Delineation of groundwater protection zones by the backward particle tracking method: theoretical background and GIS-based stochastic analysis   总被引：1，自引：0，他引：1  

Konstadinos N. Moutsopoulos  Alexandra Gemitzi  Vassilios A. Tsihrintzis 《Environmental Geology》2008,54(5):1081-1090

The backward particle tracking method, an effective and powerful tool that can be used to delineate groundwater protection zones, is presented. The theoretical background and insights on the applicability of this method are provided. Moreover, the present work enriches the backward particle tracking method with an uncertainty analysis concerning the porosity values, applying a Monte Carlo (MC) approach, coupled with the use of geographical information systems (GIS). As an application example, a wellfield in the Komotini area, Greece, is investigated. The present study may serve as a potential guideline for wellfield delineation, particularly in areas like Greece where lack of data related to the hydrogeological system is often a problem.  相似文献   

Bedrock, soils, and hillslope hydrology in the Central Texas Hill Country, USA: implications on environmental management in a carbonate-rock terrain     

C. M. Woodruff Jr  L. P. Wilding 《Environmental Geology》2008,55(3):605-618

The Hill Country of Central Texas, USA, is undergoing rapid socioeconomic development, but environmental management of this region is hampered by misconceptions about local bedrock, soils, terrain, and hydrologic processes. The Hill Country is underlain mostly by Glen Rose Limestone (Lower Cretaceous) and exhibits a stepped terrain, which has been incorrectly attributed to alternating hard and soft bedrock strata. Other characteristics mistakenly attributed to this landscape include thin soils with scant water-retention capabilities, and rapid runoff as the dominant hydrologic process. This report presents new findings: unweathered bedrock is well indurated, but interbeds exhibit variable weathering rates. Recessive slopes (“risers”) on this stepped terrain result from rapid deterioration of strata having generally heterogeneous depositional fabrics (bioturbation and irregular clay partings) in contrast to ledge-forming strata having homogeneous fabrics. A stony regolith is thus formed beneath risers, providing porous and permeable ground that retards runoff and promotes the formation of moderately deep to deep (two-tiered) regolith/soil zones. These surficial materials on local steep slopes compose important natural environmental buffers; they support diverse biota and enhanced geochemical cycling of nutrients; they also exhibit significant water retention and enhanced erosion abatement. Proper land management demands recognition of these attributes in the siting, design, and construction of facilities.  相似文献   

Numerical modeling assessment of three-gate structures for capturing contaminated groundwater     

Paul F. Hudak 《Environmental Geology》2008,55(6):1311-1317

This modeling study evaluated the capability of alternative funnel-and-gate structures with three gates for capturing contaminated groundwater in a hypothetical unconfined aquifer. Simulated interceptor structures were linear and 45 m wide, consisting of three gates and two funnels (walls). One gate occupied the center and two gates occupied the ends of the interceptor structures. The structures, positioned perpendicular to regional groundwater flow, traversed the entire thickness of the aquifer. A total of four structures were evaluated (numbers designate widths of end, center, and end gates, respectively, in meters): 3-3-3, 2-5-2, 1-7-1, and 4-1-4. Particle tracking and zonal water budgets identified shapes of capture zones and discharge patterns for each interceptor structure. A mass transport model, accounting for advection and hydrodynamic dispersion, tested the capability of each structure for capturing a contaminant plume. Results suggest that: time-dependent capture zones underestimate the amount of time to capture a contaminant plume, wide center gates facilitate plume capture, and wide end gates facilitate lateral containment of contaminants. Of the structures simulated, the 2-5-2 configuration was relatively efficient at processing and containing the simulated contaminant plume.  相似文献   

Triassic Nb-enriched basalts, magnesian andesites, and adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by slab-derived melts in the mantle wedge   总被引：10，自引：0，他引：10  

Qiang Wang  Derek A. Wyman  Jifeng Xu  Yusheng Wan  Chaofeng Li  Feng Zi  Ziqi Jiang  Huaning Qiu  Zhuyin Chu  Zhenhua Zhao  Yanhui Dong 《Contributions to Mineralogy and Petrology》2008,155(4):473-490

