Molybdenum Mineralization Research Articles

Discrete mineralization events at the Hongtuling Au-(Mo) vein deposit in the Xiaoqinling district, southern North China Craton: Evidence from monazite U-Pb and molybdenite Re-Os dating

The Xiaoqinling district, the second largest gold producer in China, is situated on the southern margin of the North China Craton and immediately to the north of the Qinling Orogen. The timing and genesis of the gold deposits have been hotly debated because the area has undergone multiple tectono-magmatic events since the stabilization of the North China Craton in the early Paleoproterozoic. Whether they are genetically related to the Triassic orogeny that formed the Qinling Orogen or associated with the early Cretaceous tectonic reactivation of the craton remains controversial. Here we present monazite U-Pb and molybdenite Re-Os dating results from the Hongtuling vein deposit in the eastern part of the Xiaoqinling district to provide new insights into the age and tectonic setting of gold mineralization. The Hongtuling deposit consists of gold veins at the top and minor molybdenum veins at the bottom, with molybdenum veins being locally crosscut by gold veins. Molybdenum veins mainly consist of calcite, quartz, K-feldspar, molybdenite, and pyrite with minor amounts of galena, and a variety of accessory minerals. Gold veins are dominated by quartz and pyrite, with minor to trace amounts of chalcopyrite, galena, sphalerite, and sericite. Monazite grains are well developed both in molybdenum and gold veins, and are intergrown with molybdenite and pyrite, respectively. Monazites from gold vein contain lower REEs contents, more prominent negative Eu anomalies, and higher Th/U ratios than those from molybdenum vein. The textural and geochemical evidence indicates that monazites from both veins precipitated from contrasting ore-forming fluids. Laser ablation ICP-MS U-Pb dating of monazite from the molybdenum vein yields a 206Pb/238U age of 203.5 ± 8.1 Ma (MSWD = 0.23, 2σ), which is statistically indistinguishable from the molybdenite Re-Os age of 204 Ma. In contrast, monazite from the gold vein has a significantly younger 206Pb/238U age of 130.4 ± 5.3 Ma (MSWD = 0.99, 2σ). Results presented here, combined with independent studies, suggest that the molybdenum and gold veins of the Hongtuling deposit, and by inference the other deposits in the district, formed in two discrete mineralization events in the late Triassic and early Cretaceous. The molybdenum mineralization is most likely related to the post-collisional magmatism associated with the Qinling orogeny, whereas gold mineralization occurred in an extensional setting associated with the decratonization of the North China Craton.

Zircon chemistry and new laser ablation U–Pb ages for uraniferous granitoids in SW Cameroon

The Ekomedion two-mica granite, southwestern Cameroon, has potential for uranium and molybdenum mineralization. Here, we present LA-ICP-MS U–Pb ages, Lu–Hf isotope characteristics, trace element concentrations and Ti-geothermometry of zircon from this granite hosting U–Mo mineralization in pegmatitic pods. The majority of zircon are CL-dark though some CL-bright cores were also identified. U–Pb zircon age data range from 121 ± 3 to 743 ± 11 Ma with only 5 of 34 ages being near concordant. The concordant mean age of 603 ± 12 Ma is similar to ages of granitic intrusions along the Central African Shear Zone in Cameroon. Apparent ages with mean of 261 ± 6 Ma reveal open system behavior with respect to Pb and/or U. Zircon eHfi values range from − 20.3 to − 0.3. This implies that U–Mo was remobilized during partial melting of the surrounding gneiss. Zircon Th/U > 0.1 as well as an increasing Hf with decreasing Th/U indicates that fractional crystallization was the main factor that controlled U–Mo mineralization in pegmatitic pods. Y and Y/Ho ratios cluster from 29 to 33 close to the chondritic ratio of 28 and indicate fractionation of Y and Ho with low F contents during the earliest stages of crystallization. Late stage accumulation of F-rich magmatic-hydrothermal fluids impacted U–Mo mineralization as a ligand. Zircon contains a prominent negative Eu anomaly pointing to a fractionating system rich in plagioclase. Calculated Ti-in-zircon temperatures span 672 °C to 1232 °C with the temperatures at the high end reflecting interference from mineral inclusions in the zircon grains while the lower temperature values are linked to crystallization.

In situ trace element and sulfur isotope of pyrite constrain ore genesis in the Shapoling molybdenum deposit, East Qinling Orogen, China

The Early Cretaceous (ca. 128 Ma) Shapoling vein-type molybdenum (Mo) mineralization, associated with the Huashan intrusion is a newly discovered deposit in the Xiong'ershan district, East Qinling, China where pyrite is a ubiquitous mineral phase. Here we present results from an integrated study on the texture, in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and sulfur isotopic composition using secondary-ion mass spectrometry (SIMS), with a view to understand the geochemical variation, genesis of Mo mineralization and ore-forming process. The distinct textural patterns as revealed by petrographic observations suggest three types of pyrites: Py1 is composed of coarse-grained euhedral pyrite in the wall rock and early barren quartz vein at Stage I, Py2 is represented by subhedral-anhedral grains coexisting with molybdenite in quartz veins at Stage II, and Py3 forms irregular interstitial grains in the quartz + K-feldspar + molybdenite dominated veins at Stage III. The Mo enrichment mainly occurred in Py3 (with Co/Ni ratios >1 and δ34S values mainly <0‰). Our study shows that Mo, Au, Pb, Zn, Ag and Cu are selectively partitioned into pyrite as mineral micro/nano-inclusions, and that the siderophile and chalcophile elements (such as Co, Ni, As, Se and Te) occur substituted within different textural types of pyrite. The δ34S values of the pyrites in Py1 and Py2 range between −2.33‰ and −0.37‰, indicating a dominantly magmatic origin. The δ34S values of Py3 increase from −2.55‰ to +1.48‰. In situ δ34S analysis of pyrite from Py1, Py2 to Py3 shows a progressive and gradual change in redox conditions. The negative values indicate oxidized sulfur in the early generation of pyrite (Py1 that coexists with magnetite). Conversely, positive values represent reduced sulfur found in the later generations of pyrite (Py3), which contain higher concentrations of Cu, Pb, Zn and Ag. The Mo-bearing pyrite identified in our study could be used as a possible pathfinder for the exploration of high-grade Mo mineralization.

