Contribution of clinopyroxene EMP and SIMS data to the understanding of magmatic processes: an example from Filicudi Island (Aeolian Arc, Southern Tyrrhenian Sea)
Santo, Alba P
published: Jul 7, 1998
ArtNo. ESP154017302004, Price: 29.00 €
Clinopyroxenes from basaltic, basaltic andesitic and high-K calc-alkaline andesitic rocks of Filicudi Island (Aeolian Arc, Southern Tyrrhenian Sea) have been investigated by means of Electron Microprobe and Secondary Ion Mass Spectrometry. Texturally these c1inopyroxenes can be divided into two groups: 1) euhedral and clear phenocrysts and 2) rounded, dusty or sieved phenocrysts. Both groups span similar compositional ranges with Wo 34-48, En 38-50 and Fs 4-25. Basalts and basaltic andesites contain clinopyroxene of diopsidic and augitic composition, whereas high-K andesites contain exclusively augite. In terms of major-element concentrations, the phenocrysts exhibit complex variation of Mg, Fe and Ca from core to rim. Clinopyroxene phenocrysts and microphenocrysts display a number of compositional features suggesting disequilibrium with the groundmass. These include: i) Fe/Mg ratios increasing towards the core, ii) wide ranges of some trace elements, and iii) REE contents higher in the core than in the rim. These characteristics suggest a mixing process among magmas of different composition and degree of evolution and support the hypothesis that this process has played an important role during the evolution of Filicudi magmas, as suggested by previously obtained whole rock data.