Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experie...Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experienced significant seismic events,particularly along its northern boundary,highlighting the recurrent seismic activity in the Kyrgyz Republic.The Issyk-Ata fault,stretching 120 km from west to east in the northern Tien Shan,bounds from the north a young,growing anticline demarcating the foothills of the Kyrgyz Range and the Chui depression.This region is susceptible to strong earthquakes,posing a significant threat to the Chui region and Bishkek,the capital city with over a million residents.The youngest fault in the area is the Issyk-Ata fault,traversing the southern part of Bishkek,where modern construction has obscured its features.This study integrates remote sensing,detailed fieldwork,and paleoseismological investigations to map and analyze surface ruptures,quantify vertical displacements,and assess seismic hazards along the Issyk-Ata fault.Using optically stimulated luminescence and radiocarbon dating,we determined ages for documented paleoseismic events,placing two ancient earthquakes in the Holocene.Magnitude estimates suggest seismic events with magnitudes ranging from 6.6 to 7.1.In the Dzhal area,geological and geomorphological analysis yielded a longterm fault-slip rate of 1.15 mm/a.The Issyk-Ata fault shows variable rupture behavior,with distinct segments demonstrating different seismic characteristics and histories of activity.This variability necessitates comprehensive seismic hazard modeling to better understand and mitigate potential risks in the region.展开更多
Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrate...Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrated analysis of porosity,petrology,permeability,mineralogy,mercury injection,and stable isotopic data in core samples from the Permian Shan 2 and He 1 members(Shan 2—He 1 Mbr)in China's Ordos Basin.Early compaction and precipitation of diagenetic minerals have significantly reduced primary pore space in these members,although certain sandstones have retained anomalously high porosity.These high-porosity reservoirs have been shaped by many factors,with dissolution identified as the predominant mechanism.Detailed petrographic observations and assessments of the primary minerals,the minerals'genesis,and associated diagenetic processes revealed seven distinct diagenetic facies differentiated by their sand-grain populations,types of cementation,clay matrix contents,and volcanic tuffaceous sediment(VTS).The main interstitial fillings consist of VTS,clay minerals,quartz overgrowths,and calcite(ferrocalcite).Clasts and VTS-dissolved sandstone have mainly formed Class I reservoirs with highly unstable grains and good secondary pores resulting from the dissolution of the grains and VTS.VTS tight sandstone,siliceous cementation tight sandstone,illite-siliceous cementation tight sandstone,and calcite cementation tight sandstone have formed Class II reservoirs with high rates of interstitial filling and cementation.Sandstone tightly cemented by illite has poor reservoir properties and has mainly formed Class III reservoirs.This classification underscores the critical importance of understanding diagenesis,diagenetic facies,and especially the diagenetic features of VTS for accurately assessing reservoir quality.A comprehensive understanding of these factors may facilitate more effective hydrocarbon exploration and exploitation in this area.展开更多
0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapp...0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapponnier et al.,2001;Meyer et al.,1998).The northwest-trending mountain ranges in the Qilian Shan(“Shan”means“Mountain”in Chinese)have significantly influenced this deformation(Zheng et al.,2013).展开更多
The north-trending Liupan Shan （六盘山） is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and e...The north-trending Liupan Shan （六盘山） is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and environmental effects. In this article we report a new Late Cenozoic red earth section from an intermontane basin in the southern part of the Liupan Shan. Lithofacies analysis, paleomagnetic and fission-track chronologies, and paleocurrent analysis have been employed to identi- fy the tectonic uplift events of the Liupan Shan. Based on the age constraints of mammal fossils, the pa- leomagnetic polarity zones of the Huating （华亭） Section can be approximately correlated with the standard polarity zones that lie between C3An.2n and C5n.ln of the Geomagnetic Polar- ity Timescale; the bottom age of this section is approximately 10 Ma. Based on this and the previous studies, we infer that a tectonic event commenced in the southern Liupan Shan in this interval between 8.3 and 8.7 Ma, accompanied by a remarkable increase in sediment accumulation rate. Field observations, fission-track dating, determinations of grain-size frequency distribu- tions and the vertebrate fossils found there suggest that the red earth deposits were reworked by water and mainly transported by fluvial-alluvial processes from the adjacent area.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
