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
Eolian loess is widely distributed on the various geomorphic surfaces between 700-2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut...Eolian loess is widely distributed on the various geomorphic surfaces between 700-2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin. The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over 71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic Bruhues/Matuy-ama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was estimated to be -0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion experienced two dramatic periods of desert expansions that occurred at -0.65 Ma and 0.5 Ma, respectively; and the subsequent continuous展开更多
Determining the spatio-temporal distribution of the deformation tied to the India-Eurasian convergence and the impact of pre-existing weaknesses on the Cenozoic crustal deformation is significant for understanding how...Determining the spatio-temporal distribution of the deformation tied to the India-Eurasian convergence and the impact of pre-existing weaknesses on the Cenozoic crustal deformation is significant for understanding how the convergence between India and Eurasia contributed to the development of the Tibetan Plateau. The exhumation history of the northeastern Tibetan Plateau was addressed in this research using a new apatite fission track （AFT） study in the North Qaidam thrust belt （NQTB）. Three granite samples collected from the Qaidam Shan pluton in the north tied to the Qaidam Shan thrust, with AFT ages clustering in the Eocene to Miocene. The other thirteen samples obtained from the Luliang Shan and Yuka plutons in the south related to the Luliang Shan thrust and they have showed predominantly the Cretaceous AFT ages. Related thermal history modeling based on grain ages and track lengths indicates rapid cooling events during the Eocene-early Oligocene and since late Miocene within the Qaidam Shan, in contrast to those in the Cretaceous and since the Oligocene-Miocene in the Luliang Shan and Yuka region. The results, combined with published the Cretaceous thermochronological ages in the Qaidam Shan region, suggest that the NQTB had undergo rapid exhumation during the accretions along the southern Asian Andean-type margin prior to the India-Eurasian collision. The Cenozoic deformation initially took place in the North Qaidam thrust belt by the Eocene, which is consistent with the recent claim that the deformation of the northeastern Tibetan Plateau initiated in the Eocene as a response to continental collision between India and Eurasia. The immediate deformation responding to the collision is tentatively attributed to the preexisting weaknesses of the lithosphere, and therefore the deformation of the northeastern Tibetan Plateau should be regarded as a boundary-condition-dependent process.展开更多
From April of 2001 to March of 2002, a passive seismic array experiment was car- ried out in the Dabie Shan and its adjacent region. In this experiment, totally 34 broadband seismic stations were deployed along a prof...From April of 2001 to March of 2002, a passive seismic array experiment was car- ried out in the Dabie Shan and its adjacent region. In this experiment, totally 34 broadband seismic stations were deployed along a profile across the Dabie Shan orogen and North-China platform. This profile is about 500 km long from Cuilin (34°40′N, 114°49′E), Henan Province, to Dajipu (30°20′N, 115°03′E), Hubei Province. The space between stations is about 3?8 km in the Dabie Shan orogenic belt and about 15?20 km in other area. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km depth along the profile are investigated in terms of the receiver function techniques (Liu et al., 1996, 2000). Our results show that the crust beneath the Dabie Shan orogen has an obviously asymmetric blocked structure in the direction perpendicular to the mountain strike. The maximal crustal thickness reaches to 42 km. The crust-mantle boundary has a dislocation structure correlated to the crustal blocks and the largest offset reaches to 8 km. In the kernel of the orogen exists a low-velocity body inside the crust, which is separated into two parts corresponding to the South Dabie and North Dabie on the surface, respectively. Probably a vertical divergent movement between both took place in history. The crust below this low-velocity area has a positive gradient velocity structure with the depth, and the upper mantle down to the depth of 70 km has the lower S-wave velocity than its both sides. Beneath the Dabie Shan, however, a high-velocity anomaly exists in the upper mantle below 70 km.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 ...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
Small thrust faults in the Daqing Shan that were previously mapped as separate structures belong to a single Mesozoic thrust, herein named the Daqing Shan thrust. It extends more than 155 km along the northern margin ...Small thrust faults in the Daqing Shan that were previously mapped as separate structures belong to a single Mesozoic thrust, herein named the Daqing Shan thrust. It extends more than 155 km along the northern margin of the Daqing Shan, obliquely cutting the Daqing Shan along the western flank of the Jinluandian peak to the southeast and taking its way to Chayouzhongqi to the east. Kinematic markers indicate tectonic transport of the thrust sheet to the NNW. Minimum displacement, based on the observable outcrops, is 22 km, and the inferred thrusting distance may be larger than 35 km. The thrust sheet covers the whole eastern area of the Daqing Shan. The thrust truncates the E-W trending, somewhat older South-directed Panyanshan thrust and, therefore, the two faults are not as a result of counter thrusting. Such major intraplate tectonic deformation that occurred in the Inner Mongolia Axis or the Yin Shan latitudinal tectonic belt during late Jurassic time calls for deep thought on its tectonic significance in dynamics. It is most likely that the Daqing Shan thrust represents major intraplate shortening during Jurassic-Cretaceous closure of the Mongolo-Okhotsk ocean about 1000 krn away to the north.展开更多
