The subcontinental versus suboceanic debate,I Lead-neodymium-strontium isotopes in primary alkali basalts from a shield area the Ahaggar volcanic suite |
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Authors: | Claude J Allègre Bernard Dupré Bernard Lambret Pierre Richard |
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Institution: | 1. Laboratoire de Géochimie et Cosmochimie (LA 196), Institut de Physique du Globe, Universitéde Paris VI, 4 Place Jussieu, 75230 Cedex 05France;2. Département des Sciences de la Terre, Universitéde Paris VII, 4 Place Jussieu, 75230 Cedex 05France |
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Abstract: | Pb, Nd and Sr isotopic compositions have been determined in lherzolite-xenolith-bearing alkali-basalts from the center of the African shield. The present data are very similar to those reported for ocean-island basalts and do not support the hypothesis of different mantle sources for alkali-basalts from continental and oceanic areas. From these observations and on the basis of data obtained for xenolith in kimberlite and for tholeiitic continental basalts one may infer the following terrestrial mantle structure: whereas oceanic tholeiites would originate in upper oceanic mantle, oceanic and continental alkali basalts would come from the lower mantle and tholeiitic continental basalts from the continental lithosphere. |
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