Genesis of the Bianjiadayuan Pb-Zn polymetallic deposit,Inner Mongolia,China:Constraints from in-situ sulfur isotope and trace element geochemistry of pyrite

The Southern Great Xing'an Range(S(GXR)which forms part of the eastern segment of the Central Asian Orogenic Belt(CAOB)is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a number of porphyry Mo(Cu),skarn Fe(Sn),epithermal Au-Ag,and hydrothermal veintype Ag-Pb-Zn ore deposits.Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR.Porphyry Sn± Cu± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field.We identify a five-stage mineralization process based on field and petrologic studies including(i)the early porphyry mineralization stage,(ii)main porphyry mineralization stage,(iii)transition mineralization stage,(iv)vein-type mineralization stage and(v)late mineralization stage.Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage,and we identify corresponding four types of pyrites:Pyl is medium-grained subhedral to euhedral occurring in the early barren quartz vein;Py2 is medium-to fine-grained euhedral pyrite mainly coexisting with molybdenite,chalcopyrite,minor sphalerite and galena;Py3 is fine-grained,subhedral to irregular pyrite and displays cataclastic textures with micro-fractures;Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena.LA-ICP-MS trace element analyses of pyrite show that Cu,Pb,Zn,Ag,Sn,Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions,whereas Co,Ni,As and Se enter the lattice via isomorphism in all types of pyrite.The Cu,Zn,Ag,Cd concentrations gradually increase from Pyl to Py4,which we correlate with cooling and mixing of ore-forming fluid with meteoric water.Py2 contains the highest contents of Co,Ni,Se,Te and Bi,suggesting high temperature conditions for the porphyry mineralization stage.Ratios of Co/Ni(0.03-10.79,average 2.13)and sulphur isotope composition of sulfide indicate typical hydrothermal origin for pyrites.The δ~(34)S_(cDT) values of Pyl(0.42‰-1.61‰,average1.16‰),Py2(-1.23‰to 0.82‰,average 0.35‰),Py3(—0.36‰to 2.47‰average 0.97‰).Py4(2.51‰--3.72‰,average 3.06‰),and other sulfides are consistent with those of typical porphyry deposit(-5‰to 5‰),indicating that the Pb-Zn polymetallic mineralization in the Bianjiadayuan deposit is genetically linked to the Yanshanian(Jurassic-Cretaceous)magmatic-hydrothermal events.Variations of δ~(34) S values are ascribed to the changes in physical and chemical conditions during the evolution and migration of the ore-forming fluid.We propose that the high Sn content of pyrite in the Bianjiadayuan hydrothermal vein-type Pb-Zn polymetallic deposit can be used as a possible pathfinder to prospect for Sn mineralization in the surrounding area or deeper level of the ore field in this region.     

Geochronology and Genesis of the Tiegelongnan Porphyry Cu(Au) Deposit in Tibet: Evidence from U–Pb,Re–Os Dating and Hf,S, and H–O Isotopes

The Tiegelongnan Cu (Au) deposit is the largest copper deposit newly discovered in the Bangong–Nujiang metallogenic belt. The deposit has a clear alteration zoning consisting of, from core to margin, potassic to propylitic, superimposed by phyllic and advanced argillic alteration. The shallow part of the deposit consists of a high sulphidation‐state overprint, mainly comprising disseminated pyrite and Cu–S minerals such as bornite, covellite, digenite, and enargite. At depth porphyry‐type mineralization mainly comprises disseminated chalcopyrite, bornite, pyrite, and a minor vein molybdenite. Mineralization is disseminated and associated with veins contained within the porphyry intrusions and their surrounding rocks. The zircon U–Pb ages of the mineralized diorite porphyry and granodiorite porphyry are 123.1 ± 1.7 Ma (2σ) and 121.5 ± 1.5 Ma (2σ), respectively. The molybdenite Re–Os age is 121.2 ± 1.2 Ma, suggesting that mineralization was closely associated with magmatism. Andesite lava (zircon U–Pb age of 111.7 ± 1.6 Ma, 2σ) overlies the ore‐bodies and is the product of post‐mineralization volcanic activity that played a critical role in preserving the ore‐bodies. Values of ?4.6 ‰ to + 0.8 ‰ δ³⁴S for the metal sulfides (mean ? 1.55 ‰) suggest that S mainly has a deep magmatic source. The H and O isotopic composition is (δD = ?87 ‰ to ?64 ‰; δ¹⁸O_H2O = 5.5 ‰ to 9.0 ‰), indicating that the ore‐forming fluids are mostly magmatic‐hydrothermal, possibly mixed with a small amount of meteoric water. The zircon ε_Hf(t) of the diorite porphyry is 3.7 to 8.3, and the granodiorite porphyry is 1.8 to 7.5. Molybdenite has a high Re from 382.2 × 10^?6 to 1600 × 10^?6. Re and Hf isotope composition show that Tiegelongnan has some mantle source, maybe the juvenile lower crust from crust–mantle mixed source. Metallogenesis of the Tiegelongnan giant porphyry system was associated with intermediate to acidic magma in the Early Cretaceous (~120 Ma). The magma provenance of the Tiegelongnan deposit has some mantle‐derived composition, possibly mixed with the crust‐derived materials.     

