锦江水库坝址③号断裂构造破碎带地质特征及其对堤坝安全性的影响     

黄成炽  黄维旺  李志勤 《四川地质学报》2003,23(2):109-111

通过野外地质调查和地球化学探测成果，结合区域地质发展史，论述锦江水库③号断裂构造破碎带的地质特征及其对建筑物的影响。  相似文献   

生态交界带特征与动态变化机理分析   总被引：2，自引：0，他引：2  

张理华  周秉根  万荣荣 《地域研究与开发》2003,22(1):59-61

文章论述了生态交界带是两个以上生态系统交接的过渡带，它具有特有的生态系统结构，生态交界带生态系统的结构，功能和物质，能是以及信息的交流与相邻生态系统有密切的联系，但又表现出明显的异质性，其动态变化机理显示生态交界带内物质，能量和信息的均衡状况。  相似文献   

A millennial-scale record of Holocene tsunamis on the Kronotskiy Bay coast, Kamchatka, Russia     

Tatiana K PineginaJoanne Bourgeois  Lilia I BazanovaIvan V Melekestsev  Olga A Braitseva 《Quaternary Research》2003,59(1):36-47

Deposits from as many as 50 large tsunamis during the last 7000 years are preserved on the Pacific coast of the Kamchatka Peninsula near the mouth of the Zhupanova River, southern Kronotskiy Bay. These deposits are dated and correlated using Holocene marker tephra layers. The combined, preserved record of tsunami deposits and of numerous marker tephras on Kamchatka offers an unprecedented opportunity to study tsunami frequency. For example, from the stratigraphy along southern Kronotskiy Bay, we estimate frequency of large tsunamis (>5 m runup). In the last 3000 years, the minimum frequency is about one large tsunami per 100 years, and the maximum about one large tsunami per 30 years; the latter frequency occurred from about 0 to 1000 A.D. This time interval corresponds to a period of increased seismicity and volcanic activity that appears to be recorded in many places on the Kamchatka Peninsula.  相似文献   

Copper-Polymetal Metallogenic Series and Prospecting Perspective of Eastern Section of Gangdise   总被引：1，自引：0，他引：1  

ZhengYouye XueYingxi GaoShunbao 《中国地质大学学报(英文版)》2003,14(4):349-355

Geological, geophysical, geochemical and remote sensing comprehensive studies show that big ore-prospecting potentiality is contained in the eastern section of the Gangdise Mountains, Tibet.There are various mineralization types with dominant types of porphyry and exhalation. According to their relations with tectonic evolution, they are divided into four kinds of metallogenic series as follows:magnmtic type (Cr, Pt, Cu, Ni) and exhalation type (Cu, Pb, Zn, Ag) ore deposit series related to Neo-Tethys oceanic crust subduction action (125-96 Ma); epithermai type (Au, Ag, Pb, Zn, Sb), altered fractured rock type (Cu, Mo) and skarn rock type (Cu) ore deposit series related to arc-continental collision; porphyry type (Cu, Mo), cryptoexplosion breccia type (Cu, Au, Pb, Zn), shear zone type (Au, Ag, Sb) and skarn rock type (Cu, Fe) ore deposit series with relation to post-orogenic extensional strike-slip. From subductive complex to the north, zoning appears to be crystallization differentiation type (segregation type)-shear zone type (altered rock type)-skarn rock type, epithermai type-porphyry type-porphyry type and exhalation type-exhalation type-hydrothermai filling-replacement type.The ore deposit is characterized by multi-places from the same source, parity and multi-stage, hypabyssal rock from the deep source and poly genetic compound as a whole.  相似文献   

从成矿和变形时代的不耦合现象探讨康古尔金矿的成因   总被引：5，自引：0，他引：5  

陈文  韩春明  张彦  刘新宇 《地球学报》2003,24(6):579-583

位于塔里木盆地北缘的康古尔金矿出露于秋格明塔什-黄山巨型韧性剪切带中部，长期以来被当作剪切带型金矿加以研究。通过初步的同位素年代学研究却发现了成矿和变形时代的不耦合现象：康古尔金矿成矿时代在290Ma左右，而秋格明塔什-黄山韧性翦切带剪切变形时代在225～236Ma。如果认定康古尔金矿成矿作用发生在海西期，则发生于印支中-晚期的韧性剪切变形作用不仅不是康古尔金矿成矿作用的主因，而且对金矿的改造作用也是有限的。因此，康古尔金矿不能被称为剪切带型金矿。  相似文献   

Use of accessory zircon for the quantification of volume changes in ductile shear zones cutting plutonic rocks     

Robert Sturm  Hans Peter Steyrer 《Chemie der Erde / Geochemistry》2003,63(1):31-54

  相似文献   

Assessing selected natural and anthropogenic impacts on freshwater lens morphology on small barrier Islands: Dog Island and St. George Island, Florida, USA   总被引：3，自引：2，他引：1  

James C. Schneider  Sarah E. Kruse 《Hydrogeology Journal》2006,14(1-2):131-145

Abstract The freshwater lens morphologies of the barrier islands Dog Island and St. George Island on the panhandle coast of Florida (FL), USA, are controlled to varying degrees by both natural and anthropogenic factors. Variable-density groundwater flow models confirm that spatial variability of recharge values can account for the observed lens asymmetry on these islands. The depth to the base of the lens does not vary significantly seasonally. Human development has altered recharge patterns in some areas, locally thinning the freshwater lens. Aqueduct water supply to St. George Island represents 7–25% of natural recharge; higher recharge rates are required to simulate the lens on St. George Island than on Dog Island. On both islands, coastal erosion rates are sufficiently rapid that the freshwater lens may not be in equilibrium with current boundary conditions.

