Element Mobility During Incipient Granulite Formation at Kabbaldurga, Southern India   总被引：7，自引：2，他引：7  

ST?HLE  H.J.; RAITH  M.; HOERNES  S.; DELFS  A. 《Journal of Petrology》1987,28(5):803-834

At Kabbaldurga, infiltration of carbonic fluids along a systemof ductile shears and foliation planes has led to partial transformationof Archaean grey biotite–hornblende gneiss to coarse-grainedmassive charnockite at about 2.5 b.y. ago. The dehydration ofthe gneiss assemblage was induced by a marked metasomatic changeof the reacting system from granodioritic to granitic, and obviouslytook place under conditions of an open system at 700–750?C and 5–7 kb. Extensive replacement of plagioclase (An_16–30)by K-feldspar through Na, Ca–K exchange reactions withthe ascending carbonic fluids led to strong enrichment in K,Rb, Ba, and SiO₂, and to a depletion in Ca. Progressive dissolutionof hornblende, biotite, magnetite, and the accessory mineralsapatite and zircon resulted in a marked depletion in Fe, Mg,Ti, Zn, V, P, and Zr. Most important is the recognition of REEmobility: with advancing charnockitization, the moderately fractionatedREE distribution patterns of the grey gneisses (La_N270; La_N/Yb_N= 5–20; Eu_N27; Eu/Eu^* = 0.6–0.3) give way to stronglyfractionated REE patterns with a positive Eu-anomaly (La_N200;La_N/Yb_N = 20–80; Eu_N22; Eu/Eu^* = 0.6–1.8). The systematicdepletion especially in the HREE is due to the progressive dissolutionof zircon, apatite (and monazite), which strongly concentratethe REE. Stable isotope data (¹⁸O of 6.9–8.0 per mille for gneissesand charnockites; ¹³C of –8.5 and –6.5 per millefor late carbonate) indicate a magmatogenic source for the carbonicfluids. In contrast to the currently favoured derivation ofcarbonic fluids by decarbonation of the upper mantle or degassingof underplated basaltic intrusions, it is discussed here thatabundant fluid inclusions in lower crustal charnockites providedan extensive reservoir of ‘fossil’ carbonic fluids.Shear deformation has tapped this reservoir and generated thechannel-ways for fluid ascent. Charnockitization of the Kabbaldurgatypethus appears to be a metasomatic process which is tectonicallycontrolled and restricted to the crustal level of the amphiboliteto granulite transition.  相似文献   

Soil-structure interaction with Rayleigh waves     

Alberto Gmez-Mass  John Lysmer  Jian-Chu Chen  H. Bolton Seed 《地震工程与结构动力学》1983,11(4):567-583

Presented is a plane-strain method for soil-structure interaction analysis consisting of the superposition of the free field motions and the interaction motions in a generalized seismic environment. The free field is modelled as a horizontally layered viscoelastic medium and the seismic environment may consist of a combination of S, P and Rayleigh waves. The soil-structure system is modelled with viscoelastic finite elements, transmitting boundaries, viscous boundaries and a three-dimensional simulation. Comparative analyses of the same structure are conducted for an input of R waves and for vertically propagating S and P waves in a rock site and sand site. In the rock site the R waves produce higher peak horizontal spectral acceleration up to 25 per cent, and a significant rocking effect at points away from the centre of gravity of the structure. However, the S and P waves show higher peak vertical spectral acceleration by up to 15 per cent at the centre of the structure. Very similar horizontal response, but higher vertical response only at the centre of the structure for S and P waves, is obtained for the sand site.  相似文献   

Comment on “Silicic melts produced by reaction between peridotite and infiltrating basaltic melts: ion probe data on glasses and minerals in veined xenoliths from La Palma,Canary Islands” by Wulff-Pedersen et al.     

Andreas?KlügelEmail author 《Contributions to Mineralogy and Petrology》2001,141(4):505-510

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Tectono-thermal modeling of the Yinggehai Basin,South China Sea   总被引：1，自引：0，他引：1  

Lijuan?HeEmail author  Liangping?Xiong  Jiyang?Wang  Jihai?Yang  Weiliang?Dong 《中国科学D辑(英文版)》2001,44(1):7-13