Early Cretaceous gold mineralization in the Lesser Xing’an Range of NE China: the Yongxin example

ABSTRACT

The northern Lesser Xing’an Range in NE China hosts many gold deposits. However, genesis and tectonic background for the mineralization remain unclear. The newly discovered Yongxin gold deposit in this region provides a good example for understanding the related issues. Two economic orebodies have been recognized at Yongxin and they are mainly hosted in the hydrothermal breccias. Zircon U–Pb ages of granite porphyry and diorite porphyry are 119.3 ± 0.7 Ma and 119.9 ± 0.6 Ma, respectively. These data provide constraints to the upper limit of ore-forming age. The δ³⁴S values of pyrite from orebodies range from 2.3‰ to 5.1‰. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios of the pyrite are of 18.126–18.255, 15.492–15.537 and 37.880–38.019, respectively. The δ¹⁸O_H2O and δD values of ore-forming fluids range from ?12.5‰ to 1.8‰ and from ?124.8‰ to ?102.1‰, respectively. The REE compositions of gold-bearing pyrite are similar to those of the volcanic rocks of the Longjiang formation, diorite porphyry and granite porphyry. The combined geological, geochronological and geochemical characteristics of the Yongxin gold deposit indicate that the ore-forming materials were likely sourced from the volcanic rocks of the Longjiang formation, diorite porphyry and granite porphyry, whereas the ore-forming fluids are dominated by meteoric water. The Yongxin gold deposit could be a product of the Early Cretaceous large-scale gold mineralization in northeast China which occurred in an extensional tectonic setting and were related to the rollback of the subducted Paleo-Pacific Oceanic Plate beneath the continental margin of northeast China.     

Application of number–size (N-S) fractal model for separation of mineralized zones in Dareh-Ashki gold deposit, Muteh Complex, Central Iran

The goal of this study is to separate different mineralized zones in Dareh-Ashki gold deposit located in Muteh Complex, Central Iran, by using number–size (N-S) fractal model. The N-S log–log plot shows seven geochemical populations and four Au-mineralized zones. Based on obtained results, Au thresholds are 0.17, 0.32, 6.3, and 12.6 ppm which represent weakly, moderately, highly, and extremely mineralized zones in terms of Au grades, respectively. Au values lower than 0.17 ppm illustrate wall rocks. Main mineralization stage of gold commences from 6.3 ppm in this deposit. The moderately mineralized zone with Au values between 0.32 and 6.3 ppm has occupied the biggest part of the studied deposit. However, highly (with Au values between 6.3 and 12.6 ppm) and extremely (higher than 12.6 ppm) mineralized zones have small extension. Correlation between geological model and results from N-S fractal model reveals that the gold mineralized zones specifically the moderately mineralized zone are situated in green schist units.     

Depositional age and tectonic environment of the Gouap banded iron formations from the Nyong group,SW Cameroon:Insights from isotopic,geochemical and geochronological studies of drillcore samples

The discovery of the Gouap banded iron formations(BIFs)-hosted iron mineralization in the northwestern of the Nyong Group(Ntem Complex)in southwestern Cameroon provides unique insights into the geology of this region.In this contribution,we firstly report detailed study of geochemistry,isotopic and geochronology of well preserved samples of the Gouap BIFs collected from diamond drillcores.The Gouap BIFs consist mainly of amphibole BIFs and amphibole-pyrite BIFs characterized by dominant Fe₂O₃+SiO₂contents and variable contents of CaO,MgO and SO₃,consistent with the presence of amphibole,chlorite,epidote and pyrite,formed during amphibolite facies metamorphism and overprinted hydrothermal event.The amphibole–pyrite BIFs are typically enriched in trace and rare earth elements(REE)compared to the amphibole BIFs,suggesting the influence of detrital materials as well as secondary hydrothermal alteration.The Post Archean Australian Shale(PAAS)-normalized REE–Y profiles of the Gouap BIFs display positive La,Eu anomalies,weak negative Ce anomalies,indicating a mixture of low-temperature hydrothermal fluids and relatively oxic conditions probably under relative shallow seawater.We present here the first isotopic data of BIFs within the Ntem Complex.Theδ³⁰Si_NBS28values of the quartz from the Gouap BIFs vary from-1.5‰to-0.3‰and from-0.8‰to-0.9‰for the amphibole BIFs and amphibole–pyrite BIFs,respectively.The quartz hasδ¹⁸OV-SMOW values of 6.8‰–9.5‰(amphibole BIFs)and 9.2‰–10.6‰(amphibole–pyrite BIFs).The magnetite from the Gouap BIFs showsδ¹⁸O values ranging from-3.5‰to-1.8‰and from-3‰to-1.7‰for the amphibole BIFs and amphibole–pyrite BIFs,respectively.Moreover,the pyrite grains in the amphibole–pyrite BIFs displayδ34S values of 1.1‰–1.8‰.All isotopic data of the Gouap BIFs confirm that they might have precipitated from low-temperature hydrothermal fluids with detrital input distant from the volcanic activity.According to their geochemical and isotopic characteristics,we propose that the Gouap BIFs belong to the Superior type.In situ U–Pb zircon dating of BIFs was conducted to assess the BIF depositional age based on strong evidence of zircon in thin section.The Gouap BIFs were probably deposited at 2422±50 Ma in a region where sediments extended from continental shelf to deep-water environments along craton margins like the Caue Formation of the Minas Supergroup,Brazil.The studied BIFs have experienced regional hydrothermal activity and metamorphism at 2089±8.3 Ma during the Eburnean–Transamazonian orogeny.These findings suggest a physical continuity between the protocratonic masses of both Sao Francisco and Congo continents in the Rhyacian Period.     

