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1.
The uplift and exhumation process in the Tianshan orogen since the late Paleozoic were likely related to the preservation of ore deposits. This study involved reconstructing the whole tectonic thermal history of the Ouxidaban pluton in central South Tianshan Mountains based on hornblende/plagioclase Ar-Ar and zircon/apatite(U-Th)/He methods. The thermal history and uplift process of central South Tianshan Mountains since the late Paleozoic were analyzed according to the results of previous works and cooling/exhumation rate features. The hornblende yields a plateau age of 382.6±3.6 Ma, and the plagioclase yields a weighted mean age of 265.8±4.9 Ma. The Ouxidaban pluton yields weighted mean zircon(U-Th)/He age of 185.8±4.3 Ma and apatite(U-Th)/He age of 31.1±2.9 Ma, respectively. Five stages of tectonic thermal history of South Tianshan Mountains since the late Paleozoic could be discriminated by the cooling curve and modeling simulation:(1) from the latest Silurian to Late Devonian, the average cooling rate of the Ouxidaban pluton was 7.84°C/Ma;(2) from the Late Devonian to the latest Middle Permian, the average cooling rate was about 2.07°C/Ma;(3) from the latest Middle Permian to the middle Eocene, the cooling rate decreased to about 0.68°C/Ma, suggesting that the tectonic activity was gentle at this time;(4) a sudden increase of the cooling rate(5.00°C/Ma) and the exhumation rate(0.17 mm/a), and crustal exhumation of ~1.83 km indicated that the Ouxidaban pluton would suffer a rapid uplift event during the Eocene(~46?35 Ma);(5) since the middle Eocene, the rapid uplift was sustained, and the average cooling rate since then has been 1.14°C/Ma with an exhumation rate of about 0.04 mm/a and an exhumation thickness of 1.33 km. The strong uplift since the Cenozoic would be related to a far-field effect from the Indian and Eurasian plates' collision. However, it was hysteretic that the remote effect was observed in the Tianshan orogenic belt.  相似文献   

2.
1906年新疆玛纳斯大震区的多层次逆冲构造与深部结构   总被引：10，自引：0，他引：10       下载免费PDF全文
通过对天山北麓 190 6年玛纳斯 7 7级地震区的浅层地震探测资料、石油地震反射剖面、二维电性结构剖面、深地震反射剖面的研究 ,发现玛纳斯地震区多层次活动构造系统的根带 ,它通过脆 -韧转换带与天山活动构造块体内上地壳中的低速、高导层连为一体。低速、高导层可能是天山地壳内正在活动的韧性剪切带 ,而齐古逆断裂 -褶皱带下的脆 -韧转换带是连接深部活动韧性剪切带与地壳浅部脆性破裂的枢纽 ,也是现今孕育和发生大地震的重要构造部位。 190 6年玛纳斯地震发生在脆韧转换带的底部 ,地震区的活动逆断裂和褶皱只是部分记录了深部韧性剪切带活动的信息  相似文献   

3.
The Kalpin nappe structure is a strongest thrust and fold deformation belt in front of the Tianshan Mountains since the Cenozoic time. The tectonic deformation occurred in 5―6 striking Meso-zoic-Cenozoic fold zones, and some renascent folds formed on the recent alluvial-proluvial fans in front of the folded mountains. We used the total station to measure gully terraces along the longitudinal to-pographic profile in the renascent fold zones and collected samples from terrace deposits for age de-termination. Using the obtained formation time and shortening amount of the deformed terraces, we calculated the shortening rate of 4 renascent folds to be 0.1±0.03 mm/a, 0.12±0.04 mm/a, 0.59±0.18 mm/a, and 0.26±0.08 mm/a, respectively. The formation time of the renascent folds is some later than the major tectonic uplift event of the Qinghai-Tibet Plateau 0.14 Ma ago. It may be the long-distance effect of this tectonic event on the Tianshan piedmont fold belt.  相似文献   

