Mapping a geothermal anomaly using apatite (U‐Th)/He thermochronology in the Têt fault damage zone,eastern Pyrenees,France     

Gatan Milesi  Roger Soliva  Patrick Moni  Philippe Münch  Mathieu Bellanger  Olivier Bruguier  Michael Bonno  Audrey Taillefer  Sylvain Mayolle 《地学学报》2019,31(6):569-576

(U‐Th)/He ages on apatite obtained in the vicinity of the Têt fault hydrothermal system show a large variability. In the inner damage zone adjacent to the fault core, where fluid flows are concentrated, AHe ages display a large scatter (3–41 Ma) and apatite ageing. Samples from the outer damage zone show young ages with less dispersion (0.9–21.1 Ma) and apatite rejuvenation. Outside the damage zone, ages are consistent with the regional exhumation history between 20 and 12 Ma. The important age dispersion found in the damage zone is interpreted as the result of ⁴He mobility during fluid infiltration. Our results show that thermochronological data close to a fault should be interpreted with caution, but may offer a new tool for geothermal exploration.  相似文献   

River evaporation and corresponding heat fluxes in forested catchments          下载免费PDF全文

Audrey Maheu  Daniel Caissie  André St‐Hilaire  Nassir El‐Jabi 《水文研究》2014,28(23):5725-5738

River water temperature is a very important variable in ecological studies, especially for the management of fisheries and aquatic resources. Temperature can impact on fish distribution, growth, mortality and community dynamics. River evaporation has been identified as an important heat loss and a key process in the thermal regime of rivers. However, its quantification remains a challenge, mainly because of the difficulty of making direct measurements. The objectives of this study were to characterize the evaporative heat flux at different scales (brook vs river) and to improve the estimation of the evaporative heat flux in a stream temperature model at the hourly timescale. Using a mass balance approach with floating minipans, we measured river evaporation at an hourly timescale in a medium‐sized river (Little Southwest Miramichi) and a small brook (Catamaran Brook) in New Brunswick, Canada. With these direct measurements of evaporation, we developed mass transfer equations to estimate hourly evaporation rates from microclimate conditions measured 2 m above the stream. During the summer 2012, river evaporation was more important for the medium‐sized river with a mean daily evaporation rate of 3.0 mm day^?1 in the Little Southwest Miramichi River compared with that of 1.0 mm day^?1 in Catamaran Brook. Evaporation was the main heat loss mechanism in the two studied streams and was responsible for 42% of heat losses in the Little Southwest Miramichi River and 34% of heat losses in Catamaran Brook during the summer. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

New constraints on early Solar System chronology from Al-Mg and U-Pb isotope systematics in the unique basaltic achondrite Northwest Africa 2976     

Audrey Bouvier  Lev J. Spivak-Birndorf  Gregory A. Brennecka  Meenakshi Wadhwa 《Geochimica et cosmochimica acta》2011,75(18):5310-5323

We report elemental abundances and the isotopic systematics of the short-lived ²⁶Al-²⁶Mg (half-life of ∼0.73 Ma) and long-lived U-Pb radiochronometers in the ungrouped basaltic meteorite Northwest Africa (NWA) 2976. The bulk geochemical composition of NWA 2976 is clearly distinct from that of the eucrites and angrites, but shows broad similarities to that of the paired NWA 001 and 2400 ungrouped achondrites indicating that it is likely to also be paired with these two samples. The major and trace element abundances in NWA 2976 further indicate that it formed by extensive melting and magmatic fractionation processes on its parent body. The Al-Mg and Pb-Pb isotope systematics indicate that this meteorite represents the earliest stages of crust formation on a differentiated parent body in the early Solar System. The absolute Pb-Pb internal isochron age of NWA 2976, obtained from acid leaching residues of three whole-rock samples and two pyroxene separates, is 4562.89 ± 0.59 Ma (MSWD = 0.02). This Pb-Pb age is calculated using the measured ²³⁸U/²³⁵U ratio of a NWA 2976 whole-rock of 137.751 ± 0.018 (2σ) which was determined relative to the recently revised value of 137.840 ± 0.008 for the SRM 950a U isotope standard. The Al-Mg systematics reveal the presence of ²⁶Mg isotopic anomalies produced by the decay of ²⁶Al with an (²⁶Al/²⁷Al)₀ of (3.94 ± 0.16) × 10⁻⁷, and indicate a time of formation of 0.26 ± 0.18 Ma after the D’Orbigny angrite. Using the revised Pb-Pb age of 4563.36 ± 0.34 Ma for the D’Orbigny anchor (corrected for its U isotopic composition), we deduce an Al-Mg model age of 4563.10 ± 0.38 Ma for NWA 2976, which is consistent with its Pb-Pb internal isochron age.The concordance of the Pb-Pb and Al-Mg chronometers, when taking into account the differences in the U isotopic compositions of the D’Orbigny and NWA 2976 achondrites (whose parent bodies likely formed in distinct regions of early Solar System as indicated by their different oxygen isotopic compositions), implies that ²⁶Al was homogeneously distributed in the early Solar System. It also suggests that igneous processes on planetesimals, as represented by the formation of various basaltic meteorite groups that likely originated on distinct parent bodies (e.g., eucrites and angrites, as well as ungrouped achondrites), were widespread throughout the protoplanetary disk within the first ∼5 Ma of the history of the Solar System.  相似文献   

