The large-scale Qixiashan Pb-Zn Deposit in the eastern Middle-Lower Yangtze metallogenic belt is hosted in carbonate rocks.Based on a detailed mineral paragenesis study,in-situ LA-ICP-MS(laser ablation inductively cou...The large-scale Qixiashan Pb-Zn Deposit in the eastern Middle-Lower Yangtze metallogenic belt is hosted in carbonate rocks.Based on a detailed mineral paragenesis study,in-situ LA-ICP-MS(laser ablation inductively coupled plasma mass spectrometer)trace element geochemistry data for pyrite and sphalerite from different stages in the Qixiashan Deposit are reported,the Pb-Zn mineralization processes are reconstructed,and a genetic model is constructed.Four paragenetic stages of Pb-Zn ore deposition are identified:the biogenic pyrite mineralization stage(Stage 1),the early stage of hydrothermal Pb-Zn mineralization(Stage 2),the late stage of hydrothermal Pb-Zn mineralization(Stage 3),and the carbonate stage(Stage 4).Stages 2 and 3 are the main ore stages.The trace element characteristics of the sulfide in stages 2 and 3,such as the higher Co/Ni and lower trace element contents of the pyrite and the Fe,Mn,and Ge contents of the sphalerite,indicate that they were generated by magmatic-hydrothermal processes.Furthermore,the lower Cu,Ag,Sb,and Pb contents of the pyrite and sphalerite of Stage 3 compared to Stage 2 suggest an increase in magmatic-hydrothermal activity from Stage 2 to Stage 3.The hydrothermal fluids leached trace elements(e.g.,Cu,Ag,Sb,and Pb)from the previously deposited primary pyrite and sphalerite,which were precipitated in the later hydrothermal stage Cu,Au,Ag,Sb,and Pb bearing minerals and secondary pyrite and sphalerite with lower trace element contents(e.g.,Cu,Au,Ag,Sb,and Pb).Compared with the pyrite from stages 2 and 3,the Stage 1 pyrite has relatively higher trace elements contents(Sb,Cu,Zn,Au,Ag,Pb,As,and Ni).However,their lower Co/Ni ratio suggests a syngenetic sedimentary origin.Based on the petrographic features and trace element data,a multi-stage mineralization model is proposed.The Stage 1 biogenic pyrite formed stratiform pyrite layers,which provided reducing conditions and a base for the subsequent Pb-Zn mineralization.During Stage 2,subsequent hydrothermal fluid interacted with the stratiform pyrite layers,which resulted in sulfide precipitation and the formation of stratiform Pb-Zn orebodies.In Stage 3,the hydrothermal fluid replaced the limestone along the fractures,which triggered the formation of Pb-Zn vein orebodies.展开更多
The exploitation of metallic mines may cause serious environmental problems.The removal of the heavy metals from the contaminated mining environments has become an urgent issue.In this paper,the occurrence and distrib...The exploitation of metallic mines may cause serious environmental problems.The removal of the heavy metals from the contaminated mining environments has become an urgent issue.In this paper,the occurrence and distribution of heavy metals in the calcareous tufa collected from the mining laneway of the Qixiashan Pb-Zn Mine in Nanjing were investigated by using multiple mineralogical techniques.Examination by X-ray diffraction spectrum(XRD) shows that calcite is the major compo-nent of the calcareous tufa.Several heavy metals such as Mn,Zn,Mg,Fe and Pb are detected in calcite by means of electron microprobe analysis.Although the heavy metal contents in the hostrock and the formation water are significantly low,the contents of Mn,Zn,Mg,Fe and Pb in the tufa calcite are as high as 23.65 wt%,9.6 wt%,0.76 wt%,4.44 wt% and 0.66 wt%,respectively.The back-scattered electron image shows complex compositional zoning texture in the tufa,which is linked directly to varia-tions in heavy metals,particularly in Mn and Zn.In addition,we also observed floccule and helical precipitations,which may be derived from the metabolism of the microbe.It is deduced that the occurrence and high concentration of heavy metals in tufa may be controlled by the activities of microbes.The results presented in this work suggest that calcite will be an important candidate for the remediation of the heavy metal contamination in mining areas.展开更多
基金This study was supported by the National Natural Science Foundation of China(No.1212011220678)We are very grateful to Jiangsu East China Basic Geological Exploration Co.,Ltd.for providing basic geological data and assistance in the field.
