Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Gui...Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.展开更多
Dexing copper deposit is the biggest porphyry copper deposit in China. By researching isotopes of C,Si and Cu from the samples of Tongchang and Fujiawu ore-field, the authors found that δ13CPDB values of siderite wer...Dexing copper deposit is the biggest porphyry copper deposit in China. By researching isotopes of C,Si and Cu from the samples of Tongchang and Fujiawu ore-field, the authors found that δ13CPDB values of siderite were close to the δ13CPDB value of original magma; δ30Si values of the samples at the ore-forming stage were close to the δ30Si value range of magma, δ30Si values of partial samples were far away from it; Cu isotopic compositions of massive chalcopyrite formed at the early ore-forming stage are higher than that of veinal chalcopyrite formed at the later ore-forming stage. The results show that ore-forming materials were mainly derived from the porphyry body, and part of them were from wall rock materials.展开更多
The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and...The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and the fine-grained materials were suggested to be derived from wind-blown dust.However,increasing evidence indicated that the REEs in the water-soluble portion of atmospheric depositions also displayed similar patterns to those of aeolian sediments.In this study,water-soluble REEs in three atmospheric depositions collected from different climatic zones in China were adsorbed with two adsorbents with distinct adsorption capacity,glass powder,and co-precipitated iron hydroxide.The results showed that the REEs adsorbed by the two adsorbents displayed patterns similar to those of the original atmospheric depositions.The typical characteristics of the REE patterns of atmospheric deposition can be well reproduced in the adsorbed REEs.The higher the REE concentrations in the atmospheric depositions,or the higher adsorption efficiency of the adsorbents,the better reproducibility of the REEs patterns.The results suggest that the REEs of the fine-grained materials in various sediments,which have a high adsorption capacity,especially those deposited in South China,may come from the water-soluble REEs in atmospheric deposition,and may not be appropriate tracers of wind-blown dust from North China.展开更多
The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb-（Zn） deposits ...The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb-（Zn） deposits around this intrusion. Those deposits are spatially associated with the Habo alkaline intrusion. （1） The δ^34S values of sulfides from Au deposits range from -1.91‰ to 2.69 ‰, which are similar to those of Pb-（Zn） deposits （-3.82 ‰ to -0.05 ‰） and both indicate a much greater contribution from magma. （2） The Habo alkaline intrusion has relatively homogeneous Pb isotopic compositions with ^206pb/^204pb ranging from 18.608 to 18.761, ^207pb/^204pb from 15.572 to 15.722 and ^20spb/^204pb from 38.599 to 39.110. These Pb isotope ratios are similar to those of Au deposits, whose ^206pb/^204pb range from 18.564 to 18.734, ^20Tpb/^20apb from 15.582 to 15.738 and ^208pb/^204pb from 38.592 to 39.319. Pb ratios in both the intrusion and Au deposits suggest that Pb mainly derived from the depth, probably represents a mixture of mantle and crust. Pb-（Zn） deposits, however, show a decentralized trait, and most of them are similar to that of the alkaline intrusion with ^206pb/^204pb ranging from 18.523 to 18.648, ^207pb/^204pb from 15.599 to 15.802, and ^20spb/^204pb from 38.659 to 39.206. （3） In the plumbotectonic diagram ^20Tpb/^204pb versus ^206pb/^204pb, almost all of Au and Pb-（Zn） deposits have the same projection area with the Habo alkaline intrusion, which indicates that those deposits almost share the same source with the alkaline intrusion. （4） Isotopic age of the Habo alkaline intrusion is 36-33 Ma, which is similar to that of Beiya, whose ore- related alkaline porphyries age is 38-31 Ma and molybdenite Re-Os age is 36.9 Ma. Therefore, along with S-Pb isotope traits, we suggest that the Habo Au and Pb-（Zn） deposits should be typically Ailaoshan-Red RiverCenozoicalkaline-related deposits and ore-forming ages of these deposits should be later than that of the Habo alkaline intrusion.展开更多
Quartz was studied with respect to its silicon isotopic composition and cathodoluminescence in micro-fine disseminated gold deposits in SW Guizhou and NW Guangxi. The resultsshowed that quartz in wall rocks, ores and ...Quartz was studied with respect to its silicon isotopic composition and cathodoluminescence in micro-fine disseminated gold deposits in SW Guizhou and NW Guangxi. The resultsshowed that quartz in wall rocks, ores and that in association with hydrothermal silicificationare distinctive in silicon isotopes and cathodoluminescence characters. Quartz in association withprimary silicification is non-luminescent while that in wall rocks and associated with secondarysilicification exhibits striking luminescence. Based on the dynamic fractionation of silicon isotopes, it is suggested that the mineralization was accompanied by rapid transport of a primarysiliceous fluid along the major deep fault system into subordinate faults before ore componentsdeposited in favorable strata via penetration and metasomatism. Therefore, a deep origin is implicit for gold deposits of this type.展开更多
文摘Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.