Evaluation of the frequency of skipped spawning in Norwegian spring-spawning herring     

James Kennedy  Jon Egil Skjraasen  Richard D.M. Nash  Aril Slotte  Audrey J. Geffen  Olav S. Kjesbu 《Journal of Sea Research》2011,65(3):327-332

Based upon an under-representation of second time spawners on the spawning grounds between 1935 and 1973, researchers have suggested that Norwegian spring-spawning (NSS) herring (Clupea harengus) frequently skip their second spawning event. In order to evaluate this claim with direct evidence, herring were collected over a period of three years from statutory surveys and commercial catches over a wide area covering the feeding, over-wintering and spawning grounds. The development stage of the ovaries was assessed and the intensity of atresia quantified. Only a negligible number of the analysed herring caught were considered likely to skip spawning, thus this phenomenon does not appear to be a common feature of the NSS herring stock at present. In addition, considering the reproductive strategy of herring, it seems doubtful that skipping the second spawning event has ever frequently occurred in this stock.  相似文献   

Metamorphosed calcium‐aluminum‐rich inclusions in CK carbonaceous chondrites     

Noël Chaumard  Bertrand Devouard  Audrey Bouvier  Meenakshi Wadhwa 《Meteoritics & planetary science》2014,49(3):419-452

CK chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6. Although CKs are described as calcium‐aluminum‐rich inclusion (CAI)‐poor objects, the abundance of CAIs in the 18 CK3–6 we analyzed ranges from zero to approximately 16.4%. During thermal metamorphism, some of the fine‐grained CAIs recrystallized as irregular assemblages of plagioclase + Ca‐rich pyroxene ± olivine ± Ca‐poor pyroxene ± magnetite. Coarse‐grained CAIs display zoned spinel, fassaite destabilization, and secondary grossular and spinel. Secondary anorthite, grossular, Ca‐rich pyroxene, and spinel derive from the destabilization of melilite, which is lacking in all CAIs investigated. The Al‐Mg isotopic systematics measured in fine‐ and coarse‐grained CAIs from Tanezrouft (Tnz) 057 was affected by Mg redistribution. The partial equilibration of Al‐Mg isotopic signatures obtained in the core of a coarse‐grained CAI (CG1‐CAI) in Tnz 057 may indicate a lower peak temperature for Mg diffusion of approximately 540–580 °C, while grossular present in the core of this CAI indicates a higher temperature of around 800 °C for the metamorphic event on the parent body of Tnz 057. Excluding metamorphic features, the similarity in nature and abundance of CAIs in CK and CV chondrites confirms that CVs and CKs form a continuous metamorphic series from type 3 to 6.  相似文献   

Electronic Publishing: the Role of a Large Scientific Society     

B. Bederson  H. Lustig 《Astrophysics and Space Science》1997,247(1-2):41-53

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Results from the Eso Large Program on Transneptunian Objects and Centaurs     

Boehnhardt  Hermann  Barucci  Antonella  Delsanti  Audrey  De Bergh  Catherine  Doressoundiram  Alain  Romon  Jennifer  Dotto  Elisabetta  Tozzi  Gianpaolo  Lazzarin  Monica  Fornasier  Sonia  Peixinho  Nuno  Hainaut  Olivier  Davies  John  Rousselot  Philippe  Barrera  Luis  Birkle  Kurt  Meech  Karen  Ortiz  JoseLuis  Sekiguchi  Tomohiko  Watanabe  Jun-ichi  Thomas  Nick  West  Richard 《Earth, Moon, and Planets》2003,92(1-4):145-156

BVRI photometry of 107 TNOs and Centaurs establishes the range of spectral gradients to be between –5 to 55%/100 nm (with one exception). A cluster of very red Cubewanos is firmly identified in orbits of low inclination and eccentricity beyond 40 AU from the Sun. Further correlations between surface colours and dynamical parameters (inclination and perihelion distance) are suggested for Cubewanos and scattered disk objects, but lack complete confidence for their reality. Plutinos and Centaurs do not show any clear correlation between surface colours and orbital parameters. We present in this paper 12 spectra obtained in the visible region and nine of them for which we obtained also near infrared spectra up to 2.4 microns. A few other objects have been observed, but the data are still under reduction and analysis. The principal reported results obtained are: (i) a wide range of visible slopes; (ii) evidence for surface variations on 2001 PT₁₃; and (iii) possible detection of few percent of water ice (1999 TC_36}, 2000 EB₁₇₃, 1999 DE₉, 2001 PT₁₃, 2000 QC₂₄₃, 1998 SG₃₅).  相似文献   

Pb-Pb dating constraints on the accretion and cooling history of chondrites     

Audrey Bouvier  Janne Blichert-Toft  Jeffrey D. Vervoort 《Geochimica et cosmochimica acta》2007,71(6):1583-1604