Genesis of the Zhunsujihua porphyry Mo deposit in the Erenhot‐East Ujimqin metallogenic belt, Inner Mongolia, China: Evidence from geology, fluid inclusions, and isotope systematics

The newly discovered Zhunsujihua porphyry Mo deposit is located in the south‐western part of the Great Hingan Range, north‐east China. Molybdenum mineralization generally presents as veins or disseminations hosted in granitic intrusions, and multiple‐stage hydrothermal activity has resulted in potassic, phyllic, and sericitic alteration. The mineralization process can be divided into four stages, that is, quartz–K‐feldspar ± pyrite veinlets in stage I, quartz–molybdenite veinlets in stage II, quartz–polymetallic sulfide veinlets in stage III, and barren quartz–calcite veins in stage IV. Four types of fluid inclusions can be distinguished by petrography in hydrothermal quartz, including liquid‐rich two‐phase, vapour‐rich two‐phase, pure gaseous, and pure liquid inclusions, but quartz in stage I contains all types of fluid inclusions. The homogenization temperatures in quartz of stages I, II, III, and IV vary from 300°C to 520°C, 230°C to 410°C, 170°C to 260°C, and 136°C to 227°C, with salinities of 4.18–13.30 wt.% NaCl equiv., 2.07–11.10 wt.% NaCl equiv., 1.74–8.95 wt.% NaCl equiv., and 0.70–5.71 wt.% NaCl equiv., respectively. The ore‐forming fluids in this deposit are characterized by high temperature and intermediate to low salinity belonging to an H2O–NaCl system. δ18Oquartz values of quartz from stages I to IV range from +5.5‰ to +10.1‰, with the calculated δ18Ofluid values ranging from –6.7‰ to +6.3‰, and the δD values of fluid inclusion waters in quartz ranging from –118‰ to –102‰. The δ34S values of pyrite and molybdenite from different ore stages range from 3.8‰ to 6.8‰ with an average of 5.1‰. Pyrite and molybdenite samples in the deposit have 206Pb/204Pb ratios of 18.394 to 18.766, 207Pb/204Pb ratios of 15.580 to 15.694, and 208Pb/204Pb ratios of 38.309 to 38.942. All these observations reveal that the hydrothermal fluids of the Zhunsujihua porphyry Mo deposit have a dominantly magmatic signature with an input of meteoric water during the carbonate stage, and the ore‐forming components (metal and sulfur) were sourced from a greater magmatic source and some upper crustal materials.

Evolution of fluids in the Dasuji porphyry Mo deposit on the northern margin of the North China Craton: Constraints from Microthermometric and LA-ICP-MS analyses of fluid inclusions

The newly discovered Dasuji Mo deposit is located on the northern margin of the North China Craton, and the Mo mineralization is related to Triassic granite porphyry and quartz porphyry. Alteration associated with the deposit includes silicification, sericitization, chloritization, K-feldspathization, kaolinitization, carbonatization, and fluoritization. The silicification and sericitization (phyllic alteration) are closely related to the Mo mineralization. Based on mineral assemblages and cross-cutting relationships, the hydrothermal ore-forming process can be divided into four stages: stage 1 is characterized by K-feldspathization with minor molybdenum mineralization; stage 2 is the main stage of molybdenum mineralization; stage 3 is involved in lead-zinc mineralization; and stage 4 is characterized by no mineralization. Four types of fluid inclusions are recognized: liquid-rich, gas-rich, CO2-H2O, and daughter-mineral-bearing. Microthermometric data show a decrease in homogenization temperatures and salinities from the early to late stages, so that stages 1–4 show homogenization temperatures of 468–375, 435–271, 318–206, and 222–142 °C, respectively, and the fluids of stages 1, 3, and 4 had salinities of 2.57–16.50 (along with a few high-salinity inclusions: 32.04–48.05), 0.88–11.19, and 0.88–7.45 wt% NaCl equiv., respectively. The salinities of stage 2 fluid inclusions have a bimodal distribution: 1.40–17.48 and 29.20–53.25 wt% NaCl equiv. Laser ablation inductive coupled plasma mass spectrometer (LA-ICP-MS) analyses show that the fluid compositions are dominated by Na, K, Fe, and Mn. In stage 2 fluid inclusions, the Mo concentrations vary over a range of more than one order of magnitude (more than for any other element) as a result of fluid-rock interactions and molybdenite precipitation. Cu concentrations remain always relatively high in the fluids during their evolution (26–7092 ppm) because there was little chalcopyrite precipitation. The stage 3 fluid inclusions are rich in Mn, Pb, and Zn, while Ag concentrations increased in stage 3 and 4 fluid due to the addition of meteoric water from the surrounding rock. Reactions between the wallrock and hydrothermal fluids affected the composition of the hydrothermal fluids; sericitic alteration in particular had a great effect on fluid compositions, manifesting the variety of the content of Sr, Ba, Ca, Pb. The ore-forming fluids were mainly magmatic-hydrothermal fluids that were mixed with meteoric water during stages 3 and 4. Fluid immiscibility, a rapid decrease in pressure, fluid-rock reactions and fluid cooling were collectively responsible for the sulfide precipitation in the Dasuji deposit.

