Structural and geochemical data on the Rio Magno Unit: evidence for a new 'Apenninic' ophiolitic unit in Alpine Corsica and its geodynamic implications     

Elisa Padoa  Emilio Saccani  & Michel Durand-Delga 《地学学报》2001,13(2):135-142

The Rio Magno Unit (RMU) tectonically overlies the Schistes Lustrés units in south-eastern Alpine Corsica. It is represented by an ophiolitic sequence, showing remarkable differences with respect to the commonly recognized Corsican ophiolites. This unit can be distinguished from the Schistes Lustrés by the lack of HP–LT metamorphism, reflecting its different geodynamic setting, although both were involved early in the same tectonic events. Similarly, the RMU can be distinguished from the Balagne Unit by the presence of normal-MORB basalts and the scarcity of continent-derived sedimentary input, testifying to a different oceanic palaeogeographical setting. Moreover, the petrochemical and stratigraphic features of the RMU ophiolitic sequence show close analogies with the Internal Ligurides of the Northern Apennines. The RMU represents the first record of a nonmetamorphic 'Apenninic'-type ophiolitic unit in Alpine Corsica, supporting the hypothesis that the Alpine Corsica – Northern Apennine system represents a double-vergent accretionary wedge.  相似文献   

Nouvelle hypothèse sur l'origine des formations géologiques de l'île de Timor (Sud-Est asiatique)     

Michel Villeneuve  Jean-Jacques Corne  Rossana Martini  Louisette Zaninetti 《Comptes Rendus Geoscience》2004,336(16):1511-1520

Similar lithological and tectonic features indicate that Timor and Sulawesi islands were part of the same continental block. Timor was in the southern part of Sulawesi, then separated during Late Miocene time during the opening of the South Banda Sea basin. At this time Timor evolved as a part of an Upper Miocene volcanic arc that collided the Australian plate at the end of the Lower Pliocene (3.5 Ma). To cite this article: M. Villeneuve et al., C. R. Geoscience 336 (2004).  相似文献   

Coseismic slip resolution and post-seismic relaxation time of the 1999 Chi-Chi, Taiwan, earthquake as constrained by geological observations, geodetic measurements and seismicity   总被引：2，自引：0，他引：2  

Anne Loevenbruck  Rodolphe Cattin  Xavier Le Pichon  Stéphane Dominguez  Rémi Michel 《Geophysical Journal International》2004,158(1):310-326

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Indication of the uplift of the Ardenne in long-term gravity variations in Membach (Belgium)     

Olivier Francis  Michel Van Camp  Tonie van Dam  René Warnant  Marc Hendrickx 《Geophysical Journal International》2004,158(1):346-352

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A test of the integrity of metal records in sediment cores based on the documented history of metal contamination in Lac Dufault (Québec, Canada)     

Yves Couillard  Michel Courcelles  Antonella Cattaneo  Sybille Wunsam 《Journal of Paleolimnology》2004,32(2):149-162

There is an important volume of published information on Lac Dufault (Québec) which describes the history of metal inputs over 70 years and the changes that occurred in the lake as a result of this contamination. We used this abundant source of chronological markers to test the hypothesis that lake sediments can provide true historical records of trace metal loading from metal mining. Sediment cores were obtained from the deepest zone of the lake (19 m). The sediments were dated using ²¹⁰Pb and ¹³⁷Cs and they were analyzed for total elemental concentrations (Ca, Cd, Cu, Fe, P, Pb, S, Zn). Metal profiles in the sediment core preserved the distinct signatures of different mine exploitations documented in the lake watershed. In particular, the core recorded: the beginning of industrialization in 1926; increasing sedimentation rates associated with perturbations in the lake watershed; the maximum of sediment [Cu] and the contemporary exploitation of ore bodies rich in Cu; the maximum of sediment [Fe] and the contemporary production of pyrite by a mining operation; the low sediment [Cu] and [Zn] in the 1950s and the low contemporary production of these metals by mining operations; the maximum of sediment [Cd] and the contemporary production of Cd by a subsequent mining operation. Anomalies in the distribution of ²¹⁴Pb activities in sediments reflected the intensity of acid mine drainage (AMD). There is good evidence that the lake resisted acidification from this AMD for the last thirty years. Overall, our results support the thesis that profiles of sedimentary Cd, Cu, Zn, Pb and Fe levels reflect the past history of metal input to Lac Dufault.  相似文献   

Surface Matching and Change Detection Using a Modified Hough Transformation for Robust Parameter Estimation   总被引：3，自引：0，他引：3  

Ayman F. Habib  Yong-Ran Lee  & Michel Morgan 《The Photogrammetric Record》2001,17(98):303-315

Many photogrammetric and GIS applications, such as city modelling, change detection and object recognition, deal with surfaces. Change detection involves looking for differences between two surface models that are obtained from different sensors, for example an optical sensor and a laser scanner, or by the same sensor at different epochs. Surfaces obtained through a sampling process may also have to be compared for future processing (for example transformation parameter estimation and change detection). Surface matching is therefore an essential task in these applications. The matching of surfaces involves two steps. The first step deals with finding the correspondences between two surface points and/or patches. The second step requires the determination of transformation parameters between the two surfaces. However, since most surfaces consist of randomly distributed discrete points and may have different reference systems, finding the correspondences cannot be achieved without knowing the transformation parameters between the two surfaces. Conversely, deriving the transformation parameters requires the knowledge of the correspondence between the two point sets. The suggested approach for surface matching deals with randomly distributed data sets without the need for error prone interpolation and requires no point-to-point correspondence between the two surfaces under consideration. This research simultaneously solves for the correspondence and the transformation parameters using a Modified Iterated Hough Transform for robust parameter estimation. Several experiments are conducted to prove the feasibility and the robustness of the suggested approach, even when a high percentage of change exists.  相似文献   

