The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Holly J Stein - One of the best experts on this subject based on the ideXlab platform.
-
molybdenum isotope variations in Molybdenite vapor transport and rayleigh fractionation of mo
Geology, 2007Co-Authors: Judith L Hannah, Michael E. Wieser, J.r. De Laeter, Holly J Stein, M D VarnerAbstract:Molybdenum isotopes in 20 Molybdenite samples, dated by the Re-Os method and representing a range of geologic settings, show mass-dependent fractionation spanning 0.63‰ per atomic mass unit (amu). Previous Mo isotope data for Molybdenite reveal variations in fractionation of <0.5‰/amu. Interpretation of these data is hampered, however, by limited sample numbers in each study, lack of a common standard for interlaboratory comparison, and limited range of geologic settings. Here we show that Mo isotope compositions of Molybdenites do not correlate with crystallization temperature, age, geographic distribution, or geologic conditions. Rather, Rayleigh distillation may explain variations of as much as 0.34‰/amu in a single Molybdenite occurrence, exceeding the proposed variability in average continental crust. Vapor transport and rapid precipitation of Mo in propagating fractures may account for isotope fractionation of Mo (and perhaps other metals) at very small scales. If so, the average isotopic composition of Mo at each Molybdenite occurrence may be representative of bulk crust. Our results suggest that the isotopic composition of Mo delivered to the oceans is uniform geographically and through geologic time.
-
Variscan ore formation and metamorphism at the Felbertal scheelite deposit (Austria): constraining tungsten mineralisation from Re–Os dating of Molybdenite
Contributions to Mineralogy and Petrology, 2006Co-Authors: Johann G. Raith, Holly J SteinAbstract:The Felbertal scheelite deposit in the Eastern Alps has been regarded as the type locality for stratabound scheelite deposits. It is hosted by a Cambro-Ordovician metavolcanic arc sequence with minor Variscan granitoids (∼ 340 Ma) in the central Tauern Window. Re–Os model ages for Molybdenite from the Felbertal tungsten deposit range between ∼ 358 and ∼ 336 Ma and record several pulses of magmatic-hydrothermal-metamorphic Molybdenite formation. Molybdenite ages from the K2 orebody, a scheelite-rich quartz mylonite in the Western ore field, indicate that both mineralisation and mylonite are Variscan in age and suggest that the shear zone was active for ∼ 20 million years. Early stage tungsten mineralisation ( Scheelite 1 ) in quartzitic ores in the Eastern ore field, which is free of Molybdenite, yielded very low to near blank levels of Re and Os and thus could not be dated. However, Molybdenite from scheelite–quartz stringers, previously interpreted as a feeder stockwork to quartzitic scheelite ore of presumed Cambrian age, yielded Variscan Re–Os ages of ∼ 342 and ∼ 337 Ma. Dating of Molybdenite contained in scheelite ores thus far provides no indication of a Cambrian component to the tungsten mineralisation. Our data are consistent with a model of either granite intrusion-related ore formation and coeval metamorphic overprint during the Early Carboniferous or, alternatively, Molybdenite formation may be exclusively attributed to Variscan metamorphism (see Stein 2006 ).
