Lithium isotopes as indicators of meteorite parent body alteration     

Mark A. Sephton  Rachael H. James  Manuela A. Fehr  Philip A. Bland  Matthieu Gounelle 《Meteoritics & planetary science》2013,48(5):872-878

Hydrothermal processing on planetesimals in the early solar system produced new mineral phases, including those generated by the transformation of anhydrous silicates into their hydrated counterparts. Carbonaceous chondrites represent tangible remnants of such alteration products. Lithium isotopes are known to be responsive to aqueous alteration, yet previously recognized variability within whole rock samples from the same meteorite appears to complicate the use of these isotopes as indicators of processing by water. We demonstrate a new way to use lithium isotopes that reflects aqueous alteration in carbonaceous chondrites. Temperature appears to exert a control on the production of acetic acid‐soluble phases, such as carbonates and poorly crystalline Fe‐oxyhydroxides. Temperature and degree of water‐rock interaction determines the amount of lithium isotope fractionation expressed as the difference between whole rock and acetic acid‐leachable fractions. Using these features, the type 1 chondrite Orgueil (δ⁷Li_{(whole rock)} = 4.3‰; Δ⁷Li_{(acetic‐whole)} = 1.2‰) can be distinguished from the type 2 chondrites Murchison (δ⁷Li_{(whole rock)} = 3.8; Δ⁷Li_{(acetic‐whole)} = 8.8‰) and carbonate‐poor Tagish Lake (δ⁷Li_{(whole rock)} = 4.3; Δ⁷Li_{(acetic‐whole)} = 9.4‰). This initial study suggests that lithium isotopes have the potential to reveal the role of liquid water in the early solar system.  相似文献   

Elliptical Descriptors: Some Simplified Morphometric Parameters for the Quantification of Complex Outlines     

Matthieu Schmittbuhl  Bernard Allenbach  Jean-Marie Le Minor  André Schaaf 《Mathematical Geology》2003,35(7):853-871

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Small Antarctic micrometeorites: A mineralogical and in situ oxygen isotope study     

Matthieu GOUNELLE  Ccile ENGRAND  Michel MAURETTE  Gero KURAT  Kevin D. McKEEGAN  Franz BRANDSTTTER 《Meteoritics & planetary science》2005,40(6):917-932

Abstract— We have investigated the texture, bulk chemistry, mineralogy, as well as the anhydrous minerals oxygen isotopic composition of 67 small Antarctic micrometeorites (AMMs) collected at Cap Prudhomme, Antarctica, and belonging to the currently poorly studied size fraction 25–50 μm. When compared to larger (50–400 μm) micrometeorites collected at the same site in Antarctica with the same techniques, no significant differences are found between the two populations. We therefore conclude that the population of Cap Prudhomme AMMs is homogeneous over the size range 25–400 μm. In contrast, small AMMs have different textures, mineralogy, and oxygen isotopic compositions than those of stratospheric interplanetary dust particles (IDPs). Because small AMMs (<50 μm) overlap in size with IDPs, the differences between these two important sources of micrometeorites can no longer be attributed to a variation of the micrometeorite composition with size. Physical biases introduced by the collection procedures might account for these differences.  相似文献   

Calcification rate influence on trace element concentrations in aragonitic bivalve shells: Evidences and mechanisms     

Matthieu Carré  Ilhem Bentaleb  Elmer Ordinola  Michel Fontugne 《Geochimica et cosmochimica acta》2006,70(19):4906-4920

Trace elements in calcareous organisms have been widely used for paleoclimatic studies. However, the factors controlling their incorporation into mollusc shells are still unclear. We studied here the Sr, Mg, Ba and Mn serial records in the shells of two aragonitic marine bivalve species: Mesodesma donacium and Chione subrugosa from the Peruvian Coast. The elemental concentrations were compared to local temperature and salinity records. The relationships with crystal growth rate G were investigated thanks to well defined periodic growth structures providing a precise shell chronology. Our results show that for both species, environmental parameters only have minor influence, whereas crystal growth rate strongly influences trace elements concentrations, especially for Sr (explaining up to 74% of the variance). The relationship between G and Sr/Ca exhibits variability among the shells as well as inside the shells. For a same growth rate value, Sr/Ca values are higher in more curved shell sections, and the growth rate influence is stronger as well. We show that intercellular and Ca²⁺-pump pathways cannot support the calcification Ca²⁺ flux, leading us to propose an alternative mechanism for ionic transport through the calcifying mantle, implying a major role for calcium channels on mantle epithelial cell membranes. In this new calcification model, Sr/Ca shell ratios is determined by Ca²⁺-channel selectivity against Sr²⁺, which depends (i) on the electrochemical potential imposed by the crystallisation process and (ii) on the Ca²⁺-channel density per surface unit on mantle epithelia.  相似文献   

Erratum à l'article Enregistrements sismologiques de l&#x27;explosion sur le site de l&#x27;usine AZF (Toulouse,France): [C. R. Geoscience 334 (2002) 155–161]     

Annie Souriau  Matthieu Sylvander  Valérie Maupin  Jean-François Fels  Alexis Rigo 《Comptes Rendus Geoscience》2003,335(5):495

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Enregistrements sismologiques de l'explosion sur le site de l'usine AZF (Toulouse,France)Seismological records of an explosion at the AZF chemical complex in Toulouse,France     

