The Southern Great Xing’an Range (SGXR) which forms part of the eastern segment of the Central Asian Orogenic Belt (CAOB) is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a ...The Southern Great Xing’an Range (SGXR) which forms part of the eastern segment of the Central Asian Orogenic Belt (CAOB) is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a number of porphyry Mo (Cu),skarn Fe (Sn),epithermal Au-Ag,and hydrothermal veintype Ag-Pb-Zn ore deposits.Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR.Porphyry Sn ±Cu ± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field.We identify a five-stage mineralization process based on field and petrologic studies including (i) the early porphyry mineralization stage,(ii) main porphyry mineralization stage,(iii) transition mineralization stage,(iv) vein-type mineralization stage and (v) late mineralization stage.Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage,and we identify corresponding four types of pyrites: Py1 is medium-grained subhedral to euhedral occurring in the early barren quartz vein;Py2 is medium- to fine-grained euhedral pyrite mainly coexisting with molybdenite,chalcopyrite,minor sphalerite and galena;Py3 is fine-grained,subhedral to irregular pyrite and displays cataclastic textures with micro-fractures;Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena.LA-ICP-MS trace element analyses of pyrite show that Cu,Pb,Zn,Ag,Sn,Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions,whereas Co,Ni,As and Se enter the lattice via isomorphism in all types of pyrite.The Cu,Zn,Ag,Cd concentrations gradually increase from Py1 to Py4,which we correlate with cooling and mixing of ore-forming fluid with meteoric water.Py2 contains the highest contents of Co,Ni,Se,Te and Bi,suggesting high temperature conditions for the porphyry mineralization stage.Ratios of Co/Ni (0.03-10.79,average 2.13) and sulphur isotope composition of sulfide indicate typical hydrothermal o展开更多
Major elements, trace elements and Sr isotopic compositions of apatite from the granite in the Chengchao skarn-type Fe deposit of Edong ore district of Middle-Lower Yangtze River metallogenic belt were measured using ...Major elements, trace elements and Sr isotopic compositions of apatite from the granite in the Chengchao skarn-type Fe deposit of Edong ore district of Middle-Lower Yangtze River metallogenic belt were measured using EMPA （electron microprobe）, LA-ICP-MS （laser ablation inductively coupled plasma mass spectrometer） and LA-MC （multicollector）-ICP-MS methods in order to reveal the petroge- netic and metallogenic significance of the skarn-type iron deposits. The results show that the apatite in Chengchao granite is fluorapatite, which displays slight variation in major elements. The REE distribution pattern of the apatite is similar to that of the whole rocks, with strong negative Eu anomaly and low Sr/Y ratio. The concentration of Mn in apatite is low （140 ppm-591 ppm） and the Sr isotopic composition shows a limited variation from 0.706 9 to 0.708 2. The high oxygen fugacity of the Chengchao granite, implied by the low Mn content in apatite, is possibly attributed to contamination of the gypsum from sedimentary rock strata, which has long been thought to be an important factor that controls the Fe mineralization in the Middle-Lower Yangtze River metallogenic bell This study also proves that the Eu/Eu＊ value and Sr/Y ra- tio in apatite can be effectively used to identify the adakitie affinity. The in situ Sr isotope analysis of apatite is in consistent with the bulk rock analysis, which indicates that the apatite Sr isotope can represent the ini- tial Sr isotopic compositions of the magma. The Sr isotope and negative Eu anomaly in apatite imply that the Chengchao granite is likely sourced from crust-mantle mixed materials.展开更多
基金financially supported by National Key Research and Development Program of China (2016YFC0600504)Fundamental Research Funds for the Central Universities (2652017218)
文摘The Southern Great Xing’an Range (SGXR) which forms part of the eastern segment of the Central Asian Orogenic Belt (CAOB) is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a number of porphyry Mo (Cu),skarn Fe (Sn),epithermal Au-Ag,and hydrothermal veintype Ag-Pb-Zn ore deposits.Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR.Porphyry Sn ±Cu ± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field.We identify a five-stage mineralization process based on field and petrologic studies including (i) the early porphyry mineralization stage,(ii) main porphyry mineralization stage,(iii) transition mineralization stage,(iv) vein-type mineralization stage and (v) late mineralization stage.Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage,and we identify corresponding four types of pyrites: Py1 is medium-grained subhedral to euhedral occurring in the early barren quartz vein;Py2 is medium- to fine-grained euhedral pyrite mainly coexisting with molybdenite,chalcopyrite,minor sphalerite and galena;Py3 is fine-grained,subhedral to irregular pyrite and displays cataclastic textures with micro-fractures;Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena.LA-ICP-MS trace element analyses of pyrite show that Cu,Pb,Zn,Ag,Sn,Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions,whereas Co,Ni,As and Se enter the lattice via isomorphism in all types of pyrite.The Cu,Zn,Ag,Cd concentrations gradually increase from Py1 to Py4,which we correlate with cooling and mixing of ore-forming fluid with meteoric water.Py2 contains the highest contents of Co,Ni,Se,Te and Bi,suggesting high temperature conditions for the porphyry mineralization stage.Ratios of Co/Ni (0.03-10.79,average 2.13) and sulphur isotope composition of sulfide indicate typical hydrothermal o
基金supported by the National Key R & D Program of China (No. 2016YFC0600206)the China Geological Survey (No. 12120114051801)
文摘Major elements, trace elements and Sr isotopic compositions of apatite from the granite in the Chengchao skarn-type Fe deposit of Edong ore district of Middle-Lower Yangtze River metallogenic belt were measured using EMPA （electron microprobe）, LA-ICP-MS （laser ablation inductively coupled plasma mass spectrometer） and LA-MC （multicollector）-ICP-MS methods in order to reveal the petroge- netic and metallogenic significance of the skarn-type iron deposits. The results show that the apatite in Chengchao granite is fluorapatite, which displays slight variation in major elements. The REE distribution pattern of the apatite is similar to that of the whole rocks, with strong negative Eu anomaly and low Sr/Y ratio. The concentration of Mn in apatite is low （140 ppm-591 ppm） and the Sr isotopic composition shows a limited variation from 0.706 9 to 0.708 2. The high oxygen fugacity of the Chengchao granite, implied by the low Mn content in apatite, is possibly attributed to contamination of the gypsum from sedimentary rock strata, which has long been thought to be an important factor that controls the Fe mineralization in the Middle-Lower Yangtze River metallogenic bell This study also proves that the Eu/Eu＊ value and Sr/Y ra- tio in apatite can be effectively used to identify the adakitie affinity. The in situ Sr isotope analysis of apatite is in consistent with the bulk rock analysis, which indicates that the apatite Sr isotope can represent the ini- tial Sr isotopic compositions of the magma. The Sr isotope and negative Eu anomaly in apatite imply that the Chengchao granite is likely sourced from crust-mantle mixed materials.
