Apatite fission track analysis in the Argentera massif: evidence of contrasting denudation rates in the External Crystalline Massifs of the Western Alps |
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| Authors: | S Bogdanoff A Michard M Mansour & G Poupeau |
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| Institution: | Laboratoire de Géologie structurale, Universitéde Paris-Sud, Bâtiment 504, 91405 Orsay, France; Laboratoire de Géologie structurale, Universitéde Paris-Sud, Bâtiment 504, 91405 Orsay, France, and, Laboratoire de Géologie, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris cedex 05, France; Département de Géologie, Facultédes Sciences Aïn Chock, B.P. 5366, Maarif, Casablanca, Morocco; UPRESA 5025 CNRS, Maison des Géosciences, B.P. 53, 38041 Grenoble cedex 9, France |
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| Abstract: | Apatite fission track dating from a central transect in the Argentera massif (southernmost External Crystalline Massif = ECM) yielded ages between 8.05 ± 0.6 and 2.4 ± 0.2 Myr, with a positive age/altitude correlation above 3 Ma, 1200 m. Recognising a thermal peak at c . 250°C, 33 Ma, based on stratigraphic, metamorphic and 39Ar/40Ar data, the present results suggest a slow cooling rate (8–5°C) for the Argentera massif during the Oligocene–early Pliocene. This rate compares with that from the Pelvoux massif, but contrasts with those observed in the northern ECM (Mont-Blanc and Aar: up to 14°C Myr?1) for the same time interval. This can be related to the different location of the ECM within the collided European margin. At about 3–4 Ma, the denudation rate would have increased up to c . 1 mm yr?1 in the Argentera massif, reaching the same value as in the Belledonne and northern ECM, likely a consequence of Penninic thrust inversion. |
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