Permian intrusions are widespread in the Middle and Southern Tien-Shan,with fewer occurrences in the Northern Tien-Shan.Notably,many of these intrusions are spatially associated with a variety of ore deposits,indicati...Permian intrusions are widespread in the Middle and Southern Tien-Shan,with fewer occurrences in the Northern Tien-Shan.Notably,many of these intrusions are spatially associated with a variety of ore deposits,indicating a significant link between magmatic activity and mineralization processes in these areas.We studied granite samples recently recovered from drilling in the Kumtor gold field to evaluate their potential relationships with gold mineralization.The major and trace element geochemistry,zircon U-Pb age and Hf isotope data for this so-called Kumtor granite are reported.The Kumtor granite is metaluminous to peraluminous and belongs to the high-K and calc-alkaline series with I-type geochemical characteristics.The relatively high K_(2)O and Na_(2)O concentrations and low high field strength elements(HFSE)and heavy rare earth elements(HREE),the presence of biotite within these I-type granites,together with their low zircon saturation temperatures(731-779℃),suggest that they were likely derived from a hydrous source formed by dehydration melting of mica-bearing,medium-to high-K metabasaltic rocks.The zircon U-Pb dating results indicate that the Kumtor granite intruded at 293±1.7 Ma,which is consistent with the age range of other Middle Tien-Shan granitoids.The zircon Hf isotopic composition isε_(Hf)(t)=-7.56 to-5.05,indicating an ancient(1.39 to 1.52 Ga)crustal origin.Petrographical,geochemical and geochronological data indicate that the Kumtor granite is similar to leucogranites of the Terekty Complex.These results indicate that the Kumtor granite was emplaced in the Early Permian in a postcollision setting and may have temporal and genetic relationships with gold mineralization.展开更多
Knowledge of the interactions among atmospheric dynamics,dust emissions and climate system is essential to understand the physical mechanisms for the dust lifecycle,their role in loess formation as well as the predict...Knowledge of the interactions among atmospheric dynamics,dust emissions and climate system is essential to understand the physical mechanisms for the dust lifecycle,their role in loess formation as well as the predictions of future dust concentration.However,these issues still remain relatively poorly known in Central Asia(CA).The extensive loess deposits on the CA pediments provide a promising archive to explore atmospheric dust dynamics and climatic conditions in the past and their association with loess formation.This study investigates the granulometric and magnetic properties of a loess section(named Osh section)in the Fergana Valley,which provides a sensitive record of atmospheric dust dynamics since 30 ka based on radiometric(AMS ^(14)C)dating.The frequency-dependent magnetic susceptibility(χfd)and the mean grain size are used to reconstruct the broadscale effective moisture and summer atmospheric dynamics pattern in CA,respectively.The results show that the precession forcing exerts a huge influence on the wind-regime variabilities in CA,but with different physical processes under the impact of the Northern Hemisphere ice sheet(NHIS)before and after 15 ka.The origin of the sedimentation rate variations in the Osh loess is also linked to the NHIS-modulated changes of the atmospheric circulation patterns.Either the strengthened westerlies or the increased surface roughness from higher vegetation cover in loess-deposition areas have significantly accelerated the loess accumulation.As a result,these complicated influence factors of sedimentation rate change in the Osh loess section,especially during the Holocene epoch,may hamper accessibility of the authentic dust emission flux and atmospheric dust concentration in CA.展开更多
The high-to ultrahigh-pressure metamorphic rocks of the Atbashy complex were petrologically investigated. The eclogites of the Choloktor Formation show a prograde evolution from epidote-blueschist facies(P = 17-21 kba...The high-to ultrahigh-pressure metamorphic rocks of the Atbashy complex were petrologically investigated. The eclogites of the Choloktor Formation show a prograde evolution from epidote-blueschist facies(P = 17-21 kbar and T = 450-515 ℃) to peak eclogite-UHP conditions(P = 26-29 kbar and T = 545-615 ℃) with a subsequent epidote-amphibolite and greenschist facies overprint. The micaschists of the Choloktor Formation also show a clockwise P-T path from blueschist/epidote-blueschist facies conditions through peak eclogite facies conditions(P = 21-23 kbar and T = 530-580 ℃) to retrograde epidote-amphibolite and greenschist facies stages. A comparison of the P-T paths in the eclogites and mica-schists of Choloktor Formation reveal that they may have shared their P-T history from peak to retrograde stages. The mica-schists of the Atbashy Formation record peak metamorphism of P = 10-12 kbar and T = 515-565 ℃, which indicates that the highest grade of regional metamorphism in the Atbashy Ridge was epidote-amphibolite facies.The newly obtained P-T conditions for the mica-schists of Choloktor Formation indicate that sheets of sedimentary rocks were brought to great depths along the subduction zone and they metamorphosed under eclogite facies HP conditions. The eclogite blocks were amalgamated with mica-schists of Choloktor Formation in the eclogite facies HP conditions and together they experienced isothermal decompression to ～40 km. During this path, the eclogites and mica-schists of Choloktor Formation docked with mica-schists of Atbashy Formation at 10-12 kbar and 515-565 ℃, and from this depth(～40 km) the whole sequence was exhumed together. These new results improve our understanding of high-pressure metamorphism in subduction-related accretionary prism zones and the exhumation processes of deeply-seated rocks in the Atbashy HP-UHP complex.展开更多
