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181.
本文从分析铀市场价格规律入手,指出在铀市场价格连续下跌以后,于2000年可能有回升现象;在分析全球铀的产需情况后指出,自1990年开始出现自然铀的需求量大于生产量的趋势;在分析国内产需发展趋势的基础上指出,不能盲目满足于现有地质储量,而应密切注视商业铀储量和发展核电对铀的需求量之间的关系。最后,在综合分析全球铀经济地质形势的基础上,认为我国应把地质工作重点转移到以寻找低成本铀资源为中心的轨道上来, 相似文献
182.
杨宇星 《地质灾害与环境保护》2001,12(4):41-43
白恶统红层强烈风化复杂工程地质条件下,基础处理采用静压预应力管桩,可能出现管桩长度难以控制“超长桩”现象,广州和平花园施工实践表明,局部管桩长度难以控制,主要与持力层度剧烈变化及有上硬下软或硬夹层的工程地质条件有关。“超长桩”现象为一般管桩通过硬夹层折射;断桩在某软弱部位堆积造成。 相似文献
183.
阿尔金北缘大平沟金矿床成因 总被引:4,自引:1,他引:4
大平沟金矿是阿尔金北缘地区近年来新发现的一个中型金矿床。它受韧性剪切带构造的控制,矿化类型为蚀变糜棱岩型夹少量钾长石石英脉型。文章通过地质地球化学的研究,探讨了该矿床的成因。稀土元素、硫同位素、铅同位素和锶同位素地球化学特征反映成矿物质主要来源于变质岩;流体包裹体和氢氧同位素反映成矿流体主要来源于变质水,有少量重熔岩浆水和大气降水的混入,成矿温度198~2 90℃,成矿流体密度0 .791~0 .971g/cm3 ;盐度w(NaCleq) =2 .0 3%~5 .5 % ,成矿压力(42 0~72 0 )×10 5Pa ,成矿深度为1.6 1~2 .6 8km。石英流体包裹体Rb_Sr等时线年龄表明成矿时代为加里东期。大平沟金矿床属于中温动力变质热液成因矿床。 相似文献
184.
河南西峡-内乡琥珀矿床的初步研究 总被引:2,自引:0,他引:2
河南西峡-内乡琥珀矿床是我国琥珀市场上原料的重要产地。通过对该矿床的地层、岩相、古地理以及水动力条件等因素的分析研究,以及对琥珀矿体地质特征、琥珀物理性质及化学组成特征的研究,认为该琥珀矿床属于晚白垩世河流冲、洪积沉积矿床。 相似文献
185.
M.R. Kaplan A. Coronato N.R.J. Hulton J.O. Rabassa P.W. Kubik S.P.H.T. Freeman 《Geomorphology》2007,87(4):284-301
We measured in situ 10Be, 26Al and36Cl on glacial deposits as old as 1.1 Myr in the southernmost part of Patagonia and on northern Tierra del Fuego to understand boulder and moraine and, by inference, landscape changes. Nuclide concentrations indicate that surface boulders have been exposed for far less time than the ages of moraines they sit upon. The moraine ages are themselves constrained by previously obtained 40Ar/39Ar ages on interbedded lava flows or U-series and amino acid measurements on related (non-glacial) marine deposits. We suggest that a combination of boulder erosion and their exhumation from the moraine matrix could cause the erratics to have a large age variance and often short exposure histories, despite the fact that some moraine landforms are demonstrably 1 Myr old. We hypothesize that fast or episodic rates of landscape change occurred during glacial times or near the sea during interglacials. Comparison with boulder erosion rates and exhumation histories derived for the middle latitudes of semi-arid Patagonia imply different geomorphic processes operating in southernmost South America. We infer a faster rate of landscape degradation towards the higher latitudes where conditions have been colder and wetter. 相似文献
186.
187.