Lithologic controls on mineralization at the Lagunas Norte high-sulfidation epithermal gold deposit, northern Peru

The 13.1-Moz high-sulfidation epithermal gold deposit of Lagunas Norte, Alto Chicama District, northern Peru, is hosted in weakly metamorphosed quartzites of the Upper Jurassic to Lower Cretaceous Chimú Formation and in overlying Miocene volcanic rocks of dacitic to rhyolitic composition. The Dafne and Josefa diatremes crosscut the quartzites and are interpreted to be sources of the pyroclastic volcanic rocks. Hydrothermal activity was centered on the diatremes and four hydrothermal stages have been defined, three of which introduced Au ± Ag mineralization. The first hydrothermal stage is restricted to the quartzites of the Chimú Formation and is characterized by silice parda, a tan-colored aggregate of quartz-auriferous pyrite–rutile ± digenite infilling fractures and faults, partially replacing silty beds and forming cement of small hydraulic breccia bodies. The δ³⁴S values for pyrite (1.7–2.2?‰) and digenite (2.1?‰) indicate a magmatic source for the sulfur. The second hydrothermal stage resulted in the emplacement of diatremes and the related volcanic rocks. The Dafne diatreme features a relatively impermeable core dominated by milled slate from the Chicama Formation, whereas the Josefa diatreme only contains Chimú Formation quartzite clasts. The third hydrothermal stage introduced the bulk of the mineralization and affected the volcanic rocks, the diatremes, and the Chimú Formation. In the volcanic rocks, classic high-sulfidation epithermal alteration zonation exhibiting vuggy quartz surrounded by a quartz–alunite and a quartz–alunite–kaolinite zone is observed. Company data suggest that gold is present in solid solution or micro inclusions in pyrite. In the quartzite, the alteration is subtle and is manifested by the presence of pyrophyllite or kaolinite in the silty beds, the former resulting from relatively high silica activities in the fluid. In the quartzite, gold mineralization is hosted in a fracture network filled with coarse alunite, auriferous pyrite, and enargite. Alteration and mineralization in the breccias were controlled by permeability, which depends on the type and composition of the matrix, cement, and clast abundance. Coarse alunite from the main mineralization stage in textural equilibrium with pyrite and enargite has δ³⁴S values of 24.8–29.4?‰ and $ {\delta^{18 }}{{\mathrm{O}}_{{\mathrm{S}{{\mathrm{O}}_4}}}} $ values of 6.8–13.9?‰, consistent with H₂S as the dominant sulfur species in the mostly magmatic fluid and constraining the fluid composition to low pH (0–2) and logfO₂ of ?28 to ?30. Alunite–pyrite sulfur isotope thermometry records temperatures of 190–260 °C; the highest temperatures corresponding to samples from near the diatremes. Alunite of the third hydrothermal stage has been dated by ⁴⁰Ar/³⁹Ar at 17.0?±?0.22 Ma. The fourth hydrothermal stage introduced only modest amounts of gold and is characterized by the presence of massive alunite–pyrite in fractures, whereas barite, drusy quartz, and native sulfur were deposited in the volcanic rocks. The $ {\delta^{18 }}{{\mathrm{O}}_{{\mathrm{S}{{\mathrm{O}}_4}}}} $ values of stage IV alunite vary between 11.5 and 11.7?‰ and indicate that the fluid was magmatic, an interpretation also supported by the isotopic composition of barite (δ³⁴S?=?27.1 to 33.8?‰ and $ {\delta^{18 }}{{\mathrm{O}}_{{\mathrm{S}{{\mathrm{O}}_4}}}} $ ?=?8.1 to 12.7?‰). The Δ³⁴S_py–alu isotope thermometry records temperatures of 210 to 280 °C with the highest values concentrated around the Josefa diatreme. The Lagunas Norte deposit was oxidized to a depth of about 80 m below the current surface making exploitation by heap leach methods viable.     

Geochemical characteristics of the Bayan Obo giant REE–Nb–Fe deposit: Constraints on its genesis

Geochemical characteristics of different dolomites in the Bayan Obo giant REE–Nb–Fe deposit in Inner Mongolia have been studied. Intensively REE-mineralized dolomites (total REE over 800 ppm) show similar geochemical characteristics to associated carbonatite dykes, with Ba, Th, REE enrichments and Sr, Nb, Ti, Cu depletions, which is different from those of dolomites in the deposit with low REE contents (total REE less than 800 ppm). The low REE dolomites display some transitional characteristics between carbonatite dyke and sedimentary carbonate, with La depletion and Nb enrichment. This indicates that the genesis of the REE-mineralized dolomites might be related to both carbonatite magma and sedimentary carbonates. Sulfur isotope data indicates two sulfur sources, a mantle source (δ³⁴S c.a. 0‰) and seawater (δ³⁴S c.a. +25‰). It is proposed that mineralized dolomites in the Bayan Obo giant REE–Nb–Fe deposit are the product of sedimentary carbonate hydrothermally metasomatised by carbonatite magma and/or associated fluids. These dolomites formed the large-scale rare earth mineralization in the unique Bayan Obo REE–Nb–Fe deposit.     