Objective Climate fluctuations over suborbital or millennial timescale display significant instability during the last glacial period,which are often superimposed upon the orbital periodicity.They triggered some abrup...Objective Climate fluctuations over suborbital or millennial timescale display significant instability during the last glacial period,which are often superimposed upon the orbital periodicity.They triggered some abrupt climate events,展开更多
The Westerlies is important in linking the Northem high latitude, North Atlantic and East Asian monsoon. The location and intensity of the Westerly jet can not only control the climate of central Asia （including nort...The Westerlies is important in linking the Northem high latitude, North Atlantic and East Asian monsoon. The location and intensity of the Westerly jet can not only control the climate of central Asia （including northwest arid China）, but also significantly influence the climate of the East Asian monsoon region. However, it remains unclear of the variability of the Westerlies in Asia on multiple timeseales and their global linkage.展开更多
Arid Central Asia(ACA), with its diverse landscapes of high mountains, oases, and deserts, hosted the central routes of the Silk Roads that linked trade centers from East Asia to the eastern Mediterranean.Ecological p...Arid Central Asia(ACA), with its diverse landscapes of high mountains, oases, and deserts, hosted the central routes of the Silk Roads that linked trade centers from East Asia to the eastern Mediterranean.Ecological pockets and ecoclines in ACA are largely determined by local precipitation. However, little research has gone into the effects of hydroclimatic changes on trans-Eurasian cultural exchange. Here,we reconstruct precipitation changes in ACA, covering the mid-late Holocene with a U-Th dated, ~3 a resolution, multi-proxy time series of replicated stalagmites from the southeastern Fergana Valley,Kyrgyzstan. Our data reveal a 640-a megadrought between 5820 and 5180 a BP, which likely impacted cultural development in ACA and impeded the expansion of cultural traits along oasis routes. Instead,it may have diverted the earliest transcontinental exchange along the Eurasian steppe during the 5 th millennium BP. With gradually increasing precipitation after the megadrought, settlement of peoples in the oases and river valleys may have facilitated the opening of the oasis routes, ‘‘prehistoric Silk Roads", of trans-Eurasian exchange. By the 4 th millennium BP, this process may have reshaped cultures across the two continents, laying the foundation for the organized Silk Roads.展开更多
The current and potential impacts of global warming have generated widespread concerns about food security among all sectors of society.Central Asian countries located deep in the interior of Asia with fragile ecologi...The current and potential impacts of global warming have generated widespread concerns about food security among all sectors of society.Central Asian countries located deep in the interior of Asia with fragile ecological environments and lower agricultural technology are particularly more prone to severe threats from climate change.Based on panel data acquired in five Central Asian countries from 1990 to 2019,a C-D-C model was developed to study how climate change affects food security in the region and to predict future trends.The study found that the level of food security has generally increased for these five Central Asian countries over the past 30 years,with Kazakhstan and Tajikistan having the highest and lowest food security levels,respectively.The average annual temperature and precipitation exhibit an inverted U-shaped relationship with the region’s food security,with the most positive effect on the food security of Kazakhstan.Extremely high and low temperatures have significantly affected food security in the studied region,with Turkmenistan experiencing the most significant negative impacts.The number of frost days had no significant effect on food security.An analysis of future climate showed that the temperature and precipitation in Central Asia will continue to increase from 2030 to 2090,which will negatively impact the food security of these countries.It is recommended that the Central Asian countries enhance their understanding of climate risks,strengthen scientific climate research,and develop multiple adaptation strategies in advance.Simultaneously,they are encouraged to consolidate international cooperation,reducing greenhouse gas emissions effectively and maintaining the ability to ensure food security.展开更多
基金partly supported by Eurasia-Pacific Uninet projects(Nos.EPU 08/2019 and EPU 18/2020)to Etienne Skrzypek,Rustam Orozbaev and Christoph Hauzenberger。
