Mineralogy and mineral chemistry of Bi-minerals: Constraints on ore genesis of the Beiya giant porphyry-skarn gold deposit,southwestern China

The Beiya deposit, located in the Sanjiang Tethyan tectonic domain (SW China), is the third largest Au deposit in China (323 t Au @ 2.47 g/t). As a porphyry-skarn deposit, Beiya is related to Cenozoic (Himalayan) alkaline porphyries. Abundant Bi-minerals have been recognized from both the porphyry- and skarn- ores, comprising bismuthinite, Bi–Cu sulfosalts (emplectite, wittichenite), Bi–Pb sulfosalts (galenobismutite, cosalite), Bi–Ag sulfosalt (matildite), Bi–Cu–Pb sulfosalts (bismuthinite derivatives), Bi–Pb–Ag sulfosalts (lillianite homologs, galena-matildite series), and Bi chalcogenides (tsumoite, the unnamed Bi₂Te, the unnamed Ag₄Bi₃Te₃, tetradymite, and the unnamed (Bi, Pb)₃(Te, S)₄). Native bismuth and maldonite are also found in the skarn ores. The arsenopyrite geothermometer reveals that the porphyry Au mineralization took place at temperatures in the range of 350–450 °C and at log fS₂ in the range of − 8.0 to − 5.5, respectively. In contrast, the Beiya Bi-mineral assemblages indicate that the skarn ore-forming fluids had minimum temperatures of 230–175 °C (prevailing temperatures exceeding 271 °C) and fluctuating fS₂–fTe₂ conditions. We also model a prolonged skarn Au mineralization history at Beiya, including at least two episodes of Bi melts scavenging Au. We thus suggest that this process was among the most effective Au-enrichment mechanisms at Beiya.     

Mineralogy and trace element geochemistry of sulfide minerals from the Wocan Hydrothermal Field on the slow-spreading Carlsberg Ridge,Indian Ocean

The basalt-hosted Wocan Hydrothermal Field (WHF), located on the NW slope of an axial volcanic ridge at a depth of ∼3000 m at 6°22′N on the slow-spreading Carlsberg Ridge, northwest Indian Ocean, was discovered in 2013 during Chinese DY28th cruise. Preliminary investigations show that the field consists of two hydrothermal sites: Wocan-1, which shows indications for recent high-temperature hydrothermal activity, is located near the peak of the axial volcanic ridge at a water depth of 2970–2990 m, and Wocan-2 site, located at a water depth of 3100 m, ∼1.7 km to the northwest of Wocan-1. The recovered hydrothermal precipitates can be classified into four groups: (i) Cu-rich chimneys; (ii) Cu-rich massive sulfides; (iii) Fe-rich massive sulfides; and (iv) silicified massive sulfides. We conducted mineral texture and assemblage observation and Laser-ablation ICP-MS analyses of the hydrothermal precipitates to study the mineralization processes. Our results show that there are distinct systematic trace element distributions throughout the different minerals in the four sample groups. In general, chalcopyrite from the group (i) is enriched in Pb, As, Mo, Ga, Ge, V, and Sb, metals that are commonly referred to as medium- to low-temperature elements. In contrast these elements are present in low contents in the chalcopyrite grains from other sample groups. Selenium, a typical high-temperature metal, is enriched in chalcopyrite from groups (ii) and (iv), whereas Ag and Sn are enriched only in some silicified massive sulfides. As with chalcopyrite, pyrite also shows distinct trace element associations in grains with different habitus. The low-temperature association of elements (Pb, Mo, Mn, U, Mg, Ag, and Tl) is typically present in colloform/framboidal pyrite, whereas the high-temperature association (Se, Co, and Bi) is enriched in euhedral pyrite. Sphalerite in the groups (i) and (iii) at Wocan-1 is characterized by high concentrations of Ga, Ge, Pb, Cd, As, and Sb, indicating that sphalerite in these sample groups likely precipitated at intermediate temperatures. Early bornite, which mainly occurs in the central part of the Cu-rich chimney, is typically enriched in Sn and In compared to the other minerals. In contrast, late bornite that likely formed during increasing interaction of hydrothermal fluids with cold, oxygenated seawater has low Sn and In, but significantly higher concentrations of Ag, Au, Mo and U. Digenite, also forming in the exterior parts of the samples during the late stages of hydrothermal fluid venting, is poor in most trace elements, except Ag and U. The notable Ag enrichment in the late-stage mineral assemblages at both Wocan-1 and Wocan-2 may therefore be related to lower temperatures and elevated pH. Our results indicate that Wocan-1 has experienced a cycle of heating with Cu-rich chimney growth and subsequent cooling, followed by late seafloor weathering, while Wocan-2 has seen intermediate- to high-temperature mineralization followed by intense silicification of sulfides. Seafloor weathering processes or mixing of hydrothermal fluids with seawater during the waning stages of hydrothermal fluid flow result in significant redistributions of trace elements in sulfide minerals.     

