喜马拉雅山脉中段土地覆被的垂直分异特征     

张镱锂  吴雪  郑度 《地理学报》2020,75(5):931-948

喜马拉雅山脉中段的珠穆朗玛峰等地,海拔高差巨大、生境复杂多变、土地覆被类型多样且植被垂直带谱完整,是全球范围内研究土地覆被垂直变化的理想场所。本文基于30 m空间分辨率的土地覆被数据（2010年）和DEM数据,在ArcGIS和Matlab平台的支持下,提出并运用脊线法、样带法和扇区法3种山地南北坡划分方法,研究了喜马拉雅山土地覆被垂直分布与结构差异。结果表明：① 山地土地覆被分布具有明确的垂直地带性结构特征,喜马拉雅中部土地覆被垂直带谱为南六北四式,土地覆被垂直带谱中具有人类活动的特点。② 南北坡之间的土地覆被垂直带谱差异明显,南坡土地覆被类型完整多样,北坡相对简单;对同类型土地覆被而言,南坡较北坡分布高程低、幅度宽。③ 依据各类型分布面积比随海拔变化情况,土地覆被类型在南北坡上的垂直分布可分为4种模式：冰川雪被、稀疏植被和草地为单峰分布型,裸地为南单峰北双峰分布型。④ 3种划分方法中,南坡的土地覆被垂直带结构具有相似性,而北坡的土地覆被垂直带结构存在差异,扇区法较好地反映了土地覆被自然分布格局。  相似文献   

青藏高原腹地各拉丹冬南北坡多年冻土考察初步结果     

刘广岳  邹德富  杨斌  杜二计  周华云  肖瑶  赵林  谭昌海  胡国杰  庞强强  王武  孙哲  朱小凡  殷秀峰  汪凌霄  李智斌  谢昌卫 《冰川冻土》2022,44(1):83-95

青藏高原唐古拉山南北两侧在地形地貌、地理和气候特征上存在显著差异,多年冻土的发育状况和特征也明显不同。受第二次青藏高原综合科学考察研究等项目资助,多年冻土对亚洲水塔的影响专题考察分队分别于2019年和2020年的10—11月对唐古拉山各拉丹冬南侧的色林错上游扎加藏布源区（简称“湖源区”）和北侧的长江上游沱沱河源区（简称“江源区”）进行了多年冻土野外考察。利用钻探、坑探、地球物理勘探等方法对多年冻土的分布边界、多年冻土剖面的地层、地下冰等特征进行了描述和取样,同步构建了多年冻土温度和活动层水热观测网络,为多年冻土对亚洲水塔影响的机理分析、数值模拟以及情景预估提供数据保障。对野外调查资料的初步分析认为,各拉丹冬南北两坡地层沉积类型和地下冰赋存状态存在明显差异,北坡多年冻土的热稳定性、地下冰含量、冰缘地貌类型多样性均高于南坡,但由于受到构造地热、河流融区等多种因素的影响,北坡的冻土分布形式更为复杂。江源区100 m钻孔剖面揭示了连续分布的、厚度大于50 m的地下冰;在该区域发现了多年生冻胀丘分布群,并利用钻探和地球物理勘探方法对该区域规模最大、结构最完整的冰核型冻胀丘进行了较为系统的勘察剖析。两次野外调查工作共采集钻孔岩心、表层土壤、冰水等各类样本近1.2万件,为后期区域冻土理化指标分析,冻土环境化学、古气候环境研究的开展奠定基础。  相似文献   

The evolution of zircon during low‐P partial melting of metapelitic rocks: theoretical predictions and a case study from Mt Stafford,central Australia     

WEI‐ Wang  E. Dunkley  G. L. Clarke  N. R. Daczko 《Journal of Metamorphic Geology》2014,32(8):791-808

