THE CHARACTERISTICS OF TECTONIC FACIES IN THE WESTERN TIANSHAN MT. AND ITS ADJACENT AREA,NORTHWESTERN CHINA

Based on the theory of plate tectonics, the authors combined the concept and analytic methods of tectonic facies, and divided the western Tianshan Mt. and its adjacent area into eight tectonic facies. i. e.① Kuluktage rejuvenational foreland basement fold-thrust facie, ②Kalpin rejuvenational foreland basement fold-thrust facie,③ Kuqa rejuvenational foreland fold-thrust facie. ④ Southern Tianshan backarc foreland mollasse facie. ⑤ Southern Tianshan Late Paleozoic magmatic arc facie. ⑥ Southern Tianshan backarc melange facie. ⑦ Central Tianshan composite magmatic are facie, and ⑧ Northern Tianshan foreare melange facie. F1nally. we reconstructed the history of the western Tianshan Paleozoic tectonic evolution.

Soft-sediment Deformation Structures Related to Earthquake from the Devonian of the Eastern North Qilian Mts.and Its Tectonic Significance

Devonian in the North Qilian orogenic belt and Hexi Corridor developed terrestrial molasse of later stage of foreland basin caused by collision between the North China plate and Qaidam microplate. The foreland basin triggered a intense earthquake, and formed seismites and earthquake-related soft-sediment deformation. The soft-sediment deformation structures of Devonian in the eastern North Qilian Mts. consist of seismo-cracks, sandstone dykes, syn-depositional faults, microfoids （micro-corrugated lamination）, fluidized veins, load casts, flame structures, pillow structures and brecciation. The seismo-cracks, syn-depositional faults and microfolds are cracks, faults and folds formed directly by oscillation of earthquake. The seismic dykes formed by sediment instilling into seismic cracks. Fluidized veins were made by instilling into the seismo-fissures of the fluidized sands. The load casts, flame structures and pillow structures were formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The brecciation resulted from the oscillation of earthquake and cracking of sedimentary layers. The seismites and soft-sediment deformations in Devonian triggered the earthquake related to tectonic activities during the orogeny and uplift of North Qilian Mts.

FROM BACK-ARC BASIN TO BACK-ARC FORELAND BASIN—THE SEDIMENTARY BASIN AND TECTONIC EVOLUTION OF THE LATE CALEDONIAN—EARLY HERCYNIAN STAGES IN CORRIDOR AND NORTH QILIAN MTS

Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.

Age and Provenance of Loess deposits on the Northern Flank of Tianshan Mountain

The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73 Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05 Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.

Climate Change and Its Effects on Runoff in the North of Tianshan,Xinjiang

[Objective] The aim was to study climate changes in northern Tianshan in Xinjiang and its influences on runoff. [Methed] Based on the runoff data for 54 years of Kenswatt station on Manas River and the climate date of 16 meteorological stations from 1957 to 2007 in the north of Tian- shan in Xinjiang, the climate change and temporal series of the annual runoff were studied by use of nonparametric test, wavelet analysis, R/S analysis and periodic trend superposition model. [ Result] The temperature, precipitation and annual runoff of Manas River increased significantly. The Hurst coefficients of both climate factors and the annual runoff were bigger than 0.5, which indicated that they would still keep an increasing trend. Temperature from 1957 to 1959 was low, precipitation was much, belonging to low temperature and more rain period. 1960s and 1970s were low temperature and less rain period. Temperature in 1980s was close to average value and precipitation was little. Since 1990s, it entered into high temperature and less rain period and was significant during 2000 and 2007. The temperature and precipitation changed in 1995 and 1996. Tempera- ture was＇significant in 11 and 22 years. Precipitation had 5, 8, 14 and 22 years of main cycle. The annual runoff and climate factors in Manasi River were increasing in different times. The annual runoff was related to climate factors, and temperature was closer to annual runoff than precipitation. [ Conclusion] The study provided theoretical basis for the reasonable configuration, ecological protection and agricultural production of water re- sources in north Tianshan in Xinjiang.