-
low rhenium Molybdenite by metamorphism in northern sweden recognition genesis and global implications
Lithos, 2006Co-Authors: Holly J SteinAbstract:Abstract Re–Os dating of Molybdenite is an accurate means to date intrusions and intrusion-related ore deposits using the model age or isochron approach. But, Molybdenite has a new niche in the greenschist- to granulite-facies metamorphic environment. Re–Os ages for metamorphic Molybdenite may be used to construct regional metamorphic histories. Age significance and accuracy are established by analyzing multiple Molybdenite separates extracted from single, petrographically-characterized Molybdenite occurrences. In this study, twelve geologically distinct Molybdenite-bearing samples from two small Mo districts in northern Sweden trace a 150 m.y. Paleoproterozoic Svecofennian metamorphic history from ∼1900 to 1750 Ma. These data reveal a little-known, widespread and protracted, Late Svecofennian anatexis in northern Sweden. The Kataberget Mo–(Cu, F) deposit is located in the Moskosel granite batholith north of the economically-renown Skellefte district. Four different Molybdenite samples from outcrop at Kataberget indicate an intrusion age of 1895 ± 6 Ma with the formation of later pegmatite–aplite at 1875 ± 6 Ma. The Allebuoda (Bjorntjarn) and Munka Mo–(W) deposits in the Rappen district are represented by three outcrop and five drill core samples of Molybdenite-bearing aplite–pegmatite–granite. These two deposits were previously described as intrusion-related Climax-type Mo mineralization. Re–Os ages for Molybdenites from these deposits range from 1865 to 1750 Ma and, significantly, Re concentrations are markedly low, extending to the sub-ppm level. Age agreement within the deposits is conspicuously lacking, whereas, with one exception, age agreement within any single sample (geologic occurrence), as established by analysis of additional Molybdenite separates, is very good. These data, together with fundamental geologic observations discussed in this paper, suggest that Mo–(W) mineralization in northern Sweden is not intrusion-related, but the local product of episodic melting of Archean–Paleoproterozoic supracrustal gneisses related to the Svecofennian orogeny. Petrographic traverses across the boundary between widespread, foliation-parallel units of aplitic to pegmatitic pink granite and hosting biotite gneiss directly capture the process of ore formation. Dehydration breakdown of zircon-rich biotite aligned with the foliation in the gneiss is accompanied by formation of new pristine, post-deformational biotite plus sulfides, oxides, hydrothermal zircon and fluorite, all associated with microcline-dominant leucosomes. This process has profound implication for the traditional leucogranite, intrusion-related genesis attributed to the broad classification of Mo–W–Sn–base and precious metal mineralization (e.g., South Mountain Batholith, Nova Scotia; Okiep, Namaqualand, South Africa; Mactung, Yukon; Pogo–Liese, Tintina, Alaska; Carajas and Goias–Rio Tocantins, Brazil; New England Batholith, NSW, Australia; Bergslagen, Sweden; Nevoria, Western Australia; Alpeinerscharte, Austria; Erzgebirge, Germany; Sardinia–Corsica Batholith). In addition to biotite, metallogenic contributions (e.g., Mo, W, Sn, U, Bi, Cu, Pb, Zn, Fe, Ni, Co, Au, Ag, Te, As, Sb, REE) in various combinations may also be controlled by breakdown of amphibole. In effect, the trace element composition of dehydrating or recrystallizing components in a gneissic rock essentially defines the local and district metallogenic suite. In the absence of focusing structures (e.g., shear zones, sheeted vein development), this process will generally form small and disconnected subeconomic deposits with erratic and unpredictable grades. Low Re content in associated Molybdenite is a key indicator for a subeconomic origin by local melting of biotite gneiss (Mo–W) or muscovite schist (Sn–W).
