Manioc : Portail | resultats 21 - 40 pour la recherche: step tourism

Personal narrative of travels to the equinoctial regions of America, during the years 1799-1804 / by Alexander von Humboldt and Aimé Bonpland ; translated from the French of Alexander von Humboldt and edited by Thomasina Ross. Volume 2
Auteur(s) : Bonpland, Aimé (1773-1858) Humboldt, Alexander von (1769-1859)
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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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Reports from committees : eighteen volumes. Sugar and coffee planting. Session 18 november 1847 - 5 september 1848. Part. 2
Auteur(s) : Grande Bretagne. House of commons. Library
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Le calvaire d'un innocent ; n° 95
Auteur(s) : D' Arzac, Jules
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Les colonies françaises : un siècle d'expansion coloniale
Auteur(s) : Terrier, Auguste (1873-1932) Dubois, Marcel (1856-1916)
Auteurs secondaires : France. Ministère des colonies (1894-1946)
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Exhumation of HP-LT metamorphic rocks in the Cyclades: constraints from Pressure-Temperature-time-strain
Auteur(s) : Labrousse, L. Huet, B. Monié, P. Jolivet, Laurent
Auteurs secondaires : Dpt for Geodynamics and Sedimentology [Vienne] ; University of Vienna [Vienna] 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) Institut des Sciences de la Terre d'Orléans (ISTO) ; Institut national des sciences de l'Univers (INSU - CNRS) - Université d'Orléans (UO) - Université François Rabelais - Tours - Centre National de la Recherche Scientifique (CNRS)

Éditeur(s) : HAL CCSD
Résumé : International audience
High Pressure - Low Temperature (HP-LT) rocks testify for burying and exhumation of crustal material in subduction zones. The question of their exhumation is nevertheless still unclear. The Aegean domain offers several HP-LT belts. Especially, the Attic-Cycladic Blueschist unit (ACBU) is an example of a HP-LT unit exhumed in a convergent and then in a divergent context. It actually appears in metamorphic core complexes (MCCs) formed in the back-arc of the subduction. The syn-convergence "message" is however difficult to read because of the post-convergence structural and thermal overprint that accompanied the formation of the MCCs. Particularly, the geometry, the timing and the amount of the syn-orogenic exhumation remain unclear. We investigate theses questions with metamorphic petrology (Andros and Ios islands) and phengite population, single grain and in situ 40Ar-39Ar geochronology (Andros, Tinos, Syros and Ios islands). Based on these new constraints and a synthesis of published data, we are able to refine the geometry, the timing and the modes of the exhumation of the ACBU. Data from the whole Cyclades exhibit little differences in the age and P-T conditions at the successive stages of syn-orogenic exhumation. The peak of pressure (500±50 °C-18±1 kbar) has been reached at 50-55 Ma. The onset of the exhumation occurred at 40-45 Ma in blueschist facies conditions, between a basal thrust and a summital detachment. The following decompression was accompanied by cooling until 30-35 Ma (400±50 °C-8±1 kbar). At that time, the boundary conditions switched to extension. The change in boundary conditions is recorded by slowing of the exhumation and isobare heating. The conditions of post-orogenic exhumation differ from an island to another. The onset of post-orogenic exhumation is dated around 30 Ma in the northern Cyclades and 25 Ma in the southern Cyclades. It is related to top-to-the-North deformation in all the studied domain. The end of ductile deformation below the detachments is also diachronous (21 Ma in the North and 18 Ma in the South). Finally, we propose a model for the final steps of the exhumation related to the intrusion of granitic bodies around 14 Ma.
American Geophysical Union, Fall Meeting
San Francisco, United States

insu-00860510
https://hal-insu.archives-ouvertes.fr/insu-00860510
BIBCODE : 2010AGUFM.T23C2301L

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