Pb, Cu botanogeochemical anomalies and toxic effects on plant cells in Pb-Zn （Sn） ore fields, Northeast Guangxi Autonomous Region, China

In the Lingchuan-Daoping and Xinglu Pb-Zn ore fields in northern and eastern Guangxi Autonomous Region, Pb, Cu botanogeochemical anomalies may be ascribed to the excessive amounts of Pb and Cu taken up by the root system of plants, such as China fir (Cunninghamia lanceolata Lamb. Hook), mason pine (Pinus massoniana Lamb.) and bracken fern (Pteridium aquilinum var. latiusculum). Under transmission electron microscope (TEM), the excess Pb, Cu in the leaf cells of the plants are present as high electron-density substances, which were precipitated in the leaf cells, causing phytotoxic effects by deforming and injuring cellular tissues. The sorts of toxic elements accumulating in the leaf cells are consistent with those of the botanogeochemically anomalous elements in the polluted soil where the plants grow. In addition, the plants may also be capable of resisting the invasion of excess Cu (and Pb) .     

Soil heavy-metal speciation and wheat phytotoxicity in the vicinity of an abandoned lead–zinc mine in Shangyu City,eastern China

Sixteen soil samples were collected from the vicinity of an abandoned lead–zinc mine in Shangyu City, eastern China, and the heavy-metal speciation and wheat phytotoxicity in the soils were studied. The results showed that the concentrations of free Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were highly variable and ranged from <0.01 to 0.32, 0.06 to 10.62, <0.01 to 1.40 and 0.02 to 37.10 μmol l⁻¹, respectively. The concentrations of soluble Cu, Zn, Cd and Pb ranged from 0.38 to 3.24, 0.72 to 78.74, <0.01 to 1.95 and 0.15 to 639.34 μmol l⁻¹, respectively. The general trend of mean solid/liquid partition coefficient and percentage of free metal ion to total soluble metal concentration were Cu > Pb > Zn > Cd and Cd > Zn > Cu > Pb, respectively. Stepwise multiple linear regression with pH, log(total metal) and log(organic matter) showed that log(total metal) was an important factor that controlled log(free metal ion) and log(soluble metal). Of the variability in log(free Cu²⁺), log(free Cd²⁺) and log(free Pb²⁺), 55.2, 58.6 and 64.3% could be explained by log(total Cu), log(total Cd) and log(total Pb) alone, respectively. Of the variability in log(soluble Cu) and log(soluble Cd), 77.1 and 72.5% could be explained by log(total Cu) and log(total Cd) alone, respectively. Wheat root length was controlled by the various metals with different free and soluble concentrations, and 99.2% of the variability in root length could be explained by concentrations of free and soluble Pb, soluble Cu and total Zn in the soils.     

Contrasting water–rock interaction behaviors of antimony and arsenic in contaminated rivers around an antimony mine,Hunan Province,China

Although antimony (Sb) and arsenic (As) exhibit similar geochemical behavior and toxicity in the environment, growing evidence suggests that their water–rock interaction behavior in contaminated rivers is quite different. Twenty-nine river water samples were collected between September and November 2018 from contaminated rivers around an antimony mine in Hunan Province, China. The concentrations of As and Sb were inversely proportional to the water flow distance. The rates and magnitudes of Sb decrease were more prominent than those of As. Silicate mineral dissolution from rocks such as silicified limestone increased the As and Sb concentration of in-mine-district (IMD) water. Dissolution of carbonate minerals, ion exchange, and competitive adsorption were the major water–rock interactions, resulting in rapidly decreasing As and Sb concentration in IMD direct impacted water and IMD indirect impacted water. The behaviors of As and Sb during water–rock interaction were dissimilar for areas dominated by carbonate and silicate minerals.     

