Late Hercynian–Mesozoic thinning in the Alboran domain: metamorphic data from the northern Rif, Morocco     

André Michard  Bruno Goffé  Mohamed Bouybaouene  & Omar Saddiqi 《地学学报》1997,9(4):171-174

In the Alboran domain, two crustal-thickening late-orogenic extension cycles are superposed. The importance of the late Alpine thinning of the Alpujarride-Sebtide crustal section on top of the Beni Bousera peridotites is discussed here in metamorphic petrological terms. The Alpine metamorphism operated first under a HP–LT gradient, and reached the eclogite facies in the Permian–Triassic phyllites, before retrogression under a high geothermal gradient. A contrasting, higher temperature metamorphism characterizes the pre-Permian section, reaching the HP-granulite facies at the bottom of the crustal section. By reference to the western European setting, the granulites relate to the Hercynian orogeny, as supported by the isotopic ages of the enclosed, armoured monazite crystals. Thus, thinning of an overthickened crust might have occurred there during the late Hercynian extension and Tethyan opening, before being reactivated during the late Oligocene.  相似文献   

Delivery and deposition of organic matter in surface sediments of Lagoa do Caçó (Brazil)     

Abdelfettah Sifeddine  Renato Campello Cordeiro

  Ana Luiza S. Albuquerque
  Marcelo Bernardes
  Bruno Turcq
  Jorge João Abrão
《Journal of Paleolimnology》2011,45(3):385-396

Elemental and isotopic compositions of organic matter in surficial sediments from five transects across Lagoa do Caçó (Brazil) were analyzed to identify the depth-related processes that affect the production and deposition of sedimentary organic matter in this shallow tropical lake. Each of four transverse transects began at a margin dominated by aquatic macrophytes (Eleocharis), crossed the central deep part of the lake, and terminated in the opposite, macrophyte-dominated margin. In each transect, TOC concentrations, C/N ratios, and δ¹³C values decreased between 0 and 4 m, whereas δ¹⁵N values increased. The variables remained stable in sediment from 4 m water depth to the center of the lake at 10 m. The depth-related patterns reflect differences in both the delivery and the deposition of organic matter in the lake. Organic matter is produced in abundance in the marginal area by emersed and submerged macrophyte vegetation that diminishes with depth and disappears at 4 meters. After the disappearance of macrophytes, organic matter is produced at low rates principally by open-lake phytoplankton. Drawdown of dissolved oxygen is high in the lake margins, but it is low in the oligotrophic open waters of the lake. Preservation of organic matter is consequently better in sediments of the lake margins than in deep waters. The depth-related pattern of organic matter delivery and deposition in the sediments of Lagoa do Caçó, in which water levels are sensitive to groundwater fluctuations, shows that the elemental and isotopic compositions of sediment organic matter can provide a record of changes in the paleohydrology of this and other similar shallow lake systems.  相似文献   

The 1.10- and 1.18-μm nightside windows of Venus observed by SPICAV-IR aboard Venus Express     

Bruno Bézard  Anna Fedorova  Jean-Loup Bertaux  Alexander Rodin  Oleg Korablev 《Icarus》2011,216(1):173-183

Observations of the 1.10- and 1.18-μm nightside windows by the SPICAV-IR instrument aboard Venus Express were analyzed to characterize the various sources of gaseous opacity and determine the H₂O mole fraction in the lower atmosphere of Venus. We showed that the line profile model of Afanasenko and Rodin (Afanasenko, T.S., Rodin, A.V. [2007]. Astron. Lett. 33, 203–210) underestimates the CO₂ absorption in the high-wavelength wing of the 1.18-μm window and we derived an empirical lineshape that matches this wing well. An additional continuum opacity is required to reproduce the variation of the 1.10- and 1.18-μm radiances with surface elevation as observed by the VIRTIS-M instrument aboard Venus Express. A constant absorption coefficient of 0.7 ± 0.2 × 10⁻⁹ cm⁻¹ am⁻² best reproduces the observed variation. We compared spectra calculated with different CO₂ and H₂O line lists. We found that the CDSD line list lacks the 5ν₁ + ν₃ series of CO₂ bands, which provide significant opacity in Venus’ deep atmosphere, and we have constructed a composite line list that best reproduces the observations. We also showed for the first time that HDO brings significant absorption at 1140–1190 nm. Using the best representation of the atmospheric opacity we could reach, we retrieved a water vapor mole fraction of ppmv, pertaining to the altitude range 5–25 km. Combined with previous measurements in the 1.74- and 2.3-μm windows, this result provides strong evidence for a uniform H₂O profile below 40 km, in agreement with chemical models.  相似文献   

Mercury resolved spectroscopy from NTT     

Stéphane Erard  Bruno Bézard  Alain Doressoundiram  Daniela Despan 《Planetary and Space Science》2011,59(15):1842-1852

Mercury has been observed in June 2006 with the SofI instrument at NTT. Resolved spectroscopy was performed in the range. The observations were acquired close to a favorable quadrature with maximum elongation, and span mostly the southern hemisphere in the 235–315°E longitude area.In contrast to recent observations from IRTF, the present study does not indicate any pyroxene absorption in the near-infrared range, neither in the region nor at . Detailed spectral analysis allows to derive an upper limit of 1.5% type-A pyroxene (hedenbergite) or 1.1% enstatite (assuming minimum lunar iron content) in the regions observed, at the 700 km scale. Assuming lunar-like maturity effects on band depth, this corresponds to an upper limit of 0.15 and 0.6 wt.% FeO content in silicates, an order of magnitude less than previous estimates.  相似文献   

