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31.
西准噶尔克拉玛依蛇绿混杂岩中的石榴角闪岩 总被引:5,自引:5,他引:0
本文报道在准噶尔地区发现的石榴角闪岩,该岩石产在克拉玛依蛇绿混杂岩带的百口泉地区.石榴角闪岩主要由钙质角闪石、富钠斜长石和黝帘石组成,含少量钛铁矿、绿帘石、绿泥石、榍石、石榴石、普通辉石、金红石、磷灰石、钠长石、石英和锆石.石榴石中常包裹磷灰石、金红石、钛铁矿、石英和锆石.黝帘石 富钠斜长石组合中出现少量钙铝榴石残余.百口泉石榴角闪岩中石榴石的化学组成特征以及其中出现的金红石-钛铁矿-磷灰石-石英-锆石包体组合说明,该岩石不是异剥钙榴岩退变质的产物,而是榴辉岩退变的产物(辅助证据包括二辉橄榄岩中发育的辉石出溶结构和辉石塑性变形特征).百口泉石榴角闪岩至少记录了四个阶段:石榴石-单斜辉石-金红石-磷灰石-石英-锆石组成的阶段Ⅰ(可能为榴辉岩相),普通辉石-钛铁矿-磷灰石-角闪石组成的退变阶段Ⅱ,角闪石-斜长石-榍石-钛铁矿构成的阶段Ⅲ(角闪岩相),以及绿帘石-石英-绿泥石构成的绿片岩相变质阶段Ⅳ.尽管上述演化历史存在一些不确定性,石榴角闪岩的发现为深入研究西准噶尔地区古生代洋壳俯冲带的性质及其演化过程提供了新的物质基础. 相似文献
32.
随着"数字国土工程"的启动,国土资源信息化管理得到了各级政府的高度重视,而土地利用数据库的建设是"数字国土工程"中基础数据库的重要组成部分.文章通过分析桌面地理信息系统MapGIS的功能,结合赣州市土地利用现状图的数字化实践,总结出用MapGIS进行土地利用数据库建库的流程,并对数据库建设中应特别注意的质量问题进行了探讨. 相似文献
33.
花岗岩残积土水土特征曲线的试验研究 总被引:2,自引:1,他引:1
本文采用渗析法测定花岗岩残积土的水土特征曲线,详细介绍了渗析法的试验步骤及注意事项,并对花岗岩残积土的水土特征曲线进行了分析。通过试验得到残积土水土特征曲线,无论是干燥段或是浸湿段,下降都较为平缓。花岗岩残积土的进气值较低,仅为10kPa左右,而土体残余含水量较大,为20%左右,说明花岗岩残积土持水能力较强。文章还对水土特征曲线的滞回圈进行了分析,认为水土特征曲线的滞回圈应该是由多种原因引起的。 相似文献
34.
Jesús M. Mercado Teodoro Ramírez Dolores Corts Marta Sebastin Andreas Reul Begoa Bautista 《Estuarine, Coastal and Shelf Science》2006,69(3-4):459
The changes in the phytoplankton absorption properties during a diurnal cycle were investigated at one station located in the north-western area of the Alborán Sea. The experiment was performed in spring when the water column was strongly stratified. This hydrological situation permitted the establishment of a deep chlorophyll a (chl a) fluorescence maximum (DFM) which was located on average close to the lower limit of the mixed layer and the nutricline. The relative abundance of pico-phytoplankton (estimated as its contribution to the total chl a) was higher in the surface, however, micro-phytoplankton dominated the community at the DFM level. Chl a specific absorption coefficient (a*(λ)) also varied with optical depth, with a* (the spectrally average specific absorption coefficient) decreasing by 30% at the DFM depth with respect to the surface. A significant negative correlation between the contribution of the micro-phytoplankton to the total chl a and a* was obtained indicating that a* reduction was due to changes in the packaging effect. Below the euphotic layer, a* increased three-fold with respect to the DFM, which agrees with the expected accumulation of accessory pigments relative to chl a as an acclimation response to the low available irradiance. The most conspicuous change during the diurnal cycle was produced in the euphotic layer where the chl a concentration decreased significantly in the afternoon (from a mean concentration of 1.1 μg L−1 to 0.7 μg L−1) and increased at dusk when it averaged 1.4 μg L−1. In addition, a* and the blue-to-red absorption band ratio increased in the afternoon. These results suggest that a*(λ) diurnal variability was due to increase in photo-protective and accessory pigments relative to chl a. The variation ranges of a*(λ) at 675 and 440 nm (the absorption peaks in the red and blue spectral bands, respectively) in the euphotic layer were 0.01–0.04 and 0.02–0.10 m2 mg−1 chl a, respectively. Approximately 30% out of this variability can be attributed to the diurnal cycle. This factor should therefore be taken into account in refining primary production models based on phytoplankton light absorption. 相似文献
35.
Effect of Cyclic Loading Frequency on Undrained Behaviors of Undisturbed Marine Clay 总被引:2,自引:0,他引:2
Based on a series of cyclic triaxial tests, the effect of cyclic frequency on the undrained behaviors of undisturbed marine clay is investigated. For a given dynamic stress ratio, the accumulated pore water pressure and dynamic strain increase with the number of cycles. There exists a threshold value for beth the accumulated pore water pressure and dynamic strain, below which the effect of cyclic frequency is very small, but above which the accumulated pore water pressure and dynamic strain increase intensely with the decrease of cyclic frequency for a given number of cycles. The dynamic strength increases with the increase of cyclic frequency, whereas the effect of cyclic frequency on it gradually diminishes to zero when the number of cycles is large enough, and the dynamic strengths at different frequencies tend to the same limiting minimum dynamic strength. The test results demonstrate that the reasons for the frequency effect on the undrained soil behaviors are beth the creep effect induced by the loading rate and the decrease of sample effective confining pressure caused by the accumulated pore water pressure. 相似文献
36.
Lock-release gravity currents with a viscous self-similar regime are simulated by use of the renormalization group(RNG) k - ε model for Reynolds-stress closure. Besides the turbulent regime with initially a slumping phase of a conslant current front speed and later an inviseid self-similar phase of front speed decreasing as t^-1/3(where t is the time measured from release), the viseous self-similar regime is satisfactorily reproduced with front speed decreasing as t^-4/5,consistent with well known experimental observations. 相似文献
37.
38.
A new approach to high-order Boussinesq-type equations with ambient currents is presented. The current velocity is assumed to be uniform over depth and of the same magnitude as the shallow water wave celerity. The wave velocity field is expressed in terms of the horizontal and vertical wave velocity components at an arbitrary water depth level. Linear operators are introduced to improve the accuracy of the kinematic condition at the sea bottom. The dynamic and kinematic conditions at the free surface are expressed in terms of wave velocity variables defined directly on the free surface. The new equations provide high accuracy of linear properties as well as nonlinear properties from shallow to deep water, and extend the applicable range of relative water depth in the case of opposing currents. 相似文献
39.
40.
1 .IntroductionTheBohaiGulfisinfestedbyiceinthewholewinter,andoffshorestructuresthereexperiencenotonlywind ,waves ,currentsandearthquake ,butalsoiceloadswhicharecomplicatedbecauseofthedynamicinteractionbetweenicesheetsandstructures.Duanetal.( 2 0 0 0 )hadacomprehensivere viewofthelatestadvancesonice inducedvibration ,fatigueandfractureofoffshorestructures ,payingmuchattentiontothedifferencesinicebreakingmodeanddynamicsofstructuresindifferentice in festedwaters .Theypresentedcriticallythelates… 相似文献