Polyphase wrench tectonics in the southern french Massif Central: kinematic inferences from pre- and syntectonic granitoids     

Jean-Yves Roig  Michel Faure  Patrick Ledru 《International Journal of Earth Sciences》1996,85(1):138-153

In the Variscan French Massif Central, the South Limousin area consists of low- to medium-grade metamorphic rocks intruded by two granitic bodies. The structural and textural analyses of these plutons undertaken in parallel with the structural analysis of their host rocks allow us to characterize and to date different stages in the tectonic evolution of this area. This study shows that the South Limousin area experienced successivelly two strike-slip events along two geographically distinct shear zones, from north to south the left-lateral Estivaux and the right-lateral South Limousin strike-slip faults, respectively. These ductile faults subdivide the South Limousin into three structural units, from north to south they are the Upper Gneiss unit, Thiviers-Payzac unit .and Génis unit. The two granitic bodies intrude the Thiviers-Payzac unit only. The younger Estivaux granite is a syntectonic pluton which emplaced during left-lateral wrenching. ⁴⁰Ar/³⁹Ar dates from biotites indicate an Early Carboniferous age (346 ± 3 Ma). The older granite is a pretectonic body. It is the Ordovician Saut du Saumon augen orthogneiss in which detailed structural analyses show the polyphase nature of the solid-state deformation. Our microtectonic data indicate that the right-lateral motions overprint the left-lateral ones and produce apparently symmetrical fabrics.  相似文献   

The dammed Hikurangi Trough: a channel-fed trench blocked by subducting seamounts and their wake avalanches (New Zealand–France GeodyNZ Project)     

Keith B. Lewis  Jean-Yves Collot  & Serge E. Lallem 《Basin Research》1998,10(4):441-468

The Hikurangi Trough, off eastern New Zealand, is at the southern end of the Tonga–Kermadec–Hikurangi subduction system, which merges into a zone of intracontinental transform. The trough is mainly a turbidite-filled structural trench but includes an oblique-collision, foredeep basin. Its northern end has a sharp boundary with the deep, sediment-starved, Kermadec Trench. Swath-mapping, sampling and seismic surveys show modern sediment input is mainly via Kaikoura Canyon, which intercepts littoral drift at the southern, intracontinental apex of the trough, with minor input from seep gullies. Glacial age input was via many canyons and about an order of magnitude greater. Beyond a narrow, gravelly, intracontinental foredeep, the southern trench-basin is characterized by a channel meandering around the seaward edge of mainly Plio-Pleistocene, overbank deposits that reach 5 km in thickness. The aggrading channel has sandy turbidites, but low-backscatter, and long-wavelength bedforms indicating thick flows. Levées on both sides are capped by tangentially aligned mudwaves on the outsides of bends, indicating centrifugal overflow from heads of dense, fast-moving, autosuspension flows. The higher, left-bank levée also has levée-parallel mudwaves, indicating Coriolis and/or boundary currents effects on dilute flows or tail plumes. In the northern trough, basin-fill is generally less than 2 km thick and includes widespread overbank turbidites, a massive, blocky, avalanche deposit and an extensive, buried, debris flow deposit. A line of low seamounts on the subducting plate acts as a dam preventing modern turbidity currents from reaching the Kermadec Trench. Major margin collapse probably occurred in the wake of a large subducting seamount; this seamount and its wake debris flow probably dammed the trench from 2 Ma to 0.5 Ma. Before this, similar dams may have re-routed turbidity currents across the plateau.  相似文献   

Radiative properties of stellar plasmas and open challenges     

S. Turck-Chi??ze  G. Loisel  D. Gilles  L. Piau  C. Blancard  T. Blenski  M. Busquet  T. Caillaud  P. Coss??  F. Delahaye  G. Faussurier  J. Fariaut  F. Gilleron  J. A. Guzik  J. Harris  D. P. Kilcrease  N. H. Magee  J. C. Pain  Q. Porcherot  M. Poirier  G. Soullier  C. J. Zeippen  S. Bastiani-Ceccotti  C. Reverdin  V. Silvert  F. Thais  B. Villette 《Astrophysics and Space Science》2011,336(1):103-109

The lifetime of solar-like stars, the envelope structure of more massive stars, and stellar acoustic frequencies largely depend on the radiative properties of the stellar plasma. Up to now, these complex quantities have been estimated only theoretically. The development of the powerful tools of helio- and astero- seismology has made it possible to gain insights on the interiors of stars. Consequently, increased emphasis is now placed on knowledge of the monochromatic opacity coefficients. Here we review how these radiative properties play a role, and where they are most important. We then concentrate specifically on the envelopes of ?? Cephei variable stars. We discuss the dispersion of eight different theoretical estimates of the monochromatic opacity spectrum and the challenges we need to face to check these calculations experimentally.  相似文献   

