Tienshan Mountains Research Articles

Methane-rich fluid inclusions from ophiolitic dunite and post-collisional mafic–ultramafic intrusion: The mantle dynamics underneath the Palaeo-Asian Ocean through to the post-collisional period

The protracted development history of the Palaeo-Asian Ocean starting from ∼1000 Ma to ∼320 Ma, and continuation of mantle-derived magmatism right through the post-collisional period as manifested by the widespread mafic–ultramafic intrusion and alkaline–peralkaline granite suggest a vigorous, long-running mantle dynamo. Using the micro-laser Raman spectrometer, we analyzed olivine- and plagioclase-hosted fluid inclusions from ophiolitic dunite, Kudi of the western Kunlun Range, and post-collisional mafic–ultramafic intrusions of the Xiangshan and the Huangshandong, eastern Chinese Tienshan Mountains. Our results show that fluids brought from the mantle by these rocks are rich in H 2 O and CH 4 with variable amounts of N 2 . Estimation of the redox state, pressure and depth of formation for the melt–CH 4 –H 2 O + N 2 fluid systems from the 3 rock suites of the Xinjiang, and comparison of these parameters with those of the peridotite–fluid parageneses for the sub-cratonic upper mantle give meaningful results. These fluids were formed in the asthenosphere, were originally CH 4 –N 2 -rich, primordial mantle fluid, but have been progressively diluted with H 2 O and become oxidized by repeated subduction of oceanic slab. We propose that repeated redox melting in the mantle due to dilution of CH 4 with H 2 O and oxidation caused formation of the long-lived Palaeo-Asian Ocean, brought about extensive intrusion of mafic–ultramafic complexes and alkaline–peralkaline granites right through the post-collisional period, and, consequently, resulted in significant Phanerozoic continental growth in the Central Asian Orogenic Belt. Rise of atmospheric O 2 and the Earth's major oxidation occurred at about 2.4 to 2.2 Ga. Oxidation of the Earth's mantle promoted the mantle melting and magma input to the crust, resulting in major continental growth after 2.5 Ga. However, much-postponed oxidation of the primordial mantle underneath the Central Asian Orogenic Belt led to significant continental growth in the Phanerozoic times.

The Influence of Synoptic-scale Air Flow and Local Circulation on the Dust Layer Height in the North of the Taklimakan Desert

The present study investigates the influences of synoptic-scale air flows and local wind circulations on the dust layer height (DLH) in the Taklimakan Desert, based on lidar observations performed in the north of the desert in March 2003. The DLH fluctuates approximately every three days between 2500 m (above sea level) and 5000 m, including diurnal variations. Meteorological analyses and numerical simulations show that the three-day fluctuation of DLH corresponds with variations in synoptic-scale air flows over the Taklimakan Desert, and the diurnal variations are linked to downdrafts and updrafts that are formed over the north of the desert as part of local circulations. When strong northerly winds prevail in the upper troposphere and a developed valley wind blows toward the Tienshan Mountains in the lower troposphere, the downdrafts strengthen in the middle troposphere over the north of the desert, lowering the DLH to about 2500 m. In contrast, the DLH rises to about 5000 m when the updrafts develop between strong southerly winds in the upper troposphere and a developed mountain wind blowing from the Tienshan Mountains. Simulations for the local circulation behavior without the presence of the Tienshan Mountains demonstrate that the valley and mountain winds on the southern slope of the Tienshan Mountains control the intensity of the downdrafts and updrafts, thereby influencing the DLH over the north of the Taklimakan Desert.

Collapse process of rock glacier in the head water area of Urumqi River, Tienshan Mountains in China

Collapse process of rock glacier in the head water area of Urumqi River, Tienshan Mountains in China

Volumetric velocities of the periglacial rubble slope in 44 years, Tienshan Mountains in China

Volumetric velocities of the periglacial rubble slope in 44 years, Tienshan Mountains in China

Observed Dust Storm in the Taklimakan Desert on April 13, 2002

Analysis results of data from lidar and AWS observations performed in the northwestern part of the Taklimakan Desert show a sudden increase in the backscattering ratios in the lower troposphere on 13 April 2002, with strong easterly winds. The Terra satellite reveals that the sudden increase is caused by the outbreak of an extensive dust storm. Numerical simulations, using a regional model, reproduce the strong easterly winds prevailing in a wide area of the desert, originating from north of the Tienshan Mountains. These conclude that the strong easterly winds lift a large amount of sand particles off the ground and results in the dust storm. In addition, a nose-shaped profile of the increased backscattering ratios indicates passage of a gravity current.

