In mid-May,good news came from Tajikistan,the country of high mountains.The Tajikistan Bogda Mountain geological exploration and sampling project,which had been dormant for over a decade,achieved a key breakthrough af...In mid-May,good news came from Tajikistan,the country of high mountains.The Tajikistan Bogda Mountain geological exploration and sampling project,which had been dormant for over a decade,achieved a key breakthrough after years of careful research,multi-party collaboration,and optimization of various plans,launching a new round of field exploration and testing work.展开更多
Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,i...Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,is an important ecological barrier area in the temperate arid zone.The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve.In the present study,we assessed the spatiotemporal variations of four ecosystem services(including net primary productivity(NPP),water yield,soil conservation,and habitat quality)in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.In addition,the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis,and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector.During the study period,NPP and soil conservation values in the reserve increased by 48.20%and 25.56%,respectively;conversely,water yield decreased by 16.56%,and there was no significant change in habitat quality.Spatially,both NPP and habitat quality values were higher in the northern part and lower in the southern part,whereas water yield showed an opposite trend.Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation,and exhibited a trade-off relationship with water yield.Water yield and habitat quality also had a trade-off relationship.NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index(NDVI),respectively,while water yield and soil conservation were more affected by digital elevation model(DEM).Therefore,attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management.The findings of the present study provide a reference that could facilitate the sustainable utilization of ecosystem services in the typical fragile areas of Northwest China.展开更多
Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glac...Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate＇s impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer （ASTER） imagery show the trends that are highly variable over time and within the region. An analysis of the local topographic settings of very small （〈0.5 km2） glaciers was conducted to investigate their influence on recent changes in these glaciers. Among 137 glaciers, 12 disappeared completely. The study reveals that glaciers situated in favorable locations had tiny relative area reduction, while those in less favorable settings generally had large area loss or even disappeared. It is suggested that most of the small glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century. Undoubtedly, the strong retreating of small glaciers exerts adverse effects on the hydro- logic cycle and local socioeconomic development.展开更多
Glacier is one kind of the most beautiful geological sightseeing in the world as well as a special kind of tourism resources.The characters of glacier tourism include scarcity,frangibility,localization of tourist acti...Glacier is one kind of the most beautiful geological sightseeing in the world as well as a special kind of tourism resources.The characters of glacier tourism include scarcity,frangibility,localization of tourist activity,scien-tific connotation,and integrated function and value.The paper summarizes the latest researches in developing glacier tourism resources.Regarding the Bogda Glacier Park as an example,the authors analyze the characteristics of glacier tourism resources in detail and the conditions and potential threats of glacier tourism development.Suggestions on glacier tourism development and protection are given as follows:1) to plan function subarea scientifically and rea-sonably;2) to combine tourism,scientific research with ecological education;3) to take countermeasures of environ-mental protection;4) to integrate tourism resources and strengthening regional cooperation.Finally,emphases are put forward on resources conformity along the tourism line and cooperation of tourism management.The paper aims to seek after the coordination path in exploitation and protection of glacier tourism resources to guide the exploitation of other glacier tourism destinations.展开更多