Metallogenesis and hydrothermal evolution of the Tonggou Cu deposit in the Eastern Tianshan: Evidence from fluid inclusions,H-O-S isotopes,and Re-Os geochronology

The Tonggou Cu polymetallic deposit in the Bogda Orogenic Belt, Eastern Tianshan shows evidence for three stages of hydrothermal mineralization: early pyrite veins (Stage 1), polymetallic sulfide ± epidote–quartz (Stage 2), and late-stage pyrite–calcite veins (Stage 3). Fluid inclusion petrography and microthermometry analyses indicate that the liquid-rich aqueous inclusions (L), vapour-rich aqueous inclusions (V), and NaCl daughter mineral–bearing three phase inclusions (S) formed during the main stage of mineralization, and that the ore fluids represent high-temperature and high-salinity H₂O-NaCl hydrothermal fluids that underwent boiling. Stable isotope (H, O) data indicate that the ore fluids of the Tonggou deposit were originally derived from magmatic water in Stage 2 and subsequently mixed with local meteoric water during Stage 3. Sulphur isotope compositions (6.7‰ to 10.9‰) are consistent with the δ³⁴S values of pyrite from the Qijiaojing Formation sandstone, indicating the primary source of the sulphur ore. Furthermore, chalcopyrite grains separated from the chalcopyrite-rich ore samples yield an isochron age of 303 ± 12 Ma (MSWD = 1.2). These results indicate that the Tonggou deposit is a transition between high–sulfidation and porphyry deposits which formed in the Late Carboniferous. It also suggests an increased likelihood for the occurrence of Cu (Au, Mo) in the Bogda Orogenic Belt, especially at locations where the Cu-Zn deposits are thicker; further deep drilling and exploration are encouraged in these areas.     

Different mineralization styles in a volcanic-hosted ore deposit: the fluid and isotopic signatures of the Mt Morgan Au–Cu deposit,Australia

Quantitative laser ablation (LA)-ICP-MS analyses of fluid inclusions, trace element chemistry of sulfides, stable isotope (S), and Pb isotopes have been used to discriminate the formation of two contrasting mineralization styles and to evaluate the origin of the Cu and Au at Mt Morgan.The Mt Morgan Au–Cu deposit is hosted by Devonian felsic volcanic rocks that have been intruded by multiple phases of the Mt Morgan Tonalite, a low-K, low-Al₂O₃ tonalite–trondhjemite–dacite (TTD) complex. An early, barren massive sulfide mineralization with stringer veins is conforming to VHMS sub-seafloor replacement processes, whereas the high-grade Au–Cu ore is associated with a later quartz–chalcopyrite–pyrite stockwork mineralization that is related to intrusive phases of the Tonalite complex. LA-ICP-MS fluid inclusion analyses reveal high As (avg. 8850 ppm) and Sb (avg. 140 ppm) for the Au–Cu mineralization and 5 to 10 times higher Cu concentration than in the fluids associated with the massive pyrite mineralization. Overall, the hydrothermal system of Mt Morgan is characterized by low average fluid salinities in both mineralization styles (45–80% seawater salinity) and temperatures of 210 to 270 °C estimated from fluid inclusions. Laser Raman Spectroscopic analysis indicates a consistent and uniform array of CO₂-bearing fluids. Comparison with active submarine hydrothermal vents shows an enrichment of the Mt Morgan fluids in base metals. Therefore, a seawater-dominated fluid is assumed for the barren massive sulfide mineralization, whereas magmatic volatile contributions are implied for the intrusive related mineralization. Condensation of magmatic vapor into a seawater-dominated environment explains the CO₂ occurrence, the low salinities, and the enriched base and precious metal fluid composition that is associated with the Au–Cu mineralization. The sulfur isotope signature of pyrite and chalcopyrite is composed of fractionated Devonian seawater and oxidized magmatic fluids or remobilized sulfur from existing sulfides. Pb isotopes indicate that Au and Cu originated from the Mt Morgan intrusions and a particular volcanic strata that shows elevated Cu background.     

Anatomy of a large Ag–Pb–Zn deposit in the Great Xing'an Range,northeast China: metallogeny associated with Early Cretaceous magmatism

The Bairendaba vein-type Ag–Pb–Zn deposit, hosted in a Carboniferous quartz diorite, is one of the largest polymetallic deposits in the southern Great Xing'an Range. Reserves exceeding 8000 tonnes of Ag and 3 million tonnes of Pb?+?Zn with grades of 30 g/t and 4.5% have been estimated. We identify three distinct mineralization stages in this deposit: a barren pre-ore stage (stage 1), a main-ore stage with economic Ag–Pb–Zn mineralization (stage 2), and a post-ore stage with barren mineralization (stage 3). Stage 1 is characterized by abundant arsenopyrite?+?quartz and minor pyrite. Stage 2 is represented by abundant Fe–Zn–Pb–Ag sulphides and is further subdivided into three substages comprising the calcite–polymetallic sulphide stage (substage 1), the fluorite–polymetallic sulphide stage (substage 2), and the quartz–polymetallic sulphide stage (substage 3). Stage 3 involves an assemblage dominated by calcite with variable pyrite, galena, quartz, fluorite, illite, and chlorite. Fluid inclusion analysis and mineral thermometry indicate that the three stages of mineralization were formed at temperatures of 320–350°C, 200–340°C, and 180–240°C, respectively. Stage 1 early mineralization is characterized by low-salinity fluids (5.86–8.81 wt.% NaCl equiv.) with an isotopic signature of magmatic origin (δ¹⁸O_fluid = 10.45–10.65‰). The main ore minerals of stage 2 precipitated from aqueous–carbonic fluids (4.34–8.81 wt.% NaCl equiv.). The calculated and measured oxygen and hydrogen isotopic compositions of the ore-forming aqueous fluids (δ¹⁸O_fluid = 3.31–8.59‰, δD_fluid?=??132.00‰ to??104.00‰) indicate that they were derived from a magmatic source and mixed with meteoric water. Measured and calculated sulphur isotope compositions of hydrothermal fluids (δ³⁴S_∑S?=??1.2–3.8‰) indicate that the ore sulphur was derived mainly from a magmatic source. The calculated carbon isotope compositions of hydrothermal fluids (δ¹³C_fluid?=??26.52‰ to??25.82‰) suggest a possible contribution of carbon sourced from the basement gneisses. The stage 3 late mineralization is dominated (1.40–8.81 wt.% NaCl equiv.) by aqueous fluids. The fluids show lower δ¹⁸O_fluid (?16.06‰ to??0.70‰) and higher δD_fluid (?90.10‰ to??74.50‰) values, indicating a heated meteoric water signature. The calculated carbon isotope compositions (δ¹³C_fluid?=??12.82‰ to??6.62‰) of the hydrothermal fluids in stage 3 also suggest a possible contribution of gneiss-sourced carbon. The isotopic compositions and fluid chemistry indicate that the ore mineralization in the Bairendaba deposit was related to Early Cretaceous magmatism.     

