The Middle-Lower Yangtze River Metallogenic Belt(MLYB)is known to contain abundant copper and iron porphyry-skarn deposits,with an increasing number of tungsten deposits and scheelite in Fe-Cu deposits being discovere...The Middle-Lower Yangtze River Metallogenic Belt(MLYB)is known to contain abundant copper and iron porphyry-skarn deposits,with an increasing number of tungsten deposits and scheelite in Fe-Cu deposits being discovered in the MLYB during recent decades.The ore genesis of the newly-discovered tungsten mineralization in the MLYB is poorly understood.We investigate four sets of scheelite samples from tungsten,iron and copper deposits,using CL imaging and LA-ICP-MS techniques to reveal internal zonation patterns and trace element compositions.The REE distribution patterns of four studied deposits show varying degrees of LREE enrichment with negative Eu anomalies.The oxygen fugacity of ore-forming fluid increased in Donggushan,while the oxygen fugacity of ore-forming fluid decreased in Ruanjiawan,Guilinzheng and Gaojiabang.The scheelites from the Donggushan,Ruanjiawan,Guilinzheng and Gaojiabang deposits show enrichment in LREEs and HFSE,with Nb/La ratios ranging from 1.217 to 52.455,indicating that the four tungsten deposits are enriched in the volatile fluorine.A plot of(La/Lu)N versus Mo/δEu can be used to distinguish quartz vein type,porphyry and skarn tungsten deposits.This study demonstrates that scheelite grains can be used to infer tungsten mineralization and are effective in identifying magmatic types of tungsten deposits in prospective mining sites.展开更多
Determining the precise timing of mineralization and mineralizing events is crucial to understanding regional mineralizing and other geological events and processes.However,there are a number of mineralogical and anal...Determining the precise timing of mineralization and mineralizing events is crucial to understanding regional mineralizing and other geological events and processes.However,there are a number of mineralogical and analytical limitations to the approaches developed for the absolute dating of mineralizing systems,such as molybdenite Re-Os and zircon and garnet U-Pb,among others.This means that the precise and accurate dating of mineralizing systems that may not contain minerals suitable for dating using existing approaches requires the development of new(and ideally in situ)approaches to absolute dating.This study outlines a new in situ analytical approach that has the potential to rapidly and accurately evaluate the timing of ore formation.Our study employs a novel application of in situ scheelite U-Pb dating analysis using laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)and samples from the Qiaomaishan deposit,a representative example of skarn mineralization within the Xuancheng ore district of eastern China.Our approach to scheelite dating of the deposit is verified by cross-comparison to dating of cogenetic garnet and apatite,proving the effectiveness of this approach.Our new approach to dating of scheelite-bearing geological systems is rapid,cheap,requires little sample preparation,and is undertaken in situ,allowing crucial geological and mineralogical context to be retained during analysis.The approaches outlined here not only allow the determination of the absolute timing of formation of the Qiaomaishan deposit through the U-Pb dating of scheelite[138.6±3.2 Ma,N=39,mean square weighted deviation(MSWD)=1.17],garnet(138.4±1.0 Ma,N=40,MSWD=1.3),and apatite(139.6+3.3 Ma,N=35,MSWD=0.72),but also further supports the theoretical genetic links between this mineralization and the emplacement of a proximal porphyritic granodiorite intrusion(zircon U-Pb age:139.5±1.2 Ma,N=23,MSWD=0.3).Moreover,our research indicates that the higher the concentrations of U within scheelite,the more suitable that scheelite is for U-Pb dating,with the main factor controlling the U content of scheelite seemingly being variations in oxygen fugacity conditions.This novel approach provides a potentially powerful tool,not just for the dating of skarn systems but also with potential applications in orogenic and intrusion-related gold,porphyry W-Mo,and greisen mineralizing systems as well as other scheelite-bearing geological bodies or geological systems.展开更多