Endemic to China, the Emei Shan Liocichla(Liocichla omeiensis) is considered globally vulnerable by the IUCN because of its small, declining population and fragmented range. The species has been recorded in only a few...Endemic to China, the Emei Shan Liocichla(Liocichla omeiensis) is considered globally vulnerable by the IUCN because of its small, declining population and fragmented range. The species has been recorded in only a few mountainous forests in south-central Sichuan and in the extreme northeast of Yunnan Province. We summarized the basic eco-biology information on its habitat,breeding, winter habits and behavior, voice, population status, research and conservation.展开更多
The Early Cretaceous Hohhot metamorphic core complex （mcc） of the Daqing Shan （Mtns.） of central Inner Mongolia is among the best exposed and most spectacular of the spatially isolated mcc＇s that developed within...The Early Cretaceous Hohhot metamorphic core complex （mcc） of the Daqing Shan （Mtns.） of central Inner Mongolia is among the best exposed and most spectacular of the spatially isolated mcc＇s that developed within the northern edge of the North China ＂craton＂. All of these mcc＇s were formed within the basement of a Late Paleozoic Andean-style arc and across older Mesozoic fold-and-thrust belts of variable age and tectonic vergence. The master Hohhot detachment fault roots southwards within the southem margin of the Daqing Shan for an along-strike distance of at least 120 km. Its geometry in the range to the north is complicated by interference patterns between （1） primary, large-scale NW-SE-trend- ing convex and concave fault corrugations and （2） secondary ENE-WSW-trending antiforms and syn- forms that folded the detachment in its late kinematic history. As in the Whipple Mtns. of California, the Hohhot master detachment is not of the Wernicke （1981） simple rooted type; instead, it was spawned from a mid-crustal shear zone, the top of which is preserved as a mylonitic front within Carboniferous metasedimentary rocks in its exhumed lower plate. 4~Ar-39Ar dating of siliceous volcanic rocks in basal sections of now isolated supradetachment basins suggest that crustal extension began at ca. 127 Ma, although lower-plate mylonitic rocks were not exposed to erosion until after ca. 119 Ma. Essentially synchronous cooling of bornblende, biotite, and muscovite in footwall mylonitic gneisses indicates very rapid exhumation and at ca. 122--120 Ma. Contrary to several recent reports, the master detachment clearly cuts across and dismembers older, north-directed thrust sheets of the Daqing Shah foreland fold-and-thrust belt. Folded and thrust-faulted basalts within its foredeep strata are as young as 132.6 ± 2.4 Ma, thus defining within 5--6 Ma the regional tectonic transition between crustal contraction and profound crustal extension.展开更多
There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, B...There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.展开更多
Black carbon （BC） concentration and meteorological data are measured discontinuously from May 2009 to March 2011,at the Qilian Shan Station of Glaciology and Ecologic Environment （hereafter ＂QSSGEE＂）,located nea...Black carbon （BC） concentration and meteorological data are measured discontinuously from May 2009 to March 2011,at the Qilian Shan Station of Glaciology and Ecologic Environment （hereafter ＂QSSGEE＂）,located near the terminal of the Laohugou No.12 Glacier in northwestern Qilian Shan,China.We measured the daily,monthly and seasonal variations of BC concentration in the atmosphere and discussed the possible emission sources.Black carbon background concentration in this region varied in the range of 18–72 ng/m 3 with the highest in summer and the lowest in autumn.The relations between BC concentration and surface wind direction indicated that BC concentration was higher when northwest wind prevails while lower when southeast wind prevails.Air masses backward trajectories showed the potential emission sources in the northwest.Significant positive correlations between daily mean BC concentration and relative humidity indicated that BC might be one of important cloud condensation nuclei.This hypothesis needs to be confirmed further through cloud microphysical features in this region.展开更多
