Superimposed tectonic and hydrothermal events during the late-orogenic extension in the Western French Massif Central: a structural and ⁴⁰Ar/³⁹Ar study     

Jean-Yves Roig  Michel Faure  & Henri Maluski 《地学学报》2002,14(1):25-32

In the Western French Massif Central, the Argentat fault is a major structure through which As–Au fluids percolated in the Late Carboniferous along brittle fractures. New petrostructural investigations show that an early ductile normal-dextral faulting, coeval to leucogranite emplacement took place during the Late Visean syncollisional extension of the belt and was accompanied by a hydrothermal event marked by the growth of muscovites whose ⁴⁰Ar/³⁹Ar ages cluster around 335 Ma. This early fluid channelling is associated with brittle deformation only in the hangingwall of the Argentat fault, whereas ductile deformation is restricted to the footwall. These results provide new evidence for the upper crust implication during the syncollisional extension in the French Massif Central. This study stresses the interest of a detailed multimethod analysis to characterize hydrothermal processes, especially in basement areas where the tectonic, plutonic and metamorphic evolution is polyphased.  相似文献   

A detailed study of the Gagua Ridge: A fracture zone uplifted during a plate reorganisation in the Mid-Eocene   总被引：2，自引：0，他引：2  

Deschamps  Anne E.  Lallemand  Serge E.  Collot  Jean-Yves 《Marine Geophysical Researches》1998,20(5):403-423

Recent multibeam bathymetric and geophysical data recorded in the West Philippine Basin, east of Taiwan, reveal new information on the structure and the tectonic origin of the oceanic Gagua Ridge. This linear, 300 km-long, 4 km-high, north-south-trending ridge, is being subducted beneath the Ryukyu Trench along 123° E. This basement high separates two basins of different ages. Its summit is marked by two crests and an axial valley. A map of the basement top shows the region of the ridge to be composed of a set of linear and parallel ridges and troughs. All these elements suggest that the development of the ridge, and its surroundings, has been influenced by strike-slip deformation. Nevertheless, the height of the ridge indicates also an important compressive component in the deformation. Gravity models across the ridge show local compensation with a crustal root, indicating that an overthickening of the crust occurred when it was young and thus more easily deformable. This idea is strengthened with flexural modeling of the lithosphere that bends under the load of the ridge, indeed it indicates that the high probably formed when the underlying lithosphere was young. We interpret the Gagua Ridge as a fracture zone transverse ridge uplifted during a transpressive episode along a north-south -trending fracture zone in the middle Eocene time, if we accept Hilde and Lee's (1984) model of magnetic lineations. This tectonic event could be contemporaneous with a change of the pole of rotation of the West Philippine Basin which occurred about 43/45 Ma ago.  相似文献   

The influence of paleoclimatic events on the functioning of an alpine thermal system (France): the contribution of hydrodynamic–thermal modeling     

Stéphanie Gallino  Jean-Yves Josnin  Marc Dzikowski  Fabien Cornaton  Dominique Gasquet 《Hydrogeology Journal》2009,17(8):1887-1900

Numerical models of the Aix-les-Bains thermal aquifer (France) were used to investigate the influence of Quaternary paleoclimatic events on the current thermal state of the groundwater. Initial numerical tests were successful in that present-day fluid flows (heads and flow rates) and the resulting velocities were compatible with residence time data. Water flowing through an aquifer cools the rock mass; therefore, the rate of water flow governs the outlets temperature. For the Aix-les-Bains aquifer, applying present-day flow rates to the entire history of the aquifer leads to much more substantial cooling of the rock mass than is indicated by the outlets temperature (i.e. present-day flow rates are 10 times too high). This suggests that the aquifer may have gone through alternating functioning phases, during which the rock mass cooled, and blocked phases, during which the aquifer reheated. Other results indicate that the main parameters affecting thermal behavior during a functioning phase are the total inflow volume, rather than individual inflow rates, and the initial heat field. As phenomena linked to glaciation can lead to the blocking of infiltration zones and aquifer outlets, the findings suggest that the hypothesis of intermittent aquifer functioning related to glaciations is compatible with the current thermal field.  相似文献   

Bimodal distribution of the solid products in a magmatic chamber: Modelling by fractional crystallization and coupling of the chemical exchanges with the differential melt/solid transport     