4.
库车坳陷是南天山中段新构造运动异常强烈的地区,发育4排近EW向展布的逆断裂-背斜带。通过野外实地考察及前人资料分析,认为该区晚第四纪以来的构造变形主要集中于喀桑托开逆断裂-背斜带、秋里塔格逆断裂-背斜带和最南缘的亚肯逆断裂-背斜带之上,而且不同构造带之间的变形方式存在较大差异。作者利用全站仪(total station)对上述构造带的变形地貌进行了精确测量,并结合年代学分析,得到喀桑托开逆断裂-背斜的地壳缩短速率为1·0~2·0mm/a,秋里塔格逆断裂-背斜带的地壳缩短速率为2·5~3·0mm/a,亚肯盲逆断裂-背斜的地壳缩短速率为1·5~2·0mm/a。晚第四纪以来,库车坳陷SN向总的地壳缩短速率不<5·0~7·0mm/a  相似文献   

5.
焉耆盆地北缘和静逆断裂-褶皱带第四纪变形   总被引：5，自引：5，他引：0       下载免费PDF全文
焉耆盆地是塔里木盆地东北缘天山山间的重要坳陷区,盆地北缘发育的和静逆断裂-褶皱带是一条现今活动强烈的逆断裂-褶皱带,对其第四纪以来缩短量和隆升量的计算有利于分析该区域的构造活动情况,对缩短速率和隆升速率的估计可以与天山造山带其他区域的活动速率进行横向对比,从而反映出焉耆盆地在天山晚新生代构造变形的作用。在深部资料不足的情况下,对背斜形态完整、构造样式简单的和静逆断裂-褶皱带,利用地表可获得的地层和断层产状,通过恢复褶皱几何形态,计算褶皱的缩短量、隆升量和断层滑动量,得到逆断裂-褶皱带早更新世晚期(1.8Ma)、中更新世(780ka)和晚更新世中期(80ka)以来的缩短量分别为1.79km、0.88km和26m,初步估计的缩短速率分别为0.99mm/a、1.13mm/a和0.33mm/a。显示和静逆断裂-褶皱带自开始形成以来构造活动强度并不一致。与地壳形变观测结果对比,作为南天山东段最主要的坳陷区,焉耆盆地吸收了这一区域(86°～88°E)的大部分地壳缩短,且主要表现为盆地北缘新生逆断裂-褶皱带的强烈变形。  相似文献   

6.
In order to derive a radiometric age marker for the end of the penultimate glacial–interglacial transition, we compiled published U-series isotope measurements on corals from the period extending from stage 6 to the middle of the last interglacial, and computed the corresponding open-system ages using Thompson et al. model (Thompson, W.G., Spiegelman, M.W., Goldstein, S.L., Speed, R.C., An open-system model for U-series age determinations of fossil corals. Earth Planet. Sci. Lett. 210 (2003) 365–381). We obtain a global mean age of 126 calendar kyr BP (ka) ± 1.7kyr (2σ) for the beginning of the last interglacial sea level high stand. After showing that the phase relationships observed between changes in sea level, North Atlantic benthic and planktonic foraminifera oxygen isotopic records, and atmospheric methane over the last deglaciation were likely also valid over the penultimate deglaciation, we derive an age of 131.2ka ± 2kyr (2σ) for the abrupt increase in atmospheric CH4 and North Atlantic surface temperature marking the end of the penultimate glacial–interglacial transition. This age is consistent with U–Th dates of the penultimate glacial–interglacial transition recorded in speleothems from sites where speleothems isotopic records are synchronous with North Atlantic temperature records over the last deglaciation. Finally, we show that the phase obtained between the climatic response and northern hemisphere summer insolation is not constant from Termination II to Termination I, implying that northern hemisphere summer insolation alone cannot explain the timing of terminations.  相似文献   

