Molybdenite Mineralization Research Articles

Alternative sources of molybdenum for Methanococcus maripaludis and their implication for the evolution of molybdoenzymes

Molybdoenzymes are essential in global nitrogen, carbon, and sulfur cycling. To date, the only known bioavailable source of molybdenum (Mo) is molybdate. However, in the sulfidic and anoxic (euxinic) habitats that predominate in modern subsurface environments and that were pervasive prior to Earth’s widespread oxygenation, Mo occurs as soluble tetrathiomolybdate ion and molybdenite mineral that is not known to be bioavailable. This presents a paradox for how organisms obtain Mo to support molybdoenzymes in these environments. Here, we show that tetrathiomolybdate and molybdenite sustain the high Mo demand of a model anaerobic methanogen, Methanococcus maripaludis, grown via Mo-dependent formate dehydrogenase, formylmethanofuran dehydrogenase, and nitrogenase. Cells grown with tetrathiomolybdate and molybdenite have similar growth kinetics, Mo content, and transcript levels of proteins involved in Mo transport and cofactor biosynthesis when compared to those grown with molybdate, implying similar mechanisms of transport and cofactor biosynthesis. These results help to reconcile the paradox of how Mo is acquired in modern and ancient anaerobes and provide new insight into how molybdoenzymes could have evolved prior to Earth’s oxygenation.

Molybdenite Reference Materials for In SituLA‐ICP‐MS/MS Re‐Os Geochronology

Re‐Os isotope‐dilution geochronology has been widely used to date the timing of molybdenite, pyrite and chalcopyrite formation across a variety of geological settings. However, in situ methods have been impeded by the isobaric interference of 187Re on 187Os. In situ Re‐Os geochronology using LA‐ICP‐MS/MS has been shown to be a useful technique to chemically separate Os from Re, as Os reacts with CH4 to create higher‐mass reaction products, which can then be measured with minimised interference of 187Re. However, application of the method requires matrix‐matched primary reference materials, e.g., age‐homogenous molybdenite amenable to laser ablation. Here, we characterise and present two new molybdenite mineral reference materials for in situ Re‐Os geochronology by LA‐ICP‐MS/MS, verified by ID‐TIMS Re‐Os measurements. We also present case studies from molybdenite samples with varying Re mass fractions and Re‐Os age mapping. The method provides accurate and precise age data, with excellent precision for high Re samples. The benefits of the LA‐ICP‐MS/MS approach include: (1) simple sample preparation, (2) rapid data acquisition, (3) targeting of specific textural domains including growth zones and (4) the ability to simultaneously collect trace elements used to link the timing and conditions of ore‐formation.

A transition from porphyry Mo to vein-style Zn-Pb mineralization: Insights from hydrothermal fluid evolution of the Chalukou deposit, NE China

To reveal the hydrothermal evolution from porphyry Mo to vein-style Zn-Pb mineralization, the Chalukou deposit in NE China with these two typical mineralization overprinted is selected for detailed research. From early to late hydrothermal veins, the quartz cathodoluminescence intensities change from bright to dark and the textures also evolve. The Ti concentrations of quartz in these veins change from high to moderate and then to low values. The fluid inclusion petrography, microthermometry and stable isotope analyses indicate intermediate-density magma-derived fluids (δ18Owater = +4.7 to + 6.2‰, δD = −132 to −136‰) exsolved at high temperatures (560° to 600 °C) with low to moderate salinity (2.4 to 8.0 wt% NaCl equiv) containing minor CO2 (<5.7 mol %). Early minor molybdenite occurred under lithostatic conditions at high temperatures (540° to 580 °C) during fluids pH change and early magnetite precipitation. Later main molybdenite precipitation at moderate temperatures (350° to 430 °C), result from fluid cooling and involving of meteoric water under the transition from lithostatic to hydrostatic conditions. The precipitation of pyrite in transitional veins at moderate temperatures (330° to 420 °C), and the late sphalerite-galena from a lower-temperature fluid (180° to 300 °C) is consistent with the cooling of magmatic fluid, and gradually dilution with meteoric water under hydrostatic conditions. It is deduced the transition from porphyry Mo to vein-style Zn-Pb mineralization is likely driven by progressive decrease in temperature of the magmatic fluids and the increasing influx of meteoric water.

Genesis of the Taoguanping molybdenum deposit in the Northern Qinling Belt, Central China: Constraints from geology, fluid inclusions, and H–O–S isotopes

The Taoguanping molybdenum deposit is located in the west of the Mangling pluton in the Northern Qinling Belt, but its fluid characteristics and ore-forming process are unclear, hindering the understanding of its ore genesis and genetic model. The paragenetic sequence of the Taoguanping molybdenum deposit can be divided into: quartz–K-feldspar–sulfide stage (Stage I), quartz–polymetallic sulfide stage (Stage II), and quartz–calcite stage (Stage III). Stage I is characterized by disseminated molybdenite mineralization associated with siliceous and K-feldspar alteration in the medium- to fine-grained monzogranite, representing the early mineralization. Stage II is the main mineralization featured by coarse-grained quartz–sulfide veins, e.g., quartz–molybdenite and quartz–biotite–molybdenite ± pyrite ± chalcopyrite veins, crosscutting monzogranite and host rocks. Stage III is late hydrothermal veins to crosscut former minerals. Detailed fluid inclusion study shows that temperature and salinity of fluids decreased from Stage I (peaks at ca. 320–380 °C and 3.7–13.6 wt% NaCl eqv.), through Stage II (peaks at ca. 260–300 °C and 1.2–11.8 wt% NaCl eqv.) to Stage III (peaks at ca. 180–220 °C and 0.4–8.9 wt% NaCl eqv.), accompanied by fluid mixing and boiling. The H–O isotopes of quartz (δDfluid = –72‰ to –53‰ and δ18Ofluid = 9.1–10.9‰) suggest Stage II fluids are magmatic–hydrothermal origin mixed with minor meteoric water. The in-situ sulfur isotope of pyrite (–33.4‰ to –13.4‰ and 0‰ to 7.8‰) indicates Stage II fluids being mainly magmatic–hydrothermal origin, with participation of strata materials inferred by presence of Stage II euhedral to anhedral pyrite with inclusion-rich domains and CH4 in Stage II fluid inclusions during fluid–rock interaction. In combination of this study and regional tectonic setting, we propose that the Taoguanping molybdenum deposit underwent porphyry and hydrothermal vein-type mineralization, contributed by medium- and fine-grained monzogranite and possible granite porphyry, respectively, which should be ascribed to a porphyry mineralization system and formed in a post-collisional setting during the Late Mesozoic.