Genesis of the Yaguila Pb-Zn-Ag-Mo skarn deposit in Tibet: Insights from geochronology, geochemistry, and fluid inclusions

The Yaguila skarn deposit with reserves of 52 Mt at 4% Pb, 2% Zn, and 64.3 g/t Ag is located in the eastern segment of the central Lhasa subterrane, Tibet. The stratabound skarn Pb-Zn-Ag orebodies are hosted in the Upper Carboniferous-Lower Permian Laigu Formation, which consists of meta-quartz sandstone, slate, and marble. Molybdenum occurs as quartz-molybdenite ± pyrite veinlets, veins, and partial disseminations in the Paleocene quartz porphyry, slate, and garnet skarn. Zircon U-Pb dating suggests that three major magmatic events occurred in the Yaguila area, producing Cretaceous rhyolitic rock (ca. 128 Ma), Paleocene quartz porphyry (65.6 ± 1.2 Ma), and Miocene granite porphyry (17.8 ± 0.4 Ma). Combined with the published data, the quartz porphyry has variable εHf(t) values of −13.9 to +12.1, (87Sr/86Sr)i values of 0.71718–0.72805, and εNd(t) values of −5.2 to −13.5, whereas the granite porphyry displays relatively restricted εHf(t) values of +2.3 to + 6.5, (87Sr/86Sr)i values of 0.70798–0.71678, and εNd(t) values of −2.8 to −5.5. Geochemical and isotopic (Sr-Nd-Pb-Hf) signatures indicate that the Cretaceous rhyolitic magma was derived from the melting of continental lower crust of the ancient Lhasa subterrane with a strong fractional crystallization. The emplacement of the Paleocene quartz porphyry probably resulted from the magma mixing process between the dominant Lhasa middle-upper crust-derived magma and varying contributions of mantle-derived materials during the collision and Neo-Tethyan subduction slab rollback. The Miocene granite porphyry was likely formed by the melting of thickened Lhasa lower crust, which was triggered by upwelling of hot asthenosphere. Our molybdenite Re-Os data from garnet skarn, together with published data from quartz porphyry and slate, display an excellent isochron age of 64.3 ± 1.6 Ma. Fluid inclusion data from this study reveal that the ore-forming fluids associated with diverse types of molybdenum mineralization were a common magmatic-hydrothermal fluid with moderate to high temperatures (290–400 °C) and moderate salinities (9–22 wt% NaCl equiv.). Our study suggests that the Yaguila Pb-Zn-Ag and Mo mineralization occurred under the same ore system associated with the Paleocene quartz porphyry.

COMPLEX GOLD-MOLYBDENUM DEPOSITS AND OCCURRENCES IN GREENSTONE BELTS OF THE MIDDLE DNIPRO REGION OF THE UKRAINIAN SHIELD

The most important molybdenum mineralization of the Middle Dnipro province is limited to the Mesoarchean (3,1–2,9 Ga) Greenstone belts or structure (GSS). These are next occurrences: East-Sergiivka, Solone in the Sura GSS and Gannivka (district “Chervona”) in the Kryvyi Rih GSS. They have spatial combining or closeness with well-known gold deposits and occurrences: East-Sergiivka and Solone occurrences are located on the Eastern flanks of the Sergiivka and Balka Zolota deposits, respectively, in the sublatitudinal ore-bearing zones. From the West to the East gold mineralization gradually changes to gold-molybdenum and molybdenum. Gannivka molybdenum and Zhovtіanka gold occurrences are adjacent and localized in the submeridional zone of the Kryvyi Rih-Kremenchuk fault, and not spatially combined. However, similar to the etalon Lobash deposit, they can be combined as elements of a common ore-generating system related to a submeridional-extended granite massif undiscovered by erosion. In the process of previously performed geological surveys and related research, these ore prospects were studied and evaluated separately for each type of minerals. It is proposed to carry out further geological research in the context of spatially and genetically combining of gold and molybdenum mineralization. First of all it concerns deposits and occurrences of Sura GSS, where it is rationally to place two complex gold-molybdenum deposits: Sergiivka and Balka Zolota. This approach, which involves carrying out mining and exploration works on a joint scientific and technical base for molybdenum and gold ores, will undoubtedly have good economic efficiency and, ultimately, substantially increase the investment attractiveness of one or another deposit, facilitate the early launch industrial exploitation.

Discriminating characters of ore-forming intrusions in the super-large Chalukou porphyry Mo deposit, NE China

The Chalukou porphyry Mo deposit, located in the Great Hinggan Range, is the largest Mo deposit in northeast China, although the age and genesis of the associated magmatic intrusions remain debated. Here we report zircon U–Pb ages and trace elements, whole rock geochemistry and Sr–Nd isotope data with a view to understand the relationship between the magmatism and molybdenum mineralization. Zircon U–Pb analysis yield an age of 475 Ma for rhyolite in the older strata, 168 Ma for the pre-mineralization monzogranite, and 154 Ma for the syn-mineralization granite porphyry. The granite porphyry and quartz porphyry are considered as the ore-forming intrusions. These rocks are peraluminous, alkali-calcic, and belong to high-K to shoshonitic series with a strong depletion of Eu. They also display characteristics of I-type granites. The rocks exhibit wide variations of (87Sr/86Sr)i in the range of 0.705426–0.707363, and εNd(t) of −3.7 to 0.93. Zircon REE distribution patterns show characteristics between crust and the mantle, implying magma genesis through crust-mantle interaction. The Fe2O3/FeO values (average 1) for the whole rock and EuN/EuN∗ values (average 0.45), Ce4+/Ce3+ values (average 301) for zircon grains from the granite porphyry are higher than those from other lithologies. These features suggest that the ore-forming intrusions (syn-mineralization porphyry) had higher oxygen fugacity conditions than those of the pre-mineralization and post-mineralization rocks. The Chalukou Mo deposit formed in relation to the southward subduction of the Mongol-Okhotsk Ocean. Our study suggests that the subduction-related setting, crust-mantle interaction, and the large-scale magmatic intrusion were favorable factors to generate the super-large Mo deposits in this area.