Study on the Source Parameters of Earthquakes in the Middle Eastern Area of North Tianshan in Xinjiang

By applying the empirical Green＇s function method, we first proved that the source spectra in the middle eastern area of North Tianshan follow the ω^-2 Brune model, and then, on this basis, obtained the source spectra for 105 earthquakes of ML 2.5 - 5.7 in the studied area upon removing the noise, instrument, propagation and site effects in the observational seismic S waveforms. Finally, we determined the source parameters such as the seismic moment, stress drop, source dimension, etc., based on the Brune model. The results show that there is a good linear correlation between scalar seismic moment, M0, and ML, which is Log10 M0 = 1.10 ML ＋ 17.20; The source radii range between 100- 1500m; the stress drop, 1-16MPa with a predominant range of 1 - 10MPa. The relationship of the seismic moment versus corner frequencies indicates that there may exist two source scaling, that is, when M0 〈 4×10^21 dyne. cm （equal to an ML4.0 event）, stress drop is weakly dependent on M0： whereas, when M0 〉 4×10^21 dyne·cm, stress drop is independent of M0.

Early Cretaceous Thrust and Nappe Tectonics in North Qilian Shan,Northern Tibetan Plateau:Evidence from Field Mapping,Geochronology,and Deep Structural Analysis

The North Qilian Shan fold and thrust belt,located at the northern Tibetan Plateau and southern margin of the Hexi Corridor,is a key tectonic unit to decode the formation and expansion of the plateau.Previous studies emphasize the Cenozoic deformation due to the far-field response to the Indo-Asian collision,but the Mesozoic deformations are poorly constrained in this area.We conducted detailed field mapping,structural analysis,geochronology,and structural interpretation of deep seismic reflectional profiling and magnetotelluric(MT)sounding,to address the superposed results of the Mesozoic and Cenozoic deformation.The results recognized the North Qilian thrust and nappe system(NQTS),the root and the frontal belt are the North Qilian thrust(NQT),and the Yumu Shan klippe(YK),respectively.The middle belt is located between the NQT and the YK.Monzonitic granite zircon U-Pb dating from the middle belt yields an age of ca.415 Ma,which is similar to south NQT.The thrusting displacement is estimated at ca.48 km by structural interpretation of deep profiles.The timing is constrained in the early stage of the Early Cretaceous by the formation of simultaneous growth strata.We suggest that the NQTS has resulted from the far-field effect of the Lhasa-Qiangtang collision,and the Yumu Shan is uplifted by the superposed Cenozoic deformation.

Analysis on Variations of the Temperature and Precipitation in North Slope Area of the Western Tianshan in Recent 50 Years

[Objective] The research aimed to analyze variation characteristics of the temperature and precipitation in north slope area of the Western Tianshan in recent 50 years.[Method] According to temperature and rainfall data from 1961 to 2010 at three meteorological stations in north slope area of the Western Tianshan,climate change in the zone in recent 50 years was analyzed by using linear trend analysis method and 5-year sliding average method.[Result] The temperature in north slope area of the Western Tianshan showed significant warming trend.The annual average temperature significantly increased at 0.3 ℃/10 a in recent 50 years.But rise rates of the temperature in different seasons were different:autumn> winter> spring> summer.The annual rainfall in north slope area of the Western Tianshan in recent 50 years overall presented relative increase trend.Seen from annual rainfall,it significantly increased at 16.9 mm/10 a.Seen from seasonal rainfall,except in autumn,rainfalls in other three seasons in the past 50 years all showed significant increase trends,with amplitude of 3.2-11.2 mm/10 a.The largest increase amplitude was in summer.After a small precipitation peak in the 1980s,autumn rainfall slightly declined in the past 20 years.[Conclusion] The climate in north slope area of the Western Tianshan become warm and wet.

Subsurface Facies Analysis of the Late Cambrian Mt. Simon Sandstone in Western Ohio (Midcontinent North America)

