From geometry to dynamics of microstructure: using boundary lengths to quantify boundary misorientations and anisotropy   总被引：1，自引：0，他引：1  

John Wheeler  Z. Jiang  D. J. Prior  J. Tullis  M. R. Drury  P. W. Trimby 《Tectonophysics》2003,376(1-2):19-35

The microstructure of a quartzite experimentally deformed and partially recrystallised at 900 °C, 1.2 GPa confining pressure and strain rate 10⁻⁶/s was investigated using orientation contrast and electron backscatter diffraction (EBSD). Boundaries between misoriented domains (grains or subgrains) were determined by image analysis of orientation contrast images. In each domain, EBSD measurements gave the complete quartz lattice orientation and enabled calculation of misorientation angles across every domain boundary. Results are analysed in terms of the boundary density, which for any range of misorientations is the boundary length for that range divided by image area. This allows a more direct comparison of misorientation statistics between different parts of a sample than does a treatment in terms of boundary number.The strain in the quartzite sample is heterogeneous. A 100×150 μm low-strain partially recrystallised subarea C was compared with a high-strain completely recrystallised subarea E. The density of high-angle (>10°) boundaries in E is roughly double that in C, reflecting the greater degree of recrystallisation. Low-angle boundaries in C and E are produced by subgrain rotation. In the low-angle range 0–10° boundary densities in both C and E show an exponential decrease with increasing misorientation. The densities scale with exp(−θ/λ) where λ is approximately 2° in C and 1° in E; in other words, E has a comparative dearth of boundaries in the 8–10° range. We explain this dearth in terms of mobile high-angle boundaries sweeping through and consuming low-angle boundaries as the latter increase misorientation through time. In E, the density of high-angle boundaries is larger than in C, so this sweeping would have been more efficient and could explain the relative paucity of 8–10° boundaries.The boundary density can be generalised to a directional property that gives the degree of anisotropy of the boundary network and its preferred orientation. Despite the imposed strain, the analysed samples show that boundaries are not, on average, strongly aligned. This is a function of the strong sinuosity of high-angle boundaries, caused by grain boundary migration. Low-angle boundaries might be expected, on average, to be aligned in relation to imposed strain but this is not found.Boundary densities and their generalisation in terms of directional properties provide objective measures of microstructure. In this study the patterns they show are interpreted in terms of combined subgrain rotation and migration recrystallisation, but it may be that other microstructural processes give distinctive patterns when analysed in this fashion.  相似文献   

川北地区岩石反射谱波特征     

刘登忠  陈建平  兰立波 《国土资源遥感》1997,8(1):31-36

四川北部地区既有岩浆岩、变质岩构成的前震旦系结晶变质基底,又有震旦纪以后的沉积盖层,岩石类型十分齐全。本文根据该区的120件岩(矿)石样品反射波谱测试结果,绘制了区内主要岩石类型典型波谱曲线,并对这些波谱曲线进行了初步分析,总结了主要岩石类型的波谱特征,这些岩石波谱特征在西南地区有一定的代表性。  相似文献   

水库地震主震发生时间的预测   总被引：1，自引：2，他引：1  

常宝琦  沈立英 《华南地震》1997,17(2):76-82

水利工程对水库地震的抗震设防要求事先对水为地震进行预测。预测内容包括蓄水后诱发地震的危险性（可能性、）最大震级、最大震的地占紧及不库地震对场址地震动参数的影响。除主震时间的预测外，本文第一作者都曾提出过初步的预测方法。本文认为，水库地震前震波速比异常、非线性灰色模型以及前震系列回归等方法，是预测主震时间的有前途的方法。  相似文献   

Effects of early season defoliation ofAnthyllis cytisoides(a Mediterranean browse species) on further herbivore attack     

Concepción L. Alados  Fernando G. Barroso  Antonio Aguirre  Juan Escós 《Journal of Arid Environments》1996,34(4):455-463