The Magushan skarn Cu-Mo deposit is a representative example of the skarn mineralization occurring within the Xuancheng ore district of the Middle-Lower Yangtze River Metallogenic Belt of eastern China.The precise age...The Magushan skarn Cu-Mo deposit is a representative example of the skarn mineralization occurring within the Xuancheng ore district of the Middle-Lower Yangtze River Metallogenic Belt of eastern China.The precise age of an ore deposit is important for understanding the timing of mineralization relative to other geological events in a region and to fully place the formation of a mineral deposit within the geological context of other processes that occur within the study area.Here,we present new molybdenite Re-Os and titanite and andradite garnet U-Pb ages for the Magushan deposit and use these data to outline possible approaches for identifying genetic relationships in geologically complex areas.The spatial and paragenetic relationships between the intrusions,alteration,and mineralization within the study area indicates that the formation of the Magushan deposit is genetically associated with the porphyritic granodiorite.However,this is not always the case,as some areas contain complexly zoned plutons with multiple phases of intrusion or mineralization may be distal from or may not have any clear spatial relationship to a pluton.This means that it may not be possible to determine whether the mineralization formed as a result of single or multiple magmatic/hydrothermal events.As such,the approaches presented in this study provide an approach that allows the identification of any geochronological relationships between mineralization and intrusive events in areas more complex than the study area.Previously published zircon U-Pb data for the mineralization-related porphyritic granodiorite in this area yielded an age of 134.2±1.2 Ma(MSWD=1.4)whereas the Re-Os dating of molybdenite from the study area yielded an isochron age of 137.7±2.5 Ma(MSWD=0.43).The timing of the mineralizing event in the study area was further examined by the dating of magmatic accessory titanite and skarn-related andradite garnet,yielding U-Pb ages of 136.3±2.5 Ma(MSWD=3.2)and 135.9±2.7 Ma(MSWD=2.5),respectively.The dating of magmatic and hydrothermal activity within the Magushan area yields ages around 136 Ma,strongly suggesting that the mineralization in this area formed as a result of the emplacement of the intrusion.The dates presented in this study also provide the first indication of the timing of mineralization within the Xuancheng district.providing evidence of a close genetic relationship between the formation of the mineralization within the Xuancheng district and the Early Cretaceous magmatism that occurred in this area.This in turn suggests that other Early Cretaceous intrusive rocks within this region are likely to be associated with mineralization and should be considered highly prospective for future mineral exploration.This study also indicates that the dating of garnet and titanite can also provide reliable geochronological data and evidence of the timing of mineralization and magmatism,respectively,in areas lacking other dateable minerals(e.g.,molybdenite)or where the relationship between mineralization and magmatism is unclear,for example in areas with multiple stages of magmatism,with complexly zoned plutons,and with distal skarn mineralization.展开更多
Magmatic microgranular enclaves(MMEs)are widely developed in the Shaocunwu granodiorite at the northeast margin of the eastern Jiangnan orogenic belt.Field geology showed that the MMEs occur as irregular ellipsoids ne...Magmatic microgranular enclaves(MMEs)are widely developed in the Shaocunwu granodiorite at the northeast margin of the eastern Jiangnan orogenic belt.Field geology showed that the MMEs occur as irregular ellipsoids near the edge of the intrusion,and consist of diorite,dominantly composed of amphibole,biotite,and plagioclase grains,with minor acicular apatite.Zircon U-Pb dating showed the ages of the host granodiorites and MMEs are 145.9±1.1 Ma and 145.6±2.5 Ma,respectively,indicating both originated during coeval late Jurassic magmatism.Whole-rock geochemical results show that the host granodiorite and MMEs have similar rare earth and trace element partition curves in spider grams,and similar 87Sr/86Sr,and 147Nd/144Nd isotope ratios,and their zircon 177Hf/176Hf isotopic ratios are similar.Geochemical studies indicate that both the host granodiorite and MMEs formed by mixing of coeval magma.Zircon Ti thermometers and oxygen fugacity of the host granodiorite and the MMEs show high oxygen fugacity,similar to that of W-Cu(Mo)mineralized granitoids in the eastern Jiangnan orogenic belt.A similar magma mixing process was probably one of the mechanisms that generated the W-Cu(Mo)fertile melts.展开更多
