Stibnite Precipitation Research Articles

Biochar-Sulfate Reducing Bacteria synergy: A green approach for antimony removal and recovery from high-concentrated waters

Environments with elevated antimony (Sb) levels often result from industrial and mining activities, causing harm to ecosystems due to the inherent toxicity. Traditional treatments aim to eliminate or decrease Sb toxicity, yet they often result in the generation of secondary pollution. This study explores a novel approach for enhancing biological sulfate-reduction by biochar addition to cope with high Sb concentrations. Moreover, this research postulates sulfate-reduction bioprocess as a feasible alternative to obtain valuable antimony sulfide. The findings indicate that sulfate reduction effectively removes antimony, particularly at high concentrations, using a non-specialized inoculum. Biochar plays a pivotal role in enhancing sulfate-reduction rates, reducing lag-phase periods, and enriching the microorganisms responsible for sulfate reduction.Interestingly, lower concentrations of Sb(III) (5–40 mg/L) and Sb(V) (5–100 mg/L) exhibited a lower removal percentage compared to higher concentrations of Sb(III) (80–500 mg/L) and Sb(V) (200–1000 mg/L). This phenomenon was attributed to the excess sulfide hindering the equilibrium of the first-order reaction at lower concentrations, while at higher concentrations, the reaction proceeded more rapidly. A combination of biochemical and physicochemical reactions facilitated the removal of >95 % Sb(III) and >97 % Sb(V) using biochar.Furthermore, various taxa displayed a significant logarithmic rate of change in their abundance, influenced by the application of biochar or the introduction of distinct antimony species. The biogenic sulfide generated through the sulfate reduction process reacted with the Sb species, resulting in the precipitation of stibnite (Sb2S3), Na3SbS3, and Na3SbS4. These precipitates are considered crucial precursors in electronic applications.In conclusion, this study constitutes a pioneering exploration of elevated antimony (Sb) concentrations under sulfate-reducing conditions, significantly contributing to an advancement of knowledge in the application of biological processes.

Mineralogical and geochemical facets of the massive deposition of stibnite-metastibnite at a seafloor hydrothermal field (Wakamiko Crater, Kagoshima Bay, Ryukyu Volcanic Arc)

Abstract Stibnite precipitates in the form of massive boulders at two active hydrothermal mounds in the submarine Wakamiko Crater (Ryukyu Volcanic Arc) as opposed to commonly observed accessory stibnite in the seafloor hydrothermal deposits. The stibnite dimorph, metastibnite, found here for the first time on the seafloor, appears to always form whenever stibnite is precipitated under submarine hydrothermal conditions. Our study shows that hydrothermal conditions of low temperatures (<50 °C) and low values of pH (<6) are favorable for the precipitation of stibnite on the seafloor. The stibnite probably does not precipitate at the measured vent fluid temperatures (i.e., 177.6 – 187.0 °C) along the chimney conduits, but rather at temperatures <50 °C and at slightly reduced to slightly oxic conditions (Eh = -0.5 to +0.5 V) within the chimney walls and hydrothermal mounds. Metastibnite deposition appears to be the result of rapid quenching of hot hydrothermal fluid when mixed with cold seawater and rapid precipitation at the interface between stibnite and vent fluid. The low concentrations (usually below detection limits) of the trace elements (Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, P, Pb, Sr, V, Zn) in the stibnite deposits from Wakamiko Crater are likely a result of decreased metal-transporting capacity of the precipitating vent fluid due to its low chlorinity. Low-chlorinity venting implies sub-seafloor boiling and phase separation of the hydrothermal fluid. Sluggish hydrothermal fluid/seawater mixing within the walls of the chimneys and mounds favors the reduction of sulfate dissolved in the hydrothermal fluids and results in a heavy S isotope composition of the sulfate in the vent fluids. Sulfate reduction and disproportionation of magmatic SO2, both leading to heavy S isotope composition of sulfate in the vent fluids, seem to be common processes in volcanic arc/back-arc submarine hydrothermal settings.

Gold, antimony and mercury ore formation and metallogenic link in the Sandu-Danzhai area, Jiangnan Orogen, SW China