The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion o...The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion of the Indochina block during and subsequent to the Indian-Eurasian collision.Diancang Shan（DCS） high-grade metamorphic complex,located at the northwest extension along the Ailao Shan-Red River（ASRR） shear zone,is a representative metamorphic complex of the ASRR tectonic belt.Structural and microstructural analysis of sheared rocks in the high-grade metamorphic rocks reveals that they are coherent with solid-state high-temperature ductile deformation,which is attributed to left-lateral shearing along the ASRR shear zone.New LA-ICP-MS zircon U-Pb geochronological and microstructural studies of the post-kinematic granitic plutons provide a straightforward time constraint on the termination ductile left-lateral shearing and exhumation of the metamorphic massif in the ASRR shear zone.It is suggested that the left-lateral shearing along the ASRR shear zone ended at ca.21 Ma at relative lower-temperature or decreasing temperature conditions.During or after the emplacement of the young dikes at ca.21 Ma,rapid brittle deformation event occurred,which makes the DCS massif start fast uplift/exhumation and cooling to a shallow crustal level.展开更多
This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the se...This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the second place, we also present new detrital apatite fission track data on the Meso-Cenozoic sediments from fault related basins and surrounding intramontane basins. Our results confirm multistaged Meso-Cenozoic tectonic activity, possibly induced by the accretion of the so-called Cimmerian blocks to the Eurasian margin. New evidence for this multi-staged thermo-tectonic activity is found in the data of both basement and Meso-Cenozoic sediment samples in or close to the Talas-Fergana Fault.Zircon(U-Th)/He and apatite fission track data constrain rapid Late TriassiceE arly Jurassic and Late JurassiceE arly Cretaceous basement cooling in the Kyrgyz Tien Shan around 200 Ma and 130 -100 Ma respectively. Detrital apatite fission track results indicate a different burial history on both sides of the Talas-Fergana Fault. The apatite fission track system of the Jurassic sediments in the Middle Tien Shan unit east of the Talas-Fergana Fault is not reset, while the Jurassic sediments in the Fergana Basin and Yarkand-Fergana Basin, west of the fault zone, are partially and in some cases even totally reset. The totally reset samples exhibit Oligocene and Miocene ages and evidence the Cenozoic reactivation of the western Kyrgyz Tien Shan as a consequence of the India-Eurasia convergence.展开更多
By analyzing the deep seismic sounding profiles across the Longmen Shan,this paper focuses on the study of the relationship between the upper crust structure of the Longmen Shan area and the Wenchuan earthquake.The Lo...By analyzing the deep seismic sounding profiles across the Longmen Shan,this paper focuses on the study of the relationship between the upper crust structure of the Longmen Shan area and the Wenchuan earthquake.The Longmen Shan thrust belt marks not only the topographical change,but also the lateral velocity variation between the eastern Tibetan Plateau and the Sichuan Basin.A low-velocity layer has consistently been found in the crust beneath the eastern edge of the Tibetan Plateau,and ends beneath the western Sichuan Basin.The low-velocity layer at a depth of-20 km beneath the eastern edge of the Tibetan Plateau has been considered as the deep condition for favoring energy accumulation that formed the great Wenchuan earthquake.展开更多
The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in t...The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.展开更多
基金financial support of the Faculty Research Grant project of the American University of Central Asia(AUCA)supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF-2023S1A5B5A16080131)。
文摘Geodetic observations over the past several decades identify the Tien Shan as a prominent and active intracontinental mountain belt,characterized by a meridional shortening rate of up to 20 mm/a.The region has experienced significant seismic events,particularly along its northern boundary,highlighting the recurrent seismic activity in the Kyrgyz Republic.The Issyk-Ata fault,stretching 120 km from west to east in the northern Tien Shan,bounds from the north a young,growing anticline demarcating the foothills of the Kyrgyz Range and the Chui depression.This region is susceptible to strong earthquakes,posing a significant threat to the Chui region and Bishkek,the capital city with over a million residents.The youngest fault in the area is the Issyk-Ata fault,traversing the southern part of Bishkek,where modern construction has obscured its features.This study integrates remote sensing,detailed fieldwork,and paleoseismological investigations to map and analyze surface ruptures,quantify vertical displacements,and assess seismic hazards along the Issyk-Ata fault.Using optically stimulated luminescence and radiocarbon dating,we determined ages for documented paleoseismic events,placing two ancient earthquakes in the Holocene.Magnitude estimates suggest seismic events with magnitudes ranging from 6.6 to 7.1.In the Dzhal area,geological and geomorphological analysis yielded a longterm fault-slip rate of 1.15 mm/a.The Issyk-Ata fault shows variable rupture behavior,with distinct segments demonstrating different seismic characteristics and histories of activity.This variability necessitates comprehensive seismic hazard modeling to better understand and mitigate potential risks in the region.
