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1.
对青藏东北缘现今块体划分、运动及变形的初步研究 总被引:19,自引:9,他引:10
利用2维非连续变形分析方法(DDA),以位移代替围压作为边界约束力,研究青藏东北缘现今块体划分及其运动变形。根据该地区地质构造及地震活动,以GPS点测量位移作为模拟结果约束点,得出了较合理的块体划分模型和随时间演化的主应变分布图,并把应变高值区与近几年来发生的5级以上地震作对比,得出了研究区内地震危险性可能较大的区域。另外,对模拟的甘青块体与阿拉善块体的边缘带断裂左旋运动做了大概计算。 相似文献
2.
刘峰 《成都信息工程学院学报》2003,18(4):376-380
分组密码是数据通讯中最常用的数据加密方式,以DES为例分析现有分组加密算法的安全隐患,并提出了可变密钥加密和变长密文输出两个新思路,可应用于所有现有分组加密算法以提高安全性,并就该方法的安全性、效率、具体应用做出了分析。 相似文献
3.
四川石棉大水沟独立碲矿床堪称世界首例,其矿体两侧的围岩蚀变较窄,且蚀变带与矿脉及未蚀变岩呈清楚而截然的接触关系。主要围岩蚀变为白云石化、白(绢)云母化、云英岩化及电气石化等。这些蚀变作用分别发生于177.7~165.1Ma和91.71~80.19Ma。蚀变作用过程中SiO2大量析出,Al2O3、TiO2、CaO、MgO、K2O、H2O、CO2、Fe2O3、MnO则有不同程度地带入。与此同时,REE在此过程中包集体迁出,Te、Bi、AS等元素的含量则决定于蚀变作用及其强度,而与原岩无关。 相似文献
4.
矿床谱系是对成矿多样性的理论概括,而成矿多样性又是由不同级别、不同性质的致矿地质异常决定的.本文论述了山东省内生金矿矿床谱系及其致矿地质异常. 相似文献
5.
秦岭凤太矿田层控铅锌(铜)矿床的金属物质、硫和成矿溶液主要来自深部基底的岩石,属海底喷流—沉积成因矿床。从这一理论认识出发可进一步分析控矿地质条件及今后在该区有效地寻找同类矿床。 相似文献
6.
断层相关褶皱理论在准噶尔盆地南缘山前带构造研究的应用 总被引:8,自引:4,他引:4
利用断层相关褶皱的构造几何分析方法,对准噶尔盆地南缘山前复杂构造带内基于地震剖面进行了构造解析,搭建了中、东段的构造轮廓和构造组合样式,认为东段阜康断裂带主要表现为至地表的推覆逆掩。由于位移量大部分转移至地表,阜康断裂带的前陆部分无喜山期构造带;西段造山带内的挤压往前陆方向传递过程中以前列式不断释放其位移量,造成在纵向上呈现三排主要的断层相关褶皱带。根据正演平衡地质剖面制作技术对山前复杂构造区地震剖面反射波的构造识别进行了模拟与探讨。 相似文献
7.
青藏块体东北缘地壳水平运动状态 总被引:10,自引:6,他引:4
应用青藏块体东北缘1999~2003年多期GPS观测资料,计算了不同时段GPS点水平运动速率。通过分析发现:甘青块体可分为东部块体和西部块体,东、西部块体的运动状态存在明显的差异;受2001年11月14日昆仑Ms8.1地震的影响,震后地壳运动状态发生了明显的改变。 相似文献
8.
Abstract The high-grade metamorphic rocks of southern Brittany underwent a complex tectonic evolution under various P-T conditions (high-P, high-T), related to stacking of nappes during Palaeozoic continentcontinent collision. The east to west thrusting observed in the whole belt is strongly perturbed by vertical movements attributed to the ascent of anatectic granites in the high-T area. The field reconstruction of subvertical, closed elliptical structures in gneisses and migmatites, associated with the subhorizontal, doubly radial pattern of stretching lineation in the mica schists, suggests the existence of an elliptical diapiric body buried at depth beneath the present erosion level. Deformation is associated with a complex P-T evolution partly recorded in aluminous gneisses (kinzigites, e.g. morbihanites). A chronology of successive episodes of mineral growth at different compositions is established by detailed studies of the mineral-microstructure relationships in X-Z sections, using the deformation-partitioning concept (low- and high-strain zones). Several thermometric and barometric calibrations are applied to mineral pairs either in contact or not in contact but in equivalent microstructiiral positions with respect to the deformation history. This methodology provides a continuous microstructural control of P-T variations through time and leads to three P-T-t-d paths constructed from numerous successive P-T estimations. Path 1 is a clockwise retrograde path preserved in low-strain zones, which records general exhumation movements after crustal thickening. Paths 2 and 3 are clockwise prograde/retrograde paths from high-strain zones; they are interpreted and discussed in the light of models of crustal anatexis and upward movement of magma (diapirism). Deformation and P-T effects induced by diapirism can be distinguished from the general deformation-metamorphic history of a belt, and would seem to be produced during a late stage of its history. The present microstructural-petrological approach to defining successive mineral equilibria in relation to progressive deformation steps provides a far more accurate evaluation of the metamorphic evolution than is possible by ‘standard’thermobarometry. 相似文献
9.
C. Giraudi 《第四纪科学杂志》2004,19(6):537-545
The island of Lampedusa lies on the northern edge of the African continental shelf, but during some Quaternary marine lowstands it was joined to the African continent. The study and dating of the aeolian, alluvial, detrital sediments, calcareous crusts and speleothems have established that the climatic–environmental variations recorded on the island can be related chronologically to those known for northern Libya, Tunisia and the Italian peninsula. During the Last Glacial Maximum, phases of Saharan dust accumulation on Lampedusa occurred, and were coeval with dust accumulation in crater lakes and on high mountains in central‐southern Italy, and with phases of glacial advance in the Apennines and in the Alps. During the late Holocene, accumulation of Saharan dust on Lampedusa occurred but there was little accumulation of dust on the northern side of the Mediterranean Sea. With the new data from Lampedusa, it is possible to envisage two different scenarios of atmospheric circulation relating to the Last Glacial Maximum and to the late Holocene. During the Last Glacial Maximum, southerly atmospheric circulation brought rainfall to the southern slopes of the Alps and to the Apennines. During the late Holocene, a prevalent westerly atmospheric circulation became established in the northern Mediterranean. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
The paper provides a new stereo‐analytical method, which is a combination of the stereographic method and analytical methods, to separate finite removable blocks from the infinite and tapered blocks in discontinuous rock masses. The methodology has applicability to both convex and concave blocks. Application of the methodology is illustrated through examples. Addition of this method to the existing block theory procedures available in the literature improves the capability of block theory in solving practical problems in rock engineering. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献