-
subgrain scale decoupling of re and 187os and assessment of laser ablation icp ms spot dating in Molybdenite
Geochimica et Cosmochimica Acta, 2003Co-Authors: Holly J Stein, Judith L Hannah, Anders Schersten, Richard J MarkeyAbstract:Abstract Reproducibility of Re-Os Molybdenite ages depends on sample size and homogeneity, suggesting that Re and Os are decoupled within individual Molybdenite crystals and do not remain spatially linked over time. In order to investigate the Re-Os systematics of Molybdenite at the subgrain (micron) scale, we report LA-ICP-MS Re-Os ages for an Archean Molybdenite crystal from Aittojarvi, Finland, analyzed in situ in a white aplite matrix. A related Aittojarvi Molybdenite (A996D), in the form of a very fine-grained mineral separate, is used as one of our in-house NTIMS standards, and thus its age of 2760 ± 9 Ma is well established. Measurements of ( 187 Re + 187 Os)/ 185 Re on micron scale spots along 200 μm traverses across the crystal yield a wide range of ages demonstrating that, in this case, microsampling of Molybdenite does not produce geologically meaningful ages. Experimentation with mineral separations and sample size over a 7-yr period predicted that this would be the outcome. We suggest that 187 Os is more likely to be the mobile species, based on its charge and ionic radius, and that 187 Os becomes decoupled from parent 187 Re with time on the micron and larger scale. Incompatible charge and ionic radius for Os ions formed during reduction of Molybdenite-forming fluids may explain the widely observed absence of common (initial) Os in Molybdenite. Geologically accurate ages for Molybdenite can only be obtained for fully homogenized crystals (or crystal aggregates) so that any post-crystallization 187 Re- 187 Os decoupling is overcome. A growing number of geologically accurate ID-NTIMS 187 Re- 187 Os ages for homogenized Molybdenite suggest that postcrystallization mobility of radiogenic 187 Os must be limited to within the Molybdenite mineral phase. We suggest that radiogenic 187 Os may be stored in micron scale dislocations, kink bands, and delamination cracks produced by deformation, and that the unusual structure and deformation response of Molybdenite results in an increased chemical stability in this mineral. Migration of 187 Os into adjacent silicate phases is highly unlikely, but other contacting sulfides may take in Os. In an example from a Proterozoic skarn deposit at Pitkaranta (western Russia), we demonstrate minor loss of radiogenic 187 Os from Molybdenite and a corresponding gain in adjacent chalcopyrite such that the Molybdenite age is not perceptibly disturbed, whereas the resulting chalcopyrite ages are impossibly old. Therefore, it is unadvisable to perform Re-Os analytical work on any sulfide in contact or intimate association with Molybdenite. In addition to large errors in the age, if the isochron method is employed, initial 187 Os/ 188 Os ratios could be erroneously high, leading to seriously errant genetic interpretations.
-
The remarkable Re-Os chronometer in Molybdenite : how and why it works
Terra Nova, 2001Co-Authors: Holly J Stein, Judith L Hannah, R J Markey, John W Morgan, Anders ScherstenAbstract:The Re–Os (rhenium–osmium) chronometer applied to Molybdenite (MoS2) is now demonstrated to be remarkably robust, surviving intense deformation and high-grade thermal metamorphism. Successful dating of Molybdenite is dependent on proper preparation of the mineral separate and analysis of a critical quantity of Molybdenite, unique to each sample, such that recognized spatial decoupling of 187Re parent and 187Os daughter within individual Molybdenite crystals is overcome. Highly precise, accurate and reproducible age results are derived through isotope dilution and negative thermal ion mass spectrometry (ID-NTIMS). Spatial decoupling of parent–daughter precludes use of the laser ablation ICP-MS microanalytical technique for Re–Os dating of Molybdenite. The use of a reference or control sample is necessary to establish laboratory credibility and for interlaboratory comparisons. The Rb–Sr, K–Ar and 40Ar/39Ar chronometers are susceptible to chemical and thermal disturbance, particularly in terranes that have experienced subsequent episodes of hydrothermal/magmatic activity, and therefore should not be used as a basis for establishing accuracy in Re–Os dating of Molybdenite, as has been done in the past. Re–Os ages for Molybdenite are almost always in agreement with observed geological relationships and, when available, with zircon and titanite U–Pb ages. For terranes experiencing multiple episodes of metamorphism and deformation, Molybdenite is not complicated by overgrowths as is common for some minerals used in U–Pb dating (e.g. zircon, monazite, xenotime), nor are Re and Os mobilized beyond the margins of individual crystals during solid-state recrystallization. Moreover, inheritance of older Molybdenite cores, incorporation of common Os, and radiogenic Os loss are exceedingly rare, whereas inheritance, common Pb and Pb loss are common complications in U–Pb dating techniques. Therefore, Molybdenite ages may serve as point-in-time markers for age comparisons.