Ore-forming material sources of the Jurassic Cu–Pb–Zn mineralization in the Qin–Hang ore belt,South China: Constraints from S–Pb isotopes

The Qin–Hang ore belt in South China, which serves as the boundary between the Yangtze and Cathaysia blocks, is marked by extensive Jurassic porphyry-skarn-metasomatic Cu–Pb–Zn polymetallic mineralization. In this contribution, S and Pb isotopic compositions of the Baoshan Cu–Pb–Zn deposit in the western portion of the Qin–Hang ore belt were analyzed to determine the ore-forming material sources in the area. This is coupled by the first systematic collection, compilation and interpretation of previously published S and Pb isotopic data of multiple sulfide minerals to reveal the metal origin and accumulation mechanism of the Cu–Pb–Zn mineralization from the significant deposits in the region (i.e., Dexing, Qibaoshan, Shuikoushan, Baoshan, Huangshaping, Tongshanling and Dabaoshan). The results show that Cu mineralization is characterized by low and narrow δ³⁴S (‰) range of values (–5 to 6) and Pb isotopic ratios (²⁰⁸Pb/²⁰⁴Pb = 38.0–39.0, ²⁰⁷Pb/²⁰⁴Pb = 15.4–15.8, and ²⁰⁶Pb/²⁰⁴Pb = 17.7–18.7), which are consistent with those of local porphyries. In contrast, the Pb–Zn mineralization reveals higher and more variable δ³⁴S (‰) values (–4 to 18) and Pb isotopic ratios (²⁰⁸Pb/²⁰⁴Pb = 38.0–39.5, ²⁰⁷Pb/²⁰⁴Pb = 15.3–16.0, and ²⁰⁶Pb/²⁰⁴Pb = 18.0–19.0) that correspond to wall-rock and basement rock compositions in the region. This indicates that the sulfur and lead that formed the Cu mineralization in the Qin–Hang ore belt was mainly sourced from regional magmatism with mantle contributions, whereas the sulfur and lead for the Pb–Zn mineralization was likely derived from the host sedimentary rocks and Proterozoic metamorphic basement rocks, respectively. The S and Pb isotopic data, combined with the geochemical signatures of mineralization-related porphyries, suggest that the Cu was sourced from the deeper levels along with mantle-derived magmas. In contrast, the Pb–Zn probably originated from the crust, with partial melting of the crystalline basement in the Cathaysia Block. Consequently, a three-stage genetic model is proposed to explain the ore-forming processes of the Qin–Hang Cu-polymetallic belt in South China.     

Metallegenesis of the Nongtun Large-scale Pb–Zn Deposit in Guangxi, South China: a Preliminary Study on the Fluid Inclusion

Please refer to the attachment(s) for more details.     

Re–Os dating of molybdenite and in-situ Pb isotopes of sulfides from the Lamo Zn–Cu deposit in the Dachang tin-polymetallic ore field,Guangxi, China

The Dachang tin-polymetallic district, Guangxi, China, is one of the largest tin ore fields in the world. Both cassiterite-sulfide and Zn–Cu skarn mineralization are hosted in the Mid-Upper Devonian carbonate-rich sediments adjacent to the underlying Cretaceous Longxianggai granite (91–97 Ma). The Lamo Zn–Cu deposit is a typical skarn deposit in the district and occurs at the contact zone between the Upper Devonian limestone and the granite. The ore minerals mainly consist of sphalerite, arsenopyrite, pyrrhotite, galena, chalcopyrite, and minor molybdenite. However, the age of mineralization and source of the metals are not well constrained. In this study, we use the molybdenite Re–Os dating method and in-situ Pb isotopes of sulfides from the Lamo deposit for the first time in order to directly determine the age of mineralization and the tracing source of metals. Six molybdenite samples yielded a more accurate Re–Os isochron age of 90.0 ± 1.1 Ma (MSWD = 0.72), which is much younger than the reported garnet Sm–Nd isochron age of 95 ± 11 Ma and quartz fluid inclusions Rb–Sr isochron age of 99 ± 6 Ma. This age is also interpreted as the age of Zn–Cu skarn mineralization in the Dachang district. Further, in this study we found that in-situ Pb isotopes of sulfides from the Lamo deposit and feldspars in the district’s biotite granite and granitic porphyry dikes have a narrow range and an overlap of Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.417–18.594, ²⁰⁷Pb/²⁰⁴Pb = 15.641–15.746, and ²⁰⁸Pb/²⁰⁴Pb = 38.791–39.073), suggesting that the metals were mainly sourced from Cretaceous granitic magma.     

