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771.
Wei Lin Nicolas Charles Yan Chen Ke Chen Michel Faure Lin Wu Fei Wang Qiuli Li Jun Wang Qingchen Wang 《Gondwana Research》2013,23(1):78-94
Granitoids play an important role in deciphering both crustal growth and tectonic evolution of Earth. In the eastern end of the Yinshan–Yanshan belt of North China Craton, the Yiwulüshan massif is a typical region that presents the tectonic evolution features of this belt. Our field work on the host rocks has demonstrated two phases of opposite tectonics: compressional and extensional, however, the deformation is almost invisible in the intrusive rocks. To improve the understanding of the tectonic evolution of the Yiwulüshan massif and the Late Mesozoic tectonics of East Asia, a multidisciplinary study has been carried out. In this study, anisotropy of magnetic susceptibility (AMS) and gravity modeling have been applied on these Jurassic plutons (Lüshan, Jishilazi and Guanyindong), which intrude into the Yiwulüshan massif. According to laboratory measurements and microscopic observations on thin sections, the AMS of the Yiwulüshan massif is characterized by secondary fabrics, indicating that the intensive post solidus deformation has reset the (primary) magmatic magnetic fabrics. A relatively gentle NW dipping magnetic foliation has been identified with two distinct groups of magnetic lineations of N34°E and N335°E orientations, namely LM1 and LM2, relatively. Gravity modeling reveals a southward thinning of the massif with a possible feeding zone rooted in the northern part of the massif. Integrating all results from structural observation, geochronological investigation, AMS measurement and gravity modeling, two tectonic phases have been identified in the Yiwulüshan massif, posterior to the Jurassic (180–160 Ma) magmatism in the Yinshan–Yanshan area. The early one concerns a Late Jurassic–Early Cretaceous (~ 141 Ma) compressional event with a top-to-the-south to southwest sense of shear. The second one shows an Early Cretaceous (~ 126 Ma) NW–SE ductile extensional shearing. At that time, sedimentary basins widened and Jurassic plutons started to be deformed under post solidus conditions. In fact, the NW–SE trend of the maximum stretching direction is a general feature of East Asian continent during Late Mesozoic. 相似文献
772.
测试数据准确可靠的高应变法检测,能够定量分析基桩缺陷,准确判定缺陷位置。通过工程桩的低应变法和高应变法对桩身完整性判定分析的工程实例,结合钻芯法验证,总结高应变法在不同情况下对桩身完整性的评定。 相似文献
773.
Integrated geoelectrical survey for groundwater and shallow subsurface evaluation: case study at Siliyin spring, El-Fayoum, Egypt 总被引:2,自引:1,他引:2
Mohamed Metwaly Gad El-Qady Usama Massoud Abeer El-Kenawy Jun Matsushima Nasser Al-Arifi 《International Journal of Earth Sciences》2010,99(6):1427-1436
Siliyin spring is one of the many natural fresh water springs in the Western Desert of Egypt. It is located at the central
part of El-Fayoum Delta, which is a potential place for urban developments and touristic activities. Integrated geoelectrical
survey was conducted to facilitate mapping the groundwater resources and the shallow subsurface structures in the area. Twenty-eight
transient electromagnetic (TEM) soundings, three vertical electrical soundings (VES) and three electrical resistivity tomography
(ERT) profiles were carried out around the Siliyin spring location. The dense cultivation, the rugged topography and the existence
of infra structure in the area hindered acquiring more data. The TEM data were inverted jointly with the VES and ERT, and
constrained by available geological information. Based on the inversion results, a set of geoelectrical cross-sections have
been constructed. The shallow sand to sandy clay layer that forms the shallow aquifer has been completely mapped underneath
and around the spring area. Flowing of water from the Siliyin spring is interconnected with the lateral lithological changes
from clay to sand soil. Exploration of the extension of Siliyin spring zone is recommended. The interpretation emphasizes
the importance of integrating the geoelectrical survey with the available geological information to obtain useful, cheap and
fast lithological and structural subsurface information. 相似文献
774.
