ИСТИНА

Petro-geochemical study of basalts of hole 332b DSDP-37 Leg located near the MAR in the Azores Plateau area supports the tezis that about 3.5 million years ago rift magmatism in this region was presented by a poorly enriched type of MORB. For magmas of similar magnesia, two types of magmas have been identified: depleted and enriched. The established crystallization temperatures of about 1270°C for Fo90.5 are typical for tholeiitic magmas. The origin of magmas is associated with the melting of the peridotite mantle (Dmitriev et al., 1985). At the same time the melting source had a poor enrichment with lithophilic elements probably reflecting the addition to the depleted asthenosphere the substance from enriched sources such as the enriched metasomatic mantle of the Azores Plateau formed at earlier stages of the MAR opening (40-35o N).