---

Resumen Las morfologías de los lentes de agua dulce en las islas de barrera: Islas Dog y St. George, en la costa alargada y estrecha de Florida, EUA, están controladas en diferentes grados por factores antropogénicos y naturales. Los modelos de flujo con densidad variable del agua subterránea, confirman que la variabilidad espacial de los valores de recarga, pueden ser la causa de la asimetría observada en los lentes de estas islas. La profundidad hasta la base de los lentes no varía significativamente con las estaciones climáticas. El desarrollo humano ha alterado las tendencias de recarga en algunas áreas, causando adelgazamiento local de los lentes de agua dulce. El abastecimiento de agua del acueducto en la Isla St. George, representa entre 7% y 25% de la recarga natural; por otro lado se necesitan cantidades mayores de recarga para simular los lentes en la Isla St. George que en la Isla Dog. En ambas islas, las tasas de erosión costera son tan rápidas, que las lentes de agua dulce podrían no estar en equilibrio con las condiciones actuales de frontera.

---

Résumé La morphologie des lentilles deau douce des îles de Dog et de St. George, situés dans le district côtier de Florida-Etats Unis est contrôlé dans une mesure variable par des facteurs naturelles et humaines. Les modèles découlement à densité variable des eaux souterraines confirment que la variation spatiale de la recharge peut expliquer les asymétries observées des lentilles des cettes îles. La profondeur des lentilles ne présente pas des variations saisonnières importantes. Les activités humaines ont modifié la recharge dans certaines zones en amincissant localement les lentilles deau douce. Lalimentation en eaux de lîle de St. George représente 7–25% de la recharge naturelle; pour simuler les lentilles de lîle de Dog il a été nécessaire dintroduire des valeurs plus élevées de la recharge par rapport aux ceux utilisés pour lîle de St. George. Pour les deux îles lérosion côtière est assez rapide ainsi que les lentilles de eau douce ne sont pas en équilibre avec les conditions à la frontière.

  相似文献   

Probing the history of the Mathematician paleoplate using surface waves     

Yu J. Gu   《Tectonophysics》2006,424(1-2):41-51

This paper investigates the shear velocity structure under the northern East Pacific Rise at the latitude range of 9–18°N, using intermediate-period Rayleigh and Love waves. The selected ocean-bottom seismic records provide source–receiver paths that ideally constrain the lithospheric mantle structure beneath the southern Rivera plate and the Mathematician paleoplate. The Rayleigh wave data infer a relatively thin ( 30 km) lithosphere under the eastern side of the present-day East Pacific Rise. The associated shear velocities are consistent with existing models of oceanic mantle beneath this region, and the estimated plate age of 2–3 million years agrees with results from magnetic dating. The west of the rise axis is characterized by a thicker and faster lithosphere than the eastern flank, and such structural differences suggest the presence of a relatively old Mathematician paleoplate. The discontinuous change in mantle structure across the East Pacific Rise spreading center are observed in both isotropic and anisotropic velocities. The young oceanic lithosphere east of the rise axis shows strong polarization anisotropy, where the dominant orientation of crystallographic axes roughly parallels the spreading direction. However, the western flank of the rise axis is approximately isotropic, and the lack of anisotropy suggests complex deformation mechanisms associated with earlier episodes of ridge segmentation, propagation and dual-spreading on and around the Mathematician paleoplate.  相似文献   

首都圈及山西断陷带北部地壳垂直形变与地震危险性分析   总被引：3，自引：2，他引：1  

韩月萍  杨国华  马庆尊 《华北地震科学》2003,21(3):8-13

根据首都圈地区及山西断陷带精密水准复测资料,分析了近十年来地壳垂直形变状态与特征。结果表明,研究区的东北区域表现为整体下降,下降速率约2～4mm／a;但“北升南降”的运动格局基本没有改变。太行山以西至山西断陷带的东侧地区为整体隆升。隆升速率最大近8mm／a。运动的时空分布从“南快北慢”整体上升的特征,逐步转变为“北升南降”的有升有降的特征。西区上述运动性质发生变化是以2001年为分界线,同时在延怀盆地及其附近区域形成了四象限分布的形变图像。但这一图像从规模和量级上都小于大同地震前的变形。山西断陷带北部的运动表现为断陷型的垂直运动,整体呈下降趋势,运动速率为4～6mm／a。上述特征表明监测区未来2～3年内发生6级以上地震的可能性不大。  相似文献   

泥河湾保护区地貌特征与地质灾害   总被引：4，自引：0，他引：4  

牛平山  杨小荟  李铎 《地理与地理信息科学》2003,19(6):107-111

根据泥河湾保护区实地调查,黄土台地、黄土沟梁和河谷地貌是发育在“泥河湾层”及其覆地层上的主要地貌类型,其形态特征和形态测量反映了该区流水地貌的现代演化特征。伴随流水地质作用与地貌演化发生的水土流失、泥石流、崩塌和地面塌陷等地质灾害危及保护区的地层剖面。笔者认为该区域地质灾害是多种致灾因素造成的,其中的主导因素是气候、植被和人为因素,通过控制植被因素可以改变目前的地质环境状况。  相似文献