Late Sulfide Research Articles

Differences in Sm/Nd ratios between early magmatic and late sulfides: The role of fluids and Nd mobility

Differences in Sm/Nd ratios between early magmatic and late sulfides: The role of fluids and Nd mobility

Genesis of the Shaquanzi Zn–Pb deposit in the Eastern Tianshan, NW China: Constraints from geology, fluid inclusion and isotope geochemistry

The Shaquanzi Zn–Pb deposit, located in the Central Tianshan Terrane, is mainly hosted by siliceous slates and carbonaceous marbles of the Mesoproterozoic Kawabulake Group, and its mineralization / alteration can be divided into skarn period (I: early skarn stage, II: late skarn stage), quartz-sulfide period (III: early sulfide stage, IV: late sulfide stage and V: quartz-calcite stage) and supergene period (VI: supergene alteration stage). The W-type fluid inclusions (FIs) were identified in the garnet, chlorite, quartz, and calcite in skarn and quartz-sulfide periods. Detailed fluid inclusion study shows temperature of fluids decreased from Stage I (510–520 °C) through, Stage III (481–507 °C), Stage IV (248–417 °C, peak at 280–400 °C) to Stage V (148–260 °C, peak at 200–220 °C), with salinities of 20.8–22.2 wt% NaCl eqv., 19.8–29.1 wt% NaCl eqv., 10.6–27.8 wt% NaCl eqv. (peaks at 20–23 wt%), and 21.6–29.9 wt% NaCl eqv. (peak at 23–27 wt%), respectively, indicating that the ore-forming fluids consisted of a high-medium salinity and Na-Mg-Fe-Ca-rich fluid system, and may have evolved from high-medium temperature to medium temperature. The H–O isotopic compositions varied from Stage III (δ18OH2O = 7.7 ‰–9.0 ‰ and δDH2O = − 105 ‰ to − 91 ‰) through Stage IV (δ18OH2O = 2.6 ‰ to 4.3 ‰ and δDH2O = − 114 ‰ to − 111 ‰) to Stage V (δ18OH2O = − 4.2 ‰ to − 3.7 ‰ and δDH2O = − 119 ‰ to − 96 ‰), suggesting that the ore-forming fluid sources may have evolved from magmatic fluids to meteoric water. The average δ34SH2O values of the early sulfide, late sulfide, and quartz-calcite stages are 5.7 ‰, 8.5 ‰ and 14.0 ‰, respectively, indicating that the sulfur in the early stage was mainly derived from magmatic hydrothermal sulfur, while the increase of the δ34SH2O values in the late stages is likely to be sourced from the Kawabulake Group through water–rock reaction. Above all, we propose that the Shaquanzi may have been a skarn-type Zn–Pb deposit.

MOLYBDENUM MINERALIZATION OF THE HANNIVKA DEPOSIT, KRYVYI RIH STRUCTURE

The Hannivka molybdenum deposit is located in the northeastern side of the Kryvyi Rih structure, within the East Hannivka monocline. Molybdenum mineralization is confined to the contact zone of granitoids of the Demuryne complex with metabasites of the Novokryvorizka suite. The main volume of molybdenum mineralization is concentrated in the exocontact, in metabasites, and only 10-15% in endocontact granitoids. The molybdenum-bearing zone is represented by schistose, moderately quartzized and biotitized fine-grained metabasalts, which contain quartz, epidote-quartz, epidote, sometimes feldspar-quartz veins and veinlets and moderate (0.5-3%) sulfide mineralization. The volume of vein material ranges from 0.5% to 3-5%. The geological-morphological type of mineralization is defined as linear stockwork. Leading processes responsible for the development of molybdenite are quartzization and biotitization, namely silicic-alkaline metasomatism. Using JSM-6700F і JXСА-733 electron microscopes, the following ore minerals have been diagnosed and studied: magnetite, ilmenite, molybdenite, loellingite, arsenopyrite, pyrrhotite, pyrite, chalcopyrite, sphalerite. Based on their structural positions and relationships, several successive ore stages have been identified: early oxide (ilmenite-magnetite), main sulfide with molybdenite, potentially gold-bearing arsenide-sulfoarsenide-sulfide and late sulfide. Molybdenite is localized in zalbands of thin (1-3 mm, occasionally up to 2 cm) quartz veinlets, sometimes in the form of boudinaged structures, lenses and pockets reaching sizes up to 4 cm, as well as in host metabasalts and plagiogranites. Conditionally, three morphological types of molybdenite can be distinguished: a) medium-sized elongated tabular, platy, and foliated crystals ranging in size from 0.1 mm to 1.5-2 mm, which are oriented subparallel to the vein structures and rock foliation; b) fine-grained (from 10-20 µm to 0.1 mm) elongated flakes uniformly or randomly oriented; с) isometric crystals of hexagonal-tabular habitus with sizes ranging from 0.1 to 0.7 mm. Outlined are several areas that require further investigation: epitaxial growths of molybdenite and silicates and the conditions of their formation, the time of formation of molybdenite and ore-generating granitoids.