Genesis of the Wurinitu W-Mo deposit, Inner Mongolia, northeast China: Constraints from geology, fluid inclusions and isotope systematics

The Wurinitu W–Mo deposit is located in the Erlian-East Ujimqin metallogenic belt in the Great Xing’an Range, NE China. Tungsten and molybdenum mineralization generally occurs as veins in quartz hosted by the Middle to Lower Ordovician wall rocks or as disseminations in the Early Cretaceous monzogranite intrusions. Fluid inclusion studies and multiple isotope analyses, provide systematic evidence to determine the evolution of the hydrothermal fluids, the source of metals and fluids, as well as mineral precipitation mechanisms, which are significant for the magmatic-hydrothermal system but are poorly understood. Three types of fluid inclusion assemblages (FIAs), including L (liquid-rich two-phase FIAs), V (vapor-rich two-phase FIAs), and L-V (liquid–vapor two-phase FIAs), have been identified in quartz veins from the W-mineralization (I), Mo-mineralization (II), and quartz – carbonate (III) stages at Wurinitu. The ore-forming fluids evolved from a high- to moderate-temperature and moderate- to low-salinity H2O–NaCl ± CO2 system in the W- and Mo- mineralization stages to a low-temperature and low-salinity H2O–NaCl system in the quartz-carbonate stage; they were trapped at temperatures of ∼365 °C, ∼266 °C, and ∼198 °C. The results of hydrogen and oxygen isotope analyses (δ18OH2O = −4.0 to +7.7‰; δDH2O = −116 to −92‰) indicate that the stage I fluids dominantly originated from magmatic water, and the stages II and III show addition of meteoric water. Sulfur (δ34SVCDT = 1.9–4.0‰) and lead isotope values (206Pb/204Pb = 18.099–18.728, 207Pb/204Pb = 15.527–15.616, and 208Pb/204Pb = 38.019–38.465) suggest that the ore metals in the hydrothermal fluids were derived from the granitic magma. All these observations reveal that (1) the Wurinitu W–Mo deposit is a magmatic-hydrothermal ore system, (2) W- and Mo- mineralization occurred under lithostatic pressure of 203–294 bars, and hydrostatic pressure of ∼102 bars, respectively, and (3) fluid boiling and mixing with meteoric water might be the key factors controlling the large-scale ore deposition at Wurinitu.

Geochemistry of Sandstone Type Uranium Deposit in Tarat Formation from Tim-Mersoi Basin in Northern Niger (West Africa): Implication on Provenance, Paleo-Redox and Tectonic Setting

The study aimed at investigating the geochemistry of a sandstone-type uranium deposit in Tarat formation for provenance, paleo-redox, tectonic setting in order to propose a geological model of uranium. X-Ray Fluorescence (XRF) and Induced Coupled Plasma Mass Spectrometry (ICP-MS) analyses were used to determine the sandstone composition. Major, trace and rare earth element compositions of the sandstones have been investigated to determine their provenance, tectonic setting and the influence of weathering conditions. Field studies of Tarat formation revealed that a major accident N30° that can be interpreted as an extension of the Austriche accident ensures the controls of Tarat sedimentation and mineralization deposits and the presence oxidized zone and reduced zone indicate the direction of circulation of the mineralized fluids from West to East. The uranium mineralization is disseminated as pitchblende that gives a yellow color to the sandstone while, molybdenum mineralization gives a blue color to the sandstone. Results of the Geochemical analysis indicate that the sandstone-type uranium deposit of Taratis classified into Protoquarzite (i.e. lithearenite and sublitharenite), arkose, subarkose, wacke and quartz arenite and varied in their maturity. Their Rare Earth Elements (REE) pattern displays high light REE over heavy REE, flat HREE and a significant negative Eu and Ce anomalies and in general correlated well with the NASC and PAAS average composition. The source area may have contained quartzose sedimentary rocks. The geochemical data support deposition in reducing environment of arid to humid climatic conditions rich in organic matter affected by passive margin (PM) tectonic setting and the sediments are derived from felsic and mafic source rocks. Trace and REE data as well as the high values of the weathering indices: Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA) and Chemical Index of Weathering (CIW) suggest intermediate to extreme weathering conditions in the source area or during transportation. The studied sandstones are inferred as highly mature sediments evidenced from their high SiO2/Al2O3 > 1 and the presence of the ultra-stable clay minerals, smectite, kaolinite, chlorite and illite. Also the Th/U < 3 ratio suggests high uranium enrichment of Tarat sandstones over crust average composition. From the factor analysis of the analyzed sandstone, there is no direct relationship between organic carbon and uranium, indicating the absence of organo-uraniferous composite and a major source derived from felsic to the mafic rock of Air Massif. The mineralized fluids of circulating from west to east are usually capped and underlain by impermeable mudstone or clay-rich units and uranium mineralization occurs in the association U-Mo-Pb or U-Zn-Ni-Pb structurally controlled by the major fault in Azaoua lineament fault NS of Arlit in the West, the N70° Tin Adrar “faisceau” in the North, the N30° Mouron accident in the Southeast, N30 Autriche accident in the West and precipitated in areas of suitable reducing environment of arid to humid climatic conditions rich in organic matter affected by passive margin (PM) tectonic setting. The negative correlation of U-Th and U-Na in our samples indicates intense remobilization of uranium in Tarat formation.

Typomorphic Characteristics of Molybdenite from the Bystrinsky Cu–Au Porphyry–Skarn Deposit, Eastern Transbaikal Region, Russia

The paper presents pioneering data on the composition, texture, and crystal structure of molybdenite from various types of molybdenum mineralization at the Bystrinsky Cu–Au–Fe porphyry–skarn deposit in the eastern Transbaikal region, Russia. The data were obtained using electron microprobe analysis (EMPA), laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS), and high-resolution transmission electron microscopy (HRTEM). Molybdenite found at the deposit in skarn, sulfide-poor quartz veins, and quartz–feldspar alteration markedly differs in the concentrations of trace elements determined by their species in the mineral, as well as in its structural features. Molybdenite-2H from skarn associated with phyllosilicates occurs as ultrafine crystals with uniform shape and texture; no dislocations or inclusions were found but amorphous silica was. The molybdenite composition is highly contrasting in the content and distribution of both structure-related (Re, W, and Se) and other (Mn, Co, Ni, Cu, Zn, As, Ag, Cd, Sb, Te, Ag, Pd, Au, Hg, Pb, and Bi) metals. In the sulfide-poor quartz veins, highly structurally heterogeneous (2H + 3R) molybdenite microcrystals with abundant defects (dislocations and volumetrically distributed inclusions) are associated with illite, goethite, and barite. Some single crystals are unique three-phase (2H + 3R polytypes + amorphous MoS2). The mineral has a low concentration of all trace elements, which are uniformly distributed. However, individual domains with uniquely high Pd, Te, Ni, Hg, and W concentrations caused by mineral inclusions are found in some grains. Molybdenite from quartz–feldspar alteration is characterized by low concentrations of all trace elements except for Re and Se, which enrich some domains of the grains. Our data indicate that the compositional and structural heterogeneity of molybdenite from the Bystrinsky deposit are its crucial features, which obviously correlate with the types of Mo mineralization.