Sediment-hosted Pb–Zn deposits in the Tethyan domain from China to Iran: Characteristics,tectonic setting,and ore controls

The Tethyan domain from China to Iran hosts many important sediment-hosted Pb–Zn deposits but most have been poorly documented. This study summarizes the salient features of these deposits and discusses the type of ore, tectonic setting, and important ore controls, on the basis of new geological observations and previous publications. The Tethyan domain is characterized by the young and extensive Himalayan–Tibetan and Zagros orogens that formed through collisions between the India/Arabia and Eurasia continents since the Late Cretaceous or early Cenozoic. Abundant Mississippi Valley-type (MVT) and subordinate clastic-dominated (CD, also known as SEDEX) Pb–Zn deposits occur in this domain, including in central and eastern Himalayan–Tibetan orogen in China, the Indian passive margin in southern Pakistan, and various tectonic units of Iran. Economically important deposits contain 0.1–21 Mt Pb + Zn and have total metal resources of ∼75 Mt with ∼48% being oxidized ores. All major deposits known in this domain are MVTs (i.e., the Jinding, Huoshaoyun, Mehdiabad, and Angouran deposits).Mississippi Valley-type Pb–Zn deposits occur in continental-collision-related fold-and-thrust belts and forelands, where deposits are mostly located on the margin of the Eurasian continent, with some in the Indian and Arabian continental margins. Clastic-dominated Pb–Zn deposits occur in central Iran and southern Pakistan, hosted by deep-water siliciclastic sequences of the early Cambrian rifted continental margin of Gondwana and the Jurassic passive continental margin of India, respectively. The youngest mineralized rocks and ages constrain that some important MVT deposits (e.g., the Jinding, Chaqupacha, and Angouran deposits) were formed after a main phase of regional compression, during a regional, large-scale strike-slip or crustal-extension stage in a continental collision setting. In sense of lithologic structure, important ore controls for MVT deposits include evaporite diapir structure, carbonate/evaporite dissolution–collapse structure, pre-existing barite, and porous dolostone. Much of the primary sulfide ore in this domain has been oxidized by supergene processes. This is particularly pronounced in the newly discovered Huoshaoyun deposit, where almost all sulfides have been oxidized to smithsonite and cerussite. An understanding of tectonic setting, ore controls, and supergene processes is essential in exploring for MVT deposits in this domain.     

Zircon U–Pb Geochronology of Baiyingaolao Formation from the Hadayingzi Region in the southern Great Xing’an Range, Northeast China