Role of magma differentiation depth in controlling the Au grade of giant porphyry deposits

Porphyry deposits are the world's most important source of Cu and a major source of Au. It has been recognized that low Au grades generally characterize porphyry deposits in thick continental arcs, like the Andes, where the magmas are likely to differentiate at depth. In contrast, Au-rich porphyries are mainly found in thin island arcs, for example, those of the southwest Pacific, or associated with short extensional periods in continental arcs, where the magmas are likely to experience relatively shallow differentiation. However, the key factors that control this difference remain debated. This study shows that the Au grade of giant porphyry deposits and La/Yb ratios of the ore-associated suites are negatively correlated (r=∼0.7, p=10−7). We attribute the negative correlation to be mainly due to varying sulfide saturation histories, modulated by the depth of magma differentiation.Magmas differentiating in deep crustal reservoirs are likely to reach sulfide saturation early due to high pressure and early depletion of FeO (calc-alkaline trend). Early sulfide saturation causes most Au to be held in cumulus sulfides, making it unavailable to enter ore-forming fluid released in the upper crust, resulting in Au-poor porphyry systems. In contrast, magmas evolving in shallow reservoirs are likely to experience late sulfide saturation because of the high sulfur solubility induced by low pressure and the high FeO content of the melts (tholeiitic trend). Late sulfide saturation enhances the potential of a magmatic system to form Au-rich porphyry deposits due to the high Au content of the magma at voluminous fluid saturation and efficient Au transfer from melt to the ore-forming fluids via sulfide-fluid interaction. The link between average magma differentiation depth and Au content is supported by platinum-group element geochemistry of the porphyry ore-forming suites, which shows that the magmas differentiating at shallower depths (lower La/Yb) reach sulfide saturation later and therefore have higher Au concentrations than those that differentiate at deeper levels (higher La/Yb). Numerical models for ore-associated magmas with different sulfide saturation histories indicate that variations in the Au grades of giant porphyry deposits can be explained by the variations in the timing of sulfide saturation. Based on the results, we propose that Au concentration in the magma, modulated by average magma differentiation depth and sulfide saturation history, is one of the critical factors controlling the Au grade of giant porphyry Cu deposits.

Mineral Paragenesis, formation stages and trace elements in sulfides of the Olympiada gold deposit (Yenisei Ridge, Russia)

The mineral sequence and LA-ICP-MS study of the trace-elements distribution in chalcogenides (arsenopyrite, pyrite, pyrrhotite, sphalerite, chalcopyrite, ullmannite, tetrahedrite, berthierite, stibnite, gudmundite, jamesonite) of the Olympiada gold ore deposit (Yenisei Ridge, Russia) are presented. The deposit was formed in three stages, separated by tectonic breaks. Early (I) corresponds to the paragenesis of acicular arsenopyrite + pyrite + pyrrhotite. At the stage of base-metal sulfides (II), the deposition of the bulk of chalcopyrite, sphalerite and galena occurred. Mineral associations of these stages determined the gold-arsenic (Au-As) type of ores. The stage of late sulfides (III) is characterized by the paragenesis of antimony minerals (stibnite + berthierite + gudmundite) and corresponds to the gold-antimony (Au-Sb) ore type. Commercial concentrations of gold were formed at the early sulfides stage in the lattice bonded and nanosize mode in acicular arsenopyrite (12.5–1,512 ppm). The progress of the ore deposition process with the formation of late polymetallic and stibnite-berthierite mineralization led to recrystallization of early sulfides (prismatic arsenopyrite Au ∼ 36.4 ppm → dipyramidal arsenopyrite Au ∼ 0.5 ppm), remobilization and re-deposition of gold in a native form. Pyrite of the deposit does not contain significant amounts of gold (∼0.4 ppm). Silver is absent in early sulfides, but is concentrated in tetrahedrite (348.0–3,811 ppm), jamesonite (0.1–7.7 ppm), berthierite (0.1–2.3 ppm) and stibnite (0.2–2.0 ppm) of the later stage (III). Early sulfides (stage I) are characterized by the As-Au-W-Se-Te geochemical association; polymetallic sulfides (stage II) — by the Cu-Zn-Pb-Cd-In association; and late sulfides (stage III) — by the Sb-Co-Ni-Te-Bi-Pb-Hg-Ag association.

Mineralogy, Geochemistry and Localization of Regional Pyritization Zones – Constraints from Early Mesozoic Deposition in the Chay–Yureya Fault of the Kular-Nera Terrane, NE Russia

The Early Mesozoic clastic rocks the Kular-Nera terrane in the Verkhoyansk-Kolyma orogenic belt, northeast Russia, exhibit regional sulfidation zones. The most abundant mineral of the zones is pyrite. However, its origin (sedimentary-diagenetic, metamorphogenic-hydrothermal, metasomatic) and contribution to the formation of economically important gold deposits remain debatable. The localization of the sulfidation zones is still poorly understood. We have studied geological-structural and mineralogical-geochemical features of pyritization zones in bedrock outcrops on Khara-Yuryakh creek (a right-side tributary of the Nera river) within the Kular-Nera terrane, Verkhoyansk-Kolyma folded area. The pyritization zones are distant from the known gold deposits, and they extend along the Chay-Yureya regional fault. The deformation structure of the clastic rocks of the Chay-Yureya fault is defined by different-aged fold-thrust and strike-slip elements. The early deformations are isoclinal and tight folds up to a few hundred meters wide, with rounded and sharp crests and subhorizontal hinges. The early folds were refolded so that their crests may be seen on the limbs of later folds of the same NW strike. These structures were formed in the conditions of progressive deformation D1 in course of a single continuous (non-stop) tectonic regime during the frontal convergence of the Kolyma-Omolon superterrane with the eastern margin of the Siberian craton. These are commonly inclined or, more rarely, recumbent folds. Also present are late folds associated with dextral and sinistral strike-slip motions on the Chay-Yureya fault. The sulfide mineralization of the Chay-Yureya fault is represented by the disseminated idiomorphic pyrite crystals 1 to 10 mm in size. Metapyrites exhibit a cataclastic microtexture complicated by later corrosion processes. They contain zircon, rutile, and monazite microinclusions entrained in the process of growth. Microinclusions of galena, sphalerite, chalcopyrite, and other late sulfides are confined to defects in the pyrite grains. The chemical composition of pyrite was determined on the Camebax-Micro microanalyzer, using a standard X-ray spectral analysis (DPMGI, SB RAS, Yakutsk). Most of the grains have a stoichiometric composition. 30 percent of the analyses showed excess Fe. Metacrystals of pyrite demonstrate variations in the concentration of trace elements, which often leads to chemical zonality. Our investigations showed that pyritization zones of the rocks are localized in the trans-crustal Chay-Yureya fault which served as a transit path for ascending regional fluid flows. Typomorphic trace elements found in pyrites are Co, Ni, As, Sb, and Cu, with the total amount of 0.1 to 0.4%. They are characterized by the low concentrations and nonuniform distribution. Zonality in the distribution of trace elements is attributable to the poly-