Many small mountain glaciers have been reported undergoing strong shrinkage, and it is therefore important to understand how they respond to climate change. The availability of topographic maps from 1962, Landsat TM i...Many small mountain glaciers have been reported undergoing strong shrinkage, and it is therefore important to understand how they respond to climate change. The availability of topographic maps from 1962, Landsat TM imagery from 1990 and ASTER（Advanced Spaceborne Thermal Emission and Radiometer） imagery from 2006 and field investigation of some glaciers allow a comprehensive analysis of glacier change based on glacier size and topography on Mt. Bogda. Results include：（1） an overall loss of a glacierized area by 31.18±0.31 km^2 or 21.6% from 1962 to 2006,（2） a marked dependence of glacier area shrinkage on initial size, with smaller glaciers experiencing higher shrinkage levels,（3） the disappearance of 12 small glaciers,（4） a striking difference in area loss between the southern and northern slopes of 25% and 17%, respectively. A subset of the investigated glaciers shows that the area 57.45±0.73 km2 in 1962 reduced to 54.79±0.561 km^2 in 1990 and 48.88±0.49 km^2 in 2006, with a relative area reduction of 4.6% during 1962-1990, and 10.8% during 1990-2006. The corresponding volume waste increased from 6.9% to 10.2%. Three reference glaciers were investigated in 1981 and revisited in 2009. Their terminus experienced a marked recession. Meteorological data from stations around Mt. Bogda reveals that glacier shrinkage is correlated with winter warming and an extension of the ablation period. Precipitation on the northwest side of the range shows a marked increase, with a slight increase on the southeast side.展开更多
Apatite fission track （AFT） analysis on samples collected from a Paleozoic series is used to constrain the cooling history of the Bogda Mountain, northwest China. AFT ages range from 136.2 to 85.6 Ma and are younger...Apatite fission track （AFT） analysis on samples collected from a Paleozoic series is used to constrain the cooling history of the Bogda Mountain, northwest China. AFT ages range from 136.2 to 85.6 Ma and are younger than rock depositional ages and the mean confined track lengths （11.0 13.2 μm） mostly showing unimodal distribution are shorten, indicating significant track-annealing. Thermal histories modeling based on the distribution of fission-track lengths combined with the regional geological data show that two rapid cooling phases occurred in the latest Jurassic-early Cretaceous and the Oligocene-Miocene. Those new data together with previous published data show that the AFT ages become younger from the southwest to northeast in the western Bogda Mountain and its adjacent areas. The fission-track ages of the southwest area are relatively older （〉100 Ma）, recording the earlier rapid uplift phase during the late Jurassic-Cretaceous, while the ages in the north pied- mont of the Bogda Mountain （namely the northeast part） are younger （〈60 Ma）, mainly reflecting the later rapid uplift phase in the Oligocene-Miocene. The trend of younger AFT ages towards the northeast might be explained by post-Cretaceous large-scale crustal tilting towards the southwest. In the thrust fault-dominated northern limbs of the Bogda Mountain, AFT ages reveal a discontinuous pattern with age-jumps across the major fault zones, showing a possible strata tilting across each thrust faults due to the thrust ramps during the Cenozoic. The two rapid uplift stages might be related to the accretion and collision in the southern margin of the Asian continent during the late Jurassic and late Cenozoic, respectively.展开更多
Based on field geological survey,interpretation of seismic data and analysis of drilling and logging data,the evolution of geological structures,stratigraphic sedimentary filling sequence and sedimentary system around...Based on field geological survey,interpretation of seismic data and analysis of drilling and logging data,the evolution of geological structures,stratigraphic sedimentary filling sequence and sedimentary system around the Bogda Mountain were analyzed according to the idea of"structure controlling basin,basin controlling facies and facies controlling assemblages".The tectonic evolution of the basin around the Bogda Mountain can be divided into nine stages.The Middle-Late Permian–Middle-Late Triassic was the development stage of intracontinental rift,foreland basin and inland depression basin when lake,fan delta and braided river delta sedimentary facies developed.Early intracontinental rifting,late Permian tectonic uplift,and middle-late Triassic tectonic subsidence controlled the shape,type,subsidence rate and sedimentary system evolution of the basin.The Bogda Mountain area was the subsidence center and deposition center of the deep water lake basin in the Middle Permian with mainly deep-water deposition and local gravity flow deposition.This area had tectonic inversion in the Late Permian,when the Bogda Mountain uplifted to form a low bulge and a series of fan delta sand bodies.In the Middle-Late Triassic,subsidence occurred in the Bogda low uplift,characterized by extensive development of braided river delta deposits.展开更多
