Herschel SPIRE FTS relative spectral response calibration     

Trevor Fulton  Rosalind Hopwood  Jean-Paul Baluteau  Dominique Benielli  Peter Imhof  Tanya Lim  Nanyao Lu  Nicola Marchili  David Naylor  Edward Polehampton  Bruce Swinyard  Ivan Valtchanov 《Experimental Astronomy》2014,37(2):381-395

Herschel/SPIRE Fourier transform spectrometer (FTS) observations contain emission from both the Herschel Telescope and the SPIRE Instrument itself, both of which are typically orders of magnitude greater than the emission from the astronomical source, and must be removed in order to recover the source spectrum. The effects of the Herschel Telescope and the SPIRE Instrument are removed during data reduction using relative spectral response calibration curves and emission models. We present the evolution of the methods used to derive the relative spectral response calibration curves for the SPIRE FTS. The relationship between the calibration curves and the ultimate sensitivity of calibrated SPIRE FTS data is discussed and the results from the derivation methods are compared. These comparisons show that the latest derivation methods result in calibration curves that impart a factor of between 2 and 100 less noise to the overall error budget, which results in calibrated spectra for individual observations whose noise is reduced by a factor of 2–3, with a gain in the overall spectral sensitivity of 23 % and 21 % for the two detector bands, respectively.  相似文献   

Oxygen 1.27-μm emission from the atmosphere of Venus     

Jean-Paul Parisot  Guy Moreels 《Icarus》1980,42(1):46-53

The emission of O₂ in the ${}^1\text{Δg}$ band at 1.27 μm originating from the upper atmosphere of Venus is computed. Seven different production mechanisms are compared. The adopted value for the quenching rate coefficient is 3 × 10^?20 cm³ sec^?. The results are compared with the measurements by Connes and it is shown that the values of the ozone profile calculated by N. D. Sze and M. B. McElroy (1975, Planet. Space Sci.23, 763–786) are too low to explain the emission at 1.27 μm on the basis of the ozone photolysis. In this case, the ozone quantity would be underestimated by a factor of at least 10. The scarcity of kinetic data relative to the other processes, which involve ClO for example, does not allow a reliable identification of the main process responsible for the emission.  相似文献   

Swiss and Alpine geologists between two tectonic revolutions. Part 1: from the discovery of nappes to the hypothesis of continental drift     

Jean-Paul Schaer 《Swiss Journal of Geoscience》2010,103(3):503-522

At the advent of the twentieth century, geologists believed that folded continental mountain chains like the Alps were due to horizontal compression, resulting from contractions of the Earth’s crust as it cooled. In 1918, Albert Heim defended this point of view and illustrated it with a geological section across Switzerland. In 1915, however, and in short notes as early as 1912, Alfred Wegener in Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans) proposed that mountains were the result of collisions between light continents drifting and floating on denser formations of the Earth’s interior, also present at the bottom of the oceans. Before this (1906), Otto Ampferer had already proposed the association of folds with active movements of material inside the Earth. Wegener used numerous morphological, geological, and gravimetric data to justify his theory. He was innovative in his successful use of paleogeographic and paleoclimatologic reconstitutions. Although very popular, his theory only received reserved approval from the active scientific community. Alpine geologists found it too audacious and too far removed from the field data. In the first critical analysis written in French (1922), Elie Gagnebin welcomed it as a working hypothesis, but was very reserved regarding the arguments of a geophysicist who, in his opinion, was not sufficiently versed in structural geology. In contrast, Emile Argand integrated Wegener’s theory into his conception of the evolution of the Alps already in 1916. At that time, he judged the Alpine orogeny to have been the result of permanent compression and proposed that its whole history had been dominated by what he called embryonic tectonics, a compressional concept which he illustrated so admirably that it had an incomparable and lasting success. However, he himself abandoned it in his major work, La Tectonique de l’Asie (The Tectonics of Asia), in favour of an evolution that first originated in an extension regime, finally leading to the splitting of the continental crust, with local emergence of basic rocks, constituting the bottom of new oceanic floors. It is at the slope of these continental margins, and at their foot, that geosynclines are formed by the large accumulation of sediments transported by submarine slumping. During the following compressive stage, slices of basic ocean floor are transported upwards between overlapping continental masses, forming extensive ophiolitic zones. Although admired for his enormous accomplishment, La Tectonique de l’Asie remained ignored for its most innovative propositions, which clearly foreshadow plate tectonics. After this work, Argand practically abandoned geology. His last publication (1934), Guide géologique de la Suisse: la zone pennique (Geological Guide to Switzerland: the Pennine Zone), revived his argument of the early evolution of the geosyncline in a context of extension, followed by thrusts involving the ocean floor. Unfortunately, the concept had no greater success than at its first appearance.  相似文献   

Geochemistry and Sr, Nd, Pb isotopic composition of the Central Atlantic Magmatic Province (CAMP) in Guyana and Guinea   总被引：2，自引：0，他引：2  

Katja Deckart  Herv Bertrand  Jean-Paul Ligeois 《Lithos》2005,82(3-4):289-314

The Central Atlantic Magmatic Province (CAMP) is one of the largest igneous provinces on Earth, extending more than 5000 km north to south, on both sides of the Atlantic Ocean. Its emplacement occurred about 200 Ma ago, at the Triassic–Jurassic boundary, and is linked to the initial breakup of Pangaea. Two areas of the province are studied here: French Guyana/Surinam (South America) and Guinea (West Africa), in order to document the petrogenesis and geodynamical significance of high-Ti and low-Ti basaltic magmas from the CAMP.

