The influence of Cenozoic tectonics on the groundwater-production capacity of fractured zones: a case study in Sao Paulo, Brazil   总被引：1，自引：0，他引：1  

Amelia Fernandes  David L. Rudolph 《Hydrogeology Journal》2001,9(2):151-167

A new procedure is developed to correlate structural lineaments recognised through air-photo interpretation with subsurface fracture features that are associated with zones of high groundwater production in fractured-rock environments. The analysis approach is referred to as the homogeneous tectonic domain (HTD) method and involves correlating the lineament features of a given area with the orientation of the primary stress fields and fracture structures associated with the recent tectonic history that affected the region of study. The main premise of the method is that the most recent tectonic events in a given area have had the most significant influence on the nature of the existing fracture network and subsequently on the regional groundwater flow characteristics. A study site was selected within the state of S?o Paulo, Brazil, where a complex tectonic history dating back to Precambrian time has generated significant fracture porosity in the bedrock environment. The bedrock is heavily used in this area as a domestic and industrial aquifer. The most recent tectonic activity is associated with five distinct Cenozoic events that generated fracture features through both shear and extension stress fields. Due to the mode of formation, fracture zones generated by extension tend to have the largest effective apertures and are the most conductive to groundwater. By applying the HTD method in a series of test areas where specific Cenozoic events were dominant, fracture trends generated by shear and extension mechanisms could be identified. Water-well production capacity was correlated with proximity to extension-type structures in most cases. Other factors, such as the type of rock the well was completed in, had a much weaker influence on well capacity. Through this application, the HTD approach is shown to provide a methodology for delineating fractured areas within rock environments that have high potential for groundwater-resource development by combining classical lineament analysis with a clear understanding of the tectonic history of a given area. Electronic Publication  相似文献   

Application of Stochastic Fracture Network with Numerical Fluid Flow Simulations to Groundwater Flow Modeling in Fractured Rocks     

Wang Mingyu The University of Arizona  Tucson  Arizona  USA  Department of Water Resources  Environmental Engineering  China University of Geosciences  Beijing Chen Jinsong Wan Li Department of Water Resources  Environmental Engineering 《中国地质大学学报(英文版)》2001,12(3)

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太行-五台山区不同时代花岗岩类岩石学和地球化学的特征对比及陆壳演化     

罗淑兰  吴宗絮  邓晋福  杨瑞瑛 《岩石学报》1997,13(2)

通过对太行－五台山区太古宙、元古宙和中生代等不同时代的花岗岩类岩石学和地球化学特征的对比，并将晚太古时期花岗岩类同国内外同时期花岗岩类进行对比，确定了本区晚太古时期花岗岩类岩石组合为英云闪长岩－奥长花岗岩－花岗闪长岩或英云闪长岩－奥长花岗岩－花岗闪长岩－花岗岩，并以奥长花岗岩演化趋势为主，叠加了部分钙碱性演化；而元古宙、中生代花岗岩类岩石组合则主要为花岗闪长岩－花岗岩或花岗岩，以钙碱性演化趋势为特征。可以认为晚太古时期的太行－五台山区正处于陆壳演化的初始阶段和成熟阶段之间的过渡性阶段。  相似文献   

广西金牙金矿床中饱和烃丰度分布特征及其意义   总被引：2，自引：0，他引：2       下载免费PDF全文

肖建新  张爱云 《地球科学》1997,22(2):177-180

对广西金牙金矿床的可溶有机质族组成和气相色谱分析表明，矿体饱和烃的丰度低于围岩，矿体与围岩总抽提物所气相色谱图亦明显不同，尤其是甲醇－丙酮－苯抽提物的区别更明显，矿体与围岩饱和烃丰度的差异为分析有机质在金矿形成过程中的作用提供了线索，对其意义进行了讨论。  相似文献   

湖南石门中-下三叠统碳酸盐岩岩相组合及其沉积环境研究          下载免费PDF全文

田成  乐昌硕  张瑞锡  张平  许建儿 《地球科学》1997,6(3)

首先将研究区中、下三叠统碳酸盐岩划分成２１种岩相，并分析了各种岩相的沉积条件．在此基础上，建立了９个岩相组合类型，讨论了每个岩相组合的沉积环境．最后概括总结了纵向上存在的４个沉积旋回的沉积演化特征及蒸发岩的主要沉积层位  相似文献   

西藏羌塘地区第三系火山岩及与羌塘盆地含油性关系的研究          下载免费PDF全文

王方正  赖旭龙  郭铁鹰  王家生 《地球科学》1997,6(3)