Magmatic fractionation and the magmatic-hydrothermal transition in rare metal granites: Evidence from Argemela (Central Portugal)

Rare Metal Granites (RMGs) are highly evolved intrusions with specific geochemical signatures that are the result of combined magmatic and hydrothermal processes. In most examples, the early evolution is overprinted by late subsolidus transformations and the role of magmatic and magmatic-hydrothermal fractionation processes remains unclear. The origin of fluids involved in magmatic-hydrothermal systems is also an open question. The Argemela RMG (Portugal) is a small subvolcanic intrusion, which exposes in remarkable continuity a sequence of magmatic, magmatic-hydrothermal and early hydrothermal processes. The intrusion comprises a main granitic facies and a border unit made of a complex alternation of aplitic and pegmatitic facies plus three generations of intragranitic veins. The granitic mineral assemblage includes quartz, K-feldspar, albite, muscovite and accessory montebrasite, cassiterite and columbite-tantalite. The whole-rock chemistry is strongly peraluminous, with very high P2O5, Li and F enrichments, elevated rare metal (Sn, Nb, Ta, W) concentrations and strong depletions in Ca, Fe, Ti, Mg. Trace element zonation in minerals, mainly muscovite and quartz, record crystallization/fractionation processes along the magmatic-hydrothermal transition. Three main stages are recognized, magmatic (crystal fractionation and accessory/minor mineral saturation), magmatic-hydrothermal (fluid/melt element partitioning) and early hydrothermal, corresponding to the segregation and collection of magmatic fluids in the intragranitic vein system. Those are followed by limited metasomatic transformations and a late sulphide stage. Stable isotope (O, H) data demonstrate a magmatic origin for the early fluids and a granite-buffered signature for the vein-forming fluids. The fractionation of rare elements (Sn, Nb, Ta, Li, W, Mn, B, Rb, Cs) from the magmatic to the early hydrothermal stage is quantitatively modelled from the combination of three mechanisms, crystal fractionation, magmatic crystallization of accessory/minor phase (MCMA) and fluid/melt partitioning. Sn and W show a markedly contrasted behaviour with Sn precipitated as disseminated mineralization within the intrusion and W partitioned toward the magmatic fluid and extracted from the intrusion. Geochemical trends along the magmatic-hydrothermal transition do not require phases with unusual properties, such as immiscible hydrous melts to be explained and they do not necessarily result in an amplification of initial rare metal melt enrichments. The Argemela RMG stresses the importance of MCMA to generate magmatic rare element pre-concentrations, which later can be hydrothermally redistributed to form large economic deposits.

Genesis of the Bagenheigeqier Pb–Zn skarn deposit in Inner Mongolia, NE China: constraints from fluid inclusions, isotope systematics and geochronology

AbstractMost skarns are found near the pluton or in lithologies containing at least some limestone. However, recent research has shown that neither a pluton nor limestone is necessarily required to form a skarn deposit. The newly discovered Bagenheigeqier Pb–Zn skarn deposit is located in NE China. The skarn and Pb–Zn orebodies occur in volcanic lithologies of the Baiyin’gaolao Formation and are controlled by NE–SW-trending faults. The nearest pluton is a granite porphyry, at a distance of 20–250 m from the orebodies. Five paragenetic stages at Bagenheigeqier are recognized: (I) skarn; (II) oxide; (III) early sulphide; (IV) late sulphide; and (V) late quartz–calcite. The fluid inclusions from stages II to V homogenized at temperatures of 402–452, 360–408, 274–319 and 167–212°C, respectively. The hydrogen and oxygen isotope compositions (δ18OH2O, –12.4‰ to +9.3‰; δDH2O, –156.5‰ to –99.1‰) indicate that the ore-fluids were primarily of magmatic origin, with the proportion of meteoric water increasing during the progression of ore formation. Sulphur isotope values (δ34SVCDT, 1.4–5.5‰), lead isotope values (206Pb/204Pb, 18.184–18.717; 207Pb/204Pb, 15.520–15.875; 208Pb/204Pb, 37.991–38.379) and the initial 187Os/188Os ratios of the pyrite (0.307 ± 0.06) suggest that the ore metals were derived from the granite porphyry and Baiyin’gaolao Formation. Re–Os dating of pyrite intergrown with galena and sphalerite yielded a well-constrained isochron age of 151.2 ± 4.7 Ma, which is coeval with the laser ablation – inductively coupled plasma – mass spectrometry zircon U–Pb age of 154 ± 1 Ma for the granite porphyry. The deposit was therefore formed during Late Jurassic time.