The Bogda Shan orogenic belt is interpreted to be an Upper Palaeozoic continental rift, which was closed towards the end of the Carboniferous period. Intrusive activities in that belt are represented mainly by a large...The Bogda Shan orogenic belt is interpreted to be an Upper Palaeozoic continental rift, which was closed towards the end of the Carboniferous period. Intrusive activities in that belt are represented mainly by a large number of diabasic sills, dykes and stocks with sparse dioritic and granitic bodies. Determinations on a group of samples from the Shangdaheyan intrusion yielded a mineral\|rock Rb\|Sr isochron with an age of \{298.4±0.76\} Ma and an initial \{\{\}\+\{87\}Sr\}/\+\{86\}Sr ratio of 0.7041. In combination with field evidence, these results indicate that most of the intusions of the Bogda Shan orogenic belt were emplaced during the Hercynian cycle as a result of initial extension following rift closure, and that post\|Hercynian intrusive activities are not important in that belt.展开更多
Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be...Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be divided into four stages of thermal evolution: 150-106, 75-65, 44-24 and 13-9 Ma. Before 44-24 Ma, the cooling rate and uplifting rate of the southern and northern segments of Mt. Bogda are almost the same, showing that the uplifting of Mt. Bogda is an overall process. Since 44-24 Ma, the uplifting of the southern and northern segments of Mt. Bogda has shown differences. During 42-11 Ma, the northern segment of Mt. Bogda was at a steady stage, with the cooling rate being {0.03℃/Ma} and the uplifting rate being {0.001} mm/a. From 11 Ma to the present, the northern segment of Mt. Bogda was at a rapid cooling and uplifting stage, with the cooling rate being {5.72℃/Ma} and the uplifting rate being {0.19} mm/a. However, the southern segment of Mt. Bogda has been at a rapid cooling and uplifting stage since 26 Ma, with the cooling rate being {1.24℃/Ma} and the uplifting rate being {0.041} mm/a during 26-9 Ma; {4.88℃/Ma} and {0.163} mm/a from 9 Ma till now.展开更多
The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most ...The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evo展开更多
This study investigates the provenance of sedimentary rocks in Bogda Mountains, NW China, and reconstructs the lithology and unroofing history of the Eastern North Tianshan Suture. Petrographic point counting data of ...This study investigates the provenance of sedimentary rocks in Bogda Mountains, NW China, and reconstructs the lithology and unroofing history of the Eastern North Tianshan Suture. Petrographic point counting data of sandstones and compositions of conglomerates of upper Permian-lowermost Triassic Wutonggou low-order cycle from Zhaobishan, North Tarlong, Taodonggou, and Dalongkou sections in the southern and northern foothills of Bogda Mountains were used to interpret the temporal and spatial variations of lithology of the Eastern North Tianshan Suture, which is the sediment source area. Three compositional trends were identified. A trend of upwardincreasing quartz content and granitic pebbles in Zhaobishan section suggests a change from the undissected volcanic arc, accretionary wedge and trench setting to predominantly transitional volcanic arc and subordinate accretionary wedge and trench, in the eastern part of the Eastern North Tianshan Suture. In North Tarlong and Taodonggou sections, however, the lithic content decreases and the contents of quartz and granitic pebbles increase up sections. These trends indicate that the western part of the Eastern North Tianshan Suture changed from an undissected volcanic arc to the transitional volcanic arc, accretionary wedge and trench. No clear trend in the lithic-rich sandstones of the Dalongkou section indicates that sediments were derived from the undissected volcanic arc in the Eastern North Tianshan Suture and local rift shoulders. Compositional variations of studied rocks suggest that the Eastern North Tianshan Suture was an amalgamated complex with great spatial and temporal heterogeneities in lithology and experienced persistent unroofing during late Permian-earliest Triassic. This study reconstructs a key element of the Chinese Tianshan Suture and serves as an example to understand the unroofing processes of ancient sutures.展开更多
文摘In mid-May,good news came from Tajikistan,the country of high mountains.The Tajikistan Bogda Mountain geological exploration and sampling project,which had been dormant for over a decade,achieved a key breakthrough after years of careful research,multi-party collaboration,and optimization of various plans,launching a new round of field exploration and testing work.