Development of the periglacial rubble slope in the head water area of Urumqi River, Tienshan Mountains in China

Development of the periglacial rubble slope in the head water area of Urumqi River, Tienshan Mountains in China

Twenty Years Morphological Changes of Number Six Glacier, Urmuqi River, the Tienshan Mountains

Twenty Years Morphological Changes of Number Six Glacier, Urmuqi River, the Tienshan Mountains

Wurpte Glacier in the Tienshan Mountains

Wurpte Glacier in the Tienshan Mountains

Early Carboniferous athyridid brachiopods from the Qaidam Basin, northwest China

Four new Early Carboniferous athyridid species in three genera, including one new genus,Bruntonathyris, are described from the Qaidam Basin, northwest China:Lamellosathyris qaidamensis, Bruntonathyris amunikeensis, Bruntonathyris?heijianshanensis, andLochengia qinghaiensis. Based on the new material and also on published information, we also reviewed the taxonomic composition and the stratigraphic and paleogeographic distributions of the three genera. As a result,Lamellosathyrisis considered to be indicative of late Famennian to Viséan age, originating in late Famennian in central North America and Armenia of Russia, respectively. Later, the genus appears to have two migratory directions: one branch rapidly dispersed over Mississippi Valley, Oklahoma, Texas and New Mexico of central North America in Tournaisian; alternatively, another branch from Armenia migrated westerly to Belgium, France, Spain, Britain, Ireland, via the Moscow Basin and Ural seaway, eastward to the Tienshan Mountains and Qaidam Basin of northwest China during the Tournaisian to Viséan, and easterly along the southern shelves of the Paleo-Tethys to Iran and western Yunnan of southwestern China in Tournaisian. BothBruntonathyrisandLochengiaare restrictedly Tournaisian to Viséan in age, and probably originated in the Qaidam Basin. Later,Bruntonathyrismigrated easterly to South China and Japan, and westerly to Urals, Moscow Basin, Donetsk Basin and Britain;Lochengiamigrated easterly to South China and westerly to the Urals seaway and the adjoined Russian Platform (i.e., both the Moscow and Donetsk Basins).

FACIES CONTROL ON THE COMPOSITION OF SERPUKHOVIAN AND EARLY BASHKIRIAN FORAMINIFERAL ASSEMBLAGES IN THE MIDDLETIEN-SHAN MOUNTAINS, CENTRAL ASIA

Serpukhovian-lower Bashkirian deposits are widely developed in the Middle Tien-Shan Mountains of Uzbekistan and adjacent countries of Central Asia. These deposits formed in a sedimentary basin exhibiting four distinctive facies that differ in foraminiferal diversity and population density. The facies types, named for mountain ranges containing representative sections, are called 1) Talassic, for inner shelf, shallow- water marine carbonates; 2) Ugamic, for carbonaceous deposits accumulating on an open, shallow-water, outer carbonate shelf platform; 3) Karzhantauic, for interbedded volcaniclastics and shallow-water marine carbonates deposited on a eroded surface; and 4) Paltauic, for basinal beds containing thin-bedded, graded and laminated organic limestones and interbedded turbidites. A statistical program (Sorenson's Coefficients of Species Similarity) was used to compare assemblages in eight foraminiferal zones from coeval fades across the basin. Highest similarity coefficients occur in the early Serpukhovian and are probably related to a marine transgression that flooded the basin. Regression and volcaniclastic sedimentation account for lower coefficients in the remainder of the Serpukhovian. Increased foraminiferal diversity and abundance in the earliest Bashkirian were probably caused by the opening of new connections to adjacent Paleotethyan basins only to be followed by more restricted environmental conditions and lower similarity coefficients later in the early Bashkirian.