Experimental fragmentation of crystal- and vesicle-bearing silicic melts     

Caroline Martel  Donald B. Dingwell  Oliver Spieler  Michel Pichavant  Max Wilke 《Bulletin of Volcanology》2001,63(6):398-405

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Compaction in a mantle with a very small melt concentration: Implications for the generation of carbonatitic and carbonate-bearing high alkaline mafic melt impregnations     

Michel RabinowiczYanick Ricard  Michel Grégoire 《Earth and Planetary Science Letters》2002,203(1):205-220

Xenoliths entrained in alkaline basalts and kimberlites give strong evidence that mantle carbonatitic and carbonated high alkaline mafic silicate melts, which are initially produced at very low degrees of partial melting (?1%), percolate and accumulate to form impregnations with a melt concentration of up to 10%. At present no compaction model has explained such huge local amplification of melt concentration. Recently, Bercovici et al. [1] have shown that the commonly used equations of compaction are not sufficiently general to describe all melt percolation processes in the mantle. In particular, they show that, when the melt concentration in the mantle is very low, the pressure jump ΔP between the solid and liquid fractions of the mantle mush is very important and plays a driving role during compaction. 1-D compaction waves generated with two different systems of equations are computed. Three types of wave-trains are observed, i.e. (1) sinusoidal waves; (2) periodic waves with flat minima and very acute maxima (‘witch hat waves’); (3) periodic solitary waves with flat maxima and extremely narrow minima (‘bowler hat waves’). When the initial melt distribution in the mantle is quite homogeneous, the compaction waves have sinusoidal shapes and can locally amplify the melt concentration by a factor less than two. When there is a drastic obstruction at the top of the wetted domain, the pressure jump ΔP between solid and liquid controls the shape of the waves. If the computation assumes the equality of pressure between the two phases (ΔP=0), the compaction wave has a ‘bowler hat shape’, and locally amplifies the melt concentration by a factor less than 5. Alternatively, simulations taking into account the pressure jump between phases ΔP predict compaction waves with ‘witch hat shape’. These waves collect a large quantity of melt promoting the development of magmons with local melt concentration exceeding 100× the background melt concentration. It is inferred that in a mantle with very low concentrations of carbonatitic or high alkaline mafic silicate melt the magmons are about 1 km thick and reach, in less than 1 Ma, a melt concentration of about 10%. The magmons are likely generated below the lithosphere at some distance away from the center of hot spots. This can explain the development of mantle carbonatitic eruptions in the African rift and the carbonatite and high alkaline mafic silicate volcanic activity in oceanic islands.  相似文献   

Building damage from the Marmara, Turkey earthquake of August 17, 1999     

Michel Bruneau 《Journal of Seismology》2002,6(3):357-377

The objective of this paper is to provide a brief overview of damage as observed immediately following the earthquake. Detailed studies of structural seismic performance, conducted in the time elapsed since August 1999, are not the subject of this paper, but rather the object of other papers presented in this Special Issue of the Journal. Damage to reinforced concrete, masonry, and steel structures, is described. The mode the failure presented include: foundation failures; soft stories; strong beams and weak columns; lack of column confinement and poor detailing practice; buckling and fractures of steel members; and non-structural damage. Some general lessons learned from this earthquake are also formulated.  相似文献   

A Tertiary asthenospheric flow beneath the southern French Massif Central indicated by upper mantle seismic anisotropy and related to the west Mediterranean extension   总被引：1，自引：0，他引：1  

Guilhem Barruol  Michel Granet 《Earth and Planetary Science Letters》2002,202(1):31-47

Upper mantle flow beneath the French Massif Central is investigated using teleseismic shear wave splitting induced by seismic anisotropy. About 25 three-component stations (short period, intermediate and broadband) were installed during the period 1998-1999 in the southern Massif Central, from the Clermont Ferrand volcanic area to the Mediterranean Sea. Teleseismic shear waves (SKS, SKKS and PKS) were used to determine the splitting parameters: the fast polarization direction and the delay time. Delay times ranging between 0.7 and 1.5 s have been observed at most of the sites. The azimuths of the fast split shear waves trend homogeneously NW-SE in the southern Massif Central suggesting a homogeneous mantle flow beneath this area. The observed NW-SE direction differs from the N100°E Pyrenean anisotropy further south. It does not appear to be correlated to Hercynian structures nor to the present-day motion of the plate but is well correlated to the Tertiary extension direction. We propose that the opening of the western Mediterranean induced by the rotation of the Corsica-Sardinia lithospheric block and the roll-back to the SE of the Tethys slab may have generated a large asthenospheric mantle flow beneath the southern Massif Central and a deflection of the up going plume centered beneath the northern Massif Central toward the SE.  相似文献