Geochemistry of ophiolites from the Chamrousse complex (Belledonne Massif,Alps) |
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| Authors: | J L Bodinier C Dupuy J Dostal F Carme |
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| Institution: | (1) Centre Géologique et Géophysique, Université des Sciences et Techniques, Place Eugène Bataillon, F-34060 Montpellier, France;(2) Department of Geology, Saint Mary's University, Halifax, Nova Scotia, Canada;(3) Département de Géologie, Université des Sciences, F-88039 Amiens, France |
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| Abstract: | The ophiolite complex of Chamrousse (Belledonne Massif, Alps), consists of mafic to ultramafic cumulates and non-cumulates metamorphosed to amphibolite facies grade. The non-cumulitic rocks are similar in chemical composition to recent ocean-floor olivine tholeiites (both N-type and enriched P-type). The distribution of lithophile elements shows that the non-cumulitic rocks represent several magmas of different parentage. The character of the magmas varies according to the time of emplacement.Geological and geochemical data suggest that the Chamrousse complex was formed at a spreading oceanic ridge. The dynamic partial melting of an upper mantle diapir generated tholeiitic melt which decreased in amount and in REE contents. The first melt, enriched in light REE, was generated along the axis of the ridge while the second batch of melt, of lesser quantity and slightly depleted in light REE, was emplaced on the flank of the ridge. The third melt formed cross-cutting dikes with REE abundances typical of N-type (strongly light REE depleted) mid-ocean ridge basalts. |
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