C-axis fabrics of quartz-ribbons during high-temperature deformation of syn-tectonic granitoids (Sila Massif, Calabria, Italy)   总被引：1，自引：0，他引：1  

Vincenzo Festa   《Comptes Rendus Geoscience》2009,341(7):557-567

Late-Hercynian, high temperature (HT) shear deformation affected the zone straddling the contact between the Sila Massif batholith (above) and the host migmatitic paragneisses (below). A segment of the regional HT shear zone was investigated close to the town of Mesoraca, where a natural section allows one to analyse the solidus deformation of syn-tectonic granitoids. Shearing favoured the formation of polycrystalline quartz ribbons in deformed granodiorite and tonalite. Two main c-axis fabrics were found in the quartz-ribbons, different from each other by opening angles around Z between strong point maxima, in accordance with deformation under granulite to amphibolite facies conditions. These fabrics, along with microstructural observations, suggest that temperature of deformation played a key role and that ribboning was accompanied by the activation of (i) prism [c] slip and prism [c] + prism <a> slips, under granulite facies conditions, followed by (ii) basal <a> and prism <a> slips under amphibolite facies conditions.  相似文献   

Grain structure of the Earth's inner core     

Lucile Venet  Thierry Duffar  Renaud Deguen 《Comptes Rendus Geoscience》2009,341(7):513-516

The coarsening rate of an initial grain structure is calculated and compared to the inner core growth rate. An estimate of the present size of the grains in the centre of the core varies from 560 m to 12 km, depending on the value taken for the diffusion coefficient of iron in the core. Regardless of the hypotheses chosen, this size is homogeneous inside the inner core.  相似文献   

Study on soil-pile-structure-TMD interaction system by shaking table model test   总被引：1，自引：0，他引：1  

楼梦麟  王文剑 《地震工程与工程振动(英文版)》2004,3(1):127-137

The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soilstructure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify theSSI effect on the seismic performance ofTMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.  相似文献   

Seasonal and spatial characteristics of seawater and sediment at Youngil Bay, southeast coast of Korea   总被引：1，自引：0，他引：1  

Lee M  Bae W  Chung J  Jung HS  Shim H 《Marine pollution bulletin》2008,57(6-12):325-334

The seasonal geochemical characteristics of the seawater and sediments and the major factors causing heavy metal contamination were investigated at the Youngil bay and the Hyungsan river estuary in the Southeast Coast of Korea, where a world-scale steel-industry complex (Pohang iron and steel industrial complex, POSCO) is located. The seasonal and spatial distribution characteristics of temperature, dissolved oxygen (DO), pH, and nutrients of the seawater were studied at 45 fixed stations, especially focusing on the river mouth area. Sediments at 27 stations were examined during winter and summer to determine the major controlling factors for the distribution of metals, using correlation matrix and R-mode factor analyses, and to evaluate the pollution status, using the modified geoaccumulation (I(geo)(')) index. Temperatures for the effluent from the POSCO located at the Hyungsan river mouth were 2-3 degrees C higher compared to other sampling areas, due to the thermal discharge from the POSCO. The DO concentration of the surface water at the Pohang old port was as low as 2-4 mg/L. In spring, the DO value at the Hyungsan river mouth was higher than 12 mg/L, by the mass multiplication of phytoplanktons at the river mouth where seawater temperature and nutrients concentrations were relatively high, resulting in the pH value of higher than 8.3. The nitrogen to phosphorus (N/P) ratios at the river mouth were 20-150 times higher compared to other areas, implying that the nitrogen loading into this semi-enclosed bay is significantly higher than phosphorus and the major nitrogen sources are not only the domestic sewage from the city but the industrial wastewater from the POSCO and other steel factories nearby. The phosphorus concentrations at the Pohang old port were shown 3-10 times higher than those at other stations, due to the inflow of pollutants generated from the nearby ships anchoring and the release of phosphate from the bottom sediment. Results from the sediment analysis showed that the major controlling factors for the distribution pattern of each metal are grain size and organic carbon (C(org)) content. Based on the factor analysis, Al, Fe, Cr, Li, and Pb were shown strongly correlated with the mean grain size (Mz), whereas Cd, Cu, Zn, and Sn with the C(org) content. Results from the fractionation of the sedimentary metals into lattice and labile fractions to characterize the mobility of sediment metals showed that the mineral lattice fraction was high in the order of Al=K>Cr>Li>Sr>Fe, while the labile fraction, which might be released to the overlying water, was in the order of Pb>Zn>Cd>Cu>Ca>Sn. Evaluation of the sediment pollution status by applying (I(geo)(')) of 13 metals showed Cd, Cu, and Zn as high as 1-3 range at the old port. Even though the overall marine pollution mainly by the world-class steel industrial complex in this semi-enclosed bay area studied does not currently pose a serious threat, due to the seawater circulation and the large influx of river discharge, the countermeasures to implement the sediments concentrated with heavy metals, especially at the old port with no seawater circulation, are still warranted for this coastal water environment.  相似文献   