Hongbo Zeng - One of the best experts on this subject based on the ideXlab platform.
-
Separation of talc and Molybdenite: challenges and opportunities
Minerals Engineering, 2019Co-Authors: Duowei Yuan, Kenneth C. Cadien, Qi Liu, Hongbo ZengAbstract:Abstract Talc is one of the most problematic hydrophobic gangue minerals that occur in sulfide ores such as Molybdenite and Pt-bearing nickel sulfide ores. Owing to its strong natural hydrophobicity, talc can easily float into the sulfide mineral concentrates, which not only lowers concentrate grade but also adversely affects subsequent smelting. Over the past several decades, many studies have been carried out to separate the hydrophobic gangue mineral talc from Molybdenite by froth flotation and other techniques. However, the selective and efficient removal of talc from Molybdenite concentrates remains a challenging issue, and the underlying mechanisms of depression are poorly understood. To better understand the flotation and depression behaviors of talc and Molybdenite, a fundamental understanding of the surface properties, such as surface charge, wettability and their alteration, is required. Recently, significant progress in understanding the surface chemistry of talc and Molybdenite has been made and novel depressants have been developed. In the current review, these recent advances are systematically discussed, together with a discussion of conventional practices and reagent systems for the Molybdenite-talc separation. The remaining challenges and future directions for the Molybdenite-talc separation are also presented.
-
Adsorption characteristics and mechanisms of O-Carboxymethyl chitosan on chalcopyrite and Molybdenite.
Journal of colloid and interface science, 2019Co-Authors: Duowei Yuan, Kenneth C. Cadien, Qi Liu, Hongbo ZengAbstract:O-Carboxymethyl chitosan (O-CMC), a nontoxic and biodegradable derivative of the natural polysaccharide-chitosan, was recently found to be a viable alternative for the toxic depressants used in the flotation separation of chalcopyrite and Molybdenite. In this work, the adsorption characteristics of O-CMC on Molybdenite/chalcopyrite surfaces and the associated interaction mechanisms were investigated by electrokinetic study, infrared spectroscopy, Atomic force microscopy (AFM) imaging, X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The experimental results demonstrated that O-CMC adsorbed on both mineral surfaces. However, the interactions between O-CMC and chalcopyrite are mostly weak physical interactions such as electrostatic interaction, and most of the adsorbed O-CMC molecules can be removed mechanically (e.g., washing) or displaced by xanthate. In comparison, the adsorption of O-CMC on Molybdenite is dictated by hydrophobic interaction and electrostatic interaction, and is barely affected by rinsing or xanthate addition. As a result, the strong adsorption of O-CMC on Molybdenite over the chalcopyrite lead to the depression of Molybdenite and selective separation of two minerals in flotation. In addition, infrared spectroscopy and XPS revealed that no strong chemical interactions were involved during the adsorption O-CMC on Molybdenite and chalcopyrite surfaces.
-
Selective flotation separation of Molybdenite and talc by humic substances
Minerals Engineering, 2018Co-Authors: Duowei Yuan, Qi Liu, Lei Xie, Xingwei Shi, Guofan Zhang, Hao Zhang, Hongbo ZengAbstract:Abstract Humic acid (HA) has been studied as a potential selective depressant for Molybdenite in the flotation separation of Molybdenite and talc in this paper. In the single mineral flotation tests, HA has shown good depression ability to Molybdenite over the entire pH range tested from pH 3–11, while the floatability of talc was only affected by HA under strong acidic condition (pH 3). In the mixed minerals flotation, HA can effectively depress the flotation of Molybdenite while not affecting the flotation of talc under strong alkaline condition (pH 11). Contact angle measurements have proved that the hydrophobicity of both talc and Molybdenite decreases after treatment by HA, however, the contact angles of treated talc are still higher than Molybdenite. Equilibrium adsorption studies indicate that HA has a much higher adsorption density on Molybdenite than on talc. The preferential adsorption of HA on Molybdenite was further confirmed by diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) and atomic force microscopy (AFM) imaging. All of the experimental results suggest that humic acids can be employed as a selective depressant for Molybdenite during the flotation separation of Molybdenite and talc under alkaline conditions, and the higher adsorption density of HA on Molybdenite over talc is the primary reason for the selective separation.