In Guyana, doleritic and gabbroic dykes are located on the edge of the Guiana Shield, and represent limited volumes of magma. They display low SiO₂ (47–50%), high TiO₂ (2.5–3.5%) and high FeO tholeiitic trends and show variably enriched trace element patterns ((La/Yb)_n=1.5–5.1). Their isotopic signature and ratios of very incompatible elements (εNd_i=+5.8 to +4.2, (⁸⁷Sr/⁸⁶Sr)_i=0.703–0.705, (²⁰⁷Pb/²⁰⁴Pb)_i=15.46–15.64) match a depleted PREMA (prevalent mantle)-like source. Their genesis can be modeled by ca. 15% partial melting of a lherzolite source, and a subsequent limited fractional crystallization (5–10%) or a slight upper crustal assimilation–fractional crystallization (AFC, r=0.1, Proterozoic contaminant). In Guinea, in contrast, huge volumes of CAMP magmas were intruded along the Rockelides suture and the West African craton, forming the Fouta Djalon sills and the Kakoulima laccolith. The laccolith is more than 1000 m thick. These features consist of gabbros, dolerites, diorites and mafic (gabbro) and ultramafic (dunite, wherlite) cumulates. Guinean tholeiites show high SiO₂ (51–58%), low TiO₂ (0.7–1.2%) and FeO trends, with high LILE/HFSE ratios and slight negative Nb–Ta anomalies. Isotopic signatures (εNd_i=+0.4 to −5.3, (⁸⁷Sr/⁸⁶Sr)_i=0.705–0.710, (²⁰⁷Pb/²⁰⁴Pb)_i=15.57–15.66) indicate a more enriched source than for Guyana as well as a higher rate of magma–upper crust interaction through an AFC process (r=0.3, Birimian crust contaminant) and, probably, an additional upper crustal contamination for the most differentiated sample.

This geochemical study supports the prevalence in Guinea, as for other low-Ti CAMP tholeiites, of a lithospheric mantle source, previously enriched during ancient subduction events, and preferentially reactivated in late Triassic times by edge-driven convection between cratonic and mobile belt domains. A larger contribution from a depleted asthenospheric source is required to generate high-Ti tholeiites in Guyana, which may reflect the development of CAMP rifting towards the initiation of the Central Atlantic oceanic crust.  相似文献   

Système hydrogéologique d'un massif minier ultrabasique de Nouvelle-Calédonie     

Jean-Lambert Join  Bernard Robineau  Jean-Paul Ambrosi  Claire Costis  Fabrice Colin 《Comptes Rendus Geoscience》2005,337(16):1500-1508

Ultramafic rocks outcrop over more than one third of New Caledonia's main island. Under tropical conditions, thick lateritic mantles with nickel concentrations developed on these rocks by geochemical weathering. Groundwater in ultramafic mined massifs represents a valuable resource, but also a severe constrain for mining engineering. Previous works describe several water tables in the various layers of the weathering mantle. From a hydrologic study of the Tiebaghi massif, the hydraulic continuity across the weathering layers down to the bedrock is proposed. To cite this article: J.-L. Join et al., C. R. Geoscience 337 (2005).  相似文献   

Mise en évidence d'une discontinuité émersive majeure au sein de la plate-forme récifale plio-pléistocène de l'avant-arc des Petites Antilles     

Jean-Len Léticée  Auran Randrianasolo  Jean-Jacques Cornée  Philippe Münch  Jean-Frédéric Lebrun  Jean-Paul Saint-Martin  Michel Villeneuve 《Comptes Rendus Geoscience》2005,337(6):617-624

A major emersion surface (S1) reveals at least a 60-m relative sea-level fall within the ‘Calcaires supérieurs’ of Grande-Terre (Lesser Antilles fore-arc), an Upper Pliocene–Lower Pleistocene reefal unit. We thus divide the ‘Calcaires supérieurs’ into 2 units. S1, together with the transgresssive calcarenitic and the Acropora-rich reefal units on top of it, corresponding to the record of a complete eustatic cycle by the carbonate platform of this active margin. A comparison with the carbonate platform of the Bahama Bank stable margin, allows us to relate S1 to the major emersive event of 1.66 Ma and to infer that its origin is glacio-eustatic. To cite this article: J.-L. Léticée et al., C. R. Geoscience 337 (2005).  相似文献   

A spatial analysis of structural controls on Karst groundwater geochemistry at a regional scale   总被引：7，自引：0，他引：7  

Danile Valdes  Jean-Paul Dupont  Benoît Laignel  Sylvie Ogier  Thierry Leboulanger  Barbara J. Mahler 《Journal of Hydrology》2007,340(3-4):244-255

