Variation of Uplift Velocit y in Qinghai-Tibet Plateau: Its Occasion and Consequences     

Hong HanjingInstitute of Geology  SSB  Beijing  China 《中国地震研究》1995,(4)

The velocity of uplift in the Qinghai-Tibet plateau has been changed in a remarkable sense by the continental collision.In this paper the buoyancy variation,which occurred in the crustal shortening and thickening process,was used to explain the varied velocities.In the initial stage subcrustal material came from anomalous mantle with high temperature,then the density contrast between crust and mantle was small; in turn both the buoyancy and the surface uplift were gentle.When the thickened crust was squeezed into normal mantle in the later stage,the significant buoyancy would cause a rapid uplift.The variation of buoyancy also affected the stress regime around the plateau.  相似文献   

用大地测量资料检验青藏高原隆升的两种构造演化模式     

许才军 《武汉大学学报(信息科学版)》1995,(2)

对当前地质学和地球物理学方面提出的两种青藏高原构造演化模式进行了分析，着重讨论了用大地测量资料检验构造演化模式的原理和方法，以实测资料初步验证了回流模式的合理性。  相似文献   

攀西地区的深部地壳结构与构造   总被引：22，自引：2，他引：22       下载免费PDF全文

崔作舟  卢德源  陈纪平  张之英  黄立言 《地球物理学报》1987,30(6):566-580

根据1984-1985年地震测深资料,论述了攀西地区的深部地质特征。该区地壳厚50-60km;具高、低速相间的多层结构及断块构造;五个主要速度界面中,界面R₄稳定且清晰,为上、下地壳的分界面,R₆稳定并有较强的能量反射,为壳、幔之间的界面（莫霍面）,莫霍面沿构造带北深南浅（56-50km）,横穿构造带西深东浅（60-48km）。构造带内的上地壳较薄,纵横速度变化均较大,而下地壳较厚,速度较均匀,上地壳底部的低速层,在构造带内较带外薄而浅,P_n速度较低,为7.54-7.80km/s,属壳-幔过渡带,厚13-22km。小江、四开、安宁河及金河等断裂为超壳型或壳内断裂,多为逆冲断层。该构造带的各种深部特征表明它为大陆高原型年轻构造带。  相似文献   

黄土区沟谷发育与气候变化的关系(以洛川黄土塬区为例)   总被引：11，自引：2，他引：11  

袁宝印  巴特尔  崔久旭  殷强 《地理学报》1987,(4)

黄土区沟谷侵蚀与气候变化有密切关系。黄土是干冷气候环境中堆积的地质体,只有在干冷时期才是稳定的。气候变湿润时黄土区发生冲沟侵蚀。洛川黄土塬区20万年以来至少出现过五次明显的侵蚀时期,该区河流的侵蚀与堆积过程恰好和冲沟发育过程相反,但两者在时间上可以较好地对比。  相似文献   

NEW DISCOVERY OF RESHUI-TAOSTUO RIVER FAULT IN DULAN,QINGHAI PROVINCE AND ITS IMPLICATIONS          下载免费PDF全文

LI Zhi-min  REN Zhi-kun  LIU Jin-rui  HA Guang-hao  LI Zheng-fang  WANG Bo  WANG Lin-jian 《地震地质》1979,42(1):18-32