The turbidite-hosted Au-Sb-Hg deposits in the Sandu-Danzhai area are distributed along the southwestern marginal fault of the Jiangnan Orogen, yet any genetic link among the Au, Sb and Hg mineralization and their respective ore-forming process remain unclear. Here, we investigate the Paiting Au(-Hg) and Miaolong Au-Sb deposits and present a new metallogenic model based on detailed petrographic observations, and in-situ trace element (EPMA and LA-ICP-MS) and sulfur isotope (fs-LA-MC-ICPMS) analyses on sulfide minerals. Our results show that the ore formation in the Sandu-Danzhai metallogenic belt (SDMB) can be divided into Au (pyrite + arsenopyrite + dolomite), Au-Sb (pyrite + arsenopyrite + stibnite + quartz), Sb (stibnite + native antimony + barite + dolomite + quartz) and Hg (cinnabar + calcite) stages, based on mineral paragenetic and vein crosscutting relationships. Trace element compositions suggest that progressive As enrichment in pyrite is accompanied by increasing Au, Sb and Cu contents, implying that these elements may have been leached from the same source via fluid-rock reactions. Sulfur isotope compositions of the sulfates and sulfides in the Au-Sb-Hg ores reveal that the sulfur was originated from thermal-chemical sulfate reduction (TSR) of marine sulfates in the Cambrian ore-bearing strata. Thus, we propose that deep metamorphic fluids (as evidenced from the high fluid CO2 and CH4 contents) may have promoted ore-material (e.g., Au, Sb, As, Hg) mobilization in the metamorphic basement and/or Cambrian strata. As for the metal transport and precipitation mechanism, fluid-rock interaction may have decreased the ore-fluid As content and caused auriferous pyrite precipitation. Meanwhile, changes in temperature and oxygen-sulfur fugacity may have significantly decreased Sb solubility, leading to extensive stibnite precipitation. Cinnabar associated with calcite was likely deposited via carbonate dissolution in the Cambrian strata in late hydrothermal (waning) stage. Overall, we propose that the Au-Sb-Hg deposits in the SDMB are best classified as orogenic type, and the metallogeny was controlled by boundary faults of the Jiangnan Orogen.

Telescoped boiling and cooling mechanisms triggered hydrothermal stibnite precipitation: Insights from the world’s largest antimony deposit in Xikuangshan China

AbstractSociety annually consumes 250% more Sb relative to the year 1960 and a sustainable supply of antimony depends critically on understanding the precipitation mechanism of stibnite (Sb2S3) that is the globally predominant source of this important technology metal. Previous solubility studies revealed that antimony is transported in mesothermal hydrothermal fluids mainly as the aqueous species thioantimonite (H2Sb2S4, HSb2S4−, Sb2S42−) and hydroxothioantimonite [Sb2S2(OH)2]. Thioantimonite can transform to hydroxothioantimonite with a decline of H2S concentration. However, whether this transition occurs in hydrothermal systems and its role in stibnite precipitation are unknown. In this work, bulk Sb isotope measurements for stibnite from the world’s largest Sb deposit in Xikuangshan China were conducted to address ore fluid evolution and stibnite precipitation mechanisms. The abundance of the stable antimony isotopes 121Sb and 123Sb were measured in stibnite from the Xikuangshan orebodies and reported as δ123Sb. The δ123Sb values show a trend of decreasing first and then increasing from proximal to distal parts of orebodies. This reveals that 123Sb had been preferentially partitioned from the ore fluid into stibnite first, then 123Sb remained preferentially dissolved in the ore fluid. These data indicate that the dominant Sb-complex transforms to Sb2S2(OH)2 from H2Sb2S4 with consumption of H2S. Speciation diagram considerations indicate that stibnite precipitation from the ore fluid was controlled by two telescoped processes: (1) boiling of the ore fluid induced a decrease in H2S that reduced the solubility of H2Sb2S4, and (2) subsequent cooling that induced a decrease in the solubility of Sb2S2(OH)2. This study highlights that understanding the controls of Sb isotope fractionation is critical to constrain fluid evolution and stibnite precipitation mechanisms in Sb-rich mineral systems. In particular, the stable Sb complex in the hydrothermal ore fluid may change during fluid evolution and affect the isotope fractionation mechanism.

Mineralogy, geochemistry and microbiology insights into precipitation of stibnite and orpiment at the Daiyon-Yonaguni Knoll (Okinawa Trough) hydrothermal barite deposits