Changes in Nutrient Biogeochemistry in Response to the Regression of Zostera noltii Meadows in the Arcachon Bay (France)     

Marie-Lise Delgard  Bruno Deflandre  Jonathan Deborde  Marion Richard  Céline Charbonnier  Pierre Anschutz 《Aquatic Geochemistry》2013,19(3):241-259

From 1989 to 2007, a severe decline in Zostera noltii meadows was reported in the Arcachon Bay, with an accelerated regression after 2005. We investigated the inter-annual variability of the biogeochemistry of the sediment in an area affected by seagrass decline. In late summer and in winter of the years 2006, 2010, and 2011, sediment cores were collected at low tide on vegetated and adjacent non-vegetated sediments located in the eastern part of the Arcachon Bay. The geochemical analyses of sediment solid-phase organic carbon, reactive P and Fe, and the pore water concentrations of Fe²⁺, DIP, and NH₄ ⁺ are presented. The changes in the chemistry of sediment and pore water between 2006 and 2010 are interpreted as a consequence of the decrease in the Z. noltii biomass between 2006 and 2010. The absence of significant seasonal variations in biomass throughout the growth period (March–September) in 2011 is most likely related to the regression of Z. noltii meadow that strongly affects the study area. In contrast to the healthy meadow in 2006, the declining meadow favored the dissolution of sedimentary particulate phosphorus in winter. In late summer, the low biomass of seagrass resulted in a net release of ammonium in the pore water of the upper 20 cm of sediment. This study clearly shows that seagrass decay may enhance nutrient release in sediments, resulting in a significant supply of phosphorus to the water column of a magnitude comparable to annual inputs to the lagoon from the rivers and the tidal pump.  相似文献   

AVES: A high performance computer cluster array for the INTEGRAL satellite scientific data analysis     

Memmo Federici  Bruno Luigi Martino  Pietro Ubertini 《Experimental Astronomy》2012,34(1):105-121

In this paper we describe a new computing system array, designed, built and now used at the Space Astrophysics and Planetary Institute (IAPS) in Rome, Italy, for the INTEGRAL Space Observatory scientific data analysis. This new system has become necessary in order to reduce the processing time of the INTEGRAL data accumulated during the more than 9 years of in-orbit operation. In order to fulfill the scientific data analysis requirements with a moderately limited investment the starting approach has been to use a ??cluster?? array of commercial quad-CPU computers, featuring the extremely large scientific and calibration data archive on line.  相似文献   

Monte Carlo Markov Chain parameter estimation in semi-analytic models of galaxy formation     

Bruno M. B. Henriques  Peter A. Thomas  Seb Oliver  Isaac Roseboom 《Monthly notices of the Royal Astronomical Society》2009,396(1):535-547

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Coordinated Study on Solar Wind Turbulence During the Venus-Express, ACE and Ulysses Alignment of August 2007     

R. Bruno  V. Carbone  Z. Vörös  R. D’Amicis  B. Bavassano  M. B. Cattaneo  A. Mura  A. Milillo  S. Orsini  P. Veltri  L. Sorriso-Valvo  T. Zhang  H. Biernat  H. Rucker  W. Baumjohann  D. Jankovičová  P. Kovács 《Earth, Moon, and Planets》2009,104(1-4):101-104

At the end of August 2007, Venus, Earth and Ulysses were aligned within a few degrees. This unusual event gives the opportunity to attempt a coordinated study on the radial evolution of solar wind turbulence and coronal transients like CMEs between 0.7 and 1.4 AU. Interplanetary magnetic field data and moments of proton velocity distribution function such as density, speed and temperature are required for this programme and will be provided by ACE at Earth, Venus Express at Venus and Ulysses at 1.4 AU. This project has been recently proposed as a Coordinated Investigation Programme (CIP35) for the International Heliophysical Year.  相似文献   

Discussion on “Effects of different drying rates on shrinkage characteristics of a residual soil and soil mixtures” by Henry Krisdani, Harianto Rahardjo, Eng-Choon Leong [Engineering Geology 102 (2008) 31–37]     

Mamert Mbonimpa  Michel Aubertin  Bruno Bussire 《Engineering Geology》2009,107(3-4):172-173

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Low-pH waters discharging from submarine vents at Panarea Island (Aeolian Islands,southern Italy) after the 2002 gas blast: Origin of hydrothermal fluids and implications for volcanic surveillance     

Franco Tassi  Bruno Capaccioni  Giorgio Caramanna  Daniele Cinti  Giordano Montegrossi  Luca Pizzino  Fedora Quattrocchi  Orlando Vaselli 《Applied Geochemistry》2009

A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out from December 2002 to March 2007, in order to investigate (i) the geochemical processes controlling the chemical composition of the hydrothermal fluids and (ii) the possible relations between the chemical features of the hydrothermal reservoir and the activity of the magmatic system. Compositional data of the thermal water samples were integrated in a hydrological conceptual model, which describes the formation of the vent fluid by mixing of seawater, seawater concentrated by boiling, and a deep, highly-saline end-member, whose composition is regulated by water-rock interactions at relatively high temperature and shows clear clues of magmatic-related inputs. The chemical composition of concentrated seawater was assumed to be represented by that of the water sample having the highest Mg content. The composition of the deep end-member was instead calculated by extrapolation assuming a zero-Mg end-member. The Na–K–Ca geothermometer, when applied to the thermal end-member composition, indicated an equilibrium temperature of approximately 300 °C, a temperature in agreement with the results obtained by gas-geothermometry.  相似文献