基金supported by the National Natural Science Foundation of China:Tethys Dynamics(Grant No.92255302)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA14010201)the China Scholarship Council(Grant No.202206400023).
文摘Understanding diagenetic processes plays a crucial role in evaluating the quality of tight reservoirs.In this study,we aimed to examine diagenetic facies and thereby assess reservoir quality by conducting an integrated analysis of porosity,petrology,permeability,mineralogy,mercury injection,and stable isotopic data in core samples from the Permian Shan 2 and He 1 members(Shan 2—He 1 Mbr)in China's Ordos Basin.Early compaction and precipitation of diagenetic minerals have significantly reduced primary pore space in these members,although certain sandstones have retained anomalously high porosity.These high-porosity reservoirs have been shaped by many factors,with dissolution identified as the predominant mechanism.Detailed petrographic observations and assessments of the primary minerals,the minerals'genesis,and associated diagenetic processes revealed seven distinct diagenetic facies differentiated by their sand-grain populations,types of cementation,clay matrix contents,and volcanic tuffaceous sediment(VTS).The main interstitial fillings consist of VTS,clay minerals,quartz overgrowths,and calcite(ferrocalcite).Clasts and VTS-dissolved sandstone have mainly formed Class I reservoirs with highly unstable grains and good secondary pores resulting from the dissolution of the grains and VTS.VTS tight sandstone,siliceous cementation tight sandstone,illite-siliceous cementation tight sandstone,and calcite cementation tight sandstone have formed Class II reservoirs with high rates of interstitial filling and cementation.Sandstone tightly cemented by illite has poor reservoir properties and has mainly formed Class III reservoirs.This classification underscores the critical importance of understanding diagenesis,diagenetic facies,and especially the diagenetic features of VTS for accurately assessing reservoir quality.A comprehensive understanding of these factors may facilitate more effective hydrocarbon exploration and exploitation in this area.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0901)the State Key Laboratory of Earthquake Dynamics(No.LED2023B04)+1 种基金the National Natural Science Foundation of China(Nos.42272242,W2411033,W2521003)the Science and Technology Plan of Gansu Province(No.22JR11RA088)。
文摘0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapponnier et al.,2001;Meyer et al.,1998).The northwest-trending mountain ranges in the Qilian Shan(“Shan”means“Mountain”in Chinese)have significantly influenced this deformation(Zheng et al.,2013).
基金supported by the National Natural Science Foundation of China (Nos. 41290253, 40772116)the National Basic Research Program of China (973 Projects) (Nos.2010CB83340, 2013CB955904)
文摘The north-trending Liupan Shan （六盘山） is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and environmental effects. In this article we report a new Late Cenozoic red earth section from an intermontane basin in the southern part of the Liupan Shan. Lithofacies analysis, paleomagnetic and fission-track chronologies, and paleocurrent analysis have been employed to identi- fy the tectonic uplift events of the Liupan Shan. Based on the age constraints of mammal fossils, the pa- leomagnetic polarity zones of the Huating （华亭） Section can be approximately correlated with the standard polarity zones that lie between C3An.2n and C5n.ln of the Geomagnetic Polar- ity Timescale; the bottom age of this section is approximately 10 Ma. Based on this and the previous studies, we infer that a tectonic event commenced in the southern Liupan Shan in this interval between 8.3 and 8.7 Ma, accompanied by a remarkable increase in sediment accumulation rate. Field observations, fission-track dating, determinations of grain-size frequency distribu- tions and the vertebrate fossils found there suggest that the red earth deposits were reworked by water and mainly transported by fluvial-alluvial processes from the adjacent area.
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 projects of the Sichuan Provincial Science&Technology Department(2011JYZ008)the Sichuan Provincial Education Department(11ZA155)Leshan Normal University(Z1158)
文摘Endemic to China, the Emei Shan Liocichla(Liocichla omeiensis) is considered globally vulnerable by the IUCN because of its small, declining population and fragmented range. The species has been recorded in only a few mountainous forests in south-central Sichuan and in the extreme northeast of Yunnan Province. We summarized the basic eco-biology information on its habitat,breeding, winter habits and behavior, voice, population status, research and conservation.
