Paleomagnetic and geochronological constraints on the post-collisional northward convergence of the southwest Tian Shan, NW China

A combined paleomagnetic and geochronological study is reported of Paleogene basalt lavas and an intercalated red bed succession, comprising a minimum of 14 basalt flows and 10 red bed horizons in the Tuoyun Basin of the southwest Tian Shan Range, China. Two basalt matrix samples yield ⁴⁰Ar / ³⁹Ar isochron ages of 58.5 ± 1.3 Ma (2σ, MSWD = 0.9) and 60.4 ± 1.3 Ma (2σ, MSWD = 1.7). These compare well with a previously published K–Ar dilution age of 61.7 ± 2.3 Ma for comparable Paleogene basalts and confirm that the younger pulse of magmatism in this basin is represented by both intrusive and extrusive activity. Demagnetization and component analysis identify a stable characteristic remanence (ChRM) with predominantly reversed polarity following removal of secondary remanence by peak demagnetization steps below 250–350 °C or 5 mT. Rock magnetic analysis identifies pseudo-single domain magnetite or titanomagnetite as carriers. The stable ChRM passes a fold test; it was probably acquired at the time of lava emplacement. Results from the bulk of the collection imply that paleomagnetic data from the upper and lower ( 115 Ma) basalt series in the Tuoyun Basin are not distinguishable at the 95% significance level and indicate that this tectonic domain remained essentially stationary with respect to the Earth's spin axis for 50 Ma prior to onset of the India/Asia collision in early Eocene times. It is therefore probable that no paleomagnetically detectable crustal shortening occurred in the southwest Tian Shan prior to collision. Paleomagnetic data sets from the Tuoyun Basin also show that little or no paleolatitude difference is present between the Tian Shan and the reference latitude of Eurasia at 60 Ma. This supports previous evidence suggesting that central Asian blocks in the vicinity of the Tian Shan are unlikely to have experienced appreciable northward convergence relative to Eurasia since onset of the India/Asia collision and initiation of the Himalaya.     

新疆东天山小白石头黑云母花岗岩年代学、地球化学特征及其地质意义

小白石头黑云母花岗岩位于中天山地块东部南缘。LA—ICP—MS测得该岩体的锆石U—Pb年龄为322＋5Ma（MSWD=3．2）。地球化学测试分析表明：小白石头黑云母花岗岩以高硅（73．46％～75．86％）、富碱（Na20＋K20=7．1％～8．2％）和弱过铝质（A／CNK=1．002～1．02）为特征。稀土元素C1球...     

Quaternary folding of the eastern Tian Shan, northwest China

The Tian Shan, east–west trending more than 2000 km, is one of most active intracontinental mountain building belts that resulted from India–Eurasia collision during Cenozoic. In this study, Quaternary folding related to intracontinental mountain building of the Tian Shan orogenic belt is documented based on geologic interpretation and analyses of the satellite remote sensing images [Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM) and India Remote Sensing (IRS) Pan] combined with field geologic and geomorphic observations and seismic reflection profiles. Analyses of spatial–temporal features of Quaternary folded structure indicate that the early Quaternary folds are widely distributed in both piedmont and intermontane basins, whereas the late Quaternary active folds are mainly concentrated on the northern range-fronts. Field observations indicate that Quaternary folds are mainly characterized by fault-related folding. The formation and migration of Quaternary folding are likely related to decollement surfaces beneath the fold-and-fault zone as revealed by seismic reflection profiles. Moreover, analysis of growth strata indicates that the Quaternary folding began in late stage of early Pleistocene (2.1–1.2 Ma). Finally, tectonic evolution model of the Quaternary deformation in the Tian Shan is presented. This model shows that the Quaternary folding and faulting gradually migrate toward the range-fronts due to the continuous compression related to India–Eurasia collision during Quaternary time. As a result, the high topographic relief of the Tian Shan was formed.     