Evaluation and mechanism of ultrasound-assisted electrochemical desulfurization using citric acid as the electrolyte solution

ABSTRACT Achieving the clean utilization of coal is the priority of the coal industries. This paper proposed an efficient electrochemical technology for coal desulfurization before combustion. It was explored that citric acid can chemically provide enough acidic conditions for desulfurization reactions, and the ultrasonic-enhanced treatment physically helps to remove sulfur from coal due to its cavitation effect and mechanical effect. So the experiments of ultrasound-assisted electrochemical desulfurization using citric acid as the electrolyte solution were conducted. They combined physical and chemical methods to effectively remove sulfur from coal. The optimal operating parameters of the desulfurization effect were achieved by qualitative and quantitative analysis of coal samples(coal slurry concentration of 66 g/L, electrolysis time of 8 h, electrolyte concentration of 1.5 mol/L, electrolysis voltage of 4 V, electrolysis temperature of 30°C, ultrasonic strengthening time of 1 h and ultrasonic intensity of 320 W.). The total sulfur removal efficiency reached 45.09%. The electrolytic desulfurization experiments removed samples’ sulfur contents, ash contents, and water. The crystal structures of gypsum, white iron ore, zinc sulfide, and the molybdenite mineral composition were also destroyed for purification. Gaussian simulations showed that C-S bonds and S-S bonds contained in non-thiophene organic sulfur are easier to remove, and S-S bonds are more likely to break than C-S bonds. This study realized the promotion of desulfurization with the ultrasonic wave and citric acid solution. It provides a new idea of synergistic desulfurization and is beneficial to reduce atmospheric sulfur pollution.

The Peña do Seo W-Sn deposit, NW Iberia: Petrology, fluid inclusions and O-H-S isotopes

The Peña do Seo W-Sn ore deposit in NW Iberia consists mainly of quartz veins hosted in schists. Vein mineralogy comprises wolframite, cassiterite and minor molybdenite. Peraluminous S-type granites and minor metaluminous granitoid breccias crop out in the same location. Whole rock geochemistry, mineral characterization, fluid inclusions and stable isotope geochemistry have been combined to infer hydrothermal mineralization conditions. A pre-ore stage (0) involving the alteration of host rocks, three stages of mineralization (I, II and III), and a supergene stage (IV) have been identified. Stage I (oxide-halide-sulfide stage) consisted of a cassiterite-pyrite-fluorite mineralization in granitoid breccias. Stage II (main oxide stage) involved wolframite-rich selvages and wolframite-cassiterite-(molybdenite) quartz veins. Stage III (main sulfide stage) consisted of a sulfide mineralization in quartz veins comprising pyrite and minor arsenopyrite and chalcopyrite. Three types of fluid inclusions were found in vein quartz: (1) aqueous two-phase inclusions, with homogenization temperatures (Th) between 445 °C and 280 °C and moderate salinities (9-14 wt.% NaCl eq.), (2) aqueous-carbonic three-phase fluid inclusions, with Th from 340 °C to 260 °C and low salinities (2-7 wt.% NaCl eq.), and (3) aqueous two-phase fluid inclusions, with Th from 270°C to 155 °C and low salinities (0-6 wt.% NaCl eq.). δ18O values in quartz from mineralized veins range from +11.2‰ to +13.4‰, and between +15.0‰ and +15.4% in quartz from mineralized granitoid breccias. δ34S values in sulfides (pyrite, arsenopyrite and chalcopyrite) range between +13.0 ‰ and +37.1 ‰, thus suggesting a marine source of sulfate and possible equilibration with host-rock sulfides. δD values in muscovite and chlorite from quartz veins range between -105.7 ‰ and -71.5 ‰ and between -69.4 ‰ and -67.1 ‰, respectively, indicating a transition from magmatic to magmatic-metamorphic conditions. An aqueous (H2O–NaCl) magmatic-hydrothermal fluid led to the W-Sn mineralization, as deduced from the studied fluid inclusions and isotopic signatures. High W and Sn contents in the peraluminous granites indicate that the W-Sn mineralization in Peña do Seo could partially be related to the granites and granitoid breccias. Whereas the Sn (± W) likely derived from hydrothermal fluids exsolving from the crystallizing magmas, host quartz schists would have supplied other elements required for wolframite deposition such as Fe and Mn. Sulfide mineralization in stage III was probably driven by fluid dilution.

