Manioc : Portail | resultats 21 - 40 pour la recherche: Roofing materials

Ten days in camp on Mt Pelé, Martinique. The Volcano Six Years after the Great Eruption.
Auteur(s) : Hovey, Edmund Otis (1862-1924)
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Antigua and the Antiguans: a full account of the colony and its inhabitants from the time of the Caribs to the present day, interspersed with anecdotes and legends : also, an impartial view of slavery and the free labour systems, the statistics of the island, and biographical notices of the principal families, Volume 1
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Contamination of MORB by anatexis of magma chamber roof rocks: Constraints from a geochemical study of experimental melts and associated residues
Auteur(s) : France, Lyderic Koepke, Juergen Macleod, Christopher J. Ildefonse, Benoit Godard, Marguerite Deloule, Etienne
Auteurs secondaires : Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Centre de Recherches Pétrographiques et Géochimiques (CRPG) ; Université de Lorraine (UL) - Centre National de la Recherche Scientifique (CNRS) Institut fuer Mineralogie, Universitaet Hannover School of Earth & Ocean Sciences, Cardiff University Manteau et Interfaces ; Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) - Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Mid-ocean ridge basalts (MORBs) are the most abundant magmas produced on Earth. They are widely studied to infer mantle compositions and melting processes. However, MORB liquids are also the complex end-product of a variety of intra-crustal processes such as partial or fractional crystallization, melt–rock interaction, and contamination. Deciphering the relative contribution of these different processes is of first-order importance. Contamination at ocean crustal levels is likely, and may occur at magma chamber margins where fresh magmas can interact with previously hydrothermally altered rocks. Characterizing the composition of this crustal contaminant component is critical if we are to understand the relative importance of each component in the resulting MORB liquid.Here we present the results of experiments designed to reproduce the processes occurring at oceanic magma chamber roofs, where crustal contamination should be most extensive, by melting a representative sample of the sheeted dike complex. Anatectic melts thus produced are likely to represent the principal crustal contaminant in MORB. These melts were characterized for major and trace elements, showing B, Zr, Hf, and U enrichment, and Sr, Ti, and V depletion relative to original MORB liquids. In comparison to the starting material, relative element fractionations are observed in the anatectic melts, with enrichments of: U relative to Ba, Nb, and Th; LREE and MREE relative to Sr; and Zr–Hf relative to LREE. Bulk partition coefficients for element partitioning during magma chamber roof anatexis are derived and proposed as valuable tools for tracking MORB contamination.Comparison with natural samples from the East Pacific Rise and the Oman ophiolite shows that anatectic melts can crystallize in situ to form oceanic plagiogranite intrusions, and that residual assemblages associated with the hydrous partial melting stage are represented by hornfelsic dikes and enclaves (also named granoblastic basalts). We now recognize these as commonplace at the root of the sheeted dike complex both at present-day and fossil oceanic spreading centers.
ISSN: 0024-4937

hal-01115500
https://hal.archives-ouvertes.fr/hal-01115500
DOI : 10.1016/j.lithos.2014.05.018

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Speeches of Henry Lord Brougham, upon questions relating to Publics Rights, Duties, and Interests
Auteur(s) : Brougham, Henry (1778-1868)
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Six months in the West Indies
Auteur(s) : Coleridge, Henry Nelson (1798-1843)
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Speeches of Henry Lord Brougham, upon questions relating to Publics Rights, Duties, and Interests
Auteur(s) : Brougham, Henry (1778-1868)
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The history, civil and commercial, of the British colonies in the West Indies. Volume I
Auteur(s) : Edwards, Bryan (1743-1800)
Auteurs secondaires : Bartolozzi, Francesco (1727-1815) West, Benjamin (1738-1820) Milton, Thomas (1743?-1827)
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Santo Domingo : past and present with a glance at Hayti
Auteur(s) : Hazard, Samuel (1834-1876)
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Analog experiments and mechanical analysis applied to the Alaskan Accretionary Wedge
Auteur(s) : Gutscher, Marc-André, Kukowski, Nina Malavieille, Jacques Lallemand, Serge
Auteurs secondaires : Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Seismic reflection profiles from the sediment rich Alaska subduction zone image short, frontally accreted, imbricate thrust slices and repeated sequences of long, underthrust sheets. Rapid landward increases in wedge thickness, backthrusting, and uplift of the forearc are observed, suggesting underthrusting beneath the wedge. These features and a widely varying frontal wedge morphology are interpreted to be caused by different modes of accretion active concurrently along the trench at different locations. Episodic wedge growth is observed in high basal friction experiments using sand as an analog material. Two phases of an accretionary cycle can be distinguished: frontal accretion of short imbricate thrust slices, alternating with underthrusting of long, undeformed sheets. The phase is shown experimentally to depend upon the surface slope of the wedge. Mechanical analysis of the forces at work predicts these two modes of deformation due to the varying frictional forces and yield strengths for a temporally varying wedge geometry. Maximum length of thrust slices is calculated for experimental conditions and confirmed by the observations. For a steep frontal slope (at the upper limit of the Mohr-Coulomb taper stability field) the overburden is too great to permit underthrusting, and failure occurs repeatedly at the wedge front producing short imbricate slices. The wedge grows forward, lowering the surface angle to the minimum critical taper. For a shallow frontal slope the reduced overburden along an active roof thrust permits sustained underthrusting, causing frontal erosion and backthrusting, steepening the wedge and thus completing the cycle.
ISSN: 0148-0227

hal-01261538
https://hal.archives-ouvertes.fr/hal-01261538
https://hal.archives-ouvertes.fr/hal-01261538/document
https://hal.archives-ouvertes.fr/hal-01261538/file/gutscherJGR1998.pdf

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