The 40km-long, NEE trending Reshui-Taostuo River Fault was found in the southern Dulan-Chaka highland by recent field investigation, which is a strike-slip fault with some normal component. DEM data was generated by small unmanned aerial vehicle(UAV)on key geomorphic units with resolution<0.05m. Based on the interpretation and field investigation, we get two conclusions:1)It is the first time to define the Reshui-Taostuo River Fault, and the fault is 40km long with a 6km-long surface rupture; 2)There are left-handed dislocations in the gullies and terraces cut by the fault. On the high-resolution DEM image obtained by UAV, the offsets are(9.3±0.5) m, (17.9±1.5) m, and(36.8±2) m, measured by topographic profile recovery of gullies. The recovery measurements of two terraces present that the horizontal offset of T₁/T₀ is(18.2±1.5) m and the T₂/T₁ is (35.8±2) m, which is consistent with the offsets from gullies. According to the historical earthquake records, a M5 3/4 earthquake on April 10, 1938 and a M_S5.0 earthquake on March 21, 1952 occurred at the eastern end of the surface rupture, which may be related to the activity of the fault. By checking the county records of Dulan and other relevant data, we find that there are no literature records about the two earthquakes, which is possibly due to the far distance to the epicenter at that time, the scarcity of population in Dulan, or that the earthquake occurred too long ago that led to losing its records. The southernmost ends of the Eastern Kunlun Fault and the Elashan Fault converge to form a wedge-shaped extruded fault block toward the northwest. The Dulan Basin, located at the end of the wedge-shaped fault block, is affected by regional NE and SW principal compressive stress and the shear stress of the two boundary faults. The Dulan Basin experienced a complex deformation process of compression accompanying with extension. In the process of extrusion, the specific form of extension is the strike-slip faults at each side of the wedge, and there is indeed a north-east and south-west compression between the two controlling wedge-shaped fault block boundary faults, the Eastern Kunlun and Elashan Faults. The inferred mechanism of triangular wedge extrusion deformation in this area is quite different from the pure rigid extrusion model. Therefore, Dulan Basin is a wedge-shaped block sandwiched between the two large-scale strike-slip faults. Due to the compression of the northeast and southwest directions of the region, the peripheral faults of the Dulan Basin form a series of southeast converging plume thrust faults on the northeast edge of the basin near the Elashan Fault, which are parallel to the Elashan Fault in morphology and may converge with the Elashan Fault in subsurface. The southern marginal fault of the Dulan Basin(Reshui-Taostuo River Fault)near the Eastern Kunlun fault zone is jointly affected by the left-lateral strike-slip Eastern Kunlun Fault and the right-lateral strike-slip Elashan Fault, presenting a left-lateral strike-slip characteristic. Meanwhile, the wedge-shaped fault block extrudes to the northwest, causing local extension at the southeast end, and the fault shows the extensional deformation. These faults absorb or transform the shear stress in the northeastern margin of the Tibet Plateau. Therefore, our discovery of the Dulan Reshui-Taostuo River Fault provides important constraints for better understanding of the internal deformation mode and mechanism of the fault block in the northeastern Tibetan plateau. The strike of Reshui-Taostuo River Fault is different from the southern marginal fault of the Qaidam Basin. The Qaidam south marginal burial fault is the boundary fault between the Qaidam Basin and the East Kunlun structural belt, with a total length of ~500km. The geophysical data show that Qaidam south marginal burial fault forms at the boundary between the positive gravity anomaly of the southern East Kunlun structural belt and the negative gravity anomaly gradient zone of the northern Qaidam Basin, showing as a thrust fault towards the basin. The western segment of the fault was active at late Pleistocene, and the eastern segment near Dulan County was active at early-middle Pleistocene. The Reshui-Taostuo River Fault is characterized by sinistral strike-slip with a normal component. The field evidence indicates that the latest active period of this fault was Holocene, with a total length of only 40km. Neither remote sensing image interpretation nor field investigation indicate the fault extends further westward and intersects with the Qaidam south marginal burial fault. Moreover, it shows that its strike is relatively consistent with the East Kunlun fault zone in spatial distribution and has a certain angle with the burial fault in the southern margin of Qaidam Basin. Therefore, there is no structural connection between the Reshui-Taostuo River Fault and the Qaidam south marginal burial fault.  相似文献   

NEW ACTIVITY CHARACTERISTICS AND SLIP RATE OF THE EBOMIAO FAULT IN THE SOUTHERN MARGIN OF BEISHAN,GANSU PROVINCE          下载免费PDF全文

ZHANG Bo  HE Wen-gui  LIU Bing-xu  GAO Xiao-dong  PANG Wei  WANG Ai-guo  YUAN Dao-yang 《地震地质》1979,42(2):455-471

