Rheological control on the tectonic evolution of a continental suture zone: the Variscan example from NW Iberia (Spain)   总被引：1，自引：1，他引：0  

Rubén Díez Fernández  David A. Foster  Juan Gómez Barreiro  Montserrat Alonso-García 《International Journal of Earth Sciences》2013,102(5):1305-1319

The Variscan continental suture zone exposed in NW Iberia is examined to uncover the long-lived rheological control exerted by the strata deposited over the external parts of Gondwana on its geodynamic evolution. The suture occurs within a set of allochthonous terranes whose limits were taken as domain boundaries to interpret the Variscan stacking of Paleozoic continental domains and retrodeform the resulting nappe pile. The suture zone formed due to closure of ocean basins located between Gondwana and Laurussia during the Late Paleozoic and consists of relics of oceanic and transitional crust. The suture zone exhibits a tabular to lens shape due to repeated tectonic events dominated by non-coaxial deformation (thrusts and low-angle normal faults). Thrusting and normal faulting also involved the margins of the continents bounding the suture. The structure of the continental blocks, however, is dominated by folds, particularly large nappe folds with pronounced superimposed flattening. The upper part of the basal allochthonous units comprises a rheologically incompetent domain below the suture zone. This domain is typified by the carbonaceous-rich strata, which are probably Ordovician–Silurian sediments based on U–Pb detrital zircon populations. The rheology of this layer determined the location of the first accretionary thrust that initiated the Late Devonian subduction of the Gondwana margin below the suture zone. By favoring fault development, the upper sequence of the basal allochthonous units as a whole influenced the exhumation of deep-seated continental crust, the transference of the suture zone over Gondwana, and the re-equilibration of the resulting overthickened crust.  相似文献   

Web-GIS tool for the management of rural land markets     

Juan Porta  Jorge Parapar  Paula García  Gracia Fernández  Juan Touriño  Ramón Doallo  Francisco Ónega  Inés Santé  Pablo Díaz  David Miranda  Rafael Crecente 《Earth Science Informatics》2013,6(4):209-226

Land abandonment and stagnation of rural markets in the last few years have become one of the main concerns of rural administrations. The use of Web and GIS (Geographic Information System) technologies can help to mitigate the effects of these problems. This paper pro-poses a novel Web-GIS tool with spatial capabilities for the dynamization of rural land markets by encouraging the transfer of land from owners to farmers through the leasing of plots. The system, based on open source software, offers information about the properties, their environment and their owners. It uses standards for handling the geographic information and for communicating with external data sources. This system was used as the basis for the development of SITEGAL, the tool for the management of the Land Bank of Galicia (www.bantegal.com/sitegal). SITEGAL has been operational since 2007 obtaining benefits for both administration and users (farmers and land owners), and promoting the e-Government.  相似文献   

Study of a rockfall in a limy conglomerate canyon (Covarrubias, Burgos, N. Spain)     

Leandro R. Alejano  Silverio García-Cortés  Fernando García-Bastante  Roberto Martínez-Alegría 《Environmental Earth Sciences》2013,70(6):2703-2717

In this paper, a rockfall of some tenths of cubic metres of rock, occurred in a conglomerate canyon in the northern Castilian plateau (N-Central Spain), is described in detail. This includes the basic data (geology, mapping, meteorological data and rock involved), the mechanical mechanism of the instability, the propagation and reach of the fallen rock boulders and the final location of the pieces. The study is based on detailed geological, aerial photography and geotechnical studies and advance topographical measurements. Geological engineering techniques are used to analyze the instability initiation and rockfall propagation. This study contributes to a better understanding of the geological processes leading to the occurrence of calcareous canyons and cliffs in the drainage network of the upper Castilian plateau. It is also helpful to improve our knowledge on natural rockfall phenomena for risk engineering purposes aiming to quantify, control and mitigate associated hazards.  相似文献   

Correlation between incompetent beds and slope deformation at Badong town in the Three Gorges reservoir, China   总被引：2，自引：0，他引：2  

Bo Chai  Kunlong Yin  Juan Du  Lili Xiao 《Environmental Earth Sciences》2013,69(1):209-223

Badong town is a new immigration area in the Three Gorges reservoir, China, which is built on many giant deep-seated landslides. In this region, the slope deformation is very severe and it is strongly correlated with the incompetent beds, which are distributed widely in the rock mass. In this paper, two giant deep-seated translational rock landslides used as study cases are Huangtupo landslide and Zhaoshuling landslide. Firstly, the composition materials, structures and deformation characteristics of the two landslides are analyzed. Then, the position, structure, mineral composition and the formation mechanism of the incompetent beds are studied in detail. Finally, based on the comparison of the position, mineral and structure between incompetent beds and sliding zones of the landslides, the correlations between incompetent beds and giant landslide are discussed. The results indicate that 13 large incompetent beds exist in the middle Triassic Badong Formation strata, which can be divided into three types as weak interlayers, crushed beds and groundwater corrosion zones. The dominant minerals in the incompetent beds are illite, chlorite, quartz and calcite. The contents of the clay minerals in different positions are quite distinct, and the maximum difference of clay content exceeds 70 %. In addition, it is found that the contents of minerals in incompetent beds are similar to the slide zones of the landslides. The initial deformation of slopes normally developed along the incompetent beds, which induced subsequent shear displacement easily. Under the effect of gravity, the deep slip zones were generated mainly along the incompetent beds and the failure mode evolved from creep to integral slide gradually. The results can provide an important reference for the mechanism analysis and prevention of landslides in Badong town.  相似文献   

Effect of electrode configuration on pH distribution and heavy metal ions migration during soil electrokinetic remediation   总被引：2，自引：0，他引：2  

Changsheng Peng  Juan O. Almeira  Qingbao Gu 《Environmental Earth Sciences》2013,69(1):257-265

