Characterising groundwater and surface-water interconnections using hydrogeology,hydrochemistry and stable isotopes in the Ouémé Delta,southern Benin     

Guidah Chabi  Bio  Alassane  Abdoukarim  Kpegli  Kodjo Apelete Raoul  Lawson  Fabrice Messan Amene  Alassane Zakari  Aoulatou  Koukpohounsi  Bénito Didier  Boukari  Ousmane Touré  Vouillamoz  Jean-Michel  Yalo  Nicaise  Mama  Daouda  Boukari  Moussa 《Hydrogeology Journal》2023,31(5):1229-1243

The Mio-Pliocene aquifer of the coastal sedimentary basin of Benin is the most exploited aquifer for water supply to the urbanised region in the southern part of the country. The population explosion is putting increasing pressure on quantitative and qualitative aspects of the groundwater resources. Preventing groundwater contamination caused by surface waters requires a thorough understanding of surface-water/groundwater interactions, especially the interactions between the Mio-Pliocene aquifer and surface waters. This study aimed to investigate the interactions between groundwater and surface waters along the major rivers (Sô River and Ouémé Stream) and brooks in the Ouémé Delta. Field campaigns identified 75 springs located in the valleys which feed the rivers, and thus maintain their base flow. The piezometric results indicated, through flow direction assessment, that the Mio-Pliocene aquifer feeds Ouémé Stream and Sô River. Chemical analyses of groundwater and surface waters show similar chemical facies, and changes in the chemical composition in groundwater are also observed in the surface waters. Moreover, the isotopic signatures of surface waters are similar to those of the groundwater and springs, which led to the identification of potential groundwater discharge areas. As a result of groundwater discharge into surface waters, the fraction of groundwater in the surface water is more than 66% in the brooks, regardless of the season. In the Ouémé Stream and Sô River, the fraction of groundwater is 0–21% between June and September, while from October to March it is 47–100%.

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On the Impact of the Assimilation of SARAL/AltiKa Wave Data in the Operational Wave Model MFWAM     

Lotfi Aouf  Jean-Michel Lefèvre 《Marine Geodesy》2015,38(3):381-395

As a part of our calibration/validation activities five months of SARAL/AltiKa wave data have been analyzed in this study. A robust quality control procedure using threshold values on signal and retrieved wave heights was implemented before the assimilation. Assimilation runs in the wave model Météo-France (MFWAM) were performed for a long period. The validation of the model outputs was performed with independent wave observations from altimeter and buoy data. The results indicate good performance in terms of bias and scatter index for the significant wave height and the peak wave period. Statistical analyses were performed for different ocean basins (high and intermediate latitudes and tropics). The use of SARAL/AltiKa and Jason-2 wave data combined was also investigated. This leads to further improvements for the analysis and forecast periods. In other respects, the impact of the assimilation of SARAL/AltiKa wave data is discussed for waves under strong wind conditions such as typhoons Fitow and Danas which occurred in early October 2013.  相似文献   

Mesoscale raised rim depressions (MRRDs) on Earth: A review of the characteristics,processes, and spatial distributions of analogs for Mars     

Devon M. Burr  Barbara C. Bruno  Peter D. Lanagan  Lori S. Glaze  Windy L. Jaeger  Richard J. Soare  Jean-Michel Wan Bun Tseung  James A. Skinner  Stephen M. Baloga 《Planetary and Space Science》2009,57(5-6):579-596

Fields of mesoscale raised rim depressions (MRRDs) of various origins are found on Earth and Mars. Examples include rootless cones, mud volcanoes, collapsed pingos, rimmed kettle holes, and basaltic ring structures. Correct identification of MRRDs on Mars is valuable because different MRRD types have different geologic and/or climatic implications and are often associated with volcanism and/or water, which may provide locales for biotic or prebiotic activity. In order to facilitate correct identification of fields of MRRDs on Mars and their implications, this work provides a review of common terrestrial MRRD types that occur in fields. In this review, MRRDs by formation mechanism, including hydrovolcanic (phreatomagmatic cones, basaltic ring structures), sedimentological (mud volcanoes), and ice-related (pingos, volatile ice-block forms) mechanisms. For each broad mechanism, we present a comparative synopsis of (i) morphology and observations, (ii) physical formation processes, and (iii) published hypothesized locations on Mars. Because the morphology for MRRDs may be ambiguous, an additional tool is provided for distinguishing fields of MRRDs by origin on Mars, namely, spatial distribution analyses for MRRDs within fields on Earth. We find that MRRDs have both distinguishing and similar characteristics, and observation that applies both to their mesoscale morphology and to their spatial distribution statistics. Thus, this review provides tools for distinguishing between various MRRDs, while highlighting the utility of the multiple working hypotheses approach.  相似文献   