High-Precision Geochronology of the Xiaojiayingzi Mo Skarn Deposit: Implications for Prolonged and Episodic Hydrothermal Pulses

Abstract The timescales and duration of ore-forming processes in skarn systems are not well constrained. To better understand this, we present high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon and isotope dilution-negative-thermal ionization mass spectrometry (ID-N-TIMS) Re-Os molybdenite geochronology of the Xiaojiayingzi Mo skarn deposit (0.13 Mt Mo at 0.22 wt %), northeastern China. The Xiaojiayingzi deposit is related to an intrusive complex composed of gabbroic diorite, monzodiorite, and granite porphyry. Molybdenite mineralization occurred in two ore blocks, Xiaojiayingzi (0.11 Mt Mo) and Kangzhangzi (0.02 Mt Mo). In the Kangzhangzi ore block, Mo mineralization is concentrated in skarn adjacent to a deep-seated granite porphyry, with minor disseminated and quartz veinlet mineralization within the granite porphyry. In contrast, economic Mo mineralization in the Xiaojiayingzi ore block is concentrated in skarns located between the contact of steeply dipping monzodiorite and the Mesoproterozoic Wumishan Formation, with minor Mo mineralization found in quartz and endoskarn veins hosted in the monzodiorite. Skarn mineralization in both ore blocks converges downward into the mineralized granite porphyry. In the Kangzhangzi ore block, skarn is zoned from deep proximal dark red-brown garnet to shallow distal dark-green pyroxene. In the Xiaojiayingzi ore block, proximal skarn is garnet rich, whereas pyroxene increases away from the monzodiorite-Wumishan Formation contact. In addition, pyroxene becomes more Fe and Mn rich with distance from the intrusions; Pb, Zn, and Ag increase toward the top of the system; and Mo and Fe increase with depth. High-precision CA-ID-TIMS U-Pb zircon geochronology indicates the gabbroic diorite crystallized at 165.359 ± 0.028/0.052/0.18 Ma (uncertainties presented as analytical/+ tracer/+ decay constant uncertainties), with subsequent crystallization of the monzodiorite and granite porphyry at 165.361 ± 0.040/0.059/0.19 and 165.099 ± 0.026/0.051/0.18 Ma, respectively. High-precision ID-N-TIMS Re-Os molybdenite geochronology indicates molybdenite mineralization at Xiaojiayingzi occurred in at least three discrete magmatic-hydrothermal pulses (nominally between 165.48 ± 0.09–165.03 ± 0.13, 163.73 ± 0.09, and 163.11 ± 0.11 Ma). The first episode of molybdenite mineralization formed in exoskarns, endoskarns, and quartz veins and had a minimum duration of 450 ± 40 k.y., between 165.48 ± 0.09/0.68/0.85 and 165.03 ± 0.13/0.67/0.85 Ma. It is likely that skarn ore represents a composite series of mineralization events, more than the three events capable of identification within analytical uncertainty of these high-precision data. Finally, Re-Os dating of quartz Mo veins cutting the monzodiorite and granite porphyry indicates that some mineralization postdated the observed intrusions, between 163.73 ± 0.09/0.70/0.86 and 163.11 ± 0.11/0.70/0.86 Ma, interpreted to be the result of deeper, unobserved intrusions. Collectively, these ages indicate that protracted, pulsed Mo mineralization at the Xiaojiayingzi deposit occurred over a period of at least 2.4 m.y. These data suggest that individual magmatic and/or skarn garnet ages may significantly underestimate the full duration of mineralization. In addition, this study highlights that systematically identifying skarn deposits associated with multiphase intrusive systems may reveal targets for future exploration, as it may point to previously undiscovered mineral resources.

Geochronology and Tectonic Implications of the Nianzigou Granites and Associated Mo Deposit, Inner Mongolia

Multiple stages of igneous rocks occur in the recently discovered Nianzigou Mo deposit in Chifeng, Inner Mongolia, which can provide insights into the late Mesozoic geodynamic evolution of the southern Da Hinggan Range. The mineralization age is similar to the age of local granites, but there are few detailed studies of the tectonic setting during Cu-Mo mineralization in this area. The Nianzigou Mo deposit is located close to the northern margin of the North China Craton and in the eastern Central Asian Orogenic Belt and is a typical quartz-vein-type Mo deposit in the Xilamulun Mo ore belt. The granite in this deposit has high SiO2, Al2O3, K2O, and Na2O contents, and low MgO, CaO, and Fe2O3t contents. The granite is characterized by enrichments in large-ion lithophile elements and depletions in high-field-strength elements and, in particular, Sr, Ti, and P. The granite has high contents of rare-earth elements, is enriched in light rare-earth elements, and has marked negative Eu anomalies. The granite is an alkaline and calc-alkaline and metaluminous A-type granite. The zircon U-Pb ages of the monzogranite and granite porphyry are 157.2 ± 0.3 and 154.4 ± 0.4 Ma. The model age obtained by Re-Os isotopic dating is 154.3 ± 1.7 Ma, indicating that molybdenite mineralization also occurred during the Late Jurassic period. Given that the molybdenite Re contents are 7.8–24.9 ppm (average = 16.8 ppm), the ore-forming materials of the Nianzigou Mo deposit had a mixed crust–mantle source, but were mainly derived from the lower crust. Based on the geology and geochemistry, we propose that the Nianzigou Mo deposit formed in a postorogenic extensional tectonic setting associated with the southward subduction of the Mongol–Okhotsk oceanic plate.

Oxidation-reduction effects in the flotation of copper sulfide minerals and molybdenite – A proof of concept at industrial scale