基金This research was funded by the Key Laboratory for Sustainable Development of Xinjiang's Historical and Cultural Tourism,Xinjiang University,China(LY2022-06)the Tianchi Talent Project.
文摘Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,is an important ecological barrier area in the temperate arid zone.The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve.In the present study,we assessed the spatiotemporal variations of four ecosystem services(including net primary productivity(NPP),water yield,soil conservation,and habitat quality)in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.In addition,the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis,and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector.During the study period,NPP and soil conservation values in the reserve increased by 48.20%and 25.56%,respectively;conversely,water yield decreased by 16.56%,and there was no significant change in habitat quality.Spatially,both NPP and habitat quality values were higher in the northern part and lower in the southern part,whereas water yield showed an opposite trend.Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation,and exhibited a trade-off relationship with water yield.Water yield and habitat quality also had a trade-off relationship.NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index(NDVI),respectively,while water yield and soil conservation were more affected by digital elevation model(DEM).Therefore,attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management.The findings of the present study provide a reference that could facilitate the sustainable utilization of ecosystem services in the typical fragile areas of Northwest China.
基金supported by the National Basic Research Program of China (No. 2010CB951003)the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-EW-311)the National Natural Science Foundation of China (Nos. 1141001040, J0930003/J0109)
文摘Glacial features in the geological record provide essential clues about past behavior of climate. Of the numerous physical systems on earth, glaciers are one of most responsive to climate change, especially small glaciers, their direct marginal response taking only a few years or decades to be expressed. Accelerating recession of modern glaciers raises the issue of the climate＇s impact on water runoff. Data based on topographic maps and Advanced Spaceborne Thermal Emission and Radiometer （ASTER） imagery show the trends that are highly variable over time and within the region. An analysis of the local topographic settings of very small （〈0.5 km2） glaciers was conducted to investigate their influence on recent changes in these glaciers. Among 137 glaciers, 12 disappeared completely. The study reveals that glaciers situated in favorable locations had tiny relative area reduction, while those in less favorable settings generally had large area loss or even disappeared. It is suggested that most of the small glaciers studied have retreated as far as they are likely to under the climatic conditions of the late 20th century. Undoubtedly, the strong retreating of small glaciers exerts adverse effects on the hydro- logic cycle and local socioeconomic development.
基金Under the auspices of the Western Bright Project (No. 20025023)
文摘Glacier is one kind of the most beautiful geological sightseeing in the world as well as a special kind of tourism resources.The characters of glacier tourism include scarcity,frangibility,localization of tourist activity,scien-tific connotation,and integrated function and value.The paper summarizes the latest researches in developing glacier tourism resources.Regarding the Bogda Glacier Park as an example,the authors analyze the characteristics of glacier tourism resources in detail and the conditions and potential threats of glacier tourism development.Suggestions on glacier tourism development and protection are given as follows:1) to plan function subarea scientifically and rea-sonably;2) to combine tourism,scientific research with ecological education;3) to take countermeasures of environ-mental protection;4) to integrate tourism resources and strengthening regional cooperation.Finally,emphases are put forward on resources conformity along the tourism line and cooperation of tourism management.The paper aims to seek after the coordination path in exploitation and protection of glacier tourism resources to guide the exploitation of other glacier tourism destinations.