Proterozoic copper deposits in NW Queensland,Australia: Sulfur isotopic data

Sulfur isotopic disequilibrium is commonly observed between associated pyrite and copper sulfides in NW Queensland. A sulfur isotopic study of copper mineralization in dolomites at Paradise Valley and arenites at Mammoth has allowed the significance of such disequilibrium to be evaluated. Copper mineralization at Paradise Valley is characterized by a greater enrichment in ³⁴S, with δ³⁴S values often greater than +30‰, for both copper sulfides and associated syngenetic/diagneetic pyrite. At Mammoth, copper sulfides have isotopic compositions (δ³⁴S=?15.9 to ?0.3‰) transitional between disseminated syngenetic/diagenetic pyrite (δ³⁴S=?5.7 to ?1.7‰) and epigenetic vein pyrite (δ³⁴S=?17.9 to ?7.1‰) suggesting progressive reaction and replacement of syngenetic/diagenetic pyrite by a copper-bearing mineralizing fluid under oxidizing conditions. The isotopic data, within the constraints imposed by geological and geochemical factors, support a model of reaction between copper-bearing mineralizing fluids and pre-existing syngenetic/diagenetic pyrite for both the carbonate- and arenite-hosted deposits.     

Late Hercynian polymetallic vein-type base-metal mineralization in the Iberian Pyrite Belt: fluid-inclusion and stable-isotope geochemistry (S–O–H–Cl)

Late Variscan vein-type mineralization in the Iberian Pyrite Belt, related to the rejuvenation of pre-existing fractures during late Variscan extensional tectonism, comprises pyrite–chalcopyrite, quartz–galena–sphalerite, quartz–stibnite–arsenopyrite, quartz–pyrite, quartz–cassiterite–scheelite, fluorite–galena–sphalerite–chalcopyrite, and quartz–manganese oxide mineral assemblages. Studies of fluid inclusions in quartz, stibnite, and barite as well as the sulfur isotopic compositions of stibnite, galena, and barite from three occurrences in the central part of the Iberian Pyrite Belt reveal compelling evidence for there having been different sources of sulfur and depositional conditions. Quartz–stibnite mineralization formed at temperatures of about 200 °C from fluids which had undergone two-phase separation during ascent. Antimony and sulfide are most probably derived by alteration of a deeper lying, volcanic-hosted massive sulfide mineralization, as indicated by δ³⁴S signatures from ?1.45 to ?2.74‰. Sub-critical phase separation of the fluid caused extreme fractionation of chlorine isotopes (δ³⁷Cl between ?1.8 and 3.2‰), which correlates with a fractionation of the Cl/Br ratios. The source of another high-salinity fluid trapped in inclusions in late-stage quartz from quartz–stibnite veins remains unclear. By contrast, quartz–galena veins derived sulfide (and metals?) by alteration of a sedimentary source, most likely shale-hosted massive sulfides. The δ³⁴S values in galena from the two study sites vary between ?15.42 and ?19.04‰. Barite which is associated with galena has significantly different δ³⁴S values (?0.2 to 6.44‰) and is assumed to have formed by mixing of the ascending fluids with meteoric water.     

Metallogenesis and ore-forming time of the Changtuxili Mn–Ag–Pb–Zn deposit in Inner Mongolia: Evidence from C–O–S isotopes and U–Pb geochronology

This paper reports new geochronological (U–Pb) and isotope (C, O, and S) data to investigate the timing of mineralization and mode of ore genesis for the recently discovered Changtuxili Mn–Ag–Pb–Zn deposit, located on the western slopes of the southern Great Hinggan Range in NE China. The mineralization is hosted by intermediate–acidic lavas and pyroclastic rocks of the Baiyingaolao Formation. Three stages of mineralization are identified: quartz–pyrite (Stage I), galena–sphalerite–tetrahedrite–rhodochrosite (Stage II), and quartz–pyrite (Stage III). δ¹³C and δ¹⁸O values for carbonate from the ore vary from −8.51‰ to −4.96‰ and 3.97‰ to 15.90‰, respectively, which are indicative of a low-temperature alteration environment. δ³⁴S_V-CDT values of sulfides range from −1.77‰ to 4.16‰ and show a trend of equilibrium fractionation (δ³⁴S_Py ​> ​δ³⁴S_Sp ​> ​δ³⁴S_Gn). These features indicate that pyrite, sphalerite, and galena precipitated during the period of mineralization. The alteration mineral assemblage and isotope data indicate that the weakly acidic to weakly alkaline ore-forming fluid was derived largely from meteoric water and the ore-forming elements C and S originated from magma. During the mineralization, a geochemical barrier was formed by changes in the pH of the ore-forming fluid, leading to the precipitation of rhodochrosite. On the basis of the mineralization characteristics, new isotope data, and comparison with adjacent deposits, we propose that the Changtuxili Mn–Ag–Pb–Zn deposit is an intermediate-to low-sulfidation epithermal deposit whose formation was controlled by fractures and variability in the pH of the ore-forming fluid. The surrounding volcanic rocks yield zircon U–Pb ages of 160−146 ​Ma (Late Jurassic), indicating that the mineralization is younger than 146 ​Ma.     