Blueschists in the Yilan area, Heilongjiang Province, are known as important parts of the Heilongjiang Complex. However, their metamorphic evolution history is still unclear. Petrographical, and mineral chemical investigations on the blueschists from the Yilan area are carried out in this study. P‐T pseudosections are calculated in the system Na₂O‐CaO‐K₂O‐MnO‐FeO‐MgO‐Al₂O₃‐SiO₂‐H₂O‐TiO₂‐O (Fe₂O₃) (NCKMnFMASHTO) with the PERPLE_X software for three blueschist samples. Peak metamorphic conditions are estimated to be 500‐525°C, 1.14‐1.2 GPa for garnet‐barroisite schist (g‐brs‐wnc‐act‐phn‐chl‐ep‐ab‐stlp); 480°C, 1.4 GPa for chlorite‐epidote glaucophane schist (gl‐brs‐wnc‐act‐chl‐ep‐stlp) and 450‐500°C, 0.95‐1.2 GPa for phengite‐glaucophane schist (gl‐wnc‐phn‐ab‐ep‐chl‐sph), which indicate that they all underwent peak metamorphism in the limit epidote‐blueschist facies conditions. Combined with the previously reported geochemical and geochronological data, the clockwise P‐T paths of the blueschists are constructed. The formation of blueschists in the study area marks the young oceanic crust subduction, and represents the final closure of the Paleo‐Asian Ocean and the beginning of the Paleo‐Pacific tectonic system. The P‐T pseudosection recorded the P‐T increasing process before the metamorphic peak and that the maximum temperature was coincident with the maximum pressure in the process, which indicates that the epidote‐blueschist facies conditions implemented in the process of subduction, rather than exhumation. The retrograde trajectory nearly coincidently retraced the prograde trajectory, which represents the similar geothermal gradient (11‐14°C/km) in the subduction and the relatively slow exhumation process.     

The genesis of metal zonation in the Weilasituo and Bairendaba Ag–Zn–Pb–Cu–(Sn–W) deposits in the shallow part of a porphyry Sn–W–Rb system,Inner Mongolia,China

The Weilasituo and Bairendaba Zn–Pb–Ag–Cu–(Sn–W) sulphide deposits are located in the southern part of Great Xing'an Range of Inner Mongolia in China. The deposits are located at shallow depths in the newly discovered Weilasituo porphyry hosting Sn–W–Rb mineralization. The mineralization at Weilasituo and Bairendaba consist of zoned massive sulphide veins within fractures cutting the Xilinhot Metamorphic Complex and quartz diorite. The Weilasituo deposit gradually zones from the Cu-rich Zn–Cu sulphide mineralization in the west to Zn-rich Zn–Cu sulphide mineralization in the east. The Bairendaba deposit has a Cu-bearing and Zn-rich core through a transitional zone devoid of copper to an outer zone of Zn–Pb–Ag mineralization. Three main veins contain more than 50 wt.% of the contained metal in the two deposits with their metal ratios displaying a systematic and gradual increase in Zn/Cu, Pb/Zn and Ag/Zn ratios from the western part of Weilasituo to the eastern part of Bairendaba.Three stages of vein-type mineralization are recognized. Early, sub-economic mineralization consists of a variable proportion of euhedral arsenopyrite, pyrite, quartz, and rare wolframite, scheelite, cassiterite, magnetite and cobaltite. This was succeeded by main stage mineralization with economic concentration of zoned Cu, Zn, Pb and Ag sulphide minerals along strike within the veins. The zones consist of the assemblages: (1) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–quartz–fluorite) at west Weilasituo; (2) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) at east Weilasituo; (3) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) in the centre of Bairendaba; (4) pyrrhotite–Fe-rich sphalerite–galena(–chalcopyrite–tetrahedrite–quartz–fluorite) in the transition zone of Bairendaba; and (5) pyrrhotite–Fe-rich sphalerite–galena–tetrahedrite(–chalcopyrite–falkmanite–argentite–pyrargyrite–quartz–fluorite) in the outer zone at Bairendaba. Post-main ore stage is devoid of sulphides and characterized overprinting of fluorite, sericite, chlorite, illite, kaolinite and calcite.Zircon SHRIMP U–Pb dating, Zircon LA–ICP–MS U–Pb dating, molybdenite Re–Os isochron dating, and muscovite Ar–Ar dating indicate the Beidashan granitic batholith was intruded at 140 ± 3 Ma (MSWD = 3.3), the porphyritic monzogranite from marginal facies of the Beidashan batholith was intruded at 139 ± 2 Ma (MSWD = 0.75), the mineralized quartz porphyry was intruded at 135 ± 2 Ma (MSWD = 0.91), the greisen mineralization occurred at 135 ± 11 Ma (MSWD = 7.2), and the post-main ore stage muscovite deposited at 129.5 ± 0.9 Ma. The new geochronology data show the porphyry Sn–W–Rb and vein-type sulphide mineralization are contemporaneous with granitic magmatism in the region.The metal zonation at the Weilasituo and Bairendaba deposits is a result of progressive metal deposition. This was during the evolution of a metal-bearing fluid along the strike of the veins and during the main stage of ore formation at the upper part of the deep-seated porphyry Sn–W–Rb system. This progressive zonation indicates that the deposits represent end-numbers formed from one ore-forming fluid, which moved from west to east from the porphyry. The metal zonation patterns of the major veins are consistent with metal-bearing fluid entering the system with the precipitation of chalcopyrite proximally and sphalerite, galena and Ag-bearing minerals more distally. We show that the mechanism of metal deposition is therefore controlled by thermodynamic conditions resulting in the progressive separation of sulphides from the metal-bearing fluid. The temperature gradient between the inflow zone and the outflow zone appears to be one of the key parameters controlling the formation of the metal zonation pattern. The sulphide precipitation sequence is consistent with a low fS₂ and low fO₂ state of the acidic metal-bearing fluid. The metal zonation pattern provides helpful clues from which it is possible to establish the nature of fluid migration and metal deposition models to locate a possible porphyry mineralization at depth in the Great Xing'an Range, which is consistent with the geology of the newly discovered porphyry Sn–W–Rb system.     