Generation, migration, and distribution of H⁺ and OH^? have remarkable influence on heavy metal removal from soil during electrokinetic remediation. A series of experiments were carried out to investigate the effects of electrode configuration and voltage on pH distribution and heavy metal migration, based on the preliminary exploratory experiments. In the first phase, three soil samples were used to observe the effect of electrode configuration on pH distribution. Then, three more soil samples were used to explore the effect of voltage on ion migration. Finally, three other soil samples were used to explore the effect of electrode configuration (i.e. angle CAC) on pH distribution and heavy metal migration. The results showed that the soil was divided into acid, base, and pH-jump zones and that heavy metals migrated under low pH conditions and were deposited at the pH-jump zone. Heavy metal distribution was fairly consistent with pH distribution. Under the optimal condition of $ \angle $ CAC 60º and voltage 2.33 V/cm, 4.22 mg copper and 0.51 mg zinc migrated from acid zone and deposited in pH-jump zone with 6.44 kJ energy consumption.  相似文献   

Metal content and environmental risk assessment around high-altitude mine sites     

M. A. Muñoz  A. Faz  J. A. Acosta  S. Martínez-Martínez  J. M. Arocena 《Environmental Earth Sciences》2013,69(1):141-149

Gold mining activities in Apolobamba area, northwest of La Paz, Bolivia have created serious environmental concern and great risk to human health. The current methods used to extract gold are too primitive resulting in metal contamination of soil and water. The objectives of this study were to: (1) determine the degree of metal pollution, and (2) assess the risk to human health and environment in the Apolobamba area. Soil, water, sediment samples, and mine spills were collected and analyzed. Metals including Pb, Cu, Zn, Cd, and Hg concentrations were higher in surface soils than in subsurface soils indicating active atmospheric deposition of metals. Sediment samples had elevated levels of metals probably from mine spills discharged into the Sunchulli River. Surface soils in the Sunchulli community show the highest levels of Pb and Hg in all soil samples and may pose a risk to the health of the human population and environment.  相似文献   

Surface changes on crystalline stones due to salt crystallisation   总被引：1，自引：0，他引：1  

Patricia Vázquez  Ana Luque  Francisco J. Alonso  Carlota M. Grossi 《Environmental Earth Sciences》2013,69(4):1237-1248

This study assesses the changes on the surface of crystalline stones due to salt crystallisation. Efflorescence was forced to grow on the surface of granite and marbles through 60 cycles of salt crystallisation with sodium sulphate. Changes on surface roughness, gloss and colour were measured every 15 cycles and the specimens were examined with naked eye and SEM. Sodium sulphate produces damage which depends on mineral composition. Results show that granites experience a mechanical decay with an increase in roughness. Peaks of mica can be observed on the surface and cracks widen and grow deeper. Colour and gloss do not show any significant change, although gloss decreases with an increase in surface roughness. In marbles, the decay is mainly chemical. Surface roughness increases due to dissolution of the calcite. White marbles exhibit yellowing. Gloss decreases during the first cycles—as grain boundaries become more visible—but tends to regain almost its initial value as the number of cycles increases. In this case, gloss does not show any relation with surface roughness.  相似文献   

柴达木盆地北缘下干柴沟组下段湖相混合沉积发育特征及其对储层的影响     

禚喜准  王琪  张瑞  李娟 《沉积学报》2013,31(4):724-729

柴达木盆地北缘的古近系下干柴沟组下段是油气勘探的重要目标,查明该区储层发育的控制因素是深入勘探的重要基础。根据岩屑录井、普通薄片以及铸体薄片等资料对该区冷湖七号和南八仙构造的储层特征进行了对比分析。研究表明,该区大量发育陆源碎屑-碳酸盐的混合沉积,但是由于水体咸度的不同:在冷湖七号的滨浅湖混积岩中碳酸盐和硬石膏含量较高,颗粒主要为基底式胶结;而南八仙构造地处辫状河三角洲前缘相带,因河流的稀释作用,混积岩中硬石膏含量很少,颗粒为孔隙式－基底式钙质胶结,原生孔喉较为发育,有利于后期酸性流体的溶蚀改造。两种类型混积岩的初始孔隙度以及孔喉演化模式的不同,是最终引起两个地区含油气丰度巨大差异的一个原因。  相似文献   

中国矿产资源潜力评价成果数据质量控制及方法技术   总被引：3，自引：2，他引：1       下载免费PDF全文

左群超  杨东来宋 越 马 娟 肖志坚 《中国地质》2013,40(4):1314-1328

本文以中国矿产资源潜力评价专项成果数据质量控制工作为依托,系统地阐述了应用于中国矿产资源潜力评价专项成果数据质量控制的基本理论及方法技术.通过实际应用证实了该质量控制方法技术的有效性、可行性、实用性和代表性,有一定借鉴意义和推广价值.该方法技术具有很好的示范效果和推广应用前景,适用于各类地质空间数据项目成果数据质量控制工作.  相似文献   

句容赤山湖地热井成井工艺方法          下载免费PDF全文

陈进宝  苏金宝  陈娟  杨春光  曹勇 《探矿工程》2013,40(8):35-38

江苏句容出露发育广泛白垩系红色细砂岩、泥质砂岩,浅埋于松散层之下,水文地质条件极差,地下水贫乏,钻井多数为干孔。通过钻探施工,句容赤山湖地热井先期排水量在2～3 m3/h,通过对其地质含水条件的分析,提出了应用深水泵与“脉动排砂法”,分选抽水层位等新的施工、洗井、抽水工艺理论,最终使该井日产高达500余m3。该井的成功对贫水地层找水以及碎屑岩区洗井排水具有巨大的借鉴意义与实用价值。  相似文献