浙东南碰撞造山带的岩石磁组构及其构造意义   总被引：3，自引：1，他引：3       下载免费PDF全文

谈晓冬  江新华 《地球物理学报》1995,38(6):806-814

对浙江东南碰撞造山带龙泉等地的岩石磁组构测试，显示了普遍具优势取向的最小磁化率主轴方向，由此所揭示的ＮＷ－ＳＥ方向的主压应力与侏罗纪以后该地区的推覆构造所揭示的主压应力方向一致．结合已发表的邻近地区的古地磁、同位素年龄等资料，认为该地区应属中生代碰撞造山带，龙泉群的变质年龄也与此相当．  相似文献   

台风影响期间珠江三角洲局地强风暴和大暴雨发生的环境条件   总被引：4，自引：0，他引：4  

王沛霖 《热带气象学报》1995,11(4):375-378

采用１９７６－１９８３年６－８月珠江三角洲地区受台风影响期间区内各站逐日的强风暴和降水资料以及广泛站的探空资料，用相关对比度分析方法，对台风环流中的珠江三角洲局地强风暴和大暴雨发生的环境条件进行统计诊断，得出台风影响珠江三角洲时这两种强天气发生的有利的环境条件，并发现二者在气压、风速、层结稳定度和中下层位势不稳定等方面显著不同。  相似文献   

6月份格陵兰海冰异常对黄河中上游7月份旱涝的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

胡增臻 《应用气象学报》1995,6(3):366-372

通过北极4个区的海水DQ%指数和全国160站7月份降水关系的诊断分析指出，6月份格陵兰海冰异常与黄河中上游7月份旱涝存在着明显的联系，6月份格陵兰海冰少(多)时，黄河中上游7月份易涝（旱）。产生这种联系的物理机制是6月份格陵兰海冰异常影响7月份欧亚大气环流，导致黄河中上游7月份降水产生异常。通过对相关场进行显著性检验，确认了6月份格陵兰海冰异常与黄河中上游7月份旱涝联系在统计上的可靠性。同时发现，有时随机数序列与气象要素场的相关场会达到很高的显著水平，而且这种相关场中的显著相关区的分布并不是杂乱无章的，而是成片分布的。这项工作指出了把对相关场的显著性检验与相关场成因的物理机制分析相结合的必要性。  相似文献   

中国东部新生代玄武岩中单斜辉石巨晶的主要特征及成因信息   总被引：7，自引：1，他引：7  

邱家骧  廖群安 《岩石矿物学杂志》1987,6(1):56-64

作者通过对我国东部新生代玄武岩中巨晶Cpx的109个样品的化学成分的统计、计算及投影,研究了Cpx巨晶的产状、物性及矿物化学的主要特征,并对其成因信息提出了自己的看法。Cpx巨晶的成分以A1_2O_3、A1~(v1)较高而Ti、Mg'中等为特征。但在“反应边”中,A1_2O_3、Na_2O、A1、A1~(v1)则明显降低。我国巨晶以普通辉石为主,而透辉石、次透辉石及顽透辉石少见。国内不同地区的Cpx巨晶成分也略有不同:华南区巨晶的Wo较高而A1_2O_3较低;华北区Fs、A1_2O_3较高;而东北区En较高而A1_2O_3中等。有关Cpx巨晶的成因信息,作者的观点是:(1)巨晶Cpx是寄主玄武岩浆在上地幔中结晶的产物,而不是地幔解体的捕虏晶。(2)我国巨晶Cpx的结晶温度是1021—1209℃,压力为1.4—3.2GPa,所以,Cpx巨晶的结晶深度为48—104Km。(3)我国东部新生代玄武岩均产于大陆板块内部,以碱性玄武岩成分为主,而拉斑玄武岩较少。  相似文献   

River channel adjustments downstream from channelization works in England and Wales   总被引：1，自引：0，他引：1  

Andrew Brookes 《地球表面变化过程与地形》1987,12(4):337-351

Relatively little attention has been given to river channel adjustments that occur downstream from channelization works. This study is concerned with the nature of channel adjustments downstream from a total of 46 channelization works located in low and high energy environments in England and Wales. Channel changes are identified principally by the method of field survey and by reconstructing the original positions of eroded beds and banks. Use is also made of maps, aerial photographs, and engineering drawings of different dates and the technique of space-for-time substitution is applied. Enlargement of channel cross-sections through erosion had occurred downstream from a variety of types, sizes, and dates of channelization works. The maximum increase of channel size was 153 per cent. Out of a total of 14 sites with enlarged channel cross-sections, seven had undergone a change of width only, at a further three width increased rather than depth, and at the remaining four sites depth increases were dominant. These sites all have relatively high stream powers. Factors causing spatial variation of erosion included tree roots locally binding bank sediments and the occurrence of bends. Planform change had taken place at only one site. A further three high stream power sites had downstream reaches incised into bedrock and therefore did not exhibit adjustment. Channel enlargement is explained in terms of increased flood flows downstream from channelization works causing higher stream velocities, which in turn cause erosion, thereby increasing channel width and/or depth. Examination of flow records for 35 stations revealed flood events which would formerly have spread overbank but are now confined by the channelization works and are therefore likely to alter downstream flows. At sites with downstream change it is proposed that the energy of increased flows was sufficient to exceed a threshold required for erosion of perimeter sediments. By contrast the absence of change at a majority of sites in low energy lowland areas could be a reflection of both the incompetence of increased flows to erode and resistance provided by perimeter sediments. Sites with erosion features appear not to have yet attained new equilibrium conditions.  相似文献   