EARLY CARBONIFEROUS ATHYRIDID BRACHIOPODS FROM THE QAIDAM BASIN, NORTHWEST CHINA

Four new Early Carboniferous athyridid species in three genera, including one new genus, Bruntonathyris, are described from the Qaidam Basin, northwest China: Lamellosathyris qaidamensis, Bruntonathyris amunikeensis, Bruntonathyris? heijianshanensis, and Lochengia qinghaiensis. Based on the new material and also on published information, we also reviewed the taxonomic composition and the stratigraphic and paleogeographic distributions of the three genera. As a result, Lamellosathyris is considered to be indicative of late Famennian to Viséan age, originating in late Famennian in central North America and Armenia of Russia, respectively. Later, the genus appears to have two migratory directions: one branch rapidly dispersed over Mississippi Valley, Oklahoma, Texas and New Mexico of central North America in Tournaisian; alternatively, another branch from Armenia migrated westerly to Belgium, France, Spain, Britain, Ireland, via the Moscow Basin and Ural seaway, eastward to the Tienshan Mountains and Qaidam Basin of northwest China during the Tournaisian to Viséan, and easterly along the southern shelves of the Paleo-Tethys to Iran and western Yunnan of southwestern China in Tournaisian. Both Bruntonathyris and Lochengia are restrictedly Tournaisian to Viséan in age, and probably originated in the Qaidam Basin. Later, Bruntonathyris migrated easterly to South China and Japan, and westerly to Urals, Moscow Basin, Donetsk Basin and Britain; Lochengia migrated easterly to South China and westerly to the Urals seaway and the adjoined Russian Platform (i.e., both the Moscow and Donetsk Basins).

THE CRYSTAL STRUCTURE OF MOSKVINITE-(Y), Na2 K (Y,REE) [Si6O15], A NEW SILICATE MINERAL WITH [Si6O15] THREE-MEMBERED DOUBLE RINGS FROM THE DARA-I-PIOZ MORAINE, TIEN-SHAN MOUNTAINS, TAJIKISTAN

The crystal structure of moskvinite-(Y), ideally Na 2 K (Y, REE ) [Si 6 O 15 ], from the moraine of the Dara-i-Pioz glacier, the Alai mountain range, Tien-Shan mountains, northern Tajikistan, a 10.623(2), b 14.970(2), c 8.553(1) A, V 1359.8(4) A 3 , space group Ibmm , Z = 4, D (calc.) = 2.850 g.cm −3 , has been solved by direct methods and refined to an R 1 index of 1.7% based on 936 observed [| F o | > 4σ F ] unique reflections collected with single-crystal diffractometer with Mo K α X-radiation. Electron-microprobe analysis gave the composition Na 2.06 K 0.95 (Y 0.77 Dy 0.09 Gd 0.04 Er 0.04 Ho 0.02 Sm 0.02 Nd 0.01 Tb 0.01 ) ∑1.00 Si 6 O 15 based on 15 O apfu . In the crystal structure of Na 2 K (Y, REE ) [Si 6 O 15 ], there are two tetrahedrally coordinated T sites occupied by Si with Si –O> = 1.623 A. The (SiO 4 ) tetrahedra form three-membered rings, [Si 3 O 9 ], that link by sharing apical vertices to form a doublering of the form [Si 6 O 15 ]. There are two [6]-coordinated sites, one occupied by (Y 0.77 + REE 0.23 ) with REE )–O> = 2.255 A, and the other occupied by Na with Na –O> = 2.438 A. There is a [10]-coordinated site occupied by K with K –O> = 3.062 A. The {(Y, REE )O 6 } and (NaO 6 ) octahedra share common edges to form sheets parallel to (010); these sheets connect through [Si 6 O 15 ] double-rings to form a framework. Channels extend along [001] and contain K. The topology of the Na 2 K Y [Si 6 O 15 ] framework is identical to that of synthetic Na 3 Y [Si 6 O 15 ], but the arrangement of the channel cations is different. The crystal structures of double-ring silicates and [Si 6 O 18 ]-chain structures are discussed.

Effective growth of a number of cosmic ray electrons inside thundercloud

Significant enhancement of secondary cosmic ray electrons inside electrically charged clouds is established. The effect is observed in a quiet phase of thunderstorm—in the absence of lightning, rainfall and bursts of X-ray emission. The observations are fulfilled in Tien-Shan Mountains at the modernized thunderstorm–cosmic ray (TCR) installation [Phys. Lett. A 275 (2002) 90; J. Phys. G 28 (2) (2002) 251].

Initiation of earthquake-induced slope failure: influence of topographical and other site specific amplification effects

Increased structural damage caused byearthquakes on hilltops and along ridgeshas often been related to amplification ofground motion due to the presence oftopography. However, comparison betweenobservations and numerical modeling hasshown that amplification is only partlydependent on the prominent surfacemorphology. Strong effects are also inducedby soft layers, such as weathered rockmaterial or colluvium, covering thetopographies.Numerous seismically triggered landslidesare reported to occur in the same materialsthat are likely to amplify ground motions.Therefore, it can be suspected that groundmotion dynamics significantly contribute tothe observed slopes failures. Thispotential relationship is the subject ofthe present case study, the Ananevorockslide in the northeastern Tien Shanmountains. The survey included geophysicalprospecting, earthquake recordings andstructural analyses of the rock fabric. Onthe basis of the field data, observedamplification effects could be related tothe local geological conditions andparticularly to the surface morphology andto the presence of low-velocity layers –deeply weathered rocks – on the top of thebedrock. Surface layer- andtopography-dependent amplification has alsobeen studied numerically by 2D and 3Dfinite element modeling of ground motiondynamics. The present paper focuses onadditional effects that may be induced bythe presence of a fault zone and of thelandslide scarp. Further, observed andcomputed ground motion dynamics areconnected with slope failuresusceptibility: 2D numerical simulationsreveal that strain localization is closelyrelated to wave amplification in surficiallow-velocity layers, particularly belowconvex surface morphologies.

