排序方式： 共有45条查询结果，搜索用时 15 毫秒
21.
22.
The Precambrian basement complex in the southernmost part of North-Central Nigeria is underlain by migmatitic banded gneisses,
granitic intrusions and dykes of dolerite, rhyolite porphyry and pegmatite. The rocks are generally felsic, containing modal
and normative hypersthene, as well as normative corundum. The basement complex has experienced high-grade regional metamorphism
as indicated by the presence of hypersthene and plagioclase of andesine composition. Anatectic melting is suggested by the
occurrence of ptygmatic folds, folded gneissose foliation, numerous quartzo-feldspathic veins and lenses of dark-colured,
micaceous schistose rocks. Geochemically, the rocks have magnesian, calc-alkalic and strongly peraluminous characteristics.
Their overall characteristics suggest derivation from progressive (fractional) partial melting of pelitic rocks during high-grade
regional metamorphism, possibly associated with intense hydrothermal activities. The magnesian characteristics reflect close
affinity to relatively hydrous, oxidizing melts and source regions in settings broadly related to subduction. 相似文献
23.
世界上人口数量超过一亿的国家有11个，分别是中国、印度、美国、印度尼西亚、俄罗斯、巴西、日本、尼日利亚、盂加拉国、巴基斯坦、墨西哥。因为这些国家分布在不同的大洲且数量较多，记忆起来比较困难，而且也容易遗忘。笔者根据学生的特点，总结出一种记忆这11个国家的方法，效果较好，与大家一起分享。 相似文献
24.
二战结束以来，出于政治、经济、人口、市政建设等各种原因考虑，全世界实施迁都的事例并不鲜见，如巴西首都从里约热内卢迁到巴西利亚，尼日利亚首都从拉各斯迁到阿布贾，德国首都从波恩迁到柏林，哈萨克斯坦首都从阿拉木图迁到阿斯塔纳，还有近期的缅甸首都从仰光迁到了彬马那等。另外，还有一些国家也已提出了迁都的动议。韩国继首都“汉城”改名为“首尔”不久后，又将酝酿已久的行政首都迁移问题提上了议事日程，引起了世人的关注。 相似文献
25.
JIMOH Rasheed Olayink TANG Yong LI Jiabiao AWOSIKA Larry Folajimi LI He AKINNIGBAGE Edward Akintoye ADELEYE Adedayo Oluwaseun 《海洋学报(英文版)》2018,37(7):28-40
Multi-beam,sub-bottom and multichannel seismic data acquired from the western Nigerian continental margin are analysed and interpreted to examine the architectural characteristics of the lower parts of the submarine canyons on the margin.The presence of four canyons: Avon,Mahin,Benin,and Escravos,are confirmed from the multi-beam data map and identified as cutting across the shelf and slope areas,with morphological features ranging from axial channels,moderate to high sinuosity indices,scarps,terraces and nickpoints which are interpreted as resulting from erosional and depositional activities within and around the canyons.The Avon Canyon,in particular,is characterised by various branches and sub-branches with complex morphologies.The canyons are mostly U-shaped in these lower parts with occasional V-shapes down their courses.Their typical orientation is NE–SW.Sedimentary processes are proposed as being a major controlling factor in these canyons.Sediments appear to have been discharged directly into the canyons by rivers during the late Quaternary low sea level which allows river mouths to extend as far as the shelf edge.The current sediment supply is still primarily sourced from these rivers in the case of the Benin and Escravos Canyons,but indirectly in the case of the Avon and Mahin Canyons where the rivers discharge sediments into the lagoons and the lagoons bring the sediments on to the continental shelf before they are dispersed into the canyon heads.Ancient canyons that have long been buried underneath the Avon Canyon are identified in the multichannel seismic profile across the head of the Avon Canyon,while a number of normal faults around the walls of the Avon and Mahin Canyons are observed in the selected sub-bottom profiles.The occurrence of these faults,especially in the irregular portions of the canyon walls,suggests that they also have some effect on the canyon architecture.The formation of the canyons is attributed to the exposure of the upper marginal area to incisions from erosion during the sea level lowstand of the glacial period.The incisions are widened and lengthened by contouric currents,turbidity currents and slope failures resulting in the canyons. 相似文献
26.
近日,中国电力工程顾问集团华北电力设计院（以下简称“中电华北院”）尼日利亚AJAOKUTA—LOKOJA—GWAGWALADA330千伏双回输电线路总承包工程测量项目（以下简称“ALG项目”）荣获中国测绘工程界最高奖项——“中国测绘学会优秀测绘工程白金奖”。 相似文献
27.
郝拴元 《资源导刊(河南)》2011,(9):36-36
近日，河南省地矿局在尼日利亚宾盖发现大型铌钽砂矿，探明铌钽金属资源量逾4万吨，锡金属资源量2万吨。 相似文献
28.
李致家 《中国海洋湖沼学报》2008,26(3):313-322
In this paper, the long-term dependence phenomenon （the Hurst Effect） which characterizes hydrological and other geophysical times series is studied. The long-term memory is analysed for both daily and monthly streamflow series of the Benue River at Makurdi, Nigeria by using heuristic methods and testing specifically the null hypothesis of short-term memory in the monthly flow series. Results obtained by applying heuristic procedures indicated that there may be the presence of long-term memory component in mean daily flow series but there is no discernible reason to suspect the presence in both average monthly and maximum monthly flow series （extreme event）. Hypothesis testing was conducted by using original and modified versions of rescaled range statistic. When the modified rescaled range, which accounts for short-term memory in the series, is used, the null hypothesis is accepted for both the average monthly and maximum monthly flow series, indicating little or no probable presence of long-term memory in the series. An identical conclusion is also arrived at when second null hypothesis for independence of the monthly flow series is tested. Therefore, apart from the mean daily flow series, there is little evidence of long-term dependence in the Benue River streamflow series at Makurdi. However, considering the limited length of data used, the results are inconclusive. 相似文献
29.
A gabbro-diorite plutonic complex from the Southeast Obudu Plateau, representing limited volumes of magma, was studied for its trace and rare-earth element characteristics, in an attempt to document its genetic and geodynamic history. Geochemical studies indicate that the gabbro samples are characterized by variable concentrations and low averages of such index elements as Cr (40×10-6–200×10-6; av. 80×10-6), Ni (40×10-6–170×10-6; 53.33×10-6) and Zr (110×10-6–240×10-6; 116.67×10-6); variable and high average... 相似文献
30.
The trace elements characteristics of the migmatitic gneisses (biotite-garnetand hornblende-biotite), granulite facies rocks (charnockitic gneisses) and meta-peridotite in the area of Southwest Obudu Plateau indicate that the area exhibits a high degree of geochemical variability. Compatible trace elements (Ni and Cr) are comparatively high in the granulite facies rocks and meta-peridotite. Ni ranges from 28×10-6 to 266×10-6 whilst Cr ranges from 62×10-6 to 481×10-6 for the granulite facies rocks (charnocki... 相似文献