The Cambrian Mt. Simon Sandstone (MSS) is a possible unconventional gas reservoir in the Illinois, Michigan, and Appalachian Basins, but comparatively little is known about the unit. This study used core and well logs from two deep exploratory wells to interpret the depositional environment of the MSS under western Ohio, where the MSS is about 120 m thick and found 1060 m below ground surface. In western Ohio, the MSS unconformably overlies the Precambrian Middle Run Formation, is conformably overlain by the Cambrian Eau Claire Formation, and has a distinctive gamma-ray log-signature. In well DGS-2627, the MSS consists of tan, friable, moderately sorted, rounded, coarse- to very coarse-grained siliceous quartz arenite with minor heterolithic sandstone-mudstone couplets (rhythmites) and quartz granule conglomerate. Features indicative of tidally-influenced, shallow marine settings include tidal rhythmites, lenticular-, flaser-, and wavy-bedding, herringbone cross-bedding, mud-drapes, tidal bundles, reactivation surfaces, intraclasts, and bioturbation. The unit generally coarsens- and thickens-upward, and is interpreted as migration of a tidally-influenced transgressive barrier sequence. A subsurface facies model for the MSS is developed by interpreting geophysical logs and cores from DGS-2627l, and this model is semi-quantitatively tested by first interpreting well BP-4 using geophysical logs alone, then confirming the results using core.

OXIDES AND TRACE ELEMENTS OF THE CARBONIFEROUS CARBONATE ROCK IN TIANSHAN MT.,CHINA

The Carboniferous carbonate rock with complicated composition and various rock types and lithofacies develops well in Tianshan Mt. , China, and plays an important role in the study of tectonics and metallogeny in the area. The content and variation characteristics of main pxides and elements are illustrated here based on a great amount of geochemical data.

A Report of the Newly Discovered Cu–Ni Ore Deposit in the West of East Tianshan, North Xinjiang, China

Objective The Early Permian mafic-ultramafic intrusions （298- 270 Ma, Mao et al., 2008）, which are widely distributed in different tectonic domains in North Xinjiang, host magmatic sulfide ore deposits, making North Xinjiang the second most important region for Ni resources in China. The bulk of Cu-Ni ore deposits in East Tianshan, making up a large portion of Ni resources in North Xinjiang, were concentrated in the east of East Tianshan （the Huangshan- Jing＇erquan region） （Feng Yanqing, et al., 2017）, while no any analogue was discovered in the west of East Tianshan until the Lubei Cu-Ni （Co） ore deposit （90°21＇E, 42°10rN） was identified by Xinjiang Geological Survey in 2014. The Lubei Cu-Ni （Co） ore deposit is a medium- to large- sized deposit with Ni and Cu grades in the range 0.2%- 7.76% and 0.2%-2.30%, respectively. This work has initiated the prospection for a large-sized Cu-Ni ore deposit in the west of East Tianshan.

Abiotic Methane Reservoirs in the Western Tianshan HP–UHP Metamorphic Belt,China

Natural gas,consisting primarily of methane(CH_(4)),has become a major source of clean energy in modern society in many parts of the globe.Recent experimental observations and discoveries of deep-sourced abiotic CH_(4)in cold subduction zones indicate the important ability of cold subducted slabs to generate natural gas reservoirs.However,most CH_(4)flux and reservoirs remain unknown and their potential is overlooked in global carbon flux estimations.Massive abiotic CH_(4)-rich fluid inclusions(FIs)in garnet and omphacite from ultrahigh-pressure(UHP)eclogites have been found in the Western Tianshan(WT)UHP metamorphic belt,which provides one ideal case for quantification of abiotic CH_(4)stored in the cold subducted crust.By two methods,we assess the abiotic CH_(4)content stored in the Chinese WT HP–UHP metamorphic belt.Our calculations show that at least 113 Mt CH_(4)is stored in the WT eclogites.We also discuss the implications for CH_(4)reservoirs in subduction zones worldwide and speculate that the cold subduction zones may represent one of the largest,yet overlooked,sources of abiotic CH_(4)on Earth,which should not be ignored in the global natural resource and carbon flux estimations.

