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1.
Results of several fits of the lunar theory ELP 2000-82B and of Moons' theory of libration are presented. The theories are fitted both to JPL numerical integrations and to LLR observations 相似文献
2.
Jérôme Nomade Emmanuel Chapron Marc Desmet Jean-Louis Reyss Fabien Arnaud Vincent Lignier 《地学学报》2005,17(4):350-357
Sediment archives from a mountain lake are used as indicators of seismotectonic activity in the Grenoble area (French western Alps, 45°N). Sedimentological analysis (texture and grain-size characteristics) exhibits several layers resulting from instantaneous deposits in Lake Laffrey: six debris flow events up to 8 cm thick can be attributed to slope failure along the western flank of the basin. Dating with 210Pb and 137Cs gamma counting techniques and the reconnaissance of historical events, provide a constrained age-depth model. Over the last 250 years, five of such debris flow deposits could be related to historical earthquakes of MSK intensities greater than VI over an area of <60 km. One debris flow deposit triggered at the beginning of the last century can be related to an historical landslide possibly triggered by the artificial regulation of the lake level. 相似文献
3.
This paper deals with the formation processes and the palaeoenvironmental significance of relict slope deposits located on the uppermost part of the north Portugal mountains. For this purpose, seven key sites representative of the different lithofacies have been selected and analysed in detail. The data show that three main dynamic processes are responsible for the emplacement of regional fossil slope deposits: runoff, debris flows and dry grain flows. The ubiquity of these processes and the lack of frost‐related features or landforms do not support the existence of severe Pleistocene climates in this part of the lberian Peninsula as postulated by previous work. Pedological data gathered at one of the study sites show that a subalpine environment was probably present at 700–800 m altitude between 29 and 14 kyr. Using data from the Pyrenees Mountains, a 6.5 to 12°C depression in mean annual temperature has been tentatively postulated for this Pleniglacial period. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
Philippe CARREZ Karine DEMYK Patrick CORDIER Lon GENGEMBRE Jean GRIMBLOT Louis D'HENDECOURT Anthony P. JONES Hugues LEROUX 《Meteoritics & planetary science》2002,37(11):1599-1614
Abstract— We present the results of irradiation experiments aimed at understanding the structural and chemical evolution of silicate grains in the interstellar medium. A series of He+ irradiation experiments have been performed on ultra‐thin olivine, (Mg,Fe)2SiO4, samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using analytical transmission electron microscopy. Our results show that olivine is amorphized by low‐energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease of the atomic ratios O/Si and Mg/Si as determined by x‐ray photoelectron spectroscopy and by x‐ray energy dispersive spectroscopy. This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation of metallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation‐induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, that is, at different stages of their evolution: chemical and structural evolution in the interstellar medium, from olivine to pyroxene‐type and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates. 相似文献
5.
Steven J. Ostro Lance A. M. Benner Christopher Magri Jon D. Giorgini Randy Rose Raymond F. Jurgens Donald K. Yeomans Alice A. Hine Michael C. Nolan Daniel J. Scheeres Stephen B. Broschart Mikko Kaasalainen Jean‐Luc Margot 《Meteoritics & planetary science》2005,40(11):1563-1574
Abstract— We present June 2004 radar images of asteroid 25143 Itokawa (1998 SF36) that improve upon the longitude‐latitude coverage of images obtained in 2001 by Ostro et al. (2004) and use the 2001–2004 data to refine that paper's constraints on Itokawa's shape. The 2004 images, the first of the asteroid's southern side, look distinctly different from the 2001 images, revealing leading edges that are much more curved and rugged than the nearly convex leading edges seen at northern latitudes in 2001. Itokawa is shaped like a slightly asymmetrical, bent, lumpy ellipsoid with dimensions along the principal axes within 10% of 594 times 320 times 288 m. To illustrate the uncertainty space associated with shape reconstruction from images with suboptimal orientational coverage, we present two alternative three‐dimensional models of the object. 相似文献
6.
