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21.
22.
We studied the existence of dynamical stochastic relations in the evolution of the am index. A first analysis of the autocorrelation functions showed evidence of several seasonalities. We first used linear (ARMA) models, and it was found that these do not account for the whole internal dynamics of the data series. We then used various non-linear models to provide a better fit to reality. The forecast performances of the non-linear models are not significantly different from those of the linear model. We give a tentative explanation for the failure of the non-linear predictions. Finally, ARCH models were used in order to take into account the fact that the confidence interval for the predicted value depends on past observations. 相似文献
23.
In the Gran Paradiso massif (western Alps), the boundary between the Erfaulet orthogneiss and the overlying metasediments (Money Complex) is interpreted as a Late Palaeozoic intrusive contact. Major arguments in favour of this hypothesis are: (i) the obliquity of the sedimentary layering with respect to the contact; (ii) the presence of aplitic dykes within the Money Complex; (iii) the lack of a mylonitic zone; and (iv) rare relics of an early generation of garnet in the Money metasediments, interpreted as evidence of the contact metamorphism of the Erfaulet granite. To cite this article: B. Le Bayon, M. Ballèvre, C. R. Geoscience 336 (2004). 相似文献
24.
25.
Basil Tikoff Matthew R. Davis Christian Teyssier Michel de St. Blanquat Guillaume Habert Sven Morgan 《Tectonophysics》2005,400(1-4):209-226
The Cascade Lake shear zone occurs on the eastern margin of the Tuolumne Intrusive Suite, Sierra Nevada Batholith, California. Foliation in the zone is NNW trending and subvertical, and lineation is moderately south plunging. Deformation is syn-tectonic with emplacement of the Cathedral Peak granodiorite. A deformation gradient exists toward the NE margin of this pluton, with higher strains and lower temperatures of deformation found near the contact. We compare fabric data collected very densely in this shear zone using several techniques: field fabrics, 3D orientation of K-feldspar megacrysts, and AMS (anisotropy of magnetic susceptibility) analysis. In general, the results from the three different methods are in agreement. Deformation in this shear zone is part of a larger pattern of deformation within the Cathedral Peak granodiorite, as recorded by AMS analysis, and dextral shearing associated within the last stage of plutonism within the Sierra Nevada magmatic arc. 相似文献
26.
Quantum-thermodynamic treatment of intrinsic anharmonicity; Wallace’s theorem revisited 总被引:1,自引:0,他引:1
Wallace (in Thermodynamics of crystals, 1972) developed a theorem, rooted in rigid lattice dynamics, which incorporates intrinsic anharmonic effects in solids. The practical
application of this theorem in mineral physics is computationally involved and this is the main reason for the theorem not
getting the attention it deserves. Because intrinsic anharmonicity is an important issue at the extreme conditions in planetary
mantles, we derived a method which removes the computational obstacles in applying this theorem. We extended the theorem to
incorporate details of the phonon spectrum and tested our algorithm on forsterite (Mg2SiO4). Using a least squares inversion technique applied to all available experimental data, we show that it results in an accurate
representation of thermodynamic properties and sound wave velocities of Mg2SiO4 in its complete pressure–temperature stability range. We also show that the accuracy of our results is not significantly
affected by the use of a different equation of state. 相似文献
27.
This paper briefly reviews the sociological literature on the “New” Chinatown phenomenon stressing its structural location
vis-à-vis the “Old” Chinatown and the homeland. It defines the New Chinatown as a panethnopolis, that is a global neighborhood
with a majority population of Chinese immigrants and of other ethnic groups of mostly Asian descent. It analyzes more particularly
the formation, development, and integration of San Francisco’s Richmond District’s New Chinatown into both the city where
it is located and the network of transglobal sites to which it belongs. It provides an interpretation of the New Chinatown
as a cultural enclave within the context of globalization theory. 相似文献
28.