Redox potential (Eh) control plays a significant role during sulfide mineral flotation by influencing the reactions on the surface of the minerals and accordingly the flotation behaviour. In this study, the metallurgical performance of typical copper sulfide minerals, molybdenite as well as gangue minerals (e.g., pyrite, tennantite, and enargite) under different pH and Eh conditions of the flotation cell were investigated. The copper and molybdenum processing plant at the Sungun complex-Iran were selected as a case study. For this purpose, Eh of flotation cells of phases 1 and 2 of copper and molybdenum processing circuits – Sungun complex – were measured by off-line method. After performing chemical analysis, the mineralogical study of the input load and products of each of the aforementioned flotation circuits in the rougher, cleaner, re-cleaner, and scavenger stages was performed. Based on the results, the potential in cells of phases 1 and 2 of copper concentration plants is in the range of −60 to −100 mV; and for the molybdenum plant, is in the range of −500 to −700 mV. The potentials of more than −100 mV in the phases of copper concentration plants have created suitable conditions for the separation of copper sulfide and molybdenite minerals from gangue minerals, especially pyrite. Adjustment of Eh in the range of −500 to −700 mV in the molybdenum processing plant has also led to the depression of copper minerals and the flotation of molybdenite, resulting in the effective separation of these minerals. However, grade analysis and mineralogical studies indicate the misplaced copper minerals into tailings, the passage of chalcopyrite and pyrite to molybdenum concentrate, the misplaced molybdenite to copper concentrate, and also the presence of minerals containing harmful elements such as arsenic in copper concentrate. Eh fluctuations in phase 1 and 2 of copper plants, the interaction of copper sulfide minerals, especially chalcopyrite with pyrite (and the depression of pyrite in Eh more than −100 mV), are reasons for the misplaced copper minerals into tailings. The interaction of chalcopyrite and pyrite with molybdenite and the high flotation tendency of molybdenite at the potential of +600 mV is the main factor in increasing the Cu and Fe grade in molybdenite concentrate. The interaction of copper minerals with arsenic-bearing minerals and the similar flotation behavior of these minerals in the potential of the rougher cells of the molybdenum processing plant has increased the arsenic grade in the copper concentrate or molybdenum tailings.

Evolution and genesis of hydrothermal fluids for the Cretaceous Dongnan Cu deposit, Zijinshan ore district (SE China)

The Dongnan Cu(-Mo) deposit is a newly discovered porphyry-epithermal system located between the Zijinshan high-sulfidation (HS) epithermal deposit and Luoboling porphyry deposit, within the Zijinshan ore district, a large porphyry-epithermal Cu-Au-Mo-Ag ore system in southeast China. The deposit offers a window to investigate the origins of hydrothermal fluids in a coupled porphyry-HS epithermal magmatic-hydrothermal system.Drill hole logging and alteration mineral mapping has identified four hydrothermal alteration and mineralization stages at the Dongnan deposit, namely: stage I porphyry-type alteration, which can be subdivided into stage IA potassic alteration and stage IB phyllic alteration, stage II HS mineralization and associated alteration which can be subdivided into stage IIA-1 pyrophyllite-dominated, stage IIA-2 illite and illite-montmorillonite and stage IIB dickite-dominated alteration, stage III late veins (i.e., calcite and fluorite) and stage IV supergene alteration. Chalcopyrite and molybdenite mineralization is associated with Stage I, whereas covellite and digenite mineralization formed during Stage II. Stage IB minerals (i.e., muscovite) were largely superimposed by minerals from stage II (i.e., dickite, kaolinite, pyrophyllite and alunite). Stage II epithermal alteration is located mainly in the western part of Zijinshan ore district, whereas the eastern part is dominated by porphyry-type mineralization and alteration. Microthermometry results show the average Th and salinity of each sample suite from stage IB ranging from 341 ± 22 to 442 ± 2 °C and 1.6 ± 1.6 to 19.2 ± 2.6 wt% NaCl equiv. By contrast, stage III fluid inclusions are liquid-dominated, with low temperature of homogenization and low salinity (156 ± 9 to 165 ± 4 °C and < 0.5 wt% NaCl equiv.). Thermodynamic modelling of stage II suggest that the fluid responsible for epithermal mineralization was characterized by high temperature (270 to 320 °C), high water to rock (w/r > 1) and high SO2 to H2S ratios (SO2/H2S > 1). Because stage IIA pyrophyllite alteration is overprinted by late stage IIB dickite alteration and relatively different forming condition for pyrophyllite (>270 °C) and kaolinite (<270 °C and w/r > 1), stage IIA and stage IIB may have resulted from two different fluids. The Dongnan porphyry-type mineralization formed mainly in response to the cooling and dilution, led by the mixing of acidic magmatic water with meteoric water, whereas stage II alteration was more likely related to volatile gas escaping, resulting in pH decrease and contributing to the formation of pyrophyllite, dickite and alunite.The distribution of alteration minerals and evolution of hydrothermal fluids all indicate that the hydrothermal fluids for the porphyry-type and HS epithermal-type alteration at Dongnan came separately from nearby Luoboling granodiorite porphyry and the Zijinshan HS epithermal Cu-Au deposit, which implies that Luoboling porphyry deposit and Zijinshan HS deposit formed from separate magmatic-hydrothermal events. It suggests that multiple magmatic centers exist in the Zijinshan ore district, a finding which will contribute to both understanding of ore genesis of this overprinted porphyry-epithermal deposit and further mineral exploration in the Zijinshan Ore district.

Trace element and isotopic (S, Pb) constraints on the formation of the giant Chalukou porphyry Mo deposit, NE China