Ore genesis and hydrothermal evolution of the Wulandele Mo deposit, Inner Mongolia, Northeast China: Evidence from geology, fluid inclusions and H–O–S–Pb isotopes

The newly identified Wulandele Mo deposit is located in the western part of the Great Xing’an Range, Northeast China. Molybdenum mineralization generally occurs as veins or disseminations hosted in Permian to Cretaceous granitic intrusions, associated with potassic alteration, silicification, greisenization and propylitic alteration. The ore-forming process can be divided into four stages: quartz ± K-feldspar ± biotite ± pyrite (stage I), quartz + molybdenite ± K-feldspar ± pyrite (stage II), quartz + chalcopyrite ± bornite (stage III), and quartz + carbonate (stage IV). Combined fluid inclusion microthermometry and stable and Pb isotopic compositions are used to constrain the hydrothermal processes and ore genesis of the Wulandele Mo deposit. Fluid inclusion data show four types of fluid inclusion assemblages (FIAs), i.e., L0 (liquid-rich two-phase FIAs), V0 (vapour-rich two-phase FIAs), C (CO2-rich FIAs), and rare L1 (liquid-rich three-phase FIAs with one transparent mineral), but only the former three types of FIAs were analysed. Aqueous and carbonic fluid inclusions occur in quartz veins of stages I and II, and only aqueous inclusions are observed in stages III and IV. Hydrogen and oxygen isotopic compositions of quartz indicate a primarily magmatic origin, and the proportion of meteoric water increased during the ore-forming process. Sulfur (δ34SVCDT = 1.90–4.19‰) and lead isotopes suggest that the ore-forming materials came predominantly from magmatic fluids. The Wulandele Mo deposit was formed by an initially high-temperature, high-oxygen fugacity and CO2-rich fluid system at an estimated depth of ∼0.4 to 3.3 km. Decreases in temperature and fO2 as well as the input of meteoric water were critical factors for sulfide precipitation. Combining the integrated analysis of deposit geology, the fluid evolutionary process, and the ore-forming environment, we suggest that the Wulandele deposit should be classified as a porphyry Mo deposit that was formed in a continental collision orogen during post-collisional extension associated with the consumption of the Mongol–Okhotsk ocean in NE China.

Geology, geochronology and geochemistry of the Dabate Cu–Mo deposit, northern Chinese Tien Shan: Implications for spatial separation of copper and molybdenum mineralization

The Dabate deposit is a porphyry Cu–Mo deposit located in the Sailimu Block, northern Chinese Tien Shan. The deposit shows a clear separation of Cu and Mo mineralization, with Cu mineralization occurring along the edge of the rhyolitic porphyry, and Mo mineralization in the inner part of the rhyolitic porphyry. Sm-Nd isotopic analyses of six fluorite samples from the Cu sulfides–fluorite veins yield an isochron age of 298.1 ± 5.0 Ma, and Re-Os isotopic analyses of four molybdenite samples from the molybdenite–quartz veins yield an isochron age of 299.6 ± 3.2 Ma. These geochronological data and accompanying geologic evidence indicate that the Cu and Mo mineralization belongs to the same hydrothermal system and are closely related to the rhyolitic porphyry, which has a youngest zircon 206Pb/238U age of 297.3 ± 8.0 Ma.Rare earth element (REE) and fluid inclusion studies were carried out for fluorite in the Cu ores. The fluorite related to Cu mineralization have high ΣREE (63.4–216.9 ppm) and show generally similar REE patterns with the rhyolitic porphyry, suggesting that the fluid of Cu mineralization is closely related to the rhyolitic porphyry. The slight LREE-depletion and Ce-depletion of fluorite relative to the rhyolitic porphyry may be due to preferential partitioning of HREE into the fluid in neutral to weak alkaline conditions and to mixing with meteoric water which is characterized by Ce-depletion. Three types of fluid inclusions were recognized in the fluorite from the Cu sulfides–fluorite veins: liquid–vapor (LV-type), CO2-bearing (C-type) and solid mineral-bearing (S-type). The LV-type inclusions have homogenization (vapor to liquid) temperatures from 175 to 328 °C and salinities of 0.4∼14.9 wt% NaCl eqv. (mode at 0∼8 wt% NaCl eqv.), and is of H2O + NaCl composition. The C-type inclusions have homogenization (vapor to liquid) temperatures from 206 to 279 °C and salinities of 1.6∼8.5 wt% NaCl eqv., and is of H2O + CO2 + NaCl + CH4 composition. The S-type inclusions have partial homogenization (vapor to liquid) temperatures of 173–233 °C and salinities of 1.2–7.9 wt% NaCl eqv., and is of H2O + NaCl composition. The solid particle in S-type inclusions did not change during heating up to 550 °C, indicating that the solid is not daughter mineral and the S-type inclusions are actually the same as the LV-type inclusions. The LV-type inclusions have microthermometric attributes similar to those typically found in the late stages of porphyry deposits, whereas the C-type inclusions have similar compositions as the inclusions in the Mo ores as documented in previous studies at Dabate. The presence of both LV-type and C-type inclusions suggests that the Cu mineralization may be related to mixing between meteoric water and magmatic fluids, as is also indicated by the REE of fluorite.Comparing with data from Mo ores reported in previous studies, it is suggested that the Mo-stage fluids were more reduced and acidic and Mo mineralization may be mainly related to fluid pressure decrease and immiscibility, whereas the Cu-stage fluids were more oxidized, neutral to weakly alkaline and Cu mineralization may be mainly controlled by mixing and cooling. The vapor phase produced by fluid immiscibility in the deep area may have carried Cu, As, Ag, HF, CO2 and migrated to the outer part of the porphyry, precipitated Cu sulfides, arsenopyrite and fluorite by mixing with meteoric water from the country rocks. Whereas the liquid phase produced by fluid immiscibility at depth may have carried Mo, NaCl and migrated to the middle-west part of the rhyolitic porphyry, become immiscible and precipitated molybdenite.