To determine if defoliation of a woody plant affects foraging by folivorous insects, we examined the infection rate (number of leaves damaged per total number of leaves sampled on marked stems) ofAnthyllis cytisoidesunder three experimental treatments: 10, 50 and 90% plant defoliation. Observations were made for three age classes, established by trunk base perimeter (equal to or lower than 11 cm, between 11 and 20 cm, larger than 20 cm). Plants respond positively to artificial defoliation by increasing total vegetative length of the stem and total inflorescence length. This response is most evident in young individuals.Response to herbivory was measured as overall infection rate and also as infection rate by different feeding guilds—chewing, mining, or sucking insects. We found that increased defoliation elicited increased resistance of leaves to insect attack. This was particularly evident in young plants. Different insect guilds respond in different ways. Attack by chewing insects declines with defoliation for all plant age classes; only sucking insects which feed on the oldest plants reduce feeding rate with plant defoliation. Finally, mining insects present the opposite trend in young and senescent plants.  相似文献   

岩体结构统计均质区的划分   总被引：6，自引：0，他引：6  

陈剑平  滕建仁 《地质灾害与环境保护》1996,7(1):19-24

本文介绍由Ｍｉｌｌｅｒ提出的基本概率统计理论的关联表分析，结合施密特投影图研究岩体统计均质区的划分方法。对该法进行了适当的修改，编写了相应的计算机程序。并对三峡永久船闸地区的岩体结构，进行了岩体结构统计均质区的划分，获得了良好的效果。  相似文献   

锦屏Ⅰ级水电站坝区岩体结构面特征研究     

邓荣贵  张倬元 《地质灾害与环境保护》1996,7(1):35-40,53

本文根据锦屏Ⅰ级水电站坝区体结构面野外调资料，对坝区结构面优势方位、间距、张开度、连通率、隙间充填物及形态特征进行了分析，为坝区岩体分类及其物理力学参数的确定提供了重要依据。  相似文献   

变频激电法在四川某金矿中的应用     

扶永铭  王益民 《物探化探计算技术》1996,(S5)

本文介绍了用变频激电法寻找含金硫化物矿体 ,通过对视幅频效应 Fs,和交流视电阻率 ρsf的分析 ,取得了良好的地质效果  相似文献   

黄沙坪矿区岩浆岩及其控矿特征   总被引：14，自引：0，他引：14  

钟正春 《矿产与地质》1996,10(6):400-405

在总结黄沙坪矿区各类岩浆岩特征及其控矿特征的基础上，提出了岩浆岩的演化系列及其成因，认为区内３０１花岗斑岩和３０４花斑岩是多金属矿的主要成矿源岩，而石英斑岩则是区内斑岩铜矿的成矿岩体。  相似文献   

Stability analysis of rock wedges with multiple sliding surfaces     

M. Mauldon  J. Ureta 《Geotechnical and Geological Engineering》1996,14(1):51-66

Summary Although wedge and plane sliding stability analyses are well established in the geotechnical literature, certain geologic environments produce blocks which cannot be adequately modelled as either wedges or plane slides. An example is blocks forming in cylindrically folded sedimentary rocks, where the surface of sliding is neither a single plane nor a double plane but is curved. This type of block may be idealized as a prismatic block with multiple sliding planes, all with parallel lines of intersection. If the sliding planes number three or more, the distribution of normal forces, and hence the factor of safety, is indeterminate. A new analytical model for sliding stability analysis is described in which the distribution of normal forces on the contact planes is chosen to minimize the potential energy of the system. The classic wedge and plane solutions are shown to be special cases of this more general model, which allows determination of the safety factor for any shape of prismatic contact surface. An example from Tennessee concerning a block with a curved sliding surface is described and the factor of safety compared with the standard wedge analysis. It is shown that with three or more contact planes, the safety factor may be significantly lower than that calculated from the wedge model, which provides an upper limit on stability.  相似文献   

内蒙古科尔康油田沙海组储集层的岩石学特征   总被引：1，自引：0，他引：1  

刘林玉  叶俭 《西北地质科学》1997,18(1):46-49

根据碎屑岩铸体薄片和扫描电镜观察分析资料，研究了科尔康油田沙海组储集层的岩石学特征。科尔康油田沙海组储集层的岩石类型主要为岩屑砂岩和岩屑砂砾岩。碎屑岩的岩性特征对沙海组储集层的成岩作用具有显著的影响作用。  相似文献