Abstract Porphyry-type Mo deposits have supplied most of the Mo to the world. However, the source of the Mo and the controls on its enrichment in such deposits is still a matter of great debate. In this study, we present in situ trace element and isotopic data for a giant porphyry Mo deposit (the Chalukou Mo deposit in NE China) and use these data to address these issues. Three primary paragenetic stages of mineralization were recognized at Chalukou: (Stage I) K-feldspar + quartz + minor pyrite (Py-I) + minor molybdenite (Mol-I); (Stage II) quartz + sericite + molybdenite (Mol-II) + pyrite (Py-II); (Stage III) quartz + chlorite + epidote + fluorite + pyrite (Py-III) + galena + sphalerite + minor chalcopyrite. The bulk of the molybdenite was deposited in Stage II. In situ S isotope analyses of the sulfide ores show that the δ34S values vary from –5.2 to +7.8‰ (mean = +2.9‰) and correspond to δ34SH2S values from –2.4 to +3.3‰ (mean = +1.1‰). These values are consistent with a magmatic source for the sulfur. In situ Pb isotope compositions of the sulfide ores are almost identical to those of the local Mesozoic granites and other magmatic-hydrothermal ore deposits in this region, suggesting a close genetic association between the Mo mineralization and felsic magmatism. Pyrite from the three stages of mineralization differs significantly in its trace element composition. The first generation, Py-I, has a high Cu content (8.7 ± 49.6 ppm; where the first value is the median and the second is the standard deviation) and Mo content (6.9 ± 3.8 ppm). Pyrite-II has the lowest Cu concentration (1.3 ± 2.1 ppm) and a relatively high Mo concentration (5 ± 128 ppm), and Py-III has a high Cu content (8.7 ± 37.1 ppm) but the lowest Mo content (0.05 ± 5.7 ppm). From this, we infer that pyrite recorded the chemical evolution in the Mo/Cu ratio of the ore fluid and that this ratio reached a maximum in Stage II, coinciding with the widespread saturation of the fluid in molybdenite. The evolution of the Mo/Cu ratio in pyrite implies that the fluid was undersaturated in chalcopyrite at the high temperature of Stage I, despite the Cu concentration of the fluid apparently being at its high level, and chalcopyrite only saturated later, at a lower temperature. Molybdenite, however, because of its lower solubility, saturated early (Stage I) and in the subsequent stage (Stage II) was supersaturated in the fluid. There is a significant enrichment of Mo in the syn-ore intrusions at Chalukou compared to the pre-ore monzogranite. The very low Sr/Y ratios for the Chalukou syn-ore intrusions, which are in sharp contrast to the high Sr/Y ratios of the pre-ore monzogranite and those of porphyries related to Cu deposits, suggest that fractional crystallization of plagioclase may have been a key factor in generating the syn-ore magmas. Molybdenum is a highly incompatible metal and will concentrate in the crust, and assimilation of old continental crust, therefore, may explain the Mo enrichment of the syn-ore intrusions and ultimately the formation of the giant Chalukou deposit.

Lithogeochemical and isotopic characterization of Devonian molybdenite mineralization in the Pabineau Falls Granite, northeastern New Brunswick, Canada

An unusual molybdenite occurrence in northeastern New Brunswick, referred to herein as the Pabineau Lake Mo (PLM), is situated to the south of Bathurst. This occurrence consists of high-grade molybdenite-bearing granites that occur within the large Pabineau Falls Granite (PFG). To help evaluate the evolution of this occurrence, a large composite sample containing disseminated, very coarse molybdenite (up to 5.02 wt% MoS2) was collected from mineralized granitic blocks excavated from a blasted trench. Although the host rocks are assumed to be PFG, being the only defined intrusive body in the area, major- and trace-element geochemical data together with U-Pb geochronological results suggest that the molybdenite is hosted by an intrusion distinct from the PFG. The radiogenic Sr-Nd-Hf-Pb isotopic data of the host intrusion are consistent with Gander Zone granites of the Appalachians orogenic system.The PLM's granitic host rock is characterized by a high silica content (78.93 wt% SiO2), an enrichment in incompatible elements, and a high molybdenum content. The high initial 87Sr/86Sr of 0.71268, negative εNd of −1.28, and high Pb isotope ratios together with trace- and major-element concentrations indicate a moderately to highly radiogenic Sr source and derivation from a significant amount of supracrustal materials, with a contribution from the upper mantle; a source similar to that proposed for the Gander Zone Siluro-Devonian granitic bodies. A positive εHf (+1.34) also suggests involvement of sedimentary components. This is consistent with elevated Cr (20 ppm) and Ni (20 ppm). The involvement of a pelagic sedimentary component is invoked to explain the enrichment in elements commonly associated with mafic compositions.A new precise, LA ICP-MS zircon crystallization age of 390±1 Ma makes the PLM host granite Middle Devonian, which argues against a direct relationship with the older PFG (397.2±1.9 Ma). The new age opens the possibility of an as yet undelineated, mineralized intrusion within the Gander Zone, which has perhaps been missed during previous investigations due to the extensive glacio-fluvial cover and very limited bedrock exposures. Alternatively, the younger age could be attributed to very slow cooling and/or intra-pluton fractionation, resulting in a younger much more fractionated phase of the PFG. However, there is no geochemical evidence for such a prolonged continuous fractional crystallization process.Notably, recent geophysical surveys on the Bathurst Mining Camp indicate that the PFG is substantively larger than its surface expression as it continues to the east beneath the Carboniferous unconformity.Comparing ages of PLM and PFG with the nearby Nicholas-Denys Granodiorite (381±4 Ma) and Antinouri Lake Granite (372±4 Ma), it appears that magmatic activity in the region occurred every 10 Myr over a span of about 30 Myr.Collectively, this evidence suggests the potential of significant buried intrusions within this tectonic belt of the Gander Zone. At the PLM, this might include exposure of an otherwise hidden intrusion that is younger and much more fractionated than the PFG. More detailed geophysical and geochemical analyses would be required to revise the current geological map and, most importantly, trace unmapped units at depth to possible additional mineralized sequences.

