The stress state near Spanish Peaks,colorado determined from a dike pattern   总被引：1，自引：0，他引：1  

Otto H. Muller  David D. Pollard 《Pure and Applied Geophysics》1977,115(1-2):69-86

The radial pattern of syenite and syenodiorite dikes of the Spanish Peaks region is analysed using theories of elasticity and dike emplacement. The three basic components of Odé's model for the dike pattern (a pressurized, circular hole; a rigid, planar boundary; and uniform regional stresses) are adopted, but modified to free the regional stresses from the constraint of being orthogonal to the rigid boundary. Dike areal density, the White Peaks intrusion, the strike of the upturned Mesozoic strata, and the contact between these strata and the intensely folded and faulted Paleozoic rocks are used to brient the rigid boundary along a north-south line. The line of dike terminations locates the rigid boundary about 8 km west of West Peak. The location of a circular plug, Goemmer Butte, is chosen as a point of isotropic stress. A map correlating the location of isotropic stress points with regional stress parameters is derived from the theory and used to determine a regional stress orientation (N82E) and a normalized stress magnitude. The stress trajectory map constructed using these parameters mimics the dike pattern exceptionally well. The model indicates that the regional principal stress difference was less than 0.05 times the driving pressure in the West Peak intrusion. The regional stress difference probably did not exced 5 MN/m².  相似文献   

Volcanoes as possible indicators of tectonic stress orientation — Aleutians and Alaska     

Kazuaki Nakamura  Klaus H. Jacob  John N. Davies 《Pure and Applied Geophysics》1977,115(1-2):87-112

A new method for obtaining from volcanic surface features the orientations of the principal tectonic stresses is applied to Aleutian and Alaskan volcanoes. The underlying concept for this method is that flank eruptions for polygenetic volcanoes can be regarded as the result of a large-scale natural magmafracturing experiment. The method essentially relies on the recognition of the preferred orientation of radial and parallel dike swarms, primarily using the distribution of monogenetic craters including flank volcanoes. Since dikes tend to propagate in a direction normal to the minimum principal stress (T-axis), the method primarily yields the direction of the maximum horizontal compression (MHC) of regional origin. The direction of the MHC may correspond to either the maximum (P-axis) or intermediate (B-axis) principal stress.The direction of MHC obtained at 20 volcanoes in the Aleutian arc coincides well with the direction of convergence between the Pacific and North American plates. This result provides evidence that in the island arc the inferred direction of MHC is parallel to the maximum principal tectonic stress. In the back-arc region, general E-W trends of MHC are obtained from seven volcanic fields on islands on the Bering Sea shelf and the mainland coast of Alaska. These volcanic fields consist mostly of clusters of monogenetic volcanoes of alkali basalt. In the back-arc region, the trends of MHC may correspond to an E-W intermediate, a vertical maximum, and a N-S minimum principal stress.Implications for the tectonics of island arcs and back-arc regions are: (1) volcanic belts of some island arcs, including the Aleutian arc, are under compressional deviatoric stress in the direction of plate convergence. It is improbable that such arcs would split along the volcanic axis to form actively spreading marginal basins. (2) This compressional stress at the arc, probably generated by underthrusting, appears to be transmitted across the entire arc structure, but is apparently replaced within several hundred kilometers by a stress system characterized by horizontal extension (tensional deviatoric stress) in the back-arc region. (3) The volcanoes associated with these two stress systems differ in type (polygenetic vs. monogenetic) and in the chemistry of their magmas (andesitic vs. basaltic). These differences and the regional differences in orientation of the principal tectonic stresses suggest that the back-arc stress system has its own source at considerable depth beneath the crust.Lamont-Doherty Geological Observatory Contribution No. 2503.  相似文献   

某堤防工程中防渗墙对地下水运动规律影响的初步分析   总被引：1，自引：0，他引：1  

许季军  肖利  张伟  吴昌瑜 《岩土力学》2004,25(Z2):524-530

在1998年之后,长江堤防部分堤段采用了垂直防渗墙措施来处理堤身和堤基中存在的渗流隐患问题,但与此同时,也有人担心防渗墙实施后,会影响原有的江水与地下水之间补给排泄关系而带来新的环境问题.本文将以某实施了防渗墙的堤段为例,采用GMS软件中的MODFLOW计算模块模拟分析临江地层中地下水与江水的动态互动关系,并重点讨论了防渗墙实施后对这种关系的影响,分析结果认为,防渗墙实施后一般不会带来新的地下水环境问题.  相似文献   

西昆仑新藏公路118～323km段基性、酸性岩脉K—Ar年龄   总被引：3，自引：1，他引：3  

计文化周辉  李亚民 《地质通报》2005,24(3):243-245

在西昆仑西段新藏公路沿线广泛发育数量众多的岩脉，野外出露有煌斑岩脉、辉绿岩脉、闪长岩脉、花岗岩脉。对以上岩脉进行了全岩K-Ar同位素测年，其侵位年龄与该区的地质构造事件有很好的对应关系：辉绿岩脉273～280Ma的侵位年龄对应着弧后扩张的时间，闪长岩脉和花岗岩脉230～244Ma的侵位年龄对应着碰撞造山的时间。  相似文献   