Introduction to the Middle-Lower Yangtze River Valley Metallogenic Belt The Middle-Lower Yangtze River Valley metallogenic belt(MLYB)has been a cradle of modern metallogeny in China.In the MLYB,there are numerous stra...Introduction to the Middle-Lower Yangtze River Valley Metallogenic Belt The Middle-Lower Yangtze River Valley metallogenic belt(MLYB)has been a cradle of modern metallogeny in China.In the MLYB,there are numerous stratabound sulfide deposits and polymetallic skarn-porphyry and magnetite-apatite deposits,together constituting a significant mineralogic exploration belt on the northern margin of the Yangtze craton.The deposit metallogenic series(Cheng et al.,1979),the metallogenic system(Zhai,1999),a porphyritic iron metallogenic model(Ningwu Iron Ore Research Group,1978),the continental fault depression belt in a syngenetic submarine copper deposit(Gu and Xu,1986),stratabound skarn(Chang et al.,1991)and the Mesozoic large-scale metallogenic explosion(Pan and Dong,1999;Mao et al.,1999)in the MLYB have been described and reviewed in detail.The Middle to Lower Yangtze region has been one of the main targets of research and exploration since the early period of geological work in China since the middle 20th century,Chang et al.(1991),Zhai et al.(1992),Tang et al.(1998)and other researchers have made a full review of the achievements before the 1990s.In the 21st century,much further research work has been carried out in the MLYB.Chang et al.(2012,2017,2019),Mao et al.(2011,2012),Pirajno and Zhou(2015),Xie et al.展开更多
0 INTRODUCTION Granite-related uranium deposits are one of the most important types of uranium deposits in South China,and their genetic model generally involves uranium leaching from the preexisting rocks(mainly gran...0 INTRODUCTION Granite-related uranium deposits are one of the most important types of uranium deposits in South China,and their genetic model generally involves uranium leaching from the preexisting rocks(mainly granites),U transport as uranyl carbonate and fluoride complexes and probably chloride complexes in hydrothermal solutions,and U precipitation caused by physicochemical changes(Chi et al.,2020;Hu et al.,2008).Mineralization ages of granite-related uranium deposits in South China have been a subject of significant controversy among researchers and were investigated using several methods,such as bulk uraninite U-Pb isotopic dating,in situ analytical techniques,pyrite Rb-Sr dating as well as bulk uraninite Sm-Nd dating(e.g.,Zhang et al.,2022;Zhong et al.,2019;Bonnetti et al.,2018;Luo et al.,2015;Huang et al.,2010;Ye,2005).展开更多
基金funded by grants from the National Key Research and Development Program(2016YFC0600206)the National Natural Science Foundation of China(41872081)+1 种基金the Doctoral initial funding project of Anhui Jianzhu University(2019QDZ33)the Anhui Province Science and Technology Plan Project for Housing Urban-rural Construction(2020-YF35)。
文摘The Middle-Lower Yangtze River Metallogenic Belt(MLYB)is known to contain abundant copper and iron porphyry-skarn deposits,with an increasing number of tungsten deposits and scheelite in Fe-Cu deposits being discovered in the MLYB during recent decades.The ore genesis of the newly-discovered tungsten mineralization in the MLYB is poorly understood.We investigate four sets of scheelite samples from tungsten,iron and copper deposits,using CL imaging and LA-ICP-MS techniques to reveal internal zonation patterns and trace element compositions.The REE distribution patterns of four studied deposits show varying degrees of LREE enrichment with negative Eu anomalies.The oxygen fugacity of ore-forming fluid increased in Donggushan,while the oxygen fugacity of ore-forming fluid decreased in Ruanjiawan,Guilinzheng and Gaojiabang.The scheelites from the Donggushan,Ruanjiawan,Guilinzheng and Gaojiabang deposits show enrichment in LREEs and HFSE,with Nb/La ratios ranging from 1.217 to 52.455,indicating that the four tungsten deposits are enriched in the volatile fluorine.A plot of(La/Lu)N versus Mo/δEu can be used to distinguish quartz vein type,porphyry and skarn tungsten deposits.This study demonstrates that scheelite grains can be used to infer tungsten mineralization and are effective in identifying magmatic types of tungsten deposits in prospective mining sites.
基金the National Natural Science Foundation of China(Grant Nos.41820104007,91962218)and the China Scholarship Council(Grant No.201906690036).