Changing drainage patterns in a semi-arid area and their effects on groundwater resources     

Sally E. Sutton 《地球表面变化过程与地形》1987,12(5):567-570

The magnitude of groundwater resources is poorly correlated with surface catchment area in a group of wadi bottom alluvial aquifers in Northern Oman. It is suggested that this is due to progressive water gap captures across a limestone ridge.  相似文献   

滇东-黔西地区晚二叠世煤岩及煤层气储层物性分析   总被引：3，自引：0，他引：3  

顾成亮 《贵州地质》2001,18(3):163-167,148

本文以丰富的地质资料对滇东－黔西地区晚二叠世煤岩分布的割理（裂隙）,吸附、孔隙溶积、镜质组含量、含气性、灰分产率等进行了较为系统的研究,初步建立了煤炭与煤层气储层物性的关系,提出了镜质组含量的煤炭类型有较好的煤层气储集物性条件。  相似文献   

疏勒河流域中游生态环境变化及成因分析   总被引：7，自引：1，他引：6  

陈德华  刘少玉  王昭 《水文地质工程地质》2001,28(6):23-25

近三十年来,疏勒河流域中游地区生态环境不断恶化,主要表现为绿色生产严重退化,湿地面积缩小,盐碱地,沙地迅速增加。通过不同时段的遥感解译,分析了不同生态景观的定量变化及成因。恶劣的地理环境加上人类活动对水资源利用量的不断增加是造成该区生态环境日趋恶化的主要因素。保护地下水平衡和合理用水结构,实行水资源优化管理,提高水的利用率是社会经济,环境可持续发展的有力保证。  相似文献   

Measurements of Trace Gases in the Inflow of South China Sea Background Air and Outflow of Regional Pollution at Tai O, Southern China     

T. Wang  H. Guo  D. R. Blake  Y. H. Kwok  I. J. Simpson  Y. S. Li 《Journal of Atmospheric Chemistry》2005,52(3):295-317

We present a 16-month record of ozone (O₃), carbon monoxide (CO), total reactive nitrogen (NO_y), sulphur dioxide (SO₂), methane (CH₄), C₂ – C₈ non-methane hydrocarbons (NMHCs), C₁ – C₂ halocarbons, and dimethyl sulfide (DMS) measured at a southern China coastal site. The study aimed to establish/update seasonal profiles of chemically active trace gases and pollution tracers in subtropical Asia and to characterize the composition of the `background' atmosphere over the South China Sea (SCS) and of pollution outflow from the industrialized Pearl River Delta (PRD) region and southern China. Most of the measured trace gases of anthropogenic origin exhibited a winter maximum and a summer minimum, while O₃ showed a maximum in autumn which is in contrast to the seasonal behavior of O₃ in rural eastern China and in many mid-latitude remote locations in the western Pacific. The data were segregated into two groups representing the SCS background air and the outflow of regional continental pollution (PRD plus southern China), based on CO mixing ratios and meteorological conditions. NMHCs and halocarbon data were further analyzed to examine the relationships between their variability and atmospheric lifetime and to elucidate the extent of atmospheric processing in the sampled air parcels. The trace gas variability (S) versus lifetime (τ) relationship, defined by the power law, S_lnx = Aτ^{− b}, (where X is the trace gas mixing ratio) gives a fit parameter A of 1.39 and exponent b of 0.42 for SCS air, and A of 2.86 and b of 0.31 for the regional continental air masses. An examination of ln[n-butane]/ln[ethane] versus ln[propane]/ln[ethane] indicates that their relative abundance was dominated by mixing as opposed to photochemistry in both SCS and regional outflow air masses. The very low ratios of ethyne/CO, propane/ethane and toluene/benzene suggest that the SCS air mass has undergone intense atmospheric processing since these gases were released into the atmosphere. Compared to the results from other polluted rural sites and from urban areas, the large values of these species in the outflow of PRD/southern China suggest source(s) emitting higher levels of ethyne, benzene, and toluene, relative to light alkanes. These chemical characteristics could be unique indicators of anthropogenic emissions from southern China.  相似文献   

肃南县羊露河上游似鞍山式铁矿地质特征及找矿方向   总被引：5，自引：0，他引：5  

张国成 《地质找矿论丛》2005,20(Z1):129-130

羊露河上游铁矿位于北祁连西段加里东褶皱带西段.铁矿体赋存于下元古界长城系上岩组含铁角闪片岩中,含矿层位严格受地层层位控制,矿石构造具有同生沉积特征,并显示了热液富集作用特点,具"似鞍山式"铁矿成因特征,矿石品位较高,盲矿体存在的可能性较大,因此具有重要的找矿意义.  相似文献