A porphyry-skarn metallogenic system in the Lesser Xing’an Range,NE China: Implications from U–Pb and Re–Os geochronology and Sr–Nd–Hf isotopes of the Luming Mo and Xulaojiugou Pb–Zn deposits

The Luming porphyry Mo deposit and the Xulaojiugou skarn Pb–Zn deposit are located in the southeast Lesser Xing’an Range, NE China. They are about 15 km apart, and are both related to monzogranite. Mo orebodies in the Luming deposit are hosted within the medium- to fine-grained monzogranite, while Pb–Zn orebodies in the Xulaojiugou deposit are hosted by the contact zone between the medium-grained monzogranite and the marbles of the early Cambrian Qianshan Formation.LA-ICP-MS zircon U–Pb dating of the ore-related monzogranite in the Luming deposit yields crystallization age of 180.7 ± 1.6 Ma, and the medium-grained and porphyritic monzogranites from the Xulaojiugou deposit yield crystallization ages of 181.2 ± 1.1 Ma and 179.9 ± 1.0 Ma, respectively. Analyses of seven molybdenite samples from the Luming deposit display Re–Os isochron age of 177.9 ± 2.6 Ma. These results indicate that the mineralization in the Luming and Xulaojiugou deposits occurred at about 181–178 Ma. These two deposits are genetically linked and belong to a porphyry-skarn metallogenic system. Combined with the previously reported geochronological data for ore deposits in adjacent areas, we consider that the early Jurassic is an important epoch for Mo and Pb–Zn mineralization in the Lesser Xing’an Range.The monzogranites from the Luming and Xulaojiugou deposits are enriched in and Rb, Th, U, Pb and light rare earth elements (LREEs), and are depleted in Ba, Nb, Ta, P, Ti and Eu. They have positive ε_Hf(t) values of 1.0–4.0 with two-stage Hf model ages (T_DM2) of 868–1033 Ma. Whole-rock Sr and Nd isotopes show restricted ranges of initial compositions, with (⁸⁷Sr/⁸⁶Sr)_i between 0.706346 and 0.707384 and ε_Nd(t) between −3.5 and −1.8. These data indicate that their primary magmas originated from the partial melting of a depleted lithospheric mantle which had been metasomatized by subducted slab-derived fluids/melts. The early Jurassic magmatic–metallogenic events in the Lesser Xing’an Range are interpreted as a response to the subduction of the Paleo-Pacific Plate.     