Samples of active chimneys, chimney flanges and massive sulfides from the Daiyon-Yonaguni Knoll hydrothermal field are composed of major barite and minor stibnite and orpiment. Barite is inferred to precipitate from focused-discharge fluids composed of >40% hydrothermal end-member fluid at T = 100-240°C, whereas the stibnite and orpiment are later and lower temperature precipitates. The hydrothermal fluids from this field were subject of sub-seafloor boiling and phase separation and, consequently, are brine-rich depleted in volatile and enriched in non-volatile elements. Boiling and phase separation exerted major control on the rare earth elements (REE) partitioning in the vent fluids: high-chlorinity high-temperature fluids were enriched in light REE and low-chlorinity low-temperature fluids were enriched in heavy REE. Y/Ho molar ratio and Ce anomaly of the vent fluids suggest that the seawater has not completely reacted with the basement rocks and has not equilibrated with them. The trace element concentrations in the hydrothermal deposits suggest a complex interplay among hydrothermal, hydrogenetic and microbial processes. Sulfur isotope composition of the sulfides suggests that the sulfide S is a mixture of both basement rock and seawater S with a higher proportion of the basement rock S. The sulfate dissolved in the fluids was subjected to reduction during a slow mixing of hydrothermal fluid and seawater within the chimney walls of the Tiger and Abyss vents and this resulted in a heavy S-isotope composition of the vent fluid sulfate. Lead isotope composition of the hydrothermal deposits indicates mixing relationships suggesting that Pb and potentially other metals with similar geochemical behavior were derived from two or three sources. The Pb isotopes in the hydrothermal deposits imply that an enriched source, either sediments or extended continental lithosphere, and a depleted source, potentially back-arc mafic volcanics, are present in the area of Daiyon-Yonaguni Knoll. Filamentous orpiment found in the deposits is supposed to be either heavily mineralized fungal hyphae or pure abiogenic biomorphs. Presence of carbonaceous matter on and around the orpiment filaments suggests for microbial activity during filament formation. The filaments experienced temperature of 209.1±37.1°C which falls within the temperature range of the Daiyon-Yonaguni Knoll vent fluids. Stability phase diagrams modeling reveals that the stability of stibnite does not depend on the vent fluid chlorinity, but depends on the vent fluid temperature: the area of stibnite stability increases with decreasing vent fluid temperature and results in stibnite precipitation at low log10a of Sb2S42- and less reduced environment (Eh still <0). Orpiment is stable in a wide range of log10a of H2AsO4-, in reduced conditions and at high S activity. Barite is stable in wide range of log10a of Ba2+ and precipitates in slightly reduced to slightly oxic conditions.

Formation of the Banxi Sb deposit in Eastern Yangtze Block: Evidence from individual fluid inclusion analyses, trace element chemistry, and He-Ar-S isotopes

The Banxi Sb deposit (>100,000 t Sb metal with a grade of 0.02%–64.5% Sb (typically 15.3%–25.9% Sb) in the Eastern Yangtze Block is hosted in Neoproterozoic low-grade metamorphic clastic rocks of the Banxi Group. The deposit is characterized by vein-type Sb-only mineralization. Analyses of individual quartz-hosted fluid inclusions obtained by LA-ICP-MS identified Na as the most abundant cation (thousands to tens of thousands of ppm) in the ore-forming fluids of the Banxi Sb deposit, together with variable contents of K, Ca, Al, As, Fe and Sb (tens to thousands of ppm). Multiple chemical criteria, including high Na+/K+ (typically 3–15) and low Mn2+/Na+ (0.003–0.2) and Sr2+/Na+ (0.001–0.01) ratios of individual fluid inclusions, suggest that the fluids responsible for quartz and stibnite precipitation in the Banxi Sb deposit were likely dominated by basinal brines within low-grade metasedimentary rocks. Moreover, the extremely low 3He/4He ratios (0.001–0.048Ra) but relatively high 3He/36Ar (0.5 × 10−5–5.8 × 10−4) and 40Ar/36Ar ratios (323–1111 with an average of 737) of fluid inclusions trapped in ore-stage quartz further support a sedimentary origin of ore-forming fluids in this deposit. The positive and homogeneous sulfur isotopic values (δ34S = 8.0–9.5‰) of stibnite and arsenopyrite are comparable to those of sulfides in Proterozoic metasedimentary rocks (δ34S = 5.6–11.5‰), indicating these metasedimentary rocks may have served as the primary source of S for the Banxi Sb deposit. Combined with geological features and new trace element chemistry data for quartz and stibnite, we envisaged a new formation model for the Banxi Sb deposit that assumes that circulation of weakly alkaline basinal brines through faults under an extensional tectonic setting during the Early Cretaceous (∼130 Ma), mobilization of Sb and S from the underlying and host metasedimentary rocks and ascent of ore- forming fluids along faults, and ultimately precipitation of Sb minerals in or around fault/fracture zones as a result of the decreasing pH of the ore-forming fluids as well as sulfidation during fluid-rock reaction.

Fluid inclusion, H–O–S isotope and rare earth element constraints on the mineralization of the Dong’an Sb deposit, South China