基金supported by the Initial Funding of Doctor Scientific Research (No. LZCU-BS2013-06)the Project of Humanities and Social Sciences from the Ministry of Education of China (No. 13YJC790009)+2 种基金the National Basic Research Program of China (No. 2013CBA01801)the National NaturalScience Foundation of China (No. 41471058)the Funds for the Creative Research Groups of China (No. 41121001)
文摘Many small mountain glaciers have been reported undergoing strong shrinkage, and it is therefore important to understand how they respond to climate change. The availability of topographic maps from 1962, Landsat TM imagery from 1990 and ASTER（Advanced Spaceborne Thermal Emission and Radiometer） imagery from 2006 and field investigation of some glaciers allow a comprehensive analysis of glacier change based on glacier size and topography on Mt. Bogda. Results include：（1） an overall loss of a glacierized area by 31.18±0.31 km^2 or 21.6% from 1962 to 2006,（2） a marked dependence of glacier area shrinkage on initial size, with smaller glaciers experiencing higher shrinkage levels,（3） the disappearance of 12 small glaciers,（4） a striking difference in area loss between the southern and northern slopes of 25% and 17%, respectively. A subset of the investigated glaciers shows that the area 57.45±0.73 km2 in 1962 reduced to 54.79±0.561 km^2 in 1990 and 48.88±0.49 km^2 in 2006, with a relative area reduction of 4.6% during 1962-1990, and 10.8% during 1990-2006. The corresponding volume waste increased from 6.9% to 10.2%. Three reference glaciers were investigated in 1981 and revisited in 2009. Their terminus experienced a marked recession. Meteorological data from stations around Mt. Bogda reveals that glacier shrinkage is correlated with winter warming and an extension of the ablation period. Precipitation on the northwest side of the range shows a marked increase, with a slight increase on the southeast side.
基金supported by the State Science and Technology Major Project(2009ZX05009-001)
文摘Apatite fission track （AFT） analysis on samples collected from a Paleozoic series is used to constrain the cooling history of the Bogda Mountain, northwest China. AFT ages range from 136.2 to 85.6 Ma and are younger than rock depositional ages and the mean confined track lengths （11.0 13.2 μm） mostly showing unimodal distribution are shorten, indicating significant track-annealing. Thermal histories modeling based on the distribution of fission-track lengths combined with the regional geological data show that two rapid cooling phases occurred in the latest Jurassic-early Cretaceous and the Oligocene-Miocene. Those new data together with previous published data show that the AFT ages become younger from the southwest to northeast in the western Bogda Mountain and its adjacent areas. The fission-track ages of the southwest area are relatively older （〉100 Ma）, recording the earlier rapid uplift phase during the late Jurassic-Cretaceous, while the ages in the north pied- mont of the Bogda Mountain （namely the northeast part） are younger （〈60 Ma）, mainly reflecting the later rapid uplift phase in the Oligocene-Miocene. The trend of younger AFT ages towards the northeast might be explained by post-Cretaceous large-scale crustal tilting towards the southwest. In the thrust fault-dominated northern limbs of the Bogda Mountain, AFT ages reveal a discontinuous pattern with age-jumps across the major fault zones, showing a possible strata tilting across each thrust faults due to the thrust ramps during the Cenozoic. The two rapid uplift stages might be related to the accretion and collision in the southern margin of the Asian continent during the late Jurassic and late Cenozoic, respectively.
基金Supported by the China Geological Survey Projects(DD20190106,DD20160203,DD20190090).
文摘Based on field geological survey,interpretation of seismic data and analysis of drilling and logging data,the evolution of geological structures,stratigraphic sedimentary filling sequence and sedimentary system around the Bogda Mountain were analyzed according to the idea of"structure controlling basin,basin controlling facies and facies controlling assemblages".The tectonic evolution of the basin around the Bogda Mountain can be divided into nine stages.The Middle-Late Permian–Middle-Late Triassic was the development stage of intracontinental rift,foreland basin and inland depression basin when lake,fan delta and braided river delta sedimentary facies developed.Early intracontinental rifting,late Permian tectonic uplift,and middle-late Triassic tectonic subsidence controlled the shape,type,subsidence rate and sedimentary system evolution of the basin.The Bogda Mountain area was the subsidence center and deposition center of the deep water lake basin in the Middle Permian with mainly deep-water deposition and local gravity flow deposition.This area had tectonic inversion in the Late Permian,when the Bogda Mountain uplifted to form a low bulge and a series of fan delta sand bodies.In the Middle-Late Triassic,subsidence occurred in the Bogda low uplift,characterized by extensive development of braided river delta deposits.