Holocene Earth’s magnetic field variations recorded in marine sediments of the NW African continental margin     

U.?Bleil  M.?DillonEmail author 《Studia Geophysica et Geodaetica》2008,52(2):133-155

Holocene records documenting variations in direction and intensity of the geomagnetic field during the last about seven and a half millennia are presented for Northwest Africa. High resolution paleomagnetic analyses of two marine sediment sequences recovered from around 900 meter water depth on the upper continental slope off Cape Ghir (30°51′N, 10°16′W) were supplemented by magnetic measurements characterizing composition, concentration, grain size and coercivity of the magnetic mineral assemblage. Age control for the high sedimentation rate deposits (∼60 cm/kyr) was established by AMS radiocarbon dates. The natural remanent magnetization (NRM) is very predominantly carried by a fine grained, mostly single domain (titano-)magnetite fraction allowing the reliable definition of stable NRM inclinations and declinations from alternating field demagnetization and principal component analysis. Predictions of the Korte and Constable (2005) geomagnetic field model CALS7K.2 for the study area are in fair agreement with the Holocene directional records for the most parts, yet noticeable differences exist in some intervals. The magnetic mineral inventory of the sediments reveals various climate controlled variations, specifically in concentration and grain size. A very strong impact had the mid-Holocene environmental change from humid to arid conditions on the African continent which also clearly affects relative paleointensity (RPI) estimates based on different remanence normalizers. To overcome this problem the pseudo-Thellier RPI technique has been applied. The results represent the first Holocene record of Earth’s magnetic field intensity variations in the NW Africa region. It displays long term trends similar to those of model predictions, but also conspicuous millennium scale differences.  相似文献   

Near-inertial motions in and around the Palamós submarine canyon (NW Mediterranean) generated by a severe storm     

Antoni Jordi  Dong-Ping Wang 《Continental Shelf Research》2008,28(17):150-2534

During 9–16 November 2001 the western Mediterranean Sea was lashed by one of the most extreme storms of the last decades. Current meter data from seven moorings in the Palamós submarine canyon (northwestern Mediterranean) are analyzed to understand the vertical propagation of near-inertial energy generated by the storm. The daily inertial rotary components are examined for evidence of free and forced near-inertial oscillations. Free near-inertial motions are increased during the storm, although they are larger outside the canyon than inside. Conversely, forced near-inertial motions are relatively large inside the canyon but are almost negligible outside. Based on the results of a three-dimensional ocean circulation model, these differences are shown to be caused by the presence of a storm-generated alongshore front. The mechanisms by which near-inertial energy propagates are distinct at each side of the front. On the onshore side of the front (inside the canyon), free near-inertial motions are rapidly carried away by normal inertial waves, and wave reflection off canyon wall is responsible for the dissipation of free near-inertial motions and enhancement of forced near-inertial motions. On the offshore side of the front (outside the canyon), on the other hand, free near-inertial motions propagates first downward with anomalously low frequency internal waves and are then advected southward and offshore by the mean flow.  相似文献   

山东省数字强震台站建设及其汶川8.0级地震的纪录特征     

肖兰喜  杜宪宋  冯志军  张昊  潘双进 《华北地震科学》2008,26(4):13-16

介绍了山东省强震观测台站在十五期间的建设情况,通过汶川8.0级地震的检验,表明山东强震观测台站的观测仪器运行良好,强震台站的场地条件与强震动参数存在明显的相关关系,强震动的土层放大效应非常明显,其影响对结构第一周期在1s-8s左右的建筑物具有重要的作用。  相似文献   

