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宁芜盆地火山-次火山岩的锆石U-Pb年龄、Hf同位素组成及其地质意义 总被引：40，自引：23，他引：17
宁芜火山盆地是长江中下游重要的火山盆地之一,在盆地内自下而上依次发育龙王山组、大王山组、姑山组和娘娘山组火山岩和若干个同源次火山岩或小侵入岩体。本文对宁芜盆地火山-次火山岩进行了详细的锆石U-Pb年龄和Hf同位素地球化学研究。研究结果表明,大王山组粗安岩锆石U-Pb年龄为130.3±0.9Ma,姑山组两个粗安岩锆石U-Pb年龄分别为128.2±1.3Ma和128.5±1.8Ma,另外三个侵入岩年龄分别为127.1±1.2Ma、128.3±0.6Ma和128.2±1.0Ma,均为早白垩纪。综合前人成果,认为长江中下游地区火山盆地内火山活动的时限在135～124Ma之间,不存在侏罗纪岩浆活动。宁芜盆地火山岩和侵入岩的锆石176Hf/177Hf值在0.282502～0.282673范围内,εHf(t)变化为-6.9～-0.7,显示岩浆源自于岩石圈富集地幔部分熔融并在上升过程中受地壳物质的混染,为岩石圈伸展环境的产物。 相似文献
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Karen G. Villholth Jegan Ganeshamoorthy Christian M. Rundblad Theis S. Knudsen 《Hydrogeology Journal》2013,21(7):1481-1495
A simple but comprehensive framework for analysing the potential for and constraints to groundwater development for irrigated agriculture in sub-Saharan Africa is proposed. The framework, based on food value chain principles, is applied to the sub-Saharan context and a specific catchment in Tanzania, the Usangu plains, where groundwater has been proposed as a strategic resource for augmenting food production and smallholder livelihoods and to alleviate seasonal water scarcity. The novel contribution of the work is the presentation of a tool that can be applied to support an interdisciplinary approach to systematically identify most significant barriers and most critical water management and development interventions for sustainable development of groundwater irrigation. The result of the case study shows that farmer economics, capacity, and pump and well drilling market constraints limit groundwater irrigation in the Usangu plains rather than hydrogeological conditions. 相似文献
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Christian Theis Werner Zeilinger Susanne Hüttemeister 《Astronomische Nachrichten》2005,326(7):485-521
Posters: Because of the large number of contributions, some oral presentations had to be transferred into Posters. The reader is referred to the final programme for the actual allocation of Posters. A01 Chemical Enrichment of the Intracluster Medium A02 Structural analysis of high‐velocity clouds – Evidence for an interaction between the Milky Way and the Magellanic System A03 Multi‐Phase Chemo‐Dynamical SPH code for galaxy evolution A04 The proper motion of M33 A05 Wavelet analysis of Intra–group Light in Hickson Compact Groups A06 Evidence for an evolutionary connection between early and late type dwarf galaxies A07 Dwarf Galaxies in the NGC 5846 Group A08 X‐ray spectroscopy of serendipitous clusters of galaxies in XMM‐Newton observations A09 Evolution of smale scale systems of galaxies: X‐ray detected E+S galaxy pairs A10 Modelling Star Formation in Interacting Galaxies A11 NGC 1427A – the beginning of the end: a lonely dwarf irregular entering the dense core of the Fornax cluster A12 Dwarf galaxies in galaxy groups: Photo‐evaporation, orbits and gas stripping A13 High resolution stellar kinematics for the central component of the Polar Ring Galaxy NGC 4650A A14 The Influence of Environment on the Morphological Evolution of Disk‐Dominated Galaxies A15 Interactions and star formation in galaxies A16 Dust Condensations and Molecular Clouds in Interacting Spirals A17 Star formation rates and kinematics of modelled interacting galaxies A18 Evolution of Galaxies and the Tully–Fisher Relation A19 Evolution and Collision of Galaxies on the GRID A20 Multiwavelength observations of two S+E merger candidates: the Medusa and NGC 4441 A21 Interacting Galaxies in Small Galaxy Groups A22 Virial and total masses of galaxy triplets in the Local Supercluster A23 Simulations of Interaction Processes of Galaxies with the Intra‐Cluster Medium A24 Chemical evolution of the thick and thin disks of our Galaxy A25 Dust properties of UV‐bright galaxies at z ∼ 2 A26 Simulation of the Gravitational Collapse and Fragmentation of Rotating Molecular Clouds A27 NGC 5719/13: interacting spirals forming a counter‐rotating stellar disc A28 Starbursts in very metal‐poor dwarfs due to interactions and mergers: link to the processes in the high‐redshift young galaxies A29 Testing galaxy evolution in the field: morphology and properties of the diffuse X‐ray emission in shell galaxies A30 Effects of galactic winds on dIrrs with particular emphasis on NGC 1569 and the refill of superbubble cavities A31 Galaxy formation through merging at z ≈ 2 A32 3D simulations of the ISM‐ICM interaction of disk galaxies in clusters A33 Gas replenishment in ram pressure stripped disk galaxies A34 New Results on the Kinematics of the Outer Cluster System of NGC 1399 A35 Chemical gradient evolution in massive galaxy disk due to its minor merger with dwarf galaxy A36 The complex kinematics of galaxies in Hickson 62 A37 Dust in the outer regions of interacting galaxies A38 Dynamical interaction of M31 and M32 A39 A comparative study of galaxy properties in low‐ and high density environment A40 Compact Groups in Dense Environment: The Case of IC1370 A41 The Star Formation History of CG J1720‐67.8 A42 Galaxy populations in the infall regions of intermediate redshift clusters A43 The study of gravitational fragmentation in two‐clumps collisions A44 Star Formation Activity in Galaxy Clusters Near and Far A45 An Exploration of the Merging History of the Local Starburst Galaxy, NGC 3310 A46 The high‐velocity clouds of M31: tracers of galactic evolution A47 The Properties of Fossil Groups 相似文献