Trace metal nanoparticles in pyrite

Hydrothermal pyrite contains significant amounts of minor and trace elements including As, Pb, Sb, Bi, Cu, Co, Ni, Zn, Au, Ag, Se and Te, which can be incorporated into nanoparticles (NPs). NP-bearing pyrite is most common in hydrothermal ore deposits that contain a wide range of trace elements, especially deposits that formed at low temperatures. In this study, we have characterized the chemical composition and structure of these NPs and their host pyrite with high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), analytical electron microscopy (AEM), and electron microprobe analysis (EMPA). Pyrite containing the NPs comes from two types of common low-temperature deposits, Carlin-type (Lone Tree, Screamer, Deep Star (Nevada, USA)), and epithermal (Pueblo Viejo (Dominican Republic) and Porgera (Papua New-Guinea)).EMPA analyses of the pyrite show maximum concentrations of As (11.2), Ni (3.04), Cu (2.99), Sb (2.24), Pb (0.99), Co (0.58), Se (0.2), Au (0.19), Hg (0.19), Ag (0.16), Zn (0.04), and Te (0.04) (in wt.%). Three types of pyrite have been investigated: “pure” or “barren” pyrite, Cu-rich pyrite and As-rich pyrite. Arsenic in pyrite from Carlin-type deposits and the Porgera epithermal deposit is negatively correlated with S, whereas some (colloform) pyrite from Pueblo Viejo shows a negative correlation between As + Cu and Fe. HRTEM observations and SAED patterns confirm that almost all NPs are crystalline and that their size varies from 5 to 100 nm (except for NPs of galena, which have diameters of up to 500 nm). NPs can be divided into three groups on the basis of their chemical composition: (i) native metals: Au, Ag, Ag–Au (electrum); (ii) sulfides and sulfosalts: PbS (galena), HgS (cinnabar), Pb–Sb–S, Ag–Pb–S, Pb–Ag–Sb–S, Pb–Sb–Bi–Ag–Te–S, Pb–Te–Sb–Au–Ag–Bi–S, Cu–Fe–S NPs, and Au–Ag–As–Ni–S; and (iii) Fe-bearing NPs: Fe–As–Ag–Ni–S, Fe–As–Sb–Pb–Ni–Au–S, all of which are in a matrix of distorted and polycrystalline pyrite. TEM-EDX spectra collected from the NPs and pyrite matrix document preferential partitioning of trace metals including Pb, Bi, Sb, Au, Ag, Ni, Te, and As into the NPs. The NPs formed due to exsolution from the pyrite matrix, most commonly for NPs less than 10 nm in size, and direct precipitation from the hydrothermal fluid and deposition into the growing pyrite, most commonly for those > 20 nm in size. NPs containing numerous heavy metals are likely to be found in pyrite and/or other sulfides in various hydrothermal, diagenetic and groundwater systems dominated by reducing conditions.     

Sulfidic and non-sulfidic indium mineralization of the epithermal Au–Cu–Zn–Pb–Ag deposit San Roque (Provincia Rio Negro,SE Argentina) — with special reference to the “indium window” in zinc sulfide

At San Roque in Patagonia's Rio Negro Province, Argentina, an In–Au–Cu–Zn–Pb–Ag mineralization (< 0.24 wt.% In, < 7 ppm Au, < 0.45 wt.% Cu, < 14.1 wt.% Zn, < 0.55 wt.% Pb, < 60 ppm Ag) is bound to lava, and volcaniclastics of Triassic through Jurassic age. The polymetallic sulfidic and non-sulfidic indium mineralization is attributed to the low-sulfidation (LS) to intermediate sulfidation (IS) epithermal type of mineralization. Its vein-type and stockwork mineralization developed at 39.2 bars under hydrostatic conditions, corresponding to a depth of 400 m below the water level of the paleoaquifer. In the redox-controlled hypogene mineralization, the temperature increased from 130 °C up to as much as 250 °C at depth, while the pH regime changed from slightly acidic near surface to more alkaline conditions around pH 8 at a depth of approximately 150 m. The monophase mineral associations composed of sphalerite, Ag–Bi-enriched and inclusion-free galena (< 1.7 wt.% Ag, < 3.7 wt.% Bi), chalcopyrite, pyrite, gold, silver, digenite, various In–Cu- and Pb–Zn–Ag “intermediate products”, wittichenite, roquesite, sakuraiite, dzhalindite, brochantite, antlerite, cerussite, and “manganomelane” in a quartz and muscovite-rich gangue have been subdivided into three different stages: (1) Stockwork mineralization of LS to IS epithermal type (hypogene), (2) quartz vein mineralization (hypogene), and (3) salar mineralization (supergene–hypogene).Salt–mud flats controlled the youngest mineralization with Mn, Li, Ca, Mg, V, Sr, Cu, Ag and In bound to oxides, hydroxides, sulfates and subordinate carbonates. The quartz vein mineralization is made up of oxides, hydroxides prevailing over sulfides and containing W, Fe, Au, As, Pb, In, and Cu. It formed at the passage from the vadose into the phreatic zones under oxidizing to slightly reducing conditions. The level marks the boiling level of the hydrothermal solutions involved in the mineralizing process. The hypogene stockwork mineralization is exclusively made up of sulfides containing Zn, Pb, Cu, In, Ag and Bi in the phreatic zones. It developed under reducing conditions. Indium is present at all levels within the volcanic rocks and has been derived from sphalerite rich in Cd (< 1.6 wt.% Cd), In (< 7.3 wt.% In) and Cu (< 7.2 wt.% Cu) while the Fe contents are moderate in sphalerite (< 6.8 wt.% Fe). Indium reached economic grade only through the segregation of a Cu–In–S phase in the “indium window” which is defined by a Cd content of sphalerite in the range 0.2–0.6 wt.% Cd. This concentration of In is controlled by the crystal morphology and the lattice parameters of the minerals involved. It is described as a two-stage process with interdiffusion processes in an Fe-enriched system (stage I) and zoned replacement in an Fe-poor system enriched in indium (stage II). Cu-bearing sphalerite decomposed into sphalerite poor in trace elements and into Cu–In-bearing sphalerite. Further indium concentration took place, when roquesite and sakuraiite decomposed along with an increase in oxygen pressure under hypogene and supergene conditions into dzhalindite. The physical–chemical conditions of the mineralogy and chemical changes in the system In–Cu–Zn–Cd observed in nature have been approximated based upon the results obtained during laboratory studies in material sciences that were focused on solar energy.     