The coupled spatial investigation of the geometrical and geochemical properties of a chalk karstic aquifer provides information on the degree to which geologic structure controls aquifer functioning and groundwater quality. Major ion concentrations in the chalk aquifer of the Haute-Normandie region (France) were measured at a high spatial resolution (more than 100 sampling sites over a 6000 km² area) and mapped. The first observation is a continuity of the geochemical properties, in spite of the karstic properties of the aquifer principal components analysis of geochemical maps revealed two types of spatial distributions: ions with an autochthonous origin (Ca²⁺, HCO₃), and ions with a principally allochthonous origin (Cl⁻, Na⁺, , ). Mg²⁺ was categorised as both autochthonous (chalk dissolution) and allochthonous (brought in by infiltration of Tertiary deposits). To better understand the spatial distribution of the geochemistry, the aquifer geochemistry was compared to the physical properties of the aquifer, in particular aquifer thickness (representing aquifer geometry) and piezometric level (representing aquifer flow). Use of spatial correlation between the geochemical and the geometrical properties provided insight regarding the directional structure of the data and give evidence of directional relations between geochemical and geometrical properties. The degree of mineralisation (principally composed of Ca²⁺ and ions) increased along the direction of flow, corresponding to an increase in chalk dissolution rate along the flowpath. The steepest mineralisation gradients were related to an increase in the Mg/Ca ratio, evidence of longer residence times and corresponding to zones where aquifer flow capacity is limited because of a decrease of the thickness of the flow section (anticlines or faults). These results highlight the dominant role played by the geometry and the structural context in controlling aquifer geochemistry.  相似文献   

New UPb zircon ages from Tonga (Cameroon): coexisting Eburnean–Transamazonian (2.1 Ga) and Pan-African (0.6 Ga) imprints     

Evine Laure Tanko Njiosseu  Jean-Paul Nzenti  Théophile Njanko  Badibanga Kapajika  Anne Nédélec 《Comptes Rendus Geoscience》2005,337(6):551-562

The central domain of the Pan-African Belt in Cameroon is characterized by abundant porphyritic granitoids, which were emplaced synkinematically and variably orthogneissified in relation with ENE-striking steeply dipping transcurrent shear zones. These plutonic rocks have intermediate to felsic compositions and constitute a high-K calk-alkaline series. Conventional UPb zircon dating yields an age of 618 Ma for this syntectonic Pan-African magmatism in the Tonga area. The country rocks are made of metabasites (garnet amphibolites) and tonalitic to trondhjemitic gneisses, which suffered two distinct orogenic cycles: the first one is the Palaeoproterozoic Eburnean–Transamazonian cycle at 2.1 Ga and the second one is the Pan-African orogenesis. These new ages confirm the existence of an extensive Palaeoproterozoic crust in Cameroon and question the areal extent of the Congo–São Francisco craton towards the north. To cite this article: E.L. Tanko Njiosseu et al., C. R. Geoscience 337 (2005).  相似文献   

Photochemistry of flourine in the mesosphere of Venus     

Jean-Paul Parisot  Guy Moreels 《Icarus》1984,59(1):69-73

In the laboratory, reactions with flourine species proceed rapidly with high rates but under mesospheric conditions the effeciency of these compounds is low due to the rapid formation of HF and to the lack of reactivity of this species. Even if diffusion processes are included, the result of calculations leads to fluorie concentrations typically less than 20 cm^?3. The low photodissociation coeffecient of HF leads to the expectation of a scale height of HF greater than or equal to the mean scale height. If the troposphere appears to be a sink for hydrofluoric acid, the maximum value of fluorine is obtained with a downward flux of 1.3 × 10⁸ HF atoms cm^?2 sec^?1 at the level of the clouds.  相似文献   

Donnees experimentales sur la diffusion des elements majeurs entre verres ou liquides de compositions basaltique,rhyolitique et phonolitique,entre 900°C et 1300°C,a pression ordinaire     

Chantal Alibert  Jean-Paul Carron 《Earth and Planetary Science Letters》1980,47(2):294-306

Diffusion coefficients for Si, Ti, Al, Na, K, Ca, Mg and Fe between pairs of glasses of basaltic, rhyolitic or phonolitic compositions have been determinated experimentally. This method involves the heating of coaxial cylinders of paired glasses under atmospheric conditions, over a range of temperatures from 900 to 1300°C, followed by microprobe analysis determination of the concentration gradients across the interface.The measured diffusivities are similar for all cations and range from 10^?13 cm²/s at 900°C to 5 × 10^?9 cm²/s at 1300°C. Depending mainly on the composition contrast, the diffusion is characterized by asymmetrical concentration profiles. This peculiar feature increases with temperature and chemical gradients across the contact surface of the glasses and leads to higher diffusion coefficients (D) in the more “basic” glass of a given pair. In the case of the rhyolite-basalt couple, this variation increases by a factor of about 10 at 1300°C. Diffusion dependence on temperature follows an Arrhenius equation which gives activation energies ranging from 65 to 85 kcal/mole. Assuming a constant and overall D for the two glasses we have attempted to apply our results to some geological examples such as exchanges between molten enclaves and liquids of contrasting composition.  相似文献