40Ar–39Ar geochronology across Archean and Paleoproterozoic terranes from southeastern Guiana Shield (north of Amazonian Craton,Brazil): Evidence for contrasting cooling histories     

Lúcia Travassos da Rosa-Costa  Patrick Monié  Jean-Michel Lafon  Nicolas O. Arnaud 《Journal of South American Earth Sciences》2009,27(2-3):113-128

A ⁴⁰Ar/³⁹Ar geochronological study was performed on amphibole and biotite from some representative units of distinct tectonic domains of the southeastern Guiana Shield, north of the Amazonian Craton, the Amapá Block and the Carecuru Domain. In the Amapá Block, an Archean continental block involved in the Transamazonian orogenesis (2.26–1.95 Ga), the investigated minerals, from rocks of the Archean high-grade basement assemblage, give only Paleoproterozoic ages, indicating their complete resetting during the Transamazonian orogenic event. Amphibole ages vary from 2087 ± 3 to 2047 ± 20 Ma, and biotite ages spread mainly between 2079 ± 18 and 2033 ± 13 Ma. In the Carecuru Domain, in which the geodynamic evolution is related to Paleoproterozoic magmatic arc setting during the Transamazonian event, calc-alkaline granitoids yield amphibole age of 2074 ± 17 Ma, and biotite ages of 1928 ± 19 Ma and 1833 ± 13 Ma.These data reinforce the importance of the Transamazonian orogenic cycle in the investigated area, and indicate that the rocks were not significantly affected by post-Transamazonian events. When coupled with available U–Th–Pb monazite and Pb–Pb zircon geochronological records and petro-structural observations, the new ⁴⁰Ar/³⁹Ar data delineate contrasting cooling and exhumation histories for the tectonic domains. In the Amapá Block, the data suggest nearly vertical T–t paths that reflect fast cooling rates, which indicate tectonically controlled exhumation, related to collisional stages of the Transamazonian event, between 2.10 and 2.08 Ga. Conversely, in the Carecuru Domain, low cooling rates suggest that the arc-related granitoids underwent slow and monotonous cooling since their emplacement until reaching the biotite isotopic closure temperature.  相似文献   

Origine mantélique des benmoreites de Moorea (Iles de la Societé, Pacifique)     

F. Blanchard  J. M. Liotard  R. Brousse 《Bulletin of Volcanology》1981,44(4):691-710

Lavas from Moorea form two groups of about the same volumetric importance: a basalt hawaiite group and a mugearite benmoreite trachyte group. Although more differentiated, the rocks of the second group cannot be related to the first by simple fractional crystallization. A model of fractional fusion or the same mantle source may explain the relationship between the two groups. The primary magmas generated by fractional fusion were subsequently modified by low pressure fractionation.  相似文献   

Partitioning of transition elements between clinopyroxene and garnet     

C. Dupuy  J. Dostal  J.M. Liotard  A. Leyreloup 《Earth and Planetary Science Letters》1980,48(2):303-310

Abundances of transition elements (Ti, V, Cr, Mn, Fe²⁺, Co, Ni, Cu and Zn) in coexisting clinopyroxene and garnet are used to estimate clinopyroxene/garnet partition coefficients for these elements. The analyzed samples include eclogites, granulites and peridotites. The partition coefficients are sensitive to the major element composition of the mineral phases, although for individual transition elements they correlate with different chemical parameters. The partition coefficients of Ti correlate with the (FeO/MgO)_garnet/(FeO/MgO)_{clinopyroxene} ratio thus suggesting that the partitioning of Ti is a sensitive indicator of the physical (temperature-pressure) conditions of equilibration.  相似文献   

Magnetic resonance sounding applied to aquifer characterization   总被引：3，自引：0，他引：3  

Legchenko A  Baltassat JM  Bobachev A  Martin C  Robain H  Vouillamoz JM 《Ground water》2004,42(3):363-373

