Loess of Central Asia

Loess deposits are widespread within the piedmont and intramontane depressions of Central Asia. They cover piedmont plains, river terraces, ridge slopes and watersheds. Loess is a significant component in the piedmonts of Tien Shan, eastern Fergana depression, the Afgan-Tajik depression, piedmonts of Kopetdag, Badchyz and Karabil Hills north of Parapamiz, in the Kashmir valley, on the Potwar Plateau and in the Peshawar Basin.     

Surface deformations in Central Asia

Measurement of surface deformations caused by drift of the Indian tectonic plate against the Eurasian plate has been performed with short-range EDM-instruments in U.S.S.R. Central Asia. A relative motion of 1.5 cm/yr has been found. It has been shown that uncertainty in the refraction model used in derivation of the motion vectors plays a great role in determination of the short-period motion results.     

Active Tectonics of Central Asia

Geotectonics - Central Asia exceeds neighboring territories in the intensity of Quaternary uplifts and active faulting. The active fault kinematics differ in the northeast of the region, from...     

Sedimentogenesis in the Mesozoic-Cenozoic continental rifts of Central Asia

An analysis of continental sedimentogenesis in Mesozoic rifts of the Transbaikal region and Mongolia, as well as in the Cenozoic Baikal rift zone, revealed a succession of volcanic-sedimentary formations, which constitute the sedimentary cover. The peculiar sedimentation features reflect exogenic processes that are characteristic of rift structures and the influence of deep-seated (exogenic and catagenic) sources. It is proposed to define a specific, rift, type of sedimentogenesis.     

Neotectonics and the Upper Mantle Structure of Central Asia

Geotectonics - Studies carried out by the authors show that the uplift of Central Asia situated between the eastern Alpine–Himalayan and western Altai–Stanovoy orogenic belts formed in...     

Preliminary Studies of Speleothem in Central Asia

正Objective The Westerlies is important in linking the Northern high latitude,North Atlantic and East Asian monsoon.The location and intensity of the Westerly jet can not only control the climate of central Asia(including northwest arid China),but also significantly influence the climate of the East Asian monsoon region.However,it remains     

中亚地区中、南天山造山带构造演化及成矿背景分析

横贯中亚地区的中、南天山造山带,在元古宙末罗迪尼亚超大陆裂解时,先后以中天山南缘断裂为主线分裂出被洋区围限的众多大小不一的地块群。斜贯全区的塔拉斯-费尔干纳断裂,在古生代演化过程中具有转换断层性质,明显控制了南天山东西两侧的构造演化及成矿过程的差异性发展。中天山微板块北缘发育寒武纪-奥陶纪古洋盆,其南缘西段由寒武纪到中泥盆世经历两次扩张,形成多岛洋的构造格局,其中志留纪洋区被动陆缘上的碳硅质砂页岩建造成为金矿床的最佳赋存层位;东段洋区从震旦纪开始扩张,直到晚泥盆世闭合,晚石炭世南天山东西两侧在造山构造极性上发生西段由南向北、而东段由北向南呈相反方向逆掩推覆的造山过程,同时伴有碰撞型花岗岩浆活动,形成了钨、锡、铌-钽、钼、铜、铅锌等多金属矿床。晚二叠世-三叠纪塔拉斯-费尔干纳断裂以右旋走滑运动为特征,伴随有后碰撞型花岗岩浆活动,从而为汞锑成矿带的生成奠定了基础。侏罗纪塔拉斯-费尔干纳断裂进入走滑拉分期。新生代印度板块向北推挤,致使南天山发生挤压缩短而强烈抬升隆起。     

The origin of silt particles in the loess question

Many researchers consider loess as solely the product of glacial activity. Investigations throughout South America, however, have demonstrated that loess and loess-like sediments can be formed during geological periods when glaciation was absent. Loess deposits may be derived from volcanic action, from weathering processes, and as a result of pedogenic activity. Production of silt, regardless of the geologic process, can result in loess formation under suitable climatic conditions.     

P-wave tomography and origin of the Changbai intraplate volcano in Northeast Asia

We present the first seismic image of the upper mantle beneath the active intraplate Changbai volcano in Northeast Asia determined by teleseismic travel time tomography. The data are measured at a new seismic network consisting of 19 portable stations and 3 permanent stations. Our results show a columnar low-velocity anomaly extending to 400-km depth with a P-wave velocity reduction of up to 3%. High velocity anomalies are visible in the mantle transition zone, and deep-focus earthquakes occur at depths of 500–600 km under the region, suggesting that the subducting Pacific slab is stagnant in the transition zone, as imaged clearly by global tomography. These results suggest that the intraplate Changbai volcano is not a hotspot like Hawaii but a kind of back-arc volcano related to the deep subduction and stagnancy of the Pacific slab under Northeast Asia.     