Annie Souriau  Matthieu Sylvander  Valérie Maupin  Jean-François Fels  Alexis Rigo 《Comptes Rendus Geoscience》2002,334(3):155-161

This study presents a detailed analysis of the seismic records of a strong explosion that occurred on 21 September 2001 at a chemical complex located south of Toulouse, France, and provoked important damages. The explosion, which is equivalent to a 3.4 magnitude earthquake, has been recorded at most of the stations of the National Seismological Network, as well as at a station under test at the ‘Observatoire Midi-Pyrénées’, 4.2 km away from the epicentre. The main seismic phases are interpreted using the known crustal structures, and a modelling with synthetic seismograms is performed. To cite this article: A. Souriau et al., C. R. Geoscience 334 (2002) 155–161.  相似文献   

Ice mass change in Greenland and Antarctica between 1993 and 2013 from satellite gravity measurements     

Matthieu J. Talpe  R. Steven Nerem  Ehsan Forootan  Michael Schmidt  Frank G. Lemoine  Ellyn M. Enderlin  Felix W. Landerer 《Journal of Geodesy》2017,91(11):1283-1298

We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.  相似文献   

Influence of temperature on the distribution of stress and displacement in a volcano: a numerical approach     

L Chevallier  W J Verwoerd 《Bulletin of Volcanology》1990,52(6):413-425

A previously published geological model and numerical (finite element) simulation of a basaltic vollano is extended by introducing temperature-dependent elastic parameters. The geological model is composed of a shield with a central volcanic cone resting on oceanic crust. The magma system consists of a 3-km-deep upper reservoir from which rises a central column. The model of the temperature field inside the volcano is based on geological observations and comprises (1) a hot zone, 200–300-m thick around the magma system where temperature drops rapidly by conduction and (2) a cooler zone where temperature gently decreases by convection of circulating fluids. The temperature-dependent parameters, the Young modulus (E), the Poisson coefficient (v), and the coefficient of linear thermal expansion (), (of which the first two show a non-linear variation with temperature), introduce heterogeneity in the medium. Three zones with different mechanical behaviour are distinguished in the volcanic edifice. Shearing and strong deformation processes are prominent next to the magma system (in the less rigid, hot, confined zone), radial cracks are likely to be initiated in the central part of the volcano (where tiffness increases), and finally concentric vertical or outward-dipping fissures are associated with horizontal extension towards the surface (with cold and stiff matenal and a low state of thermal stress). The results are used to propose a revised model of the internal structure of basaltic oceanic intraplate volcanoes.  相似文献   

The Rwenzori Mountains,a landslide-prone region?     

Liesbet Jacobs  Olivier Dewitte  Jean Poesen  Damien Delvaux  Wim Thiery  Matthieu Kervyn 《Landslides》2016,13(3):519-536

With its exceptionally steep topography, wet climate, and active faulting, landslides can be expected to occur in the Rwenzori Mountains. Whether or not this region is prone to landsliding and more generally whether global landslide inventories and hazard assessments are accurate in data-poor regions such as the East African highlands are thus far unclear. In order to address these questions, a first landslide inventory based on archive information is built for the Rwenzori Mountains. In total, 48 landslide and flash flood events, or combinations of these, are found. They caused 56 fatalities and considerable damage to road infrastructure, buildings, and cropland, and rendered over 14,000 persons homeless. These numbers indicate that the Rwenzori Mountains are landslide-prone and that the impact of these events is significant. Although not based on field investigations but on archive data from media reports and laymen accounts, our approach provides a useful complement to global inventories overlooking this region and increases our understanding of the phenomenon in the Rwenzori Mountains. Considering the severe impacts of landslides, the population growth and related anthropogenic interventions, and the likelihood of more intense rainfall conditions, there is an urgent need to invest in research on disaster risk reduction strategies in this region and other similar highland areas of Africa.  相似文献   

Tectonic and structural evolution of Gough volcano: A volcanological model     

Luc Chevallier 《Journal of Volcanology and Geothermal Research》1987,33(4)

Morphostructural, stratigraphic and tectonic data indicate that the evolution of Gough volcano is similar to other oceanic intraplate volcanoes, is older than 1 Ma, and is related to a transform fault. At least six evolutionary stages can be distinguished within two major magmatostructural periods dominated by basaltic and trachytic magmas, respectively.The basaltic shield volcano is characterized by a curved, elongated shape in plan and a rift zone with a high density of dykes, combined with a radial intrusive system. The latter is interpreted as being fed by a magma chamber some 4 km below the surface. The activity of the volcano became more centralized at the end of the basaltic period and its slopes became steeper. This corresponds to the development of a shallower and narrower central conduit in the edifice. The basaltic period was terminated by formation of a shield caldera related to the 4 km deep magma chamber. The term “shield caldera” is used for a collapse structure that is postmagmatic, large in comparison with the diameter of the volcano, and delimited by normal faults that do not show a closed circular pattern but rather a series of arcs. In contrast, summit calderas are defined as smaller, circular-shaped, centrally situated, synmagmatic features, related to a central shallow column. During the basaltic period, landslides were generated on the flanks of the edifice as a result of slope stability factors which are not easy to determine at present, and dynamic factors among which the intrusion of magma along a curved zone certainly played a major role.The trachytic period is characterized by comparatively rare pyroclastic deposits and a large volume of thick flows extruded from domes. These extrusions, as well as plugs, formed from vertical cylindrical columns of magma rising from shallow individual magma pockets fed by the main reservoir.  相似文献