Duowei Yuan - One of the best experts on this subject based on the ideXlab platform.
-
Separation of talc and Molybdenite: challenges and opportunities
Minerals Engineering, 2019Co-Authors: Duowei Yuan, Kenneth C. Cadien, Qi Liu, Hongbo ZengAbstract:Abstract Talc is one of the most problematic hydrophobic gangue minerals that occur in sulfide ores such as Molybdenite and Pt-bearing nickel sulfide ores. Owing to its strong natural hydrophobicity, talc can easily float into the sulfide mineral concentrates, which not only lowers concentrate grade but also adversely affects subsequent smelting. Over the past several decades, many studies have been carried out to separate the hydrophobic gangue mineral talc from Molybdenite by froth flotation and other techniques. However, the selective and efficient removal of talc from Molybdenite concentrates remains a challenging issue, and the underlying mechanisms of depression are poorly understood. To better understand the flotation and depression behaviors of talc and Molybdenite, a fundamental understanding of the surface properties, such as surface charge, wettability and their alteration, is required. Recently, significant progress in understanding the surface chemistry of talc and Molybdenite has been made and novel depressants have been developed. In the current review, these recent advances are systematically discussed, together with a discussion of conventional practices and reagent systems for the Molybdenite-talc separation. The remaining challenges and future directions for the Molybdenite-talc separation are also presented.
-
Adsorption characteristics and mechanisms of O-Carboxymethyl chitosan on chalcopyrite and Molybdenite.
Journal of colloid and interface science, 2019Co-Authors: Duowei Yuan, Kenneth C. Cadien, Qi Liu, Hongbo ZengAbstract:O-Carboxymethyl chitosan (O-CMC), a nontoxic and biodegradable derivative of the natural polysaccharide-chitosan, was recently found to be a viable alternative for the toxic depressants used in the flotation separation of chalcopyrite and Molybdenite. In this work, the adsorption characteristics of O-CMC on Molybdenite/chalcopyrite surfaces and the associated interaction mechanisms were investigated by electrokinetic study, infrared spectroscopy, Atomic force microscopy (AFM) imaging, X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The experimental results demonstrated that O-CMC adsorbed on both mineral surfaces. However, the interactions between O-CMC and chalcopyrite are mostly weak physical interactions such as electrostatic interaction, and most of the adsorbed O-CMC molecules can be removed mechanically (e.g., washing) or displaced by xanthate. In comparison, the adsorption of O-CMC on Molybdenite is dictated by hydrophobic interaction and electrostatic interaction, and is barely affected by rinsing or xanthate addition. As a result, the strong adsorption of O-CMC on Molybdenite over the chalcopyrite lead to the depression of Molybdenite and selective separation of two minerals in flotation. In addition, infrared spectroscopy and XPS revealed that no strong chemical interactions were involved during the adsorption O-CMC on Molybdenite and chalcopyrite surfaces.