新疆中天山北坡断裂带不同海拔高度土壤温度分布特征

研究中天山断裂带从高山带到准噶尔盆地边缘整个过渡带的土壤温度分布特征有助于理解干旱区土壤环境特征,从而为土地利用、农业生产提供依据。本文选取新疆中天山断裂带海拔高度呈梯度分布的6个气象站2005年至2020年各层土壤温度的日观测数据,利用统计方法分析了不同地形、不同深度土壤温度随海拔高度的变化特征以及不同海拔高度土壤温度随深度的变化特征。分析表明:中天山北坡土壤温度变幅随海拔高度的降低而升高。不同地形的土壤最高温和最低温的年温差浅层大于深层,由浅至深年最高温度和年最低温度出现的时间逐渐推迟;年内中天山北坡不同海拔高度0~20 cm的土壤日平均温度曲线大致呈余弦函数曲线,320 cm深度的土壤温度基本呈正弦函数分布,较0~20 cm地温的最高和最低晚3个月左右。研究区土壤温度随海拔高度降低呈现先升高后降低的趋势。在海拔为3539~600 m高度范围,土壤温度随着海拔的升高而降低。在600~441 m高度范围,土壤温度随着海拔的下降而下降;0~20 cm为土壤温度变化的活跃层,40 cm深度的土壤温度可称之为过渡层,320 cm深度称为土壤温度的稳定层,80~160 cm称为土壤温度的次稳定层。

天山北坡西部雪岭云杉海拔梯度生态弹性变化

基于天山北坡西部温泉哈夏林区间隔100 m海拔高度采集的雪岭云杉梯度样本的断面积生长量资料,分析树木生态弹性变化。干旱事件是区域生态弹性最主要的干扰因子,高温事件也是干扰因子之一。干扰因子的强度会造成生态弹性梯度特征的变化。在极端干旱年份,哈夏林区梯度生态弹性特征最显著,即中高海拔为强抵抗力和弱恢复力,而低海拔则呈相反态势,并出现生长衰退现象。中旱事件时不同海拔均为强抵抗力和较强的恢复力,高温年份低海拔呈现弱抵抗力和弱恢复力。在发生持续干旱时,不同海拔高度的树木生长均受到遏制,但低海拔衰退强度大于高海拔区域,高海拔区域树木对干旱的适应能力要强于中低海拔。

天山北坡经济带城乡聚落格局变化与影响因素分析

以天山北坡经济带城乡聚落为研究对象,采用景观格局指数、地理信息系统(GIS)空间分析、位序-规模法等分析1980-2020年间城乡聚落格局的变化,结合地理探测器从自然、区位及社会经济因素探究城乡聚落格局的影响因素。结果表明:1980-2020年间,城乡聚落数量、规模持续扩张且趋于集聚,前20 a扩张以耕地、草地为主,后20 a以未利用地为主;城乡聚落密度变化显著,高密度区主要集中在各绿洲呈现“多核集中分布”特征,中密度区沿高密度区周围扩张,低密度区沿绿洲边缘分布并在非绿洲区有扩张;首位聚落规模发展较好,趋于位序-规模曲线,中型聚落略微发育,小型聚落数量持续减少;交通等区位因素是天山北坡城乡聚落格局的首位影响因素,社会经济因素次之,自然地理因素影响较小,各影响因素差异显著。

近30年天山北坡改进型遥感生态指数时空变化及其驱动因素

天山北坡是西北地区重要的生态功能区和重要经济带,受气候变化和人类活动的影响,脆弱的生态环境面临着巨大挑战,但目前对该地区生态环境质量时空变化、特征及驱动力的认识较少。为此,本文利用改进型遥感生态指数(ERSEI)、空间自相关分析、多元线性回归分析和地理加权分析方法揭示天山北坡1990、2000、2010和2020年4个时期生态环境质量时空变化、特征及其驱动因素。结果表明:(1)1990-2020年天山北坡ERSEI先大幅下降后逐渐恢复并持续上升,生态环境质量逐渐改善并趋于稳定,总体呈“东优西劣”的空间格局;(2)天山北坡生态环境对气候变化较为敏感,温度是ERSEI变化的最重要驱动因子;(3)不同驱动因素对ERSEI的影响存在显著的空间异质性,自然因素对局部ERSEI空间分异起主导作用,人为因素则对年际ERSEI变化产生重要影响。这表明气候变化和人类活动显著影响ERSEI变化,未来应科学规划各类经济活动,减缓气候变化效应,提升天山北坡生态安全和环境可持续性。

