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The Yangla Cu skarn deposit is located in the central part of the Jinshajiang Suture Zone, southwest China, with a total reserve of 150 Mt Cu @ 1.03%. The newly discovered antimony orebodies at the depth of Yangla are strictly controlled by the stratum, structure, and lithology, which are lenticular and vein-like within the marble fracture zone, which can provide a window into multistage mineralization and ore genesis at Yangla. Mineralization can be divided into three types, Cu–Pb–Zn (skarn) pyrite, galena, and sphalerite, Cu (porphyry) chalcopyrite and pyrite, and Sb (hydrothermal) stibnite and pyrite. The mineral assemblages were stibnite + pyrite + calcite + quartz ± minor scheelite in antimony ores. This study presents quantitative measurements of the trace element compositions of pyrite and stibnite from the Yangla antimony ores. Analysis of pyrite with electron probe microanalysis (EPMA) showed enrichment in Co, Ni, Sb, As, and Mo, and deficit in its S and Fe contents when compared to the stoichiometric concentrations of S and Fe in pyrite. The Sb-related pyrite may belong to sedimentary-reworked genesis and may be modified by hydrothermal fluids, thereby presenting a certain difference (i.e., crystal morphology, texture, and chemical composition) compared to the skarn and porphyry Cu-related pyrite in the Yangla Cu skarn deposit. Analysis of stibnite with EPMA and inductively coupled plasma-mass spectrometry showed enrichment in As, Pb, Sn, Pb, Cu, and Zn, and presented much higher Sb contents and slightly lower S contents when compared to the stoichiometric concentrations of Sb and S in stibnite. Statistical analysis of the stibnite trace elements showed correlations for the elemental pairs Cu–Pb, As–Sb, and Sn–Pb, and the coupled substitution equations Sb3+ ↔ Cu+ + Pb2+, Sb3+ ↔ As3+, and Sn2+ ↔ Pb2+ may be the major factors governed the incorporating Cu, Pb, As and Sn within the stibnite. Moreover, this study preliminary shows that the antimony mineralization may belong to a carbonate replacement hydrothermal genesis at Yangla. [ABSTRACT FROM AUTHOR]

Pyrite, the most common sulfide mineral, is a ubiquitous component of many hydrothermal gold deposits. Geochemical patterns within the refractory pyrite structure represent a valuable repository of information that can help constrain the sources of ore-forming materials, and the evolution of ore-forming processes over time. However, there are still a lot of debates on the mechanisms of physico-chemical processes in ore-forming fluid controlling trace element and sulfur isotope distributions in pyrite during growth. In our manuscript, we use cutting-edge complementary microanalytical methods to understand the origin and evolution of zoned gold-bearing pyrite in samples from the largest gold deposit in the Ailaoshan gold belt, SW China, Zhenyuan (exceeding 100t Au, average grade: 5.3 g/t). Pyrite, arsenopyrite, chalcopyrite, and stibnite are the most abundant sulfide minerals in most orebodies. Of these, pyrite is dominant and is also the most important host for gold. Two types of pyrite can be clearly distinguished: framboidal pyrite and hydrothermal pyrite. Gold is most commonly hosted by hydrothermal pyrite. Framboidal pyrite, mainly hosted by carbonaceous slate, hosts negligible Au, and features low δ34S values ranging from − 35.0 (± 0.9) to − 25.6 (± 1.0)‰. Hydrothermal pyrite is characterized by complex intra-grain zoned textures with alternating As-rich and As-poor bands readily recognizable on backscattered electron images. Scanning electron microscopy and trace-element analyses show that both visible and invisible gold occur only in the As-rich bands. Compared to the As-poor bands (72.1% of Au concentration data < 1.96 ppm, n = 43), the As-rich bands are characterized by far higher concentrations of Au (up to 1420 ppm), Cu, Ag, Sb, and Tl, but lower concentrations of Co and Ni. In-situ sulfur isotope analysis indicates that the δ34S values of As-rich zones range from − 7.3 (± 0.6) to 2.9 (± 0.6)‰ and are similar to those of As-poor zones (from − 6.9 (± 0.7) to 2.8 (± 0.6)‰), but distinct from the framboidal pyrite. Combined with published fluid inclusion data and a probable age for the magmatic event associated with mineralization, these data suggest that magmatic–hydrothermal fluids contributed most ore-forming materials and that periodic boiling led to formation of the rhythmic As-rich and As-poor bands in pyrite. Our data for pyrite constrain the evolution of ore-forming processes and provide new insights into the formation of zoned pyrite, with the conclusions having broad implications for analogous hydrothermal gold deposits worldwide. [ABSTRACT FROM AUTHOR]