Palaeoproterozoic metasedimentary migmatite reflects the highest temperature parts of a regional aureole at Mt Stafford, central Australia, comprising rocks that experienced 500–800 °C at ≈3 kbar. Whole‐rock major element concentrations are correlated with Zr content, psammitic compositions having nearly twice the Zr content of pelitic compositions. Zirconium is concentrated in mesosome compared with leucosome. Zircon is largely detrital, mostly lacking any overgrowth contemporary with migmatite formation. Comparatively small proportions of micro‐zircon (<10 μm) in sub‐solidus rocks are mostly hosted by quartz and plagioclase. Much higher proportions (three to five times) of micro‐zircon in migmatite are hosted by prograde K‐feldspar, cordierite and biotite. T–X and P–T NCKFMASHTZr pseudosections constructed using thermocalc model the distribution of Zr between solid and silicate liquid phases. Half of the detrital zircon (~100 ppm Zr) is predicted to be dissolved into silicate liquid at ≈800 °C and all dissolved by 850 °C, if all zircon is involved in the equilibration volume. Melt segregation at relatively low temperature is predicted to enrich the residuum in Zr, consistent with the observed distribution of Zr between mesosome and leucosome. The limited development of metamorphic zircon rims or overgrowths at Mt Stafford is explained by three concurrent processes: (i) Zr liberated during prograde metamorphism formed micro‐zircon, rather than following the prediction that Zr will partition into silicate liquid; (ii) some detrital zircon was probably armoured by other rock‐forming minerals, reducing Zr content in the effective bulk rock composition; and (iii) small proportions of melt loss during migmatization removed Zr that otherwise would have been available to form metamorphic rims.  相似文献   

大瑞铁路高黎贡山越岭段主要工程地质问题与地质选线   总被引：2，自引：1，他引：1  

李光伟  杜宇本  蒋良文  郭长宝  沈维  刘筱怡 《地质力学学报》2015,21(1):73-86

在野外地质调查、钻探、地应力测量和室内测试分析的基础上,对大瑞铁路高黎贡山越岭段规划设计中可能遇到的高地温、高地应力、活动断裂断错、岩爆、涌水突泥、软岩大变形和边坡稳定性等主要工程地质问题进行了论述,认为高地温和热害是制约高黎贡山深埋隧道段建设的关键因素。根据地热钻探、测试资料分析,该区的地热分布受断裂构造控制明显,黄草坝断裂具有阻水隔热的工程地质特性。对比分析认为,C12K方案(34.5 km越岭长隧道方案)位于黄草坝阻水隔热断层之南,通道内相对低温,且在隧道口处避让了古滑坡等不利工程地质问题,在众多比选方案中工程地质条件较好。调查研究结果对大瑞铁路全线贯通具有重要意义。  相似文献   

黄山不同高度雨滴谱的演变特征   总被引：1，自引：0，他引：1       下载免费PDF全文

陈聪  银燕  陈宝君 《大气科学学报》2015,38(3):388-395

选取2011年6月黄山地区一次降水过程,利用测得的雨滴谱资料对不同高度上降水微物理量及雨滴谱分布特征进行分析,并讨论其中的差异。结果表明:此次降水较强,各直径微物理量在山腰最大、山底次之、山顶最小;山腰的雨强最大,而山顶数浓度最大。在雨滴谱分布中,小于1mm的雨滴数密度是山顶大于山腰大于山底,这与小雨滴的蒸发和碰并有关;大于1.5 mm的雨滴数密度则是山腰大于山顶和山底,这可能与地形抬升使得云系加强有关。由各微物理量的时间序列可将降水过程分为两个阶段,第一阶段各微物理量值明显大于第二阶段,其中第一阶段的降水量约为第二阶段的3倍。雨强与雷达反射率、数浓度、最大直径近似成幂函数关系,其中雨强与雷达反射率相关性最好。  相似文献   

