The Aqishan-Yamansu metallogenic belt(AYMB)in East Tianshan hosts abundant sub-marine volcanic-hosted iron deposits.Although there is agreement with the magmatic source of the ore-forming materials and the role of hyd...The Aqishan-Yamansu metallogenic belt(AYMB)in East Tianshan hosts abundant sub-marine volcanic-hosted iron deposits.Although there is agreement with the magmatic source of the ore-forming materials and the role of hydrothermal replacement in iron ore formation,the mineraliza-tion processes of these iron deposits remain uncertain.Three ore types are identified on the basis of the geological occurrences of minerals and the sequence of mineral in ores.The typeⅠores are characte-rized by magnetite,diopside,amphibole with a few pyrite,and chalcopyrite.The type II ores are mainly composed of magnetite,garnet,chlorite with a few pyrite,while the type III ores are mainly composed of magnetite,quartz,calcite with a few pyrite.In order to constrain the mineralization processes of these ore types,we performed iron isotopes and trace element compositions of magnetite from three typical iron deposits(Yamansu,Duotoushan and Luotuofeng).Trace element and Fe isotope investiga-tions of the three ore types reveal two major groups.The groupⅠconsists of analyses of the typeⅠandⅡores,with both showing a narrow range of positiveδ56Fe values(+0.08‰to+0.22‰for typeⅠores and+0.15‰ to+0.22‰ for typeⅡores)and plotting in the range of the ortho-magmatic field.In contrast,the group 2 is composed merely of the typeⅢores,showing a wider range of negativeδ56Fe values(-0.49‰ to-0.01‰),which is similar to the features of Fe-skarn magnetite.As shown in the binary dia-grams of magnetite trace elements and a fractionation of the Fe isotopes,different ore types were likely produced during gradually changing ore-forming stages from magmatic to hydrothermal.Collectively,the submarine volcanic-hosted iron deposits in the East Tianshan are likely the results of a continuous magmatic-hydrothermal mineralization process.展开更多
Chromium,a strategic mineral resource in China,is widely used in high-precision equipment manufacturing.As the world's leading consumer and importer of chromite,China's external dependence exceeds 99%.The sign...Chromium,a strategic mineral resource in China,is widely used in high-precision equipment manufacturing.As the world's leading consumer and importer of chromite,China's external dependence exceeds 99%.The significant imbalance between domestic supply and demand seriously threatens national economic security.This study discusses the state of China's chromium resource supply from four aspects:the overview of domestic and global chromium resources,China's chromite production and import volume,the sources of imported chromite,and risk analysis.Considering the chromium industrial chain and factors such as production,consumption,and recovery tendency of chromium-bearing stainless steel,it is forecasted that China's demand for chromium ore will decline by 2040.This could considerably reduce the security situation of chromium resources.This study proposes five strategies for securing chromium resources:technological innovation,enhancing international cooperation and acquiring overseas resources,constructing a new pattern of“dual circulation”resource guarantee for sea-land transportation,encouraging chromium recycling,and building an emergency management system and strategic reserve mechanism for chromium resources.展开更多
The predominant types of high-grade iron deposits in China include skarn,sedimentary metamorphic(banded ironformation,BIF-type),continental/submarine volcanic-hosted and magmatic Fe-Ti-Voxide deposits.Based on a compr...The predominant types of high-grade iron deposits in China include skarn,sedimentary metamorphic(banded ironformation,BIF-type),continental/submarine volcanic-hosted and magmatic Fe-Ti-Voxide deposits.Based on a comprehensive review of current studies on these deposits,this paper suggests that the oxygen concentration in atmosphere played an important role for the formation of BIFs,whereas the tectonic setting and deep magmatic differentiation processes are more important for the other types.Notably,both high temperature and high pressure experiments and melt inclusion studies indicate that during the differentiation,high temperature magmas could develop iron-rich magma via liquid immiscibility but not pure oxide melt("iron ore magma").Fe-P melt could be generated directly by liquid immiscibility under hydrous and oxidized condition.The formation of high-grade iron deposits is mostly associated with the processes related to multiple stages of superimposition,e.g.,desiliconization and iron enrichment,removal of impurity,and remobilization and re-precipitation of iron.According to the temporal evolution,the high-grade iron deposit could be divided into multi-episode superimposition type(temporally discontinuous mineralization)and multi-stage superimposition type(temporally continuous mineralization).The former is represented by the sedimentary metamorphic iron deposit,and the latter includes those related to magmatic-hydrothermal fluids(e.g.,skarn,volcanic-hosted and magmatic types).展开更多
We explore firm quasi-dynamics(entry,exit,and growth)in Chinese manufacturing industry and investigate how these dynamics vary across regions.Our results show that relative to provinces with less developed economies,i...We explore firm quasi-dynamics(entry,exit,and growth)in Chinese manufacturing industry and investigate how these dynamics vary across regions.Our results show that relative to provinces with less developed economies,in provinces with more developed economies(i)there is a higher proportion of new firms;(i)new firms are smaller and more labor-intensive;(ii)firms exit at a quicker rate,and surviving firms grow faster.These results point toward cross-region differences in market efficiency in terms of how much it costs a firm to enter or exit the market.Our findings shed light on how firms should adapt their strategies across regions and how the government should create sound policies on industrial upgradingand relocation.展开更多
基金This study was financially supported by National Natural Science Foundation of China(No.41672078)the China Geological Survey(No.DD20190606).