Massive sulfides of Mount Jourdanne along the super-slow spreading Southwest Indian Ridge and their genesis

Modern massive sulfide deposits are known to occur in diverse tectonic settings and it is generally expected that hydrothermal deposits of similar geological settings shall have more or less similar mineralogical and geochemical signatures. However, the Mount Jourdanne sulfide deposits along the super-slow spreading Southwest Indian Ridge deviate from this common concept. These sulfide precipitates are Zn-rich (up to 35 wt.%) and are characterized by high concentrations of Pb (≤ 3.5 wt.%), As (≤ 1.1 wt.%), Ag (≤ 0.12 wt.%), Au (≤ 11 ppm), Sb (≤ 967 ppm), and Cd (≤ 0.2 wt.%) which are unusual for a modern sediment-free mid-oceanic ridge system. Therefore, we have reinvestigated the sulfide samples collected during the INDOYO cruise in 1998, in order to explain their unusual mineralogy and geochemical composition. The sulfide samples are polymetallic and are classified as: a) chimneys, b) mounds, and c) hydrothermal breccias. The chimneys are small tube-like symmetrical bodies (30–40 cm high; ~ 10 cm diameter) and consist mainly of sphalerite and less chalcopyrite, set in a matrix of late amorphous silica. The inner wall shows a late-stage colloform sphalerite containing co-precipitates of galena and/or Pb–As sulfosalts. In contrast, the mound samples are dominated either by Fe-sulfides (pyrite) or by a mixture of pyrite and chalcopyrite with less sphalerite, pyrrhotite, amorphous silica and barite. Both, the chimney and mound samples, are characterized by layering and mineral zonation. The hydrothermal breccias are highly altered and mineralogically heterogeneous. They consist of silicified basaltic material that are impregnated with sulfides and contain cm-sized chimney fragments within a matrix of low-temperature minerals such as sphalerite and pyrite. The latter fragments mainly consist of chalcopyrite with isocubanite lamellae. In addition, these breccias contain late-stage realgar, boulangerite, galena, Pb–As sulfosalts and barite that are mostly confined to vugs or fractures. At least five mineralogical associations are distinguished that indicate different thermal episodes ranging from black smoker mineralization conditions to cessation of the hydrothermal activity. Based on the mineralogical associations and established literature in this regard, it is inferred that the mineralization at Mt. Jourdanne occurred mainly in three temperature domains. Above 300 °C, the chalcopyrite (with isocubanite)–pyrrhotite association formed whereas the sphalerite dominated assemblage with much less chalcopyrite and pyrite formed around and below 300 °C. The late-stage mineralization (below 200 °C) contains colloform sphalerite, galena, Pb–As sulfosalts, realgar and barite. The unusual mineralogy and trace element chemistry for this modern VHMS deposit could be explained assuming hydrothermal leaching of some felsic differentiates underneath the basaltic cover and subsequent zone refining processes.     

Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate

Toxic metalliferous mine-tailings pose a significant health risk to ecosystems and neighboring communities from wind and water dispersion of particulates containing high concentrations of toxic metal(loid)s (e.g., Pb, As, Zn). Tailings are particularly vulnerable to erosion before vegetative cover can be reestablished, i.e., decades or longer in semi-arid environments without intervention. Metal(loid) speciation, linked directly to bioaccessibility and lability, is controlled by mineral weathering and is a key consideration when assessing human and environmental health risks associated with mine sites. At the semi-arid Iron King Mine and Humboldt Smelter Superfund site in central Arizona, the mineral assemblage of the top 2 m of tailings has been previously characterized. A distinct redox gradient was observed in the top 0.5 m of the tailings and the mineral assemblage indicates progressive transformation of ferrous iron sulfides to ferrihydrite and gypsum, which, in turn weather to form schwertmannite and then jarosite accompanied by a progressive decrease in pH (7.3–2.3).Within the geochemical context of this reaction front, we examined enriched toxic metal(loid)s As, Pb, and Zn with surficial concentrations 41.1, 10.7, 39.3 mmol kg⁻¹ (3080, 2200, and 2570 mg kg⁻¹), respectively. The highest bulk concentrations of As and Zn occur at the redox boundary representing a 1.7 and 4.2-fold enrichment relative to surficial concentrations, respectively, indicating the translocation of toxic elements from the gossan zone to either the underlying redox boundary or the surface crust. Metal speciation was also examined as a function of depth using X-ray absorption spectroscopy (XAS). The deepest sample (180 cm) contains sulfides (e.g., pyrite, arsenopyrite, galena, and sphalerite). Samples from the redox transition zone (25–54 cm) contain a mixture of sulfides, carbonates (siderite, ankerite, cerrusite, and smithsonite) and metal(loid)s sorbed to neoformed secondary Fe phases, principally ferrihydrite. In surface samples (0–35 cm), metal(loid)s are found as sorbed species or incorporated into secondary Fe hydroxysulfate phases, such as schwertmannite and jarosites. Metal-bearing efflorescent salts (e.g., ZnSO₄·nH₂O) were detected in the surficial sample. Taken together, these data suggest the bioaccessibility and lability of metal(loid)s are altered by mineral weathering, which results in both the downward migration of metal(loid)s to the redox boundary, as well as the precipitation of metal salts at the surface.     

Metamorphosed Pb–Zn–(Ag) ores of the Keketale VMS deposit,NW China: Evidence from ore textures,fluid inclusions,geochronology and pyrite compositions