Systematic geochemical study on the Cambrian strata-hosted Dong’an Sb deposit in the Central Hunan Sb belt would provide key information on the origin of the low-temperature mineralization in South China. In this study, microthermometric, H–O isotopic and fluid composition analyses on ore-bearing quartz, S isotopic analyses on sulfides, and rare earth element (REE) analyses on wall-rocks and monominerals (stibnite, pyrite and quartz) in ores were conducted to constrain the genesis of the Dong’an Sb deposit. Two major stages of mineralization were identified in the Dong’an deposit: (1) an early pyrite-stibnite-quartz stage mineralization with intense wall-rock alteration occurring at depth of the deposit, and (2) a late quartz-stibnite stage mineralization occurring at shallow depths. Microthermometric analyses reveal a low temperature (150 to 230 °C), low salinity (4.5–7.0 wt% NaCl equiv.), low density (0.88–0.96 g/cm3), low pressure (4.5 MPa) and weakly acid (pH = 5.74) fluid for the Sb mineralization. Compositional analyses for fluid inclusions show that the main ion compositions are Na+, K+, Mg2+, Ca2+, F−, Cl− and SO42−, while the gas compositions are dominated by H2O and CO2. This suggests that the ore-forming fluids were enriched in alkali metals, sulfur and halogen. The H–O isotopic compositions (δ18OH2O = 2.52‰ to 7.13‰, δ2HH2O = −88.6‰ to −58.3‰) of fluid inclusions in quartz suggest a mixture of magmatic water, metamorphic rocks-derived brine and meteoric water. The δ34S values of stibnite (−1.32‰ to +2.86‰) and pyrite (+17.4‰ to +23.6‰) are very different, suggesting multi-sulfur sources involving buried magmatic rocks, ore-bearing meta-sedimentary rocks and deep basement rocks. The decreasing of REE contents from early to late mineralization stages reflects a decrease of temperature, reduction of fluid-rock interaction and input of meteoric water along with the stibnite precipitation. We propose that Precambrian strata that underwent regional metamorphism during Early Paleozoic acted as a Sb source bed, whereas strong tectono-magmatism in the early Mesozoic provided thermal driving force for the Sb mineralization occurring under a tensile stress in secondary faults at the shallow crust. This study highlights the use of multi-geochemical methods to constrain the genesis of large-scale Sb mineralization in South China.

Genesis of the Banxi Sb deposit, South China: Constraints from wall-rock geochemistry, fluid inclusion microthermometry, Rb–Sr geochronology, and H–O–S isotopes

The Banxi Sb deposit is located in the world-class central-western Hunan Sb belt in South China, with quartz-vein type Sb-only mineralization hosted by Neoproterozoic epimetamorphic clastic sedimentary rocks. In this contribution, microthermometric, Rb–Sr geochronological and H–O isotopic analyses on fluid inclusions trapped in quartz, S isotopic studies on stibnite, and major-trace elemental measurements on fluid-altered and unaltered wall-rocks are presented to constrain the genesis of the deposit. The fluid inclusions are characterized by low homogenization temperature (170–260 °C) and low salinity 3–7 wt% NaCl equiv., with a low fluid density of 0.72–0.93 g/cm3 and a pH of 5.59. The low δDw (fluid δ2H, –140‰ to –107‰) whereas positive δ18OV-SMOW (15.9–17.2‰) and δ18Ow (fluid δ18O, 5.9–8.4‰) values in quartz indicate that the mineralizing fluid was generated from the low-grade metamorphic basement rocks and received a certain input of meteoric water. The Rb–Sr isotopic compositions of quartz samples yielded an isochron age of 196 ± 4 Ma (1σ, MSWD = 0.70) for quartz-stibnite ores. A highly radiogenic 87Sr/86Sr value (0.72663–0.74002, initial 87Sr/86Sr = 0.72640) indicates that ore-forming materials are derived mainly from basement rocks, and a direct material contribution from local granitic rocks can be ruled out. The δ34SV-CDT values of stibnite range narrowly from 4.81‰ to 6.72‰ and are in the δ34SV-CDT range of the metamorphic rocks, indicating that the sulfur was sourced from the basement rocks by sulfate reduction. Compositional differences between fluid-altered (decolorized) and unaltered wall-rocks are obvious: the migrated SiO2, SO3, LREE, Hf, Nb, Zr, Ta, Th, U, Mo, Sn, W into altered wall-rocks suggests a deep basement metamorphic rocks-derived Si-rich alkaline brine for the fluid-rock interaction; while the leached Fe2O3, MgO, MnO, TiO2, Ba, Cs, Rb, As, Co, V, Ni, Sb, Sc, Cu, Pb and Zn from the altered rocks imply a material contribution of Banxi Group wall-rocks during the Sb mineralization process. Consequently, we conclude that the quartz-stibnite stage of the Banxi Sb deposit was formed during the Late Triassic orogeny in the Xuefeng Mountain region. Heated by granitic magmatism, Sb and S were leached from the basement rocks, forming an initial Si-rich and alkaline ore-bearing fluid. Precipitation of stibnite from the fluid resulted from interacting with wall-rocks and mixing of meteoric water, coupled by releasing of stress, decreasing of temperature and lowering of the pH at higher crustal levels.