7.
Introduction The Tianshan orogenic belt between the Tarim and Junggar basins has re-uplifted in Cenozoic due to the collision and the northwards push-compression of Asia-India plate. The special active tectonic zones have been formed along both south and north margins of the Tianshan mountains (FENG, et al, 1991). The Tianshan seismic belt is one of the major seismic belts in China. A se-ries of strong earthquakes occurred in two flanks of the Tianshan mountains in 20th century, such as …  相似文献   

8.
The middle part of the Tianshan Mountains in Xinjiang is located in the north-central part of the Tianshan orogenic belt, between the rigid Tarim Basin and Junggar Basin. It is one of the regions with frequent deformation and strong earthquake activities. In this paper, 492 MS>2.5 earthquake events recorded by Xinjiang seismograph network from 2009 to 2018 were collected. The MS3.5 earthquake was taken as the boundary, the focal mechanism solutions of the earthquake events in this region were calculated by CAP method and FOCEMEC method respectively. At the same time the focal mechanism solutions of GCMT recorded historical earthquake events in this region were also collected. According to the global stress map classification standard, the moderate-strong earthquakes in the region are mainly dominated by thrust with a certain slip component, which are distributed near the combined belts of the Tarim Basin, Junggar Basin, Turpan Basin and Yili Basin with Tianshan Mountains. The thrust component decreases from south to north, while the strike-slip component increases. The spatial distribution characteristics of the tectonic stress field in the middle section of the Tianshan Mountains in Xinjiang are obtained by using the damped regional-scale stress field inversion method. The maximum principal compressive stress in axis the study area rotated in a fan shape from west to east, the NW direction in the western section gradually shifted to NE direction, its elevation angle is nearly horizontal, in the state of near horizontal compression. The minimum principal compressive stress axis is nearly EW, and the elevation angle is nearly vertical. Influenced by large fault zones such as Kashi River, Bolhinur, Nalati, Fukang, the southern margin of the Junggar and the north Beiluntai, the local regional stress field presents complex diversity. Under the influence of the northward extrusion of Pamir and Tarim blocks, the whole Tianshan is shortened by compression, but its shortening rate decreases from south to north and from west to east, the stress shape factor increases gradually from west to east, the intermediate principal compressive stress axis exhibits a change in compression to extension. There are some differences in the characteristics of tectonic stress field between the north and south of Tianshan Mountains. The regional maximum principal compressive stress axis is 15° north by east on the south side, while it is nearly NS on the north side. The deformation of the Tianshan Mountains and the two basins on both sides is obviously larger than that in the inside of the mountain. Changes in the crustal shortening rate caused by the rotation of the rigid Tarim block and Junggar block to the relatively soft Tianshan block, as well as the uplifts of Borokonu and Bogda Mountains, the comprehensive influence of the material westward expansion constitute the stress field distribution characteristics of the north and south sides of the middle section of Tianshan Mountains. The recent two MS6.6 earthquakes in the region caused the regional stress field to rotate counterclockwise. The post-earthquake stress field and the main source focal mechanism solution tend to be consistent. The seismic activity in the study area is week in the south and strong in the north. The focal depth is about 20km. Most strike-slip earthquakes occur near the junction belt of the Tianshan and Junggar Basin.  相似文献   

9.
The Pochengzi Glaciation is a typical glaciation in Quaternary in the Tianshan Mountains. The glacial landforms comprise several integrated end moraines, like a fan spreading from the north to the south at the mouth of the Muzhaerte River valley and on the piedmont on the southeastern slope of the Tumur Peak, the largest center of modern glaciation in the Tianshan Mountains. The landforms recorded a complex history of the ancient glacier change and contained considerable information of the glacial landscape evolution, and dating these landforms helps us understand the temporal and spatial shifts of the past cryosphere in this valley and reconstruct the paleoenvironment in this region. Electron spin resonance (ESR) dating of the glacial tills in the upper stratum from a well-exposed section, end moraines, and associated outwashes was carried out using Ge centers in quartz grains, which are sensitive to the sunlight and grinding. The results could be divided into three clusters, 13.6–25.3, 39.5–40.4 and 64.2–71.7 ka. Based on the principle of geomorphology and stratigraphy and the available paleoen- vironmental data from northwestern China, the end moraines were determined to deposit in the Last Glaciation. The landforms and the three clusters of ages demonstrate that at least three large glacial advances occurred during the Pochengzi Glaciation, which are corresponding to marine oxygen isotope stage 4 (MIS4), MIS3b and MIS2. The landforms also indicate that the gla- ciers were compound valley glacier in MIS2 and MIS3b and piedmont glacier in MIS4, and the ancient Muzhaerte glacier were 94, 95 and 99 km at their maximum extensions in these three glacial advances.  相似文献   