Human-Induced Changes to Biodiversity and Alpine Pastureland in the Bayanbulak Region of the East Tienshan Mountains

The Bayanbulak region, deep in the East Tienshan Mountains, is the southernmost and highest breeding area for swans anywhere in the world. As one of the few biodiversity hotspots in central Asia, it was listed in 1986 as a Chinese national swan nature reserve. The region is also the largest grazing area in Xinjiang as well as a tourist attraction. But in the last 25 years, the population of wild swans has decreased from about 20,000 to 2000, and approximately half of the pastureland now suffers from overgrazing and degradation. Moreover, the local government has been considering building a reservoir in the region. If this is done, the ecology of this region would be greatly altered, and almost all wild-swan habitats would disappear. The present study identifies alpine grassland types and concludes that it is urgent to protect the breeding areas of wild swans and control grassland degradation, and that any plan for reservoir construction should be rejected.

Some results of snow chemical surveys in the Kunnes River valley, East Tienshan mountains, China

Chemical surveys of snow were carried out in the upper reaches of the Kunnes River, a tributary of the Yili River in East Tienshan Mountains, China. Some surprisingly high values of sodium and potassium (K ++Na +) ranging from 4.44 to 8.99 mg/l compared with other data from neighboring areas are detected. Moreover, some relative high values of SO 4 2− with mean concentration 15.8 mg/l for new snow and 14.40 mg/l for deposited snow, ranging from 10.43 to 23.71 mg/l are also found. Therefore, it is inferred that the sodium and potassium (K ++Na +) are in the forms of sulfate and that the sources of the sulfate are deserts and some dried lakes in Central Asia. It is also found that there is obviously spatial variation of ions such as K ++Na +, Ca 2+, SO 4 2− and HCO 3 −. The concentrations of K ++Na + and SO 4 2−, and that of Ca 2+ and HCO 3 − have similar spatial pattern. The temporal pattern of ion concentration of new snow is considered to be mainly controlled by the depth and area of snow cover in the study area and in the areas to the west.

Tournaisian-Visean brachiopods from the Gancaohu area of Southern Tienshan Mountains, Xinjiang, NW China

A brachiopod fauna spanning the Tournaisian-Visean boundary is reported from the Southern Tienshan Mountains of Xinjiang, NW China. This fauna exhibits strong generic and specific links with coeval North American faunas. The present fauna is of close affinity with those of the northern Tienshan and Junggar Basin rather than that of the Tarim Basin. Biogeographically, the southern and northern Tienshan areas belong to the Tienshan-Hinggan Province of the Boreal Realm during the Tournaisian and Visean, while the adjacent Tarim Basin belongs to the Tethyan Province of the Tethyan Realm, which differs from the conclusions of previous studies. Two now species are proposed: Spirifer (Spirifer) gancaohuensis and Kitakamithyris karatagensis.

Ants from Northwestern China (Hymenoptera, Fomficidae)

An ecological survey of the ant fauna of the southern part of the Junggar Basin and adjacent mountains, Xinjiang, China, revealed 46 species of which 27 (59%) were new records for China. Most of the species are widespread and no endemics were found. A largely boreal fauna occupies the spruce forest zone at high elevations of the Tienshan Mountains, giving way, lower down, in elm forest, to a mixed, but primarily mesic temperate fauna. Loess desert and degraded steppe at mid-elevations and in the foothills are overgrazed and have only a few species that elsewhere occur in temperate mesic and/or steppic habitats. The sandy deserts and poplar woodlands of the arid Junggar Basin have a fauna characteristic of deserts and steppes. The salt desert fauna has a strange mixture of a number of elements.

Ultra-high pressure eclogites of the Makbal district, northern Tien-Shan Mountains, Kyrghyzstan

Ultra-high pressure eclogites of the Makbal district, northern Tien-Shan Mountains, Kyrghyzstan

Carotenoids in certain lichens from Pamir-Alai and Tien-Shan Mountains

Carotenoids in certain lichens from Pamir-Alai and Tien-Shan Mountains