Fluid Inclusion Studies of Comb Quartz and Stibnite at the Hishikari Au–Ag Epithermal Deposit, Japan

AbstractFluid inclusion microthermometry was conducted on late‐stage barren comb quartz and the latest stibnite at the Hishikari deposit to characterize the hydrothermal activity responsible for vein formation. Eight fluid inclusion assemblages (i.e. fluid inclusions trapped at the same time, ‘FIAs’) were studied to determine the formation fluid temperatures and salinities for the comb quartz in the Shosen No. 2 vein, Sanjin ore zone, and the stibnite in the Seisen No. 1–1 vein, Yamada ore zone.The average homogenization temperatures (the formation temperatures) of the seven FIAs from the comb quartz were between 207 and 230°C, while the average homogenization temperature (the formation temperature) of an FIA from the stibnite was 113°C. The measured fluid salinities of the seven FIAs from the comb quartz were low, ranging between 0.0 and 1.1 wt% NaCl equiv., indicating that dilute fluids were responsible for the comb quartz formation.By comparison with previous microthermometric data, the formation temperatures of the studied comb quartz were higher than those of columnar adularia and comb quartz at most other veins (generally around 200°C) but were similar to those of columnar adularia at Keisen veins (230°C) in the same ore zone. The higher formation temperatures both in the Shosen and the Keisen veins in the Sanjin ore zone indicate that the fractures corresponding to the vein system at the Sanjin ore zone were main conduits for hot ascending fluids.The low formation temperature of stibnite in the latest stage (113°C) indicates that stibnite precipitation occurred during a waning stage of hydrothermal activity. Combined with previous thermodynamic data on antimony solubilities, the large discrepancy between the formation temperature of the comb quartz (200–230°C) and that of the stibnite suggests that the stibnite may have precipitated as a result of a drastic cooling of the hydrothermal system.

Fluid inclusions and ore precipitation mechanism in the giant Xikuangshan mesothermal antimony deposit, South China: Conventional and infrared microthermometric constraints

The giant Xikuangshan antimony deposit, located in the Xiangzhong (central Hunan) Basin, South China, is the largest antimony deposit in the world. Stibnite is the predominant ore mineral, and gangue minerals consist of quartz, calcite, fluorite and barite. The ore mineral assemblages include early-stage quartz-stibnite, fluorite-quartz-stibnite and barite-quartz-stibnite, and late-stage calcite-stibnite. In spite of numerous research works on the Xikuangshan deposit during the past several decades, the signatures of the ore-forming fluids and the ore precipitation mechanisms are poorly constrained. In order to characterize the fluids responsible for antimony mineralization and ascertain the genetic processes in the Xikuangshan ore district, conventional and infrared microthermometric measurements have been performed in this study on fluid inclusions hosted in transparent minerals (quartz, fluorite and barite) and opaque stibnite, respectively. Four types of fluid inclusions were identified for the early-stage mineralization based on their phase assemblages, including type I (pure liquid inclusions), type II (two-phase, liquid-rich aqueous inclusions), type III (two-phase, vapor-rich aqueous inclusions) and type IV (pure vapor inclusions). Stibnite only contains type I and type II inclusions, while all types of fluid inclusions are common in the gangue minerals. The homogenization temperatures and salinities of fluid inclusions in stibnite and associated gangue minerals in this ore district display significant differences. Fluid inclusions in stibnite exhibit relatively low homogenization temperatures (112–323 °C) and higher salinities (0.2–15.4 wt% NaCl equiv.) than inclusions in coexisting gangue minerals (119–366 °C, 0.2–4.2 wt% NaCl equiv.), usually about 50 °C less than the “intergrown” gangue minerals. According to the petrography of fluid inclusions and the relationship between their homogenization temperature and salinity, it was concluded that stibnite and gangue minerals in the Xikuangshan ore district are not co-genetic, instead, they were deposited from two distinctly different hydrothermal solutions. Fluid mixing was responsible for stibnite precipitation, but the precipitation of gangue minerals resulted from fluid boiling due to an abrupt drop in pressure. The Xikuangshan deposit is a typical example of mesothermal deposits, rather than an epithermal deposit as previously considered.

Mineralogy, geochemistry and fluid inclusions of the Qinglong Sb-(Au) deposit, Youjiang basin (Guizhou, SW China)

