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71.
A 70 Ma record of suprasolidus conditions in the large,hot, long‐duration Grenville Orogen 下载免费PDF全文
François Turlin Clara Deruy Aurélien Eglinger Olivier Vanderhaeghe Anne‐Sylvie André‐Mayer Marc Poujol Abdelali Moukhsil Fabien Solgadi 《地学学报》2018,30(3):233-243
Petrochronology of magmatic monazite and apatite from a single paragneiss leucosome derived by in situ partial melting documents the thermal evolution of the Allochthonous Belt of the central Grenville Province. Monazite records suprasolidus metamorphism from ca. 1080 to 1020 Ma under high temperature up to 850°C. Apatite from the same leucosome yields an age of 960 Ma, consistent with cooling of this crustal segment down to subsolidus conditions of ca. 450°C. A pegmatitic granite dyke, with lobate contacts, previously dated at ca. 1005 Ma (Turlin et al., 2017 ) is interpreted to intrude the paragneisses at a temperature of ca. 650°C close to the wet‐solidus. These data document slow cooling at a rate of 2–6°C/Ma for the middle crust of this part of the Grenville hinterland marked by protracted suprasolidus conditions for at least 70 Ma. It supports the definition of the Grenville Orogen as a large, hot, long‐duration orogen. 相似文献
72.
André Giret Sylvie Tourpin Sabine Marc Olivier Verdier Jean-Yves Cottin 《Comptes Rendus Geoscience》2002,334(7):481-488
Despite its small area (5.6 km2), the Penguins Island brings magmatic information concerning mantle geochemical heterogeneities in southwestern Indian Ocean. The volcanism that built the island was firstly associated with marine deposits, and secondly with aerial, giving then abundant volcanic breccias and lava flows. The rocks are weakly differentiated and result of magmatic fractionation from picritic to tephritic types. KAr ages are near 1.1 Ma. The magmatic source may be related to a HIMU reservoir or to EMI ± EMII ones, depending on the geochemical evidences that are taken into account. However, comparisons with the Marion Island, on the same oceanic plateau and far to the west, as well as with Kerguelen Islands, far to the east, suggest a very heterogeneous mantle source. To cite this article: A. Giret et al., C. R. Geoscience 334 (2002) 481–488. 相似文献
73.
Sylvie Derenne Jean-Noël Rouzaud François Robert 《Geochimica et cosmochimica acta》2005,69(15):3911-3917
Polyaromatic hydrocarbons (PAHs) are often considered as abundant and widespread organic structures in the universe and such structures are known to build the macromolecular network of the organic matter in carbonaceous chondrites. Assuming that interstellar PAHs are properly identified from infrared bands, these meteoritic aromatic moieties can be compared with their interstellar counterpart. The main structural parameters of the aromatic units of the insoluble organic matter of the Orgueil and Murchison chondrites are directly determined through high resolution transmission electron microscopy along with image analysis. These aromatic moieties appear weakly organized and of a smaller size than those present in the interstellar medium (containing ∼30 and ∼150 C atoms). Provided chondritic and interstellar polyaromatic hydrocarbons are derived from a similar organosynthesis, the smaller units were selectively preserved in meteorites, likely thanks to their fast accumulation on grains, which would protect them from solar UV photodissociation at the surface of the protosolar disk. 相似文献
74.
M. Renard N. Chaumerliac S. Cautenet N. Audiffren E. C. Nickerson 《Journal of Atmospheric Chemistry》1995,20(3):237-258
The sensitivity of the horizontal and vertical transport of an inert tracer to seasonal variability of the complex West Africa circulations is explored by means of a 2D mesoscale meteorological model including explicit microphysics and describing the cloud dynamics of these circulations. The seasonal variations of the location and spatial extent of the cloudy masses associated with the Inter Tropical Convergence Zone (ITCZ) are reproduced in a meridional cross section over West Africa. The redistribution of the inert tracer is shown to be due to the northward migration of the ITCZ from January to July and also to the enhancement of the convective activity of the ITCZ in July. The redistribution of carbon monoxide during the dry and wet seasons is discussed, highlighting the importance of the biomass burning during the dry season as a source of trace gas enrichment in the upper levels of the tropical troposphere over West Africa. 相似文献
75.
Ozone tendencies due to chemistry and transport are calculated by a mesoscale model using a fine horizontal resolution (3 km × 3 km),
over South-Eastern France. Over that region where the anthropogenic emissions are very strong, ozone pollution is highlighted
during two intensive observations periods of the ESCOMPTE campaign, when the sea breeze penetrates far into the Durance and
Rhone valleys and the up-slope breezes are developed. From a fine analysis of time series of ozone concentration at different
ground stations along these valleys and from numerical results, it is possible to discriminate the tendency due to chemistry
from the tendency due to dynamical processes. We can distinguish both processes, either local chemical production/loss or
dynamical increase/decrease (transport, deposition) on maps of ozone budget according to the meteorological conditions. In
particular, we show that the variations due to transport can be have the same order of magnitude than those due to chemistry,
reaching 20 ppbv h−1, whereas those due to chemistry are around 30 ppbv h−1. 相似文献
76.