Ore genesis of skarn mineralization in continental collision orogens: A case study from the Pusangguo Co-bearing Cu–Pb–Zn deposit in Tibet

The Gangdese belt in southern Tibet, is renowned for hosting numerous collision-related porphyry Cu-Mo deposits. The recent discovery of Pusangguo Co-bearing Cu–Pb–Zn skarn deposits is the first reported Co-bearing deposit in Gangdese belt as well as in Tibet. Researches on the geological and metallogenic characteristics of Pusanguo indicate that this Co-bearing Cu-Pb-Zn deposit was formed in a collisional setting. We document mineralogy, fluid inclusion studies, and H–O–S–Pb isotope systematics of the skarns and ores of the Pusangguo deposit. Intense endoskarn alteration, dominated by green and pink epidote and quartz, is widely disseminated throughout the host granodiorite as well as in veinlets. Exoskarn alteration is characterized by the presence of prograde grandite (andradite32–100 and grossular0–68) with minor pyroxene (diopside0–46, hedenbergite38–74, and johannsenite1–62). Retrograde epidotes from both the endoskarn and exoskarn show a narrow range of Fe3+/(Fe3+ + Al) ratios (0.25–0.34). Ore minerals include chalcopyrite, sphalerite and galena, with lesser pyrite, pyrrhotite, bornite, Co minerals and falkmanite.Four paragenetic stages of skarn formation and ore deposition are recognized in the Pusangguo Cu–Pb–Zn deposit: prograde (stage I), retrograde (stage II), early sulfide (stage III), and late sulfide (stage IV). Fluid inclusions in all stages are dominated by two-phase liquid-rich (type L) inclusions. During the major phase of mineralization (stage III), fluid inclusions formed at low temperatures (180–240 °C) and with low salinities (0.5–8.6 wt% NaCl equiv.). This is in contrast to other skarn deposits within the Gangdese porphyry copper belt (e.g., the Zhibula, Jiama, and Bangpu deposits) that formed from highly saline fluids at high temperatures. Hydrogen-Oxygen isotopic values obtained from garnet, epidote, quartz and calcite are δDH2O = −179‰ to − 213‰ and δ18OH2O = −9.1‰ to 9.3‰, whereas S-Pb isotopic values for sphalerite, chalcopyrite, pyrite and galena are δ34S = −1.0‰ to 1.2‰, estimated δ34Sfluid = −0.05‰. Such data are indicative of ore-forming fluids and metals that originated from a magmatic–hydrothermal source related to granodiorite emplacement during the Miocene post-continental collision. Extensive mixing between the magmatic-hydrothermal and meteoric fluids led to the co-precipitation of Cu, Pb and Zn minerals from low-salinity fluids at relatively low temperatures. The Pusangguo Co-bearing Cu-Pb-Zn skarn deposit shows consistent features with other (porphyry-related) skarn deposits in the Gangdese belt, except for relatively low temperature and salinity. The research is of great significance for understanding cobalt as an associated mineral in the Gangdese sulfide skarn deposit in Tibet.

Geology, isotope geochemistry, and fluid inclusion investigation of the Robat Zn-Pb-Ba deposit, Malayer-Esfahan metallogenic belt, southwestern Iran

The Robat Zn-Pb-Ba deposit in the Arak mining district in the Malayer-Esfahan metallogenic belt (MEMB) has an estimated reserve of 5 million tonnes (Mt) ore grading 2.1 wt% Zn and 1.4 wt% Pb and 4 Mt barite ore. This deposit, hosted by Early Cretaceous carbonate rocks, formed in an extensional back-arc environment between the Sanandaj-Sirjan Zone and Central Iranian Microcontinent. Sulfide and barite ores display a strong lithological control and form stratabound stacked ore lenses, which are hosted in two horizons by silicified and dolomitized limestone. They are generally best developed below marl layers within intercalated shale, marl, and limestone.The textural and mineralogical data indicate two main stages of sulfide and barite mineralization at the Robat deposit. The first stage comprised deposition of volumetrically minor early fine-grained disseminated sulfides and barite near the seafloor in unconsolidated sediments. Subsequently, sub-seafloor replacement of barite, carbonate, and early sulfide laminae/bands occurred by precipitation of late sulfides and other hydrothermal minerals within the Early Cretaceous limestone-dominant sequence. The minerals in this later stage were deposited in a close relationship with quartz veins.Electron microprobe analyses revealed that sphalerite has a very high Fe content averaging about 1.23 wt% and is relatively enriched in As, Ga, Ge, Cd, Ag, and Bi, which is similar to Irish-type carbonate-hosted deposits. In addition, the Ag content of galena is comparatively low, although concentrations of Ga, Ge, Cd, Zn, and Sb are fairly high. Fluid inclusion microthermometric study of hydrothermal quartz revealed two types of primary two-phase (L + V) fluid inclusions in hydrothermal quartz. Type I fluid inclusions with irregular shapes were recorded along crystal growth zones, whereas type II inclusions are observed as isolated inclusions with relatively regular shapes that are less common than type I. Type I and II inclusions exhibit homogenization temperatures of 140–239 °C and 233–290 °C, with salinities of 2.2–11.8 and 5.5–11.5 wt% NaCl equiv., respectively. Fluid inclusions extracted from quartz displayed δDSMOW between −67‰ and −56‰ and measurements of hydrothermal quartz yielded δ18Ofluid (SMOW) of 12.9‰ to 23.5‰. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of galena samples fell in the ranges of 18.412–18.427, 15.642–15.647, and 38.556–38.580, respectively. The different ratios for the Pb isotopes suggest a dominant continental crust origin for Pb in the ores. Geological, textural, mineralogical, and isotopic data may be cumulatively interpreted to indicate that the Robat carbonate-hosted deposit formed from sub-seafloor replacement like commonly observed for Irish-type base metal deposits.

Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy

We compare three poorly known, historical Ni–Co-bearing hydrothermal deposits in different geological settings in Italy: The Ni–Co–As–Sb–Au-bearing Arburese vein system (SW Sardinia), the Co–Ni–As-rich Usseglio vein system (Piedmont), and the small Cu–Ag–Co–Ni–Pb–Te–Se stockwork at Piazza (Liguria). These deposits share various (mineralogical, chemical, thermal, and stable isotopic) similarities to the Five Element Vein-type ores but only the first two were economic for Co–Ni. The Sardinian Ni-rich veins occur in Paleozoic basement near two Variscan plutons. Like the Co-rich Usseglio vein system, the uneconomic Piazza deposit is hosted in an ophiolite setting anomalous for Co. The Sardinian and Usseglio deposits share a polyphasic assemblage with Ni–Co–As–Sb–Bi followed by Ag-base metal sulfides, in siderite-rich gangue, whereas Piazza shows As-free, Ag–Pb–Te–Se-bearing Co–Ni–Cu sulfides, in prehnite–chlorite gangue. Fluid inclusions indicated Co–Ni arsenide precipitation at ≈170 °C for Usseglio, whereas for the Sardinian system late sulfide deposition occurred within the 52–126 °C range. Ore fluids in both systems are NaCl-CaCl2-bearing basinal brines. The chlorite geothermometer at Piazza provides the range of 200–280 °C for ore deposition from CO2-poor fluids. Enrichments in Se and negative δ13C in carbonates suggest interaction with carbonaceous shales. These deposits involve issues about source rocks, controls on Co/Ni and possible role of arsenic and carbonate components towards economic mineralization.

The granite-hosted Variscan gold deposit from Santo António mine in the Iberian Massif (Penedono, NW Portugal): constraints from mineral chemistry, fluid inclusions, sulfur and noble gases isotopes

The study area is located in the Central Iberian Zone, a major tectonic unit of the Iberian Massif (Variscan belt). In this region the basement is composed of Cambrian-Ordovician sedimentary and minor volcanic rocks that underwent deformation and metamorphism during the Carboniferous. These metamorphic rocks host ca. 331–308 Ma granitic plutons emplaced during the D2 extensional and D3–D4 contractional deformation phases. The gold-bearing quartz veins from the Santo Antonio mine (Penedono region) occur in granite formed at 310.1 ± 1.1 Ma and post-dated the peak of metamorphism. Gold–silver alloy is included in quartz, but mainly occurs in spaces between grains or micro-fractures within arsenopyrite of all three generations and less in pyrite. Late sulphides and sulphosalts were deposited along fractures mainly in arsenopyrite, and locally surrounding the gold–silver alloy grains. Ferberite, scheelite and stolzite replace arsenopyrite. The abundant aqueous carbonic fluids and the occurrence of a low-salinity fluid and their minimum possible entrapment temperature of 360–380 °C suggest that this gold-forming event began during the waning stages of the Variscan orogeny. The mean δ34S values of arsenopyrite and pyrite are − 4.7‰ and − 3.8‰, respectively. He–Ar–Ne isotopic data suggest a crustal origin. The ascent of the granite magma has provided the heat for remobilization of gold, other metals and metalloids from the metamorphic rocks. This gold-arsenopyrite deposit has thus similar characteristics as other selected gold-arsenopyrite deposits from the Iberian Massif, but it contains tungstates.

Trace elements and isotope data of the Um Garayat gold deposit, Wadi Allaqi district, Egypt

Trace element composition of sulfides and O, C, Sr and S isotopic data are assessed to constrain the evolution and potential fluid and metal sources of the Um Garayat gold deposit. Ore microscopy and BSE investigations of quartz veins show blocky arsenopyrite and pyrite replaced in part by pyrrhotite, chalcopyrite, sphalerite, galena, and gersdorffite. Free-milling gold occurs commonly in close association with the late sulfides, and along fractures in pyrite. On the other hand, recrystallized pyrite is disseminated in host metavolcaniclastic/metasedimentary rocks that commonly contain carbonaceous material. In situ LA-ICP-MS analysis of sulfides shows the recrystallized pyrite enriched in most trace elements, while blocky pyrite contains only some traces of arsenic. Detected concentrations of gold (up to 17 ppm) were only reported in arsenopyrite disseminated in quartz veins. The δ34S values of blocky pyrite and pyrrhotite in quartz veins define a narrow range (1.6 to 3.7‰), suggesting a homogenous sulfur source which is consistent with the dominantly mafic host rocks. The recrystallized pyrite has a distinctive sulfur isotope composition (δ34S − 9.3 to − 10.6‰), which is rather comparable to diagenetic sulfides. Hydrothermal carbonate in quartz veins and wallrock have nearly constant values of δ18O (10.5 to 11.9‰) and δ13C (− 4.2 to − 5.5‰). Based on constraints from mineral assemblages and chlorite thermometry, data of six samples indicate that carbonate precipitation occurred at ~ 280 °C from a homogenous hydrothermal fluid with δ18OH2O 4.4 ± 0.7‰ and δ13C = 3.7 ± 0.8‰. Strontium isotope values of two samples (87Sr/86Sr = 0.7024 and 0.7025) are similar to the initial 87Sr/86Sr ratios of island arc metabasalts (~ 710 Ma) in the South Eastern Desert. The generally homogenous sulfur, C, O, Sr isotope data are suggestive of metamorphogenic fluids, likely produced from dominantly mafic volcanic rocks at the greenschist–amphibolite facies transition.

