Daily variability of river concentrations and fluxes: indicators based on the segmentation of the rating curve     

Michel Meybeck  Florentina Moatar 《水文研究》2012,26(8):1188-1207

The variability of water chemistry on a daily scale is rarely addressed due to the lack of records. Appropriate tools, such as typologies and dimensionless indicators, which permit comparisons between stations and between river materials, are missing. Such tools are developed here for daily concentrations (C), specific fluxes or yields (Y) and specific river flow (q). The data set includes 128 long‐term daily records, for suspended particulate matter (SPM), total dissolved solids (TDS), dissolved and total nutrients, totalling 1236 years of records. These 86 river basins (10³–10⁶ km²) cover a wide range of environmental conditions in semi‐arid and temperate regions. The segmentation—truncation of C–q rating curves into two parts at median flows (q₅₀) generates two exponents (b_50inf and b_50sup) that are different for 66% of the analysed rating curves. After segmentation, the analysis of records results in the definition of nine major C–q types combining concentrating, diluting or stable patterns, showing inflexions, chevron and U shapes. SPM and TDS are preferentially distributed among a few types, while dissolved and total nutrients are more widely distributed. Four dimensionless indicators of daily variability combine median (C₅₀, Y₅₀), extreme (C₉₉, Y₉₉) and flow‐weighted (C*, Y*) concentrations and yields (e.g. C₉₉/C₅₀, Y*/Y₅₀). They vary over two to four orders of magnitude in the analysed records, discriminating stations and river material. A second set of four indicators of relative variability [e.g. (Y*/Y₅₀)/(q*/q₅₀)], takes into account the daily flow variability, as expressed by q*/q₅₀ and q₉₉/q₅₀, which also vary over multiple orders of magnitude. The truncated exponent b_50sup is used to describe fluxes at higher flows accounting for 75% (TDS) to 97% (SPM) of interannual fluxes. It ranges from ? 0·61 to + 1·86 in the database. It can be regarded as the key amplificator (positive b_50sup) or reductor (negative b_50sup) of concentrations or yields variability. C₅₀, Y₅₀, b_50sup can also be estimated in discrete surveys, which provides a new perspective for quantifying and mapping water quality variability at daily scale. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Bayesian statistics of non-linear inverse problems: example of the magnetotelluric 1-D inverse problem   总被引：1，自引：0，他引：1  

Pascal Tarits  Virginie Jouanne  Michel Menvielle  Michel Roussignol 《Geophysical Journal International》1994,119(2):353-368

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Test of the vibrational modelling for the λ-type transitions: Application to the α-β quartz transition     

Joëlle Castex  Michel Madon 《Physics and Chemistry of Minerals》1995,22(1):1-10

Vibrational modelling is at the present time the only known way to predict the heat capacities of the Earth's mantle minerals at high-pressure and high-temperature. To test the validity of this method for λ-type transitions, we have applied it to the α-β quartz transition (T ₀=846±1 K). Raman spectra of quartz were recorded up to 900 K. Measured frequency shifts of the α-quartz Raman modes were then used in conjunction with available high-pressure Raman data to calculate intrinsic mode anharmonicity, through the parameter a _i=(?Lnv_i/?T)_v. Vibrational modelling of the heat capacity at constant volume, Cv, and at constant pressure, Cp, including anharmonic corrections deduced from the a _i parameters, are compared to experimental data. Taking into account the soft-mode associated to the α-β quartz transition, the model reproduces the excess of Cp related to the transition. Then, this study confirms that detecting a soft-mode from vibrational data allows one to predict λ-type transitions. However, when modelling the thermodynamic properties, the contribution of a soft-mode cannot be established from spectroscopic data. Therefore, one needs first to determine this contribution in order to predict the heat capacities of Earth's mantle minerals displaying λ-type transitions. In α-quartz, this contribution has been determined as 0.007% of the total number of the optic modes in the model of the density of states.  相似文献   

Geothermobarometry in albite-garnet orthogneisses: A case study from the Gran Paradiso nappe (Western Alps)     

Elisabeth Le Goff  Michel Ballvre 《Lithos》1990,25(4):261-280

The aim of this paper is to estimate syntectonic P-T conditions within albite- and garnet-bearing orthogneisses. These rocks are generally characterized by the assemblage quartz + albite + biotite + phengite + CaFe-garnet + epidote + titanite. Garnet contains up to 55 mole per cent of grossular. K-feldspar is a relict magmatic phase.