文摘The Bogda Shan orogenic belt is interpreted to be an Upper Palaeozoic continental rift, which was closed towards the end of the Carboniferous period. Intrusive activities in that belt are represented mainly by a large number of diabasic sills, dykes and stocks with sparse dioritic and granitic bodies. Determinations on a group of samples from the Shangdaheyan intrusion yielded a mineral\|rock Rb\|Sr isochron with an age of \{298.4±0.76\} Ma and an initial \{\{\}\+\{87\}Sr\}/\+\{86\}Sr ratio of 0.7041. In combination with field evidence, these results indicate that most of the intusions of the Bogda Shan orogenic belt were emplaced during the Hercynian cycle as a result of initial extension following rift closure, and that post\|Hercynian intrusive activities are not important in that belt.
文摘Fission-track dating evidence from 5 apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150-106 Ma), the uplift process of Mt. Bogda can be divided into four stages of thermal evolution: 150-106, 75-65, 44-24 and 13-9 Ma. Before 44-24 Ma, the cooling rate and uplifting rate of the southern and northern segments of Mt. Bogda are almost the same, showing that the uplifting of Mt. Bogda is an overall process. Since 44-24 Ma, the uplifting of the southern and northern segments of Mt. Bogda has shown differences. During 42-11 Ma, the northern segment of Mt. Bogda was at a steady stage, with the cooling rate being {0.03℃/Ma} and the uplifting rate being {0.001} mm/a. From 11 Ma to the present, the northern segment of Mt. Bogda was at a rapid cooling and uplifting stage, with the cooling rate being {5.72℃/Ma} and the uplifting rate being {0.19} mm/a. However, the southern segment of Mt. Bogda has been at a rapid cooling and uplifting stage since 26 Ma, with the cooling rate being {1.24℃/Ma} and the uplifting rate being {0.041} mm/a during 26-9 Ma; {4.88℃/Ma} and {0.163} mm/a from 9 Ma till now.
基金the National Basic Research Program of China (973 Program)(Grant No. 2007CB411305)National Science Foundation of China (Grant No. 40572116)National Project of Geological Survey (Grant No. 200113000078)
文摘The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evo
基金partially supported by Alfred Spreng Graduate Research Grant from Geology and Geophysics Program of Missouri University of Science and Technology to DYZby a U.S. National Science Foundation grant (IES-1714749) to WY。
文摘This study investigates the provenance of sedimentary rocks in Bogda Mountains, NW China, and reconstructs the lithology and unroofing history of the Eastern North Tianshan Suture. Petrographic point counting data of sandstones and compositions of conglomerates of upper Permian-lowermost Triassic Wutonggou low-order cycle from Zhaobishan, North Tarlong, Taodonggou, and Dalongkou sections in the southern and northern foothills of Bogda Mountains were used to interpret the temporal and spatial variations of lithology of the Eastern North Tianshan Suture, which is the sediment source area. Three compositional trends were identified. A trend of upwardincreasing quartz content and granitic pebbles in Zhaobishan section suggests a change from the undissected volcanic arc, accretionary wedge and trench setting to predominantly transitional volcanic arc and subordinate accretionary wedge and trench, in the eastern part of the Eastern North Tianshan Suture. In North Tarlong and Taodonggou sections, however, the lithic content decreases and the contents of quartz and granitic pebbles increase up sections. These trends indicate that the western part of the Eastern North Tianshan Suture changed from an undissected volcanic arc to the transitional volcanic arc, accretionary wedge and trench. No clear trend in the lithic-rich sandstones of the Dalongkou section indicates that sediments were derived from the undissected volcanic arc in the Eastern North Tianshan Suture and local rift shoulders. Compositional variations of studied rocks suggest that the Eastern North Tianshan Suture was an amalgamated complex with great spatial and temporal heterogeneities in lithology and experienced persistent unroofing during late Permian-earliest Triassic. This study reconstructs a key element of the Chinese Tianshan Suture and serves as an example to understand the unroofing processes of ancient sutures.