Paleozoic Tectono-Metallogeny in the Tianshan-Altay Region, Central Asia

The research on Paleozoic tectonics and endogenic metallogeny in the Tianshan-Altay region of Central Asia is an important and significant project. The Altay region, as a collision zone of the Early Paleozoic (500–397 Ma), and the Tianshan region, as a collision zone of the early period in the Late Paleozoic (Late Devonian-Early Carboniferous, 385–323 Ma), are all the result of nearly N-S trending shortening and collision (according to recent magnetic orientation). In the Late Devonian-Early Carboniferous period (385–323 Ma), regional NW trending faults displayed features of dextral strike-slip motion in the Altay and Junggar regions. In the Tianshan region, nearly EW-trending regional faults are motions of the thrusts. However, in the Late Carboniferous-Early Permian period (323–260 Ma), influenced by the long-distance effect induced from the Ural collision zone, those areas suffered weaker eastward compression, the existing NW trending faults converted into sinistral strike-slip in the Altay and Junggar regions, and the existing nearly E-W trending faults transferred into dextral strike-slip faults in the Tianshan region. The Rocks of those regions in the Late Carboniferous-Early Permian period (323–260 Ma) were moderately ruptured to a certain tension-shear, and thus formed a number of world famous giant endogenic metal ore deposits in the Tianshan-Altay region. As to the Central Asian continent, the most powerful collision period may not coincide with the most favorable endogenic metallogenic period. It should be treated to “the orogenic metallogeny hypothesis” with caution in that region.     

Paleozoic Tectono-Metallogeny in the Tianshan-Altay Region, Central Asia

The research on Paleozoic tectonics and endogenic metallogeny in the Tianshan-Altay region of Central Asia is an important and significant project. The Altay region, as a collision zone of the Early Paleozoic(500–397 Ma), and the Tianshan region, as a collision zone of the early period in the Late Paleozoic(Late Devonian-Early Carboniferous, 385–323 Ma), are all the result of nearly N-S trending shortening and collision(according to recent magnetic orientation). In the Late Devonian-Early Carboniferous period(385–323 Ma), regional NW trending faults displayed features of dextral strike-slip motion in the Altay and Junggar regions. In the Tianshan region, nearly EW-trending regional faults are motions of the thrusts. However, in the Late Carboniferous-Early Permian period(323–260 Ma), influenced by the long-distance effect induced from the Ural collision zone, those areas suffered weaker eastward compression, the existing NW trending faults converted into sinistral strike-slip in the Altay and Junggar regions, and the existing nearly E-W trending faults transferred into dextral strike-slip faults in the Tianshan region. The Rocks of those regions in the Late Carboniferous-Early Permian period(323–260 Ma) were moderately ruptured to a certain tension-shear, and thus formed a number of world famous giant endogenic metal ore deposits in the Tianshan-Altay region. As to the Central Asian continent, the most powerful collision period may not coincide with the most favorable endogenic metallogenic period. It should be treated to "the orogenic metallogeny hypothesis" with caution in that region.     

Geodynamics and seismicity of the eastern part of Central Asia

Study of the geodynamics of the eastern part of Central Asia shows that the present-day tectonic activity of this territory is connected with its division into blocks limited by active faults and with the interaction among these blocks and with the neighboring lithospheric plates. The North China and South China platforms occupy most of this territory. The western boundary of the South China platform with Tibetan blocks is the most active. The energy volume increases up to 10¹⁰–10¹² J, and the earthquake magnitudes go up to 8–9 within this boundary. The interaction of Tibetan blocks with the Southeast China Block causes detachment and a clockwise turn of the upper layers of the Earth’s crust under the influence of the Hindustan indenter pressure.

     

中亚天山冰川资源及其分布特征

中亚天山分布有冰川１５９５３条，面积１５４１６．４ｋｍ＾２，估计冰储量１０４８．２４７ｋｍ＾３。冰川以高大山峰为中心呈辐射状分布为其主要类型。冰川在各大山区和各大水系中，分别以中央天山和塔里木盆地水系为最多，纬向对冰川发育和雪线高度的影响大于经向的影响。     

Late Cambrian-Ordovician tectonics and geodynamics of Central Asia

In the Late Cambrian-Ordovician, Gondwana-derived microcontinents such as Kokchetav, Altai-Mongolian, Tuva-Mongolian, and Barguzin, as well as the Kazakhstan-Tuva-Mongolian island arc or a system of island arcs were involved in intense accretion-collision processes in similar geodynamic settings on a vast territory of Central Asia — from West Kazakhstan to Lake Baikal. The processes were likely to be the result of a large rebuilding of the Earth’s crust possibly related to the increased mantle impact on the lithosphere as they were simultaneous to the opening of the Uralian and Mongolian-Okhotsk (Turkestan) Oceans. The 970–850 Ma breakup of Rodinia and the 760–700 Ma important tectonic events were followed by the Late Cambrian-Early Ordovician plume magmatism impulse at 500–480 Ma, which led to the opening of new oceans and accelerated the accretion of the Gondwana-derived blocks to the island arc and subsequent formation of an extended — more than 6000 km long — Kazakhstan-Baikal orogenic belt.     