Fluid evolution of the Zhunuo porphyry Cu-Mo deposit in Gangdese Tract, Tibet, China: A fluid-inclusion investigation

The Zhunuo porphyry Cu-Mo deposit in the western part of south Gangdese porphyry copper belt (GPCB), Tibet, is a large porphyry system. The Cu-Mo mineralization of this deposit is mainly associated with a weakly aluminous I-type Miocene granite porphyry pluton that formed in a post-collisional extensional tectonic setting. Field observations and petrographic studies demonstrate that emplacement of the pluton took place in several intrusive pulses, each with associated hydrothermal activities. Early hydrothermal alteration produced a potassic assemblage, overprinted by later phyllic alteration. At least three main stages of mineralization have been identified: (1) early A stage quartz + K-feldspar + minor sulfide veins; (2) middle stage B1-subtype veins composed of quartz + molybdenite + sporadic sulfide and B2-subtype quartz + pyrite + chalcopyrite veins; and (3) late stage pyrite + quartz D veins.Three types of fluid inclusions (FIs) in quartz were identified in the early and middle stages (i.e., CO2 bearing-aqueous vapor (V)-type and liquid (L)-type, and solid (S)-type); only aqueous L-type FIs were observed in the late stage minerals. S-type FIs contain variable solid particles, including halite, calcite, anhydrite (or gypsum), and chalcopyrite, hematite, and an unidentified transparent crystal. Only halite was dissolved during heating. Halite-bearing S-type FIs were mainly homogenized by halite dissolution at 300–470°C (S2-type), corresponding to salinities of 38.9–56.3 wt% NaCl equiv.; and minor halite bearing S-type FIs were homogenized to liquid at 360–520°C via vapor disappearance (S1-type), with salinities of 31.9–56.7 wt% NaCl equiv. Other FIs in minerals of A, B1, B2 and D veins were homogenized at temperatures of 350–550°C, 303–500°C, 305–460°C, and 250–347°C with salinities of 3.4–20.9, 2.6–22.4, 4.8–21.8, and 4.7–18.2 wt% NaCl equiv., respectively. These data suggest that the ore fluids forming the Zhunuo deposit changed from high-temperature, low-moderate salinity, CO2-bearing magmatic fluids to low-temperature, low-salinity and CO2-poor meteoric fluids. Phase separation and cooling caused the precipitation of the abundant chalcopyrite in the middle stage B2-subtype veins. The molybdenite mineralization was caused mainly by the decrease of pressure due to the release of CO2, and by phase separation of fluid in the middle stage as recorded in the B2-subtype veins. This hydrothermal ore-forming system is different from other magmatic-hydrothermal systems in GPCB, but is similar to the typical Cu-Mo porphyry systems, which were initially CO2-bearing as indicated by the presence of abundant CO2-bearing, low-moderate salinity FIs and calcite-bearing S-type FIs.

CONTROLS ON THE METAL ENDOWMENT OF PORPHYRY Mo DEPOSITS: INSIGHTS FROM THE LUMING PORPHYRY Mo DEPOSIT, NORTHEASTERN CHINA

AbstractProcesses controlling the metal endowment of arc-related porphyry Mo deposits are not well understood. Located in northeastern China, the arc-related Luming porphyry Mo deposit has a proven reserve of 0.75 Mt Mo at an average grade of 0.092 wt % and is characterized by multiple pulses of alteration and mineralization. These features make this deposit an ideal location to investigate the role of multiple pulses of magmatism and fluid release in the evolution and formation of an arc-related porphyry Mo deposit. Molybdenum mineralization at Luming is typically observed as a series of molybdenite-bearing veins hosted within a composite intrusive complex, referred to as the Luming Intrusive Suite. Crosscutting relationships between intrusive units and offset veins indicate that the Luming Intrusive Suite is composed of five major, successive granitic intrusions: the premineralization plutonic biotite monzogranite and monzogranite units, and the synmineralization stock- and dike-like porphyritic monzogranite, granite porphyry, and syenogranite units. Each synmineralization unit is associated with similar vein sequences that comply with the general form of early EB-type biotite veins, through A-type quartz ± biotite and B-type quartz-molybdenite veins, to late D-type quartz-molybdenite ± pyrite ± chalcopyrite, molybdenite, quartz-pyrite ± calcite, and calcite ± clays veins. The intensity and volume of alteration and mineralization within a given synmineralization unit decrease from early- through inter- to late-mineralization units. Although minor Mo mineralization is associated with potassic alteration along B-type veins, the majority of the ore is associated with D-type quartz-molybdenite-pyrite and molybdenite veins rimmed by sericite-chlorite-pyrite alteration, which are primarily hosted in the two premineralization units.A combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U-Pb and hydrothermal biotite 40Ar/39Ar studies, together with available isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS) molybdenite Re-Os data, has resulted in a substantial reappraisal of the timing of magmatism and its association with molybdenite mineralization at Luming. The volumetrically dominant premineralization intrusive units have indistinguishable zircon U-Pb weighted mean 206Pb/238U ages ranging from 187.5 ± 2.8 to 186.5 ± 3.6 Ma (2σ), whereas the synmineralization units yield weighted mean 206Pb/238U ages from 178.6 ± 2.2 to 175.6 ± 3.0 Ma (2σ). The zircon U-Pb weighted mean 206Pb/238U ages of the synmineralization units are indistinguishable from the mean molybdenite Re-Os model (178.1 ± 2.7; 2σ) and hydrothermal biotite 40Ar/39Ar plateau (174.7 ± 1.1 Ma; 2σ) ages within uncertainty, confirming a genetic link with mineralization. Melt inclusion data show that the synmineralization intrusions were Mo poor, with Mo concentrations &amp;lt;4 ppm.The data presented here suggest that molybdenite mineralization at Luming was most likely accomplished through three discrete magmatic-hydrothermal events during assembly of the Mo-poor synmineralization intrusive complex. The giant Luming deposit appears to be related to multiple pulses of magmatic-hydrothermal activities, resulting in the superposition of temporally distinct mineralization events. Our results suggest that pulsed release of ore-forming magmas and fluids, which are channeled along focusing structures like small porphyry fingers within a focused area, from a large magma chamber at depth may play a major role in the formation of large to giant porphyry Mo deposits of both the arc-related and Climax types. This conclusion is in line with field observations of a number of large to giant porphyry Mo deposits, which commonly show reversals in magmatic-hydrothermal evolutionary trend and are associated with multiple pulses of small stocks and dikes that are separate in time and space.