Yannick Giraud-Héraud Jean Kaplan François De Volnay Martin Charling Tao Sylvaine Turck-Chièze 《Solar physics》1990,128(1):21-33
The Saclay solar evolution code is used to check the effect of WIMPs on solar evolution. In this paper we study the effects of various types of Cosmion-matter interactions, give constraints on the crosssections compatible with the measured neutrino rate of 2 SNU on chlorine, and relate these constraints to ongoing dark matter detection experiments.Unité associée au CNRS UA 280, F-75251 Paris Cedex 05, France.On leave from LPC, Collège de France. 相似文献
7.
Eloïse Gaillou Aurlien Delaunay Benjamin Rondeau Martine Bouhnik-le-Coz Emmanuel Fritsch Guy Cornen Christophe Monnier 《Ore Geology Reviews》2008,34(1-2):113
Seventy-seven gem opals from ten countries were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) through a dilution process, in order to establish the nature of the impurities. The results are correlated to the mode of formation and physical properties and are instrumental in establishing the geographical origin of a gem opal. The geochemistry of an opal is shown to be dependant mostly on the host rock, at least for examples from Mexico and Brazil, even if modified by weathering processes. In order of decreasing concentration, the main impurities present are Al, Ca, Fe, K, Na, and Mg (more than 500 ppm). Other noticeable elements in lesser amounts are Ba, followed by Zr, Sr, Rb, U, and Pb. For the first time, geochemistry helps to discriminate some varieties of opals. The Ba content, as well as the chondrite-normalized REE pattern, are the keys to separating sedimentary opals (Ba > 110 ppm, Eu and Ce anomalies) from volcanic opals (Ba < 110 ppm, no Eu or Ce anomaly). The Ca content, and to a lesser extent that of Mg, Al, K and Nb, helps to distinguish gem opals from different volcanic environments. The limited range of concentrations for all elements in precious (play-of-color) compared to common opals, indicates that this variety must have very specific, or more restricted, conditions of formation. We tentatively interpreted the presence of impurities in terms of crystallochemistry, even if opal is a poorly crystallized or amorphous material. The main replacement is the substitution of Si4+ by Al3+ and Fe3+. The induced charge imbalance is compensated chiefly by Ca2+, Mg2+, Mn2+, Ba2+, K+, and Na+. In terms of origin of color, greater concentrations of iron induce darker colors (from yellow to “chocolate brown”). This element inhibits luminescence for concentrations above 1000 ppm, whereas already a low content in U (≤ 1 ppm) induces a green luminescence. 相似文献
8.
Spatial variations in grain-size parameters (i.e. grain-size trends) contain information on sediment transport patterns. Analytical procedures have been proposed using the grain-size trend to determine net sediment transport pathways. In the first part of this study, the fundamentals of the theory are presented through methods for analysing 1D and 2D variations. The methods used are critically discussed, while pointing out some severe problems. So far, these methods suffer from limitations leading to serious interpretational errors, making it necessary to take account of two kinds of uncertainties. Inputs uncertainties are linked to the physical sediment properties as well as procedures of sampling and analysis. Model uncertainties are then discussed for each step of the grain-size trend analysis. The validity of Sediment Trend Analysis under natural conditions is tested against published field studies to determine the most appropriate variation trend to use in a specific environment. Proposals are given for each step of the procedure for optimal use of the method using a Quality Assurance (QA) approach. Further developments are proposed, such as integration into a Geographic Information System. 相似文献
9.