The Gongguan deposit in southern Qinling district, central China, is characterized by a Hg and Sb metal association, with proven reserves of 7,543 t Hg and 17,100 t Sb. The Hg-Sb mineralized veins are primarily hosted by local Lower Devonian dolomite. Three primary paragenetic stages have been identified, including (I) pyrite-dolomite-quartz, (II) stibnite-cinnabar-quartz-calcite and (III) post-ore calcite. Dominant mercury and antimony mineralization occurred in stage II. Fluid inclusion microthermometry of quartz and calcite reveal that the Hg-Sb mineralization is associated with a low temperature (142° to 240 °C) and low salinity (< 8.6 wt% NaCl equivalent) fluid, belonging to a H2O-NaCl ± CO2 system. The H–O isotope compositions (δDH2O = −84 to −63‰, δ18OH2O = 1.3 to 12.7‰) of the hydrothermal fluid suggest a mixture of metamorphic fluid and meteoric water. In situ sulfur isotope results of cinnabar (δ34S = 3.4 to 14.5‰), stibnite (δ34S = 4.9 to 10.5‰) and pyrite (δ34S = 3.8 to 5.4‰) indicate sulfur sources from decomposition of diagenetic pyrite and/or the thermochemical sulfate reduction in local sedimentary rocks. In situ obtained 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios (18.006 to 18.362, 15.445 to 15.610 and 37.871 to 38.288, respectively) of stibnite and pyrite substantially differ from those for the regional Carlin Au-Sb and SEDEX Pb–Zn ore deposits. The lead isotope results indicate that the underlying Paleozoic (Silurian to Cambrian) strata and Precambrian metamorphic basement supplied substantial metals for the studied Hg-Sb deposit, whereas the host Devonian carbonates did not contribute significant metals. In summary, we propose that fluid mixing between metamorphic fluid and meteoric water was the main cause for carbonate-hosted Hg-Sb deposition at Gongguan, which reduced the stibnite solubility, oxidized mercury (Hg0 to Hg2+), favoring the process of dedolomitization. [ABSTRACT FROM AUTHOR]

To systematically study the environmental problems of heavy metal pollution in soils caused by antimony (Sb) smeltery in central and southern China, the pollution levels, sources and risks of heavy metals were explored based on the GIS, pollution indices, multivariate statistical methods combined with positive matrix factorization (PMF) model, and risk assessment model. The results showed the average contents of Hg, Pb, Cd, Cr, As, and Sb in soils were 0.06, 47.77, 2.88, 53.12, 21.22 and 20.53 mg/kg, respectively. Except for Hg and Cr, the contents of other metals all exceeded the background values of Hunan Mountain soil (BV). Spatial distribution of heavy metal contents and pollution indices (Igeo, PLI, and RI) indicated that above 50% of the studied area were polluted moderately by Cd and Sb, and 77% of sampling sites were under a severe ecological risk level. Multivariate statistics and PMF analysis suggested that Cd (76.9%) and As (57.7%) were mainly from agricultural activities, followed by Sb smelting (12.7% for Cd and 25% for As). The atmosphere deposition of transportation and industrial activities, antimony smelting and nature origin respectively contributed 40.6%, 20.5% and 30.7% of Hg in soils. Sb (73.9%) and Pb (54.5%) were from the Sb smelting, followed by the high geological background (35.6% for Pb and 25% for Sb). Cr (69.7%) was natural origin, but agricultural activities had 21.6% of contribution to its accumulation in soils. Significantly, the values of non-carcinogenic risk (HI) for children under three exposure pathways in different soil depths was bigger than 1 and exceeded the "acceptable level" of risk, and the total carcinogenic risks (TCR) for adults and children were exceeded 1 × 10–4 with an unacceptable carcinogenic risk for human body. Oral ingestion of As was the remarkable characteristic of risk, which should be paid attention to. [ABSTRACT FROM AUTHOR]

Antimony pollution in the groundwater of the Xikuangshan (XKS) antimony (Sb) mine area in China's Hunan Province has attracted increasing attention. A total of 43 water samples were collected to help understand the hydrogeochemical characteristics, identify the Sb source, and evaluate the water–rock interactions of the Shetianqiao aquifer (SA). The Sb concentrations in shallow and deep SA water samples were 0.1–47.4 mg L−1 and 0.3–19.2 mg L−1, respectively. Stibnite oxidation and leaching from arsenic alkali residue mine wastes were the main Sb sources for the shallow SA water, whereas stibnite oxidation and stronger water–rock interaction were the predominant Sb sources for the deep SA water. The higher Sb concentration (> 10.0 mg L−1) in shallow SA water was predominantly induced by weathering of Sb-bearing minerals, evaporation/concentration effects, and cation exchange, whereas the higher Sb concentration in deep SA water was largely caused by weathering of Sb-bearing minerals, evaporation/concentration effects, ion exchange, and competitive adsorption. These findings provide a more detailed understanding of the geochemical behavior of Sb in groundwater and can be used to develop suitable Sb pollution management strategies. [ABSTRACT FROM AUTHOR]