文摘Permian intrusions are widespread in the Middle and Southern Tien-Shan,with fewer occurrences in the Northern Tien-Shan.Notably,many of these intrusions are spatially associated with a variety of ore deposits,indicating a significant link between magmatic activity and mineralization processes in these areas.We studied granite samples recently recovered from drilling in the Kumtor gold field to evaluate their potential relationships with gold mineralization.The major and trace element geochemistry,zircon U-Pb age and Hf isotope data for this so-called Kumtor granite are reported.The Kumtor granite is metaluminous to peraluminous and belongs to the high-K and calc-alkaline series with I-type geochemical characteristics.The relatively high K_(2)O and Na_(2)O concentrations and low high field strength elements(HFSE)and heavy rare earth elements(HREE),the presence of biotite within these I-type granites,together with their low zircon saturation temperatures(731-779℃),suggest that they were likely derived from a hydrous source formed by dehydration melting of mica-bearing,medium-to high-K metabasaltic rocks.The zircon U-Pb dating results indicate that the Kumtor granite intruded at 293±1.7 Ma,which is consistent with the age range of other Middle Tien-Shan granitoids.The zircon Hf isotopic composition isε_(Hf)(t)=-7.56 to-5.05,indicating an ancient(1.39 to 1.52 Ga)crustal origin.Petrographical,geochemical and geochronological data indicate that the Kumtor granite is similar to leucogranites of the Terekty Complex.These results indicate that the Kumtor granite was emplaced in the Early Permian in a postcollision setting and may have temporal and genetic relationships with gold mineralization.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB40000000 and XDB26000000)Natural Science Foundation of China(Grant Nos.41977385 and 41572162)+1 种基金Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0101)State Key Laboratory of Loess and Quaternary Geology(Grant No.SKLLQGPY2006).
文摘Knowledge of the interactions among atmospheric dynamics,dust emissions and climate system is essential to understand the physical mechanisms for the dust lifecycle,their role in loess formation as well as the predictions of future dust concentration.However,these issues still remain relatively poorly known in Central Asia(CA).The extensive loess deposits on the CA pediments provide a promising archive to explore atmospheric dust dynamics and climatic conditions in the past and their association with loess formation.This study investigates the granulometric and magnetic properties of a loess section(named Osh section)in the Fergana Valley,which provides a sensitive record of atmospheric dust dynamics since 30 ka based on radiometric(AMS ^(14)C)dating.The frequency-dependent magnetic susceptibility(χfd)and the mean grain size are used to reconstruct the broadscale effective moisture and summer atmospheric dynamics pattern in CA,respectively.The results show that the precession forcing exerts a huge influence on the wind-regime variabilities in CA,but with different physical processes under the impact of the Northern Hemisphere ice sheet(NHIS)before and after 15 ka.The origin of the sedimentation rate variations in the Osh loess is also linked to the NHIS-modulated changes of the atmospheric circulation patterns.Either the strengthened westerlies or the increased surface roughness from higher vegetation cover in loess-deposition areas have significantly accelerated the loess accumulation.As a result,these complicated influence factors of sedimentation rate change in the Osh loess section,especially during the Holocene epoch,may hamper accessibility of the authentic dust emission flux and atmospheric dust concentration in CA.
基金partly supported by the Project ISTC(No KR-712)to the Institute of Geology of NAS KR and JSPS KAKENHI(Grant Nos.JP15H05695 for AT and JP12F02026 for RO)
文摘The high-to ultrahigh-pressure metamorphic rocks of the Atbashy complex were petrologically investigated. The eclogites of the Choloktor Formation show a prograde evolution from epidote-blueschist facies(P = 17-21 kbar and T = 450-515 ℃) to peak eclogite-UHP conditions(P = 26-29 kbar and T = 545-615 ℃) with a subsequent epidote-amphibolite and greenschist facies overprint. The micaschists of the Choloktor Formation also show a clockwise P-T path from blueschist/epidote-blueschist facies conditions through peak eclogite facies conditions(P = 21-23 kbar and T = 530-580 ℃) to retrograde epidote-amphibolite and greenschist facies stages. A comparison of the P-T paths in the eclogites and mica-schists of Choloktor Formation reveal that they may have shared their P-T history from peak to retrograde stages. The mica-schists of the Atbashy Formation record peak metamorphism of P = 10-12 kbar and T = 515-565 ℃, which indicates that the highest grade of regional metamorphism in the Atbashy Ridge was epidote-amphibolite facies.The newly obtained P-T conditions for the mica-schists of Choloktor Formation indicate that sheets of sedimentary rocks were brought to great depths along the subduction zone and they metamorphosed under eclogite facies HP conditions. The eclogite blocks were amalgamated with mica-schists of Choloktor Formation in the eclogite facies HP conditions and together they experienced isothermal decompression to ～40 km. During this path, the eclogites and mica-schists of Choloktor Formation docked with mica-schists of Atbashy Formation at 10-12 kbar and 515-565 ℃, and from this depth(～40 km) the whole sequence was exhumed together. These new results improve our understanding of high-pressure metamorphism in subduction-related accretionary prism zones and the exhumation processes of deeply-seated rocks in the Atbashy HP-UHP complex.
