Effect of the chemical composition of the crust on the metamorphic evolution of orogenic wedges   总被引：4，自引：0，他引：4  

B. Goffé  R. Bousquet  P. Henry  X. Le Pichon 《Journal of Metamorphic Geology》2003,21(2):123-141

Petrological data provide a good record of the thermal structure of deeply eroded orogens, and, in principle, might be used to relate the metamorphic structure of an orogen to its deformational history. In this paper, we present two‐dimensional thermal modelling of various subduction models taking into account varying wedge geometry as well as variation of density and topography with metamorphic reactions. The models clearly show that rock type accreted in the wedge has important effects on the thermal regime of orogenic wedges. The thermal regime is dominated by radiogenic heat production. Material having high radioactive heat production, like the granodioritic upper crust, produces high temperature metamorphism (amphibolitic conditions). Material with low radioactive heat production results in low temperature metamorphism of greenschist or blueschist types depending on the thickness of the wedge. Application of this model to seemingly unrelated areas of the Central Alps (Lepontine Dome, Grisons) and Eastern Alps (Tauern Window) explains the coexistence and succession of distinct Barrovian and blueschist facies metamorphic conditions as the result of a single, continuous tectonic process in which the main difference is the composition of the incoming material in the orogenic wedge. Accretion of the European upper continental crust in the Lepontine and Tauern Domes produces Barrovian type metamorphism while accretion of oceanic sediments results in blueschist facies metamorphism in the Valaisan domain.  相似文献   

岷县高炮防雹效果分析   总被引：1，自引：1，他引：1  

渠永兴  孙旭映  阎敬泽 《干旱气象》2003,21(2):37-38,41

根据甘肃省岷县1959-1998年的年雹日和受灾面积、历史资料，用统计学方法分析检验高炮防雹效果。经序列、wolch检验发现，高炮防雹后“年雹日”减少32．8％，“受灾面积”减少33．6％，显著性水平达到0．05．可信度达95％以上。  相似文献   

基于灵敏度分析的结构损伤识别中的传感器优化配置   总被引：5，自引：0，他引：5  

刘晖  瞿伟廉  袁润章 《地震工程与工程振动》2003,23(6):85-90

本文提出了结构损伤识别中的传感器测点优化配置的方法。该方法是通过仅考虑结构刚度变化的结构特征灵敏度分析，以结构各自由度的损伤信息为条件，计算出结构的Fisher信息阵，并且考虑到Fisher信息阵的逆阵可能不存在，而将Fisher信息阵对应于每个自由度进行分解，通过计算每个分解的Fisher信息阵的迹而确定每个自由度含有的损伤信息的多少，从而从结构的全部自由度中去掉那些含损伤信息少的自由度。建立直接利用结构不完整的实测模态来定位结构的损伤，避免结构模态扩阶带来不必要的误差。最后，通过数值算例表明，该方法能有效地识别出结构的损伤。  相似文献   

华北板块南缘栾川群研究   总被引：7，自引：0，他引：7  

石铨曾  陶自强 《华北地质矿产杂志》1996,11(1):51-59

栾川群出露于东秦岭北部。在栾川群分布区域，古华北板块不同时代的地层往南逆冲，构成北秦岭的太华推覆体。栾川群存在于该推覆体内部的特定逆冲岩席之中，沿这一逆冲岩席追索，确定古华北板块南缘的栾川群是连续沉积的，而受后期推覆构造的改造，栾川群在推覆体前缘的分布是断续相连的。根据地层之间的接触关系、岩浆活动、沉积作用的研究，对栾川群的划分提出了新的看法，认为栾川群由三川组、南泥湖组、煤窑沟组及大红口组构成。栾川群形成于震旦纪晚期，由湖坪及潮下斜坡等滨浅海沉积物构成。栾川群的岩浆岩为具双众数特征的岩套，具典型的大陆裂谷岩浆岩特征。并认为中元古代以来，古华北板块南缘处于裂陷拉张环境。早期的裂陷形成了熊耳群、汝阳群、官道口群及竞坪群，晚期裂陷的过程形成了栾川群、陶湾群，其进一步发育导致以二郎坪群为代表的洋壳生成。  相似文献   

中国硫的供求现状和展望   总被引：1，自引：0，他引：1  

范可正  林乐 《化工矿产地质》1996,18(4):317-324

从工业和农业两个方面供需现状分析，中国目前硫的供需基本平衡，且供略大于求。展望２０００年，中国硫的供求关系将出现缺口，需进一步开拓硫的潜在资源。从总体上看，目前中国土壤供硫情况尚好，但一些地区已开始出现缺硫和严重缺硫的状况，预测今后土壤缺硫状况将会加剧，希望各有关部门对此应给予充分注意  相似文献   

Electron microscopy study of the sakhaite from endogenous borate deposit in Hunan, China     