10.
Introduction The Tianshan Mountain is the youngest cordillera in the present-day continental Asia, and its tectonic evolution is closely related to the collision and subduction between Indian Plate and Eurasian Plate in the Himalayas orogen since Cenozoic…  相似文献   

11.
天山的晚新生代构造变形及其地球动力学问题   总被引：73，自引：6，他引：73  
张培震  冯先岳 《中国地震》1996,12(2):127-140
天山是大陆内部典型的新生代复活造山带，其新生代构造变形的方式，变形量，速度及过程等对于认识大陆内部造山带的变形机理有着重要的意义。本文在对南北天山主要活动构造地质填图和综合研究的基础上，重点探讨了天山的晚新生代构造变形特征及其动力学问题。早更新世以来，特别是早，中更新世之间，天山的构造活动由内部向南北两侧扩展，使得两侧的新生代凹陷逐渐褶皱成山，形成数排新生代褶皱带，整个天山的现代构造活动是一种扇形  相似文献   

12.
利用2009—2011、2011—2013、2013—2015年GPS形变资料,借助最小二乘配置方法、位移与应变的偏导关系,计算获得北天山东部应变场的动态演化结果,重新认识北天山东段构造区的现今活动特征,探讨应变场三个周期空间分布特征与2016年呼图壁6.2级地震的内部联系。结果表明:(1)区域地壳运动速率与应变场强度在时间上表现为“弱-强-弱”的变化特征,主应变率以NNW或NNE向的主压应变为主,第一、三周期N-S向主压应变较小,约(1~2)×10-8/a,第二周期变化显著增强,约(1~6)×10-8/a,第三周期滑动速率显示北天山东段呈“强[(2.2±0.4) mm/a]-弱(不明显)-强[(3.0±1.0) mm/a]”的右旋走滑特征;(2)地震可能更易发生在面应变率场等值线四象限中心区域或正、负过渡区的高密度梯度带内部,这可能是地震孕育过程中利用GPS资料观测到的形变前兆;(3)强震更易发生在剪应变率(最大剪应变率)的高值区或边缘区;(4)相对于面应变率与最大剪应变率等应变场物理量,主应变率更适用于在块体运动方向与性质上给出解释。  相似文献   