Late Cenozoic volcanic province in Central and East Asia

The paper presents materials on the inner structure of the Late Cenozoic within-plate volcanic province in Central and East Asia, in which two subprovinces are distinguished: Central Asian and Far Eastern, which comprise a number of autonomously evolving volcanic areas. Some of the volcanic areas are proved to have evolved for a long time, starting in the Late Mesozoic. In spite of differences in their age and structural setting, the volcanic areas evolved according to similar scenarios in the Late Cenozoic. Magmatism in the province was related to a mantle source of the within-plate type. The magmatic associations are dominated by mafic alkaline high-K rocks. The rocks are geochemically close to basalts of the OIB type, and their isotopic composition corresponds to a combination of mantle sources of the PREMA, EMI, and EMII types at the predominance of PREMA. Geological, geochemical, and isotopic lines of evidence suggest that magmatism in the province was related to mantle plumes. This is consistent with geophysical data, which testify that the volcanic areas are underlain by upwellings of the asthenospheric mantle or plumes. Seismic tomography data indicate that the “stems” of the plumes can be traced down to the upper and lower mantle. The province is thought to have been produced when the eastern margin of the Asian plate overlapped one of the branches of the Pacific superplume at approximately 160 Ma. This branch of the superplume is pronounced in the modern mantle structure as a cluster of mantle plumes that control (according to seismic tomography data) the interaction zone of the Pacific and Asian lithospheric plates.     

中亚地区干旱变化及其影响分析

全球变暖加剧了中亚地区的干旱威胁,使得因干旱引发的水资源短缺、生态退化及跨境河流争端等问题更加突出。研究显示：过去半个多世纪,基于帕默尔干旱指数表征的中亚地区干旱程度整体变化趋势不显著,但伴随着区域的高温波动,中亚地区帕默尔干旱指数自2000年以来呈现明显下降趋势,约65%的区域表现为干旱化程度加剧,且在未来共享社会经济路径下中亚地区干旱强度持续增强。设计“去趋势”数字试验定量解析干旱指标对气候变化中各项因子的敏感性,发现气温对中亚干旱化趋势影响较大,降水变化加大了干旱的变率。从不同干旱亚类来看,中亚地区极端干旱区和干旱区面积以0.02×10⁴和0.22×10⁴km²/a的速率增加,主要集中在新疆塔里木盆地北缘和哈萨克斯坦南部等地区。同时,平原荒漠区的植被蒸腾和土壤水耗散量加大,浅层土壤含水量（0～10和10～40 cm）分别约有84%和81%的区域表现为下降趋势,导致一些依靠地下水和土壤水维系生存的、抗旱性弱的浅根系荒漠植物衰亡,生态农业干旱加剧,且水文干旱呈更加复杂的态势,研究结论为中亚地区水资源规划管理和生态保护提...     

Seismic structure and origin of active intraplate volcanoes in Northeast Asia

Three-dimensional P-wave velocity structure beneath the Changbai and other intraplate volcanic areas in Northeast Asia is determined by inverting 1378 high-quality P-wave arrival times from 186 teleseismic events recorded by 61 broadband seismic stations. Low-velocity (low-V) anomalies are revealed beneath the Changbai, Longgan, Xianjindao volcanoes. High-velocity (high-V) anomalies are found in the mantle transition zone, where deep-focus earthquakes under Hunchun occur at depths of 500–600 km. The high-V anomaly reflects the deep subduction of the Pacific slab under NE Asia which may have contributed to the formation of the Changbai, Longgang, Xianjindao and Jingpohu intraplate volcanoes. A low-V anomaly is also revealed in the mantle transition zone, which may have a close relationship with the occurrence of deep earthquakes under the Hunchun area. Our results support the Big Mantle Wedge (BMW) model by Zhao et al. [Zhao, D., Lei, J., Tang, Y., 2004. Origin of the Changbai volcano in northeast China: evidence from seismic tomography, Chin. Sci. Bull. 49, 1401–1408; Zhao, D., Maruyama, S., Omori, S., 2007. Mantle dynamics of western Pacific and East Asia: insight from seismic tomography and mineral physics. Gondwana Res. 11, 120–131.] who proposed that the intraplate volcanoes in NE Asia are caused by the back-arc magmatism associated with the deep dehydration process of the subducting slab and convective circulation process in the BMW above the stagnant Pacific slab.