Whole rock geochemistry, molybdenite Re-Os geochronology, stable isotope and fluid inclusion investigations of the Siah-Kamar deposit, western Alborz-Azarbayjan: New constrains on the porphyry Mo deposit in Iran

The Siah-Kamar porphyry Mo deposit, located in the western Alborz-Azarbayjan magmatic belt, is the first and largest Mo deposit in the Iran. This deposit is mainly hosted by an I-type, shoshonitic quartz monzonite to monzonite intrusion and also extends in the surrounding lower to middle Eocene volcanic rocks. The geochemical features of the Siah-Kamar intrusion show enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), and significant negative anomalies of Nb, Ta and Ti analogues to the magmas derived from metasomatized sub-continental mantle. Porphyry molybdenum mineralization is associated with potassic, sericitic, argillic, and propylitic alteration zones. Mineralization occurs in disseminated form, in veins/veinlets and in hydrothermal breccias. The main ore minerals comprise molybdenite, chalcopyrite and bornite. The Microthermometric analyses at Siah-Kamar deposit showed that the halite-bearing inclusions contain high salinity (30.9–60.7wt% NaCl eq.) with homogenization temperature ranging from 226°C to 397°C. The homogenization temperature of two phase liquid-rich inclusions range between 224°C and 375°C. The salinity of this type inclusions range from 0.6 to 7.5wt% NaCl equivalent. The two-phase vapor-rich fluid inclusions homogenized at 270°C to 397°C. The salinity of this type fluid inclusions lie within the range of 0.6 to 4.24wt% NaCl equivalent. Coexisting two phase V-rich and L-rich fluid inclusions in quartz associated with molybdenite provide evidence for boiling at 270°C to 400°C. The δ18Owater values of quartz in the molybdenite-bearing veins vary from +2.16 to +4.05‰, suggesting a magmatic origin for the ore-forming fluids. Re-Os isotopic dating of molybdenite indicated a mineralization age of 41.9±3.6Ma. The Re concentration in molybdenite suggests incorporation of mantle derived melt with crustal materials. The late Eocene magmatism along the western Alborz-Azarbayjan magmatic zone resulted from the Neo-Tethys subduction beneath the Iranian plateau. The Siah-Kamar monzonitic intrusion hosting the Mo deposit, could be considered asan example among the late Eocene intrusions within the western Alborz-Azarbayjan magmatic zone for any further exploration in this zone.

Two different types of granitoids in the Suyunhe large porphyry Mo deposit, NW China and their genetic relationships with molybdenum mineralization

The Suyunhe large porphyry Mo deposit (∼0.57Mt molybdenum), located in the West Junggar, NW China, is the largest known porphyry Mo deposit in Xinjiang. Granitoids in this deposit are mainly characterized by three closely spaced intrusive centers (known as stocks I, II and III respectively). The stocks I and III mainly consist of barren granodiorite porphyry and tonalite porphyry, whereas the stock II is mainly composed of fertile monzonitic granite porphyry and granite porphyry. Based on detailed major and trace element, and Sr–Nd isotopic analyses, two distinct compositional groups can be identified. The first group of high-silica end-members (HSE) is characterized by high SiO2 (mostly >75wt%), low MgO (0.07–0.69wt%) and Mg# (0.19–0.36), significant Eu depletion in the chondrite-normalized diagram, and low Sr/Y and La/Yb, as well as noticeably negative anomalies of Ba, Sr, P and Ti in the primitive mantle-normalized diagram. The second group of low-silica end-members (LSE), however, displays adakite-like features with lower SiO2 (<75wt%), higher MgO (0.52–1.32wt%) and Mg# (0.32–0.52; mostly >0.4), and higher Sr/Y (mostly >20) and La/Yb (>8). The depleted Sr–Nd isotopic characteristics (εNd(T)=3.5–6.4 and Isr=0.7026–0.7055) and young two-stage model ages of HSE and LSE indicate that they were both derived from partial melting of juvenile lower crust that might be triggered by asthenosphere upwelling subsequent to a slab rollback event. However, the depths of initial melting might be different. The current evidence demonstrates that HSE in the Suyunhe deposit formed by partial melting of juvenile crust at depths of less than ∼33km with a plagioclase residue, whereas that for LSE occurred at depths of >40km where a garnet residue existed and the crust was thickened. The lower source depth, as well as subsequently strong plagioclase fractionation, results in the absence of adakite-like characteristics in HSE.The Ce4+/Ce3+and EuN/EuN∗ ratios in zircons of HSE are much lower than ore-forming intrusions from porphyry Cu deposits in the Central Asian Orogenic Belt, but noticeably higher than barren intrusions from the Lachlan fold belt and ore-bearing intrusions from small-intermediate porphyry Mo deposits from the East Qinling–Dabie and the Nanling metallogenic belts, China, indicating that neither too high nor too low oxygen fugacities are favorable for large porphyry Mo deposits. Based on previous studies of adakitic rocks in the world, adakite-like LSE in the Suyunhe deposit are believed to have higher oxygen fugacities, and thus be less fertile than HSE. We finally suggest that adakites and adakite-like rocks are unproductive for porphyry Mo deposits.

Zircon and molybdenite geochronology and geochemistry of the Kalmakyr porphyry Cu–Au deposit, Almalyk district, Uzbekistan: Implications for mineralization processes

