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221.
Partial melting during tectonic exhumation of a granulite terrane: an example from the Larsemann Hills, East Antarctica 总被引:23,自引:0,他引:23
C. J. CARSON R. POWELL C. J. L. WILSON & P. H. G. M. DIRKS 《Journal of Metamorphic Geology》1997,15(1):105-126
Anatectic migmatites in medium- to low-pressure granulite facies metasediments exposed in the Larsemann Hills, East Antarctica, contain leucosomes with abundant quartz and plagioclase and minor interstitial K-feldspar, and assemblages of garnet–cordierite–spinel–ilmenite–sillimanite. Qualitative modelling in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2, in conjunction with various P–T calculations indicate that the high-grade retrograde evolution of the terrane was dominated by decompression from peak conditions of c. 7 kbar at c. 800 °C to 4–5 kbar at c. 750 °C. Extensive partial melting during decompression involved the replacement of biotite by the assemblage cordierite–garnet–spinel within the leucosomes. These leucosomes represent the site of partial melt generation, the cordierite–garnet–spinel–ilmenite assemblage representing the solid products and excess reactants from the melting reaction. The extraction and accumulation of this decompression-generated melt led to the formation of syntectonic pegmatites and extensive granitic plutons. Leucosome development and terrane decompression proceeded during crustal transpression, synchronous with upper crustal extension, during a progressive Early Palaeozoic collisional event. Subsequent retrograde evolution was characterized by cooling, as indicated by the growth of biotite replacing spinel and garnet, thin mantles of cordierite replacing spinel and quartz within metapelites, and garnet replacing orthopyroxene and hornblende within metabasites. P–T calculations on late mylonites indicate lower grade conditions of formation of c. 3.5 kbar at c. 650 °C, consistent with the development of late cooling textures. 相似文献
222.
人地系统动力学研究中的几个问题 总被引:1,自引:0,他引:1
人地系统动力学研究是当前地理学研究的最主要领域,应从人的生存和发展需要出发,围绕人类活动的环境效应和人地协调发展主线选择研究对象,界定研究内容,采用物质能量守恒分析和统计分析相结合的方法,加强对人地相互作用机制的研究。 相似文献
223.
博斯腾湖的水盐平衡与矿化度 总被引:11,自引:5,他引:11
博斯腾湖曾是中国内陆区最大的淡水湖,因人类活动影响约在1968年演变为微咸水湖。本文依据湖泊水平衡太矿化度基本原理,结合博斯滕湖实际,分析计算了该湖各个时期的水盐平衡与矿化度;经推地整理,提出了预测矿化度的计算式,经检验与实测值基本吻合。 相似文献
224.
Zhuang XinguoZhuang XinguoGeothermal Regime of Meso-Cenozoic Basins Their Tectonic Background in East ChinaFaculty of Earth Resources China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1997,(1)
GeothermalRegimeofMeso-CenozoicBasinsandTheirTectonicBackgroundinEastChina*ZhuangXinguoFacultyofEarthResources,ChinaUniversit... 相似文献
225.
Li ZhongInstitute of Geology Chinese Academy of Sciences Beijing Sun YongchuanDepartment of Petroleum Geology China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1997,(1)
ReservoirDiagenesisSequenceandFrameworkinIntracontinentRiftBasin,EastChina*LiZhongInstituteofGeology,ChineseAcademyofSciences... 相似文献
226.
Lithospheric Stretching,Subsidence and Thermal History Modeling: Application to Yinggehai,Qiongdongnan and Songliao Basins in East China 总被引:3,自引:0,他引:3
Lin ChangsongDepartment of Energy Resources China University of Geosciences Beijing Li SitianFaculty of Earth Resources China University of Geosciences Wuhan Zhang QiminWest Nanhai Oil Company Zhanjiang Zhang 《中国地质大学学报(英文版)》1997,(1)
LithosphericStretching,SubsidenceandThermalHistoryModeling:ApplicationtoYinggehai,QiongdongnanandSongliaoBasinsinEastChina*Li... 相似文献
227.