文摘Dexing copper deposit is the biggest porphyry copper deposit in China. By researching isotopes of C,Si and Cu from the samples of Tongchang and Fujiawu ore-field, the authors found that δ13CPDB values of siderite were close to the δ13CPDB value of original magma; δ30Si values of the samples at the ore-forming stage were close to the δ30Si value range of magma, δ30Si values of partial samples were far away from it; Cu isotopic compositions of massive chalcopyrite formed at the early ore-forming stage are higher than that of veinal chalcopyrite formed at the later ore-forming stage. The results show that ore-forming materials were mainly derived from the porphyry body, and part of them were from wall rock materials.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41473093 and 41271212)。
文摘The distribution patterns of rare earth elements(REEs)in fine-grained materials in various depositions were often found to be similar to those of the aeolian sediments deposited in the Loess Plateau in North China and the fine-grained materials were suggested to be derived from wind-blown dust.However,increasing evidence indicated that the REEs in the water-soluble portion of atmospheric depositions also displayed similar patterns to those of aeolian sediments.In this study,water-soluble REEs in three atmospheric depositions collected from different climatic zones in China were adsorbed with two adsorbents with distinct adsorption capacity,glass powder,and co-precipitated iron hydroxide.The results showed that the REEs adsorbed by the two adsorbents displayed patterns similar to those of the original atmospheric depositions.The typical characteristics of the REE patterns of atmospheric deposition can be well reproduced in the adsorbed REEs.The higher the REE concentrations in the atmospheric depositions,or the higher adsorption efficiency of the adsorbents,the better reproducibility of the REEs patterns.The results suggest that the REEs of the fine-grained materials in various sediments,which have a high adsorption capacity,especially those deposited in South China,may come from the water-soluble REEs in atmospheric deposition,and may not be appropriate tracers of wind-blown dust from North China.
文摘The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb-（Zn） deposits around this intrusion. Those deposits are spatially associated with the Habo alkaline intrusion. （1） The δ^34S values of sulfides from Au deposits range from -1.91‰ to 2.69 ‰, which are similar to those of Pb-（Zn） deposits （-3.82 ‰ to -0.05 ‰） and both indicate a much greater contribution from magma. （2） The Habo alkaline intrusion has relatively homogeneous Pb isotopic compositions with ^206pb/^204pb ranging from 18.608 to 18.761, ^207pb/^204pb from 15.572 to 15.722 and ^20spb/^204pb from 38.599 to 39.110. These Pb isotope ratios are similar to those of Au deposits, whose ^206pb/^204pb range from 18.564 to 18.734, ^20Tpb/^20apb from 15.582 to 15.738 and ^208pb/^204pb from 38.592 to 39.319. Pb ratios in both the intrusion and Au deposits suggest that Pb mainly derived from the depth, probably represents a mixture of mantle and crust. Pb-（Zn） deposits, however, show a decentralized trait, and most of them are similar to that of the alkaline intrusion with ^206pb/^204pb ranging from 18.523 to 18.648, ^207pb/^204pb from 15.599 to 15.802, and ^20spb/^204pb from 38.659 to 39.206. （3） In the plumbotectonic diagram ^20Tpb/^204pb versus ^206pb/^204pb, almost all of Au and Pb-（Zn） deposits have the same projection area with the Habo alkaline intrusion, which indicates that those deposits almost share the same source with the alkaline intrusion. （4） Isotopic age of the Habo alkaline intrusion is 36-33 Ma, which is similar to that of Beiya, whose ore- related alkaline porphyries age is 38-31 Ma and molybdenite Re-Os age is 36.9 Ma. Therefore, along with S-Pb isotope traits, we suggest that the Habo Au and Pb-（Zn） deposits should be typically Ailaoshan-Red RiverCenozoicalkaline-related deposits and ore-forming ages of these deposits should be later than that of the Habo alkaline intrusion.
文摘Quartz was studied with respect to its silicon isotopic composition and cathodoluminescence in micro-fine disseminated gold deposits in SW Guizhou and NW Guangxi. The resultsshowed that quartz in wall rocks, ores and that in association with hydrothermal silicificationare distinctive in silicon isotopes and cathodoluminescence characters. Quartz in association withprimary silicification is non-luminescent while that in wall rocks and associated with secondarysilicification exhibits striking luminescence. Based on the dynamic fractionation of silicon isotopes, it is suggested that the mineralization was accompanied by rapid transport of a primarysiliceous fluid along the major deep fault system into subordinate faults before ore componentsdeposited in favorable strata via penetration and metasomatism. Therefore, a deep origin is implicit for gold deposits of this type.