The Berezovsk giant intrusion-related gold-quartz deposit, Urals, Russia: Evidence for multiple magmatic and metamorphic fluid reservoirs

The Berezovsk gold deposit in the Middle Urals has been mined for 270years. Its endowment (past production and gold reserves) is estimated to be 490t of gold. The deposit is located in the greenschist metamorphosed Silurian volcanogenic-sedimentary rocks intruded by granitoid dykes to the north-east of Late Carboniferous Shartash granite massif. Mineralisation is represented by sulphide-quartz veins in the granitoid dykes (“ladder” veins) and in the host rocks (“krassyk” veins) formed in the following four stages: ankerite-quartz, quartz-pyrite, gold-polymetallic and carbonate. Ore veins are accompanied by halos of gumbeite (quartz+orthoclase+carbonate), beresite (quartz+sericite+ankerite+pyrite) and listvenite (quartz+Fe-Mg carbonate+fuchsite+pyrite). The veins mainly consist of quartz with sulphide minerals (commonly 3–5vol%). About 180 minerals have been identified in ores, but the most abundant minerals are quartz, calcite, ankerite, pyrite, galena, tennantite, chalcopyrite, aikinite, native gold, and sphalerite. Native gold was deposited during quartz-pyrite (Au I) and gold-polymetallic (Au II) stages. Fineness of gold ranges from 863 to 984 and from 723 to 848 for Au I and Au II, respectively. The mineral and metal zoning was identified relative to the roof of the Shartash granite massif. The fluid inclusion study revealed that the gold mineralisation at the Berezovsk deposit was formed at 300–230°C and 0.3–2.3kbar (mostly 0.5–1.2kbar), from a H2O-CO2-NaCl fluid with salinity of 7.3–18.2wt% NaCl equiv. The fluid was separated into H2O-CO2-NaCl and CO2-rich fluids due to temperature and/or pressure drop at the deposition site. Calculated δ18O and δD values are 5.2–8.1‰ and −39 to −63‰, respectively, for the fluid in equilibrium with alteration assemblages. The average δ13C value for the fluid equilibrated with carbonates from the inner zones of metasomatic halos is −5.3‰. The calculated δ18O and δ13C values are 3.0–9.6‰ and −3 to −9‰, respectively, for ore-forming fluids. The δ34S values are 1.4–12.9‰ and −1.6 to 11.7‰ for the fluid in equilibrium with early and late sulphides, respectively. In addition to the isotopic data, the geological, mineralogical and fluid inclusion data confirmed the predominant contribution of the magmatic fluid to formation of the Berezovsk hydrothermal system. The light C, O, and S isotope enrichment of the fluid was mainly caused by fluid phase separation. Fluids generated by decarbonation and dehydration reactions due to the contact metamorphism of the host rocks during the Shartash massif emplacement were responsible for additional 34S input. The ore-forming fluid was enriched in the light 16O isotope on the deposit flanks indicating the mixing with heated meteoric water.

Geochemistry of magnetite from theHuanggangskarn iron–tin polymetallic deposit in the southernGreat Xing'an Range, NE China

The Huanggang iron–tin polymetallic skarn deposit is located in the southern Great Xing'an Range. According to the ore types and mineral assemblages, the paragenetic sequence of the Huanggang deposit can be divided into three stages, and these magnetite grains were mainly formed at the retrograde and sulphide skarn stages. The magnetite (sample HG12‐13) from the early retrograde stage is represented by fine‐grained magnetite cutting across coarse‐grained magnetite surrounded by quartz and calcite. The magnetite (sample HG12‐73) from the late retrograde stage is locally replaced by haematite along the margin or interior and is surrounded by calcite. The magnetite (sample HG12‐88) from the early sulphide stage is characterized by obvious core–rim textural features. The magnetite (sample HG‐62) from the late sulphide stage is featured by zone‐like magnetite occurring along the margin and interior of the primary magnetite.Laser ablation inductively coupled plasma mass spectrometry was used to obtain trace element concentrations of magnetite from the different mineralization stages in order to better understand the geochemical variations in the ore‐forming process. Some magnetite grains have abnormally high Mg, Al, K, Cu, Zn, and Sn due to the presence of numerous inclusions (e.g., chlorite, sylvite, chalcopyrite, sphalerite, and cassiterite). In general, magnetite grains from the different mineralization stages demonstrate similar bulk continental crust normalized trace elements patterns, suggesting that they share a similar origin. The increasing Si + Al/Mg + Mn ratios and decreasing Mg + Mn contents for magnetite show an increasing fluid–rock ratio from the retrograde to sulphide stage. Co contents of magnetite decrease abruptly from the retrograde stage to the sulphide stage, whereas Mn contents show the reverse trend, which is affected by minerals coprecipitating with magnetite. A zoned magnetite from the sulphide stage shows decreasing Ti and V contents from core to outer rim; the variation of Ti and V may be related to the temperature or oxygen fugacity. Magnetite compositions from the Huanggang deposit are similar to those from Fe, Cu‐polymetallic, or other skarn deposits, but display more variable compositions than previously presented. Our study demonstrates that the evolution of magnetite in the skarn deposit and trace element of magnetite could be a powerful tool in determining the origin of skarn iron deposit.

