The Jinmen copper deposit, which is situated on the northern margin of the Lanping-Simao back-arc basin, western Yunnan Province, is a silver-bearing, high-grade vein-typecopper deposit. Comprehensive element geochemi...The Jinmen copper deposit, which is situated on the northern margin of the Lanping-Simao back-arc basin, western Yunnan Province, is a silver-bearing, high-grade vein-typecopper deposit. Comprehensive element geochemical studies of the host rocks and hydrothermalminerals revealed the regularities in the distribution, mobilization and transport of elementsfrom the host rocks to hydrothermal minerals. In conunction with the fluid inclusion and isotope data, it is suggested that the ore-forming fluid was derived mainly from a deep sourcecharacterized by CO2 enrichment and reduction in nature. It is also suggested that the oreforming materials come largely from a deep sourcel although the contribution of the countryrocks should not be ruled out.It is also found that some hydrothermal minerals are possessed of MREE-enrichment patterns. It is deduced that the REEs in the deep-source ore fluid were transported in the form ofCO2-3 complexes and were deposited in a continental basin （or a hot-spring basin）.展开更多
The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits i...The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits in the orefield have been divided into seven major substyles according to their occurring positions and control factors.The ore-forming fluid inclusion styles in the orefield include those of two-phase fluid,liquid CO2-bearing three-phase and daughter mineral-bearing multi-phase.The homogenization temperatures range from 382° to 122℃,falling into five clusters of 370° to 390°,300° to 360°,230° to 300°,210° to 290° and 120° to 200°,and the clusters of 300° to 360°,230° to 300° and 120° to 200° are three major mineralization stages,with fluid salinity peaks from 4.14% to 7.31%,2.07% to 7.31% and 0.53% to 3.90%,respectively.The ore-forming fluids are mainly type of NaCl-H2O with medium to high density （0.74-1.02 g/cm3）,or CO2-bearing NaCl-H2O with medium to low density （0.18-0.79 g/cm3）.The fluid salinity and density both show a decline tendency with decreasing temperature.According to the measurement and calculation of Hand O-isotopic compositions in the quartz of the quartz-sulfide veins,δDV-SMOW of the ore-forming fluid is from-84‰ to-54‰,and δ18OV-SMOW of that is from 6.75‰ to 9.21‰,indicating a magmatic fluid.The δ34SV-CDT of sulfides in the ores fall into two groups,one is from-4.4‰ to 2.2‰ with average of-1.42‰,and the other from 18.8‰ to 21.6‰ with average of 19.8‰.The S-isotopic data shows one peak at-4.4‰ to 2.2‰ （meaning-1.42‰） suggesting a simple magmatic sulfur source.The ore Pbisotopic ratios are 206pb/204pb from 17.817 to 17.983,207pb/204pb from 15.470 to 15.620 and 208pb/204pb from 38.072 to 38.481,indicating characteristics of mantle-derived lead.The data show that the major ore deposits in the orefield have a magmatic-hydrothermal genesis and that the SHRIMP zircon age of the granodiorite porphyry,closely related to the mineralization,is 151.2±4.2 Ma （MSWD =1.3）,which can represent the formation ages of the ores and intrusion rocks.The study aids understanding of the ore-forming processes of the major metallic ore deposits in the orefield.展开更多
Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing ...Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements（LREE;159.556 ppm） and lower HREE（12.108 ppm）.TheΣLREE/ΣHREE ratio is 12.612 and（La/Yb）_N is 11.765.These indicate that pyrite is rich in LREE.The（La/Sm）_N ratio is 3.758 and that of（Gd/Yb）_N is 1.695.These are obvious LREE fractionations.The rare earth element（REE） distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks（regional metamorphic rocks）,but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio（average value 0.38） of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with Cl〉F.展开更多
Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little at...Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little attention. Oil yield, major element, trace element, rare earth element, and total sulfur （TS） data from the oil shale within the Yanchang are here presented and discussed in the context of hydrothermal influence. Oil shale samples returned relatively high total organic carbon （TOC）, in the range of 4.69%-25.48%. A high correlation between TS and TOC suggests TS in the oil shale is dominated by organic sulfur and affected by organic matter. The low Al/ Si ratio of oil shale samples implies quartz is a major mineralogical component. Si/（Si ＋ Al ＋ Fe） values suggest close proximity of the oil shale to a terrigenous source. δEu; Fe versus Mn versus （Cu ＋ Co ＋ Ni）× 10; and SiO2/（K2O ＋ Na2O） versus MnO/TiO2, Fe/Ti, and （Fe ＋ Mn）/Ti are evidence of hydrothermal fluid activity during oil shale sedimentation, and δU and U/Th of the oil shale indicate reducing conditions. The Sr/Ba of oil shale samples suggests fresh-water deposition. The high correlations of Fe/Ti and （Fe ＋ Mn）/Ti with δU, U/Th, and TS demonstrate that hydrothermal fluid activity promotes reducing conditions. Sr/Ba ratios had low correlation with Fe/Ti and （Fe ＋ Mn）/Ti, implying that hydrothermal fluid activity had little impact （Fe ＋ Mn）/Ti, δU, U/Th, and on paleosalinity. Fe/Ti, Cu ＋ Pb ＋ Zn all exhibited high positive correlation coefficients with TOC in oil shale samples, suggesting that more intense hydrothermal fluid activity improves conditions in favor of formation and preservation of organic matter.展开更多