东昆仑西端布喀达坂峰地区二叠纪孢粉型化石的发现     

宋泰钟  尹磊明  欧阳舒  王秉璋  王瑾  叶占福  宋生春 《地层学杂志》2004,28(2):142-147

在东昆仑西端布喀达坂峰地区二叠纪地层中首次发现陆相孢粉与海相疑源类化石一起保存的孢粉—疑源类化石组合。经对两个样品较为丰富的孢粉型化石研究后发现,上部组合以裸子植物花粉占优势,双囊无肋花粉最多,可与塔里木盆地的卡伦达尔组的孢粉组合做粗略的比较,但组合中出现了时代偏晚的Ephedripites及Taeniae-sporites,因此,研究区马尔争组中段复理石地层的时代当为中二叠世—晚二叠世。  相似文献   

Palaeoproterozoic mid‐basin inversion in the northern Mt Isa terrane,Queensland     

P. G. Betts 《Australian Journal of Earth Sciences》2013,60(5):735-748

The Mellish Park Syncline is located in the northern part of the Mt Isa terrane. It has an axial trace that transects the remnants of the unconformity‐bounded Palaeoproterozoic Leichhardt and Isa Superbasins. The syncline is separated into a lower and upper component based upon variation in fold geometry across the basin‐bounding unconformity. The lower syncline, in the Leichhardt Superbasin, is tight and has an inclined west‐dipping axial plane. The upper syncline, in the Isa Superbasin, is open and upright. The geometry of the lower syncline is a consequence of a period of shortening and basin inversion which post‐dated the Leichhardt Rift Event (ca 1780–1740 Ma) and pre‐dated the Mt Isa Rift Event (ca 1710–1655 Ma), forming an open and upright north‐oriented syncline. Subsequent southeast tilting and half‐graben development during the Mt Isa Rift Event resulted in the lower syncline being tilted into its inclined geometry. Sequences of the Isa Superbasin were then deposited onto the eroded syncline. The geometry of the upper syncline reflects regional east‐west shortening during the Isan Orogeny (ca 1590–1500 Ma). The position of the upper syncline was largely controlled by the pre‐existing lower syncline. At this time the lower syncline was reactivated and tightened by flexural slip folding.  相似文献   

A newly defined Late Ordovician magmatic‐thermal event in the Mt Painter Province,northern Flinders Ranges,South Australia     

M. A. Elburg  P. D. Bons  J. Foden  J. Brugger 《Australian Journal of Earth Sciences》2013,60(4):611-631

Magmatism,metamorphism and metasomatism in the Palaeoproterozoic‐Mesoproterozoic Mt Painter Inlier and overlying Neoproterozoic Adelaidean rocks in the northern Flinders Ranges (South Australia) have previously been interpreted as resulting from the ca 500 Ma Delamerian Orogeny. New Rb–Sr, Sm–Nd and U–Pb data, as well as structural analysis,indicate that the area also experienced a second thermal event in the Late Ordovician (ca 440 Ma). The Delamerian Orogeny resulted in large‐scale folding, prograde metamorphism and minor magmatic activity in the form of a small volume of pegmatites and leucogranites. The Late Ordovician event produced larger volumes of granite (the British Empire Granite in the core of the inlier) and these show Nd isotopic evidence for a mantle component. The high‐temperature stage of this magmatic‐hydrothermal event also gave rise to unusual diopside‐titanite veins and the primary uranium mineralisation in the basement, of which the remobilisation was younger than 3.5 Ma. It is possible that parts of the Mt Gee quartz‐hematite epithermal system developed during the waning stages of the Late Ordovician event. We suggest that the Ordovician hydrothermal system was also the cause of the commonly observed retrogression of Delamerian metamorphic minerals (cordierite, andalusite) and the widespread development of actinolite, scapolite, tremolite and magnetite in the cover sequences. Deformation during the Late Ordovician was brittle. The recognition of the Late Ordovician magmatic‐hydrothermal event in the Mt Painter Province might help to link the tectonic evolution of central Australia and the southeast Australian Lachlan Fold Belt.  相似文献   