堤防工程风险评价体系研究   总被引：1，自引：0，他引：1  

王亚军  吴昌瑜  任大春 《岩土工程技术》2006,20(1):1-8

分析了堤防系统的层次性及模糊性,在此基础上建立了堤防工程风险评价系统指标体系和评价结构模型。结合FCT(Fuzzy Consistency Theorem)及AHP(Analytic Hierarchy Process)定义了模糊一致空间,实现了基于模糊一致矩阵的权重反演。针对各典型护岸段,通过加固前江堤系统风险评价的结论,实现了护岸工程的风险等级划分,进而按照局部与整体加固两种情况完成了加固后江堤系统的风险评价。  相似文献   

西准噶尔东部碱性花岗岩体侵位机理的岩浆动力学初步探讨   总被引：1，自引：0，他引：1  

杨富贵  洪文兴 《矿物学报》1998,18(4):411-416

运用岩浆动力学原理探讨了西准噶尔东部碱性花岗岩浆侵位的驱动力、上升通道、通道最小临界宽度和定位过程。指出：碱性花岗岩体是由其岩浆主要在区域性挤压应力作用下,沿深大断裂以最小临界宽度1．33～301m的脉状上升,并在地壳浅部发生气球膨胀和岩墙扩张．定位于与区内深大断裂有关的次级张性裂隙发育部位后形成的。  相似文献   

桂西北晚古生代地层中的沉积灰岩墙研究进展   总被引：8，自引：12，他引：8  

彭阳  胡贵昂陆刚章雨旭  乔秀夫 《地质论评》2004,50(6):613-619,i005

桂西北晚古生代地层中近直立的二叠纪、三叠纪沉积灰岩墙与围岩时代相差最大超过80Ma(中二叠统茅口组灰岩墙插入中泥盆统东岗岭组中)，有人推测岩墙至少切穿整个石炭系、是海底扩张造成的巨型张裂隙；有人认为它是古构造间断面上古褶皱轴面裂隙充填。但这两种认识都有无法解释的矛盾。笔者识别出沉积灰岩墙内的变形平行层理和垂直贯入层理为地震灾变事件记录，认为沉积灰岩墙是地震液化沉积物流贯入地裂缝形成，是强地震事件在软硬岩层中的不同响应。同时发现与同沉积断裂伴生的台地边缘角砾岩是震裂岩、并有同期斜坡相塌积砾屑灰岩和盆地浊积岩(夹多层玄武岩)，从而揭示右江盆地内二叠纪—早三叠世火山—构造—地震—沉积系统、并初步解释了沉积灰岩墙成因。沉积灰岩墙表明右江盆地晚古生代有多个地震活跃期，灰岩墙与围岩的时间差标志多期局域构造活动。从而质疑早石炭世一中二叠世“右江盆地为稳定碳酸盐岩台地阶段”，进一步的深入研究将可能引起地层和构造关系的重新调整，进而对右江盆地演化和全球超大陆裂解提出重要证据。  相似文献   

A comparison between subaerial and submarine eruptions at Kilauea Volcano, Hawaii: implications for the thermal viability of lateral feeder dikes     

Elisabeth A. Parfitt  Tracy K. P. Gregg  Deborah K. Smith 《Journal of Volcanology and Geothermal Research》2002,113(1-2)

Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre.  相似文献   

综合物探方法在中坊水库坝体隐患勘查中的应用   总被引：1，自引：0，他引：1  

龚育龄  汤洪志  王良书  刘庆成  莫撼  郭令智 《水文地质工程地质》2002,29(1):49-51

在江、河、湖堤防及水库坝体隐患的勘查中，物探方法以其轻便、快捷的特点被广泛使用。中坊水库是江西省广昌县境内的一个中型水库，近年来坝体漏水现象较严重。为了查明隐患，本文采用探地雷达、高密度电阻率法、自然电位法和激发极化法等综合物探方法。对坝体进行勘查，基本查清了水库漏水地段及漏水通道位置，取得了良好的勘查效果。  相似文献   

关于辽西北票地区兴隆沟组火山岩时代的再认识   总被引：1，自引：0，他引：1  

邵济安  杨蔚 《地质通报》2008,27(6):912-916

针对近年来关于兴隆沟组火山岩同位素年龄及地层归属方面存在的分歧,通过详细的地质填图已查清,近年报道的2组U-Pb同位素年龄均为贯穿兴隆沟组火山-沉积地层的霏细斑岩脉年龄,兴隆沟组地层仍应归属为下侏罗统.  相似文献