Transformations of magnetic mineralogy in rocks revealed by difference of hysteresis loops measured after stepwise heating: theory and case studies     

Bernard Henry  Diana Jordanova  Neli Jordanova  Maxime Le Goff 《Geophysical Journal International》2005,162(1):64-78

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Cadomian volcanosedimentary complexes across the Ediacaran–Cambrian transition of the Eastern Pyrenees,southwestern Europe     

Padel  Maxime  Álvaro  J. Javier  Casas  Josep Maria  Clausen  Sébastien  Poujol  Marc  Sánchez-García  Teresa 《International Journal of Earth Sciences》2018,107(5):1579-1601

International Journal of Earth Sciences - The volcanism hosted by the Ediacaran–Terreneuvian Canaveilles Group of the Eastern Pyrenees displays two distinct geochemical affinities: (1)...  相似文献   

Experimental and theoretical study of the vibrational properties of diaspore (α-AlOOH)     

Simon?Delattre  Etienne?BalanEmail author  Michele?Lazzeri  Marc?Blanchard  Maxime?Guillaumet  Olivier?Beyssac  Eiken?Haussühl  Bj?rn?Winkler  Ekhard?K.?H.?Salje  Georges?Calas 《Physics and Chemistry of Minerals》2012,39(2):93-102

Vibrational properties of diaspore, α-AlOOH, have been re-investigated using room-temperature single-crystal Raman spectroscopy and low-temperature powder infrared (IR) transmission spectroscopy. First-principles harmonic calculations based on density functional theory provide a convincing assignment of the major Raman peaks and infrared absorption bands. The large width of the Raman band related to OH stretching modes is ascribed to mode–mode anharmonic coupling due to medium-strength H-bonding. Additional broadening in the powder IR spectrum arises from depolarization effects in powder particles. The temperature dependence of the IR spectrum provides a further insight into the anharmonic properties of diaspore. Based on their frequency and temperature behavior, narrow absorption features at ~2,000 cm⁻¹ and anti-resonance at ~2,966 cm⁻¹ in the IR spectrum are interpreted as overtones of fundamental bending bands.  相似文献   

Statistical downscaling in the arid central Andes: uncertainty analysis of multi-model simulated temperature and precipitation     

Maxime Souvignet  J��rgen Heinrich 《Theoretical and Applied Climatology》2011,106(1-2):229-244

Statistical downscaling is a technique widely used to overcome the spatial resolution problem of General Circulation Models (GCMs). Nevertheless, the evaluation of uncertainties linked with downscaled temperature and precipitation variables is essential to climate impact studies. This paper shows the potential of a statistical downscaling technique (in this case SDSM) using predictors from three different GCMs (GCGM3, GFDL and MRI) over a highly heterogeneous area in the central Andes. Biases in median and variance are estimated for downscaled temperature and precipitation using robust statistical tests, respectively Mann?CWhitney and Brown?CForsythe's tests. In addition, the ability of the downscaled variables to reproduce extreme events is tested using a frequency analysis. Results show that uncertainties in downscaled precipitations are high and that simulated precipitation variables failed to reproduce extreme events accurately. Nevertheless, a greater confidence remains in downscaled temperatures variables for the area. GCMs performed differently for temperature and precipitation as well as for the different test. In general, this study shows that statistical downscaling is able to simulate with accuracy temperature variables. More inhomogeneities are detected for precipitation variables. This first attempt to test uncertainties of statistical downscaling techniques in the heterogeneous arid central Andes contributes therefore to an improvement of the quality of predictions of climate impact studies in this area.  相似文献   

High resolution LA-ICP-MS mapping of U and Th isotopes in an early Pleistocene equid tooth from Fuente Nueva-3 (Orce, Andalusia, Spain)     

Mathieu Duval  Maxime Aubert  John Hellstrom  Rainer Grün 《Quaternary Geochronology》2011,6(5):458-467

We have produced detailed maps of U and Th isotopes for three cross-sections of an Early Pleistocene equid tooth from the archaeological site of Fuente Nueva-3 (Orce, Andalusia, Spain). This permits us to visualise, for the first time, U migration processes in 3 dimensions. The tooth shows a concentration gradient from the top to the base, indicating the U profile had not equilibrated after >1 Ma. The spatial pattern of ²³⁰Th/²³⁴U and ²³⁴U/²³⁸U indicates complex U-mobilisation processes over the last 100 ka, dominated by small-scale redistribution of U. Leaching from the tooth through the pulp cavity started at least 93 ka ago with several later phases in various domains of the dentine and cement. This leaching event could have been triggered by changes in the local hydrological regime associated with periods of increased erosion in the Guadix-Baza basin. The results illustrate the difficulty of dating faunal material from Early Pleistocene sites. They also demonstrate that dental tissues can neither be considered as homogeneous media for U-diffusion, nor behave as closed systems for U-series isotopes because diagenetic alterations seem to trigger U-migration. The results do not support the notion that U-uptake into dental tissues is necessarily of short duration. Nevertheless, rapid laser ablation scanning can be used to identify suitable samples for dating as well as domains within the teeth that may have preserved original isotopic signatures, i.e. domains that have not been affected by recent U-mobilisation process.  相似文献   