Geology, fluid inclusion and isotope geochemistry of the Hongyuan reworked sediment-hosted Zn–Pb deposit: Metallogenic implications for Zn–Pb deposits in the Eastern Tianshan, NW China

The Hongyuan Zn–Pb deposit (ca. 150km southeast of Hami city, Xinjiang) is located in the Central Tianshan Terrane. Discovered in 2009, the deposit is mainly hosted by the Mesoproterozoic Kawabulake Group siliceous slate and carbonaceous marble.Based on the mineral assemblages and their megascopic/microscopic textural relationships, the Hongyuan Zn–Pb mineralization/alteration can be divided into: Sedimentary period (Stage I: Sedimentary), skarn period (Stages II to VI: Early skarn, late skarn, early sulfide, late sulfide and carbonate) and supergene period (Stage VII: Supergene stage).Three types of fluid inclusions (FIs), i.e., aqueous (W-type), CH4-bearing aqueous inclusion (W1-type) and solid-bearing (S-type) inclusions, were identified in the Stages IV to VI quartz, calcite and sphalerite: Stage IV contains W1- and W-type FIs, whereas Stage V contains mainly W-type and rare S-type FIs. Only W-type FIs occur at Stage VI. The Stage IV W-type FIs homogenized at 139–341°C (mainly at 220–240°C), with eutectic temperature of −55 to −30°C and salinities of 2.7–14.4wt.% NaCl eqv. The Stage IV W1-type FIs homogenized at 177–402°C (mainly at 230–380°C), with eutectic temperature of −78 to −55°C and salinities of 3.6–19.6wt.% NaCl eqv. The Stage V W-type FIs homogenized at 115–273°C (mainly at 190–220°C), with eutectic temperature of −61 to −42°C and salinities of 3.6–14.3wt.% NaCl eqv. The Stage VI W-type FIs homogenized at 90–206°C (mainly at 100–160°C), with eutectic temperature of −65 to −33°C and salinities of 3.9–13.1wt.% NaCl eqv. The ore-forming fluids consisted of an initial H2O–NaCl–CaCl2 fluid system, may have evolved from high-medium temperature and medium salinity to medium-low temperature and low salinity.The δ18OH2O and δDH2O of the Stage III fluids are 10.2‰ and −73.8‰, respectively. At Stage IV, the δ18OH2O of quartz ranges from −2.1‰ to 2.7‰; while the δ13CPDB and δ18OSMOW of calcite range from −1.6‰ to −0.2‰ and 3.5‰ to 8.0‰, respectively. At Stage V, the δ18OH2O and δDH2O of quartz range from −3.7‰ to 3.1‰ and −107‰ to −63‰, respectively, while the δ13CPDB and δ18OSMOW of calcite range from 0.1‰ to 0.6‰ and 11.8‰ to 13.5‰, respectively. At Stage VI, the δ18OH2O and δDH2O of quartz range from −8.1‰ to −7.8‰ and −111‰ to −96‰, respectively, while calcite has δ13CPDB and δ18OSMOW of −3.6‰ and 4.1‰, respectively. The H–O–C isotopic compositions at Hongyuan suggest that the ore-forming fluid sources may have changed from magmatic fluids to meteoric water. The sphalerite and pyrite δ34S ranges 16.05–16.80‰, indicating that the sulfur may have been mainly derived from the reduction of Precambrian sulfates. Meanwhile, the Hongyuan sphalerite and galena have Pb isotopic affinities of the ore-hosting Kawabulake Group, suggesting that the lead was mostly derived from the sedimentary host rocks and influenced by magmatic-hydrothermal fluids.We propose that the Hongyuan Zn–Pb mineralization may have initially formed by Mesoproterozoic sedimentary exhalative processes, and was strongly reworked by Late Carboniferous contact metasomatism, whose intensive skarn alteration may have transformed and upgraded the ores. This superimposing mineralization model may also be applicable to other newly-discovered Zn–Pb deposits in the Eastern Tianshan.

Compositions and Pressure–Temperature Conditions of Metamorphic Fluids Overprinting the Talate VMS Pb–Zn Deposit, Southern Altay, China

The Talate Pb–Zn deposit, located in the east of the NW–SE extending Devonian Kelan volcanic‐sedimentary basin of the southern Altaides, occurs in the metamorphic rock series of the upper second lithological section of the lower Devonian lower Kangbutiebao Formation (D1k12). The Pb–Zn orebodies are stratiform and overprinted by late sulfide–quartz veins. Two distinct mineralization periods were identified: a submarine volcanic sedimentary exhalation period and a metamorphic hydrothermal mineralization period. The metamorphic overprinting period can be further divided into two stages: an early stage characterized by bedding‐parallel lentoid quartz veins developed in the chlorite schist and leptite of the ore‐bearing horizon, and a late stage represented by pyrite–chalcopyrite–quartz veins crosscutting chlorite schist and leptite or the massive Pb–Zn ores. Fluid inclusions in the early metamorphic quartz veins are mainly CO2–H2O–NaCl and carbonic (CO2±CH4±N2) inclusions with minor aqueous inclusions. The CO2–H2O–NaCl inclusions have homogenization temperatures of 294–368° C, Tm,CO2 of –62.6 to –60.5°C, Th,CO2 of 7.7 to 29.6°C (homogenized into liquid), and salinities of 5.5–7.4 wt% NaCl eqv. The carbonic inclusions have Tm,CO2 of –60.1 to –58.5°C, and Th, CO2 of –4.2 to 20.6°C. Fluid inclusions in late sulfide quartz veins are also dominated by CO2–H2O–NaCl and CO2±CH4 inclusions. The CO2–H2O–NaCl inclusions have Th,tot of 142 to 360°C, Tm,CO2 of –66.0 to –56.6°C, Th,CO2 of –6.0 to 29.4°C (homogenized into liquid) and salinities of 2.4–16.5 wt% NaCl eqv. The carbonic inclusions have Tm, CO2 of –61.5 to –57.3°C, and Th, CO2 of –27.0 to 28.7°C. The aqueous inclusions (L‐V) have Tm,ice of –9.8 to –1.3°C and Th,tot of 205 to 412°C. The P–T trapping conditions of CO2‐rich fluid inclusions (100–370 MPa, 250–368°C) are comparable with the late‐ to post‐regional metamorphism conditions. The CO2‐rich fluids, possibly derived from regional metamorphism, were involved in the reworking and metal enrichment of the primary ores. Based on these results, the Talate Pb–Zn deposit is classified as a VMS deposit modified by metamorphic fluids. The massive Pb–Zn ores with banded and breccia structures were developed in the early period of submarine volcanic sedimentary exhalation associated with an extensional subduction‐related back‐arc basin, and the quartz veins bearing polymetallic sulfides were formed in the late period of metamorphic hydrothermal superimposition related to the Permian–Triassic continental collision.