Six granite samples were collected from six difference elevation locations at the Hua Shan in a main ridge of the Qinling Mountain. Apatite and zircon separated from these six samples were dated by the fission track t...Six granite samples were collected from six difference elevation locations at the Hua Shan in a main ridge of the Qinling Mountain. Apatite and zircon separated from these six samples were dated by the fission track technique. An assessment of the Cenozoic uplift or exhumation rate was obtained from the altitude difference of sampling samples dated by fission track, and from the difference of fission track dates of both apatite and zircon for a sample. The preliminary results suggest that the beginning of uplift of the Hua Shan was as early as 68.2 MaBP and the uplift rates for different periods are 0.02-0.19 mm/a (from the elevation difference) or 0.12-0.16 mm/a (from two mineral fission track dates). The average uplift rate is 0.12 mm/a (from the elevation difference) or 0.14 mm/a (from two mineral fission track dates). The uplift of the Hua Shan might accelerate since (17.8±2.0) MaBP, and the average uplift rate is about 0.19 mm/a.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
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
Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS...Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS) in an attempt to understand the processes that control their behavior. Glaciers over the recent 40 years(1970-2010) have shrunk 3.4±3.1%in area, based on a comparison between two Chinese glacier inventories. Variations of surface elevations, derived from ICESat-GLAS(Ice, Cloud, and Land Elevation Satellite-Geoscience Laser Altimeter System) elevation products(GLA14 data) using the robust linear-fit method, indicate that the glaciers have been gaining mass at a rate of 0.23±0.24 m w.e./a since 2003. The annual mass budget for the whole WKS range from 2003 to 2009 is estimated to be 0.71±0.62 Gt/a. This gain trend is confirmed by MOD10A1 albedo for the WKS region which shows a descent of the mean snowline altitude from 2003 to 2009.展开更多
A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed...A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of -2 km. The high-resolution P-velocity model revealed interesting structures in the seismogenic layer： （1） The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; （2） The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least -10 km from the surface; （3） A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif＇s western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; （4） Vicinity along the Yingxiu- Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; （5） Two blocks of low-velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a -7 km offset with -5 km vertical component.展开更多
Forests are important ecosystems for economic and social development.However,the response of tree radial growth to climate has produced‘divergent problems'at high latitudes under global warming.In this study,the ...Forests are important ecosystems for economic and social development.However,the response of tree radial growth to climate has produced‘divergent problems'at high latitudes under global warming.In this study,the response stability and trend of Picea schrenkiana radial growth to variability in climate factors were analyzed in the mid-latitudes of the western Tien Shan Mountains.Radial growth of P.schrenkiana was mainly limited by minimum and mean temperatures.The divergent responses of radial growth occurred in response to the minimum and mean temperatures at the beginning of the growing season(April–May)of the current year,but responses to drought occurred in July–September of the previous year.And the mean and minimum temperatures in June–September of the current year were both stable.Radial growth first increased and then decreased according to the basal area increment,with a gradual increase in temperature.Therefore,forest ecosystems in mountainous arid areas will be increasingly affected by future climate warming.展开更多
Based on paleomagnetic measurements and morphostratigraphy of red bed/clay sequences from pediments of the Liupan Shan and the Longdong Basin, the following results are revealed. The red bed/clay sediments became to a...Based on paleomagnetic measurements and morphostratigraphy of red bed/clay sequences from pediments of the Liupan Shan and the Longdong Basin, the following results are revealed. The red bed/clay sediments became to accumulate at around 8.1 MaBP, which implied that the plantation surface developed since Late Cretaceous was broken by active fault, and its development was terminated. The Liupan Shan began to slightly uplift. The Liupan Shan experienced a small-scale uplift around 5.2 MaBP, inferred from the appearance of fine gravel sediments at that time. Consequently, a pediment was developed. The Liupan Shan accelerated uplift since about 3.8 MaBP at a large scale, which caused the deep incision of the rivers and the termination of fluvial and lacustrine deposition. Meanwhile, typical eolian red clay appeared since then. This uplift process is well correlated and in response to that of the Tibetan Plateau and the mountains around it.展开更多
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This work was co-supported by China's 'Excellent Researchers Fund' of the National Natural Science Foundation of China (Grant No. 49928J01)'Hundred Talents Project' of the Chinese Academy of Sciences (Renjiaozi[2000]005)the National Tibetan Project (
