Regional GPS data confirm high strain accumulation prior to the 2000 June 4 M_w= 7.8 earthquake at southeast Sumatra     

G. W. Michel  M. Becker  Ch. Reigber  R. Tibi  Y. Q. Yu  S. Y. Zhu 《Geophysical Journal International》2001,146(3):571-582

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Channelling contribution to tipper vectors: a magnetic equivalent to electrical distortion   总被引：2，自引：0，他引：2  

Ping Zhang  Laust B. Pedersen  Marianne Mareschal  Michel Chouteau 《Geophysical Journal International》1993,113(3):693-700

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The 2 Ga peraluminous magmatism of the Jacobina — Contendas Mirante Belt (Bahia) Brazil): Major and trace-element geochemistry and metallogenic potential     

Michel Cuney  Pierre Sabat  Philippe Vidal  Moacyr M. Marinho  Herbet Conceiao 《Journal of Volcanology and Geothermal Research》1990,44(1-2)

The Jacobina — Contendas Mirante belt represents a Transamazonian (2 Ga), N-S, 500-km long, elongated orogenic domain in the central part of the São Francisco craton, Bahia state. Numerous syntectonic to post-tectonic peraluminous leucogranites were emplaced along the major structures of the belt. Their mineralogical and geochemical and some of their metallogenetic characteristics are very similar to their Hercynian and Himalayan equivalents. However, their average peraluminous index varies from one granitic pluton to another and biotite is, on average, slightly more magnesian in the Transamazonian leucogranites. Higher oxygen fugacity is indicated by the general occurrence of magnetite, the stability of allanite and sometimes epidote in most of the plutons and by biotite chemistry. The peraluminous magmatism of the Jacobina-Contendas Mirante belt results from crustal partial melting during a continental collision event at 2 Ga.Trace-element geochemistry implies variable source composition and/or melting conditions for the different granitic plutons and some different facies within the same plutonic unit. The scarcity of ilmenite, the general occurrence of magnetite, and the relatively low peraluminous index of some of these granites suggest that graphite-beating sediments are not a significantly source material. From their mineralogical and geochemical characteristics, acid meta-igneous rocks such as the Sete Voltas TTG suite of presumed Archaean age, seem to represent a suitable source for these granites.Sn, W, Li, F and Be enrichment of most Transamazonian leucogranites is much weaker than in the mineralized Variscan equivalents. The Caetano-Aliança and Riacho das Pedras granites represent the most specialized granitic bodies. Beryl (emerald), molybdenite and scheelite mineralizations are related to some of these granites which intrude ultrabasic formations: the Campo Formoso and the Carnaiba granites. In many of these granites, uranium content is comparable to values measured in mineralized Hercynian leucogranites. The occurrence of hexavalent uranium minerals, mineralization and episyenitic alteration are favourable criteria for finding Variscan-type uranium ore deposits.  相似文献   

Meta-igneous origin of Hercynian peraluminous granites in N.W. French Massif Central: implications for crustal history reconstructions     

Laurent Turpin  Michel Cuney  Marc Friedrich  Jean-Luc Bouchez  Monique Aubertin 《Contributions to Mineralogy and Petrology》1990,104(2):163-172

Seventy samples of Hercynian peraluminous granites (Guéret, Millevaches and Saint Sylvestre massifs) and metamorphic units of the Limousin area were analysed for Rb–Sr and Sm–Nd. The source rocks of the peraluminous granites can be found in the metamorphic rocks of Limousin, among them meta-igneous rocks were largely predominent over meta-sedimentary rocks in the source of the three granites. Millevaches and Guéret granites were generated by the partial melting of rocks comprising meta-volcanics and meta-sediments, whereas the Saint Sylvestre granite was produced exclusively by the melting of late Precambrian granites. This leads to confusing T _DM ^Nd values, the confusion being amplified by the segregation of monazite during the petrogenetic evolution of the peraluminous granites, which leads to dramatic fractionation in Sm/Nd ratios. The data of the present study tend to demonstrate that peraluminous granites do not give a good representation of isotopic mean crustal estimates. Late Precambrian time seems, however, to have been a period of extensive crustal generation in Western Europe.  相似文献   

Love-Rayleigh wave incompatibility and possible deep upper mantle anisotropy in the Iberian peninsula   总被引：1，自引：0，他引：1  

