Abstract
Sr isotope compositions are reported for 37 volcanic rocks from the Island of Stromboli and for 8 samples from the islands of Filicudi and Alicudi, Aeolian Arc, south Tyrrhenian Sea. The rocks cover the entire compositional range of the Aeolian volcanics which vary from calc-alkaline (CA) to high-K calc-alkaline (HKCA), shoshonitic (SHO) up to potassic series (KS). In the Island of Stromboli the Sr isotopic ratio ranges from 0.70519 to 0.70757 and increases regularly from the CA to HKCA and SHO, reaching the highest values in the KS volcanics. Significant variations are also observed within individual magmatic series, especially the KS. The Filicudi and Alicudi samples include typical CA basalts and basaltic andesites that display lower Sr isotopic ratios (0.70379–0.70538) than the Stromboli volcanics. The data indicate that fractional crystallization has been the leading process in the evolution of the HKCA and SHO series, although some samples show clear evidence of mixing with CA and KS magmas. The KS volcanics display a range of isotopic composition which is negatively correlated with Sr abundance, indicating processes of crustal assimilation. The overall Sr isotopic variations in the Stromboli rocks and the positive relationship with K enrichment are interpreted as indicating either the genesis of parent magmas of the different series in a heterogeneous mantle source or formation by processes of crystal fractionation associated with assimilation and mixing in a periodically refilled and tapped deep magma chamber.
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