Abstract

Clinopyroxene phenocrysts from the volcanic rocks of Lipari, one of the Aeolian Islands (Italy), were characterized by single-crystal X-ray diffraction and electron-microprobe analysis. They form three groups, related to different volcanic cycles. Although there is no evidence of tholeiitic rocks in the archipelago, the structural framework of these clinopyroxenes is close to those of clinopyroxene from subalkaline basalts of tholeiitic affinity. This feature may be ascribed to contamination of the magma by older gabbros in the lower crust, or to crystallization from an early magma of tholeiitic composition. Comparisons with analogues from other Aeolian Islands (Vulcano, Salina, Filicudi and Stromboli) highlight the fact that the Lipari clinopyroxene are low-pressure phenocrysts.

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