鄂北—豫南地区榴辉岩相岩石变质作用演化特征   总被引：4，自引：2，他引：4  

王晓燕 《岩石学报》1997,13(3):369-379

鄂北－豫南地区榴辉岩相变质岩石类型多样，其野外产状和岩石化学特征反映了原地变质成因。根据区域地质及榴辉岩相变质岩石的野外产状，结合榴辉岩中石榴石绿辉石的Ｆｅ２＋－Ｍｇ互换温度计所计算出的峰期变质温度，将本区榴辉岩分为两类，一类为中温榴辉岩，产于晚太古界—早元古界大别群，为Ｂ类榴辉岩，由绿帘角闪岩相岩石进变质形成。榴辉岩相变质作用分为两阶段，首先为柯石英榴辉岩相阶段，其峰期变质条件为Ｔ＝６００℃～７００℃，Ｐ＝２．７～３．０ＧＰａ，然后近等温降压，出现蓝闪石等含水矿物，为蓝闪石榴辉岩相阶段，此时水活度在榴辉岩相变质过程中起着重要作用；另一类为低温榴辉岩，产于中元古界七角山组，为Ｃ类榴辉岩，由蓝片岩相岩石进变质形成，其峰期变质条件为Ｔ＝４９０℃～５６０℃，Ｐ＜１．５ＧＰａ。中温榴辉岩与低温榴辉岩具有不同的变质作用特征。最后讨论了本区高压变质带的成因演化。  相似文献   

矿产开发与环境保护   总被引：4，自引：0，他引：4  

郭真 《吉林地质》1997,16(2):11-16

通过国内多个矿区实例，较系统地叙述了矿产资源开发导致的生态环境破坏和污染状况。表明矿产开发中对环境污染的途径包括河流、土壤、等。最后简要介绍了国内、国外几种对采矿污染比较有效的防治措施。  相似文献   

Parameters of Land-Surface Processes for Gobi in North-West China   总被引：1，自引：0，他引：1  

Zhang Qiang  Huang Ronghui 《Boundary-Layer Meteorology》2004,110(3):471-478

Using data from the intensive observation period (May–June 2000) of the NWC-ALIEX (The Field Experiment on Interaction between Land and Atmosphere in Arid Region of North-west China), the characteristics and mechanisms of some key land-surface process over Gobi in a typical arid region of north-west China are analyzed and several parameters of land-surface processes are calculated. The weighted mean of the surface albedo over a typical arid region of the Dunhuang Gobi is calculated using the relative reflection as a weighting factor, and its value is 0.255 ± 0.021. After removing the influence of precipitation, the mean soil heat capacity over a typical arid region of the Dunhuang Gobi is 1.12 × 10⁶ J m^-3 K^-1,which is smaller than that observed in the Heihe (China) River basin Field Experiment (HEIFE). The mean soil heat diffusivity and conductivity are about half of those observed in HEIFE.  相似文献   

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface     

LIU Shu-hua~ 《地球科学进展》2004,(Z1)

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth‘s surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...  相似文献   

1948—2001年全球大尺度区域 6～8月降水的长期变化     

黄先香  施能  顾骏强  高鸿 《地球科学进展》2004,19(5):824-830

研究了1948-2001年南、北半球及欧亚大陆、非洲大陆、澳洲大陆、北美大陆、南美大陆、南极大陆和中国 7个大尺度区域 6～8月降水的长期趋势变化和年代际变化。结果表明，南、北半球 6～8月的降水都为负趋势，但南半球降水的负趋势在统计上不显著。在54年的时间段内，南半球 6～8月降水的递减速度为 0．12 mm／a，仅为北半球同期降水减幅（0．24 mm／a）的一半。南、北半球 6～8月降水量年代际尺度的振荡都非常明显，但是，南、北半球年代际变化的特征明显不同。目前北半球仍是在少雨时间段，而南半球处在降水量正常或多雨的时间段。分析还表明，非洲大陆 6～ 8月降水的年代际特征最明显，降水的负趋势也最为显著；欧亚大陆 6～8月降水也有着明显的年代际变化与明显的负趋势变化；澳洲大陆 6～8月降水的年际变化明显，年代际变化相对来说要小得多；北美大陆 6～8月降水的年际变化明显，但无明显的趋势变化。此外，分析了大尺度区域 6～ 8月降水之间的相关关系，发现部分区域大尺度降水量之间有明显的联系；分析了中国夏季降水的长期变化，发现中国夏季降水的年代际变化明显，但无明显的趋势变化。  相似文献   

The Rotational Structure along the Eastern Segment of the Altyn Tagh Fault and Its Implications in Dynamics     

Wang Ping 《中国地震研究》2004,18(4):327-336

As a result of the left-lateral strike-slipping of the Altyn Tagh fault in Neotectonic period, a contra-rotational structure, namely the Zhaobishan vortex structure, has developed at the juncture of the main Altyn Tagh fault and the northern fringe fault of the Qilian Mountains.Preliminary analysis on the deformation and evolution of the Zhaobishan vortex structure. In combination with the previous data, suggests that the tectonic transform between the Altyn Tagh fault and the northern fringe fault of the Qilian Mountains attributes to the deformation of the rotational structure. The existence of a series of rotational structures along the Altyn Tagh fault and on the northeastern edge of the Qinghai-Xizang(Tibet) plateau indicate that as the substance in the northern Qinghal-Xizang (Tibet) plateau moves clockwise around the eastern tectonic knot of the Himalayas, rotational structures become the principal mode on the northern marginal zone of the Plateau of transforming and absorbing tectonic deformation.  相似文献   