Based on the observed data, the average value of surface heat flow in the Yinggehai Basin is calculated and it turns out to be 84.1 mW/m². The thermal evolution of the basin since the Cenozoic era has been attempted by tectono-thermal modeling. Three-phase extension made the basin become hotter and hotter, reaching its climax in paleo-temperature history since 5.2 Ma. And nowadays, the basin is in the heat flow decreasing period. During the Cenozoic era, the basement heat flow remained at 50–70 mW/m² all the time. This is related to the degree of each extension phase, stretching rate mode and also the limited basin scale. Modeling results also show that, the surface heat flow is controlled mainly by the basement heat flow, and less than 20% comes from radiogenic heat production in the sediments of the basin  相似文献   

Direct and Indirect pCO2 Measurements in a Wide Range of pCO2 and Salinity Values (The Scheldt Estuary)     

Michel Frankignoulle  Alberto Vieira Borges 《Aquatic Geochemistry》2001,7(4):267-273

Recent improvements in both Infra-red spectroscopy and equilibrator techniqueshave allowed to determine, for the first time, pCO₂using simultaneously and continuously both the direct and indirect methods in an estuary where pCO₂ values range from 500 to 8500 atm and salinity from 0 to 30. Our results show that both methods are in excellent agreement in the wholeestuary (r² = 0.999, n = 1075, p < 0.0001). Thus, the NBS (US National Bureau of Standards) scale, although inadequate for seawater samples, is appropriate for estuarine waters and can be applied with confidence to calculate pCO₂.  相似文献   

Iodine concentrations of soils near Trabzon, Turkey: a region of endemic goiter     

E. ?ift?i  E. ?evketbeyo?lu  S. Tokel 《Environmental Geology》2007,53(2):457-465

Iodine contents of soils developed over the major rock formations of the northern zone of the Eastern Pontide Tectonic Belt (Northeastern Turkey) have been investigated with respect to soil-parent rock relationship, effect of topography, elevation, and climate to construe its effect on the health of the local population. Samples were collected from the A and B horizons of the soils developed over the major stratigraphic units constituting the eastern Pontides, including the Lower Basic Complex of Jurassic-Lower Cretaceous age, the Berdiga limestone (Jurassic-lower Cretaceous), the Dagbasi granitoid (Upper Cretaceous), volcano-sedimentary sequence of Upper Cretaceous age, ore-bearing and barren dacites of Upper Cretaceous age, and Neogene alkaline basalts. Chemical analyses of soil samples indicate significantly lower iodine abundances for all the soils studied (5–28 ppm) in comparison to the average abundance of iodine in analogous soils of other parts of the world (22–93 ppm). The concentration of iodine in soils developed over the same geologic formation decrease with increasing elevation. In certain cases, this decrease may reach up to 70%. Goiter is highly common throughout this region in Turkey. The results of this study suggest that the iodine deficiency of region’s soils may be a principal underlying cause for this area of Turkey being an endemic goiter region.  相似文献   

An energy-duration procedure for rapid determination of earthquake magnitude and tsunamigenic potential   总被引：1，自引：0，他引：1  

Anthony Lomax  Alberto Michelini  Alessio Piatanesi 《Geophysical Journal International》2007,170(3):1195-1209

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松潘-平武地震前地震视应变场的时空演变          下载免费PDF全文

张彬  杨选辉  易志刚 《地震工程学报》2007,29(3):235-239

利用松潘-平武周边地区的地震资料研究了1970-1975年该地区地震视应变场的分布和时空变化特征。结果表明,地震视应变的时空变化与松潘-平武强震具有很好的对应关系,1970年在附近就出现异常区,并且地震视应变总体上逐年增加,地震就发生在地震视应变异常区。  相似文献   

2006年甘肃文县5.0级地震灾害损失评估   总被引：1，自引：1，他引：1       下载免费PDF全文

马占虎  周志宇  高晓明  何文贵  刘洪春 《地震工程学报》2007,29(3):256-259,263

2006年6月21日在甘肃省文县发生MS5.0地震,造成了建筑物破坏及人员伤亡。在震后开展的地震现场考察与震害评估工作中,将灾区分为2个评估子区,完成了29个点的震害抽样调查工作,根据地震灾害损失评估系统EDLES2.5的要求建立了有关数据库,做出了经济损失评估,并针对灾害特点给出了灾区恢复重建的建议。  相似文献   

高分辨率浅层人工地震勘探探测隐伏断裂实例   总被引：1，自引：4，他引：1       下载免费PDF全文

连玉平  张锦福  林松建  陈伟 《地震工程学报》2007,29(3):260-263

利用高分辨率浅层地震勘探反射波法探测了福建某火电厂场址内的隐伏断裂。结果表明断裂显示清楚,为一走向NE40~55°,上断点埋深为11 m和31 m,断距2~4 m的正断层,为工程避让提供较可靠的依据。  相似文献