Geology,Mineralogy, Geochronology,and Sulfur Isotope Constraints on the Genesis of the Luanling Gold Telluride Deposit,Western Henan Province,Central China

The Luanling gold telluride deposit in the Xiong'ershan region is located in the southern margin of the North China Craton. The deposit formed in four stages, that is, an early pyrite‐quartz stage (I), a pyrite‐molybdenite stage (II), a sulfide‐telluride‐gold stage (III), and a late carbonate stage (IV). Six species of telluride in stage (III) are recognized, including hessite, altaite, petzite, unidentified Au‐Ag‐Te mineral, empressite, and unidentified Ag‐Te‐S mineral. Gold occurs mostly as native gold and electrum along the microfractures of sulfides or the contact between sulfide and telluride. The mineralization temperature of stage I and stage III ranges from 296 to 377°C and 241 to 324°C, respectively. Tellurides in stage III precipitate at the log?_S2 from ?14.3 to ?7.3 and log?_Te2 from ?17.4 to ?9.4. The ores were formed in an oxidizing environment. The Re‐Os model ages of molybdenite are 162–164 Ma, which indicate that the main ore formation stage was in the Late Jurassic. The Re contents of five molybdenite samples from the Luanling deposit have a range of 36.32–81.95 ppm, except for one large value of 220 ppm, which indicates that the ore‐forming materials are mainly derived from a crustal‐dominated source. The δ³⁴S values of sulfides range from ?17.6 to ?6.2‰, whereas those of sulfates are from 6.8 to 11.5‰. The δ³⁴S_∑S value of the ore‐forming system is 0.0–3.7‰, indicating that the sulfur of the Luanling deposit derived from a deep igneous source. Mineral association and isotope data of the Luanling deposit, together with its geodynamic setting, imply that this deposit belongs to a part of the metallogenic system of the Nannihu‐Sandaozhuang, Shangfangou porphyry molybdenum deposits, and the Late Jurassic granitic intrusions.     

Gold and antimony metallogenic relations and ore-forming process of Qinglong Sb(Au) deposit in Youjiang basin,SW China: Sulfide trace elements and sulfur isotopes

In the northwestern margin of the Youjiang basin(NWYB)in SW China,many Carlin-like gold deposits are highly antimony(Sb)-rich,and many vein-type Sb deposits contain much Au.These deposits have similar ages,host rocks,ore-forming temperatures,ore-related alterations and ore mineral assemblages,but the Au and Sb metallogenic relations and their ore-forming process remain enigmatic.Here we investigate the large Qinglong Sb deposit in the NWYB,which has extensive sub-economic Au mineralization,and present a new metallogenic model based on in-situ trace elements(EPMA and LA-ICP-MS)and sulfur isotopes(NanoSIMS and fs-LA-MC-ICPMS)of the ore sulfides.At Qinglong,economic Sb ores contain coarse-grained stibnite,jasperoid quartz and fluorite,whilst the sub-economic Au–Sb ores comprise dominantly veined quartz,arsenian pyrite and fine-grained stibnite.Three generations of ore-related pyrite(Py1,Py2 and Py3)and two generations of stibnite(Stb1 and Stb2)are identified based on their texture,chemistry,and sulfur isotopes.The pre-ore Py1 is characterized by the lower ore element(Au,As,Sb,Cu and Ag)contents(mostly below the LA-ICP-MS detection limit)and Co/Ni ratios(average 0.31)than the ore-stage pyrites(Py2 and Py3),implying a sedimentary/diagenetic origin.The Py2 and Py3 have elevated ore element abundance(maximum As=6500 ppm,Au=22 ppm,Sb=6300 ppm,Cu=951 ppm,Ag=77 ppm)and Co/Ni ratios(average 1.84),and have positive As vs.Au–Sb–Cu–Ag correlations.Early-ore Stb1 has lower As(0.12–0.30 wt.%)than late-ore Stb2(0.91–1.20 wt.%).These features show that the progressive As enrichment in ore sulfides is accompanied by increasing Au,Sb,Cu and Ag with the hydrothermal evolution,thereby making As a good proxy for Au.As-rich,As-poor and As-free zones are identified via NanoSIMS mapping of the Au-bearing pyrite.The As-rich zones in the Qinglong Au-bearing pyrites(Py2 and Py3)and ore stibnites(Stb1 and Stb2)have narrowδ³⁴SH₂S ranges(-8.9‰to +4.1‰,average-3.1‰)and-2.9‰to +6.9‰,average + 1.3‰),respectively,indicating that the Au-rich and Sb-rich fluids may have had the same sulfur source.Published in-situ sulfur isotopic data of pyrite As-rich zones from other Carlin-like Au deposits(Shuiyindong,Taipingdong,Nayang,Getang and Lianhuashan)in the NWYB have similar ore-fluidδSH₂S values(-4.5‰to +6.7‰,average-0.6‰)to those of Qinglong.Therefore,we infer that the sulfur of both Au and Sb mineralization was derived from the same magmatic-related source(0±5‰)in the NWYB.Moreover,the core of pyrites(Py1)has variable S isotope fractionation(-18.9‰to +18.1‰,mostly +3‰to +12‰),suggesting that the higher-³⁴S H₂S was produced by bacterial sulfate reduction(BSR).The hydrothermal pyrite(Py2 and Py3)δ³⁴S values gradually decrease with increasing As concentrations,and ultimately,within the restricted range(-5‰to +5‰)in As-rich zones.This variation implies that the As-rich pyrite was formed through ongoing interactions of the magmatic-hydrothermal fluid with pre-existing sedimentary pyrites,causing the progressive decreasing δ³⁴S values with As content increase,Hence,the fluid/mineral interaction may have generated the observed variation in δ³⁴S and As contents.Overall,comparing the Au and Sb deposits in the NWYB,we favor a magmatic-related source for the Au–Sb–As-rich fluids,but the Au-and Sb-ore fluids were likely evolved at separate stages in the ore-forming system.     