P-T conditions are estimated using several independent methods. First, it is shown that exchange reactions based on the Fe---Mg partitioning between garnet and biotite or garnet and phengite cannot be used to estimate temperatures in these rocks, due to the high grossular content of garnet. Second, maximum and minimum pressures are constrained, respectively, by the occurrence of albite instead of jadeite + quartz and by the assemblage phengite + biotite + quartz. Third, phase equilibria in albite- and garnet-bearing metagranites are modelled in the system K₂O---CaO---FeO---Al₂O₃---SiO₂---H₂O. Equilibrium curves are calculated for the observed phase compositions. Uncertainties in P-T estimates mainly result from the choice of appropriate non-ideal solution models for the garnet.

An application is developed for granites from the Gran Paradiso nappe (Western Alps). These granites show an heterogeneous deformation of Alpine age expressed by mylonitic shear zones cutting across weakly deformed domains. Estimated P-T conditions for the synkinematic assemblages are 10–16 kbar at 550±50°C.  相似文献   

Phase transformations and inherited lattice preferred orientations: implications for seismic properties     

David Mainprice  Michel Humbert  Francis Wagner 《Tectonophysics》1990,180(2-4):213-228

In phase transitions via either the martensitic (diffusionless shear) or nucleation and growth mechanism a specific orientation relationship may exist between the two phases. In cases where the orientation relationship is known, the lattice preferred orientation (LPO) inherited by the new phase may be calculated from the LPO of the old phase. The method of calculation is presented in a form suitable for the spherical harmonic method of texture analysis using the orientation distribution function (ODF). Examples are presented for the -β-quartz, calcite-aragonite, orthopyroxene-clinopyroxene and olivine-spinel transformations.

The seismic properties of the transformed and untransformed phases are calculated from the ODF and the single crystal elastic constants. In particular the -β quartz transformation is considered in detail. The quartz polycrystal is very anisotropic in the alpha field (V_p anisotropy coefficient, A = 8.1%) and almost isotropic in the β-field (A = 2.1%). The transition is accompanied by V_p velocity increase of 0.6 km/s. In the other example discussed, olivine-β-spinel, there is also a decrease in V_p anisotropy coefficient from 11.1% (olivine) to 4.0% (β-spinel). The estimate of the volume fraction of olivine at the 400 km discontinuity (associated with this phase transition) is shown to depend on the direction of wave propagation.  相似文献   

Calculated mineral equilibria in the greenschist-blueschist-eclogite facies in Na2O−FeO−MgO−Al2O3−SiO2−H2O     

Michel Guiraud  Tim Holland  Roger Powell 《Contributions to Mineralogy and Petrology》1990,104(1):85-98

The new, greatly expanded internally-consistent dataset of Holland and Powell includes thermodynamic data for a wide range of mineral end-members in common rock-forming minerals, in particular, including FeMg_-1 substitutions in glaucophane, garnet, chloritoid and carpholite, and FeMg_-1 and MgSiAl_-1Al_-1 substitutions in talc and chlorite. Moreover, we have the uncertainties and correlations for these data. With the data, we have calculated the full pressure-temperature phase diagram for the system Na₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O (NFMASH) for quartz (or coesite) and H₂O in excess, in the range 300°–800°C and 5–50 kbars. By solving the set of non-linear equations formed by the equilibrium relationships for an independent set of equations between the end-members in an assemblage in NFMASH, the compositions of the minerals (and PT) can be calculated. Thus the changes in MgSiAl_-1Al_-1 along NMASH reactions, and FeSiAl_-1Al_-1 along NFASH reactions, are calculated, and the changes in FeMg_-1 and MgSiAl_-1Al_-1 along NFMASH reactions are calculated. From this information it is straightforward to generate PT diagrams for specific rock compositions. Mineral assemblages and mineral compositional changes in the phase diagram are discussed in relation to greenschist, blueschist and eclogite facies assemblages in metapelitic rocks. It is found that the correspondence between the predictions of the phase diagrams and the observations on rocks is remarkably good. When semiquantitative extensions of the phase diagram to include Ca(MgFe)_-1, NaSiCa_-1Al_-1, Fe³⁺Al_-1 and KNa_-1 substitutions are taken into account the agreement is essentially complete.  相似文献   