Michel Magny Matthieu Honegger et Laurent Chalumeau 《Eclogae Geologicae Helvetiae》2005,98(2):249-259
Resume. Les fouilles archéologiques réalisées de 1998 à 2002 sur le site néolithique de Marin-Les Piécettes sur la rive nord-ouest
du lac de Neuchatel ont offert l’opportunité d’observer deux séquences sédimentaires intéressantes pour la reconstitution
des variations holocènes du niveau du lac, en particulier au cours de la période correspondant au changement de cours de l’Aar
en direction du nord-est, vers 5650–5500 cal BP. La géométrie des corps sédimentaires et les changements lithologiques permettent
de reconna?tre plusieurs phases majeures de bas niveaux relatifs du plan d’eau vers 6870, 5660, 5060–3990, 3580, 2280, 1640
et 1170 cal BP. Le site néolithique de Marin-Les Piécettes s’est développé vers 5454–5433 cal BP à la faveur d’un court épisode
de bas niveau du lac qui a interrompu une importante phase de haut niveau au début du Subboréal. Les événements paléohydrologiques
identifiés à Marin-Les Piécettes apparaissent cohérents avec ceux reconstitués sur le site de Montilier au bord du lac de
Morat, ainsi qu’avec les variations paléohydrologiques reconstituées à partir des lacs du Jura, du Plateau suisse et des Préalpes
du Nord fran?aises. Ceci suggère qu’ils témoignent d’un signal climatique. La séquence sédimentaire de Marin-Les Piécettes
met enfin en évidence la formation d’un cordon littoral sur la rive nord-ouest du lac juste après 5660 cal BP.
Manuscrit re?u le 22 septembre 2004 Révision acceptée le 11 mars 2005 相似文献
29.
30.
Prosper Rakotovao Andrianjakavah Stefano Salvi Didier Béziat Michel Rakotondrazafy Gaston Giuliani 《Mineralium Deposita》2009,44(7):817-835
The Ianapera emerald deposit is located in the Neoproterozoic Vohibory Block of southern Madagascar. The local geology consists
of intercalated migmatitic gneissic units and calcareous metasedimentary rocks, containing boudinaged metamorphosed mafic/ultramafic
lenses, all intruded by pegmatite veins. These units occur near the hinge of the tightly folded Ianapera antiform, within
a few kilometers of the Ampanihy shear zone. Emerald mineralization is hosted by metasomatic phlogopite veins, and bodies
developed within the mafic/ultramafic rocks. Based on field and textural relationships, we distinguish proximal and distal
styles of mineralization. Proximal mineralization occurs at the contact of pegmatite veins with mafic/ultramafic units; in
the distal style, pegmatites are not observed. Three types of emeralds could be distinguished, mainly on the basis of color
and mineral zoning. Some of these emeralds have the most Al-depleted and Cr-rich composition ever recorded. Another characteristic
feature to the Ianapera deposit and, to our knowledge, yet unreported, is the association of some emeralds with scapolite
in metasomatised mafic rocks. Mineral inclusions are common in most emeralds and include phlogopite, carbonates, barite, K-feldspar,
quartz, pyrite, zircon, monazite, bastnaesite, phenakite, plus Fe and Cr oxides. However, feldspar and rare earth element-bearing
minerals occur predominantly in proximal emeralds, which also have a more incompatible trace-element signature than distal
emeralds. We propose a model related to syn- to post-tectonic magmatic-hydrothermal activity. Pegmatitic bodies intruded units
of the Ianapera antiform probably during tectonic relaxation. Exsolution of fluids rich in halogens and incompatible elements
from the cooling pegmatites caused hydrothermal metasomatism of Cr-bearing mafic/ultramafic rocks in direct contact with the
pegmatites. Local fracturing favored fluid infiltration, permitting the formation of distal mineralization. Emerald composition
was controlled by the chemistry of the host rock. The presence of carbonate mineral inclusions in the emeralds and the high
F-activity indicated by elevated F-contents in newly formed minerals suggest transport of Be as a fluoride-carbonate complex.
It seems likely that beryl formation was triggered by precipitation of F-rich phlogopite, which removed the complexing ligand
from the fluid. 相似文献