Major and trace elements are presented for the late Paleozoic radiolarian cherts, which were spatially associated with the NE Jiangxi ophiolite melange. These chert samples show relatively low SiO2 (78.40%-89.28%) and...Major and trace elements are presented for the late Paleozoic radiolarian cherts, which were spatially associated with the NE Jiangxi ophiolite melange. These chert samples show relatively low SiO2 (78.40%-89.28%) and high Al2O3 (3.42%-11.02%). Low Si/Al ratios (6.3-23) and tight negative correlation between Si/Al and Al2O3 of the samples indicate that they are muddy cherts containing high and variable contents of pelitic detritus. Geochemically, they are characterized by Al2O3/(Al2O3+Fe2O3) = 0.51-0.90, shale-normalized Lan/Cen = 0.76-1.11, Ce/Ce* = 0.91-1.22, V<20μg/g, V/Y<2.6 and Ti/V>40, resembling those of cherts formed in the continental margin regimes. It is therefore concluded that these late Paleozoic radiolarian muddy cherts were most likely formed in a continental margin regime, and not genetically related to the ophiolite suite in NE Jiangxi. It is also unlikely that an oceanic basin existed between the Yangtze and Cathaysia blocks during the late Paleozoic.展开更多
文摘The Jinmen copper deposit, which is situated on the northern margin of the Lanping-Simao back-arc basin, western Yunnan Province, is a silver-bearing, high-grade vein-typecopper deposit. Comprehensive element geochemical studies of the host rocks and hydrothermalminerals revealed the regularities in the distribution, mobilization and transport of elementsfrom the host rocks to hydrothermal minerals. In conunction with the fluid inclusion and isotope data, it is suggested that the ore-forming fluid was derived mainly from a deep sourcecharacterized by CO2 enrichment and reduction in nature. It is also suggested that the oreforming materials come largely from a deep sourcel although the contribution of the countryrocks should not be ruled out.It is also found that some hydrothermal minerals are possessed of MREE-enrichment patterns. It is deduced that the REEs in the deep-source ore fluid were transported in the form ofCO2-3 complexes and were deposited in a continental basin （or a hot-spring basin）.
基金financially supported jointly by the National Key Basic Research Program (Grant 2012CB416704) from the Ministry of Science and Technology, Chinathe Program of High-level Geological Talents (201309) and Youth Geological Talents (201112) from the China Geological Surveyby Geological Survey Program Grant 1212010561603-2 from the China Geological Survey
文摘The Yinkeng orefield in Yudu County,Jiangxi Province,SE China,is a zone of concentrated Au-Ag-Pb-Zn-Cu-Mn polymetallic ores.Based on summing up basic geology and ore geology of the orefieid,the polymetallic deposits in the orefield have been divided into seven major substyles according to their occurring positions and control factors.The ore-forming fluid inclusion styles in the orefield include those of two-phase fluid,liquid CO2-bearing three-phase and daughter mineral-bearing multi-phase.The homogenization temperatures range from 382° to 122℃,falling into five clusters of 370° to 390°,300° to 360°,230° to 300°,210° to 290° and 120° to 200°,and the clusters of 300° to 360°,230° to 300° and 120° to 200° are three major mineralization stages,with fluid salinity peaks from 4.14% to 7.31%,2.07% to 7.31% and 0.53% to 3.90%,respectively.The ore-forming fluids are mainly type of NaCl-H2O with medium to high density （0.74-1.02 g/cm3）,or CO2-bearing NaCl-H2O with medium to low density （0.18-0.79 g/cm3）.The fluid salinity and density both show a decline tendency with decreasing temperature.According to the measurement and calculation of Hand O-isotopic compositions in the quartz of the quartz-sulfide veins,δDV-SMOW of the ore-forming fluid is from-84‰ to-54‰,and δ18OV-SMOW of that is from 6.75‰ to 9.21‰,indicating a magmatic fluid.The δ34SV-CDT of sulfides in the ores fall into two groups,one is from-4.4‰ to 2.2‰ with average of-1.42‰,and the other from 18.8‰ to 21.6‰ with average of 19.8‰.The S-isotopic data shows one peak at-4.4‰ to 2.2‰ （meaning-1.42‰） suggesting a simple magmatic sulfur source.The ore Pbisotopic ratios are 206pb/204pb from 17.817 to 17.983,207pb/204pb from 15.470 to 15.620 and 208pb/204pb from 38.072 to 38.481,indicating characteristics of mantle-derived lead.The data show that the major ore deposits in the orefield have a magmatic-hydrothermal genesis and that the SHRIMP zircon age of the granodiorite porphyry,closely related to the mineralization,is 151.2±4.2 Ma （MSWD =1.3）,which can represent the formation ages of the ores and intrusion rocks.The study aids understanding of the ore-forming processes of the major metallic ore deposits in the orefield.