Cosmogenic radionuclide dating of glacial landforms in the Lahul Himalaya,northern India: defining the timing of Late Quaternary glaciation

The timing of glaciation in the Lahul Himalaya of northern India was ascertained using the concentrations of cosmogenic ¹⁰Be and ²⁶Al from boulders on moraines and drumlins, and from glacially polished bedrock surfaces. Five glacial stages were identified: Sonapani I and II, Kulti, Batal and Chandra. Of these, cosmogenic exposure ages were obtained on samples representative of the Batal and Kulti glacial cycles. Stratigraphical relationships indicate that the Sonapani I and II are younger. No age was obtained for the Chandra glacial advance. Batal Glacial Stage deposits are found throughout the valley, indicating the presence of an extensive valley glacial system. During the Kulti Stage, glaciers advanced ca. 10 km beyond their current positions. Moraines produced during the Batal Stage, ca. 12–15.5 ka, are coeval with the Northern Hemisphere Late‐glacial Interstadial (Bølling/Allerød). Deglaciation of the Batal Glacial Stage was completed by ca. 12 ka and was followed by the Kulti Glacial Stage during the early Holocene, at ca. 10–11.4 ka. On millennial time‐scales, glacier oscillations in the Lahul Himalaya apparently reflect periods of positive mass‐balance coincident with times of increased insolation. During these periods the South Asian summer monsoon strengthened and/or extended its influence further north and west, thereby enhancing high‐altitude summer snowfall. Copyright © 2001 John Wiley & Sons, Ltd.     

东天山库姆塔格发现辉长岩中钼的超常富集

在新疆东天山库姆塔格新发现了辉长岩中钼元素的超常富集,超过了目前的工业品位。从野外产状看,与钼矿化直接相关的岩石均为辉长岩,共两类:一是规模较小但全岩矿化的辉长岩脉;二是规模较大但没有矿化的辉长岩体;矿化的辉长岩脉穿插于非矿化的辉长岩体之中。虽然辉长岩体矿区东侧有中酸性岩浆岩存在,但野外产状和现有的物化探工作尚未发现钼矿化与中酸性岩浆岩有直接关系。无论辉长岩的形成与钼的富集是否属于同一次地质作用的产物,这都可能是一种尚未被认识的、全新的钼矿床(矿化)类型,具有重要的理论意义。     

Multistage Enrichment of the Sawafuqi Uranium Deposit: New Insights into Sandstone-hosted Uranium Deposits in the Intramontane Basins of Tian Shan, China

Meso-Cenozoic intracontinental orogenic processes in the Tian Shan orogenic belt have significant effect on the sandstone-hosted uranium deposits in the intramontane basins and those adjacent to the orogen. The Sawafuqi uranium deposit, which is located in the South Tian Shan orogenic belt, is investigated to reveal the relationships between uranium mineralization and orogenies. Recent exploration results show that the Sawafuqi uranium deposit has tabular, stratiform, quasi-stratiform, and lens-like orebodies and various geological characteristics different from typical interlayer oxidation zone sandstone-hosted uranium deposits. Systematic studies of ore samples from the Sawafuqi uranium deposit using a variety of techniques, including thin section observation, α-track radiograph, electron microprobe and scanning electron microscope, suggest that uranium mineralization is closely related to pyrite and organic matter. Mineralization-related alterations in the host rocks are mainly silicification and argillation including kaolinite, illite(and illite-smectite mixed layer) and chlorite. Tree stages of mineralization were identified in the Sawafuqi uranium deposit:(i) uranium-bearing detritus and synsedimentary initial pre-enrichment;(ii) interlayer oxidization zone uranium mineralization; and(iii) vein-type uranium mineralization. The synsedimentary uranium pre-enrichment represents an early uranium enrichment in the Sawafuqi uranium deposit, and interlayer oxidation zone uranium mineralization formed the main orebodies, which are superimposed by the vein-type uranium mineralization. Combining the results of this study with previous studies on the Meso-Cenozoic orogenies of South Tian Shan, it is proposed that the synsedimentary uranium pre-enrichment of the Sawafuqi uranium deposit was caused by Triassic Tian Shan uplift, and the interlayer oxidation zone uranium mineralization occurred during the Eocence-Oligocene period, when tectonism was relatively quiet, whereas the vein-type uranium mineralization took place in relation to the strong orogeny of South Tian Shan since Miocene.     