太岳山17.9亿年英安斑岩的发现及其对华北克拉通南部裂谷系成因的约束

熊耳群火山岩系主要分布于华北克拉通南部地区,主体喷发时限是1.75~1.80Ga。作为华北克拉通早期板块构造调整阶段的首次大规模岩浆活动,该火山-侵入岩系的形成时限、时空分布规律和地球动力学背景尚有争议,制约了对华北克拉通中元古代构造演化的进一步认识。本次研究在华北中部太岳山地区识别出中元古代英安斑岩,与古元古代花岗质片麻岩围岩呈侵入关系,无明显变质变形。锆石U-Pb年龄分析结果表明,该英安斑岩形成于1.79Ga,属于熊耳期岩浆活动的产物。样品中约90%的锆石显示出~1.92Ga和~2.16Ga两期年龄峰值,推测其为围岩的捕获锆石。英安斑岩SiO_(2)含量为65.12%~66.11%,A/CNK=0.91~1.05,全碱(K_(2)O+Na_(2)O)含量为6.85%~7.28%,Na_(2)O/K_(2)O=0.48~0.54,属于钾玄岩系列。样品稀土元素含量较高,亏损Nb、Ta、Zr、Hf等高场强元素,富集Rb、Ba、La等大离子亲石元素,与华北克拉通南部地区熊耳期英安-流纹斑岩的地球化学特征完全一致,指示板内伸展环境。太岳山熊耳期英安斑岩的发现,贯通了中条山地区的熊耳群火山岩系、吕梁地区汉高山群和小两岭火山岩系,完善了熊耳三叉裂谷系北支的空间分布范围,是华北克拉通中部地区开启中元古代裂陷作用演化的重要岩浆记录。

天山北坡城市群国土空间格局识别与时空变化分析

气候变化和人类活动大环境下,探索国土空间格局演化特征及其规律对进一步缓和绿洲地区人地矛盾有着重要的意义。以天山北坡城市群为例,选取2000、2010年和2020年3期土地利用数据及DEM数据,基于“三生”空间理论对天山北坡城市群国土空间结构数量与空间分布进行分析。结果表明:(1)20 a间天山北坡城市群“三生”空间类型面积呈不同程度的增减,其中水域和林地生态空间的转出量最多,牧草和其他生态空间两者间相互的转换数量最大;(2)研究区除阜康市、木垒哈萨克自治县、奇台县、石河子市及乌鲁木齐市的国土空间利用程度综合指数呈小幅度增加和递减外,其他县域呈逐年提高趋势;(3)生产空间的核密度高值区呈东南-西北条带状,连片分布于研究区的中部,而生态空间的核密度高值区则分布于研究区外围;生活空间的核密度高值区以乌鲁木齐市为中心呈点状分布,周围衍生出许多零碎的中值点,总体分布较为破碎,空间连接性较低。

北天山巴音沟石炭纪安山岩岩石成因及构造意义

北天山增生杂岩带是北天山洋最终闭合的产物,对其中分布的晚古生代火山岩开展详细的地质学、年代学和地球化学研究对恢复古亚洲洋的构造演化历史具有重要的科学意义。笔者选取北天山增生杂岩带巴音沟石炭纪安山岩为研究对象,在详细的野外地质调查基础之上、对其开展系统的岩石学、矿物学、地质年代学以及全岩主微量地球化学综合分析。研究发现:①北天山巴音沟中的这套安山岩具有较低的全岩MgO含量(<3%),明显区别于典型的高镁安山岩(MgO>6%),但其具有较高的Mg#值(>45),结合其微量元素特征,表明安山岩形成于与板块俯冲相关的汇聚板块边缘,其中幔源物质参与了安山岩的形成和演化。②LA-ICP-MS锆石U-Pb加权平均年龄为(324.1±1.1)Ma(MSWD=1.5),代表了巴音沟安山岩的形成时代为早石炭世晚期的霍夫期。文中的北天山石炭纪安山岩是基性下地壳部分熔融形成的长英质熔体和幔源熔体混合的产物。结合区域地质资料,进一步限定了北天山洋在早石炭世晚期可能仍然没有闭合。

基于资源约束的新疆天山北坡乡村建设发展模式探究

新疆地理环境特殊、生态脆弱、气候干旱、经济滞后、人文环境独特。该区域乡村的发展在自然资源的约束下面临更大的局限性和挑战性。基于上述背景,新疆乡村走出自己的发展路径、提高自然环境适应能力迫在眉睫。文章对天山北坡的区域资源进行梳理和归纳,根据区域现状调研和分析,将其分为农牧业资源、区位资源、人文生态资源,总结出3种大类资源下的7种乡村建设模式。为自然资源匮乏的乡村建设发展提供参考与借鉴。