Sur la présence de tholéiites à l'île Saint-Paul (Océan Indien) |
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| Authors: | M Girod G Camus Y Vialette |
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| Institution: | (1) Département des Sciences de la Terre, Université Claude Bernard, 86 rue Pasteur, F-69 Lyon-7éme;(2) Départment de Géologie et Minéralogie, Université de Clermont-Ferrand, 5 rue Kessler, F-63 Clermont-Ferrand;(3) Laboratoire associé de Géochronologie, C.N.R.S., Université de Clermont-Ferrand, 5 rue Kessler, F-63 Clermont-Ferrand |
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| Abstract: | The basalts and dolerites from Saint-Paul island, located on the east section of the Indian ridge, are reinvestigated. New chemical rock analysis show that they are caracterized by high Fe, low Mg, and various Al contents; they belong to quartz tholeiites and olivine tholeiites of Yoder and Tilley's classification. Two clinopyroxene analysis allow to confirm this tholeiitic relationship. Compared with abyssal tholeiites, those of Saint-Paul are dissimilar in respect to Al2O3/CaO and FeO/MgO ratios, Sr and Rb contents (231–308 ppm and 6 to 29 ppm respectively) and 87 Sr/86 Sr values (0,7041–0,7065). Bearing in mind the structural position of the island, this differences are discussed in light of experimental data. Saint-Paul's basalts and dolerites are products a magma fractionated according to a Fernner trend and probably issued from deeper part of the upper mantle than abyssal tholeiites. |
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