Sulphur- and lead-isotope geochemistry of the Arapuçandere lead–zinc–copper deposit,Biga Peninsula,northwest Turkey

The Arapuçandere Pb–Zn–Cu ore body is a typical vein-type lead–zinc deposit of the Biga Peninsula, and is currently being mined for lead and zinc. In the study area, Permian–Triassic metamorphic rocks, Triassic metaclastic and metabasic rocks, Oligocene–Miocene granitoids, Miocene volcanic rocks, and Quaternary terrigenous sediments crop out. The ore deposits developed as Pb–Zn–Cu-bearing veins along faults in Triassic metasandstone and metadiabase. Microscopic studies reveal that the veins contain galena, sphalerite, chalcopyrite, pyrite, marcasite, covellite, and specular hematite as ore minerals, and quartz, calcite, and barite as gangue minerals. Analysed sulphur-isotope compositions (δ³⁴S_VCDT) of galena, sphalerite, and chalcopyrite range from ? 5.9 to ? 1.9‰ (average ? 3.4‰), from ? 5.5 to ? 1.7‰ (average ? 4.2 ‰), and from ? 3.5 to ? 0.9‰ (average ? 2.6‰), respectively; that of H₂S in the hydrothermal fluid was in the calculated range of ? 5.8 to +0.1‰ (average ? 2.5‰). These isotopic values suggest that magmatic sulphur dominates in sulphides, mixed with minor, isotopically light sulphur. Because no contemporaneous magmatic activity is associated with mineralization, it may be assumed that sulphur was leached from the surrounding Triassic units, mainly from metabasic, partly from metaclastic rocks. Lead-isotope studies indicate a model age of 114–63 Ma for the lead reservoir, in accord with possible sulphur-bearing local source rocks. Thus, the sulphur and lead deposited in the studied ore veins were probably leached from Triassic metabasic and metaclastic rocks some time during the Early Cretaceous to the Palaeocene.     

The giant Dexing porphyry Cu–Mo–Au deposit in east China: product of melting of juvenile lower crust in an intracontinental setting

The Dexing porphyry Cu–Mo–Au deposit in east China (1,168 Mt at 0.45 % Cu) is located in the interior of the South China Craton (SCC), made up of two lithospheric blocks, the Yangtze and Cathaysia blocks. The Cu–Mo–Au mineralization is associated with mid-Jurassic granodioritic porphyries with three high-level intrusive centers, controlled by a series of lineaments at the southeastern edge of the Yangtze block. Available age data define a short duration (172–170 Ma) of the felsic magmatism and the mineralization (171?±?1 Ma). The deposit shows broad similarities with deposits in volcanoplutonic arcs, although it was formed in an intracontinental setting. Porphyries associated with mineralization are mainly granodiorites, which contain abundant phenocrysts (40–60 %) and carry contemporaneous microgranular mafic enclaves (MMEs). They are mainly high-K calc-alkaline and show geochemical affinities with adakite, characterized by relatively high MgO, Cr, Ni, Th, and Th/Ce ratios. The least-altered porphyries yielded relatively uniform ε _Nd(t) values from ?0.9 to +0.6, and wide (⁸⁷Sr/⁸⁶Sr)_i range between 0.7046 and 0.7058 partially overlapping with the Sr–Nd isotopic compositions of the MMEs and mid-Jurassic mafic rocks in the SCC. Zircons from the porphyries have positive ε _Hf(t) values (3.4 to 6.9), and low δ¹⁸O values (4.7 to 6.3?‰), generally close to those of depleted mantle. All data suggest an origin by partial melting of a thickened juvenile lower crust involving mantle components (e.g., Neoproterozoic mafic arc magmas), triggered by invasion of contemporaneous mafic melts at Dexing. The MMEs show textural, mineralogical, and chemical evidence for an origin as xenoliths formed by injection of mafic melts into the felsic magmas. These MMEs usually contain magmatic chalcopyrite, and have original, variable contents of Cu (up to 500 ppm). Their geochemical characteristics suggest that they were derived from an enriched mantle source, metasomatized by Proterozoic slab-derived fluids, and supplied a part of Cu, Au, and S for the Dexing porphyry system during their injection into the felsic magmas. The 171?±?1 Ma magmatic-hydrothermal event at Dexing is contemporaneous with the mid-Jurassic extension in the SCC, followed by 160–90 Ma arc-like magmatism in southeastern China. With respect to the tectono-magmatic evolution of the SCC, the emplacement of Cu-bearing porphyries and the associated Cu mineralization occurred in response to the transformation from a tensional regime, related to mid-Jurassic extension, to a transpressional regime, related to the subduction of the Paleo-Pacific oceanic lithosphere.     