西天山博故图金矿床地质特征和找矿预测

博故图金矿床位于西天山石炭纪—二叠纪裂谷带中,其矿体赋存于构造破碎带内的大哈拉军山组火山碎屑岩、石英钠长斑岩及辉绿岩中。矿体受东西向基底断裂和北西向次级张扭性断裂带控制,对围岩没有选择性。与金矿化紧密相关的蚀变类型为硅化、黄铁矿化、毒砂矿化、泥化、绿泥石化。依据火试金分析结果圈定金矿体42条,矿体长45~1050 m,斜深34~670 m,平均厚度1.31~9.49 m,最大35.2 m,平均品位1.2~3.46×10-6,最高品位40×10-6,矿床平均品位2.01×10-6,金资源量(控制+探明+推测)达大型,矿床类型为浅成低温热液型金矿。金矿带上发育金、砷、银、钼等元素异常,矿体位于激电高极化率异常梯度带上,物、化探综合勘查成果显示Ⅰ号金矿带及其外围仍有很大找金潜力。     

Development of Tectonic Geomorphology Study Promoted by New Methods in China: A Viewpoint from Reviewing the Tian Shan Researches

Tectonic Geomorphology is an important branch of Geomorphology. Now the scope of tectonic geomorphology study has covered the interactions between tectonics, climate, surface processes and the influence on geomorphic evolution. The study of tectonic geomorphology in China started at the beginning of the 20th century, developed gradually in the 1950s, and entered a rapid development stage in the new century. Based on the long-term development, the study of tectonic geomorphology in China has formed a relatively complete theoretical and methodological system, and now presents a trend of the continuous intersection and integration with other adjacent disciplines. Now, several books on tectonic geomorphology have been published. The representative book abroad is Tectonic Geomorphology which was edited by Burbank D. W. and Anderson R. S., and was first published in 2001 and reprinted in 2012. In China, the first book on tectonic geomorphology is Active Tectonic Geomorphology which was edited by Yang Jingchun and Li Youli and was first published in 2011.In recent years, the tectonic geomorphology study has been absorbing and integrating the new ideas and new methods of other disciplines, significantly promoting the development of tectonic geomorphology. At the 2019 China Geographic Congress & the 110th anniversary of the establishment of the Chinese Geographical Society, the authors organized the session "Theory, Method and Application of Tectonic Geomorphology", aiming to present the recent progresses of tectonic geomorphology study in China. Later, invited by the editorial office, the authors organized the special column with the same name in the journal Advances in Earth Science. The contents of this column mainly dealt with the classical theoretical problems of geomorphology (the evolution and the controlling mechanism of river terrace, planation surface, and alluvial fan), new methods (such as K-feldspar thermoluminescence thermochronology, detrital zircon U-Pb chronology), and models and numerical simulation of tectonic geomorphology evolution. Because of the limited number of the articles, it was impossible for this column to comprehensively present the recent progresses in the study of tectonic geomorphology in China. Therefore, this paper first briefly reviewed the history of the development of tectonic geomorphology in China and the basic trend of tectonic geomorphology. The authors started the study of neotectonics and tectonic geomorphology in the Tian Shan range and its foreland basins about 15 years ago (exactly in 2002). The main aim of this paper was to explore the contributions of the interdisciplinary and new methods to the development of tectonic geomorphology study, by reviewing the main achievements in the tectonic geomorphology study conducted in the Tian Shan and its foreland basins during the past 20 years. These achievements include the history of uplift and exhumation during the Cenozoic times, the chronology and genesis of the late Cenozoic terrigenous sedimentary sequences in the foreland basins, the characteristics of the late Quaternary active tectonic deformation in the foreland and intermontane basins, the late Quaternary river geomorphology (geomorphic framework, chronology, and cause of formation), and erosion rates of the catchment basins. At the end of this paper, it was pointed out that, two aspects may need more attention in the future tectonic geomorphology study, i.e. the comparative study at different time scales and the better constraint of the formation age of river terrace.     