-
Selective flotation separation of Molybdenite and talc by humic substances
Minerals Engineering, 2018Co-Authors: Duowei Yuan, Qi Liu, Lei Xie, Xingwei Shi, Guofan Zhang, Hao Zhang, Hongbo ZengAbstract:Abstract Humic acid (HA) has been studied as a potential selective depressant for Molybdenite in the flotation separation of Molybdenite and talc in this paper. In the single mineral flotation tests, HA has shown good depression ability to Molybdenite over the entire pH range tested from pH 3–11, while the floatability of talc was only affected by HA under strong acidic condition (pH 3). In the mixed minerals flotation, HA can effectively depress the flotation of Molybdenite while not affecting the flotation of talc under strong alkaline condition (pH 11). Contact angle measurements have proved that the hydrophobicity of both talc and Molybdenite decreases after treatment by HA, however, the contact angles of treated talc are still higher than Molybdenite. Equilibrium adsorption studies indicate that HA has a much higher adsorption density on Molybdenite than on talc. The preferential adsorption of HA on Molybdenite was further confirmed by diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) and atomic force microscopy (AFM) imaging. All of the experimental results suggest that humic acids can be employed as a selective depressant for Molybdenite during the flotation separation of Molybdenite and talc under alkaline conditions, and the higher adsorption density of HA on Molybdenite over talc is the primary reason for the selective separation.
Andres Ramirez - One of the best experts on this subject based on the ideXlab platform.
-
The Depressing Effect of Kaolinite on Molybdenite Flotation in Seawater
Minerals, 2020Co-Authors: Andres Ramirez, Leopoldo Gutierrez, Dennis Vega-garcia, Lorenzo Reyes-bozoAbstract:Copper-molybdenum grades of important mining deposits have progressively decayed, which is associated with high levels of clay minerals which affect froth flotation. The depressing effect of clay minerals on copper sulfides was previously reported but there are no systematic studies on the effect on Molybdenite flotation in seawater. The objective of this work was to study the effect of kaolinite on Molybdenite flotation in seawater and to evaluate the use of sodium hexametaphosphate (SHMP) as dispersant. The results of this work show that kaolinite depresses Molybdenite flotation which is more significant in seawater at pH > 9. All the experimental data validate the hypothesis that kaolinite covers Molybdenite, reducing its flotation recovery. The depressing effect of kaolinite on Molybdenite flotation in seawater is enhanced by the magnesium and calcium hydroxo complexes at pH > 9, which induce heterocoagulation between kaolinite and Molybdenite, thus reducing recovery. The attachment of the positively charged hydroxo complexes of magnesium and calcium to the Molybdenite and kaolinite surfaces is diminished by SHMP. This reagent increases the repulsive forces between Molybdenite and precipitates and as a result, Molybdenite becomes more hydrophobic and recovery increases.
-
Use of “oily bubbles” and dispersants in flotation of Molybdenite in fresh and seawater
Minerals Engineering, 2020Co-Authors: Andres Ramirez, Leopoldo Gutierrez, Janusz S. LaskowskiAbstract:Abstract Molybdenite - as all inherently hydrophobic minerals – is floated with the use of water-insoluble oily collectors. Such collectors can be used in flotation either after emulsification in water, but can also be brought to the point of particle-to-bubble attachment on the surface of bubbles (as oily-bubbles). In this paper we are testing the effect of oily-bubbles and the dispersants sodium hexametaphosphate (SHMP) and sodium silicate (SS) on the flotation of moleybdenite in seawater in alkaline environment. The results show that Molybdenite recovery increases when kerosene is supplied on the surface of bubbles which was particularly important in the flotation of Molybdenite at pH > 9.5 in seawater. SHMP dispersant had a strong positive effect on the recovery of Molybdenite at pH > 9.5, the pH range known to cause depression of the Molybdenite flotation when pH is raised to depress pyrite and magnesium species precipitate as hydroxo-complexes/hydroxide. The combined effect of the oily bubbles and dispersants allows for the Molybdenite recoveries to reach to similar values to those achieved when using fresh water. The results of induction time measurements indicate that the attachment of bubbles to Molybdenite is significantly improved when the bubbles are coated with a layer of kerosene.