文摘Determining the precise timing of mineralization and mineralizing events is crucial to understanding regional mineralizing and other geological events and processes.However,there are a number of mineralogical and analytical limitations to the approaches developed for the absolute dating of mineralizing systems,such as molybdenite Re-Os and zircon and garnet U-Pb,among others.This means that the precise and accurate dating of mineralizing systems that may not contain minerals suitable for dating using existing approaches requires the development of new(and ideally in situ)approaches to absolute dating.This study outlines a new in situ analytical approach that has the potential to rapidly and accurately evaluate the timing of ore formation.Our study employs a novel application of in situ scheelite U-Pb dating analysis using laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)and samples from the Qiaomaishan deposit,a representative example of skarn mineralization within the Xuancheng ore district of eastern China.Our approach to scheelite dating of the deposit is verified by cross-comparison to dating of cogenetic garnet and apatite,proving the effectiveness of this approach.Our new approach to dating of scheelite-bearing geological systems is rapid,cheap,requires little sample preparation,and is undertaken in situ,allowing crucial geological and mineralogical context to be retained during analysis.The approaches outlined here not only allow the determination of the absolute timing of formation of the Qiaomaishan deposit through the U-Pb dating of scheelite[138.6±3.2 Ma,N=39,mean square weighted deviation(MSWD)=1.17],garnet(138.4±1.0 Ma,N=40,MSWD=1.3),and apatite(139.6+3.3 Ma,N=35,MSWD=0.72),but also further supports the theoretical genetic links between this mineralization and the emplacement of a proximal porphyritic granodiorite intrusion(zircon U-Pb age:139.5±1.2 Ma,N=23,MSWD=0.3).Moreover,our research indicates that the higher the concentrations of U within scheelite,the more suitable that scheelite is for U-Pb dating,with the main factor controlling the U content of scheelite seemingly being variations in oxygen fugacity conditions.This novel approach provides a potentially powerful tool,not just for the dating of skarn systems but also with potential applications in orogenic and intrusion-related gold,porphyry W-Mo,and greisen mineralizing systems as well as other scheelite-bearing geological bodies or geological systems.
基金financially supported by funds from the National Key R&D Program of China(Grant Nos.2016YFC0600209,2016YFC0600206)the National Natural Science Foundation of China(Grant No.41820104007)+1 种基金the Scientific and Technological Program of Land and Resources of Anhui province(Grant No.2016-K-4)the China Scholarship Council(Grant No.201906690036)。
文摘The Magushan skarn Cu-Mo deposit is a representative example of the skarn mineralization occurring within the Xuancheng ore district of the Middle-Lower Yangtze River Metallogenic Belt of eastern China.The precise age of an ore deposit is important for understanding the timing of mineralization relative to other geological events in a region and to fully place the formation of a mineral deposit within the geological context of other processes that occur within the study area.Here,we present new molybdenite Re-Os and titanite and andradite garnet U-Pb ages for the Magushan deposit and use these data to outline possible approaches for identifying genetic relationships in geologically complex areas.The spatial and paragenetic relationships between the intrusions,alteration,and mineralization within the study area indicates that the formation of the Magushan deposit is genetically associated with the porphyritic granodiorite.However,this is not always the case,as some areas contain complexly zoned plutons with multiple phases of intrusion or mineralization may be distal from or may not have any clear spatial relationship to a pluton.This means that it may not be possible to determine whether the mineralization formed as a result of single or multiple magmatic/hydrothermal events.As such,the approaches presented in this study provide an approach that allows the identification of any geochronological relationships between mineralization and intrusive events in areas more complex than the study area.Previously published zircon U-Pb data for the mineralization-related porphyritic granodiorite in this area yielded an age of 134.2±1.2 Ma(MSWD=1.4)whereas the Re-Os dating of molybdenite from the study area yielded an isochron age of 137.7±2.5 Ma(MSWD=0.43).The timing of the mineralizing event in the study area was further examined by the dating of magmatic accessory titanite and skarn-related andradite garnet,yielding U-Pb ages of 136.3±2.5 Ma(MSWD=3.2)and 135.9±2.7 Ma(MSWD=2.5),respectively.The dating of magmatic and hydrothermal activity within the Magushan area yields ages around 136 Ma,strongly suggesting that the mineralization in this area formed as a result of the emplacement of the intrusion.The dates presented in this study also provide the first indication of the timing of mineralization within the Xuancheng district.providing evidence of a close genetic relationship between the formation of the mineralization within the Xuancheng district and the Early Cretaceous magmatism that occurred in this area.This in turn suggests that other Early Cretaceous intrusive rocks within this region are likely to be associated with mineralization and should be considered highly prospective for future mineral exploration.This study also indicates that the dating of garnet and titanite can also provide reliable geochronological data and evidence of the timing of mineralization and magmatism,respectively,in areas lacking other dateable minerals(e.g.,molybdenite)or where the relationship between mineralization and magmatism is unclear,for example in areas with multiple stages of magmatism,with complexly zoned plutons,and with distal skarn mineralization.