The Haidbach deposit in the Central Tauern Window, Eastern Alps, Austria: a metamorphosed orthomagmatic Ni-Cu-Co-PGE mineralization in the Polymetallic Ore District Venediger Nappe System – Hollersbach Complex

Abstract Cu-Ni-Co-PGE mineralization occurs at Haidbachgraben in the Early Palaeozoic, Subpenninic Hollersbach Complex of the Central Tauern Window, Austria. Massive sulfide ore formed from sulfide melt segregated from silicate melt during intrusion of pyroxenite into magmatic rocks formed in an MORB-type environment. Relics of magmatic minerals include chromian spinel and polyphase sulfide droplets composed of pyrrhotite, chalcopyrite and pentlandite preserved in recrystallized pyrite. Both ore and host rocks were multiply deformed and metamorphosed, leading to hornblendite carrying the ore, enveloped by chlorite-epidote schist. Conditions of – likely Variscan – amphibolite facies metamorphism are documented by relict pargasitic cores in hornblende and actinolite-tremolite, and by ternary sulfarsenide compositions in the Co-Ni-Fe solid solution series that are the most common accessory minerals found in the sulfide ore. Pyrrhotite, pentlandite, chalcopyrite and pyrite are the major sulfide minerals. Chalcopyrite is Cd-rich and retains a high-temperature magmatic signature. High Co/Sb and moderate Se/As ratios in pyrite also point to a magmatic environment of mineralization. The accessory mineral assemblage of small grain size (mostly &lt;10 µm) comprises native Au-Ag alloy and petzite as Au-Ag minerals, sperrylite, a variety of Pd tellurides and bismuthotellurides with elevated Sb, irarsite, and Re sulfides such as tarkianite and a Pb-Re sulfide. In addition, minor molybdenite, bournonite, scheelite and selenides have been identified. Two precious metal assemblages are present in individual samples: (1) hessite associated with Pd tellurides, often accompanied by sphalerite and chalcopyrite; (2) tarkianite forming euhedral inclusions in pyrite. Sperrylite and Au-Ag native alloys are present throughout and were also detected in silicate matrix. Most of the precious metal-bearing phases must have formed during recrystallization of base metal sulfides after the magmatic, and probably during later metamorphic events terminating in the Neoalpine Tauern crystallization.

Kivilompolo Mo mineralization in the Peräpohja belt revisited: Trace element geochemistry and Re-Os dating of molybdenite

The Kivilompolo molybdenite occurrence is located in the northern part of the Peräpoh jabelt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The minerali-zation occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.

Ore‐forming Fluid and Metallogenic Mechanism of Wolframite–Quartz Vein‐type Tungsten Deposits in South China

AbstractSouth China is endowed with copious wolframite–quartz vein‐type W deposits that provide a significant contribution to the world's tungsten production. Mineralization is spatially associated with highly evolved granites, which have been interpreted as products of ancient crustal anatexis. Ore veins are mainly hosted in low‐grade metamorphosed quartz sandstone, slate and granitic rocks. The ore minerals mainly comprise wolframite, cassiterite, scheelite and pyrite, with minor molybdenite, arsenopyrite and chalcopyrite. Typical steeply dipping veins can be divided into five zones from top to the bottom, namely: (I) thread, (II) veinlet, (III) moderate vein, (IV) thick vein, and (V) thin out zones. In general, three types of fluid inclusions at room temperature are commonly recognized in wolframite and/or quartz from these veins: two‐phase liquid‐rich (type L), two‐phase CO2‐bearing (type CB), and CO2‐rich (type C). Comparative microthermometry performed on fluid inclusions hosted in wolframite and associated quartz indicates that most wolframite was not co‐precipitated with the coexisting quartz. Detailed petrographic observation and cathodoluminescence (CL) imaging on coexisting wolframite and quartz of the Yaogangxian deposit, show repeated precipitation of quartz, wolframite, and muscovite, suggesting a more complex fluid process forming these veins. Previous studies of H‐O isotopes and fluid inclusions suggested that the main ore‐forming fluids forming the wolframite–quartz vein‐type deposits had a magmatic source, whereas an unresolved debate is centered on whether mantle material supplemented the ore‐forming fluids. The variable CO2 contents in the ore‐forming fluids also implies that CO2 might have had a positive effect on ore formation. Fluid inclusion studies indicate that wolframite was most likely deposited during cooling from an initial H2O + NaCl ± CO2 magmatic fluid. In addition, fluid‐phase separation and/or mixing with sedimentary fluid might also have played an important role in promoting wolframite deposition. We speculate that these processes determine the precipitation of W to varying degrees whereas the leading mechanistic cause remains an open question. Comprehensive studies on spatial variation of fluid inclusions show that both the steeply and gently dipping veins are consistent with the “five floors” model that may have broader applications to exploration of wolframite–quartz vein‐type deposits. Recent quantitative analysis of wolframite‐ and quartz‐hosted fluid inclusions by laser ablation inductively‐coupled plasma mass spectrometry shows enhanced advantages in revealing fluid evolution, tracing the fluid source and dissecting the ore precipitation process. Further studies on wolframite–quartz vein‐type W deposits to bring a deeper understanding on ore‐forming fluids and the metallogenic mechanism involved.