Line-broadening effects in the powder infrared spectrum of apatite     

Etienne Balan  Simon Delattre  Damien Roche  Loïc Segalen  Guillaume Morin  Maxime Guillaumet  Marc Blanchard  Michele Lazzeri  Christian Brouder  Ekhard K. H. Salje 《Physics and Chemistry of Minerals》2011,38(2):111-122

The crystallinity of natural and synthetic apatite samples is often determined from the broadening of ν ₄ PO₄ infrared absorption bands. However, various physical mechanisms contribute to the observed linewidth. In the present study, the factors determining the linewidth in the powder spectrum of synthetic fluorapatite and hydroxyapatite samples are investigated. The temperature dependence of the infrared spectrum (10–270 K) is used to assess the respective contributions of homogeneous broadening, related to the decay of phonons through anharmonic coupling, and heterogeneous broadening related to elastic strain and macroscopic electrostatic effects. This latter contribution is dominant in the investigated samples and depends on the shape of powder particles. It is discussed under the light of the theoretical modeling of the low-frequency dielectric properties of apatite based on first-principles density functional theory calculations. The linewidth of the weak ν ₁ PO₄ absorption band provides a reliable information on microscopic sources of broadening, i.e., apatite crystallinity. In comparison, the other more intense PO₄ bands are more sensitive to long-range electrostatic effects.  相似文献   

Hierarchical modelling of archaeomagnetic data and curve estimation by moving average technique     

Philippe Lanos  Maxime Le Goff  Mary Kovacheva  Elisabeth Schnepp 《Geophysical Journal International》2005,160(2):440-476

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Distortion of the geomagnetic field in volcanic terrains: an experimental study of the Mount Etna stratovolcano     

Jean-Claude Tanguy  Maxime Le Goff 《Physics of the Earth and Planetary Interiors》2004,141(1):59-70

The inclination (I), declination (D) and total intensity (F) of the geomagnetic field were measured on Mount Etna in 1989-1991 at a dozen sites previously sampled for archeomagnetic studies. The purpose of the work was to determine the variations of these parameters at 30 cm above ground level, and how the distortion from the main field can affect the archeomagnetic record of volcanic rocks. Ten measurements were usually performed at each site with a three-component flux-gate magnetometer, whose estimated precision is ±0.2° on direction and ±50 nT on intensity. This was considered sufficient on volcanic areas with highly magnetized rocks and where the geomagnetic gradient may be in excess of 1000 nT/m. Results averaged for each site generally show small variations in intensity (±3% of the total field) and direction (±1.5°). The averaged values of the 12 sites (I=52.6°, D=0.3°, F=44010 nT) are very close to those measured in sedimentary terrain away from the volcano (I=52.9°, D=0.35°, F=44110 nT), themselves consistent with the interpolated IGRF in eastern Sicily. The largest deviations of the geomagnetic direction have been observed on four sites, three of them located on the South flank between 1900 and 700 m elevation. It is suggested that these anomalies are mainly related to dyke swarms which are common within the South Rift Zone of Mount Etna. Our findings show that reliable archeomagnetic results can be obtained from volcanic rocks, provided that lavas of the same eruption are sampled on several sites distributed over the largest possible area.  相似文献   

Structures in the Canyon Mountain Ophiolite indicate an island-arc intrusion     

Maxime Misseri  Franoise Boudier 《Tectonophysics》1985,120(3-4):191-209

Lithosphere created in an interarc basin is expected to be characterized by features distinguishing it from “normal” oceanic lithosphere. Apart from island-arc geochemical affinities and from the occurrence of hydrous high-T parageneses in the mantle and deep crustal sequences, it is expected that due to a low rate of spreading, vertical transport prevails over lateral drifting.

The Canyon Mountain complex located in an island-arc environment of Permo-Triassic age offers a remarkable illustration of these expected geological characteristics. In particular, mantle diapirism is deduced from the structural study. Smaller diapirs are formed in crustal formations. The intrusions took place at variable temperatures (1300°–800°C) and were accompanied by multistage melting in hydrous conditions.  相似文献   

Reply to the Comment on “Chronology of Vesuvius' activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources” by R. Lanza and E. Zanella     

Claudia Principe  Jean-Claude Tanguy  Simone Arrighi  Maxime Le Goff 《Bulletin of Volcanology》2006,68(4):397-398

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