13.
Influenced by the far-field effect of India-Eurasia collision, Tianshan Mountains is one of the most intensely deformed and seismically active intracontinental orogenic belts in Cenozoic. The deformation of Tianshan is not only concentrated on its south and north margins, but also on the interior of the orogen. The deformation of the interior of Tianshan is dominated by NW-trending right-lateral strike-slip faults and ENE-trending left-lateral strike-slip faults. Compared with numerous studies on the south and north margins of Tianshan, little work has been done to quantify the slip rates of faults within the Tianshan Mountains. Therefore, it is a significant approach for geologists to understand the current tectonic deformation style of Tianshan Mountains by studying the late Quaternary deformation characteristics of large fault and fold zones extending through the interior of Tianshan. In this paper, we focus on a large near EW trending fault, the Baoertu Fault (BETF) in the interior of Tianshan, which is a large fault in the eastern Tianshan area with apparent features of deformation, and a boundary fault between the central and southern Tianshan. An MS5.0 earthquake event occurred on BETF, which indicates that this fault is still active. In order to understand the kinematics and obtain the late Quaternary slip rate of BETF, we made a detailed research on its late Quaternary kinematic features based on remote sensing interpretation, drone photography, and field geological and geomorphologic survey, the results show that the BETF is of left-lateral strike-slip with thrust component in late Quaternary. In the northwestern Kumishi basin, BETF sinistrally offsets the late Pleistocene piedmont alluvial fans, forming fault scarps and generating sinistral displacement of gullies and geomorphic surfaces. In the bedrock region west of Benbutu village, BETF cuts through the bedrock and forms the trough valley. Besides, a series of drainages or rivers which cross the fault zone and date from late Pleistocene have been left-laterally offset systematically, resulting in a sinistral displacement ranging 0.93~4.53km. By constructing the digital elevation model (DEM) for the three sites of typical deformed morphologic units, we measured the heights of fault scarps and left-lateral displacements of different gullies forming in different times, and the result shows that BEFT is dominated by left-lateral strike-slip with thrust component. We realign the bended channels across the fault at BET01 site and obtain the largest displacement of 67m. And we propose that the abandon age of the deformed fan is about 120ka according to the features of the fan. Based on the offsets of channels at BET01 and the abandon age of deformed fan, we estimate the slip rate of 0.56mm/a since late Quaternary. The Tianshan Mountains is divided into several sub-blocks by large faults within the orogen. The deformation in the interior of Tianshan can be accommodated or absorbed by relative movement or rotation. The relative movement of the two sub-blocks surrounded by Boa Fault, Kaiduhe Fault and BETF is the dominant cause for the left-lateral movement of BETF. The left-lateral strike-slip with reverse component of BETF in late Quaternary not only accommodates the horizontal stain within eastern Tianshan but also absorbs some SN shortening of the crust.  相似文献   

14.
帕米尔东北侧地壳结构研究   总被引：50，自引：17，他引：50  
1998年在帕米尔东北侧伽师及其周边地区完成了两条深地震宽角反射/折射剖面. 结果表明,西昆仑、塔里木和天山在地壳速度结构、构造特征上显示出较大差异. 塔里木块体具有稳定地块的地壳结构特征,地壳平均速度较高(6.5km/s). 向南进入西昆仑,地壳明显增厚,厚度可达0km左右,且地壳平均速度偏低(6.0-6.2km/s),偏低的地壳平均速度主要来源于相对低速度的下地壳结构,反映了西昆仑褶皱系下地壳介质的特征. 向北进入天山后,地壳同样明显增厚,但增厚的程度低于西昆仑下,约为50-55km. 天山地壳同样具有明显低的平均速度(6.2km/s),显示了天山地壳相对"软"的特征,但天山地壳偏低的平均速度来源于广泛分布于中地壳的低速度层和速度偏低的下地壳. 在印度块体向北强烈推挤的作用下,该区地壳遭受强烈的不均匀变形,塔里木块体向南插入西昆仑下,向北插入天山下,形成了该区强烈地震频繁发生的深部构造环境.  相似文献   

15.
盆山结合部的浅-深结构样式是进行陆内造山动力学研究与讨论的重要依据.2007年,在喀什东的天山与塔里木盆地之间的过渡带上,完成了一条近南北向的长度为121 km的主动源深地震反射剖面,显示出盆山结合部现今地壳尺度的构造格架.剖面南部呈现出10~12 km巨厚的沉积盖层,沉积盖层内发育滑脱断层;盆山结合部多排隆起构造以及天山山前上地壳显现出向北倾斜的断裂与地表地质观察吻合;盆山结合带展现出滑脱与逆冲推覆构造相关的断层褶皱;与塔里木盆地稳定沉积层相比,在南天山浅、中层地层受到强烈的变形改造,导致地层比较破碎,反射变弱、连续性较差;时间剖面上可以追踪到比较连续的Moho反射,从南向北有加深的趋势.深地震反射剖面揭露出的西南天山与塔里木盆地的这些浅-深构造,展现出塔里木盆地盖层向南天山滑脱与南天山向塔里木盆地逆冲推覆的特征,反映出陆内汇聚下的盆山耦合关系.  相似文献   