文摘The large-scale Qixiashan Pb-Zn Deposit in the eastern Middle-Lower Yangtze metallogenic belt is hosted in carbonate rocks.Based on a detailed mineral paragenesis study,in-situ LA-ICP-MS(laser ablation inductively coupled plasma mass spectrometer)trace element geochemistry data for pyrite and sphalerite from different stages in the Qixiashan Deposit are reported,the Pb-Zn mineralization processes are reconstructed,and a genetic model is constructed.Four paragenetic stages of Pb-Zn ore deposition are identified:the biogenic pyrite mineralization stage(Stage 1),the early stage of hydrothermal Pb-Zn mineralization(Stage 2),the late stage of hydrothermal Pb-Zn mineralization(Stage 3),and the carbonate stage(Stage 4).Stages 2 and 3 are the main ore stages.The trace element characteristics of the sulfide in stages 2 and 3,such as the higher Co/Ni and lower trace element contents of the pyrite and the Fe,Mn,and Ge contents of the sphalerite,indicate that they were generated by magmatic-hydrothermal processes.Furthermore,the lower Cu,Ag,Sb,and Pb contents of the pyrite and sphalerite of Stage 3 compared to Stage 2 suggest an increase in magmatic-hydrothermal activity from Stage 2 to Stage 3.The hydrothermal fluids leached trace elements(e.g.,Cu,Ag,Sb,and Pb)from the previously deposited primary pyrite and sphalerite,which were precipitated in the later hydrothermal stage Cu,Au,Ag,Sb,and Pb bearing minerals and secondary pyrite and sphalerite with lower trace element contents(e.g.,Cu,Au,Ag,Sb,and Pb).Compared with the pyrite from stages 2 and 3,the Stage 1 pyrite has relatively higher trace elements contents(Sb,Cu,Zn,Au,Ag,Pb,As,and Ni).However,their lower Co/Ni ratio suggests a syngenetic sedimentary origin.Based on the petrographic features and trace element data,a multi-stage mineralization model is proposed.The Stage 1 biogenic pyrite formed stratiform pyrite layers,which provided reducing conditions and a base for the subsequent Pb-Zn mineralization.During Stage 2,subsequent hydrothermal fluid interacted with the stratiform pyrite layers,which resulted in sulfide precipitation and the formation of stratiform Pb-Zn orebodies.In Stage 3,the hydrothermal fluid replaced the limestone along the fractures,which triggered the formation of Pb-Zn vein orebodies.
基金Supported by National Basic Research Program of China (Grant No.2007CB815603)National Natural Science Foundation of China (Grant No.40573001)the Ph.D. Programs Foundation of Ministry of Education of China (Grant No.20050284044)
文摘The exploitation of metallic mines may cause serious environmental problems.The removal of the heavy metals from the contaminated mining environments has become an urgent issue.In this paper,the occurrence and distribution of heavy metals in the calcareous tufa collected from the mining laneway of the Qixiashan Pb-Zn Mine in Nanjing were investigated by using multiple mineralogical techniques.Examination by X-ray diffraction spectrum(XRD) shows that calcite is the major compo-nent of the calcareous tufa.Several heavy metals such as Mn,Zn,Mg,Fe and Pb are detected in calcite by means of electron microprobe analysis.Although the heavy metal contents in the hostrock and the formation water are significantly low,the contents of Mn,Zn,Mg,Fe and Pb in the tufa calcite are as high as 23.65 wt%,9.6 wt%,0.76 wt%,4.44 wt% and 0.66 wt%,respectively.The back-scattered electron image shows complex compositional zoning texture in the tufa,which is linked directly to varia-tions in heavy metals,particularly in Mn and Zn.In addition,we also observed floccule and helical precipitations,which may be derived from the metabolism of the microbe.It is deduced that the occurrence and high concentration of heavy metals in tufa may be controlled by the activities of microbes.The results presented in this work suggest that calcite will be an important candidate for the remediation of the heavy metal contamination in mining areas.