高精度航磁资料在新疆西天山地区 金属找矿中的应用

新疆西天山地区海拔高,地形切割大,开展地面矿产普查工作难度很大。充分利用高精度航磁资料,以区域成矿规律为基础,结合地质、矿产、化探、遥感等资料,研究不同规模、形态和强度的磁异常,通过地面查证,可以直接发现强磁性磁铁矿体,同时通过发现和圈定中弱磁性的中酸性岩体进而找到与之密切相关的多金属矿产。利用上述找矿思路,在西天山地区取得了很好的找矿效果,发现了铁、铜、金等不同种类金属矿产。因此高精度航磁资料在该地区找矿过程q-可以发挥非常重要的作用,能有效指导地面矿产勘查。     

东天山中段区域化探异常评价方法研究

本文利用1/20万区域化探数据,研究了东天山中段地区针对不同类型铜矿化的元素组合异常圈定方法。选择典型（含）铜矿床及其周围地段的化探测量点为建模样本,通过因子分析,查明针对不同矿化类型的指示元素定量组合;以因子得分为综合指标,用泛克里格剩余值圈定化探异常。结果得到3个元素组合：Cu-Co-Ni-Mn-V-Fe-Cr组合...     

Kohonen人工神经网络在新疆东天山地区斑岩型钼矿资源预测中的应用

采用多源信息找矿模型,结合Kohonen人工神经网络对新疆东天山地区斑岩型钼矿进行了成矿预测。通过该地区已有斑岩型钼矿的成矿、控矿规律,确定了5类预测变量。由于东天山钼矿床已知样本较少,使用非线性的Kohonen人工神经网络法进行少模型预测。此方法不依赖预测区域的样本数量,实行非监督分类。分类结果显示:东天山地区2个典型钼矿床皆落入A类成矿有利区域,证明分类效果较为可信。实验结果表明,该方法操作简便,是一种较为快捷、有效的预测方法。     

Late Cenozoic Tectonics Along the Northwestern Margin of the Tarim Basin: Interactions Between the Tarim Basin and the Southern Tian Shan, West China

LATE CENOZOIC TECTONICS ALONG THE NORTHWESTERN MARGIN OF THE TARIM BASIN: INTERACTIONS BETWEEN THE TARIM BASIN AND THE SOUTHERN TIAN SHAN, WEST CHINAgrants 4 98340 50and 4 9732 0 90fromtheNSFofChina;;andproject96 913 0 7 0 1fromtheMinistryofSci enceandTechnology ,China…     

Meso-Cenozoic tectonic evolution of the Talas-Fergana region of the Kyrgyz Tien Shan revealed by low-temperature basement and detrital thermochronology

This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the second place, we also present new detrital apatite fission track data on the Meso-Cenozoic sediments from fault related basins and surrounding intramontane basins. Our results confirm multistaged Meso-Cenozoic tectonic activity, possibly induced by the accretion of the so-called Cimmerian blocks to the Eurasian margin. New evidence for this multi-staged thermo-tectonic activity is found in the data of both basement and Meso-Cenozoic sediment samples in or close to the Talas-Fergana Fault.Zircon(U-Th)/He and apatite fission track data constrain rapid Late TriassiceE arly Jurassic and Late JurassiceE arly Cretaceous basement cooling in the Kyrgyz Tien Shan around 200 Ma and 130 -100 Ma respectively. Detrital apatite fission track results indicate a different burial history on both sides of the Talas-Fergana Fault. The apatite fission track system of the Jurassic sediments in the Middle Tien Shan unit east of the Talas-Fergana Fault is not reset, while the Jurassic sediments in the Fergana Basin and Yarkand-Fergana Basin, west of the fault zone, are partially and in some cases even totally reset. The totally reset samples exhibit Oligocene and Miocene ages and evidence the Cenozoic reactivation of the western Kyrgyz Tien Shan as a consequence of the India-Eurasia convergence.     