16.
The eruptive history of the Tequila volcanic field (1600 km2) in the western Trans-Mexican Volcanic Belt is based on 40Ar/39Ar chronology and volume estimates for eruptive units younger than 1 Ma. Ages are reported for 49 volcanic units, including Volcán Tequila (an andesitic stratovolcano) and peripheral domes, flows, and scoria cones. Volumes of volcanic units 1 Ma were obtained with the aid of field mapping, ortho aerial photographs, digital elevation models (DEMs), and ArcGIS software. Between 1120 and 200 kyrs ago, a bimodal distribution of rhyolite (~35 km3) and high-Ti basalt (~39 km3) dominated the volcanic field. Between 685 and 225 kyrs ago, less than 3 km3 of andesite and dacite erupted from more than 15 isolated vents; these lavas are crystal-poor and show little evidence of storage in an upper crustal chamber. Approximately 200 kyr ago, ~31 km3 of andesite erupted to form the stratocone of Volcán Tequila. The phenocryst assemblage of these lavas suggests storage within a chamber at ~2–3 km depth. After a hiatus of ~110 kyrs, ~15 km3 of andesite erupted along the W and SE flanks of Volcán Tequila at ~90 ka, most likely from a second, discrete magma chamber located at ~5–6 km depth. The youngest volcanic feature (~60 ka) is the small andesitic volcano Cerro Tomasillo (~2 km3). Over the last 1 Myr, a total of 128±22 km3 of lava erupted in the Tequila volcanic field, leading to an average eruption rate of ~0.13 km3/kyr. This volume erupted over ~1600 km2, leading to an average lava accumulation rate of ~8 cm/kyr. The relative proportions of lava types are ~22–43% basalt, ~0.4–1% basaltic andesite, ~29–54% andesite, ~2–3% dacite, and ~18–40% rhyolite. On the basis of eruptive sequence, proportions of lava types, phenocryst assemblages, textures, and chemical composition, the lavas do not reflect the differentiation of a single (or only a few) parental liquids in a long-lived magma chamber. The rhyolites are geochemically diverse and were likely formed by episodic partial melting of upper crustal rocks in response to emplacement of basalts. There are no examples of mingled rhyolitic and basaltic magmas. Whatever mechanism is invoked to explain the generation of andesite at the Tequila volcanic field, it must be consistent with a dominantly bimodal distribution of high-Ti basalt and rhyolite for an 800 kyr interval beginning ~1 Ma, which abruptly switched to punctuated bursts of predominantly andesitic volcanism over the last 200 kyrs.Electronic Supplementary Material Supplementary material is available in the online version of this article at Editorial responsility: J. Donnelly-NolanThis revised version was published online in January 2005 with corrections to Tables 1 and 3.An erratum to this article can be found at  相似文献   

17.
天山造山带是新生代以来复活隆升的陆内造山带,强烈的地震活动性使得理解和认识天山造山带深部结构及盆山耦合关系尤为重要。文章中使用天山造山带及邻区(40°～49°N,79°～93°E)85个台站2017—2019年的背景噪声资料,结合背景噪声互相关方法获得了6～52 s瑞利波相速度频散曲线,利用基于射线追踪的面波直接反演法对天山中段地壳三维S波速度结构及盆山耦合关系进行研究。结果显示：地壳浅层S波速度分布与构造单元中沉积层厚度相关,塔里木盆地北缘、准噶尔盆地南缘表现为低速,天山造山带表现为高速;到了中下地壳,天山造山带下方存在被高速异常包裹的低速体;莫霍面附近,天山造山带表现出相对低速;准噶尔盆地南缘和天山造山带的地壳厚度分别在45～50 km、50～62 km之间,沿南北向,天山造山带莫霍面呈现较为宽缓的形态;在82°～86.5°E之间,塔里木盆地和准噶尔盆地向天山下方双向俯冲,86.5°～88°E之间,准噶尔盆地向天山南向俯冲,由西向东,不同盆山耦合关系揭示了新生代以来天山中段不同区域构造运动差异,为进一步探讨造山动力过程提供参考。  相似文献   

