HETEROGENEITY OF ISOTOPE SOURCES OF ALKALINE MAGMATISM IN THE HOT SPOT OF THE SOUTHWESTERN ATLANTIC: FERNANDO DE NORONHA ISLANDS

Abstract

New data on age and isotopic characteristics of alkaline magmatism in the hot spot of the Fernando de Noronha Islands have been obtained. For the first time, a new aspect of isotope heterogeneity expressed in enrichment in radiogenic Sr was revealed. The Fernando de Noronha Archipelago is situated 345 km away from the Atlantic coast of Brazil and is confined to a transform fracture zone. The Fernando de Noronha lineament is traced far to the west by the Rocas atoll, a chain of seamounts, and occurrences of alkaline magmatism on the continent. According to the tectonic interpretation, this lineament is regarded as a track of a hot spot.