The Keketale Pb–Zn deposit is located in the Devonian volcanic-sedimentary Maizi basin of the Altay orogenic belt. The mineralization at Keketale is hosted in marbles and deformed volcanic tuffs and biotite–garnet–chlorite schists, folded into a series of overturned synclines formed in multiple deformation events. Keketale contains economic amounts of Pb (0.89 Mt @ 1.51 wt.%), Zn (1.94 Mt @ 3.16 wt.%) and Ag (650 t @ 40 g/t).Detailed petrographic studies have defined two main generations of sulfide development. The banded pyrite of the early Stage A is commonly stratiform, with minor galena, sphalerite and chalcopyrite. Stage B is characterized by a large amount of polymetallic sulfides including pyrrhotite, chalcopyrite, sphalerite and galena, with minor pyrite hosted in quartz veins.Three types of fluid inclusions (FIs), including mixed carbonic-aqueous (C-type), pure carbonic (PC-type) and aqueous (W-type), have been recognized in quartz of stage B. The C-type FIs have homogenization temperatures of 150–326 °C and salinities of 0.2–16.6 wt.% NaCl equivalent. The PC-type FIs are dominated by CO₂ with minor CH₄ and N₂ and have initial ice-melting temperatures of − 57.5 to − 56.7 °C, CO₂ homogenization temperatures of 11–14.1 °C. The W-type primary FIs were completely homogenized at temperatures of 124–359 °C with salinities of 5.0–14.6 wt.% NaCl equivalent. Such CO₂-rich fluid inclusions are consistent with those discovered in orogenic-type deposits in the Altay area and elsewhere.Muscovite separates from the polymetallic quartz veinlets of stage B yield a well-defined ⁴⁰Ar/³⁹Ar isotopic plateau age of 259.33 ± 2.56 Ma, with an isochron age of 259.62 ± 2.65 Ma. This age is coeval with the closure of the Paleo-Asia Ocean and reactivation of the Ertix Fault system.LA-ICP-MS analyses of two generations of pyrite indicate that the banded pyrite of stage A is relatively depleted in metallic elements and contains low contents of Cu (0.39 ppm), Ag (0.20 ppm), Au (below the detection limits), Pb (17.43 ppm) and Zn (14.38 ppm); whereas the pyrite in quartz–polymetallic sulfide veinlets of the stage B is relatively rich in metallic elements, e.g., Cu (2.56 ppm), Ag (3.07 ppm), Au (0.01 ppm), Pb (1047 ppm) and Zn (1136 ppm). The trace amounts of Cu, Pb, Zn, Au and Ag are interpreted to have been initially locked in the lattice of type-A pyrite, and then liberated and precipitated as micromineral inclusions with type-B pyrite during subsequent metamorphism and deformation.Two key factors are considered vital to the formation of economic ores of the Keketale Pb–Zn deposit, namely the original Devonian banded pyrite formed in a VMS system and subsequent Permian deformation and metamorphic processes that liberated Cu, Pb, Zn, Au and Ag from the lattice of type-A pyrite to form galena, sphalerite and chalcopyrite with minor muscovite in quartz veinlets. The model provides a new interpretation of VMS Pb–Zn deposit occurring in back-arc basin environments followed by collision, and new insights into the unique regional Fe–Cu–Pb–Zn–Au mineralization in the Altay orogenic belt.     

The geochemistry, mineralogy and maturity of gossans derived from volcanogenic Zn–Pb–Cu deposits of the eastern Lachlan Fold Belt, NSW, Australia

The Eastern Highlands of Australia have probably been in existence since the Late Cretaceous or earlier and so there has been ample time for mature gossan profiles to form over outcropping volcanogenic Zn–Pb–Cu mineralisation in the eastern Lachlan Fold Belt. The mature gossan profiles are characterised by the upward progression from supergene sulfides to secondary sulfates, carbonates and phosphates into a Fe-oxide dominated surficial capping which may contain boxwork textures after the original sulfides (as at the Woodlawn massive sulfide deposit). However, the region has locally been subjected to severe erosion and the weathering profile over many deposits is incomplete (immature) with carbonate and phosphate minerals, especially malachite, being found in surficial material. These immature gossans contain more Cu, Pb and Zn but lower As, Sn (and probably Au) than the mature gossans. Although Pb is probably the best single pathfinder for Zn–Pb–Cu VHMS deposits of the eastern Lachlan Fold Belt, Ag, As, Au, Bi, Mo, Sb and Sn are also useful, with most of these elements able to be concentrated in substantial amounts in Fe oxides and alunite–jarosite minerals.     

Geochemical and mineralogical haloes about the Elura Zn-Pb-Ag orebody, western New South Wales

The Elura Zn-Pb-Ag deposit, situated 43 km NNW of Cobar, western New South Wales, is hosted by the C.S.A. Siltstone, a distal turbidite sequence. Deep weathering has given rise to a bleached quartz-muscovite-kaolinite rock to a depth of approximately 80 m. Weathered bedrock is mantled by a thin (0.3–2 m) layer of soil and transported overburden which contains thin layers of maghemite-bearing gravels. Outcrop in the area is extremely poor with the insignificant gossan subcrop covered by 0.2 m of soil. The water table is presently at a depth of about 80 m. Groundwater is saline with up to 2.5% total dissolved solids.Oxidation of the orebody has resulted in the formation of a gossan and ferruginization of wall rocks. Elements associated with ore and retained at high concentration in the gossan are Ag, As, Ba, Cu, Hg, Mo, Pb, Sb, (Se) and Sn; much of the Zn has been leached whilst Cd and Tl are below the detection limits. Silver, Cu and Hg have been partially leached and concentrated in the supergene zone. Ferruginous wall rock contains substantial amounts of Pb, As and Ba but other element contents are substantially lower than in the gossan.Secondary dispersion from the Elura orebody is largely restricted to an interpreted paleodrainage channel SW of the orebody and has occurred in two distinct periods. Mobile elements, particularly Zn, leached during gossan formation, occur in anomalous concentrations at or near the water table. More recently, the less mobile elements Pb, As, Bi, Hg and Sb have been leached from mechanically transported fragments of ferruginized wall rock and gossan by the saline groundwaters and occur as anomalies up to 150 m from the gossan in near-surface bedrock. Copper and Zn form broad low-contrast anomalies whilst Sn is retained within the gossan.Iron-rich bands, 50–1200 mm in thickness, which are common in the weathered zone about the Elura orebody, were formed by precipitation from groundwater passing along bedding planes, shears, fractures and cracks. They have higher As, Bi, Co, Cu, Mn, Ni, Zn, lower values of Ba and Sr, and similar Pb, Sb and Sn contents to the weathered siltstones. Iron may be derived from Fe-rich carbonates in the siltstones and be redeposited as goethite and minor hematite. These Fe-rich bands have trapped target and pathfinder elements which are believed to be from primary haloes rather than from the orebody or gossan.A two-stage mechanism for the formation of some secondary minerals within the weathered zone has been confirmed by stable light isotope studies. These studies have also shown that fractionation of S isotopes is minimal during gossan formation, and that a S isotopic halo in weathered bedrock may be used as an exploration tool.     

