New ages of carbonatitic and alkaline ultramafic rocks from Sweden and Finland

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Abstract
The following intrusions have been dated by the K-Ar method: Alnö (537 m.y.), Åvike Bay (542 m.y.), Kalix (1142 m.y.), Västervik (1559 m.y.) and Kortejärvi (1875 m.y.). Carbonatitic/alkaline intrusions from Scandinavia and the Kola Peninsula fall into three groups, namely, Caledonian, Grenville and Svecokarelian age-groups. A twofold division of the Svecokarelian group is indicated. The Caledonian intrusions occur in a relatively narrow zone parallelling the Caledonian fold belt; the Svecokarelian intrusions define a zone E. of the Caledonian intrusions.