基金sponsored by National Science Foundation grants EAR-9627909 and EAR-9903012 to Davisa China National Natural Sciences Foundation grant to Zheng+1 种基金a Louisiana State University research grant to DarbyRadiometric dating was done by George Gehrels of the University of Arizona(U-Pb) and by Terry Spell of the Nevada Isotope Geochronology Laboratory (Ar/Ar,funded in part by NSF grant EPS-9720162)
文摘The Early Cretaceous Hohhot metamorphic core complex （mcc） of the Daqing Shan （Mtns.） of central Inner Mongolia is among the best exposed and most spectacular of the spatially isolated mcc＇s that developed within the northern edge of the North China ＂craton＂. All of these mcc＇s were formed within the basement of a Late Paleozoic Andean-style arc and across older Mesozoic fold-and-thrust belts of variable age and tectonic vergence. The master Hohhot detachment fault roots southwards within the southem margin of the Daqing Shan for an along-strike distance of at least 120 km. Its geometry in the range to the north is complicated by interference patterns between （1） primary, large-scale NW-SE-trend- ing convex and concave fault corrugations and （2） secondary ENE-WSW-trending antiforms and syn- forms that folded the detachment in its late kinematic history. As in the Whipple Mtns. of California, the Hohhot master detachment is not of the Wernicke （1981） simple rooted type; instead, it was spawned from a mid-crustal shear zone, the top of which is preserved as a mylonitic front within Carboniferous metasedimentary rocks in its exhumed lower plate. 4~Ar-39Ar dating of siliceous volcanic rocks in basal sections of now isolated supradetachment basins suggest that crustal extension began at ca. 127 Ma, although lower-plate mylonitic rocks were not exposed to erosion until after ca. 119 Ma. Essentially synchronous cooling of bornblende, biotite, and muscovite in footwall mylonitic gneisses indicates very rapid exhumation and at ca. 122--120 Ma. Contrary to several recent reports, the master detachment clearly cuts across and dismembers older, north-directed thrust sheets of the Daqing Shah foreland fold-and-thrust belt. Folded and thrust-faulted basalts within its foredeep strata are as young as 132.6 ± 2.4 Ma, thus defining within 5--6 Ma the regional tectonic transition between crustal contraction and profound crustal extension.
基金This research was supported by the National Nature Foundation of China （49803031, 40372084） the Seismic Scientific United Fund （95-07-0425）+3 种基金 US National Science Foundation grant EAR-0125565 ETH Forschungskommission grant TH-4/03-01 Key Subject Program of Sichuan province Grant No. SZD0408 and the Program for the Subject of Ph.D. in Higher Education Institute, Grant No.20050616004.
文摘There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.
基金supported by the Global Change Research Program of China (No. 2010CB951401)the "Talent Project" of Chinese Academy of Sciences,National Natural Science Foundation of China (No. 40901046)+1 种基金the State Key Laboratory of Cryospheric Sciences (No. SKLCS-ZZ-2008-01)the China Meteorological Administration (No. GYHY201106023)
文摘Black carbon （BC） concentration and meteorological data are measured discontinuously from May 2009 to March 2011,at the Qilian Shan Station of Glaciology and Ecologic Environment （hereafter ＂QSSGEE＂）,located near the terminal of the Laohugou No.12 Glacier in northwestern Qilian Shan,China.We measured the daily,monthly and seasonal variations of BC concentration in the atmosphere and discussed the possible emission sources.Black carbon background concentration in this region varied in the range of 18–72 ng/m 3 with the highest in summer and the lowest in autumn.The relations between BC concentration and surface wind direction indicated that BC concentration was higher when northwest wind prevails while lower when southeast wind prevails.Air masses backward trajectories showed the potential emission sources in the northwest.Significant positive correlations between daily mean BC concentration and relative humidity indicated that BC might be one of important cloud condensation nuclei.This hypothesis needs to be confirmed further through cloud microphysical features in this region.
