Rare-earth elements in high-alumina basaltic rocks from Sardinia |
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| Authors: | J Dostal C Dupuy C Coulon |
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| Institution: | 1. Department of Geology, Saint Mary''s University, Halifax, N.S. Canada;2. Centre Géologique et Géophysique, U.S.T.L., Montpellier France;3. Laboratoire de Géologie Dynamique, Marseille France |
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| Abstract: | High-alumina basalts and basic andesites, which represent the most “primitive” magma types of the Cenozoic andesitic series of Sardinia, show a spatial chemical zonation with respect to REE. The basaltic rocks from the northern and south-central part of the island have REE patterns typical of calc-alkaline rocks with an enrichment of light REE and fractionation of heavy REE. In contrast, those from the southernmost part have a pattern similar to typical continental tholeiites with only a small light-REE enrichment and unfractionated heavy REE.The present data suggest that basaltic rocks may be formed by anatexis of upper-mantle material with mineral assemblages containing either garnet (calc-alkaline rocks) or spinel (rocks of tholeiitic affinities). The presence of garnet or spinel could merely reflect mineral phase transformation and indicates a different depth of fusion for the various types of basaltic rocks with those of tholeiitic affinities originating at a shallower depth than the calcalkaline rocks. The REE data are consistent with the generation of the basaltic rocks by partial melting of mantle peridotite overlying a subducted plate. |
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