Ages of sediment-hosted Himalayan Pb–Zn–Cu–Ag polymetallic deposits in the Lanping basin,China: Re–Os geochronology of molybdenite and Sm–Nd dating of calcite

The Lanping basin is a significant Pb–Zn–Cu–Ag mineralization belt of the Sanjiang Tethyan metallogenic province in China. Over 100 thrust-controlled, sediment-hosted, Himalayan base metal deposits have been discovered in this basin, including the largest sandstone-hosted Pb–Zn deposit in the world (Jinding), and several Cu ± Ag ± Co deposits (Baiyangping, Baiyangchang and Jinman). These deposits, with total reserves of over 16.0 Mt Pb + Zn, 0.6 Mt Cu, and 7000 t Ag, are mainly hosted in Meso-Cenozoic mottled clastic rocks, and strictly controlled by two Cenozoic thrust systems developed in the western and eastern segments of the Lanping basin.To define the metallogenic history of the study area, we dated nine calcite samples associated with copper sulfides from the Jinman Cu deposit by the Sm–Nd method and five molybdenite samples from the Liancheng Cu–Mo deposit by the Re–Os method. The calcite Sm–Nd age for the Jinman deposit (58 ± 5 Ma) and the molybdenite Re–Os age for the Liancheng deposit (48 ± 2 Ma), together with previously published chronological data, demonstrate (1) the Cu–Ag mineralization in the western Lanping basin mainly occurred in three episodes (i.e., ∼56–54, 51–48, and 31–29 Ma), corresponding to the main- and late-collisional stages of the Indo–Asian orogeny; and (2) the Pb–Zn–Ag (±Cu) mineralization in the eastern Lanping basin lacked precise and direct dating, however, the apatite fission track ages of several representative deposits (21 ± 4 Ma to 32 ± 5 Ma) may offer some constraints on the mineralization age.     

The Jabali nonsulfide Zn–Pb–Ag deposit,western Yemen

The Jabali Zn–Pb–Ag deposit is located about 110 km east of Sana'a, the capital of Yemen, along the western border of the Marib-Al-Jawf/Sab'atayn basin. The economic mineralization at Jabali is a nonsulfide deposit, consisting of 8.7 million tons at an average grade of 9.2% zinc, derived from the oxidation of primary sulfides. The rock hosting both primary and secondary ores is a strongly dolomitized carbonate platform limestone of the Jurassic Shuqra Formation (Amran Group). The primary sulfides consist of sphalerite, galena and pyrite/marcasite. Smithsonite is the most abundant economic mineral in the secondary deposit, and is associated with minor hydrozincite, hemimorphite, acanthite and greenockite. Smithsonite occurs as two main generations: smithsonite 1, which replaces both host dolomite and sphalerite, and smithsonite 2, occurring as concretions and vein fillings in the host rock. At the boundary between smithsonite 1 and host dolomite, the latter is widely replaced by broad, irregular bands of Zn-bearing dolomite, where Zn has substituted for Mg. The secondary mineralization evolved through different stages: 1) alteration of original sulfides (sphalerite, pyrite and galena), and release of metals in acid solutions; 2) alteration of dolomite host rock and formation of Zn-bearing dolomite; 3) partial dissolution of dolomite by metal-carrying acid fluids and replacement of dolomite and Zn-bearing dolomite by a first smithsonite phase (smithsonite 1). To this stage also belong the direct replacement of sphalerite and galena by secondary minerals (smithsonite and cerussite); 4) precipitation of a later smithsonite phase (smithsonite 2) in veins and cavities, together with Ag- and Cd-sulfides.The δ¹⁸O composition of Jabali smithsonite is generally lower than in other known supergene smithsonites, whereas the carbon isotope composition is in the same range of the negative δ¹³C values recorded in most supergene nonsulfide ores. Considering that the groundwaters and paleo-groundwaters in this area of Yemen have negative δ¹⁸O values, it can be assumed that the Jabali smithsonite precipitated in different stages from a combination of fluids, possibly consisting of local groundwaters variably mixed with low-temperature hydrothermal waters. The carbon isotope composition is interpreted as a result of mixing between carbon from host rock carbonates and soil/atmospheric CO₂.The most favorable setting for the development of the Jabali secondary deposit could be placed in the early Miocene (~ 17 Ma), when supergene weathering was favored by major uplift and exhumation resulting from the main phase of Red Sea extension. Low-temperature hydrothermal fluids may have also circulated at the same time, through the magmatically-induced geothermal activity in the area.     

Metallogenesis at the Terramonte Pb–Zn–Ag quartz vein,Portugal: Geological,mineralogical and geochemical evidences

The Pb–Zn–Ag quartz vein from Terramonte cuts the Neoproterozoic–Cambrian schist–greywacke complex. This orebody was partially exploited. The paragenetic sequence consists of four stages containing quartz accompanied mainly by arsenopyrite and pyrite in the first stage, sphalerite in the second stage, galena showing many inclusions of several sulphosalts in the third stage and carbonates in the fourth remobilization stage. Several sulphide and sulphosalt grains are oscillatory zoned. The chemical distinction between lighter and darker zones in backscattered images of arsenopyrite, pyrite, sphalerite and freibergite is due to substitutions in the mineral lattices. But the distinction between these zones in semseyite is due to a higher Pb content and a lower Sb content in the lighter zone than in the darker zone and the metal and metalloid are the main constituents in the solid solution, but are not correlated. The Sb, Ag and Bi substitute for Pb in galena, but did not cause any zoning. Ore deposition was possible due to mixing of a hypersaline fluid with up to 26 wt.% NaCl equivalent (and occasionally with CaCl₂ up to 17 wt.%), which carried the metallic content of the fluid, with an extremely low salinity fluid of presumed meteoric origin that percolated down into the basement. The metals could have been leached from a mixture of mainly metasediments and also previous Sb–Au deposits by fluids that acquire high salinity in one of two probable ways: leaching of salt beds or following seawater evaporation. The entire mineralizing event probably occurred at a relatively low temperature, possibly between 120 and 230 °C. Remobilization of Pb, Zn, Ag, As, Sb and Cu will be due to the tectonic evolution of the opening of the Atlantic Ocean. This vein is probably of Alpine age.     