文摘Eolian loess is widely distributed on the various geomorphic surfaces between 700-2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin. The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over 71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic Bruhues/Matuy-ama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was estimated to be -0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion experienced two dramatic periods of desert expansions that occurred at -0.65 Ma and 0.5 Ma, respectively; and the subsequent continuous
基金funded by the National Science Foundation of China(Grant No.41102128,41330207,41372206,41472181,and 41402170)the National S&T Major Project(Grant No.2016ZX05008-001 and 2016ZX05003-001)+1 种基金Research Funds from Bureau of Education Zhejiang Province(Grant No.Y201019040)the Fundamental Research Funds for the Central Universities(Grant No.2016FZA3007)
文摘Determining the spatio-temporal distribution of the deformation tied to the India-Eurasian convergence and the impact of pre-existing weaknesses on the Cenozoic crustal deformation is significant for understanding how the convergence between India and Eurasia contributed to the development of the Tibetan Plateau. The exhumation history of the northeastern Tibetan Plateau was addressed in this research using a new apatite fission track （AFT） study in the North Qaidam thrust belt （NQTB）. Three granite samples collected from the Qaidam Shan pluton in the north tied to the Qaidam Shan thrust, with AFT ages clustering in the Eocene to Miocene. The other thirteen samples obtained from the Luliang Shan and Yuka plutons in the south related to the Luliang Shan thrust and they have showed predominantly the Cretaceous AFT ages. Related thermal history modeling based on grain ages and track lengths indicates rapid cooling events during the Eocene-early Oligocene and since late Miocene within the Qaidam Shan, in contrast to those in the Cretaceous and since the Oligocene-Miocene in the Luliang Shan and Yuka region. The results, combined with published the Cretaceous thermochronological ages in the Qaidam Shan region, suggest that the NQTB had undergo rapid exhumation during the accretions along the southern Asian Andean-type margin prior to the India-Eurasian collision. The Cenozoic deformation initially took place in the North Qaidam thrust belt by the Eocene, which is consistent with the recent claim that the deformation of the northeastern Tibetan Plateau initiated in the Eocene as a response to continental collision between India and Eurasia. The immediate deformation responding to the collision is tentatively attributed to the preexisting weaknesses of the lithosphere, and therefore the deformation of the northeastern Tibetan Plateau should be regarded as a boundary-condition-dependent process.
基金the National Natural Science Foundation of China(Grant No.40074009) the Deutsche Forschungsgemein-schaft.
文摘From April of 2001 to March of 2002, a passive seismic array experiment was car- ried out in the Dabie Shan and its adjacent region. In this experiment, totally 34 broadband seismic stations were deployed along a profile across the Dabie Shan orogen and North-China platform. This profile is about 500 km long from Cuilin (34°40′N, 114°49′E), Henan Province, to Dajipu (30°20′N, 115°03′E), Hubei Province. The space between stations is about 3?8 km in the Dabie Shan orogenic belt and about 15?20 km in other area. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km depth along the profile are investigated in terms of the receiver function techniques (Liu et al., 1996, 2000). Our results show that the crust beneath the Dabie Shan orogen has an obviously asymmetric blocked structure in the direction perpendicular to the mountain strike. The maximal crustal thickness reaches to 42 km. The crust-mantle boundary has a dislocation structure correlated to the crustal blocks and the largest offset reaches to 8 km. In the kernel of the orogen exists a low-velocity body inside the crust, which is separated into two parts corresponding to the South Dabie and North Dabie on the surface, respectively. Probably a vertical divergent movement between both took place in history. The crust below this low-velocity area has a positive gradient velocity structure with the depth, and the upper mantle down to the depth of 70 km has the lower S-wave velocity than its both sides. Beneath the Dabie Shan, however, a high-velocity anomaly exists in the upper mantle below 70 km.
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.
文摘Small thrust faults in the Daqing Shan that were previously mapped as separate structures belong to a single Mesozoic thrust, herein named the Daqing Shan thrust. It extends more than 155 km along the northern margin of the Daqing Shan, obliquely cutting the Daqing Shan along the western flank of the Jinluandian peak to the southeast and taking its way to Chayouzhongqi to the east. Kinematic markers indicate tectonic transport of the thrust sheet to the NNW. Minimum displacement, based on the observable outcrops, is 22 km, and the inferred thrusting distance may be larger than 35 km. The thrust sheet covers the whole eastern area of the Daqing Shan. The thrust truncates the E-W trending, somewhat older South-directed Panyanshan thrust and, therefore, the two faults are not as a result of counter thrusting. Such major intraplate tectonic deformation that occurred in the Inner Mongolia Axis or the Yin Shan latitudinal tectonic belt during late Jurassic time calls for deep thought on its tectonic significance in dynamics. It is most likely that the Daqing Shan thrust represents major intraplate shortening during Jurassic-Cretaceous closure of the Mongolo-Okhotsk ocean about 1000 krn away to the north.