基金support from the State Key Research"973"Plan of China(No. 2009CB421001)National Natural Science Foundation of China(40872139)+1 种基金the 111 Project(B07011) of the Ministry of Education,State Key Laboratory of Geological Processes and Mineral Resources (GPMR200837)the Fundamental Research Funds for the Central Universities(GPMR2009PY01)
文摘The Ailao Shan-Red River fault zone is the boundary between the Yangtze block to the northeast and the Indochina block to the southwest.It is an important tectonic zone due to its role in the southeastward extrusion of the Indochina block during and subsequent to the Indian-Eurasian collision.Diancang Shan（DCS） high-grade metamorphic complex,located at the northwest extension along the Ailao Shan-Red River（ASRR） shear zone,is a representative metamorphic complex of the ASRR tectonic belt.Structural and microstructural analysis of sheared rocks in the high-grade metamorphic rocks reveals that they are coherent with solid-state high-temperature ductile deformation,which is attributed to left-lateral shearing along the ASRR shear zone.New LA-ICP-MS zircon U-Pb geochronological and microstructural studies of the post-kinematic granitic plutons provide a straightforward time constraint on the termination ductile left-lateral shearing and exhumation of the metamorphic massif in the ASRR shear zone.It is suggested that the left-lateral shearing along the ASRR shear zone ended at ca.21 Ma at relative lower-temperature or decreasing temperature conditions.During or after the emplacement of the young dikes at ca.21 Ma,rapid brittle deformation event occurred,which makes the DCS massif start fast uplift/exhumation and cooling to a shallow crustal level.
基金supported by a Ghent University project (BOF 015B1309)the DARIUS program+2 种基金supported by ARC DP150101730TRAX record 387. F.Isupported by state assignment project No. 0330-2016-0015
文摘This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the second place, we also present new detrital apatite fission track data on the Meso-Cenozoic sediments from fault related basins and surrounding intramontane basins. Our results confirm multistaged Meso-Cenozoic tectonic activity, possibly induced by the accretion of the so-called Cimmerian blocks to the Eurasian margin. New evidence for this multi-staged thermo-tectonic activity is found in the data of both basement and Meso-Cenozoic sediment samples in or close to the Talas-Fergana Fault.Zircon(U-Th)/He and apatite fission track data constrain rapid Late TriassiceE arly Jurassic and Late JurassiceE arly Cretaceous basement cooling in the Kyrgyz Tien Shan around 200 Ma and 130 -100 Ma respectively. Detrital apatite fission track results indicate a different burial history on both sides of the Talas-Fergana Fault. The apatite fission track system of the Jurassic sediments in the Middle Tien Shan unit east of the Talas-Fergana Fault is not reset, while the Jurassic sediments in the Fergana Basin and Yarkand-Fergana Basin, west of the fault zone, are partially and in some cases even totally reset. The totally reset samples exhibit Oligocene and Miocene ages and evidence the Cenozoic reactivation of the western Kyrgyz Tien Shan as a consequence of the India-Eurasia convergence.
基金financed by International Sciences and Technology cooperation(2006DFA21340)the special funds for Sciences and technology research of public welfare trades(200811021)+2 种基金the key innovation project for sciences and technology of ministry of land and resources(1212010711813)the Basic outlay of scientific research work from Ministry of Science and Technology of the People's Republic of China(J0803)the National Natural Science Foundation of China(40830316 and 40874045)and SINOPPROBE-02
文摘By analyzing the deep seismic sounding profiles across the Longmen Shan,this paper focuses on the study of the relationship between the upper crust structure of the Longmen Shan area and the Wenchuan earthquake.The Longmen Shan thrust belt marks not only the topographical change,but also the lateral velocity variation between the eastern Tibetan Plateau and the Sichuan Basin.A low-velocity layer has consistently been found in the crust beneath the eastern edge of the Tibetan Plateau,and ends beneath the western Sichuan Basin.The low-velocity layer at a depth of-20 km beneath the eastern edge of the Tibetan Plateau has been considered as the deep condition for favoring energy accumulation that formed the great Wenchuan earthquake.
基金supported by the National Science Foundation of China(41874117)the Second Tibetan Plateau Scientific Expedition and Research Program(SETP)(2019QZKK0901)Natural Science Basic Research Program of Shaanxi(Program No.2023-JC-ON-0309)。
文摘The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.