Detecting decadal changes in ENSO using neural networks 总被引:1,自引:2,他引:1
Julie A. Leloup Zouhair Lachkar Jean-Philippe Boulanger Sylvie Thiria 《Climate Dynamics》2007,28(2-3):147-162
77.
Richard Giot Sylvie Granet Maxime Faivre Nadia Massoussi Julie Huang 《Geomechanics and Geoengineering》2018,13(4):246-263
A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study. 相似文献
78.
Denise Bussien Grosjean Nicolas Meisser Sylvie May-Leresche Alexey Ulianov Pierre Vonlanthen 《Swiss Journal of Geoscience》2018,111(1-2):35-49
The Morcles microgranite is located in the N–E termination of the Aiguilles Rouges massif (External Crystalline Massifs, Switzerland). It outcrops as dykes, a few meters to 150 m in thickness, intruding the Aiguilles Rouges polymetamorphic basement, and presents variation of texture from granophyric to rhyolitic. We present here for the first time, in situ U–Pb zircon dating of the Morcles microgranite/rhyolite based on laser-ablation—inductively coupled plasma—mass spectrometry (LA-ICP-MS) data. Results indicate late Variscan emplacement ages at ~303 and ~309–312 Ma, a major Caledonian inherited component age at ~445–460 Ma, and secondary inherited ages ranging from Pan-African (550–1000 Ma) to Paleoproterozoic (2.3 Ga). Geochronological and geochemical data indicate that the Morcles microgranite/rhyolite shares a common origin with the higher (or “H”) facies of the neighbouring Vallorcine granitic intrusion. This close affinity is further corroborated by the geographical alignment of both intrusive bodies on either side of the Rhone Valley. The fine-grained texture of the microgranite groundmass and the rhyolite indicates a very rapid cooling rate and emplacement close to the surface, suggesting that the Morcles microgranite/rhyolite may constitute the shallow-level counterpart of the Vallorcine granite. The mineralogical assemblages observed in the Morcles microgranite/rhyolite support the idea of high-temperature melting conditions provided by underplating of mantle-derived magmas during the Carboniferous extension of the Variscan cordillera. 相似文献
79.
Didier Gourier Olivier Delpoux Herve Vezin Sylvie Derenne 《Geochimica et cosmochimica acta》2008,72(7):1914-1923
The insoluble organic matter of the carbonaceous meteorites contains radicals having a polyaromatic structure and a heterogeneous distribution. By using Hyperfine Sublevel Correlation spectroscopy (HYSCORE) in pulsed Electron Paramagnetic Resonance (pulsed-EPR), whereby nuclear frequencies of magnetic nuclei and their hyperfine interaction with electron spin of radicals are detected with high resolution, the radicals are shown to be considerably enriched in deuterium in the Orgueil meteorite, with a D/H ratio of 1.5 ± 0.5 × 10−2. These radicals hold 3.6 ± 1.2 × 10−3 H relative to total organic H.Analysis of hydrogen and deuterium hyperfine interactions indicates that the deuterium atoms are localized in the benzylic position, on aliphatic carbons bonded to aromatic radical moieties. This type of C-H bond exhibits one of the smallest bond energy, reinforcing the recent finding that the lower the C-H bond energy the higher the deuterium-enrichment (Remusat L., Palhol F., Robert F., Derenne S. and France-Lanord C. (2006) Enrichment of deuterium in insoluble organic matter from primitive meteorites: a solar system origin? Earth Planet. Sci. Lett.243, 15-25). Such a behavior is difficult to reconcile with the usual interpretation according to which high D/H ratios represent survivals of interstellar grains. More likely, the deuterium-enrichment process took place after the formation of organic grains whose initial isotopic compositions was close to the protosolar D/H ratio. These grains were possibly loaded at the surface of the protosolar disk where they exposed to the intense solar UV irradiation, triggering an isotopic exchange with deuterium-rich highly reactive ions. 相似文献
80.
Sylvie Philippe Céline Leterme Sandric Lesourd Lucie Courcot Udo Haack Jacinthe Caillaud 《Applied Geochemistry》2008
The Seine estuary possesses a heavily industrialised catchment area that contrasts significantly with that possessed by the smaller Authie estuary. For both of these northern French estuaries, Pb isotopic compositions and concentrations have been determined on specimens of Hediste diversicolor (ragworms) and on HCl leachates performed on related mudflat sediment. Three sampling campaigns were completed in 2003. As expected, the reactive Pb obtained by 1 M HCl leaching, shows higher concentrations and a more anthropogenic signature in samples from the Seine estuary than in samples from the Authie. However, neither of the two sites is free from the influence of anthropogenic Pb. Possible contaminant sources are discussed through comparisons with previously published data. For the more highly contaminated Seine estuary, most of the ragworm Pb signatures are similar to those of the sediments. In contrast, ragworms from the Authie site exhibit a higher proportion of anthropogenic Pb than the corresponding sediments. Various hypotheses are discussed to explain this significant discrepancy: (1) analytical artifacts, (2) migration of ragworm populations, (3) diet and feeding behaviour, and as the most likely explanation (4) an unsuitable leaching method for the extraction of bioavailable Pb. 相似文献