Morad Lakhssassi  Bernard Guy  Eric Touboul  Jean-Yves Cottin 《Comptes Rendus Geoscience》2010,342(9):701-709

Our aim is to explain the possible bimodality of the compositions of the magmatic rocks of the same province. In order to do so, we present a model for the crystallization of a magmatic chamber, coupling the three phenomena: solidification, sedimentation, chemical reactions between the solid and the liquid. These three phenomena make two independent dimensionless parameters appear: the ratios of the solidification rate to the transport velocity, and of the chemical kinetics to the transport velocity. The model is written for one independent chemical component. It is shown that, for certain values of the dimensionless parameters, the chemical composition of the chamber can present a bimodal distribution, starting from uniform initial conditions. This model shows that the coupling between three elementary phenomena is enough to explain the bimodality, or more generally the appearance of discontinuities of chemical compositions, without making any additional assumption.  相似文献   

Late Cenozoic geodynamic evolution of eastern Indonesia   总被引：2，自引：0，他引：2  

Florent Hinschberger  Jacques-Andr Malod  Jean-Pierre Rhault  Michel Villeneuve  Jean-Yves Royer  Safri Burhanuddin 《Tectonophysics》2005,404(1-2):91-118

This paper presents an internally and globally consistent model of plate evolution in eastern Indonesia from Middle Miocene to Present time. It is centered on the Banda Sea region located in the triple junction area between the Pacific–Philippine, Australia and South–East Asia plates. The geological and geophysical data available from Indonesia were until recently insufficient to define a unique plate tectonic model. In this paper, the new data taken into account clearly restrict the possible interpretations. Owing to a great number of geological, geophysical and geochemical studies, the major plate boundaries (the Sunda–Banda subduction zone to the south, the Tarera–Aiduna Fault zone and the Seram Thrust to the east, and the Sorong Fault zone and Molucca Sea collision zone to the north) are now clearly identified. The age of the major tectonic structures is also better known. Geodetic measurements well constrain the Present time plate kinematics. We also consider the deformation history within eastern Indonesia, where numerous short-lived microplates and their related microcontinents successively accreted to the Asiatic margin. Moreover, magnetic anomalies identification of the North and South Banda Sea basins allows a precise kinematic reconstruction of the back-arc opening. We used the Plates software to test the coherency of our model, presented as a series of 4 plate reconstruction maps from 13 Ma to the present. Finally, the origin of oceanic domains restored by our reconstruction is discussed.  相似文献   

Evolution of particle size and concentration in the Rhône river mixing zone: : influence of salt flocculation     

Antoine Thill  Stphane Moustier  Jean-Marie Garnier  Claude Estournel  Jean-Jacques Naudin  Jean-Yves Bottero 《Continental Shelf Research》2001,21(18-19)

The salt induced flocculation phenomenon is often proposed as a major mechanism influencing the deposition of the suspended matter near the mouth of major rivers. However, depending on the particular mixing conditions between fresh water and marine water and on suspended solids (SS) reactivity, salt induced aggregation may be a minor factor controlling fast deposition of SS. This work combines field studies and laboratory experiments in order to assess the importance of salt induced flocculation in the case of the saltwedge estuary of the Rhône river. Sampling of the mixing zone has been performed in contrasted hydrodynamic conditions from a low water discharge period (500 m³ s⁻¹) to a small flood event (2400 m³ s⁻¹) for particle counting and salinity measurements. Through laboratory experiments, it is shown that the Rhône river particulate matter has a poor average reactivity regarding salt induced flocculation. Considering the hydrodynamics of the estuary, we show that the evolution of the concentration of larger particles (>5 μm) can be explained by settling and dilution. In contrast, the smallest measured fraction (2–5 μm) shows a more complex behavior and settling processes alone cannot explain the observed particle concentrations during the field studies. Four hypotheses are discussed for explaining the 2–5 μm particle concentration evolutions.  相似文献   