DYNAMIC VARIATIONS OF WATER QUALITY IN TAIHU LAKE AND MULTIVARIATE ANALYSIS OF ITS INFLUENTIAL FACTORS 总被引:1,自引:0,他引:1
Cai Qiming Gao Xiyun Chen Yuwei Ma Shengwei Nanjing Institute of Geography Limnology CAS Nanjing People''s Republic of ChinaMartin Dokulil Institute of Limnology Austria 《地理学报(英文版)》1997,(3)
LakeTaihuisalargeshallowlakeinChina,whichpalysanimportantroleinwater-quantityregulation,watersupply,cultivationetc.Withrapiddevelopmentofagricultureandindustryinthearea,alargenumberofpollutantshavebeendischargedintothelake,leadingtoanincreaseinnutrients… 相似文献
228.
Yoshiko Kawabata Hiroyuki Nakahara Yukio Katayama Norio Ishida 《International Journal of Salt Lake Research》1997,6(1):5-16
The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes in Central Asia. They range from oligosaline to metasaline.
The salinity of the Aral Sea has increased by more than 30 g L−1 since widespread irrigation began in its catchment area. Few studies of the phytoplankton have been conducted on these lakes
since extensive irrigation started. The investigation reported here compares the flora of phytoplankton in these saline lakes.
In the Small Aral Sea, phytoplankton density gradually decreased with increasing electrical conductivity (EC) (∼ salinity),
but there was no such relation in Lake Balkhash and Lake Kamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae were
frequently observed in most areas of high EC value, and Cyanophyceae were most conspicuous in the area of medium and lower
EC values. In Lake Balkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were also noticeable. Most Cyanophyceae
in Aral Sea formed filaments with heterocysts. The distinct characteristic of the phytoplankton of the Lake Balkhash was that
all dominant species form colonies covered with a gelatinous film. Siliceousplankton diversity gradually decreased with increasing
EC values in the Aral Sea and Lake Balkhash. 相似文献
229.
Ming Zhao Charles A. Langston rew A. Nyblade Thomas J. Owens 《Geophysical Journal International》1997,129(2):412-420
An Mw 5.9 earthquake occurred in the Lake Rukwa rift, Tanzania, on 1994 August 18, and was well recorded by 20 broad-band seismic stations at distances of 160 to 800 km and 21 broad-band stations at teleseismic distances. The regional and teleseismic waveforms have been used to investigate the source characteristics of the main shock, and also to locate aftershocks that occurred within three weeks of the main shock. Teleseismic body-wave modelling yields the following source parameters for the main shock: source depth of 25 ± 2 km, a normal fault orientation, with a horizontal tension axis striking NE-SW and an almost vertical pressure axis (Nodal Plane I: strike 126°–142°, dip 63°–66°, and rake 280°–290°; Nodal Plane II: strike 273°–289°, dip 28°–31°, and rake 235°–245°), a scalar moment of 4.1 times 1017 N m, and a 2 s impulsive source time function. Four of the largest aftershocks also nucleated at depths of 25 km, as deduced from regional sPmp–Pmp times. The nodal planes are broadly consistent with the orientation of both the Lupa and Ufipa faults, which bound the Rukwa rift to the northeast and southwest, respectively. The rupture radius of the main shock, assuming a circular fault, is estimated to be 4 km with a corresponding stress drop of 6.5 MPa. Published estimates of crustal thickness beneath the Rukwa rift indicate that the foci of the main shock and aftershocks lie at least 10 km above the Moho. The presence of lower-crustal seismicity beneath the Rukwa rift suggests that the pre-rift thermal structure of the rifted crust has not been strongly modified by the rifting, at least to depths of 25 km. 相似文献
230.
Bettina Reimann 《Applied geography (Sevenoaks, England)》1997,17(4):301-313
The constitutional decision to return to their original owners all real-estate property in East Germany that had either been expropriated or placed under state administration (the restitution principle) has had significant consequences for urban development and urban renewal. Experiences from East Berlin's innercity residential areas illustrate the effects on the state of repair of housing, the character of residential neighbourhoods, the tenants living in the areas affected, and the future structure of real-estate ownership. The case studies reveal a picture of a contradictory development of residential neighbourhoods, including shifting power relations and new polarizations, especially between tenants and landlords. 相似文献