基金This study is supported by the National Key Research and Development Program(2016YFC0600206)Natural Science Foundation of China(41341390441,41302050,41872081)Supporting Program for the Fundamental Research Funds for Central Universities(JZ2016HGTB0730).
文摘Magmatic microgranular enclaves(MMEs)are widely developed in the Shaocunwu granodiorite at the northeast margin of the eastern Jiangnan orogenic belt.Field geology showed that the MMEs occur as irregular ellipsoids near the edge of the intrusion,and consist of diorite,dominantly composed of amphibole,biotite,and plagioclase grains,with minor acicular apatite.Zircon U-Pb dating showed the ages of the host granodiorites and MMEs are 145.9±1.1 Ma and 145.6±2.5 Ma,respectively,indicating both originated during coeval late Jurassic magmatism.Whole-rock geochemical results show that the host granodiorite and MMEs have similar rare earth and trace element partition curves in spider grams,and similar 87Sr/86Sr,and 147Nd/144Nd isotope ratios,and their zircon 177Hf/176Hf isotopic ratios are similar.Geochemical studies indicate that both the host granodiorite and MMEs formed by mixing of coeval magma.Zircon Ti thermometers and oxygen fugacity of the host granodiorite and the MMEs show high oxygen fugacity,similar to that of W-Cu(Mo)mineralized granitoids in the eastern Jiangnan orogenic belt.A similar magma mixing process was probably one of the mechanisms that generated the W-Cu(Mo)fertile melts.
文摘Introduction to the Middle-Lower Yangtze River Valley Metallogenic Belt The Middle-Lower Yangtze River Valley metallogenic belt(MLYB)has been a cradle of modern metallogeny in China.In the MLYB,there are numerous stratabound sulfide deposits and polymetallic skarn-porphyry and magnetite-apatite deposits,together constituting a significant mineralogic exploration belt on the northern margin of the Yangtze craton.The deposit metallogenic series(Cheng et al.,1979),the metallogenic system(Zhai,1999),a porphyritic iron metallogenic model(Ningwu Iron Ore Research Group,1978),the continental fault depression belt in a syngenetic submarine copper deposit(Gu and Xu,1986),stratabound skarn(Chang et al.,1991)and the Mesozoic large-scale metallogenic explosion(Pan and Dong,1999;Mao et al.,1999)in the MLYB have been described and reviewed in detail.The Middle to Lower Yangtze region has been one of the main targets of research and exploration since the early period of geological work in China since the middle 20th century,Chang et al.(1991),Zhai et al.(1992),Tang et al.(1998)and other researchers have made a full review of the achievements before the 1990s.In the 21st century,much further research work has been carried out in the MLYB.Chang et al.(2012,2017,2019),Mao et al.(2011,2012),Pirajno and Zhou(2015),Xie et al.
基金financially supported by the National Natural Science Foundation of China (Nos.42272074,42002077)the Fundamental Research Funds for the Central Universities (No.JZ2022HGTB0301)。
文摘0 INTRODUCTION Granite-related uranium deposits are one of the most important types of uranium deposits in South China,and their genetic model generally involves uranium leaching from the preexisting rocks(mainly granites),U transport as uranyl carbonate and fluoride complexes and probably chloride complexes in hydrothermal solutions,and U precipitation caused by physicochemical changes(Chi et al.,2020;Hu et al.,2008).Mineralization ages of granite-related uranium deposits in South China have been a subject of significant controversy among researchers and were investigated using several methods,such as bulk uraninite U-Pb isotopic dating,in situ analytical techniques,pyrite Rb-Sr dating as well as bulk uraninite Sm-Nd dating(e.g.,Zhang et al.,2022;Zhong et al.,2019;Bonnetti et al.,2018;Luo et al.,2015;Huang et al.,2010;Ye,2005).