Chronological and geochemical study of lavas from the Chaîne des Puys,Massif Central,France: Evidence for crustal contamination |
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| Authors: | M Condomines P Morand G Camus L Duthou |
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| Institution: | (1) Laboratoire de Géochimie-Cosmochimie LA 196 et Département des Sciences de la Terre, Université Pierre et Marie Curie Paris VI et VII, 4 Place Jussieu, F-75230 Paris cedex 05, France;(2) L.A.N 10 Géochronologie-Volcanologie, Département de Géologie et Minéralogie, Université de Clermont Ferrand, 5 rue Kessler, F-63038 Clermont-Ferrand Cedex, France;(3) Present address: Institut et Observatoire de Physique du Globe du Puy de Dôme et Département de Géologie, 5rue Kessler, F-63038 Clermont-Ferrand, France |
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| Abstract: | Datations of ancient lavas from the Chaîne des Puys through the 230Th-238U radioactive disequilibrium method confirm the eruption of several basaltic or slightly differentiated lavas around 40,000 years ago. The study of (230Th/232Th)0 initial ratios of these lava flows clearly demonstrates the influence of a crustal contamination of magmas superimposed to crystal fractionation. This contamination probably affects many trace elements, in particular, U, Th and Sr. A model based on the (230Th/232Th)0 initial ratio variations of non-contaminated lavas permits to consider that the first eruptions in the Chaîne des Puys could have occurred about 100,000 years ago. |
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