西藏羌塘地区火山岩主要见于第三系石坪顶组，主要岩石类型是呈熔岩被产出的火山熔岩，包括辉石粗安岩、角闪粗面岩、角闪英安岩、黑云母英安岩等，其次可见次火山岩相的黑云母英安质碎斑熔岩和黑云母粗面质碎斑熔岩，以及辉石黑云母花斑岩．它们均为陆相中心式喷发的产物．岩石化学上属钾玄岩组合，可进一步分为钾玄岩系列和高硅钾玄岩系列，具非常典型的二元岩浆混合成因火山岩的岩石化学特征．其ＲＥＥ及微量元素特点表明二元岩浆混合前两个端元岩浆分别来自幔源和壳源．这些火山岩岩浆热事件对盆地有机烃类转化为石油和天然气是有利的，而破坏作用仅仅发生在火山机构附近  相似文献   

内蒙古东升庙矿区狼山群中变质"双峰式”火山岩夹层的确认及其意义   总被引：14，自引：2，他引：14       下载免费PDF全文

彭润民  翟裕生 《地球科学》1997,6(6)

东升庙矿床狼山群二组含矿地层中石英钠长浅（变）粒岩类（Ⅰ类，ｗ（ＳｉＯ２）＝７０．４７％～７３．０２％）、黑云钠—更长片岩类（Ⅱ１类，ｗ（ＳｉＯ２）＝５２．００％～５４．４３％）和钠—更长绿泥（角闪）片岩类（Ⅱ２类，ｗ（ＳｉＯ２）＝４７．４４％～４８．８６％）具如下特征：（１）稳定呈层产出，并与上、下相邻地层一道褶皱、变形；（２）含有变余斑晶和晶屑；（３）轻稀土元素富集，重稀土元素亏损；（４）多种岩石化学图解一致表明它们是正变质岩；（５）Ⅰ类与Ⅱ１类呈上、下层关系连续产出等特征，确认它们都是变质火山岩夹层，并具有“双峰式”组合．研究表明本矿床形成于元古宙大陆边缘的裂谷盆地．  相似文献   

节理围岩特性及其锚固效应模型试验研究     

任伟中 《地球科学》1997,22(6):660-664

通过堆砌尺寸为１８０ｃｍ×１４０ｃｍ×１５ｃｍ的大比尺结构模型，依据两组正交节理的不同倾角和间距、地应力及洞周有无锚杆等不同组合的１６种工况进行地下洞室分步开挖模型试验，研究节理对洞室围岩变形破坏的影响及锚杆对节理围岩的锚固效应．试验首次应用ＣＣＤ画像处理法和光学照相法进行位移观测．结果表明，岩体的变形大部分是由节理变形引起的，围岩塌落区完全由开挖自由面与节理的不利组合所控制，围岩变形主要由洞室尺寸、节理倾角及间距、地应力等决定．锚杆能大幅度减少围岩的变形破坏，垂向位移减少更甚，预应力锚杆使围岩变形进一步减小．  相似文献   

灵武煤田延安组不同沉积相源岩的生烃潜力     

初志民  张爱云 《煤田地质与勘探》1997,25(2):25-27

为研究不同沉积相源岩的生烃能力，选择宁夏灵武煤田延安组的对象，对其湖泊三角洲沉积体系下不同沉积相源岩进行热解分析，划分其生油岩类型或有机质类型，分析了不同沉积相源岩的生烃潜力。  相似文献   

Geochemistry of Archaean volcanic rocks from Iron Ore Supergroup, Singhbhum, eastern India     

S. Sengupta  S. K. Acharyya  J. B. DeSmeth 《Journal of Earth System Science》1997,106(4):327-342

Mafic-ultramafic rocks of Archaean age constitute a significant component of the Eastern Indian Craton. These occur in two different modes. In the eastern belt these occur as a long, linear enclave within the Singhbhum granite and the primary banding in them is subvertical. In the more extensive western belt along the periphery of the Singhbhum granite, the disposition of the primary banding is subhorizontal. The major rock type in both the belts is meta-basalt with minor peridotitic komatiite and basaltic komatiite occurring in the eastern belt. Rare ultramafic rocks with cumulate textures are present in both the belts. The larger volume of the basaltic rocks preclude the possibility of their being derived by fractional crystallization of the high-MgO components. On the basis of trace element and REE characters the rocks may be classified into three groups. One of the groups shows a tholeiitic trend and include samples mostly from the eastern belt while the second consisting mostly of samples from the western belt shows a calc-alkaline trend. The third group includes samples having elemental ratios intermediate between these two groups. Zr/Nb ratios for the tholeiitic and calc-alkaline samples are different suggesting their sources to be different. The tholeiitic samples have been generated from a source having chondritic REE characters, while the calc-alkaline samples have been generated from a source with LREE enriched character. The high-MgO components in both the groups are suggested to represent high degrees of melting compared to the basalts in each group. It is further suggested that the tholeiitic basalts have been generated relatively early from a chondritic source. Down-buckling of this material has added LREE enriched melts to the source, thereby changing its character into a LREE enriched one. Melting of a source with such changed character has subsequently produced the calc-alkaline melts. Rocks with variable but intermediate characters between these two groups have been generated as a result of contamination between these two groups.  相似文献