文摘The Aqishan-Yamansu metallogenic belt(AYMB)in East Tianshan hosts abundant sub-marine volcanic-hosted iron deposits.Although there is agreement with the magmatic source of the ore-forming materials and the role of hydrothermal replacement in iron ore formation,the mineraliza-tion processes of these iron deposits remain uncertain.Three ore types are identified on the basis of the geological occurrences of minerals and the sequence of mineral in ores.The typeⅠores are characte-rized by magnetite,diopside,amphibole with a few pyrite,and chalcopyrite.The type II ores are mainly composed of magnetite,garnet,chlorite with a few pyrite,while the type III ores are mainly composed of magnetite,quartz,calcite with a few pyrite.In order to constrain the mineralization processes of these ore types,we performed iron isotopes and trace element compositions of magnetite from three typical iron deposits(Yamansu,Duotoushan and Luotuofeng).Trace element and Fe isotope investiga-tions of the three ore types reveal two major groups.The groupⅠconsists of analyses of the typeⅠandⅡores,with both showing a narrow range of positiveδ56Fe values(+0.08‰to+0.22‰for typeⅠores and+0.15‰ to+0.22‰ for typeⅡores)and plotting in the range of the ortho-magmatic field.In contrast,the group 2 is composed merely of the typeⅢores,showing a wider range of negativeδ56Fe values(-0.49‰ to-0.01‰),which is similar to the features of Fe-skarn magnetite.As shown in the binary dia-grams of magnetite trace elements and a fractionation of the Fe isotopes,different ore types were likely produced during gradually changing ore-forming stages from magmatic to hydrothermal.Collectively,the submarine volcanic-hosted iron deposits in the East Tianshan are likely the results of a continuous magmatic-hydrothermal mineralization process.
基金supported by the Consulting Research Project of the Chinese Academy of Engineering (Nos.2022-XY-82,2023-XY-21,and 2023-XZ-25).
文摘Chromium,a strategic mineral resource in China,is widely used in high-precision equipment manufacturing.As the world's leading consumer and importer of chromite,China's external dependence exceeds 99%.The significant imbalance between domestic supply and demand seriously threatens national economic security.This study discusses the state of China's chromium resource supply from four aspects:the overview of domestic and global chromium resources,China's chromite production and import volume,the sources of imported chromite,and risk analysis.Considering the chromium industrial chain and factors such as production,consumption,and recovery tendency of chromium-bearing stainless steel,it is forecasted that China's demand for chromium ore will decline by 2040.This could considerably reduce the security situation of chromium resources.This study proposes five strategies for securing chromium resources:technological innovation,enhancing international cooperation and acquiring overseas resources,constructing a new pattern of“dual circulation”resource guarantee for sea-land transportation,encouraging chromium recycling,and building an emergency management system and strategic reserve mechanism for chromium resources.
基金supported by the National Basic Research Program of China(Grant No.2012CB416800)。
文摘The predominant types of high-grade iron deposits in China include skarn,sedimentary metamorphic(banded ironformation,BIF-type),continental/submarine volcanic-hosted and magmatic Fe-Ti-Voxide deposits.Based on a comprehensive review of current studies on these deposits,this paper suggests that the oxygen concentration in atmosphere played an important role for the formation of BIFs,whereas the tectonic setting and deep magmatic differentiation processes are more important for the other types.Notably,both high temperature and high pressure experiments and melt inclusion studies indicate that during the differentiation,high temperature magmas could develop iron-rich magma via liquid immiscibility but not pure oxide melt("iron ore magma").Fe-P melt could be generated directly by liquid immiscibility under hydrous and oxidized condition.The formation of high-grade iron deposits is mostly associated with the processes related to multiple stages of superimposition,e.g.,desiliconization and iron enrichment,removal of impurity,and remobilization and re-precipitation of iron.According to the temporal evolution,the high-grade iron deposit could be divided into multi-episode superimposition type(temporally discontinuous mineralization)and multi-stage superimposition type(temporally continuous mineralization).The former is represented by the sedimentary metamorphic iron deposit,and the latter includes those related to magmatic-hydrothermal fluids(e.g.,skarn,volcanic-hosted and magmatic types).
基金financial support from the National Natural Science Foundation of China(No.71773004).
文摘We explore firm quasi-dynamics(entry,exit,and growth)in Chinese manufacturing industry and investigate how these dynamics vary across regions.Our results show that relative to provinces with less developed economies,in provinces with more developed economies(i)there is a higher proportion of new firms;(i)new firms are smaller and more labor-intensive;(ii)firms exit at a quicker rate,and surviving firms grow faster.These results point toward cross-region differences in market efficiency in terms of how much it costs a firm to enter or exit the market.Our findings shed light on how firms should adapt their strategies across regions and how the government should create sound policies on industrial upgradingand relocation.