Structural controls and timing of fault-hosted manganese at Woodie Woodie,East Pilbara,Western Australia

High-grade fault-hosted manganese deposits at the Woodie Woodie Mine, East Pilbara, are predominantly hydrothermal in origin with a late supergene overprint. The dominant manganese minerals are pyrolusite, braunite, and cryptomelane. The ore bodies are located on, or near the unconformities between the Neoarchean Carawine Dolomite and the Paleoproterozoic Pinjian Chert breccia (weathering product of Carawine Dolomite), and sedimentary units of the overlying ca 1300–1100 Ma Manganese Group. Stratabound manganese is typically located above or adjacent to steep fault-hosted manganese. The ore bodies range in size from 0.2 to 5.5 Mt with an average of 0.5 Mt. Historically, over 35 Mt of manganese has been mined at Woodie Woodie, and current ore resources are 29.94 Mt at 39.94% Mn, 6.96% Fe (resource and reserves statement, June 2011, Consolidated Minerals Pty Ltd).Manganese mineralization at Woodie Woodie is related to northwest–southeast directed extension and basin formation during the Mesoproterozoic. Basin architecture is generally well preserved and major manganese occurrences are localised along growth faults which down-throw the Pinjian Chert Breccia into local extensional basins. Manganese ore bodies are typically located on steep 2nd and 3rd order structures that extend off the major growth faults. Mineralized structures display a dominant northeast-trend reflecting the direction of maximum dilation during northwest–southeast extension.A paragenetic sequence is identified for the manganese ore at Woodie Woodie, with early hydrothermal braunite–pyrolusite–cryptomelane–todorokite–hausmannite, overprinted by late supergene oxides. Preliminary fluid inclusion studies in quartz crystals intergrown with pyrolusite and cryptomelane indicate that primary and pseudosecondary inclusions display a range of salinities from 1 to 18 eq. wt.% NaCl and trapping temperatures estimated to be from 220º to 290º at 1 kbar pressure.A lead–manganese oxide (coronadite) is common in manganese ores at Woodie Woodie, and Pb-isotope studies of 40 lead-rich ore samples from 16 pits indicate mineralization occurred within an age range of 955–1100 Ma. A mixed source is suggested for the lead, but was predominantly basalts and/or volcanogenic sedimentary units (e.g., Jeerinah Formation) of the ca 2700 Ma Fortescue Group. The typically high Mn:Fe ratios and enrichment in elements such as Pb, As, Cu, Mo, Zn are consistent with a dominantly hydrothermal origin for the manganese at Woodie Woodie. Supergene manganese is distinguished from hypogene manganese by a marked enrichment in REE in the supergene manganese.An early structural framework, established during Neoarchean rifting, provides a major structural control on manganese ore distribution. The Woodie Woodie mine corridor is located in a zone of oblique strike-slip extension on major northwest-trending transform faults and north-trending oblique normal faults. A major transform structure at the southern end of the Woodie Woodie mine corridor (Jewel-Southwest Fault Zone) likely acted as a major fluid conduit for manganese-bearing hydrothermal fluids and this would account for the concentration of significant manganese ore occurrences to the north and south of this structure.     

The Hakkari nonsulfide Zn–Pb deposit in the context of other nonsulfide Zn–Pb deposits in the Tethyan Metallogenic Belt of Turkey

The Hakkari nonsulfide zinc deposit is situated close to the southeastern border of Turkey. Here both sulfide and nonsulfide Zn ≫ Pb ores are hosted in carbonate rocks of the Jurassic Cudi Group with features typical of carbonate-hosted supergene nonsulfide zinc mineralization. The regional strike extent of the mineralized district is at least 60 km. The age of the supergene deposit has not been determined, but it is probable that the main weathering happened during Upper Tertiary, possibly between Upper Miocene and Lower Pliocene. The Hakkari mineralization can be compared to other carbonate-hosted Zn–Pb deposits in Turkey, and an interpretation made of its geological setting. The zinc mineral association at Hakkari typically comprises smithsonite and hemimorphite, which apparently replace both sulfide minerals and carbonate host rock. Two generations of smithsonite are present: the first is relatively massive, the second occurs as concretions in cavities as a final filling of remnant porosity. Some zinc is also hosted within Fe–Mn-(hydr)oxides. Lead is present in cerussite, but also as partially oxidized galena. Lead can also occur in Mn-(hydr)oxides (max 30% PbO). The features of the supergene mineralization suggest that the Hakkari deposit belongs both to the “direct replacement” and the “wall-rock replacement” types of nonsulfide ores. Mineralization varies in style from tabular bodies of variable thickness (< 0.5 to 13 m) to cross-cutting breccia zones and disseminated ore minerals in pore spaces and fracture planes. At Hakkari a As–Sb–Tl(≫ Hg) geochemical association has been detected, which may point to primary sulfide mineralization, quite different from typical MVT.     

The Vilalba gold district,a new discovery in the Variscan terranes of the NW of Spain: A geologic,fluid inclusion and stable isotope study