Magnetic resonance sounding (MRS) is distinguished from other geophysical tools used for ground water investigation by the fact that it measures a magnetic resonance signal generated directly from subsurface water molecules. An alternating current pulse energizes a wire loop on the ground surface and the MRS signal is generated; subsurface water is indicated, with a high degree of reliability, by nonzero amplitude readings. Measurements with varied pulse magnitudes then reveal the depth and thickness of water saturated layers. The hydraulic conductivity of aquifers can also be estimated using boreholes for calibration. MRS can be used for both predicting the yield of water supply wells and for interpolation between boreholes, thereby reducing the number of holes required for hydrogeological modeling. An example of the practical application of MRS combined with two-dimensional electrical imaging, in the Kerbernez and Kerien catchments area of France, demonstrates the efficiency of the technique.  相似文献   

Trace element evidence for the origin of ocean island basalts: an example from the Austral Islands (French Polynesia)     

C. Dupuy  H. G. Barsczus  J. M. Liotard  J. Dostal 《Contributions to Mineralogy and Petrology》1988,98(3):293-302

The Austral Islands, a volcanic chain in the South-Central Pacific Ocean (French Polynesia) are composed mainly of alkali basalts and basanites with subordinate amounts of olivine tholeiites and strongly undersaturated rocks (phonolite foidites and phonolite tephrites). The basaltic rocks have geochemical features typical of oceanic island suites. The distribution of incompatible trace elements indicate that the lavas were derived from a heterogeneous mantle source. The chondrite-normalized patterns of the incompatible elements in basaltic rocks of the Austral Islands are complementary to those of island arc tholeiites. As supported by isotope data, the observed trace element heterogeneities of the source are probably due to mixing of the upper mantle with subducted oceanic crust from which island arc tholeiitic magma was previously extracted.  相似文献   

The transition between blueschists and lawsonite-bearing eclogites based on observations from Corsican metabasalts   总被引：2，自引：0，他引：2  

Jean-Michel Caron  Guy Pquignot 《Lithos》1986,19(3-4):205-218

Syntectonic eclogites, associated with blueschist parageneses, have recrystallized in metabasalts from eastern Corsica under very low temperatures (420°C). The evolution of these eclogites is recorded by the order of development of metamorphic minerals, as demonstrated by helicitic inclusions of lawsonite and actinolite in Fe-rich garnets, and the occurrence of fibrous Na-pyroxenes in the pressure shadows and cracks of boudinaged garnets, within a foliated matrix composed of glaucophane, Ca---Fe garnets and lawsonite.

A Schreinemakers analysis has been completed on the lawsonite-ferroglaucophane-actinolite-almandine-grossular-ferro-omphacite-chlorite system in a (T,P,μ_H2O)-space. The resulting three-dimensional relationships are applied to the studied samples. They are consistent with a prograde increase in temperature at low μ_H2O, producing eclogites from blueschists, and with a subsequent retrogressive decrease in pressure.  相似文献   

Petrology and U/Pb geochronology of the Telohat migmatites,Aleksod, Central Hoggar,Algeria   总被引：6，自引：0，他引：6  

Pierre Barbey  Jean-Michel Bertrand  Serge Angoua  Danielle Dautel 《Contributions to Mineralogy and Petrology》1989,101(2):207-219

The Aleksod region is composed of metasedimentary rocks and large areas of biotite and hornblende-bearing migmatites. Anatexis associated with the main deformation stages, occurred under high pressure and temperature conditions estimated at 13±2 Kbar and 750±50° C. The bulk mineralogical composition of the Telohat migmatites shows that their protolith was granodioritic. Internal structures of zircons and U-Pb data suggest a polyphased evolution, with a 2131±12 Ma age for the protolith and a 609±17 Ma age for the Pan-African tectono-metamorphic evolution, thus precluding any Kibaran event in the Aleksod area. Leucosomes are richer in Sr and display lower Rb, Zr, Nb, Y, Th, U and REE contents than melanosomes wherein accessory phases are stored. Eu contents are also lower in the leucosomes but in lesser proportion than the other rare earth's, leading to a significant positive anomaly. Petrogenetic modelling accounting for accessory mineral phases clearly shows that the trace element contents of leucosomes and melanosomes follow a distribution law consistent neither with equilibrium nor fractional melting. Their trace element patterns are best explained by the model of disequilibrium melting, with mixing of a few residual phases. The present results and previous Sr isotopic data as well raise the question of disequilibrium melting in anatexis of crustal material CRPG Contribution no 782  相似文献