天山山区近40a年降水变化特征与南、北疆的比较   总被引：24，自引：2，他引：24       下载免费PDF全文

袁玉江  何清  喻树龙 《气象科学》2004,24(2):220-226

本文分析了天山山区近40 a来年降水变化的基本特征，并与南疆、北疆进行了比较，所得的主要结果如下：(1)天山山区在年降水量干湿变化阶段上与北疆的相似性强于南疆。(2)年降水量的空间分布的同步变化性以北疆为最好，南疆最差，天山山区居中，而年降水量的空间分布的反向变化性，以天山山区为最大，北疆最小，南疆居中。(3)天山山区与南疆从60年代到90年代，年降水均表现出了持续的增加的趋势，北疆年降水从60年代到90年代，除70年代外，不断增多。  相似文献   

Assessing land use/cover changes: a nationwide multidate spatial database for Mexico     

Jean-Franois Mas  Alejandro Velzquez  Jos Reyes Díaz-Gallegos  Rafael Mayorga-Saucedo  Camilo Alcntara  Gerardo Bocco  Rutilio Castro  Tania Fernndez  Azucena Prez-Vega 《International Journal of Applied Earth Observation and Geoinformation》2004,5(4):249-261

A nationwide multidate GIS database was generated in order to carry out the quantification and spatial characterization of land use/cover changes (LUCC) in Mexico. Existing cartography on land use/cover at a 1:250,000 scale was revised to select compatible inputs regarding the scale, the classification scheme and the mapping method. Digital maps from three different dates (the late 1970s, 1993 and 2000) were revised, evaluated, corrected and integrated into a GIS database. In order to improve the reliability of the database, an attempt was made to assess the accuracy of the digitalisation procedure and to detect and correct unlikely changes due to thematic errors in the maps. Digital maps were overlaid in order to generate LUCC maps, transition matrices and to calculate rates of conversion. Based upon this database, rates of deforestation between 1976 and 2000 were evaluated as 0.25 and 0.76% per year for temperate and tropical forests, respectively.  相似文献   

粤北笋洞花岗岩的形成时代、地球化学特征与成因   总被引：25，自引：10，他引：25  

凌洪飞沈渭洲  邓平蒋少涌  高剑峰叶海敏濮巍  谭正中 《岩石学报》2004,20(3):413-424

笋洞花岗岩体是粤北贵东复式花岗岩体的一个重要组成部分。锆石U-Pb年龄为189.1±0.7Ma,是燕山早期岩浆活动产物。该岩体的主要元素显示富硅、富碱、强过铝质和低 CaO/Na_2O比值等特征;微量元素方面,富集Rb,Th,U,Ce,Sm,Y,亏损 Ba,Sr,P,Ti;LREE轻微富集(LREE/HREE=6.6～8.8,(La/Yb)_N=6.44～10.74),Eu亏损明显(δEu=0.14～0.31);它具有低的ε_(Nd)(t)(-11.4～-9.3),高的δ~(18)O(10.2～12.7‰)、(~(87)Sr/~(86)Sr);(0.72949～0.74923)、~(206)Pb/~(204)Pb(18.180～18.488)、~(207)Pb/~(204)Pb(15.655～15.661)和古老的Nd模式年龄(1762～1933Ma)。上述这些特征表明,笋洞岩体属于典型的壳源型花岗岩,是在地壳伸展-减薄的构造背景下,通过以泥质成分为主的古-中元古代变质沉积岩部分熔融的方式形成。  相似文献   

Estimating coefficients of volume compressibility from compression of strata and piezometric changes in a multiaquifer system in west Taiwan     

Chih-Hsi Liu  Yii-Wen Pan  Wei-Cha Hung 《Engineering Geology》2004,75(1):33-47

This paper estimates the coefficients of volume compressibility from variation in compressible layer thickness and changes in piezometric heads by using detail ground surface surveys and a multilayer monitoring well at a selected site (Shigang) within the Choshui River alluvial fan in west Taiwan. The paper integrates various types of in situ monitoring tools, including leveling surveys, continuous global position system (GPS) stations, multilevel layer compression and groundwater pressure head-monitoring wells, to investigate the situation and progress of the subsidence problem in the region. The results from the cross-analyses of the measured data show that surface settlement caused by the compression of strata is between the depths of 60 and 210 m where the clayey stratum within 120-180 m was most pronounced and contributes up to 53% of the total compression. The results indicate that the clayey stratum is under normal consolidation. The results also reflect the fact that 20% of settlement contribution comes from the sandy stratum within 90-120 m; the elasto-plastic behavior of this sandy stratum is clear. The coefficients of volume compressibility of the clayey and sandy stratum analysed from the stratum's compression records; they were 6.38×10⁻⁸ and 5.71×10⁻⁹ m²/N, respectively. Ultimately, this parameter estimation would permit to control and predict land subsidence based on change in pressure head which are related to groundwater extraction.  相似文献