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The native gold in the Woxi Au–Sb–W deposit is characterized by remarkably high purities (99.9%), called as super-pure native gold. The deposit can thus be used as the suitable application example for analyzing ore-forming conditions by using the thermodynamic calculation of AuxAg1 – x-fluid equilibria. According to experimental results of minerals and fluid inclusions, some physicochemical conditions are assumed in the thermodynamic calculation of the fluids equilibrated with Au–Ag solid solutions of XAu = 0.999. Calculated results in log fO2-pH diagrams show dissolved gold and silver concentrations, as well as stability fields of pyrite and sericite associated with the super-pure native gold. On the other hand, LA-ICP-MS analysis indicates that both Au and Ag concentration are determined in the fluid inclusions of scheelite, showing varied Au/Ag ratios with different homogenization temperatures. The calculated results assumed by different data of inclusions in scheelite, indicate two fluid inclusions showing higher homogenization temperatures (303°C and 356°C) and higher Au/Ag ratios are possible for precipitation of the super-pure native gold coexisting with pyrite and sericite, whereas one fluid inclusion showing a lower homogenization temperature (198°C) and a lower Au/Ag ratio is impossible for the super-pure native gold. Therefore, the super-pure native gold in the Woxi deposit was probably formed by the hydrothermal fluid with higher Au/Ag ratios and high temperatures in the mineralization stage of scheelite. [ABSTRACT FROM AUTHOR]

Both essential and toxic metal contaminants impact agricultural crops by bioaccumulation in plants. The goal of this study was to evaluate the tissue-level spatial distribution of metal(loids) in corn seeds (Zea mays, L.) from contaminated corn fields near the Xikuangshan (XKS) antimony mine in Hunan, China, and compared them with corn (Zea mays everta L., popcorn) grown in a farm in Amherst, MA that practices sustainable farming as a control. How toxic and essential metals translocate through the roots and shoots during early stages of germination was also investigated. The cleaned corn seed samples were mounted in resin blocks and longitudinally dissected into thin sections. The laser ablation parameters were optimized, and the instrument was calibrated using tomato leaf standard reference material (NIST SRM 1573a) in a pellet form. Tissue level distributions of metal(loid)s As, Cd, Hg, Sb and Zn in corn seeds collected were determined using (LA-ICP-MS). Seeds from the control farm were germinated and their roots and shoots were analyzed to determine tissue level concentrations and their spatial distributions. It was found that seeds from the XKS mine region in China had higher overall concentration of all elements analyzed due to metal(loids) absorbed from contaminated mine soils. Metal(loids) concentrations were highest in the embryo (∼360 mg/kg) and pericarp (∼0.48 mg/kg) compared with the endosperm of corn seeds. Essential element Zn was found in the embryo and emerging coleoptile and radicle. Finally, in both roots and shoots, element concentrations were highest proximally to the tip cap compared to distal concentrations and later translocated to distal tissue regions. This study offers unique insights of metal(loid) bioaccumulation and translocation in corn and thus is better able to track metal(loids) contaminants trafficking in our food systems. Image 1 • Essential element Zn is concentrated in the embryo and pericarp of corn seeds. • As, Cd, and Sb levels are higher in corn seeds from contaminated mining soils. • Toxic metalloids are readily translocated into coleoptile and radicle in the seed. • LA-ICP-MS offers unique insights of metal(loid) translocation during germination. • Milling is helpful to remove accumulated toxic elements in corn seed's pericarp. Tissue level spatial distribution of toxic metal(loid)s shows bioaccumulation in embryo and pericarp in corn seeds while they translocate to germinating shoot and roots. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spherite from Huangshaping is the main carrier mineral of dispersed elements (Ga, In, Cd). • In sphalerite, the replacement methods of Ge, Ga, and In are Ge4++2Cu+↔3Zn2+, and In3+(Ga3+) + Cu+↔2Zn2+. • Sphalerite was formed in a medium–high temperature environment (288 ∼ 341 °C). • The Pb-Zn mineralization in Huangshaping is caused by late-stage hydrothermal fluid which is related to the skarn mineralization process. The Huangshaping copper-polymetallic deposit, which is located in southern Hunan Province, China, is an important resource base for Pb–Zn minerals. This study used the major sulfides (sphalerite, pyrite, pyrrhotite), which formed during the Pb–Zn mineralization stage of the Huangshaping deposit, to determine the genesis of the Pb–Zn ore minerals and element occurrence. In-situ LA-ICP-MS analysis of minerals was conducted to determine their trace element concentrations and reveal the distribution and occurrence of trace elements in different sulfides. The formation temperature and genesis of the Pb–Zn ore minerals were also constrained based on the deposit geology and trace element data. Trace elements were significantly different among different sulfides in the Pb–Zn mineralization stage of the deposit. Sphalerite primarily enriches Mn, Cu, Ag, Sn, and Pb and is the main carrier mineral of Ga, In, and Cd. Pyrite relatively enriches Tl, Sb, W, and Se, and pyrrhotite primarily enriches Ge. In sphalerite, Fe, Mn, Cd, Ga, In, Cu, Sn, Ag, and Ge exist by substituting for other elements (such as Zn). The replacement method of Ge is Ge4++2Cu+↔3Zn2+, whereas that of In (Ga) is In3+(Ga3+) + Cu+↔2Zn2+. In pyrrhotite, Ge is incorporated through coupling substitution, and the abnormal concentrations of Pb, Ag, and Se are caused by galena that has replaced pyrrhotite. In pyrite, W occurs as a solid solution. When galena replaces pyrite, it causes abnormal concentrations of Pb, Tl, Sb, and Ag. The sphalerite is characterized by high concentrations of high-temperature ore-forming elements (e.g., Fe, Mn, In, and Sn) and relatively low concentrations of Cd, Ge, Ga, and other elements. Thus, the sphalerite was formed at a medium–high temperature (288–341 °C). The trace element characteristics of sphalerite are consistent with those of high-temperature hydrothermal deposits. The deposit geology, pyrite Co/Ni ratio (averaging 0.13, n = 29), S/Se ratio (averaging 173,905, n = 19), pyrrhotite Co/Ni ratio (averaging 0.10, n = 26), and binary diagram of trace elements in sphalerite indicate that Pb–Zn mineralization is related to the late-stage hydrothermal activity of skarn mineralization. The Pb–Zn mineralization and W–Mo(Fe) mineralization together constitute a skarn-type mineralization system. [ABSTRACT FROM AUTHOR]

Past pollution episodes and the intensity of mining activity in a contaminated region can be unraveled, using archived elemental information in tree rings. Elemental dendrochronology can be utilized with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to make a timeline of metal(loid)s uptake in trees. In this study, six tree core samples from five tree species were collected around the XKS antimony mine region in Hunan, China, which is impacted by metal pollution: NM1 shuitong (Camptotheca acuminate L.), M1 shuitong (Camptotheca acuminate L.), G1 xiangchun (Toona sinensis L.), J2 wutong (Firmiana platanifolia L.), BSN kulian (Melia azedarach L.), and MT1 zhang (Cinnamomum camphora L.). Tree cores were dated by counting annual rings, and concentrations of As, Ca, Pb, Sb, and Zn were determined using LA-ICP-MS. Results demonstrate that the highest concentrations of Sb are present in the areas closer to mining activity: NM1 - north mine (shuitong), MT1 - mine tailing site (zhang), and BSN - between south and north mine (kulian) tree cores have average Sb concentrations of 18.8 mg/kg, 13 mg/kg, and 4.8 mg/kg, respectively. In comparison, at the village sites located farther away from the mining areas, G1 xiangchun, J2 wutong, and M1 shuitong have average Sb concentrations of 0.69 mg/kg, 0.57 mg/kg, and 0.66 mg/kg, respectively. NM1 shuitong, G1 xiangchun, and MT1 zhang all have large Sb and Zn peaks around 1986, while BSN kulian has larger Sb peaks slightly later around 1988–1990. J2 wutong has Sb peaks somewhat earlier, at 1977 and 1980. Unlike the others trees, M1 shuitong has greater Sb concentrations in more recent years (2009, 2015–2016) demonstrating Sb pollution. Image 1 • Elemental peaks reveal Sb and Zn pollution is noticeable during 1986–1990. • Antimony levels are elevated in trees near the north mine and mine tailing pond. • Average tree core Sb levels ranged from 18.8 to 4.8 mg/kg near mine sites. • LA-ICP-MS is an elegant analytical method for elemental dendrochronology. Capsule: Elemental dendrochronology of trees reveals historic Sb and Zn pollution and elemental uptake (i.e. Ca) in XKS mining district, Hunan, China. [ABSTRACT FROM AUTHOR]