The hydrogeology of crystalline aquifers in northern Nigeria and geophysical techniques used in their exploration
The hydrogeology of crystalline aquifers in northern Nigeria and geophysical techniques used in their exploration
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尼日利亚北部结晶含水层的水文地质及其勘探中使用的地球物理技术
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
C. R. C. Jones
中科院分区：
文献类型：
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作者：
J. Hazell;C. R. Cratchley;C. R. C. Jones
上世纪80年代地下水十年期间，尼日利亚北部大量农村供水钻孔的选址和钻探，提供了大量关于基底风化层水文地质的数据，并导致了定位含水层的新技术的发展。综述了包奇州、卡诺州和索科托州的风化层含水层特征及其对地质和环境的依赖性，特别强调了岩性、风化模式和压裂。比容与岩性和风化等级有关；旱季水位和成功井的出现频率与岩性有关。卡诺州的水质数据显示硝酸盐浓度很高。钻孔选址的过程从案头研究（记录和光解释）开始，然后对岩性、结构、水点、地形和土壤进行实地勘察。在目标区域进行电磁遍历和电阻率测深。利用计算模型图估计了40米和20米线圈间距下的垂直到水平线圈（EM）响应的最大风化层厚度。在这些地点进行的电磁测深测量给出了表土电阻率，从而对其作为含水层的适用性进行了一些估计。此外，EM遍历仪还定位了陡倾断裂带、岩脉和伟晶岩，计算机控制的建模系统的结果有助于对这些断裂带的走向和倾角进行解释。
Abstract The large number of rural water supply boreholes sited and drilled in northern Nigeria during the ground water decade of the eighties has provided much data on the hydrogeology of the Basement regolith and has led to the development of new techniques in locating aquifers. Regolith aquifer characteristics and their dependence on geology and environment are reviewed with particular emphasis on lithology, weathering pattern and fracturing in Bauchi, Kano and Sokoto States. Specific capacity is shown to be related to both lithology and grade of weathering; dry season water levels and frequency of occurrence of successful holes are related to lithology. Water quality data for Kano State show some high nitrate concentrations. The process of borehole siting begins with desk study (records and photointerpretation), then field reconnaissance of lithology, structure, water points, topography and soils. EM traverses and resistivity soundings follow in targeted areas. Maximum regolith thicknesses are estimated from the vertical to horizontal coil (EM) response using computed model graphs for 40 m and 20 m coil spacings. VES measurements at these sites give regolith resistivities, hence some estimate of its suitability as an aquifer. In addition EM traverses have located steeply-dipping fracture zones, dykes and pegmatites and interpretation of these in terms of strike and dip has been aided by results from a computer-controlled modelling system.