宁波育王山山前断层几何结构及新活动时代     

宋方敏  ;陈献程  ;杨晓平  ;宋新初  ;王里  ;张兰凤  ;李陈侠 《火山地质与矿产》2008,(3):177-186

根据1：10000条带状地质填图所获资料,分析了育王山山前断层的几何结构和新活动时代。断层北起岙张水库大坝东北,向南经河头蕉-竺家-陈家-钱家-俞家-王家一线以西,止于詹家西南,由2条次级段呈羽列式展布,北段为岙张水库-红岩水库段,南段为红岩水库东南-詹家段。剖面上断层地貌显示清楚,西侧为侏罗系构成的育王山低山,东侧为大楔盆地。各条断层皆由多个断面构成宽几米-几十米的断层带。根据探槽、天然剖面特征和OSL、ESR样品年龄测试结果综合分析,断层至少有两期活动,早期活动性质为逆断层,时间为早更新世,晚期活动性质为右旋走滑兼正断或逆断层,时间为中更新世,最新活动时代为中更新世晚期。通过探槽揭露,确定育王山山前洪积扇陡坎是人类活动造成,而非断层陡坎。  相似文献   

分布式基坑监测信息管理与预警系统的研制   总被引：3，自引：0，他引：3  

吴振君  王浩  王水林  葛修润 《岩土力学》2008,29(9):2503-2507

针对基坑监测的信息化、集成化、共享化要求,开发了基于GIS的分布式基坑监测信息管理与预警系统。介绍了系统的结构框架,着重介绍了系统实现的功能。在GIS图形可视化技术基础上,系统地实现了区域内多个基坑地质勘察、设计、施工等资料及测点信息、监测仪器、监测数据、周边建筑物等相关资料的全面采集,并在此基础上实现了信息的存储、处理、分析、查询、预测、预警以及成果输出的自动化。系统采用C/S结构实现信息共享与多人协作,在网络环境下可高效运行,为基坑监测提供了一个功能强大的信息平台。  相似文献   

Uncertainties of geochemical codes and thermodynamic databases for predicting the impact of carbon dioxide on geologic formations     

《Applied Geochemistry》2016

Numerical codes are applied to calculate chemical reactions following geologic carbon sequestration in deep formations and CO₂ leakage in shallow formations. However, using different thermodynamic databases generates variations in the simulation results, which are referred to as the model uncertainty. The PHREEQC and The Geochemist's Workbench codes were used to simulate anorthite dissolution for storage, retention, transfer, and near-surface formation waters in the respective geological units. For each of the formation waters, a simple one-dimensional scenario was simulated using eight different thermodynamic databases. Groundwaters in shallow aquifers commonly exhibit low ionic strengths (<0.5 mol/kgw) and low temperatures, whereas storage formation waters are characterized by high ionic strength (>1.0 mol/kgw) and high temperatures. In storage formations, mineral trapping is the most efficient process for long-term CO₂ storage. However, with respect to the geological formations and the time needed for anorthite dissolution, the model uncertainties associated with using different combinations of numerical codes and thermodynamic databases were largest (∼90%) for the storage formation waters at 58 °C and I = 6.5 mol/l. Conversely, in near-surface formation waters, the model uncertainty was less than 1%. Due to CO₂ dissolution, the calculated pH of the formation waters decreased to a range between pH 4.0 and 5.5. In this pH range, the dissolution mechanism of anorthite switches from the slow neutral mechanism to the faster acid mechanism, causing dissolution time length variations. The calculated pH variation further increased with rising ionic strength. A detailed examination of the reasons revealed the activity coefficient calculation method of the main aquatic species to have the largest impact on the simulated model results. The calculation method of the CO₂ activity coefficient had the second largest impact. Via calibration with the experimental data, a specific thermodynamic database can be chosen to represent these experimental results. However, the calibration of thermodynamic databases is not possible for all potential reactions in more complex geological systems at large ranges of temperature, ionic strength and pressure conditions. The uncertainties associated with using thermodynamic databases quantified in this study for CO₂ storage systems will therefore persist independently from previously conducted calibrations of thermodynamic databases with experimental or field data. In view of these model uncertainties, the modeller is encouraged to include a routine in the simulations for quantification of the model uncertainty depending on the specific scenario or to assess the simulation results as a range of values that represent a soft outcome.  相似文献