The Qinglong deposit is a newly-characterized, large Sb-(Au) deposit in the Youjiang basin (Guizhou, SW China). Four mineralization stages are identified (i.e., pre-ore, early-ore, late-ore and post-ore) in this study based on crosscutting relationships. Our study shows that the Qinglong Sb mineralization (early-ore stage) was dominated by quartz-stibnite ± fluorite, whilst the Sb-Au mineralization (late-ore stage) comprises quartz-stibnite ± pyrite. Electron Probe Microanalysis (EPMA) indicates that the Au is present as Au1+ in the arsenian pyrite. Besides, our new fluid inclusion data from fluorite, stibnite and quartz show that the Sb-Au-rich hydrothermal fluids were derived from the mixing fluids consisting of H2O, NaCl, hydrocarbon and minor CO2. In the early-ore stage, the ore-forming fluids are characterized by medium to low temperatures (161–294 °C, mean: 220 °C), medium to low salinities (0.35–13.18 wt% NaCl equiv.), low pH, and the presence of hydrocarbons and CO2. In comparison, the late-ore stage ore-forming fluids are featured by low temperatures (113–255 °C, mean: 175 °C), low salinities (0.18–6.30 wt% NaCl equiv.) and nearly neutral pH. The δ34S∑S values (−2.8 to 2.3‰) of the ore-forming fluids suggest that the sulfur at Qinglong was dominantly magmatic-derived. From the early-ore to late-ore stage, the ore-forming fluid temperature and oxygen fugacity (fO2) decrease but the pH increases (from acidic to neutral). Such physicochemical transition may have significantly decreased the Sb solubility from 10 s to 100 s of ppm to 0.001 ppm. Therefore, we propose that fluid mixing was the main process that substantially reduced the fluid temperature and oxygen fugacity, which effectively lowered the Sb solubility and led to abundant stibnite precipitation. The stibnite precipitation had likely decreased the H2S concentrations of the ore-forming fluids, thereby destabilizing the AuHS0 complexes in the fluids and caused local Au precipitation.

Costerfield antimony-gold deposit, southeast Australia: Coupling between brittle deformation and dissolution-precipitation reactions in the Melbourne Zone

The antimony-gold deposits at Costerfield are a swarm of ‘dyke-like’ antimony-gold lodes within a brittle transpressional fault system. They are hosted in the Lower Silurian sedimentary rocks of the Melbourne Zone of the Lachlan Orogen. Individual lodes are dominated by stibnite or stibnite-gold and widths vary from 1cm to ∼200cm (averaging 30cm) and lengths can exceed 1km. Lodes occur as fault-parallel layers or lenses mantled by deformed quartz-rich margins or overgrowths of hydrothermal quartz and carbonate. Inclusions in the stibnite-rich lodes include vuggy randomly oriented prismatic crystals, crack-sealed and stretched quartz with sugary mosaics of equant quartz grains and quartz breccias. Randomly oriented quartz and stibnite textures, common in the centre of the lodes, indicate free growth from a fluid. Throughout the mineralized system, the hydrothermal stibnite has replaced and overgrown the earlier quartz. Deformed lode margins preserve sub-horizontal lineations and evidence of oblique crack-seal re-opening that reflect emplacement associated with late sinistral strike-slip movements in bounding faults. Crystallographic orientation data collected from the marginal quartz, using neutron diffraction and supported by microstructural observations, reveal that lode emplacement also involved dissolution-precipitation creep and pressure solution. Both the marginal quartz and the lodes are overprinted by later microfractures, within which there has been precipitation of stibnite, pyrite, arsenopyrite, sphalerite and minor gold. 3D neutron tomography revealed individual gold crystals, with gold voxel sizes ranging from 140µm to ∼580µm, were located in late arsenopyrite-gold domains that overprint the stibnite. The mechanical evolution of the lodes involved short-lived brittle processes in combination with dissolution-precipitation crystallization in active fault zones. These ore bodies provide insights about the dynamics of fluid flow and flow velocities when faults breach over-pressured reservoirs of hydrothermal fluid. Our results also suggest that the Costerfield deposit was formed directly from metal-rich metamorphic fluids produced during Tabberabberan (∼375Ma) prograde metamorphism of sedimentary rocks near the base of the Lower Paleozoic Melbourne Zone, which lie above the Proterozoic Selwyn Block. From a reinterpretation of seismic reflection data, the deformation in the Melbourne Zone sedimentary wedge is characterized by thrusts isolating relatively undeformed packages of sedimentary units, which were moved in a piggyback manner up west-dipping faults. The ore-bearing fluids migrated upwards, at least in part, along these footwall thrusts from the base of the Heathcote Fault Zone. In the upper levels of the sedimentary package, out-of-sequence strike-slip, sub-vertical splays from these second order faults carried the mineralizing fluids to the orebodies. East-west compression during the Tabberabberan Orogeny preceded a northwest-southeast-oriented stress field which reflects the collision of VanDieland against the Gondwanan margin. This produced the sinistral strike-slip faults, which in turn controlled the overall permeability of the hydrothermal system.