The Ebomiao Fault is a newly discovered active fault near the block boundary between the Tibetan plateau and the Alashan Block. This fault locates in the southern margin of the Beishan Mountain, which is generally considered to be a tectonically inactive zone, and active fault and earthquake are never expected to emerge, so the discovery of this active fault challenges the traditional thoughts. As a result, studying the new activity of this fault would shed new light on the neotectonic evolution of the Beishan Mountain and tectonic interaction effects between the Tibetan plateau and the Alashan Block. Based on some mature and traditional research methods of active tectonics such as satellite image interpretation, trenches excavation, differential GPS measurement, Unmanned Aircraft Vehicle Photogrammetry(UAVP), and Optical Stimulated Luminescence(OSL)dating, we quantitatively study the new activity features of the Ebomiao Fault.
Through this study, we complete the fault geometry of the Ebomiao Fault and extend the fault eastward by 25km on the basis of the 20km-fault trace identified previously, the total length of the fault is extened to 45km, which is capable of generating magnitude 7 earthquake calculated from the empirical relationships between earthquake magnitude and fault length. The Ebomiao Fault is manifested as several segments of linear scarps on the land surface, the scarps are characterized by poor continuity because of seasonal flood erosion. Linear scarps are either north- or south-facing scarps that emerge intermittently. Fourteen differential GPS profiles show that the height of the north-facing scarps ranges from (0.22±0.02)m to (1.32±0.1)m, and seven differential GPS profiles show the height of south-facing scarps ranging from (0.33±0.1)m to (0.64±0.1)m. To clarify the causes of the linear scarps with opposite-facing directions, we dug seven trenches across these scarps, the trench profiles show that the south-dipping reverse faults dominate the north-facing scarps, the dipping angles range from 23° to 86°. However, the south-facing scarps are controlled by south-dipping normal faults with dipping angles spanning from 60° to 81°.
The Ebomiao Fault is dominated by left-lateral strike-slip activity, with a small amount of vertical-slip component. From the submeter-resolution digital elevation models(DEM)constructed by UAVP, the measured left-lateral displacement of 19 gullies in the western segment of the Ebomiao Fault are(3.8±0.5)~(105±25)m, while the height of the north-facing scarps on this segment are(0.22±0.02)~(1.32±0.10)m(L₃-L₇), the left-lateral displacement is much larger than the scarp height. In this segment, there are three gullies preserving typical left-lateral offsets, one gully among them preserves two levels of alluvial terraces, the terrace riser between the upper terrace and the lower terrace is clear and shows horizontal offset. Based on high-resolution DEM interpretation and displacement restoration by LaDiCaoz software, the left-lateral displacement of the terrace riser is measured to be(16.7±0.5)m. The formation time of the terrace riser is approximated by the OSL age of the upper terrace, which is (11.2±1.5)ka BP at (0.68±0.03)m beneath the surface, and(11.4±0.6)ka at (0.89±0.03)m beneath the surface, the OSL age (11.2±1.5)ka BP at (0.68±0.03)m beneath the surface is more close to the formation time of the upper terrace because of a nearer distance to sediment contact between alluvial fan and eolian sand silt. Taking the (16.7±0.5)m left-lateral displacement of the terrace riser and the upper terrace age (11.2±1.5)ka, we calculate a left-lateral strike-slip rate of(1.52±0.25)mm/a for the Ebomiao Fault. The main source for the slip rate error is that the terrace risers on both walls of the fault are not definitely corresponded. The north wall of the fault is covered by eolian sand, we can only presume the location of terrace riser by geomorphic analysis. In addition, the samples used to calculate slip rate before were collected from the aeolian sand deposits on the north side of the fault, they are not sediments of the fan terraces, so they could not accurately define the formation age of the upper terrace. This study dates the upper terrace directly on the south wall of the fault.
Since the late Cenozoic, the new activity of the Ebomiao Fault may have responded to the shear component of the relative movement between the Tibetan plateau and the Alashan Block under the macroscopic geological background of the northeastern-expanding of the Tibetan plateau. The north-facing fault scarps are dominated by south-dipping low-angle reverse faults, the emergence of this kind of faults(faults overthrusting from the Jinta Basin to the Beishan Mountain)suggests the far-field effect of block convergence between Tibetan plateau and Alashan Block, which results in the relative compression and crustal shortening. As for whether the Ebomiao Fault and Qilianshan thrust system are connected in the deep, more work is needed.  相似文献   

青藏高原风火山砂岩的磁性特征及其意义     

董学斌  杨惠心  程立人  李鹏武 《吉林大学学报(地球科学版)》1992,(3)

风火山白垩系紫色砂岩样品的矿物学分析结果表明,大部分样品的磁性载体是铁白云石.根据退磁曲线估计其居里点为500℃左右.当退磁温度增加到600℃左右,铁白云石开始分解,形成磁铁矿,致使样品在此温度段退磁时,其磁性不但不减小反而骤然增加,甚至可达天然剩磁的十几倍,其原生成分受到破坏.因此,在低于居里点温度确定的本征剩磁及相应的古地磁数据将能反映特定的地质意义.由风火山白垩系古地磁数据可见,青藏高原巴颜喀拉地体白垩系以后仍然存在着较大规模的北向移动.  相似文献   

