青海省都兰县一棵松铅-锌-银矿多元成矿信息与找矿方向     

陆智平  李发明 《矿产与地质》2006,20(4):465-468

阐述了一棵松铅-锌-银矿床的矿区地质特征，分析了在该矿区利用多元成矿信息找矿的有效性。着重对矿区构造的控矿作用、矿区地球化学特征和地球物理特征与矿化的关系进行较深入的分析。研究认为，在近EW向断裂构造两测与不同方向断裂带叠加的部位，且物探、化探异常互为套合的地段，是寻找和验证新的铅-锌-银矿体的有利部位。  相似文献   

腰椎骨髓逆转换的MR表现及相关常见病因分析     

钟洪波  李晓阳  李骥  李光民 《CT理论与应用研究》2006,15(1):11-14

目的研究腰椎骨髓逆转换MR表现及其常见病因的鉴别诊断。方法搜集唐山人民医院行腰椎MR检查并出现骨髓逆转换征象住院患者14名的临床、实验室及影像资料。其中腰椎转移瘤6例,多发骨髓瘤2例,骨髓纤维化1例,恶性肿瘤化疗后5例。结果5例腰椎椎体表现为于T1WI呈均匀一致低信号,于T2WI呈均匀一致高信号。9例于T1WI表现等信号背景下可见多个斑片状、斑点状低信号,于T2WI呈等信号背景下可见多个斑片状、斑点状高信号,数目不等,散在分布。其中3例附件受累,1例椎旁形成肿块,1例硬膜外形成肿块。结论腰椎转移瘤、多发骨髓瘤、骨髓纤维化、恶性肿瘤化疗后腰椎等疾病均可发生骨髓逆转换,其MR表现缺乏特异性,诊断需结合临床、实验室及其他检查才能明确诊断。  相似文献   

Chemistry of the Shiant Isles Main Sill, NW Scotland, and Wider Implications for the Petrogenesis of Mafic Sills   总被引：3，自引：0，他引：3  

GIBB  F. G. F.; HENDERSON  C. M. B. 《Journal of Petrology》2006,47(1):191-230

Major and trace element data for the Tertiary, Shiant IslesMain Sill, NW Scotland, are used to discuss its complex internaldifferentiation. Vertical sections through the sill exhibitsharp breaks in chemistry that coincide with changes in texture,grain size and mineralogy. These breaks are paired, top andbottom, and correspond to the boundaries of intrusive units,confirming a four-phase multiple-intrusion model based on fieldrelations, petrography, mineralogy and isotopes. Whole-rockchemistry is consistent with this model and necessitates onlyminor revisions to the intrusive and differentiation mechanismspreviously proposed. The rocks contain strongly zoned minerals(e.g. olivine Fo_70–5, clinopyroxene Mg# = 75–5,plagioclase An_75–5) indicating almost perfect fractionalcrystallization, but whole-rock compositions do not show suchextreme variations. Thus, while residual liquids became highlyevolved in situ, they mainly became trapped within the crystalnetwork and did not undergo wholesale inward migration. Someinward (mainly upward) concentration of residual liquids didoccur to form a ‘sandwich horizon’, but the morevolatile-rich, late-stage liquids that did not crystallize insitu appear to have migrated to higher levels in the sill toform pegmatitic horizons. Parental liquid compositions are modelledfor the intrusive units and it is concluded that the originalparent magma formed by partial melting of upper mantle thatwas more depleted in LREE than the sources of most ScottishTertiary basaltic rocks. Incompatible trace elements in thepicrodolerite–crinanite intrusive unit support isotopeevidence that its parent magma was contaminated by crustal material.Attempts to reconcile the chemical characteristics of the sillwith a recently proposed petrogenetic model based on a singleintrusion of magma differentiated by novel, but controversial,processes fail comprehensively. It is predicted that the complexpetrogenetic history of the Shiant Isles sill is not unusualand could become the model for other large (>50 m thick)sills. KEY WORDS: alkali basalt; differentiation; geochemistry; multiple intrusion; Shiant Isles; sill  相似文献   

基于漏检概率的RAIM可用性分析方法   总被引：9，自引：2，他引：9  

陈金平  周建华唐波 《测绘学院学报》2005,22(1):8-10

描述了通常基于单故障假设相应的HPL，或VPL，的计算模型，针对WAAS用户在应用RAIM时需要顾及多故障的情况，提出了基于漏检概率的可用性分析方法，并通过模拟计算得到一些结论。  相似文献   

