Effect of the chemical composition of the crust on the metamorphic evolution of orogenic wedges   总被引：4，自引：0，他引：4  

B. Goffé  R. Bousquet  P. Henry  X. Le Pichon 《Journal of Metamorphic Geology》2003,21(2):123-141

Petrological data provide a good record of the thermal structure of deeply eroded orogens, and, in principle, might be used to relate the metamorphic structure of an orogen to its deformational history. In this paper, we present two‐dimensional thermal modelling of various subduction models taking into account varying wedge geometry as well as variation of density and topography with metamorphic reactions. The models clearly show that rock type accreted in the wedge has important effects on the thermal regime of orogenic wedges. The thermal regime is dominated by radiogenic heat production. Material having high radioactive heat production, like the granodioritic upper crust, produces high temperature metamorphism (amphibolitic conditions). Material with low radioactive heat production results in low temperature metamorphism of greenschist or blueschist types depending on the thickness of the wedge. Application of this model to seemingly unrelated areas of the Central Alps (Lepontine Dome, Grisons) and Eastern Alps (Tauern Window) explains the coexistence and succession of distinct Barrovian and blueschist facies metamorphic conditions as the result of a single, continuous tectonic process in which the main difference is the composition of the incoming material in the orogenic wedge. Accretion of the European upper continental crust in the Lepontine and Tauern Domes produces Barrovian type metamorphism while accretion of oceanic sediments results in blueschist facies metamorphism in the Valaisan domain.  相似文献   

Contens of Volume 59     

Henry F. Diaz  Jon K. Eischeid  Chris Duncan  Raymond S. Bradley 《Climatic change》2003,59(3):417-418

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Are assemblages of black bream (Acanthopagrus butcheri) in different estuaries genetically distinct?     

J.A. Chaplin  G.A. Baudains  H.S. Gill  R. Mcculloch  I.C. Potter 《International Journal of Salt Lake Research》1997,6(4):303-321

Samples of the estuarine-spawning teleostAcanthopagrus butcheri were collected from nine estuaries and a coastal lake, located in the Pilbara and South-western drainage divisions of Western Australia and distributed along a coastline covering a distance of nearly 2,000 km. The patterns of allozyme variation in these samples were used to explore the extent to which there was variation in the genetic compositions of black bream assemblages in geographically-isolated estuarine systems, and whether or not any such variation could be related to the geographical location or type of estuary. Although only three of 36 scorable loci (Gpi-1, Ldh andMdh-2) exhibited variation that could be used for analysis, there was considerable variation in allele frequencies at these loci among the different samples (mean F_ST=0.166). Much of the detected variation was attributable to differences between the samples collected from the two drainage divisions, which are located in very different climatic regions. Furthermore, the genetic compositions of samples from neighbouring estuaries were typically more similar to each other than to those of samples collected from more distantly-located systems. However, the assemblages in one west coast and two south coast estuaries, that are closed to the ocean for extensive periods of time during the year, all showed very similar genetic compositions. Nevertheless, it is crucial to recognise that, pairwise comparisons of samples collected from the different estuaries, both within and between the two drainage divisions, almost invariably showed statistically significant differences in allele frequencies at one or more loci. Thus, our results indicate that the local populations of black bream in individual estuaries are genetically distinct, which is probably a consequence of both a limited movement by individuals between estuaries and the effects of differences in regional and local environmental conditions.  相似文献   

Putting Japanese investment in Europe in its place   总被引：1，自引：0，他引：1  

Peter Dicken  Adam Tickell  Henry Yeung 《Area》1997,29(3):200-212

Summary Research on Japanese economic activity in Europe concentrates almost exclusively on investment in manufacturing. However, this paper demonstrates that this emphasis both underestimates the longevity of Japanese direct investment in Europe and also grossly underdefines the importance of services. Not only does Japanese direct investment have a much longer history in Europe than is usually recognized but also—and perhaps more significantly—the bulk of that investment is not in manufacturing production per se but in a variety of circulation services. Using establishment-level data, this paper shows that the spatial manifestation of these circulation services is very different from that of manufacturing production.  相似文献   

Induced stresses and fault potential in eastern Canada due to a realistic load: a preliminary analysis   总被引：1，自引：0，他引：1  

Patrick Wu  Henry S. Hasegawa 《Geophysical Journal International》1996,127(1):215-229

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The replacement of anthophyllite by jimthompsonite: a model for hydration reactions in biopyriboles     

Bernard Henry Grobéty 《Contributions to Mineralogy and Petrology》1997,127(3):237-247