基金This work was supported by the NationalNatural Science Foundation of China (Grant Nos. 49732090 and 49872062).
文摘Six granite samples were collected from six difference elevation locations at the Hua Shan in a main ridge of the Qinling Mountain. Apatite and zircon separated from these six samples were dated by the fission track technique. An assessment of the Cenozoic uplift or exhumation rate was obtained from the altitude difference of sampling samples dated by fission track, and from the difference of fission track dates of both apatite and zircon for a sample. The preliminary results suggest that the beginning of uplift of the Hua Shan was as early as 68.2 MaBP and the uplift rates for different periods are 0.02-0.19 mm/a (from the elevation difference) or 0.12-0.16 mm/a (from two mineral fission track dates). The average uplift rate is 0.12 mm/a (from the elevation difference) or 0.14 mm/a (from two mineral fission track dates). The uplift of the Hua Shan might accelerate since (17.8±2.0) MaBP, and the average uplift rate is about 0.19 mm/a.
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 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supported by a National Science Foundation of China major project (Grant No. 41190084) funded by the National Natural Science Foundation of Chinathe National Key Technology R&D Program (Grant No. 2012BAC19B07)+2 种基金the International S&T Cooperation Program of the Ministry of Science and Technology of China (Grant No. 2010DFA92720-23)provided by the MOST (Grant No. 2006FY110200)CAS projects (Grant No. KZCX2-YW-301)
文摘Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS) in an attempt to understand the processes that control their behavior. Glaciers over the recent 40 years(1970-2010) have shrunk 3.4±3.1%in area, based on a comparison between two Chinese glacier inventories. Variations of surface elevations, derived from ICESat-GLAS(Ice, Cloud, and Land Elevation Satellite-Geoscience Laser Altimeter System) elevation products(GLA14 data) using the robust linear-fit method, indicate that the glaciers have been gaining mass at a rate of 0.23±0.24 m w.e./a since 2003. The annual mass budget for the whole WKS range from 2003 to 2009 is estimated to be 0.71±0.62 Gt/a. This gain trend is confirmed by MOD10A1 albedo for the WKS region which shows a descent of the mean snowline altitude from 2003 to 2009.
基金the Basic Research Foundation of the Institute of Geomechanics,CAGS(grant DZLXJK200707)Natural Science Foundation of China grant 40674058)
文摘A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of -2 km. The high-resolution P-velocity model revealed interesting structures in the seismogenic layer： （1） The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; （2） The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least -10 km from the surface; （3） A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif＇s western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; （4） Vicinity along the Yingxiu- Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; （5） Two blocks of low-velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a -7 km offset with -5 km vertical component.
基金supported by the National Natural Science Foundation of China(Projects Nos.41861006 and 41630750)the Scientific Research Program of Higher Education Institutions of Gansu Province(2018C-02)the Research Ability Promotion Program for Young Teachers of Northwest Normal University(NWNU-LKQN2019-4)。
文摘Forests are important ecosystems for economic and social development.However,the response of tree radial growth to climate has produced‘divergent problems'at high latitudes under global warming.In this study,the response stability and trend of Picea schrenkiana radial growth to variability in climate factors were analyzed in the mid-latitudes of the western Tien Shan Mountains.Radial growth of P.schrenkiana was mainly limited by minimum and mean temperatures.The divergent responses of radial growth occurred in response to the minimum and mean temperatures at the beginning of the growing season(April–May)of the current year,but responses to drought occurred in July–September of the previous year.And the mean and minimum temperatures in June–September of the current year were both stable.Radial growth first increased and then decreased according to the basal area increment,with a gradual increase in temperature.Therefore,forest ecosystems in mountainous arid areas will be increasingly affected by future climate warming.
基金the Hundred Talents Project of CAS(Renjiaozi[2000]05), the National Key Projects for Basic Research on the Tibetan Plateau (Grant No. G1998040809) and MOE Key Projects on Sci-Technologic Research.
文摘Based on paleomagnetic measurements and morphostratigraphy of red bed/clay sequences from pediments of the Liupan Shan and the Longdong Basin, the following results are revealed. The red bed/clay sediments became to accumulate at around 8.1 MaBP, which implied that the plantation surface developed since Late Cretaceous was broken by active fault, and its development was terminated. The Liupan Shan began to slightly uplift. The Liupan Shan experienced a small-scale uplift around 5.2 MaBP, inferred from the appearance of fine gravel sediments at that time. Consequently, a pediment was developed. The Liupan Shan accelerated uplift since about 3.8 MaBP at a large scale, which caused the deep incision of the rivers and the termination of fluvial and lacustrine deposition. Meanwhile, typical eolian red clay appeared since then. This uplift process is well correlated and in response to that of the Tibetan Plateau and the mountains around it.