Mineralogy, sulfur isotopes and infrared microthermometric study of the Leishan-Rongjiang antimony ore field, SW China

The Leishan-Rongjiang antimony ore field (LAOF) is in a unique geotectonic location in the uplift between the Youjiang and Xiangzhong basins. This paper focuses on two representative deposits in the LAOF: the Bameng and Peize antimony (Sb) deposits. We analyzed fluid inclusions (FIs) in stibnite and coexisting quartz, as well as the sulfur isotopic composition of stibnite, to better understand the nature of the ore-forming fluid and the metallogenic process. The FIs data from samples of the stibnite and coexisting quartz indicate that the ore-forming fluids were characterized by low-temperature (150–210 °C), low-salinity (1.5 wt%–6.0 wt% NaCl equiv.), and low-density (0.872–0.961 g/cm3). The δ34S values of stibnite (−8.21‰ to 3.76‰, average = −6.30‰) fall in between the sulfur isotopic compositions of the mantle and of biogenic sulfur in sedimentary rocks. However, the δ34S∑S values (−4.41‰ to +0.04‰, average = −2.49‰) of the ore-forming fluids are generally closer to the sulfur isotopic composition of the mantle source, indicating that the sulfur in the LAOF was mainly sourced from the mantle, but with possible involvement of biogenic sulfur. In addition, FIs petrography and ore deposit geology show that fluid boiling resulted from an abrupt decrease in pressure, which may have triggered the precipitation of stibnite. We conclude that low-temperature, dilute hydrothermal fluids with mixed origins migrated along the regional fault and interacted with the wall rock, extracting the ore-forming materials. Then, the ore-forming fluids were injected into the fault fracture zones.

A Study on the Mineralization of the Woxi Au–Sb–W Deposit, Western Hunan, China

AbstractThe Woxi Au–Sb–W deposit in the western Hunan Province, China, is of hydrothermal vein type characterized by a rare mineral assemblage of stibnite, scheelite and native gold, of which gold fineness ranges from 998.6 to 1000. The mineralization sequence observed in the deposit is, from early to late, coarse‐grained pyrite – scheelite – stibnite – Pb–Sb–S minerals – sphalerite (+ cubanite) – fine‐grained pyrite. Native gold may have precipitated with scheelte. Microthermometric and LA–ICP–MS analyses of fluid inclusions in scheelite, quartz associated with scheelite and stibnite and barren quartz clarified that there may be at least three types of hydrothermal fluids during the vein formation in the Woxi deposit. Scheelite and native gold precipitated from the fluid of high temperature and salinity with high concentrations of metal elements, followed by stibnite precipitation. The later fluid of the highest temperature and salinity with low concentrations of the elements yielded the sphalerite mineralization. The latest fluid of low temperature and salinity with low concentrations of the elements is observed mainly in barren quartz. The remarkably high Au/Ag concentration ratios determined in the fluid inclusions in scheelite might be the reason for the extremely high gold fineness of native gold.

Controls on stibnite precipitation at two New Zealand geothermal power stations

Stibnite (Sb 2S 3) forms in the heat-exchanger units of several New Zealand binary geothermal power stations. By analysing aqueous samples collected from two representative plants, it was determined that stibnite forms at a rate of 8.7 and 15.8 kg/day at the Rotokawa and Ngawha power stations, respectively. These results were compared to theoretical predictions of stibnite solubility. It was shown that pH change is the principal cause of stibnite deposition at Rotokawa, while at Ngawha the effect of temperature decrease is more significant. Antimony was not detected in vapour-line samples, suggesting that transport is completely within the aqueous phase.

Geology, mineralogy and geochemistry of the gold-bearing stibnite and cinnabar deposits in the Emirli and Halıköy areas (Ödemiş, İzmir, West Turkey)

Deposits of stibnite and cinnabar show a strong spatial association with metamorphic rocks and occur mainly within orogenic belts. Our study addresses the Emirli stibnite and Halıköy cinnabar deposits within the Menderes Massif in western Turkey. Stibnite mineralisation occurs as stratabound lenses in graphite- and mica-schist, and as structurally controlled veins. Both types have a common mineral paragenesis containing pyrite, arsenopyrite, stibnite, gold, base metal sulphides, marcasite, realgar, orpiment and cinnabar. Realgar, orpiment and cinnabar are not present in the stratabound lenses. Quartz is the principle gangue mineral in all the deposits. The initial fluids were dilute, carbonic and rather hot (with Th > 300 °C). Deposition of pyrite and arsenopyrite is probably due to cooling of the fluids and to sulphidation and/or decreasing fO 2, caused by interaction with syn-sedimentary sulphides in the country rocks. Arsenopyrite geothermometry indicates an average depositional temperature of 330 °C in the initial quartz vein. Vein formation increased the fluid pressure and caused effervescence, which resulted in a sudden pressure drop from 1.4 kbar during the initial quartz formation to ∼440 bars, and stibnite precipitated at 232 to 307 °C. Boiling and concomitant sulphur loss during stibnite precipitation may have also initiated gold deposition. Further cooling below 190 °C under a pressure of ≤ 600 bars caused cinnabar deposition, mainly in the Halıköy deposit. Salinity of the fluids during stibnite and cinnabar precipitation is 0.8 to 7.1 wt.% NaCl eq. and suggests a meteoric fluid. The structural framework induced by the initiation of extensional tectonics served as conduits for the penetration of surficial fluids to the environs of a possible magmatic heat source evidenced by thermal waters in the region. Stibnite from the stratabound (graphite-schist hosted) lenses and the crosscutting veins in the Emirli deposit have sulphur isotope compositions in a range of − 5.8‰ to − 8.9‰. δ 34S values of pyrite from the graphite-schist zones and mica-schists are in the ranges of − 8.9‰ to − 7.7‰ and − 10.2‰ to − 11.7‰, respectively. It is therefore concluded that the sulphur in stibnite originated from sulphide minerals in the country rocks, which in turn may have a source related to bacterial reduction of sulphate within the pre-metamorphic sediments. Cinnabar has heavier δ 34S contents (− 6.5‰ to − 6.8‰), suggesting a minor magmatic sulphur contribution towards the final stages of mineralisation.