Copper, gold and molybdenum mineralization of the Kalmakyr porphyry deposit in Uzbek Tien Shan occurs as stockworks, veinlets and disseminations in the phyllic and K-silicate alteration zones developed predominantly in a middle to late Carboniferous intrusive complex composed of monzonite and granodiorite porphyry. Zircon U–Pb dating yielded an age of 327.2±5.6Ma for the ore-hosting monzonite and an age of 313.6±2.8Ma for the ore-bearing granodiorite porphyry. Re–Os dating of seven molybdenite samples from stockwork and veinlet ores yielded model ages from 313.2 to 306.3Ma, with two well-constrained isochron ages of 307.6±2.5Ma (five stockwork ores) and 309.1±2.2Ma (five stockwork ores and two veinlet ores), respectively. These results indicate that Cu–Au mineralization post-dated the emplacement of the monzonite, started right after the emplacement of the granodiorite porphyry, and lasted for ca. 7Ma afterward. The geochronological and geochemical data suggest that the Kalmakyr deposit was formed in a late Carboniferous mature magmatic arc setting, probably related to the latest subduction process of the Turkestan Ocean beneath the Middle Tien Shan. The εHf(t) values of zircon grains from the monzonite vary from +11 to +1.7, with an average of +5.1, and those of zircon grains from the granodiorite porphyry range from +5.7 to −1.8, with an average of +2.4. These data indicate that the magma of both monzonite and granodiorite porphyry was derived from partial melting of a thickened lower crust with input of mantle components and variable crustal contamination, and that there was more mantle contribution to the formation of the monzonite than the granodiorite porphyry. The high rhenium concentrations of molybdenite (98–899ppm) also indicate major mantle contribution of rhenium and by inference ore metals. The relatively high EuN/EuN∗ values (average 0.68), Ce4+/Ce3 values (average 890) and Ce/Nd values (average 36.8) for zircon grains from the granodiorite porphyry than those from the monzonite (average EuN/EuN∗=0.33, average Ce4+/Ce3=624, average Ce/Nd=3.9) suggest that the magma for the syn-mineralization granodiorite porphyry has higher oxygen fugacity than that for the pre-mineralization monzonite. Based on these data, it is proposed that while the monzonite was emplaced, the oxygen fugacity and volatile contents in the magma were relatively low, and ore metals might disperse in the intrusive rock, whereas when the granodiorite porphyry was emplaced, the oxygen fugacity and volatile contents in the magma were increased, favoring copper and gold enrichment in the magmatic fluids. The Kalmakyr deposit formed from a long-lived magmatic-hydrothermal system connected with fertile magmatic sources in relation to the subduction of the Turkestan Ocean beneath the Middle Tien Shan.

Molybdenum mineralization related to the Yangtze's lower crust and differentiation in the Dabie Orogen: Evidence from the geochemical features of the Yaochong porphyry Mo deposit

The Dabie Orogen is a world-class case for large amounts of Mo mineralization in that it contains at least 10 porphyry Mo deposits with Mo metal reserves over 3Mt from the time period of 156–110Ma. However, the principal mechanism for the Mo mineralization remains controversial due to the lack of a precise definition of its source and shallow ore-forming process, which is essential to understand these rare large Mo deposits.Detailed geochronology, geochemistry, and isotopic data for ore-related granites and minerals were analyzed in order to place constraints on the massive Mo mineralization in the Dabie Orogen in eastern China. The Yaochong molybdenum orebodies were hosted in the transition belt and alteration zone between the granitic stocks and the Dabie Complex and were characterized as numerous veinlets with potassic, phyllic and propylitic alterations. The buried Yaochong granitic intrusions and associated molybdenum mineralization yield Early Cretaceous ages of magmatic activities at ca. 138Ma and extremely similar Re–Os isotope ages for the corresponding Mo metallogenic event at ca. 137Ma. The Yaochong monzogranite and granite porphyry belong to the highly fractionated I-type granites, which are believed to be derived from the dominantly Yangtze's lower crust mixed with the Northern Dabie Complex due to their geochemical and isotope features. The elemental diversity and isotopic homogeneity suggest that the formation of the Yaochong monzogranite involved the fractionation of biotite, garnet and minor feldspar and accessory minerals combined with a weak crustal assimilation process. In contrast, the granite porphyry was possibly generated by the partial melting of the same mixed lower continental crust via the differentiation process involving the fractionation of feldspar, apatite, and/or titanite. Fractional crystallization processes can significantly elevate the molybdenum concentration in the residual melts. The biotite fractional crystallization results in removal of molybdenum from the vestigial magma since molybdenum is compatible with it, which may account for the barren monzogranite with a low-grade molybdenum mineralization. The ore-bearing granite porphyry has more source materials from the Yangtze's lower crust, which may have contributed most of the molybdenum for the porphyry-related molybdenum deposits in the Dabie metallogenic zone. This porphyry molybdenum aggregation may have been deposited in a post-collision or intracontinental extensional setting.

Magmatic hydrothermal origin of the Hadamengou-Liubagou Au-Mo deposit, Inner Mongolia, China: Constrains on geology, stable and Re-Os isotopes

The Hadamengou-Liubagou Au-Mo deposit is the largest gold deposit in Inner Mongolia of North China. It is hosted by amphibolite to granulite facies metamorphic rocks of the Archean Wulashan Group. To the west and north of the deposit, there occur three alkaline intrusions, including the Devonian-Carboniferous Dahuabei granitoid batholith, the Triassic Shadegai granite and the Xishadegai porphyritic granite with molybdenum mineralization. Over one hundred subparallel, sheet-like ore veins are confined to the nearly EW-trending faults in the deposit. They typically dip 40° to 80° to the south, with strike lengths from hundreds to thousands of meters. Wall rock alterations include potassic, phyllic, and propylitic alteration. Four distinct mineralization stages were identified at the deposit, including K-feldspar-quartz-molybdenite stage (I), quartz-pyrite-epidote/chlorite stage (II), quartz-polymetallic sulfide-gold stage (III), and carbonate-sulfate-quartz stage (IV). Gold precipitated mainly during stage III, while Mo mineralization occurred predominantly in stage I. The δDH2O and δ18OH2O values of the ore-forming fluids range from −125‰ to −62‰ and from 1.4‰ to 7.5‰, respectively, indicating that the fluids were dominated by magmatic water with a minor contribution of meteoric water. The δ13CPDB and δ18OSMOW values of hydrothermal carbonate minerals vary from −10.3‰ to −3.2‰ and from 3.7‰ to 15.3‰, respectively, suggesting a magmatic carbon origin. The δ34SCDT values of sulfides from the ores vary from −21.7‰ to 5.4‰ and are typically negative (mostly −20‰ to 0‰). The wide variation of the δ34SCDT values, the relatively uniform δ13C values of carbonates (typically −5.5‰ to −3.2‰), as well as the common association of barite with sulfides suggest that the minerals were precipitated under relatively high fo2 conditions, probably in a magmatic fluid with δ34SƩS≈0‰. The Re-Os isotopic dating on molybdenite from Hadamengou yielded a weighted average age of 381.6±4.3Ma, indicating that the Mo mineralization occurred in Late Devonian. Collectively, previous 40Ar-39Ar and Re-Os isotopic dates roughly outlined two ranges of mineralizing events of 382–323Ma and 240–218Ma that correspond to the Variscan and the Indosinian epochs, respectively. The Variscan event is approximately consistent with the Mo mineralization at Hadamengou-Liubagou and the emplacement of the Dahuabei Batholith, whereas the Indosinian event roughly corresponds to the possible peak Au mineralization of the Hadamengou-Liubagou deposit, as well as the magmatic activity and associated Mo mineralization at Xishadegai and Shadegai. Geologic, petrographic and isotopic evidence presented in this study suggest that both gold and molybdenum mineralization at Hadamengou-Liubagou is of magmatic hydrothermal origin. The molybdenum mineralization is suggested to be associated with the magmatic activity during the southward subduction of the Paleo-Asian Ocean beneath the North China Craton (NCC) in Late Devonian. The gold mineralization is most probably related to the magma-derived hydrothermal fluids during the post-collisional extension in Triassic, after the final suturing between the Siberian and NCC in Late Permian.