Metropolitan government in Toulouse: From fragmentation to federalism     

Jean-Yves Nevers 《GeoJournal》2002,58(1):33-41

This paper examines changes in governance in the metropolitan area of Toulouse, which includes 78 communes and contains a population of 761,000. As in most French cities local government is very fragmented. Until the end of the 1980s, the urban services were delivered by many associations of communes, both single-purpose and multipurpose. This pragmatic form of governance made it possible for the communes to preserve their identity and their decision-making autonomy, which is the basis of the French traditional model of local democracy. But it is rather important to face the new challenges posed by inter-city competition across Europe, by continuing urban growth, and by the reinforcement of residential segregation. The recent creation of `Grand Toulouse', a metropolitan two-tier government with many competences and a taxing power appears to bring an institutional solution, but one can wonder if local leaders will try to make it simply another co-ordinating mechanism. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

From strike-slip faulting to oblique subduction: A survey of the Alpine Fault-Puysegur Trench transition,New Zealand,results of cruise Geodynz-sud leg 2     

Jean Delteil  Jean-Yves Collot  Ray Wood  Richard Herzer  Stéphane Calmant  David Christoffel  Mike Coffin  Jacky Ferrière  Geoffroy Lamarche  Jean-Frédéric Lebrun  Alain Mauffret  Bernard Pontoise  Michel Popoff  Etienne Ruellan  Marc Sosson  Ruppert Sutherland 《Marine Geophysical Researches》1996,18(2-4):383-399

The Geodynz-sud cruise on board the R/V l'Atalante collected bathymetric, side-scan sonar and seismic reflection data along the obliquely convergent boundary between the Australian and Pacific plates southwest of the South Island, New Zealand. The survey area extended from 44°05 S to 49°40 S, covering the transition zone between the offshore extension of the Alpine Fault and the Puysegur Trench and Puysegur Ridge. Based on variations in the nature and structure of the crust on either side of the margin, the plate boundary zone can be divided into three domains with distinctive structural and sedimentary characteristics. The northern domain involves subduction of probably thinned continental crust of the southern Challenger Plateau beneath the continental crust of Fiordland. It is characterized by thick sediments on the downgoing slab and a steep continental slope disrupted by fault scarps and canyons. The middle domain marks the transition between subduction of likely continental and oceanic crust defined by a series of en echelon ridges on the downgoing slab. This domain is characterized by a large collapse terrace on the continental slope which appears to be due to the collision of the en echelon ridges with the plate margin. The southern domain involves subduction of oceanic crust beneath continental and oceanic crust. This domain is characterized by exposed fabric of seafloor spreading on the downgoing slab, a steep inner trench wall and linear ridges and valleys on the Puysegur ridge crest. The data collected on this cruise provide insights into the nature and history of both plates, and factors influencing the distribution of strike-slip and compressive strain and the evolution of subduction processes along a highly oblique convergent margin.  相似文献   

Formation de gradients thermiques a la surface de l'ocean, au-dessus d'un talus, par interaction entre les ondes internes et le melange du au vent     

Maze  Robert; Camus  Yves; le Tareau  Jean-Yves 《ICES Journal of Marine Science》1986,42(3):221-240

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AMS study of the Pont-de-Montvert–Borne porphyritic granite pluton (French Massif Central) and its tectonic implications     

Jean-Yves Talbot  Yan Chen  Michel Faure  & Wei Lin 《Geophysical Journal International》2000,140(3):677-686

Thermomagnetic experiments, isothermal remanent magnetization (IRM), hysteresis loops, X-ray reflection analyses, optic microscopic observations, bulk magnetic susceptibility and natural remanent magnetization (NRM) show that the susceptibility signal of 56 sites in the Pont-de-Montvert–Borne pluton is derived mostly from biotite with a very small proportion of ferromagnetic material. Low anisotropy degree ( P parameter) and consistent AMS orientations among monzonite, enclaves and aplitic dykes indicate that the AMS was acquired during pluton emplacement in the subsolidus phase. Magnetic fabrics demonstrate that linear deformation is prominent in the area where the granite is in direct contact with micaschists, and that planar deformation becomes more important in the area where the pluton is surrounded by non-porphyritic peraluminous granites. AMS measurements also show that shallow plunging E–W-stretching lineations are the dominant structure over most of the studied area. Foliation orientations follow the pluton contour in the western part, indicating that the Pont-de-Montvert–Borne pluton is probably rooted in the west and extruded towards the east. These AMS results agree to some extent with fabric inferred from mineral preferred orientation. The AMS data support an E–W extensional tectonic setting during the Pont-de-Montvert–Borne pluton emplacement, which resulted from the Late Carboniferous crustal thinning of the Hercynian orogeny.  相似文献