Magnesium isotope systematics of the lithologically varied Moselle river basin, France 总被引:2,自引:0,他引:2
Agnès Brenot Christophe Cloquet Nathalie Vigier Jean Carignan Christian France-Lanord 《Geochimica et cosmochimica acta》2008,72(20):5070-5089
Magnesium and strontium isotope signatures were determined during different seasons for the main rivers of the Moselle basin, northeastern France. This small basin is remarkable for its well-constrained and varied lithology on a small distance scale, and this is reflected in river water Sr isotope compositions. Upstream, where the Moselle River drains silicate rocks of the Vosges mountains, waters are characterized by relatively high 87Sr/86Sr ratios (0.7128-0.7174). In contrast, downstream of the city of Epinal where the Moselle River flows through carbonates and evaporites of the Lorraine plateau, 87Sr/86Sr ratios are lower, down to 0.70824.Magnesium in river waters draining silicates is systematically depleted in heavy isotopes (δ26Mg values range from −1.2 to −0.7‰) relative to the value presently estimated for the continental crust and a local diorite (−0.5‰). In comparison, δ26Mg values measured in soil samples are higher (∼0.0‰). This suggests that Mg isotope fractionation occurs during mineral leaching and/or formation of secondary clay minerals. On the Lorraine plateau, tributaries draining marls, carbonates and evaporites are characterized by low Ca/Mg (1.5-3.2) and low Ca/Sr (80-400) when compared to local carbonate rocks (Ca/Mg = 29-59; Ca/Sr = 370-2200), similar to other rivers draining carbonates. The most likely cause of the Mg and Sr excesses in these rivers is early thermodynamic saturation of groundwater with calcite relative to magnesite and strontianite as groundwater chemistry progressively evolves in the aquifer. δ26Mg of the dissolved phases of tributaries draining mainly carbonates and evaporites are relatively low and constant throughout the year (from −1.4‰ to −1.6‰ and from −1.2‰ to −1.4‰, respectively), within the range defined for the underlying rocks. Downstream of Epinal, the compositions of the Moselle River samples in a δ26Mg vs. 87Sr/86Sr diagram can be explained by mixing curves between silicate, carbonate and evaporite waters, with a significant contribution from the Vosgian silicate lithologies (>70%). Temporal co-variation between δ26Mg and 87Sr/86Sr for the Moselle River throughout year is also observed, and is consistent with a higher contribution from the Vosges mountains in winter, in terms of runoff and dissolved element flux. Overall, this study shows that Mg isotopes measured in waters, rocks and soils, coupled with other tracers such as Sr isotopes, could be used to better constrain riverine Mg sources, particularly if analytical uncertainties in Mg isotope measurements can be improved in order to perform more precise quantifications. 相似文献
10.
Philippe E. Raison Regis Jardin Daniel Bouëxière Rudy J. M. Konings Thorsten Geisler Claudiu C. Pavel Jean Rebizant Karin Popa 《Physics and Chemistry of Minerals》2008,35(10):603-609
The crystallographic structures of the synthetic cheralite, CaTh(PO4)2, and its homolog CaNp(PO4)2 have been investigated by X-ray diffraction at room temperature. Rietveld analyses showed that both compounds crystallize in the monoclinic system and are isostructural to monazite LnPO4 (Ln = La to Gd). The space group is P21/n (I.T. = 14) with Z = 2. The refined lattice parameters of CaTh(PO4)2 are a = 6.7085(8) Å, b = 6.9160(6) Å, c = 6.4152(6) Å, and β = 103.71(1)° with best fit parameters R wp = 4.87%, R p = 3.69% and R B = 3.99%. For CaNp(PO4)2, we obtained a = 6.6509(5) Å, b = 6.8390(3) Å, c = 6.3537(8) Å, and β = 104.12(6)° and R wp = 6.74%, R p = 5.23%, and R B = 6.05%. The results indicate significant distortions of bond length and angles of the PO4 tetrahedra in CaTh(PO4)2 and to a lesser extent in CaNp(PO4)2. The structural distortions were confirmed by Raman spectroscopy of CaTh(PO4)2. A comparison with the isostructural compounds LnPO4 (Ln = Ce and Sm) confirmed that the substitution of the large rare earth trivalent cations with Ca2+ and Th4+ introduces a distortion of the PO4 tetrahedra. 相似文献