西天山卡特巴阿苏金矿床成矿年代学及其地质意义-来自绢云母~(40)Ar-~(39)Ar同位素年龄证据

新疆卡特巴阿苏金矿床是近年来在西天山地区新发现的一个大型金矿床。该矿床大地构造位置处于塔里木板块和哈萨克斯坦-准噶尔板块结合部位的那拉提构造-岩浆岩带,其金矿体主要赋存于蚀变二长花岗岩内。为了确定金矿化的形成时代,对该矿床主成矿阶段与金矿化密切相关的蚀变绢云母开展了40Ar-39Ar同位素定年测试。绢云母40Ar-39Ar坪年龄为(268.56±1.8)Ma,正等时线年龄为(268.38±2.2)Ma,反等时线年龄为(268.52±2.2 Ma),三者在误差范围内一致,测试结果可信,可代表卡特巴阿苏金矿化的形成年龄,这也是首次对该矿床成矿年龄的精确限定。对比中亚造山带典型金矿床,卡特巴阿苏金矿床是西天山二叠纪后碰撞构造环境下岩浆流体活动的产物,矿床成因属与中温岩浆热液有关的构造蚀变岩型矿床。     

Glacial advances constrained by Be exposure dating of bedrock landslides, Kyrgyz Tien Shan

Numerous large landslide deposits occur in the Tien Shan, a tectonically active intraplate orogen in Central Asia. Yet their significance in Quaternary landscape evolution and natural hazard assessment remains unresolved due to the lack of "absolute" age constraints. Here we present the first ¹⁰Be exposure ages for three prominent (> 10⁷ m³) bedrock landslides that blocked major rivers and formed lakes, two of which subsequently breached, in the northern Kyrgyz Tien Shan. Three ¹⁰Be ages reveal that one landslide in the Alamyedin River occurred at 11–15 ka, which is consistent with two ¹⁴C ages of gastropod shells from reworked loess capping the landslide. One large landslide in Aksu River is among the oldest documented in semi-arid continental interiors, with a ¹⁰Be age of 63–67 ka. The Ukok River landslide deposit(s) yielded variable ¹⁰Be ages, which may result from multiple landslides, and inheritance of ¹⁰Be. Two ¹⁰Be ages of 8.2 and 5.9 ka suggest that one major landslide occurred in the early to mid-Holocene, followed by at least one other event between 1.5 and 0.4 ka. Judging from the regional glacial chronology, all three landslides have occurred between major regional glacial advances. Whereas Alamyedin and Ukok can be considered as postglacial in this context, Aksu is of interglacial age. None of the landslide deposits show traces of glacial erosion, hence their locations and ¹⁰Be ages mark maximum extents and minimum ages of glacial advances, respectively. Using toe-to-headwall altitude ratios of 0.4–0.5, we reconstruct minimum equilibrium-line altitudes that exceed previous estimates by as much as 400 m along the moister northern fringe of the Tien Shan. Our data show that deposits from large landslides can provide valuable spatio-temporal constraints for glacial advances in landscapes where moraines and glacial deposits have low preservation potential.     