Stable isotope study of antimony deposits in the Muratdagi region, western Turkey

The Muratdagi region is rich in antimony deposits having the following common characteristics: post Miocene age, location on the down-thrown blocks next to normal faults, in the vicinity of active or fossil thermal springs, and in contact with carbonate rocks. The isotopic composition of — 7‰. SMOW of the mineralizing fluid calculated from the measured °18O of quartz and the fluid inclusion microthermometry, is indicative of meteoric water origin. The °13C of the inclusion CO2 of — 19.1 to — 25.4‰ PDB is indicative of interaction with organic material-graphite. The °34S of stibnite — 3.6 to — 0.7‰ is, in view of the mineral assemblage, indicative of magmatic origin of the sulphur. A tightly confined set of structural, lithological, hydrological and geochemical features define a sequence of geochemical processes; formation of acid and reducing fluid, leaching and transport of antimony complexes and precipitation of stibnite within defined lithological units. The set of processes seems to have taken place within a space of 5000 m lateral and 1000 m vertical extension.

C-O-H-N fluid inclusions associated with gold-stibnite mineralization in low-grade metamorphic rocks, Mari Rosa mine, Caceres, Spain

AbstractThe Mari Rosa mine lies within a low-grade Precambrian alternating series of black shales and metagreywackes in the Spanish Hercynian massif. There are two generations of mineralized veins: V2, gold-(stibnite)-bearing quartz veins, parallel to the main cleavage, and V3, stibnite-bearing quartz veins which postdate the main deformation event.Four main types of inclusions have been identified. Type I, II and IV are aqueous-carbonaceous inclusions, with variable degrees of filling, while type III are non-aqueous and typically single-phase at room temperature. Except for type I (absent in V3), similar inclusions have been observed in both V2 and V3 veins. Gas compositions are always characterised by CH4-N2-CO2 assemblages, ranging from CO2-rich mixtures in the earliest inclusions (type I), to N2-rich mixtures in the latest inclusions (type IV).Gold precipitation in V2 veins can be related to type I inclusions at T &gt; 380°C (TH = 300–380°C). A subsequent drop in XCO2 and cooling are recorded in type II and III inclusions, interpreted to be the result of unmixing of a previously homogeneous fluid derived from type I. This boiling would provoke the precipitation of stibnite at 300°C and 1 kbar. The type IV inclusions, which are the richest in H2O, represent a late fluid circulation at lower temperatures (TH = 190–280°C).

Solubility of stibnite in hydrogen sulfide solutions, speciation, and equilibrium constants, from 25 to 350°C

Solubility of stibnite (Sb 2S 3) was measured in aqueous hydrogen sulfide solutions as a function of pH and total free sulfur (TFS) concentrations at 25, 90, 200, 275, and 350°C and at saturated vapor pressures. At 25 and 90°C and TFS ≈ 0.01 molal solubility is controlled by the thioantimonite complexes H 2Sb 2S o 4, HSb 2S − 4, Sb 2S 2− 4 (and polymers of the general composition H 2−xSb 2nS x− 3n+1). At higher temperatures the hydroxothioantimonite complex Sb 2S 2(OH) 0 2 (or polymers of composition Sb 2nS 3n-1(OH) 0 2) becomes dominant. Polymerization due to condensation reactions yields long chains made up of trigonal-pyramidal SbS 3-groups (and SbS 2OH-groups). Equilibrium constants were derived for the dimers. The transition from thioantimonites to the hydroxothioantimonite species at approximately 120°C is endothermic and is entirely driven by a gain in entropy. Stibnite solubility calculated for some geothermal fluids indicate that these fluids are undersaturated in Sb if stibnite is the solid equilibrium phase. At high temperatures (>100°C) precipitation of stibnite from ore fluids can occur in response to conductive cooling, while at low temperatures, where thioantimonites dominate, acidification of the fluid ( e.g. due to oxidation of H 2S) is the more likely mechanism. Precipitation of stibnite from fluids containing hydroxothioantimonite consumes H 2S and may thus trigger precipitation of other metals carried as sulfide complexes, e.g. Au(HS) − 2.