-
Hemicelluloses monosaccharides and their effect on Molybdenite flotation
Powder Technology, 2020Co-Authors: Isaac Castillo, Leopoldo Gutierrez, Vicente A. Hernandez, Enzo Díaz, Andres RamirezAbstract:Abstract The use of biodegradable reagents such as hemicelluloses was shown to improve copper recovery from high clay ores, but, at the same time these reagents also depressed Molybdenite. Hemicelluloses are heteropolysaccharides formed by monosaccharides such as xylose, glucose, arabinose, galactose, and mannose. Since these monosaccharides are the basic compounds of the structure of hemicelluloses, the objective of this work was to study the effect of D-xylose, D-mannose and D-glucose on the flotation behavior of Molybdenite and propose mechanisms to explain the mineral/reagent interactions. The effect of a non-polar collector on Molybdenite flotation in the presence of the tested monosaccharides was also evaluated with the aim of looking for solutions to reduce Molybdenite depression. It was found that all the monosaccharides tested depress Molybdenite flotation. The depressing effects of D-mannose and D-glucose are stronger than that of D-xylose. These results can be explained by the fact that D-glucose and D-mannose molecules have more carbon atoms and hydroxyl groups in their structure than D-xylose, thus more chances to interact with the metallic sites existing on Molybdenite surfaces. The depressing effect of the tested monosaccharides increases with pH which is explained by the increase of the concentration of basic sites on Molybdenite surfaces and by ionization of the hydroxyl groups of monosaccharide molecules. The addition of kerosene reduces the depressing effect of the tested monosaccharides. It can be postulated that when Molybdenite faces are covered by kerosene, those acidic/basic metallic sites that explain the interactions between monosaccharides and Molybdenite disappear and adsorption is attenuated.
Lianhui Dong - One of the best experts on this subject based on the ideXlab platform.
-
u pb zircon re os Molybdenite geochronology and rb sr geochemistry from the xiaobaishitou w mo deposit implications for triassic tectonic setting in eastern tianshan nw china
Ore Geology Reviews, 2017Co-Authors: Xiaohua Deng, Yanjing Chen, M Santosh, Jingbin Wang, Chao Li, Zhen Zheng, Hongjin Chen, Haoshu Tang, Lianhui DongAbstract:Abstract The Xiaobaishitou W (–Mo) deposit is located in the eastern segment of the Central Tianshan, northwestern China. The deposit represents a skarn system distributed in the contact zones of biotite granite and crystalline limestone of the Mesoproterozoic Kawabulag Group. The Xiaobaishitou deposit is characterized by a typical calc-silicate mineralogy dominated by garnet, diopside and wollastonite, with minor epidote, tremolite, actinolite, chlorite, quartz, fluorite and calcite. The prograde and retrograde skarns are characterized by garnet–clinopyroxene–wollastonite and epidote–tremolite–actinolite–chlorite, respectively, intruded and replaced by mineral assemblages of scheelite–cassiterite–magnetite, quartz–sulfides and calcite–quartz–fluorite in younger order. Six Molybdenite samples from the deposit yielded Re − Os isotope model ages ranging from 239.7 ± 3.6 Ma to 251.4 ± 3.6 Ma. The zircon crystals from biotite granite and Mo-mineralized granite yield weighted 206Pb/238U age of 242 ± 1.7 and 240.5 ± 2.1 Ma, respectively. Both the zircon U − Pb and the Molybdenite Re − Os ages obtained in this study fall in a narrow span of 242–240 Ma, which suggest that the Xiaobaishitou W (–Mo) system was formed in the Triassic. The Re contents of the Molybdenites range from 40.33 to 64.67 ppm, suggesting that the ore-forming materials were derived mainly from continental crust together with the involvement of minor mantle components. Combined with the 87Sr/86Sr ratios of tungsten-bearing quartz veins from other studies, which scatter between 0.707153 and 0.709877, demonstrating mixing between two end-member isotopic compositions of crust and mantle. It can be concluded that the Indosinian Xiaobaishitou deposit was formed in a tectonic transition from collisional crust shortening and thickening to post-collisional extension and thinning.