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西藏南部晚始新世打拉埃达克质花岗岩及其构造动力学意义 总被引：9，自引：7，他引：2
打拉二云母花岗岩岩体位于雅拉香波穹隆的东南,侵入到中生代以前的变质岩系(眼球状花岗质片麻岩和石榴黑云母片麻岩)和特提斯沉积岩(页岩和砂岩)中,主要由石英、斜长石、钾长石、黑云母和白云母组成,形成于～44.3Ma。打拉二云母花岗岩地球化学特征表明:打拉花岗岩具有高Al_2O_3(16.0%～17.0%)、Na_2O/K_2O(1.2)以及A/CNK比值(1.05),表明打拉花岗岩为富钠过铝质花岗岩;轻稀土(LREE)富集,重稀土(HREE)相对亏损,HREE中的Ho到Lu元素有变平的特征((Ho/Lu)_N=1.11～1.46);具有微弱或无Eu异常,Eu/Eu~*=0.87～0.95;较高的初始Sr同位素比值(~(87)Sr/~(86)Sr(i)=0.71754～0.71785)和较低的初始Nd比值(ε_(Nd)(i)=-9.15～-12.4)。打拉花岗岩具有高Sr含量(为355×10~(-6)～416×10~(-6))和Sr/Y的比值(59.1～71.5)、高La/Yb比值、低Y及HREE亏损的特征,与埃达克质花岗岩类似。上述特征表明打拉花岗岩是在较高压力条件下,以角闪岩为主的深部岩石部分熔融的结果。 相似文献
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KJ. Maniharsingh 《Astrophysics and Space Science》1993,205(2):259-276
Radiating anisotropic two-fluid model universes coupled with a scalar field when a slow rotation is introduced in them are studied here, where the anisotropic pressure is generated by the presence of two non-interacting perfect fluids which are in relative motion with respect to each other. Special discussion is made of the physically interesting class of models in which one fluid is a comoving radiative perfect fluid which is taken to model the cosmic microwave background and the second a non-comoving perfect fluid which will model the observed material content of the Universe. Here we take up four analytic solutions. The effects of rotation on these models are studied and the reactions of the scalar and the radiation fields with respect to the rotational motion are discussed. Analysis on the rotational perturbations are also made, in the course of which the amount of anisotropy induced in the pressure distribution by a small deviation from the Friedmann metric is also investigated. It is shown that such anisotropies could grow faster than the expansion of the Universe. The rotating models we obtain here are found to be theoretically satisfactory and they may be taken as physically acceptable models. 相似文献
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The aim of this paper is to show the contribution of geography to the study of pastoral mobility. While pastoralists of Ferlo,
Senegal, have become semi-sedentary, little is known about the mobility of their livestock. In this paper, pastoral mobility
is analysed using GPS measurements of cattle movements made by a pastoralist from 1997 to 2000. Based on data from 3 years,
a quantification of the extent of movements and mappings of the patterns are made. The results show that cattle walk about
5000 km on an annual basis, and while a great deal of the mobility can be characterised as daily circular movements between
the camp and watering points, occasional transhumance is still used to make the most of variable resources. 相似文献
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Chemo-dynamical models have been introduced in the late eighties andare a generally accepted tool for understanding galaxy evolution. Theyhave been successfully applied to one-dimensional problems, e.g. theevolution of non-rotating galaxies, and two-dimensional problems,e.g. the evolution of disk galaxies. Recently, also three-dimensionalchemo-dynamical models have become available. In these models thedynamics of different components, i.e. dark matter, stars and amulti-phase interstellar medium, are treated in a self-consistent wayand several processes allow for an exchange of matter, energy andmomentum between the components or different gas phases. Some resultsof chemo-dynamical models and their comparison with observations ofchemical abundances or star formation histories will be reviewed. 相似文献
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Conventional planet formation models via coagulation of planetesimals require timescales in the range of several 10 or even 100 Myr in the outer regions of a protoplanetary disk. But according to observational data, the lifetime of a protoplanetary disk is limited to about 6 Myr. Therefore the existence of Uranus and Neptune poses a problem. Planet formation via gravitational instability may be a solution for this discrepancy. We present a parameter study of the possibility of gravitationally triggered disk instability. Using a restricted N‐body model which allows for a survey of an extended parameter space, we show that a passing dwarf star with a mass between 0.1 and 1 M⊙ can probably induce gravitational instabilities in the pre‐planetary solar disk for prograde passages with minimum separations below 80‐170 AU. Inclined and retrograde encounters lead to similar results but require slightly closer passages. Such encounter distances are quite likely in young moderately massive star clusters. The induced gravitational instabilities may lead to enhanced planetesimal formation in the outer regions of the protoplanetary disk, and could therefore be relevant for the formation of Uranus and Neptune. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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