LIU Xiangwen    YANG Guangming  ZOU Huamin  QU Jing & ZHAO Wenxia . Graduate School  China University of Geosciences  Wuhan  China  . Test Center  China University of Geosciences  Wuhan  China  . Physics  Technology College  Wuhan University  Wuhan  China  . Test Center  Zhongshan University  Guangzhou  China 《中国科学D辑(英文版)》2004,47(3)

Sakhaite was first discovered by Ostrovskaya, Pertsev and Nikitina at Siberia in the former Soviet Union. By using the X-ray diffraction technique, they proved that the crystal system of sakhaite was cubic (a = 1.464 nm), its possible space groups were Fm3m, F432, F43m, Fm3, F23, and its crystal chemical for-mula was Ca48Mg16(CO3)16(BO3)28Cl4(OH)8 4H2O[1]. Chichagov, Simonov and Belov studied the crystal structure of synthetic sakhaite and determined that its space group was F4132, …  相似文献   

陕北砂黄土区公路地质灾害及防治对策   总被引：8，自引：0，他引：8  

张永双  曲永新  何锋 《中国地质灾害与防治学报》2004,15(2):35-38

中国西北黄土的颗粒组成具有明显的地带性分布规律，自NW向SE可依次划分为砂黄土带、典型黄土带和粘黄土带。黄土高原北部地质灾害综合调查表明，砂黄土区公路地质灾害的主要类型包括黄土边坡滑塌灾害、路堤裂陷灾害、路桥变形和冲蚀灾害等。根据试验测试分析结果，公路地质灾害的形成主要受黄土本身的物质组成、结构及力学性质控制，人类工程活动的盲目性是诱发地质灾害的重要因素。文章在砂黄土公路地质灾害特征分析的基础上，提出加强边坡防护和冲蚀灾害防治是公路地质灾害防治的两个基本途径，并给出了针对性的防治对策。这不仅对该地区的公路建设具有重要的指导作用，而且对其它生命线工程如铁路、输油气管道、渠道等也具有重要的借鉴意义。  相似文献   

Field and petrological evidence for a Late Palaeozoic (Upper Carboniferous–Permian) age of the Erfaulet orthogneiss (Gran Paradiso,western Alps)     

Benjamin Le Bayon  Michel Ballèvre 《Comptes Rendus Geoscience》2004,336(12):1079-1089

In the Gran Paradiso massif (western Alps), the boundary between the Erfaulet orthogneiss and the overlying metasediments (Money Complex) is interpreted as a Late Palaeozoic intrusive contact. Major arguments in favour of this hypothesis are: (i) the obliquity of the sedimentary layering with respect to the contact; (ii) the presence of aplitic dykes within the Money Complex; (iii) the lack of a mylonitic zone; and (iv) rare relics of an early generation of garnet in the Money metasediments, interpreted as evidence of the contact metamorphism of the Erfaulet granite. To cite this article: B. Le Bayon, M. Ballèvre, C. R. Geoscience 336 (2004).  相似文献   

Modélisation morphodynamique cross-shore d'un estran vaseux     

Benoı̂t Waeles  Pierre Le Hir  Ricardo Silva Jacinto 《Comptes Rendus Geoscience》2004,336(11):1025-1033

Numerical experiments were performed to simulate the profile evolution of an intertidal mudflat with a 1D cross-shore morphodynamical model. First, the hydrodynamical forcing is a cross-shore tidal current due to semi-diurnal variations of the free surface elevation at the open boundary. Further, considering the conservation of the action density of surface gravity waves, a wave height (and resulting bottom shear stress) calculation is added to the morphodynamical model. Results of the numerical experiments show that the shape of the profile reaches equilibrium. The mudflat progrades continually when the forcing is tide only, whereas it can be steady under the simultaneous action of tide and waves. To cite this article: B. Waeles et al., C. R. Geoscience 336 (2004).  相似文献   

描述黄河中下游河道横断面形态的新指标     

孙赞盈  曲少军  苏运启  杨明 《山地学报》2004,22(2):161-164

描述河流横断面的窄深程度,无非是用来衡量它对过流能力和输沙能力的影响大小,及其在河流地貌方面的时空上的调整变化。回顾总结了以往描述横断面形态的常用指标,包括河相系数、宽深比,或湿周与平均水深的比值,指出这几种指标在描述黄河中下游河道时所存在的共同缺点:(1)缺乏物理意义;(2)不能真正代表断面的窄深程度;(3)明显的夸大了宽浅和窄深断面的差别。从表称流量的概念出发,作者认为,应该使用具有明确物理意义的等面积的表称流速来描述断面形态。如果用表称流速来衡量黄河下游河南和山东河道的断面形态的差别,就会发现,断面形态的不同,其对过流能力的影响不过1:2,远不象河相系数和宽深比所描述的达到1:6甚至1:11那样的悬殊程度;黄河下游河道主槽“多来多排”的主要影响因素是表称流速。  相似文献