Simulations of accidental coal immersion     

Jaffrennou C  Giamarchi P  Cabon JY  Stephan L  Burel-Deschamps L  Bautin F  Thomas A  Dumont J  Le Floch S 《Marine pollution bulletin》2007,54(12):1932-1939

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L⁻¹), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L⁻¹. Fortunately, the results show that the environmental impact of this type of accident would remain limited.  相似文献   

Updated opacities from the Opacity Project     

N. R. Badnell  M. A. Bautista  K. Butler  F. Delahaye  C. Mendoza  P. Palmeri †  C. J. Zeippen  M. J. Seaton 《Monthly notices of the Royal Astronomical Society》2005,360(2):458-464

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X-ray absorption via Kα resonance complexes in oxygen ions     

Anil K. Pradhan  Guo Xin Chen  Franck Delahaye  Sultana N. Nahar  Justin Oelgoetz 《Monthly notices of the Royal Astronomical Society》2003,341(4):1268-1271

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A study of marine pollution caused by the release of metals into seawater following acid spills     

Jean-Yves Cabon  Stephane Le Floch 《Marine pollution bulletin》2010,60(7):998-1004

This study examined the potential metal pollution induced by the accidental spill of different acids into seawater. The acids sink to the bottom according to their densities and subsequently react with marine sediments. The acids selected for this study were acetic, hydrochloric, nitric, sulfuric, and phosphoric acids; the metallic elements selected were Cr, Cu, Fe, Mn, Pb and Zn. The sediment was collected in Brest Harbour. The percentages of metals released from this sediment in the presence of various concentrations of acids in seawater were important; concentrations of approximately 7 mg L⁻¹ for Mn and 60 mg L⁻¹ for Zn were observed under our experimental conditions. We also examined the rate of release of these metals from the sediment into the seawater in the presence of the different acids and under different experimental conditions. We found that most of the metallic elements were released from the sediments into the seawater during the first fifteen minutes of exposure. After this time, a high degree of pollution was induced if acids leached into seawater were not rapidly diluted.  相似文献   

Lithofacies,depositional environments,regional biostratigraphy and age of the Chitarwata Formation in the Bugti Hills,Balochistan, Pakistan     

Grégoire Métais  Pierre-Olivier Antoine  S.R. Hassan Baqri  Jean-Yves Crochet  Dario De Franceschi  Laurent Marivaux  Jean-Loup Welcomme 《Journal of Asian Earth Sciences》2009,34(2):154-167

The Oligocene-early Miocene Chitarwata Formation records a critical interval of terrestrial sedimentation that predates the Siwalik deposits on the Potwar Plateau of north-central Pakistan. This Oligocene-early Miocene time interval has long been considered as lacking in the entire Indo-Pakistan region. The Chitarwata Formation is widely exposed in the Sulaiman Range, but has never been described in detail in the Sulaiman Lobe, where the famous fossiliferous strata called ‘Bugti Bone Beds’ have been known for over a century and half. The Chitarwata Formation represents coastal-delta at the base, and plain and fluvial environments at the top. Lithofacies and sedimentary structures of the Chitarwata Formation in the Bugti area are described in detail, and show a clearly distinct lithologic pattern, different from that reported from the Zinda Pir area. The Chitarwata Formation also records an important transition in the evolution of the drainage systems in the area during the late Paleogene and early Neogene. This transition from the west-flowing paleo-Indus fluvial system to the development of the ancestral Indus drainage system may explain the numerous hiatuses that characterize the Chitarwata Formation. The abundance of fossil mammals from the Chitarwata and overlying Vihowa formation in the Bugti Hills provides critical biochronologic information that sheds new light on biostratigraphic correlation with the Zinda Pir area and for the entire Sulaiman Range.  相似文献   

Contemporaneous multi-scale structures in the Montagne des Mémises (Préalpes du Chablais, Haute-Savoie, France)     

Anne Guyomard  Jean-Yves Josnin  Jean-Claude Hippolyte  Serge Fudral 《Swiss Journal of Geoscience》2009,102(1):3-14

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Volcanisme de l'ı̂le aux Pingouins,archipel Crozet,témoin de l'hétérogénéité du manteau fertile au sud de l'océan IndienPenguins Island,Crozet archipelago,volcanic evidence for a heterogeneous mantle in the southern Indian Ocean     

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. KAr 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