline fluid possibly derived from a granitic source. The high V/Sc ratios of tourmalines in the mineralized veins and wall-rock tourmalinites indicate an important role of biotite dissolution and fluid-rock interaction that contributed Fe–Mn for the precipitation of tourmaline and wolframite. The tourmalines in the mineralized veins at Balda (δ11Btur = −10.9 ± 0.7‰, 2σ; n = 10) and those in the associated granites (δ11Btur = −11.5 ± 0.7‰, 2σ; n = 6) have similar B-isotope composition, while those of the associated topaz granites and pegmatites (−13.9 ± 0.7‰, 2σ; n = 19) are isotopically lighter than the granites. The B-isotopic variation in the granite-pegmatite-vein system can be explained by fluid exsolution with the mineralized vein forming from exsolved fluid and the topaz-bearing granites and the pegmatites crystallizing from the residual melts. The δ11B of the mineralizing fluid is estimated to be ca. −7.4‰ at Balda and ca. −7.6‰ at Motiya, and were possibly derived from granites, consistent with extensive tourmalinization and muscovitization of the adjacent wall rocks, and high concentration of elements such as F, Li, B, Sn, Mn in the tourmalines and the reconstructed fluid. The chemistry and B-isotope composition of tourmalines in both the belts support the hypothesis that W-bearing hydrothermal fluid was primarily derived from a fractionated granitic source, and that precipitation of wolframite and tourmaline involved interaction of the granitic fluid with surrounding pelitic rocks.

Ore Genesis of the Takatori Tungsten–Quartz Vein Deposit, Japan: Chemical and Isotopic Evidence

The Takatori hypothermal tin–tungsten vein deposit is composed of wolframite-bearing quartz veins with minor cassiterite, chalcopyrite, pyrite, and lithium-bearing muscovite and sericite. Several wolframite rims show replacement textures, which are assumed to form by iron replacement with manganese postdating the wolframite precipitation. Lithium isotope ratios (δ7Li) of Li-bearing muscovite from the Takatori veins range from −3.1‰ to −2.1‰, and such Li-bearing muscovites are proven to occur at the early stage of mineralization. Fine-grained sericite with lower Li content shows relatively higher δ7Li values, and might have precipitated after the main ore forming event. The maximum oxygen isotope equilibrium temperature of quartz–muscovite pairs is 460 °C, and it is inferred that the fluids might be in equilibrium with ilmenite series granitic rocks. Oxygen isotope ratios (δ18O) of the Takatori ore-forming fluid range from +10‰ to +8‰. The δ18O values of the fluid decreased with decreasing temperature probably because the fluid was mixed with surrounding pore water and meteoric water. The formation pressure for the Takatori deposit is calculated to be 160 MPa on the basis of the difference between the pressure-independent oxygen isotope equilibrium temperature and pressure-dependent homogenization fluid inclusions temperature. The ore-formation depth is calculated to be around 6 km. These lines of evidence suggest that a granitic magma beneath the deposit played a crucial role in the Takatori deposit formation.

Origin and evolution of ore-forming fluids in a tungsten mineralization system, Middle Jiangnan orogenic belt, South China: Constraints from in-situ LA-ICP-MS analyses of scheelite

The Middle Jiangnan orogenic belt is a very important tungsten (W) polymetallic belt in China. There are many types of W deposits in the belt, including veinlet-disseminated and stratabound deposits, which have different origins. The veinlet-disseminated Dahutang W deposit has undergone extensive alteration, such as biotitization (potassic alteration), and greisenization. Scheelite in veinlet-disseminated W mineralization displays a zoned texture indicating at least two generations. The early generation (D1) from the Dahutang W deposit exhibits magmatic hydrothermal characteristics with comparatively high Nb, Ta, and Mo concentrations, but a low Sr concentration (44 to 95 ppm). In contrast, the scheelite samples from the Xi’an W deposit has relatively low Nb, Ta, and Mo concentrations, but a high Sr concentration (582 to 861 ppm), mainly originating from a metamorphic fluid that mixed with meteoric water. The composition of the late generation of scheelite (D2) samples from the Dahutang deposit are intermediate between the composition of scheelite (D1) and scheelite of the Xi’an depsoit. The mineral chemistry of the scheelite samples indicate that the ore-forming fluids of the Dahutang deposit were dominated by magmatic hydrothermal fluids during the early stage, and that meteoric water was added during fluid evolution. The rare earth elements (REEs) in the scheelite samples, especially the variation of the δEu (EuN/((SmN × GdN)0.5)) values, record the change in oxygen fugacity. The ore-forming fluids in the early stage of the Dahutang deposit were reduced becoming oxidized during the precipitation of the D2 scheelite, whereas the ore-forming fluids of the Xi’an deposit were oxidized. An increased oxygen fugacity of the ore-forming fluids of the Dahutang deposit restricted the precipitation of wolframite and promoted the formation of scheelite. Extensive alteration resulted in the decomposition of plagioclase, thus releasing Ca and Sr for the crystallization of scheelite at the Dahutang tungsten deposit.