New chronological, geochemical, and isotopic data are reported for Triassic (219–236 Ma) adakite-magnesian andesite-Nb-enriched basaltic rock associations from the Tuotuohe area, central Qiangtang terrane. The adakites and magnesian andesites are characterized by high Sr/Y (25–45), La/Yb (14–42) and Na₂O/K₂O (12–49) ratios, high Al₂O₃ (15.34–18.28 wt%) and moderate to high Sr concentrations (220–498 ppm) and ε_ND (t) (+0.86 to +1.21) values. Low enrichments of Th, Rb relative to Nb, and subequal normalized Nb and La contents, and enrichments of light rare earth elements combine to distinguish a group of Nb-enriched basaltic rocks (NEBs). They have positive ε_ND (t) (+2.57 to +5.16) values. Positive correlations between Th, La and Nb and an absence of negative Nb anomalies on mantle normalized plots indicate the NEBs are products of a mantle source metasomatized by a slab melt rather than by hydrous fluids. A continuous compositional variation between adakites and magnesian andesites confirms slab melt interaction with mantle peridotite. The spatial association of the NEBs with adakites and magnesian andesites define an “adakitic metasomatic volcanic series” recognized in many demonstrably subduction-related environments (e.g., Mindanao arc, Philippines; Kamchatka arc, Russia; and southern Baja California arc, Mexico). The age of the Touhuohe suite, and its correlation with Triassic NEB to the north indicates that volcanism derived from subduction-modified mantle was abundant prior to 220 Ma in the central Qiangtang terrane.  相似文献   

Structural elements of the Makran region, Oman sea and their potential relevance to tsunamigenisis     

Mohammad Mokhtari  Iraj Abdollahie Fard  Khaled Hessami 《Natural Hazards》2008,47(2):185-199

The character of convergence along the Arabian–Iranian plate boundary changes radically eastward from the Zagros ranges to the Makran region. This appears to be due to collision of continental crust in the west, in contrast to subduction of oceanic crust in the east. The Makran subduction zone with a length of about 900 km display progressively older and highly deformed sedimentary units northward from the coast, together with an increase in elevation of the ranges. North of the Makran ranges are large subsiding basins, flanked to the north by active volcanoes. Based on 2D seismic reflection data obtained in this study, the main structural provinces and elements in the Gulf of Oman include: (i) the structural elements on the northeastern part of the Arabian Plate and, (ii) the Offshore Makran Accretionary Complex. Based on detailed analysis of these data on the northeastern part of the Arabian Plate five structural provinces and elements—the Musendam High, the Musendam Peneplain, the Musendam Slope, the Dibba Zone, and the Abyssal Plain have been identified. Further, the Offshore Makran Accretionary Complex shown is to consist Accretionary Prism and the For-Arc Basin, while the Accretionary Prism has been subdivided into the Accretionary Wedge and the Accreted/Colored Mélange. Lastly, it is important to note that the Makran subduction zone lacks the trench. The identification of these structural elements should help in better understanding the seismicity of the Makran region in general and the subduction zone in particular. The 1945 magnitude 8.1 tsunamigenic earthquake of the Makran and some other historical events are illustrative of the coastal region’s vulnerability to future tsunami in the area, and such data should be of value to the developing Indian Ocean Tsunami Warning System.  相似文献   

塔里木盆地西部吐木休克断裂带的主要特征和构造演化   总被引：8，自引：5，他引：3       下载免费PDF全文

朱德丰  刘和甫  吴根耀 《地质科学》2008,43(2):209-227

塔里木盆地西部的吐木休克断裂带是中央隆起(前身是晋宁期碰撞造山带)的次级单元巴楚断隆与北部坳陷的次级单元阿瓦提凹陷之间的分界。本文以大量的地质和地球物理证据,证明它是一条内部结构复杂且切穿地壳的深断裂。结合区域构造演化恢复了断裂发育史,指出它经历过三期重大的冲断活动,分别发生在加里东期、海西期和新近纪。新近纪的冲断与巴楚断隆的南界断裂带有相同的构造样式,可分为两幕:中新世的冲断受制于南天山前陆冲断带的向南扩展,更新世的冲断主要受制于西昆仑前陆冲断带的向北扩展。吐木休克断裂带的东西走向段和北西走向段的构造特征尚有若干差异,前者在加里东期活动较强,反映了构造的继承性;北西走向段则是加里东期出现的新生构造,在海西期进一步发展,更新世时因被卷入西昆仑的前陆冲断作用,表现出强烈而复杂的变形。  相似文献   

塔里木西部地区古生代断裂活动的方式和机制   总被引：15，自引：2，他引：13       下载免费PDF全文

李曰俊  吴根耀  孟庆龙  师骏  冯晓军  郑民 《地质科学》2008,43(4):727-745

基于系统的地震剖面解释及其与塔中地区的对比,本文探讨了塔里木西部地区古生代断裂活动的方式和机制。玛东断裂带是一条宽阔的北东向盖层滑脱型褶皱冲断带,前展式向东南扩展,冲断作用发生在奥陶纪末。巴东断裂(吐土休克Ⅱ号断裂)为北西向基底卷入型冲断带,奥陶纪末和中二叠世末发生冲断。巴西断裂和塔参2井南断裂是海西期的正断层。塔里木古板块古生代的发育受邻侧的造山带演化制约,近东西向和北东向断裂奥陶纪末的冲断是继承基底构造发育的。塔中地区的近北西向断裂是晚寒武世的新生断裂,加里东运动可分为两幕:奥陶纪末的冲断(艾比湖运动)和晚志留-中泥盆世的冲断-走滑,后者向西明显减弱。塔里木西部的部分北西向断裂(如康西断裂)可归入塔中北西向断裂系。北东向的玛东断裂带是其西的向北(东)冲断的吐木休克断裂带与其东的向南偏东冲断的塔中8-1井——塔中5井断裂带之间的调节断层。  相似文献   