Late Mesozoic magmatism and metallogeny in NE China: The Sandaowanzi–Beidagou example

ABSTRACTThe Sandaowanzi (>22t Au) and Beidagou (>5t Au) tellurium–gold deposits are located in the northeastern Central Asian Orogenic Belt (Heilongjiang Province, NE China). The ore-hosting volcanic rocks unconformably overly monzogranite and were intruded by adakitic granodiorite. In this study, we report new-age, geochemical, and Sr–Nd–Pb isotopic data to elucidate the genetic link between the igneous rocks and the Te–Au mineralization. New-age data indicate that local magmatism occurred in the Early Jurassic (ca. 177.2 Ma) and Early Cretaceous (ca. 118.7 − 122.0 Ma). Geochemically, the igneous rocks are enriched in LREEs, Pb, K, and U, and depleted in Nb, P, and Ti, showing calc-alkaline affinity. The Early Jurassic monzogranite rocks are featured by 87Sr/86Sr = 0.7111−0.7118; εNd(t) = −4.6 to −4.7; 206Pb/204Pb = 18.098−18.102, 207Pb/204Pb = 15.558−15.580, and 208Pb/204Pb = 37.781−37.928, whereas the Early Cretaceous adakitic granodiorite contains: 87Sr/86Sr = 0.7071−0.7073; εNd(t) = − 3.4 to −3.2; 206Pb/204Pb = 17.991−18.080, 207Pb/204Pb = 15.483−15.508, and 208Pb/204Pb = 37.938−37.985. Initial isotopic ratios for the Early Cretaceous volcanic rocks: 87Sr/86Sr = 0.7061−0.7087; εNd(t) = − 3.6 to −2.9; 206Pb/204Pb = 18.136−18.199, 207Pb/204Pb = 15.512−15.628, and 208Pb/204Pb = 38.064−38.155. The pyrite, chalcopyrite, and telluride grains yielded δ34S of −6.52 ‰ to 2.13 ‰ (mean = − 0.82 ‰) and δ13CPDB of the calcite samples are in the range of −6.64 ‰ to −5.24 ‰, implying the ore materials were derived from mantle. The geochemical and isotopic results indicate that primary melts of Late Mesozoic magmatic rocks have features by partial melting of the continental crust. The adakitic rocks may have been the products of the thickened lower crustal delamination and the subsequent asthenospheric upwelling during the intra-continental extension in NE China. Regionally, intrusive activity and molybdenum mineralization during the Jurassic was affected by subduction setting, whereas gold mineralization was controlled by the Early Cretaceous tectonothermal events associated with a superposition extension.

Fluid inclusions and C-H-O-S isotope systematics of early Permian porphyry Mo mineralization of the West Junggar region, NW China: the Suyunhe example

ABSTRACTThe Suyunhe porphyry Mo deposit, located in the West Junggar terrane, is the largest molybdenum deposit found in Xinjiang to date, with a proven reserve of 0.57 Mt. The Suyunhe deposit is associated with Early Permian granitic rocks, which emplaced into the volcano-sedimentary sequences of the Middle Devonian Barluk Formation. Four metallogenic stages are identified in this study. Stage I is marked by the quartz-magnetite-K-feldspar±biotite±pyrite±molybdenite veins, which mainly occurred in the intensively potassic alternation zone and were formed at high temperature (>481°C), high salinity (58.6−65.18 wt.%), and relatively high oxygen fugacity conditions with a fluid system of NaCl-H2O-CO2. Stage II is the main metallogenic stage and develops numerous quartz-molybdenite±pyrite veins associated with muscovite–chlorite alteration, which were formed by immiscible fluids at medium-high temperature (210−427°C), medium-high salinity (43.36−49.90 wt.%), and relatively low oxygen fugacity conditions with the fluid system of NaCl-H2O-CO2-CH4-C2H6. After the main Mo-mineralization, quartz-polymetallic sulphides veins associated with quartz–sericite alteration were formed by fluids at medium-low temperature, low-salinity conditions with the fluid system of NaCl-H2O-CO2 in stage III. The following quartz-polymetallic sulphide veins are quartz-calcite±pyrite veins associated with calcite alteration, which were formed by fluids at low temperature and low-salinity conditions with a fluid system of NaCl-H2O in stage IV.The δ18O‰ values indicate that the ore fluids of stages I and II are dominated by magmatic water, whereas stages III and IV are dominated by meteoric water. A wide range of δ34S‰ values (−7.1 to 3.4‰) of sulphides between stages I and II indicates that increasing the reducibility plays an important role in molybdenum mineralization. The δ13CCH4 values suggest that CH4 of the ore fluids mainly results from the assimilation–contamination of carbonaceous country rocks, and partly derives from magma. However, the δ13CCO2 values suggest that CO2 of the ore fluids mainly originates from magma, and minor derives from wall-rocks as well as meteoric water.