Anthophyllite crystals found in ultramafic lenses of the Lepontine Alps (Switzerland) contain coherent, submicroscopic intergrowths of ordered and disordered biopyribole polysomes. The chain width distributions of disordered polysomes were analyzed using high resolution transmission electron microscopy (HRTEM). Chains wider than triple were interpreted as intermediate products in the transformation of anthophyllite to the triple chain silicate jimthompsonite. The concentration of individual chain types is strongly correlated with the reaction progress. Based on observed zipper terminations and the transformation rules given by Veblen and Buseck (1980) a scheme of possible reaction paths leading from anthophyllite to jimthomp sonite is proposed. The reaction scheme and a simple kinetic model for elementary reactions allow modeling of the observed chain width distributions. The model suggests that the complex reaction paths involving steps with increasing and decreasing chain width are more important in the formation of jimthompsonite than the direct transformation from anthophyllite. The wide chains (>triple) occurring as intermediate products of the multi-step paths are structurally closer to talc than jimthompsonite. The back-transformation of these wide chains to triple chains is, therefore, a strong argument that jimthompsonite is a stable phase and not only a metastable intermediate product in the transformation of anthophyllite to talc. Received: 8 July 1996 / Accepted: 13 December 1996  相似文献   

Submarine Ground Water Discharge and Salt Penetration Across the Sea Floor   总被引：1，自引：0，他引：1  

Henry Bokuniewicz  Meagen Pollock  John Blum  Robert Wilson 《Ground water》2004,42(7):983-989

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‘Committing to Place’ at the Local Scale: the potential of youth education programs for promoting community participation in regional natural resource management     

Ruth Lane  Damian Lucas  Frank Vanclay  Sophie Henry  Ian Coates 《The Australian geographer》2005,36(3):351-367

Emerging approaches to environmental governance require a greater level of community participation than did previous approaches in which these responsibilities largely rested with government agencies. There is consequently a need for increased engagement with NRM among a broad community sector. This paper examines initiatives by two prominent government agencies, the Murray–Darling Basin Commission (MDBC) and the National Museum of Australia (NMA), to engage school children from regional communities using education programs that focus on place and environmental health. We focus on the MDBC's International Riverhealth Conference held in Mildura in 2003 and the associated Murray–Darling Basin TalkBack Classroom sponsored by the NMA and the Parliamentary Education Office (PEO). We explore how key themes of local scale, place-based identities, youth voice and critical engagement are developed in these programs and consider how they relate to the environmental agency of children. We then reflect on the potential for the kinds of environmental agency promoted through these programs to help build the capacity of local communities to progress larger goals of environmental restoration and sustainability in the Murray–Darling Basin. The evaluation research reported here forms part of the Committing to Place research project, an Australian Research Council Linkage grant involving the University of Tasmania, the National Museum of Australia and the Murray–Darling Basin Commission.  相似文献   

Variations of U and Sr isotope ratios in Alsace and Luxembourg rain waters: origin and hydrogeochemical implications     

Franois Chabaux  Jean Riotte  Anne-Dsire Schmitt  Jean Carignan  Pierre Herckes  Marie-Claire Pierret  Henry Wortham 《Comptes Rendus Geoscience》2005,337(16):4612

Major and trace element concentrations, as well as Sr and U isotope ratios, were measured in rainwater samples collected in three different locations in Alsace (East of France) and Luxembourg: a mid-altitude mountain site (Aubure Environment HydroGeochemical Observatory), an urban site (Strasbourg) and a peri-urban site located in an area of well developed industrial activity (Esch-sur-Alzette in Luxembourg). Results highlight the quite high spatial and temporal variability of the chemical and isotopic characteristics of rainwater at the regional scale. They also suggest a quite systematic contribution of a local component in the chemical composition of rainwater. In urban and peri-urban sites, the local component is certainly linked to human activities, as it is well illustrated in this study with the Esch-sur-Alzette samples. On the other hand, for the Aubure site, i.e. a small forested watershed of mid-altitude mountain, data presented in this study demonstrate the influence of the vegetation on the chemical composition of rainwater for alkali and calc-alkali elements, as well as for the Sr isotope ratios. Such a result questions the reliability of the method classically used to estimate the rainwater contribution on the river chemical budget. In addition, data of the present study confirm the very low content of uranium in rainwater and demonstrate, especially through the U isotope analysis of Aubure rainwater, the negligible effect of rainwater on U budget of river waters. This work thus outlines the property of U to be a geochemical tracer specific of weathering fluxes carried by rivers. To cite this article: F. Chabaux et al., C. R. Geoscience 337 (2005).  相似文献   

A catalogue of caldera unrest at Taupo Volcanic Centre,New Zealand,using the Volcanic Unrest Index (VUI)     

Sally H. Potter  Bradley J. Scott  Gill E Jolly  David M. Johnston  Vince E. Neall 《Bulletin of Volcanology》2015,77(9):1-28

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