郯庐断裂带张八岭隆起南段花岗岩LA-ICP MS锆石U-Pb年龄及其构造意义   总被引：10，自引：8，他引：2  

牛漫兰  朱光  谢成龙  柳小明  曹洋  谢文雅 《岩石学报》2008,24(8)

本文利用LA-ICP MS方法,对零星分布于郯庐断裂带张八岭隆起南段肥东-巢湖地区的一些花岗岩体进行了锆石U-Pb同位素年代学研究.结果表明,西徐村北岩体、尖山岩体、西花村岩体、永丰岩体和锦张村岩体的形成年龄分别为126.9 ±1.0Ma、114.8±1.3Ma、108.1 ±1.6Ma、103.0 ±0.9Ma和120.3 ±0.7Ma,这些花岗岩体均形成于早白垩世,但侵位时间有一定差异.与郯庐断裂带西侧的鲁西、徐淮、蚌埠地区同时代克拉通内部侵入岩相比,断裂带内岩浆活动持续的时间更长(～27Ma).这一结果不但指示郯庐断裂带上的岩浆活动是不均一的,各地岩浆在活动的强烈程度和时间特征上均有很大的差异,而且显示了断裂带内比克拉通内部岩浆活动结束时间较晚,暗示其下岩石圈可能有更为强烈的减薄程度和更长的减薄历史.  相似文献   

江西永平铜矿区花岗岩热液蚀变与岩石成因:矿物化学、元素地球化学和Sr-Nd-Hf同位素制约   总被引：15，自引：11，他引：4  

朱碧  蒋少涌  丁昕  姜耀辉  倪培  顾连兴 《岩石学报》2008,24(8)

永平铜矿床是位于华南钱塘江-信江断裂坳陷带中的一个大型铜矿床.矿区内出露的岩浆岩主要有似斑状黑云母花岗岩体和少量石英斑岩脉,黑云母花岗岩岩体内及接触带发育斑岩型和矽卡岩型铜钼钨多金属矿化.对岩体中黑云母的电子探针成分分析表明,似斑状黑云母花岗岩中黑云母具有富镁贫铁高钛的特点,Fe/(Fe Mg)为0.21～0.33,TiO2含量为2.12%～4.28%;而石英斑岩脉中黑云母更加富镁贫铁,Fe/(Fe MS)为0.10～0.15,TiO2含量为2.43%～3.86%.黑云母的化学组成表明花岗质岩浆形成时的氧逸度很高,与长江中下游地区其他含铜花岗质岩体相吻合.永平花岗岩体遭受了较强的热液蚀变作用,部分黑云母蚀变为绿泥石.石英斑岩中绿泥石具有富铁贫镁低钛的特征(Fe/(Fe Mg)=0.72～0.76;TiO2=0.02%～0.06%),其形成温度为139～224℃.而似斑状黑云母花岗岩中绿泥石相对贫铁富镁高钛(Fe/(Fe Mg)=0.36～0.44;TiO2=0.05%～0.36%),形成温度稍高,为229～346℃,与该矿床流体包裹体研究获得的成矿温度(220～400℃)基本吻合.Sr-Nd-Hf同位素综合研究表明,永平似斑状黑云母花岗岩具有变化较大且相对较高的εHf(t)值(-0.1～-10.3)和εNd(t)值(-5.83～-7.95),反映岩石具有明显的壳幔混合成因特征.而石英斑岩的εHf(t)值(-8.4～-12.5)和εNd(t)值(-9.93～-10.2)均稍低于似斑状黑云母花岗岩,反映其形成过程中幔源物质贡献相对较小.永平岩体的地壳端元很可能就是该区中元古代基底地层重熔的产物.  相似文献   

辽宁省海洋环境保护与海岸带可持续开发利用     

刘现明 《海岸工程》1995,14(4):33-36

在分析综合辽宁省海岸带调查和沿海经济贝类污染监测资料基础上，根据辽宁海岸带水质，沉积物和生物污染现状及发展趋势。针对所存在的问题，讨论了辽宁省海洋污染特别是赤潮对海洋资源的破坏，并在组织机构，地方立法，海岸带环境保护规划，污染源控制与整体环境改进，监测方案等方面提出了建设海上辽宁、加强辽宁省海洋环境保护与海岸可持续开发利用的建议。  相似文献