This work defines the Vilalba gold district, a new gold region in the NW of Spain comprising three mineralized areas (Castro de Rei, Valiña–Azúmara and Arcos) and two different types of mineralization: 1) W–Au skarn in Castro de Rei, and 2) Au–As (Ag–Pb–Zn–Cu–Sb) vein/disseminated mineralization in Valiña–Azúmara and Arcos. Mineralization is mainly hosted by impure limestone and black slates (lower Cambrian) and spatially related to Variscan and Late-Variscan structures. Rhyolite dikes occur in Arcos (299 ± 6 Ma) and Castro de Rei, both consisting of peraluminous, high-potassium and calc-alkaline rocks. These dikes represent the fractionated expression of unexposed post-tectonic granitoids located at depth. The Castro de Rei area exhibits a contact aureole with biotite ± cordierite and calc-silicate hornfels. Prograde skarn consists of garnet, pyroxene, quartz, wollastonite and scheelite. The retrograde alteration took place in two stages and mainly consists of amphibole, epidote, zoisite, quartz, calcite, chlorite and sulfides. Gold mineralization in the skarn occurs as invisible gold in sulfoarsenides and as electrum related to Bi–Te–S minerals. The mineralization of Valiña–Azúmara and Arcos comprises two stages. The first consists of As-rich pyrite and arsenopyrite with invisible gold. The second stage mainly consists of base metal sulfides and Ag–Pb–Zn–Cu–Sb sulfosalts.Hydrothermal fluids involved in the skarn formation are low salinity (up to 6.6 wt.% NaCl eq.) aqueous carbonic fluids (H₂O + CO₂ ± CH₄ ± N₂) evolving into aqueous fluids during the last stage of gold mineralization. Stable isotope geochemistry indicates the importance of a magmatic fluid in the early stages (δ¹⁸O_SMOW from 7.5 to 11‰; δ³⁴S_CDT from 2.7 to 5.9‰) that evolved through interaction with host-rocks and mixing with metamorphic and/or meteoric fluids. The δ³⁴S_CDT values (7.8–10.9‰) of second retrograde stage sulfides suggest the incorporation of ³⁴S-enriched from host-rocks. In Valiña–Azúmara and Arcos, the fluid inclusion and isotope studies indicate similar hydrothermal fluids to those associated with the second retrograde skarn stage. Taking into account the fluid inclusion study and mineral geothermometry, an attempt was made to determine the P–T conditions of ore formation. The prograde skarn of Castro de Rei formed at temperatures and pressures ranging from 520 to 560 °C and from 1.7 to 2.5 kb. The mineralization of Valiña–Azúmara formed at minimum P–T conditions of 1.7 kb and 355 °C. The estimated temperatures for the Arcos mineralization are similar to those of Valiña–Azúmara (up to 383 °C) but at lower pressures.We propose the model of intrusion related gold systems (IRGSs) to explain the mineralizations of the Vilalba gold district. In this model, the Castro de Rei skarn and the Valiña–Azúmara mineralization represent a proximal and a distal deposit, respectively, relative to an unexposed granitoid situated at depth. We also consider Arcos as a distal deposit in relation to another unexposed granitoid located further south in the district.     

The geological significance of Pb–Bi- and Pb–Sb-sulphosalts in the Damajianshan tungsten polymetallic deposit,Yunnan Province,China

The Sanjiang Tethyan domain in SE Asia is one of the most important mineral belts in China. Cu, Pb–Zn, Ag, Au and Sn are the most important resources in this domain, while the tungsten mineralization is poorly reported. In this study, we report on mineralogy in recent discovered Damajianshan (DMJS) tungsten (–Cu–As–Mo–Bi) polymetallic deposit in the southern part of Sanjiang Tethyan domain related to Triassic quartz porphyry. Studies have shown that besides common ore minerals, such as native bismuth, bismuthinite, ikunolite, some specific minerals of Pb–Bi- and Pb–Sb-sulphosalts (e.g. izoklakeite, bournonite, cosalite, and boulangerite) have also been found. Based on paragenetic mineral assemblages, fluid inclusions, and thermodynamic studies, the physicochemical conditions were evaluated for the entire metallogenic process. The sulfur fugacity (logf_S2) ranges from − 9.7 to − 37 with ore-forming temperatures between 190 °C and 330 °C, and the oxygen fugacity (logf_O2) ranges from − 37.5 to − 38.5 when the temperature is 250 °C. The sulfur fugacity and oxygen fugacity show strong fluctuations with broadly negative correlation, indicating that these variations in physicochemical conditions should be responsible for mineral assemblages, and are one of the most significant factors leading to the formation of the DMJS deposit. Our mineralogical studies provide new information for tungsten mineralization and further exploration of tungsten resources in the Sanjiang Tethyan mineralization domain.     

Isotopic analysis of the super-large Shuangjianzishan Pb–Zn–Ag deposit in Inner Mongolia,China: Constraints on magmatism,metallogenesis, and tectonic setting

The super-large Shuangjianzishan Pb–Zn–Ag deposit is a newly discovered deposit located in the Huanggang–Ganzhuermiao polymetallic metallogenic belt of Inner Mongolia, NE China. The deposit's resource includes 0.026 Mt Ag, 1.1 Mt Pb, and 3.3 Mt Zn. The deposit is controlled by a NW-trending ductile shear zone and NE- and NW-trending faults in black pelite assigned to the lower Permian Dashizhai Formation. LREE enrichment, HREE depletion, Nb, Ta, P, and Ti depletion, and Zr and Hf enrichment characterize felsic magmatic rocks in the Shuangjianzishan Pb–Zn–Ag district. The ages of porphyritic monzogranite, rhyolitic crystal–vitric ignimbrite, and porphyritic granodiorite are 254–252, 169, and 130 Ma, respectively. Pyrite sampled from the mineralization has Re–Os isochron ages of 165 ± 7 Ma, which suggest the mineralization is associated with the ca. 169 Ma magmatism in the Shuangjianzishan district.Zircons extracted from the porphyritic granodiorite yield ε_Hf(t) values of − 11.34 to − 1.41, with t_DM2 dates of 1275–1901 Ma. The ε_Hf(t) values of zircons in the rhyolitic crystal–vitric ignimbrite and the ore-bearing monzogranite porphyry are 7.57–16.23 and 10.18–15.96, respectively, and their t_DM2 ages are 177–733 and 257–632 Ma, respectively. Partial melting of depleted mantle resulted in the formation of the ca. 254–252 Ma ore-bearing porphyritic monzogranite and the ca. 169 Ma rhyolitic crystal–vitric ignimbrite; dehydration partial melting of subducted oceanic crust resulted in the formation of the ca. 130 Ma porphyritic granodiorite. The porphyritic monzogranite was emplaced during the late stages of closure of the Paleo-Asian Ocean during the transformation from a collisional to extensional tectonic setting. The ca. 170 and ca. 130 Ma magmatism and mineralization in the Shuangjianzishan district are related to subduction of the Mongolia–Okhotsk Ocean and subduction of the Paleo-Pacific Ocean Plate, respectively.     