Comparison of the ‘strike‐slip’ versus the ‘episodic rift‐sag’ models for the origin of the Isa Superbasin     

P. G. Betts  G. S. Lister 《Australian Journal of Earth Sciences》2013,60(2):265-280

In this paper we assess two competing tectonic models for the development of the Isa Superbasin (ca 1725–1590 Ma) in the Western Fold Belt of the Mt Isa terrane. In the ‘episodic rift‐sag’ tectonic model the basin architecture is envisaged as similar to that of a Basin and Range province characterised by widespread half‐graben development. According to this model, the Isa Superbasin evolved during three stages of the Mt Isa Rift Event. Stage I involved intracontinental extension, half‐graben development, the emergence of fault scarps and tilt‐blocks, and bimodal volcanism. Stage II involved episodic rifting and sag during intervening periods of tectonic quiescence. Stage III was dominated by thermal relaxation of the lithosphere with transient episodes of extension. Sedimentation was controlled by the development of arrays of half‐grabens bounded by intrabasinal transverse or transfer faults. The competing ‘strike‐slip’ model was developed for the Gun Supersequence stratigraphic interval of the Isa Superbasin (during stage II and the beginning of stage III). According to this model, sinistral movements along north‐northeast‐orientated strike‐slip faults took place, with oblique movements along northwest‐orientated faults. This resulted in the deposition of southeast‐thickening ramp sequences with local sub‐basin depocentres forming to the west and north of north‐northeast‐ and northwest‐trending faults, respectively. It is proposed that dilation zones focused magmatism (e.g. Sybella Granite) and transfer of strike‐slip movement resulted in transient uplift along the western margin of the Mt Gordon Arch. Our analysis supports the ‘episodic rift‐sag’ model. We find that the inferred architecture for the strike‐slip model correlates poorly with the observed structural elements. Interpretation is made difficult because there has been significant modification and reorientation of fault geometry during the Isan Orogeny and these effects need to be removed before any assertion as to the basin structure is made. Strike‐slip faulting does not explain the regional‐scale pattern of basin subsidence. The ‘episodic rift‐sag’ model explains the macroscopic geometry of the Isa Superbasin and is consistent with the detailed sedimentological analysis of basin facies architecture, and the structural history and geometry.  相似文献   

Trace‐element signatures of apatites in granitoids from the Mt Isa Inlier,northwestern Queensland     

E. A. Belousova  S. Walters  W. L. Griffin  S. Y. O'Reilly 《Australian Journal of Earth Sciences》2013,60(4):603-619

The concentrations of trace elements in apatite from granitoid rocks of the Mt Isa Inlier have been investigated using the laser‐ablation inductively coupled plasma‐mass spectrometry (ICP‐MS) microprobe. The results indicate that the distribution of trace elements (especially rare‐earth elements (REE), Sr, Y, Mn and Th) in apatite strongly reflects the chemical characteristics of the parental rock. The variations in the trace‐element concentrations of apatite are correlated with parameters such as the SiO₂ content, oxidation state of iron, total alkalis and the aluminium saturation index (ASI). The relative enrichment of Y, HREE and Mn and the relative depletion of Sr in the apatites studied reflect the degree of fractionation of the host granite. Apatites from strongly oxidised plutons tend to have higher concentrations of LREE relative to MREE. Manganese concentrations are higher in apatite from reduced granitoids because Mn²⁺substitutes directly for Ca²⁺. The La/Ce ratio of apatite is well‐correlated with the whole‐rock K²O and Na²O contents, as well as with the oxidation state and ASI. Because apatite trace‐element composition reflects the chemistry of the whole rock, it can be a useful indicator mineral for the recognition of mineralised granite suites, where particular mineralisation styles are associated with granitoids that have specific geochemical fingerprints.  相似文献