Seismicity, seismic input and site effects in the Sahel—Algiers region (North Algeria) 总被引:2,自引:0,他引:2
A. Harbi S. Maouche F. Vaccari A. Aoudia F. Oussadou G.F. Panza D. Benouar 《Soil Dynamics and Earthquake Engineering》2007,27(5):427-447
Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this Capital city, a realistic modelling of the seismic ground motion (SGM) is conducted by using the hybrid method that combines the finite differences method and the modal summation. For this purpose, a complete database of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone [2.25°E–3.50°E, 36.50°N–37.00°N] is performed and an earthquake list, for the period 1359–2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross sections have been built up to model the SGM in the city, caused by the 1989 Mont-Chenoua and the 1924 Douéra earthquakes. Synthetic seismograms and response spectral ratio is produced for Algiers, and they show that the soft sediments in Algiers centre are responsible of the noticed amplification of the SGM. 相似文献
188.
The Tibesti massif, one of the most prominent features of the Sahara desert, covers an area of some 100,000 km2. Though largely absent from scientific inquiry for several decades, it is one of the world’s major volcanic provinces, and
a key example of continental hot spot volcanism. The intense activity of the TVP began as early as the Oligocene, though the
major products that mark its surface date from Lower Miocene to Quaternary (Furon (Geology of Africa. Oliver & Boyd, Edinburgh
(trans 1963, orig French 1960), pp 1–377, 1963)); Gourgaud and Vincent (J Volcanol Geotherm Res 129:261–290, 2004). We present here a new and consistent analysis of each of the main components of the Tibesti Volcanic Province (TVP), based
on examination of multispectral imagery and digital elevation data acquired from the Advanced Spaceborne Thermal Emission
and Reflection Radiometer (ASTER). Our synthesis of these individual surveys shows that the TVP is made up of several shield
volcanoes (up to 80 km diameter) with large-scale calderas, extensive lava plateaux and flow fields, widespread tephra deposits,
and a highly varied structural relief. We compare morphometric characteristics of the major TVP structures with other hot
spot volcanoes (the Hawaiian Islands, the Galápagos Islands, the Canary and Cape Verdes archipelagos, Jebel Marra (western
Sudan), and Martian volcanoes), and consider the implications of differing tectonic setting (continental versus oceanic),
the thickness and velocity of the lithosphere, the relative sizes of main volcanic features (e.g. summit calderas, steep slopes
at summit regions), and the extent and diversity of volcanic features. These comparisons reveal morphologic similarities between
volcanism in the Tibesti, the Galápagos, and Western Sudan but also some distinct features of the TVP. Additionally, we find
that a relatively haphazard spatial development of the TVP has occurred, with volcanism initially appearing in the Central
TVP and subsequently migrating to both the Eastern and Western TVP regions.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
189.
低序次断裂是地壳变形的直接产物,具有丰富的构造变形信息,经过转换的低序次构造。形式多样,图案复杂,是构造研究的重要对象,也是地表稳定性研究的重要基础。利用香港地区航空雷达图像资料,提取其中低序次构造的弱信息,建立转换变形模型,以分析区内不稳定地表的构造背景。区内北东向断裂是主要构造,其右行剪切形成一系列低序次R面,P面,R^1面构造,在雷达图像上表现为线性弱信息并且与微地貌发育有关。利用线性构造增强,提取技术和低序次构造组合分析方法,结合野外地质调查,确定马鞍山地区EW向的张性破裂是NE向张剪断裂的转换,是造成马鞍山滑坡的重要地质因素。 相似文献
190.
断裂构造研究进展对工程地质学的启示 总被引:4,自引:0,他引:4
在长期地质作用下形成的岩体和岩体结构是工程地质学研究的基本内容,它们的形成和演化主要受控于构造作用,而系统地解析体所经历的构造作用是认知岩体结构,抽象和概括岩体工程地质模型的突破口,因此,重视和应用现代构造地质学研究的新理论,新方法必将会对岩体工程地质学研究起着重要的指导意义。本文系统总结了与工程地质研究相关的现代构造地质学理论和思维观的研究进展,在此基础上分析了这些理论方法对工程地质工作的启示和指导意义,希望起到抛砖引玉的作用。 相似文献