Geochemical and geochronological constraints on the formation of shear-zone hosted Cu–Au–Bi–Te mineralization in the Stanos area,Chalkidiki, northern Greece

Copper–gold–bismuth–tellurium mineralization in the Stanos area, Chalkidiki Peninsula, Greece, occurs in the Proterozoic- to Silurian-aged Serbomacedonian Massif, which tectonically borders the Mesozoic Circum-Rhodope metamorphic belt to the west and crystalline rocks of the Rhodope Massif to the east. This area contains the Paliomylos, Chalkoma, and Karambogia prospects, which are spatially related to regional NW–SE trending shear zones and hosted by marble, amphibolite gneiss, metagabbro, and various muscovite–biotite–chlorite–actinolite–feldspar–quartz schists of the Silurian Vertiskos Unit. Metallic minerals occur as disseminated to massive aggregates along foliation planes and in boudinaged quartz veins. Iron-bearing sulfides (pyrite, arsenopyrite, and pyrrhotite) formed prior to a copper-bearing stage that contains chalcopyrite along with galena, sphalerite, molybdenite, and various minerals in the system Bi–Cu–Pb–Au–Ag–Te. Fluid inclusion homogenization temperatures of primary aqueous liquid–vapor inclusions in stage I quartz veins range from 170.1 °C to 349.6 °C (peak at ~ 230 °C), with salinities of 4.5 to 13.1 wt.% NaCl equiv. Calculated isochores intersect P–T conditions associated with the upper greenschist facies caused by local overpressures during late-stage tectonic movement along the shear zone in the Eocene, which produced stretching and unroofing of rocks in the region. Values of δ³⁴S for sulfides in the Stanos shear zone range from 2.42 to 10.19‰ and suggest a magmatic sulfur source with a partially reduced seawater contribution. For fluids in equilibrium with quartz, δ¹⁸O at 480 °C varies from 5.76 to 9.21‰ but does not allow for a distinction between a metamorphic and a magmatic fluid.A ¹⁸⁷Re–¹⁸⁷Os isochron of 19.2 ± 2.1 Ma for pyrite in the Paliomylos prospect overlaps ages obtained previously from intrusive rocks spatially-related to the Skouries porphyry Cu–Au, the Asimotrypes Au, and the intrusion-related Palea Kavala Bi–Te–Pb–Sb ± Au deposits in northern Greece, as well as alteration minerals in the carbonate-replacement Madem Lakkos Pb–Zn deposit. Ore-forming components of deposits in the Stanos area were likely derived from magmatic rocks at shallow depth that intruded an extensional shear environment at ~ 19 Ma.     

Genesis of Luobuzhen Pb–Zn veins: Implications for porphyry Cu systems and exploration targeting at Luobuzhen-Dongshibu in western Gangdese belt,southern Tibet

Porphyry systems are known to form in magmatic arc environment and commonly include porphyry Cu, epithermal Pb–Zn–Au–Ag, skarn polymetallic mineralization, etc. The systems are rarely reported in collisional zones, such as the Gangdese belt in southern Tibet where many postcollisional porphyry copper deposits occurred. In addition, other types of mineral systems are rarely present except porphyry copper mineralization in the Gangdese belt. In this study, we present Pb–Zn-bearing quartz veins at Luobuzhen in the western Gangdese belt. The Luobuzhen Pb–Zn veins cross-cut dacite of the Linzizong Group with zircon U–Pb age of 50.1 ± 0.2 Ma and monzogranite with zircon U–Pb age of 17.1 ± 0.1 Ma. Ore minerals include sphalerite, galena, chalcopyrite, and pyrite; gangue minerals are quartz with minor chlorite and sericite. Primary fluid inclusions of quartz are liquid-rich, aqueous, and two-phase inclusions. The homogenization temperatures of these primary inclusions are moderate to high (267–400 °C), and salinities range from 8.9 to 18.4 wt.% NaCl equiv. Quartz has δ¹⁸O_SMOW values of 6.2–9.3‰, while sulfides have δ³⁴S_V-CDT values of −5.1‰ to 0.1‰, ²⁰⁶Pb/²⁰⁴Pb of 18.722–18.849, ²⁰⁷Pb/²⁰⁴Pb of 15.640–15.785, and ²⁰⁸Pb/²⁰⁴Pb of 39.068–39.560. These data suggest that magmatic fluids with contribution from meteoric water, magmatic sulfur, and lead derived from upper crust and metasomatized mantle by Indian continental materials would be critical for the Luobuzhen base metal mineralization.The Dongshibu area, located at ∼2 km east of the Luobuzhen, is characterized by high concentrations of Cu (up to 1450 ppm) and Mo (up to 130 ppm) of stream sediments, which is quite different from high concentrations in Pb, Zn, Ag, and Au shown in the Luobuzhen area. In addition, porphyry copper mineralization-related alteration and veins/veinlets occur in the Miocene monzogranite at Dongshibu. The monzogranite is characterized by high Sr/Y ratios, which are also shown on ore-forming intrusions in the Gangdese postcollisional porphyry copper deposits, and shows similar zircon Hf isotopes to the ore-related high Sr/Y intrusions from the Zhunuo porphyry copper deposit which is located ∼20 km northeast of the Luobuzhen-Dongshibu. A comprehensive analysis allows us to infer that the base metal veins at Luobuzhen are components of a porphyry Cu system with porphyry Cu mineralization likely present at Dongshibu and epithermal Au–Ag veins possibly occurring at Luobuzhen, which are indicative of the existence of porphyry copper systems in collisional zones. The potential porphyry Cu mineralization and epithermal Au–Ag veins should be targeted in future exploration at Luobuzhen-Dongshibu.     

The Late Paleozoic porphyry–epithermal spectrum of the Birgilda–Tomino ore cluster in the South Urals,Russia

The Birgilda–Tomino ore cluster in the East Uralian zone, South Urals, Russia, hosts a variety of Late Paleozoic porphyry copper deposits (Birgilda, Tomino, Kalinovskoe, etc.), high- and low sulfidation epithermal deposits (Bereznyakovskoe, Michurino), and skarn-related base metal mineralization (Biksizak) in carbonate rocks. The deposits are related to quartz diorite and andesite porphyry intrusions of the K–Na calc-alkaline series, associated to a subduction-related volcanic arc. We report microprobe analyses of ore minerals (tetrahedrite–tennantite, sphalerite, Bi tellurides and sulfosalts, Au and Ag tellurides), as well as fluid inclusion data and mineral geothermometry. On the basis of these data we propose that the Birgilda–Tomino ore cluster represents a porphyry–epithermal continuum, with a vertical extent of about 2–3 km, controlled by temperature decreases and fS₂ and fTe₂ increase from deeper to shallow levels.