Xiaolong Liu Siliang Li Zhongliang Wang Guilin Han Jun Li Baoli Wang Fushun Wang Li Bai 《中国地球化学学报》2017,36(4):667-679
Aquatic ecosystems have been identified as a globally significant source of nitrous oxide (N2O) due to continuous active nitrogen involvement, but the processes and influencing factors that control N2O production are still poorly understood, especially in reservoirs. For that, monthly N2O variations were monitored in Dongfeng reservoir (DFR) with a mesotrophic condition. The dissolved N2O concentration in DFR displayed a distinct spatial–temporal pattern but lower than that in the eutrophic reservoirs. During the whole sampling year, N2O saturation ranging from 144% to 640%, indicating that reservoir acted as source of atmospheric N2O. N2O production is induced by the introduction of nitrogen (NO3 ?, NH4 +) in mesotrophic reservoirs, and is also affected by oxygen level and water temperature. Nitrification was the predominate process for N2O production in DFR due to well-oxygenated longitudinal water layers. Mean values of estimated N2O flux from the air–water interface averaged 0.19 µmol m?2 h?1 with a range of 0.01–0.61 µmol m?2 h?1. DFR exhibited less N2O emission flux than that reported in a nearby eutrophic reservoir, but still acted as a moderate N2O source compared with other reservoirs and lakes worldwide. Annual emissions from the water–air interface of DFR were estimated to be 0.32 × 105 mol N–N2O, while N2O degassing from releasing water behind the dam during power generation was nearly five times greater. Hence, N2O degassing behind the dam should be taken into account for estimation of N2O emissions from artificial reservoirs, an omission that historically has probably resulted in underestimates. IPCC methodology should consider more specifically N2O emission estimation in aquatic ecosystems, especially in reservoirs, the default EF5 model will lead to an overestimation. 相似文献
775.
Nenad Tomašić Štefica Kampić Iva Juranović Cindrić Kristina Pikelj Mavro Lučić Danijela Mavrić Tajana Vučetić 《Central European Journal of Geosciences》2013,5(4):457-464
The adsorption properties in terms of cation exchange capacity and their relation to the soil and sediment constituents (clay minerals, Fe-, Mn-, and Al-oxyhydroxides, organic matter) were investigated in loess, soil-loess transition zone, and soil at four loess-soil sections in North-Western Croatia. Cation exchange capacity of the bulk samples, the samples after oxalate extraction of Fe, Mn and Al, and after removal of organic matter, as well as of the separated clay fraction, was determined using copper ethylenediamine. Cation exchange capacity (pH~7) of the bulk samples ranges from 5 to 12 cmol c /kg in soil, from 7 to 15 cmol c /kg in the soil-loess transition zone, and from 12 to 20 cmol c /kg in loess. Generally, CEC values increase with depth. Oxalate extraction of Fe, Mn, and Al, and removal of organic matter cause a CEC decrease of 3–38% and 8–55%, respectively, proving a considerable influence of these constituents to the bulk CEC values. In the separated clay fraction (<2 μm) CEC values are up to several times higher relative to those in the bulk samples. The measured CEC values of the bulk samples generally correspond to the clay mineral content identified. Also, a slight increase in muscovite/illite content with depth and the vermiculite occurrence in the loess horizon are concomitant with the CEC increase in deeper horizons, irrespective of the sample pretreatment. 相似文献
776.
山地系统提供了诊断和分析全球变化的最佳场所,通过对山地环境的研究,了解山地系统内物理、地球化学和生态系统演化的过程,可以准确理解山地环境变化对全球变化的贡献及反馈机制.本文重点针对山地系统的一系列研究计划、山地环境要素研究和近年的研究热点碳循环等方面进行了总结和回顾,并提出了未来山地环境研究应当重点关注的内容.近二、三十年来,国内外山地环境研究蓬勃兴起,推行了一系列研究计划,通过多学科的综合研究,在山地气象、水文、生物、生态、土地利用和人类活动影响等多方面取得了长足的进步,近年更是在全球碳循环方面开展了一些有益的探索,山地环境碳库是目前全球变化研究的热点之一.我国的山地环境研究在今后应更加关注以下3个方面的工作:1)山区环境变化指标的长期监测和分析;2)开展山地物理、化学和生物过程研究;3)基于模型的不同类型山区环境变化的综合研究. 相似文献
777.
坦桑尼亚汉德尼金矿床地质特征与找矿方向分析 总被引:2,自引:0,他引:2
汉德尼(Handeni)金矿是近来在坦桑尼亚绿岩带中发现的大型金矿床。该金矿床产在坦桑尼亚元古宙绿岩带中,矿体位于元古代斜长角闪岩(原岩为基性火山岩)的断裂带中,矿体多呈脉状、似层状,局部网脉状和浸染状,其容矿围岩为石榴石英岩,矿化主要发育黄铁矿化、黄铜矿化、磁黄铁矿化和毒砂化等,金矿物主要为自然金和金银矿,一般颗粒较... 相似文献
778.
779.
780.
地球空间数据集成多尺度问题基础研究 总被引:21,自引:0,他引:21
多尺度数据集成是地球空间数据集成中最难处理的问题。将多尺度数据的集成分解为空间和时间多尺度数据集成,在分析应用项目对数据尺度需求的基础上,就两种多尺度数据集成的传统和数据意义上的集成方法进行了详细的探讨。 相似文献