18.
The Qilian Mountains, as a major orogenic belt in the northeastern margin of the Tibetan plateau, is the forefront of the expansion of the plateau to the northeast, where thrusts and folds dominate tectonic deformation. The Baiyang River starts from the inner Qilian Mountains, flowing northward across various structures, and finally into the Jiuxi Basin. This work focused on exhaustive investigations to the terraces on this river to characterize the Late Quaternary tectonic deformation in this region. The results show that (1)these river terraces on the Baiyang River are segmented, of which multiple levels developed at steep terrains and anticlines in the basin. Bounded by the Niutou Mountains, mainly 2-3 and 4-5 levels of terraces formed in the upper and lower reaches, respectively. (2)The longitudinal profiles along the river suggest a vertical motion rate of the Changma fault as (0.32±0.09)mm/a and crustal shortening rate (0.12±0.09)mm/a. There was no vertical activity since the formation of T5 surface (13ka)on the Hanxia-Dahuanggou fault. At the terrace T5 (9ka)on the Laojunmiao anticline, fold uplift amounts (6.55±0.5)m and shortening amounts (3.47±0.5)m, yielding uplift and shortening rates (1.23±0.81)mm/a and (0.67±0.44)mm/a, respectively. The Baiyang River anticline began to be active about 300ka with uplift and shortening rates (0.21±0.02)mm/a and (0.14±0.03)mm/a, respectively since 170ka. (3)In the Qilian Mountains, there were two different deformation characteristics in response to the expansion of the Tibetan plateau. Shear deformation dominates the inner Qilian Mountains, which is manifested as lateral extrusion of blocks. In the northern margin of Qilian Mountains and Jiuxi Basin, the deformation is dominated by compression, expressing crustal shortening and uplift, and the shortening within the basin accounts about half of the total deformation.  相似文献   

19.
The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evolution of Euro-Asian continent, which resulted in the formation of the present range-and-basin pattern in topography of the Tianshan Mountains and its adjacent areas. Thermochronology results by the method of fission-track dating of apatite suggest three obvious uplifting stages of the Bogad Mountain Chain re-orogeny during the Cenozoic, i.e. 5.6-19 Ma, 20-30 Ma, and 42-47 Ma. The strongest uplifting stage of the mountain is the second one at 20 -30 Ma, when the mountain uplifted as a whole, and the beginning of re-orogeny was no less than 65 Ma. Furthermore, our studies also show that the uplifting types of the mountain are variable in the dif-ferent time periods, including uplifting of mountain as a whole and differential uplifting. The apparently diversified uplifting processes of the mountain chain are characterized by the migration (or transfor-mation) of the uplifting direction of the mountain from west to east and from north to south, and the main process of mountain extending is from north to south.  相似文献   

20.
利用北天山中段最新的流动重力观测数据,通过整理计算平差,绘制该地区半年和一年尺度的重力场变化图像;选取横跨北天山中段乌鲁木齐、独山子两条测线,并分别绘制其重力剖面变化图;结合北天山中段地区动力构造环境,剖析该地区重力变化特征及其与地震孕育之间的关系。分析表明:北天山中段地区重力异常变化值不大,重力变化等值线图和剖面变化图均能较好地反映重力场随时空变化特征;北天山中段动态重力变化特征基本反映了该地区动力构造运动的外部环境;研究区域内的重力场空间格局分布特征较清晰,其重力变化具有明显的分区特征,山体和盆地之间的重力变化具有显著差异,山体与盆地边缘正负重力变化交替出现,且变化相对较平稳。  相似文献   

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