Natural molybdenite mineral enhanced polymeric carbon nitride nano-composites for efficient noble-metal-free photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution reaction (HER) is an ideal strategy to convert solar energy into chemical energy, while the efficiency is suppressed by limited light absorption, charge carrier separation and transfer, and interface reaction. Polymeric carbon nitride (PCN) as a metal-free visible-light photocatalyst has attracted increasing attention. However, expensive noble metal such as Pt nanoparticles are generally needed to co-catalyze HER on PCN and other photocatalysts. Herein, natural molybdenite mineral was introduced for the first time as co-catalyst to construct PCN/molybdenite nano-composites (PCN/Mo-x) by Na2SO4-assisted ball milling, which displayed a favorable noble-metal-free photocatalytic HER rate under visible light. Molybdenite not only replaced Pt co-catalyst to promote the separation efficiency of photo-induced electrons and holes but also enhanced the light absorption, synergistically increasing photocatalytic activities of PCN. The proposed path may pave the way to utilize the cheap minerals as promising candidates for co-catalysts in noble-metal-free photocatalysis on PCN and/or other photocatalysts.

Geochronology and fluid evolution of the Machangqing Cu-Mo polymetallic deposit, western Yunnan, SW China

The Machangqing porphyry-skarn Cu-Mo polymetallic deposit is located to the east of the Jinshajiang-Ailaoshan alkaline porphyry metallogenic belt in western Yunnan, SW China. Three major paragenetic stages have been identified in the Machangqing skarn mineralization, namely the (I) prograde skarn stage dominated by anhydrous minerals (e.g., garnet and pyroxene); (II) iron oxide stage dominated by magnetite and quartz, and coexisting hydrous minerals (e.g., epidote, biotite, allanite and chlorite) and trace sulfides (e.g., chalcopyrite, pyrite and molybdenite); (III) the main sulfide stage, dominated by quartz, chalcopyrite, pyrite and minor molybdenite. Zircon U-Pb dating of the ore-related granite porphyry yielded an age of 36.1 ± 0.2 Ma (n = 21; MSWD = 1.13), consistent with the reported skarn-related hydrothermal titanite U-Pb dating of 34.3 ± 1.2 Ma, indicating that the granite porphyry and skarn mineralization are closely related. Trace element compositions of these zircon grains demonstrate a positive Ce4+/Ce3+ (110–816, avg. = 401) vs. Ce/Nd (13.9–101, avg. = 36.0) correlation. The high zircon Ce4+/Ce3+ and Ce/Nd ratios point to an oxidized magma that produced hydrothermal fluids enriched in sulfophilic elements. Stage I garnet contains aqueous (L-type), halite-bearing (SH-type) and undissolved mineral-bearing (SU-type) inclusions, which homogenized at >590 °C with 47.4 wt% NaCl eqv. (SH-type) salinity. The hematite daughter mineral in SU-type indicates that the fluid in this stage is oxidized. Stage II quartz contains multiphase vapor-rich CO2-bearing C-type (4.8–11.1 wt% NaCl eqv.), SH-type (38.8 wt% NaCl eqv.) inclusions and coexisting vapor-rich (V-type) and L-type inclusions, which homogenized at around 350 °C. Stage III quartz contains L-, V-, C-, SH- and SU-type inclusions, which homogenized between 340 and 400 °C, yielding salinities from 2.7 to 20.3 and 29.2 to 53.3 wt% NaCl eqv. The coexistence of low-density (C-/V-type) and high-density (SH-type) inclusions with similar homogenization temperatures suggests that fluid boiling took place in stages II and III. It is concluded that the ore-forming fluids are characterized by high temperature, high salinity, high oxygen fugacity and high CO2 content. Fluid-rock interaction leads to magnetite crystallization and reduces the fluids, while fluid boiling causes escapes of CO2, increasing pH and sulfide precipitation.

Geochronology, geochemistry and fluid inclusions of the Yechangping giant porphyry-skarn Mo-W deposit, East Qinling, China

The Yechangping giant porphyry-skarn Mo-W deposit is located in the East Qinling molybdenum belt, Henan Province. Molybdenum mineralization occurs mainly as veins and veinlets or disseminated within dolomite and granite porphyry. The mineralized granite porphyry, emplaced at 148.1 ± 1.0 Ma, has petrological, mineralogical, and geochemical characteristics of I-type granite. The rock belongs to the high-K calc-alkaline to shoshonitic series and is characterized by enrichments in large ion lithophile elements and significant negative Eu, Ba, Sr, P, and Ti anomalies, attributed to strong fractional crystallization. The granite has negative whole-rock εNd(t) values (−13.2 to −12.4) and zircon εHf(t) values (−14.2 to −6.8), corresponding to old whole-rock Nd and zircon Hf model ages, which indicate that the primary magma was derived from partial melting of the ancient lower crust of the North China Craton.Four mineralization stages are identified in the Yechangping deposit. Stage I is a magmatic-hydrothermal transitional stage, which is respresented by the 1–5 mm-wide unidirectional solidification texture (UST), formed from fluids with high temperatures (375–504 °C), high/low salinities (46.3–51.0 vs. 7.81–13.75 wt% NaCl equiv.), and a high oxygen fugacity in an H2O-NaCl-CO2 fluid system. Stage II quartz-K-feldspar stockworks or quartz-K-feldspar-pyrite veins, with minor molybdenite, which are characterized by the K-feldspar and quartz with potassic-quartz alteration; they were formed from fluids with medium-high temperatures (320–464 °C), high/low salinities (38.8–43.4 vs. 5.41–12.85 wt% NaCl equiv.), and a relatively high oxygen fugacity. Stage III quartz-molybdenite stockworks and quartz-molybdenite-polymetallic veins, associated with quartz-sericite alteration, were formed from fluids with medium-low temperatures (273–396 °C), and variable salinities (3.38–40.0 wt% NaCl equiv.). Stage IV quartz-carbonate and fluorite veins, associated with fluid-related argillic alteration were characterized by low temperatures of 171–245 °C and low salinities of 3.23–8.00 wt% NaCl equiv.. The prolonged fractional crystallization, the high oxidization state of the magmatic-hydrothermal system and the fluid boiling process were the key factors that have contributed to the formation of the Yechangping giant Mo-W deposit.