Geology,fluid inclusion,and stable isotope study of the skarn-related Pb–Zn (Cu–Fe–Sn) polymetallic deposits in the southern Great Xing’an Range,China: implications for deposit type and metallogenesis

In recent decades, several skarn-related deposits have been found and explored in the southern Great Xing’an Range of China. To get a clear understanding of the characteristics and genetics of this type of deposit in this area, three of the largest, most typical, and most famous skarn-related deposits (Haobugao Pb–Zn deposit, Huanggang Sn–Fe polymetallic deposit, and Baiyinnuoer Pb–Zn deposit) are selected for systematically metallogenic study in this paper. The results of ore geology, fluid inclusion, and stable isotopes indicate that (1) most of the ore bodies of each deposit, occurred in the outer contact zone of the magma intrusion and Permian strata, fine vein disseminated mineralization within the intrusions were also found in this study. Mineralization of these deposits all show closely temporal, spatial, and genetic relationships with skarns. (2) Fluid inclusion petrography and microthermometry results show that the fluid inclusion assemblages developed in the different mineralization stages of each deposit changed from Type-S (daughter mineral-bearing three-phase fluid inclusions) + Type-V (vapor-rich fluid inclusions) + Type-L (liquid-rich fluid inclusions) to Type-V + Type-L and eventually evolved into L-Type. Correspondingly, the ore-forming fluids changed from medium to a high-temperature, high-salinity, and boiling fluid system and then to a low-temperature, low-salinity, and uniform fluid system. The types of fluid inclusions in garnets are consistent with those in quartz phenocrysts of Mesozoic granites, indicating that the formation of skarns is directly related to Mesozoic magmatic activity. (3) The δ³⁴S values of ores from the above three deposits all exhibit a narrow variation range (changes are mainly around 0‰) and greatly differ from the SEDEX-type deposits in China. The lead isotope compositions of the sulfide minerals are also consistent with those of Mesozoic granites. These previous characteristics suggest that both of the ore-forming fluids and the ore-forming materials were of magmatic origin. Consequently, the Haobugao, Baiyinnuoer, and Huanggang deposits are all skarn-type deposits, which are related to Mesozoic magmatic activities in terms of ore geology features, ore-forming fluids, and ore-forming material.     

Using stable isotopes (δD, δ<Superscript>18</Superscript>O, δ<Superscript>34</Superscript>S and <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr) to identify sources of water in abandoned mines in the Fengfeng coal mining district,northern China

With depleted coal resources or deteriorating mining geological conditions, some coal mines have been abandoned in the Fengfeng mining district, China. Water that accumulates in an abandoned underground mine (goaf water) may be a hazard to neighboring mines and impact the groundwater environment. Groundwater samples at three abandoned mines (Yi, Er and Quantou mines) in the Fengfeng mining district and the underlying Ordovician limestone aquifer were collected to characterize their chemical and isotopic compositions and identify the sources of the mine water. The water was HCO₃·SO₄-Ca·Mg type in Er mine and the auxiliary shaft of Yi mine, and HCO₃·SO₄-Na type in the main shaft of Quantou mine. The isotopic compositions (δD and δ¹⁸O) of water in the three abandoned mines were close to that of Ordovician limestone groundwater. Faults in the abandoned mines were developmental, possibly facilitating inflows of groundwater from the underlying Ordovician limestone aquifers into the coal mines. Although the Sr²⁺ concentrations differed considerably, the ratios of Sr²⁺/Ca²⁺ and ⁸⁷Sr/⁸⁶Sr and the ³⁴S content of SO₄^2? were similar for all three mine waters and Ordovician limestone groundwater, indicating that a close hydraulic connection may exist. Geochemical and isotopic indicators suggest that (1) the mine waters may originate mainly from the Ordovician limestone groundwater inflows, and (2) the upward hydraulic gradient in the limestone aquifer may prevent its contamination by the overlying abandoned mine water. The results of this study could be useful for water resources management in this area and other similar mining areas.