Fluid inclusion and isotopic (C, H, O, S and Pb) constraints on the origin of late Mesozoic vein-type W mineralization in northern Guangdong, South China

Northern Guangdong of South China occurs many large tungsten deposits, including Shirenzhang, Meiziwo and Yaoling quartz-vein type wolframite deposits. In this study, we carried out a detailed study on fluid inclusions and C-H-O-S-Pb isotopic analyses of mineral separates for these three deposits, in order to resolve the origin and evolution of ore-forming fluids and the ore deposition mechanism. The ore veins in these deposits present a similar mineral paragenesis that could be divided into three stages: (I) pre-ore stage, (II) syn-ore stage, and (III) post-ore stage. The pre-ore stage is the magmatic-hydrothermal transition stage, which is marked by fluid exsolution from the highly fractionated granites, accompanied with potassic alteration and greisenization. The syn-ore stage can be further divided into two stages: silicate-oxide stage (stage II-1) that is characterized by significant tin-tungsten mineral deposition, and sulfide stage (stage II-2) that is characterized by abundant sulfide minerals deposition. The post-ore stage is dominated by quartz and fluorite. The three deposits show similar temperature and salinity variations for syn-ore and post-ore stages. In the Shirenzhang deposit, the fluid temperature and salinity range from 239 to 301 °C and 1.4 to 8.7 wt% NaCl equiv in stage II-1, from 206 to 256 °C and 1.4 to 7.0 wt% NaCl equiv in stage II-2, and from 186 to 236 °C and 1.4 to 8.6 wt% NaCl equiv in stage III. In the Meiziwo deposit, the fluid temperature and salinity range from 242 to 310 °C and 1.1 to 8.6 wt% NaCl equiv in stage II-1, from 196 to 252 °C and 1.4 to 8.1 wt% NaCl equiv in stage II-2, and from 188 to 234 °C and 1.2 to 7.3 wt% NaCl equiv in stage III. In the Yaoling deposit, the fluid temperature and salinity range from 230 to 304 °C and 1.2 to 9.0 wt% NaCl equiv in stage II-1, from 203 to 258 °C and 1.4 to 6.5 wt% NaCl equiv in stage II-2, and from 184 to 231 °C and 1.6 to 8.3 wt% NaCl equiv in stage III. The ore-forming fluids in the three deposits belong to a medium temperature, low-salinity H2O-NaCl system, with trace amounts of volatile components including CO2, CH4 and N2. The C-H-O isotope data (δ13CCO2 = −18.9 to −6.7‰; δ18Owater = +1.1 to +6.3‰; δDH2O = −78 to −55‰) indicate that the ore-forming fluids were mainly magmatic water, which might be modified by fluid-rock interaction and mixing with meteoric water. Sulfur (δ34S = −7.0 to +0.3‰) and Pb isotope data (206Pb/204Pb = 18.531–18.693, 207Pb/204Pb = 15.728–15.753, 208Pb/204Pb = 38.902–39.081) suggest that the ore metal and sulfur are of magmatic origin. The involvement of both organic matter in metasedimentary rocks during fluid-rock interaction and oxidized meteoric water may have been responsible for the negative δ34S and δ13C values. Fluid boiling, fluid-rock interaction and minor input of meteoric water might have been effective factors for the precipitation of wolframite, cassiterite and scheelite. The sulfide precipitation may have resulted from cooling and dilution of magmatic fluids by mixing with meteoric water.

Metal source and wolframite precipitation process at the Xihuashan tungsten deposit, South China: Insights from mineralogy, fluid inclusion and stable isotope

The Xihuashan tungsten deposit, hosted in the late Jurassic granitic pluton in the Nanling Range of South China, has a total resource of about 81,300 tonnes of WO3 with an average ore grade of 1.08% WO3. Wolframite is the dominant ore mineral and intergrown with quartz in the main mineralization stage. Ore-forming fluids trapped in wolframite have δD and δ18O values from −82‰ to −64‰ and 7.4‰ to 8.8‰, respectively. Those in quartz have similar δD (−72‰ to −58‰) and δ18O (6.8‰ to 8.0‰) values, indicative of a magmatic fluids simultaneously trapped by quartz and wolframite. LA-ICP-MS analyses for individual fluid inclusion show that this mineralizing fluid contains measurable Li, Rb, Cs, K, Na, Ti, Cu, Zn, As and W (1–125 ppm with average of 19 ppm) while depleted in Fe and Mn. The wolframite from the Xihuashan tungsten deposit contains high FeO (10.9–17.7 wt%) and MnO (5.9–12.7 wt%) contents with Fe/(Fe + Mn) atomic ratio of 0.46 to 0.75, thus requires the availability of external Fe and Mn. We detect that the Fe and Mn contents in mica from the greisen are remarkably lower than primary mica from granite. Some magmatic micas were observed in greisen and were subjected to hydrothermal alteration. Compared to the core, the rim of these micas depleted in Fe, Mn, F, and Na. The siderite and pyrophanite are formed along cleavage planes of altered magmatic mica that are evidence to be due to Fe and Mn release during granite alteration. Thus, we demonstrate quantitatively that magmatic fluids at Xihuashan provide W in solution, whereas the hosted granite alteration contributes Fe and Mn to precipitate wolframite. It is also supported by wolframites have trace and rare earth elements characteristics similar to those of granite and some characteristics similar to the greisen. Therefore, the ore-forming fluids has components derived from the last highly evolved residual granitic melt and components acquired by releasing through the hosted granite alteration. Fluid-rock interaction exert a principle control on wolframite precipitation. Based on mineralogy, fluid inclusion and stable isotope, we proposed three-stage process to illustrate the genetic link between tungsten mineralization and granite.