Multiple isotope composition (S, Pb, H, O, He, and Ar) and genetic implications for gold deposits in the Jiapigou gold belt, Northeast China

The Jiapigou gold belt (>150 t Au), one of the most important gold-producing districts in China, is located at the northeastern margin of the North China Craton. It is composed of 17 gold deposits with an average grade around 10 g/t Au. The deposits are hosted in Archean gneiss and TTG rocks, and are all in shear zones or fractures of varying orientations and magnitudes. The δ³⁴S values of sulfide from ores are mainly between 2.7?‰ and 10?‰. The Pb isotope characteristics of ore sulfides are different from those of the Archean metamorphic rocks and Mesozoic granites and dikes, and indicate that they have different lead sources. The sulfur and lead isotope compositions imply that the ore-forming materials might originate from multiple, mainly deep sources. Fluid inclusions in pyrite have ³He/⁴He ratios of 0.6 to 2.5 Ra, whereas their ⁴⁰Ar/³⁶Ar ratios range from 1,444 to 9,805, indicating a dominantly mantle fluid with a negligible crustal component. δ¹⁸O values calculated from hydrothermal quartz are between ?0.2?‰ and +5.9?‰, and δD values of the fluids in the fluid inclusions in quartz are from ?70?‰ to ?96?‰. These ranges suggest dominantly magmatic water with a minor meteoric component. The noble gas isotopic data, along with the stable isotopic data, suggest that the ore-forming fluids have a dominantly mantle source with minor crustal addition.     

安徽新桥块状硫化物矿床地球化学特征

新桥块状硫化物矿床发育双层结构,地球化学特征也呈现出明显的“二元性”和垂向变化。下部网脉状蚀变矿化岩石SiO₂、Al₂O₃、K₂O和Na₂O等含量较高,上部层状块状矿石和含矿岩石Fe₂O₃、FeO、CaO、MgO及SiO₂等明显富集。稀土含量相对较低,上部层状块状矿层平均值为10.73×10^-6,下部通道相蚀变矿化岩石平均值为126.1×10^-6。重晶石δ³⁴S值为+16.2‰,硬石膏δ³⁴S值为+11.2‰,黄铁矿δ³⁴S值为+1.5‰～+4.7‰。含矿硅质岩δ¹⁸O为+12.0‰～+13.9‰,下部通道相含黄铁矿石英脉δ¹⁸O值为+13.3‰～+18.6‰。自下部网脉状矿化到上部层状块状矿层,从粗晶细晶到变胶状胶状黄铁矿,δ³⁴S、δ¹⁸O和δ30Si值逐渐降低,²⁰⁶Pb/²⁰⁴Pb、²⁰⁷Pb/²⁰⁴Pb和²⁰⁸Pb/²⁰⁴Pb平均值逐渐增高。     

The Archean komatiite-hosted, PGE-bearing Ni–Cu sulfide deposit at Vaara, eastern Finland: evidence for assimilation of external sulfur and post-depositional desulfurization

Archean komatiites host important resources of Ni, Cu, Co, and PGE, particularly in Western Australia and Canada. In Finland, several small, low-grade sulfide deposits have been found in komatiites, including the ca. 2.8 Ga Vaara deposit in the Archean Suomussalmi greenstone belt. It occurs in the central part of the serpentinized olivine cumulate zone of a komatiitic extrusive body and is composed of disseminated interstitial sulfides consisting of pyrite, pentlandite, millerite, violarite, and chalcopyrite accompanied by abundant magnetite. Although currently subeconomic, the mineralization is interesting due to the very high chalcophile element contents of the sulfide fraction (38 wt% Ni, 3.4 wt% Cu, 0.7 wt% Co, 22.4 ppm Pd, and 9.5 ppm Pt). The sulfides occur in relatively Cr-poor olivine cumulates suggesting involvement of a chromite-undersaturated magma. The parental magma was an Al-undepleted komatiite with an estimated MgO content of at least 24 wt%. In contrast to the common komatiite types in the eastern Finland greenstone belts, the Vaara rocks are moderately enriched in LREE relative to MREE, suggesting that crustal contamination played an important role in the genesis of the Vaara deposit. Multiple sulfur isotope data reveal considerable mass-independent sulfur isotope fractionation both in country rock sedimentary sulfides (Δ³³S ranges from ?0.50 to +2.37?‰) and in the Vaara mineralization (Δ³³S ranges from +0.53 to +0.66?‰), which provides strong evidence for incorporation of crustal sulfur. Extensive replacement of interstitial sulfides by magnetite and the presence of millerite- and violarite-bearing, pyrrhotite-free sulfide assemblages indicate significant post-magmatic, low-temperature hydrothermal oxidation of the primary magmatic pyrrhotite-pentlandite-chalcopyrite assemblages and associated sulfur loss that led to a significant upgrading of the original metal tenors of the Vaara deposit.