基金supported by the National Natural Science Foundation of China(No. 40373025)
文摘Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements（LREE;159.556 ppm） and lower HREE（12.108 ppm）.TheΣLREE/ΣHREE ratio is 12.612 and（La/Yb）_N is 11.765.These indicate that pyrite is rich in LREE.The（La/Sm）_N ratio is 3.758 and that of（Gd/Yb）_N is 1.695.These are obvious LREE fractionations.The rare earth element（REE） distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks（regional metamorphic rocks）,but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio（average value 0.38） of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with Cl〉F.
基金supported with funding from the National Natural Science Foundation of China (No. 41173055)the Fundamental Research Funds for the Central Universities (No. 310827172101)
文摘Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little attention. Oil yield, major element, trace element, rare earth element, and total sulfur （TS） data from the oil shale within the Yanchang are here presented and discussed in the context of hydrothermal influence. Oil shale samples returned relatively high total organic carbon （TOC）, in the range of 4.69%-25.48%. A high correlation between TS and TOC suggests TS in the oil shale is dominated by organic sulfur and affected by organic matter. The low Al/ Si ratio of oil shale samples implies quartz is a major mineralogical component. Si/（Si ＋ Al ＋ Fe） values suggest close proximity of the oil shale to a terrigenous source. δEu; Fe versus Mn versus （Cu ＋ Co ＋ Ni）× 10; and SiO2/（K2O ＋ Na2O） versus MnO/TiO2, Fe/Ti, and （Fe ＋ Mn）/Ti are evidence of hydrothermal fluid activity during oil shale sedimentation, and δU and U/Th of the oil shale indicate reducing conditions. The Sr/Ba of oil shale samples suggests fresh-water deposition. The high correlations of Fe/Ti and （Fe ＋ Mn）/Ti with δU, U/Th, and TS demonstrate that hydrothermal fluid activity promotes reducing conditions. Sr/Ba ratios had low correlation with Fe/Ti and （Fe ＋ Mn）/Ti, implying that hydrothermal fluid activity had little impact （Fe ＋ Mn）/Ti, δU, U/Th, and on paleosalinity. Fe/Ti, Cu ＋ Pb ＋ Zn all exhibited high positive correlation coefficients with TOC in oil shale samples, suggesting that more intense hydrothermal fluid activity improves conditions in favor of formation and preservation of organic matter.
文摘Major and trace elements are presented for the late Paleozoic radiolarian cherts, which were spatially associated with the NE Jiangxi ophiolite melange. These chert samples show relatively low SiO2 (78.40%-89.28%) and high Al2O3 (3.42%-11.02%). Low Si/Al ratios (6.3-23) and tight negative correlation between Si/Al and Al2O3 of the samples indicate that they are muddy cherts containing high and variable contents of pelitic detritus. Geochemically, they are characterized by Al2O3/(Al2O3+Fe2O3) = 0.51-0.90, shale-normalized Lan/Cen = 0.76-1.11, Ce/Ce* = 0.91-1.22, V<20μg/g, V/Y<2.6 and Ti/V>40, resembling those of cherts formed in the continental margin regimes. It is therefore concluded that these late Paleozoic radiolarian muddy cherts were most likely formed in a continental margin regime, and not genetically related to the ophiolite suite in NE Jiangxi. It is also unlikely that an oceanic basin existed between the Yangtze and Cathaysia blocks during the late Paleozoic.