Ground variation of radon 222 for location of hidden structural features. Example of the south of France (Alpes Maritimes)     

Serge Borchiellini  Michel Bernat  Robert Campredon 《Pure and Applied Geophysics》1991,135(4):625-638

We report two examples from the south of the French Alps, showing that radon emanation monitored by alpha-sensitive film may be used to locate certain discrete structural features revealed in data collected by remote sensing from a satellite. The variations observed in our data, over a period of several months, are in accordance with atmospheric changes and might correlate with local seismic activity when the detectors are located directly above structural fractures and the magnitude of the seismic event is greater than 2.  相似文献   

Plio-Quaternary geodynamic evolution of a segment of the Peruvian Andean Cordillera located above the change in the subduction geometry: the Cuzco region     

Justo Cabrera  Michel S  brier  Jacques Louis Mercier 《Tectonophysics》1991,190(2-4):331-362

The Cuzco region, which is located above a change in subduction geometry, appears to be characterized by a variable Plio-Quaternary tectono-sedimentary evolution essentially located along the major fault system that separates the High Plateaux from the Eastern Cordillera. After the higher surface formation of the High Plateaux, a set of Neogene basins were filled by Miocene “ fluvio-torrential” series and by Plio-Pleistocene fluvio-lacustrine deposits. The Neogene series have been affected by compressional tectonic forces attributed to the Late Miocene. This compression is followed by roughly E-W trending syn-sedimentary extensional tectonics attributed to the Pliocene; it is related to reactivation of the pre-existing major faults, basin evolution, and volcanic activity concentrated along the faults. In the Early Pleistocene, fluvio-lacustrine deposits are affected by syn- and post-sedimentary compressional tectonism it is characterized by shortening that trends both N-S and E-W and produces folding and faulting of the sedimentary cover. Extensional tectonism trending roughly N-S has been taking place from the Middle Pleistocene to the Present; it is coeval with shoshonitic volcanic activity, and with sedimentation of fluvio-lacustrine terraces, torrential fans and moraines. Quaternary and active normal faults due to this tectonism, are located in a narrow zone more than 100 km-long between the High Plateaux and the Eastern Cordillera, and two 15 km-long fault sectors in the Eastern Cordillera. Characteristic Pleistocene scarps, 400 m or more high, are due to the cumulative normal offset, and there are also little scarps, with heights ranging between 2 and 20 m, which are related to Holocene fault reactivations. Recent fault reactivation on the Cuzco fault system, during the April 5, 1986 earthquake (m_b = 5.3), is due to the N-S trending extension. This state of stress, located at a mean elevation of roughly 3730 m, is generally homogeneous to different scales. The active Cuzco normal faults may be a consequence of adjustment between the compensated Western Cordillera and the undercompensated Eastern Cordillera, this latter being uplifted higher than its isostatic equilibrium due to compression acting on its eastern edge. The variation of the state of stress, during the Plio-Quaternary is in agreement with the variations of the compressional boundary forces. It may be explained by variation of the convergence rate or by the variation of pull-slab forces.  相似文献   

Convection in a North Sea oil reservoir: inferences on diagenesis and hydrocarbon migration     

Michel Rabinowicz  Jean-Louis Dandurand  Marc Jakubowski  Jacques Schott  Jean-Pierre Cassan 《Earth and Planetary Science Letters》1985,74(4):387-404

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Microtectonic evidence for eastward ductile shear in the Jurassic orogen of SW Japan     

Michel Faure 《Journal of Structural Geology》1985,7(2):175-186

Two Jurassic deformation phases are responsible for the thrust and nappe structures in the infrastructure of the outer belt of the Mesozoic chain of SW Japan. The first phase was synmetamorphic, and took place under HP/LT conditions. Microtectonic analysis shows that the penetrative deformation corresponded to a ductile shear directed from W to E, parallel to the stretching and mineral lineation. At the regional scale the first phase corresponded to the obduction of the Greenschist nappes upon the Kurosegawa continent. During the second phase the Greenschist nappes were sliced, leading to an apparent reverse metamorphic zoning. The first phase structures were then locally reworked by folds giving rise to an apparent westwards sense of shear.  相似文献