Valérie Maupin  Michel Cara 《Pure and Applied Geophysics》1992,138(3):429-444

Love and Rayleigh wave phase velocities are analyzed with the goal of retrieving information about the anisotropic structure of the Iberian lithosphere. The cross-correlation method is used to measure the interstation phase velocities between diverse stations of the ILIHA network at periods between 20 and 120 s. Despite the 2-D structure of the network, the Love wave data are too few to enable an analysis of phase velocity azimuthal variations. Azimuthal averages of Love and Rayleigh wave phase velocities are calculated and inverted both in terms of isotropic and anisotropic structures. Realistic isotropic models explain the Rayleigh wave and short-period Love wave phase velocities. Therefore no significant anisotropy needs to be introduced in the crust and down to 100 km depth in the upper mantle to explain our data. A discrepancy is observed only at long periods, where the data are less reliable. Love wave data at periods between 80 and 120 s remain 0.15 km/s faster than predicted by isotropic models explaining the long-period Rayleigh wave data. Possibilities of biases in the measurements due to interferences with higher modes are examined but seem unlikely. A transversely isotropic model with 8% of S-wave velocity anisotropy in the upper mantle at depths larger than 100 km can explain the whole set of data. In terms of a classical model of mantle anisotropy, this corresponds to 100% of the crystals perfectly oriented in the horizontal plane in a pyrolitic mantle. This is a rather extreme model, which predicts at time delay between 0 and 2 seconds for split SKS.  相似文献   

Ignimbrites of basaltic andesite and andesite compositions from Tanna,New Hebrides Arc     

Claude Robin  Jean-Philippe Eissen  Michel Monzier 《Bulletin of Volcanology》1994,56(1):10-22

Tanna island is part of a large volcanic complex mainly subsided below sea-level. On-land, two series of hydroclastic deposits and ignimbrites overlie the subaerial remains of a basal, mainly effusive volcano. The ‘Older’ Tanna Ignimbrite series (OTI), Late Pliocene or Pleistocene in age, consists of ash flows and ash- and scoria-flow deposits associated with fallout tephra layers, overlain by indurated pumice-flow deposits. Phreatomagmatic features are a constant characteristic of these tuffs. The ‘younger’ Late Pleistocene pyroclastics, the Siwi sequence, show basal phreatomagmatic deposits overlain by two successive flow units, each comprising a densely welded layer and a nonwelded ash-flow deposit. Whole-rock analyses of 17 juvenile clasts from the two sequences (vitric blocks from the phreatomagmatic deposits, welded blocks, scoriaceous bombs and pumices from the ignimbrites) show basaltic andesite and andesite compositions (SiO₂=53–60%). In addition, 296 microprobe analyses of glasses in these clasts show a wide compositional range from 51 to 69% SiO₂. Dominant compositions at ∼54, 56, 58.5 and 61–62% SiO₂ characterize the glass from the OTI. Glass compositions in the lower – phreatomagmatic – deposits from the Siwi sequence also show multimodal distribution, with peaks at SiO₂=55, 57.5, 61–62 and 64% whereas the upper ignimbrite has a predominant composition at 61–62% SiO₂. In both cases, mineralogical data and crystal fractionation models suggest that these compositions represent the magmatic signature of a voluminous layered chamber, the compositional gradient of which is the result of fractional crystallization. During two major eruptive stages, probably related to two caldera collapses, the OTI and Siwi ignimbrites represent large outpourings from these magmatic reservoirs. The successive eruptive dynamics, from phreatomagmatic to Plinian, emphasize the role of water in initiating the eruptions, without which the mafic and intermediate magmas probably would not have erupted. Received: February 19, 1993/Accepted October 10, 1993  相似文献   

Current status,distribution, life cycle and ecology ofRhithrogena germanica Eaton, 1885 in Switzerland: Preliminary results (Ephemeroptera,Heptageniidae)     

Verena Lubini  Michel Sartori 《Aquatic Sciences - Research Across Boundaries》1994,56(4):388-397

Rh. germanica is a European species that, due to human impacts, has progressively disappeared from its original territories and is now considered rare. In SwitzerlandRh. germanica has disappeared from the Aare, Broye and Kleine Emme rivers and is actually found in a limited reach of the River Rhine and some of its tributaries (Limmat, Sihl, Thur and Töss rivers).Rh. germanica is a univoltine species, hatching probably in summer. The emergence occurs from February to the beginning of April. It takes place on the water surface. Laboratory observations have shown that the subimaginal stage lasts four days.Rh. germanica occurs on different substrate types, ranging from stones and cobbles to pebbles and gravel. The larvae are more abundant in zones of erosion with coarse and porous sediments than in depositional zones with fine sediments and silts. They are most abundant in riffles with water velocities from 20 to 150 cm/sec. The species tolerates moderately organic-polluted waters.The particular strategy concerning growth and emergence ofRh. germanica is also discussed.  相似文献   

Book reviews     

Michel M. Verstraete  Eric J. Barron  William M. Stigliani 《Climatic change》1988,12(1):95-101

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Book reviews     

Michel M. Verstraete 《Climatic change》1988,13(2):231-232

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Testing whether two Fisher distributions have the same centre     

Geoffrey S. Watson  Michel G. Debiche 《Geophysical Journal International》1992,109(1):225-232

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