The effects of composition and temperature on chalcophile and lithophile element partitioning into magmatic sulphides

We develop a comprehensive model to describe trace and minor element partitioning between sulphide liquids and anhydrous silicate liquids of approximately basaltic composition. We are able thereby to account completely for the effects of temperature and sulphide composition on the partitioning of Ag, Cd, Co, Cr, Cu, Ga, Ge, In, Mn, Ni, Pb, Sb, Ti, Tl, V and Zn. The model was developed from partitioning experiments performed in a piston-cylinder apparatus at 1.5 GPa and 1300 to 1700 °C with sulphide compositions covering the quaternary FeSNiSCuS0.5FeO.Partitioning of most elements is a strong function of the oxygen (or FeO) content of the sulphide. This increases linearly with the FeO content of the silicate melt and decreases with Ni content of the sulphide. As expected, lithophile elements partition more strongly into sulphide as its oxygen content increases, while chalcophile elements enter sulphide less readily with increasing oxygen. We parameterised the effects by using the ε-model of non-ideal interactions in metallic liquids. The resulting equation for partition coefficient of an element M between sulphide and silicate liquids can be expressed aslog⁡DM sulph /sil=A+BT−n2log⁡[FeO]corr+1673T[εMSn/2FeOlog⁡(1−xFeO)+εMSn/2NiSlog⁡(1−xNiS)+εMSn/2CuS0.5log⁡(1−xCuS0.5)] where A is a constant related to the entropy change of the partitioning reaction, B is a constant related to its enthalpy and n is the valency of the element of interest. Interaction parameters εFeO, εNiS and εCuS0.5 refer to non-ideal interactions between trace element and matrix, xFeO, xNiS, xCuS0.5 and xFeS are mole fractions of FeO, NiS, and CuS0.5 in sulphide and FeOcorr is FeO content of silicate liquid (wt%) corrected for the ideal activity of FeS in the sulphide as follows:[FeO]corrected=[FeO]silicate[Fe/(Fe+Ni+Cu)]sulph We find, for most elements, that the effect of Ni and Cu on partitioning is significantly smaller than the effect of oxygen. The effects of temperature are greatest for Ni, Cu and Ag.We used our model to calculate the amount of sulphide liquid precipitated along the liquid line of descent of MORB melts and find that 70% of silicate crystallisation is accompanied by ∼0.23% of sulphide precipitation. The latter is sufficient to control the melt concentrations of chalcophile elements such as Cu, Ag and Pb. Our partition coefficients and observed chalcophile element concentrations in MORB glasses were used to estimate sulphur solubility in MORB liquids. We obtained between ∼800 ppm (for primitive MORB) and ∼2000 ppm (for evolved MORB), values in reasonable agreement with experimentally-derived models. The experimental data also enable us to reconsider Ce/Pb and Nd/Pb ratios in MORB. We find that constant Ce/Pb and Nd/Pb ratios of 25 and 20, respectively, can be achieved during fractional crystallisation of magmas generated by 10% melting of depleted mantle provided the latter contains >100 ppm S and about 650 ppm Ce, 550 ppm Nd and 27.5 ppb Pb.Finally, we investigated the hypothesis that the pattern of chalcophile element abundances in the mantle was established by segregation of a late sulphide matte. Taking the elements Cu, Ag, Pb and Zn as examples we find that the Pb/Zn and Cu/Ag ratios of the mantle can, in principle, be explained by segregation of ∼0.4% sulphide matte to the core.

The Role of Late Sulfide Saturation in the Formation of a Cu- and Au-rich Magma: Insights from the Platinum Group Element Geochemistry of Niuatahi-Motutahi Lavas, Tonga Rear Arc

This research was supported by an Australian Research Council Discovery grant to Ian Campbell and a fund from the Ministry of Oceans and Fisheries of Korea (PM57580). Three-month stipend for Jung-Woo Park was supported by Australian Research Council grant to Oliver Nebel in 2012.

Neotectonic stage in the formation of the Khokhlovskoe uranium deposit, eastern Transural region: Structural, hydrochemical, mineralogical, and geochemical formation conditions

The structural, hydrochemical, mineralogical, and geochemical features of the Khokhlovskoe uranium deposit related to neotectonic processes are considered. The structural feature is expressed in neotectonic dislocations in the form of overall intense fragmentation of host rocks and widespread low-amplitude strike-slip faulting. The hydrochemical specificity is determined by the appearance of thermal carbonated formation water in ore-bearing aquifers. This water is similar in chemical and gas composition to hydrothermal solutions in fluid inclusions and mineral waters abundant in this district. The mineralogical and geochemical features comprise the occurrence of newly formed ferroan carbonates and late iron hydroxides in altered (bleached) pelitic rocks; the formation of silicic opal segregations in ore-bearing sand and sandstone; late sulfides, arsenides, and selenides of iron and other metals; and multiphase gel-pitchblende enriched in Zr especially typical of high-grade uranium ore. The age of high-grade ore determined by a precision uranium-ionium method coincides with the time when thermal carbonated water appeared in the host rocks. This time was estimated from a mathematical model of heat transfer and regional dynamics of underground water. This coincidence clearly indicates that the aforementioned processes are related to the late Quaternary neotectonic reactivation of the eastern Transural region.