井群出水量减少原因分析及治理--以北京某应急备用地下水源地为例     

查恩来  张秋建 《水文地质工程地质》2005,32(2):115-117

近来,为缓解北京市日趋紧张的供水情况,需启用1995年建成的北京某应急备用地下水源地。该水源地建有30眼水井,属第四系河旁非承压含水层,当时静水位埋深为4m,单井平均出水量超过4000m3h。近年来由于各种原因,尤其是2003年该水源井出水量大幅减少的主要原因是含铁碳质化合物附着对井壁的堵塞。针对这一情况,通过试验确定了以强力正反冲洗活塞洗井工艺为核心的复合洗井方案,对17眼水井实施洗井处理,使井群出水量恢复到了建井初期的水平,取得了良好的效果。  相似文献   

柴北缘—东昆仑地区造山型金矿床的Ar-Ar测年及其地质意义   总被引：20，自引：7，他引：20  

张德全  党兴彦  佘宏全  李大新  丰成友  李进文 《矿床地质》2005,24(2):87-98

通过对柴北缘-东昆仑地区一批金矿床中绢云母的Ar-Ar测年，确定金矿床形成于晚加里东期和晚华力西-印支期，是该区加里东和晚华力西-印支复合造山过程的产物，是典型的造山型金矿床。金成矿作用主要发生在碰撞造山过程的晚期。金成矿与柴北缘-东昆仑地区的复合造山作用在时空上的“构造迁移”相一致。  相似文献   

SMALL‐SCALE INDUSTRY AS A SPONGE? EMPIRICAL SURVEY IN THE CENTRAL REGION,GHANA     

John V. Mensah 《Singapore journal of tropical geography》2005,26(2):212-226

It has been posited that small‐scale industry – businesses with less than 30 workers – provides a large share of employment and income in Ghana. This paper examines the proposition that while such enterprises in the informal sector are said to act as a sponge to soak up surplus labour in marginal activities, they are unprofitable. Using data from a survey in 1998 of 175 micro and small‐scale enterprises in the Central Region of Ghana, the paper also confirms problematic aspects of employment in this sector including the lack of formal contracts, irregular pay, low remuneration, non‐existent social protection and only marginal employment growth. The implication is that the small‐scale industry sector is not economically sustainable in its present form in Ghana.  相似文献   

Rigorous redatuming     

W. A. Mulder 《Geophysical Journal International》2005,161(2):401-415

  相似文献   

拉萨河流域近50 年来径流变化趋势分析   总被引：10，自引：2，他引：10  

蔺学东  张镱锂  姚治君  巩同梁  王宏  刘林山 《地理科学进展》2007,26(3):58-67

以拉萨水文站以上流域为研究区, 基于拉萨水文站和唐加水文站的水文实测数据和当雄 县等3 个气象站的气候观测数据, 统计分析了1956~2003 年研究区径流的年内、年际变化, 利用 Mann- Kendall 趋势分析法和Pettitt 变点检验法分析了拉萨河流域径流的变化特征, 采用多元回 归方法分析了气候因素( 气温、降水) 对径流变化的影响。结果表明: ( 1) 研究时段内, 径流年际变 化波动较大, 在1970 年前后径流发生了较大的突变, 呈现出明显的增加趋势, 尤以近20 年来的 趋势最大; 月均径流的年际变化中, 有增加趋势的主要分布在冬半年( 11～4 月) 和夏半年的个别 月份( 5、7、9 月) ; ( 2) 流域内气候变化趋势与径流变化趋势基本一致, 但不同月/年均径流受不同 气候因素影响, 主要表现在年平均尺度上受降水影响较大, 在月平均尺度上, 夏半年径流增加趋 势受降水增加影响较大, 而冬半年径流变化则主要与气温有较显著相关性, 其主要原因可能是全 球变暖导致冰川融水增加。  相似文献   

Uncertainty and multiple objective calibration in regional water balance modelling: case study in 320 Austrian catchments   总被引：2，自引：0，他引：2  

J. Parajka  R. Merz  G. Blöschl 《水文研究》2007,21(4):435-446

We examine the value of additional information in multiple objective calibration in terms of model performance and parameter uncertainty. We calibrate and validate a semi‐distributed conceptual catchment model for two 11‐year periods in 320 Austrian catchments and test three approaches of parameter calibration: (a) traditional single objective calibration (SINGLE) on daily runoff; (b) multiple objective calibration (MULTI) using daily runoff and snow cover data; (c) multiple objective calibration (APRIORI) that incorporates an a priori expert guess about the parameter distribution as additional information to runoff and snow cover data. Results indicate that the MULTI approach performs slightly poorer than the SINGLE approach in terms of runoff simulations, but significantly better in terms of snow cover simulations. The APRIORI approach is essentially as good as the SINGLE approach in terms of runoff simulations but is slightly poorer than the MULTI approach in terms of snow cover simulations. An analysis of the parameter uncertainty indicates that the MULTI approach significantly decreases the uncertainty of the model parameters related to snow processes but does not decrease the uncertainty of other model parameters as compared to the SINGLE case. The APRIORI approach tends to decrease the uncertainty of all model parameters as compared to the SINGLE case. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献