We have analyzed the Pb isotopic compositions of whole-rocks and various components (CAIs, chondrules, and/or mineral separates) of two carbonaceous chondrites, Allende (CV3) and Murchison (CM2), and nine ordinary chondrites, Sainte Marguerite (H4), Nadiabondi and Forest City (H5), Kernouvé (H6), Bjurböle (L/LL4), Elenovka and Ausson (L5), Tuxtuac (LL5), and Saint-Séverin (LL6) by MC-ICP-MS. Three CAI fractions from Allende define an isochron with an age of 4568.1 ± 9.4 Ma (MSWD = 0.08) and plot on the same isochron as fragments of the Efremovka inclusion E60 analyzed by Amelin et al. [Amelin, Y., Krot, A. N., Hutcheon, I. D., and Ulyanov, A. A. (2002a). Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions. Science297, 1679-1683]. When these two groups of samples are combined, the isochron yields an age of 4568.5 ± 0.5 (MSWD = 0.90), which is our best estimate of the age of the Solar System. Chondrules and pyroxene-olivine fractions from the ordinary chondrites yield ages that reflect the blocking of Pb isotope equilibration with the nebular gas. The combination of these ages with the corresponding metamorphic phosphate ages provides constraints on the thermal history of the different chondrite parent bodies. Among the H chondrites, Sainte Marguerite cooled to below ∼1100 K within a few My at 4565 Ma and to ∼800 K at 4563 Ma. Nadiabondi appears to have experienced a slightly more protracted cooling history with the corresponding interval lasting from 4559 to 4556 Ma. The data from Forest City and Kernouvé show evidence of late-stage perturbation with resulting U/Pb fractionation. Likewise, Pb isotopes in Tuxtuac (LL5) record a cooling history lasting from ∼4555 to 4544 Ma, which may indicate that the cooling history for the LL parent body was more prolonged than for the H parent body. We suggest a thermal evolution model for the growth of the planetary bodies based on the release of radiogenic heat from ²⁶Al and ⁶⁰Fe. This model incorporates the accretion rate, which determines the time at which the radiogenic heat becomes efficiently trapped, and the terminal size of the parent body, which controls its overall thermal inertia. The parent bodies of carbonaceous chondrites, which show little indication of metamorphic transformation, collect cooler nebular material at a relatively late stage. Small asteroids of ∼10-50 km radius accreting within 1-3 My could be the parent bodies of H and LL chondrites. The parent body of the L chondrites is likely to be a larger asteroid (r > 100 km) or possibly the product of collisions of smaller planetary bodies.  相似文献   

Neoliberal Governance and International Medical Travel in Malaysia by Meghann Ormond. Routledge,London, 2012, pp. xi + 162 (ISBN 978‐0‐415‐50238‐2).          下载免费PDF全文

Audrey Bochaton 《Singapore journal of tropical geography》2015,36(1):134-136

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Iron in monticellite as an oxygen barometer for kimberlite magmas     

Audrey Le Pioufle  Dante Canil 《Contributions to Mineralogy and Petrology》2012,163(6):1033-1046

Monticellite is a common magmatic mineral in the groundmass of kimberlites. A new oxygen barometer for kimberlite magmas is calibrated based on the Fe content of monticellite, CaMgSiO₄, in equilibrium with kimberlite liquids in experiments at 100 kPa from 1,230 to 1,350°C and at logfO₂ from NNO-4.1 to NNO+5.3 (where NNO is the nickel–nickel oxide buffer). The XFe_Mtc/XFe_liq was found to decrease with increasing fO₂, consistent with only Fe²⁺ entering the monticellite structure. Although the XFe-in-monticellite varies with temperature and composition, these dependencies are small compared to that with fO₂. The experimental data were fitted by weighted least square regression to the following relationship: \Updelta \textNNO = \frac{ log[ 0.858( ±0.021)\fracX_\textFe^\textLiq X_\textFe^\textMtc ] - 0.139( ±0.022) }0.193( ±0.004) \Updelta {\text{NNO}} = \frac{{\left\{ {\log \left[ {0.858( \pm 0.021)\frac{{X_{\text{Fe}}^{\text{Liq}} }}{{X_{\text{Fe}}^{\text{Mtc}} }}} \right] - 0.139( \pm 0.022)} \right\}}}{0.193( \pm 0.004)} where ΔNNO is the fO₂ relative to that of the Nickel-bunsenite (NNO) buffer and XFe_liq/XFe_Mtc is the ratio of mole fraction of Fe in liquid and Fe-in-monticellite (uncertainties at 2σ). The application of this oxygen barometer to natural kimberlites from both the literature and our own investigations, assuming the bulk rock FeO is that of their liquid FeO, revealed a range in fO₂ from NNO-3.5 to NNO+1.7. A range of Mg/(Mg + Fe²⁺) (Mg#) for kimberlite melts of 0.46–0.88 was derived from the application of the experimentally determined monticellite-liquid Kd Fe²⁺–Mg to natural monticellites. The range in Mg# is broader and less ultramafic than previous estimates of kimberlites, suggesting an evolution under a wide range of petrologic conditions.  相似文献