中-哈-吉-乌天山变形带容矿金矿床:成矿环境和控矿要素与找矿标志

天山是全球第二大金矿富集区,世界级和大型-超大型金矿床东西成带横贯中国新疆中部—哈萨克斯坦东南部—吉尔吉斯斯坦—乌兹别克斯坦,构成巨型跨境金成矿带。天山巨型跨境金成矿带和重要金矿床形成的地质环境、成矿的控制要素、找矿勘查的标志都是学术界和工业界高度关注的重大地质和找矿问题。通过广泛、深入地文献调研和境内外天山较全面野外地质矿产调查与研究,本文认为中-哈-吉-乌天山大规模金成矿主体形成于晚石炭世—早二叠世古亚洲洋闭合后的陆块拼贴变形过程,部分形成于中—晚二叠世陆内走滑变形过程。中天山南、北缘古缝合带及其附近的大型脆性/韧-脆性变形带是巨量金成矿的关键控制因素,多期叠加复合成矿是天山变形带容矿金矿床的显著特征。地壳初始富集、构造变形活化、岩浆热液叠加是天山变形带容矿金矿床的主控因素。“碳质细碎屑岩+脆韧性变形带+海西末期岩体”是中-哈-吉-乌天山变形带容矿大型-超大型金矿的找矿标志组合。     

西南天山新生代造山岩浆作用响应——以皮羌盆地新生代火山岩为例

新疆西南天山皮羌盆地是一个新生代火山构造盆地。盆地内出露4个古火山颈和大量岩墙,部分岩墙与火山颈相连。运用岩相学、岩石地球化学测试分析法研究皮羌盆地内火山岩,研究表明,火山岩具原生岩浆性质,及碱玄岩、碧玄岩和玄武岩岩石组合特征。火山岩产于板内造山带环境,为幔源部分熔融产物,无明显结晶分异。结合托云盆地新生代火山岩岩石地球化学探讨西南天山岩浆触发机制,认为岩石圈局部拆沉作用是触发本区岩浆活动主要机制。     

基于ASTER VNIR-SWIR多光谱遥感数据识别与提取干旱地区岩性信息——以西南天山柯坪隆起东部为例

ASTER多光谱遥感数据目前可以用于岩石矿物资源信息的识别和提取。本研究尝试利用ASTER可见光近红外(VNIR)和短波红外(SWIR)的多光谱遥感数据提取干旱地区的岩石与矿物信息。基于新疆天山西南缘柯坪隆起东部不同地层单元岩石的化学组成和矿物成份以及VNIR-SWIR谱域光谱吸收特征的分析,我们采用相关吸收波段深度(RBD)和波段比值(BR)方法对研究区的多光谱遥感数据进行图像处理,有效区分和识别了白云岩、石灰岩、砂岩以及阿克苏群的蓝片岩—绿片岩和砂质片岩。白云岩的CO_3~(2-)吸收谱带中心波长位于2.32μm,与灰岩的CO_3~(2-)吸收谱带中心波长位置2.35μm相比,具有向短波长方向移动的特点,据此可以利用RBD7、RBD8分别有效的识别白云岩和灰岩;长英质岩石显示Al-OH和Fe~(3+)VNIR-SWIR吸收特征,而基性-超基性岩石显示Fe~(2+)和Fe、Mg-OH特征,利用不同的铁价态和次要矿物可以区分它们:ASTER band2/band1代表了含Fe~(3+)矿物分布信息、ASTER band5/band4代表了含Fe~(2+)矿物分布信息、RBD6可以估计Al-OH矿物的丰度;砂质/泥质片岩含较多的多硅白云母、绿泥石、黑硬绿泥石以及风化后表面覆盖的其它粘土矿物,在2.21μm(band6)存在有特征的吸收谱带,并且在1.65μm(band 4)具有较高的反射率,而蓝片/绿片岩在2.21μm(band 6)反射率较高,不具有明显特征吸收谱带,同时其在1.65μm(band 4)反射率较低,因此蓝片/绿片岩ASTER band4/band6比值低。应用ASTER band4/band6波段比值可以有效的区分开砂质/泥质片岩与蓝片岩/绿片岩。