青藏高原东北部尕海湖沉积物中正构烷烃及其氢同位素组成与有机质源指示意义     

段毅  吴应忠  赵阳 《地质学报》2016,90(5):1030-1039

系统采集了位于青藏高原东北部的尕海湖淡水湖泊沉积物,对沉积物中正构烷烃及其氢同位素进行了分析,研究了沉积物中正构烷烃及其氢同位素组成,探讨了它们的来源。研究结果表明,尕海湖沉积物中正构烷烃分布反映了它们来自水生和陆生植物。尕海湖沉积正构烷烃氢同位素组成平均值为-221.9‰~-190.5‰。C_(21)~C_(33)奇碳数正构烷烃δD值明显地将样品划分为两种类型。类型Ⅰ样品的C_(21)~C_(33)奇碳数正构烷烃平均δD值明显地高于类型Ⅱ样品。类型Ⅰ沉积正构烷烃δD值分布特征反映了它们主要来自尕海湖水生植物;类型Ⅱ沉积物中正构烷烃δD值特征指示了它们主要来自研究区陆生草本植物。提出了具有δD值低、丰度高和CPI值低的中等链长正构烷烃起源于改造陆源草本植物的细菌。研究成果证实了沉积正构烷烃δD值可以作为指示有机质源的地球化学指标。  相似文献   

青藏高原碰撞造山带：I.主碰撞造山成矿作用   总被引：10，自引：1，他引：10  

侯增谦  杨竹森  徐文艺  莫宣学  丁林  高永丰  董方浏  李光明  曲晓明  李光明  赵志丹  江思宏  孟祥金  李振清  秦克章  杨志明 《矿床地质》2006,25(4):337-358

大陆碰撞与成矿作用是当代成矿学研究的重要前沿。与板块构造成矿作用研究相比,大陆碰撞造山带的成矿作用研究则明显薄弱。文章以青藏高原主碰撞带为对象,研究了印度—亚洲大陆主碰撞过程与区域成矿作用的耦合关系,并初步建立了主碰撞造山成矿模型。研究表明,印度—亚洲大陆主碰撞始于65Ma,延续至41Ma,形成了以藏南前陆冲断带、冈底斯主碰撞构造_岩浆带和藏北陆内褶皱_逆冲带为特征的青藏高原碰撞造山带主体。伴随陆_陆碰撞,在冈底斯带相继发育①壳源白云母花岗岩_钾质钙碱性花岗岩组合(66～50Ma)、② εNd花岗岩_辉长岩组合(52～47Ma)和③幔源玄武质次火山岩_辉绿岩脉组合(42Ma),以及大面积分布的巨厚(5000m)的林子宗火山岩系(65～43Ma),反映深部相继发生大陆碰撞和板片陡深俯冲(65～52Ma)→板片断离(52～42Ma)→板片低角度俯冲(<40Ma)等重要过程。在主碰撞期,初步识别出4个重要的成矿事件:①与壳源花岗岩有关的Sn、稀有金属成矿事件,在藏东滇西形成腾冲Sn、稀有金属矿集区;②与壳/幔花岗岩有关的Cu_Au_Mo成矿事件,在冈底斯南缘形成长达百余公里的Cu_Au矿化带;③与碰撞造山有关的剪切带型Au成矿事件,沿雅鲁藏布江缝合带分布,形成具有较大成矿潜力的Au矿化带;④与挤压抬升有关的Cu_Au成矿事件,形成以雄村大型铜金矿为代表的斑岩型/浅成低温复合型Cu_Au矿床。在综合研究基础上,初步建立了大陆主碰撞造山区域成矿模型。  相似文献   

青藏高原东北缘深地震测深研究成果回顾   总被引：5，自引：1，他引：5       下载免费PDF全文

周民都 《地震工程学报》2006,28(2):189-191

本文回顾了在青藏高原东北缘(32°-40°N,100°-108°E)地区深地震测深研究的主要成果,给出了这一地区地壳中地震波速度结构的特征和莫霍面的形态。  相似文献