基金co-supported by the National Natural Science Foundation of China(Grants Nos:41572162.41290253)International Partnership Program of the Chinese Academy of Sciences(No:132B61KYS20160002)
文摘Objective Climate fluctuations over suborbital or millennial timescale display significant instability during the last glacial period,which are often superimposed upon the orbital periodicity.They triggered some abrupt climate events,
基金supported by the National Natural Science Foundation of China(grants No.41290254 and 41372192)the State Key Laboratory of Loess and Quaternary Geology,and Chinese Academy of Science(International partnership Program,grant No.132B61KYS20160002)
文摘The Westerlies is important in linking the Northem high latitude, North Atlantic and East Asian monsoon. The location and intensity of the Westerly jet can not only control the climate of central Asia （including northwest arid China）, but also significantly influence the climate of the East Asian monsoon region. However, it remains unclear of the variability of the Westerlies in Asia on multiple timeseales and their global linkage.
基金supported by the National Key Research and Development Program of China (2018YFA0606400)he Strategic Priority Research Program of Chinese Academy of Sciences (XDB40000000)+5 种基金the 2nd Tibetan Plateau Scientific Expedition and Research (2019QZKK0101)the Youth Innovation Promotion Association of Chinese Academy of Sciences (Y201681)partly supported by the National Natural Science Foundation of China (41888101)the National Social Science Foundation of China (18ZDA172)the National Science Foundation of United States (NSF 1702816, EAR-0908792, and EAR-1211299)a part of the ‘‘Belt & Road” Project of the Institute of Earth Environment, Chinese Academy of Sciences (IEECAS)。
文摘Arid Central Asia(ACA), with its diverse landscapes of high mountains, oases, and deserts, hosted the central routes of the Silk Roads that linked trade centers from East Asia to the eastern Mediterranean.Ecological pockets and ecoclines in ACA are largely determined by local precipitation. However, little research has gone into the effects of hydroclimatic changes on trans-Eurasian cultural exchange. Here,we reconstruct precipitation changes in ACA, covering the mid-late Holocene with a U-Th dated, ~3 a resolution, multi-proxy time series of replicated stalagmites from the southeastern Fergana Valley,Kyrgyzstan. Our data reveal a 640-a megadrought between 5820 and 5180 a BP, which likely impacted cultural development in ACA and impeded the expansion of cultural traits along oasis routes. Instead,it may have diverted the earliest transcontinental exchange along the Eurasian steppe during the 5 th millennium BP. With gradually increasing precipitation after the megadrought, settlement of peoples in the oases and river valleys may have facilitated the opening of the oasis routes, ‘‘prehistoric Silk Roads", of trans-Eurasian exchange. By the 4 th millennium BP, this process may have reshaped cultures across the two continents, laying the foundation for the organized Silk Roads.
基金This work was supported by the Chinese Academy of Sciences(Grant No.xbzg-zdsys-202217)the Shandong Provincial Special Fund(Grant No.LSKJ202203300).
文摘The current and potential impacts of global warming have generated widespread concerns about food security among all sectors of society.Central Asian countries located deep in the interior of Asia with fragile ecological environments and lower agricultural technology are particularly more prone to severe threats from climate change.Based on panel data acquired in five Central Asian countries from 1990 to 2019,a C-D-C model was developed to study how climate change affects food security in the region and to predict future trends.The study found that the level of food security has generally increased for these five Central Asian countries over the past 30 years,with Kazakhstan and Tajikistan having the highest and lowest food security levels,respectively.The average annual temperature and precipitation exhibit an inverted U-shaped relationship with the region’s food security,with the most positive effect on the food security of Kazakhstan.Extremely high and low temperatures have significantly affected food security in the studied region,with Turkmenistan experiencing the most significant negative impacts.The number of frost days had no significant effect on food security.An analysis of future climate showed that the temperature and precipitation in Central Asia will continue to increase from 2030 to 2090,which will negatively impact the food security of these countries.It is recommended that the Central Asian countries enhance their understanding of climate risks,strengthen scientific climate research,and develop multiple adaptation strategies in advance.Simultaneously,they are encouraged to consolidate international cooperation,reducing greenhouse gas emissions effectively and maintaining the ability to ensure food security.
