Crystal chemistry of trioctahedral micas in the top sequences of the Colli Albani volcano, Roman Region, central Italy

Trioctahedral mica crystals are frequently found in the volcanoclastic products emplaced during the final stages of the activity of the Colli Albani volcano (Roman Region, central Italy). In the youngest phreatomagmatic deposits, mica is found either as a minor mineral phase in holocrystalline eject...

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Bibliographic Details
Published in:Lithos 2009-12, Vol.113 (3-4), p.507-520
Main Authors: Laurora, Angela, Malferrari, Daniele, Brigatti, Maria Franca, Mottana, Annibale, Caprilli, Enrico, Giordano, Guido, Funiciello, Renato
Format: Article
Language:English
Subjects:
Colli Albani volcano
Crystal-chemistry
Petrological processes
Trioctahedral micas
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Summary:Trioctahedral mica crystals are frequently found in the volcanoclastic products emplaced during the final stages of the activity of the Colli Albani volcano (Roman Region, central Italy). In the youngest phreatomagmatic deposits, mica is found either as a minor mineral phase in holocrystalline ejecta, scoriae, and coherent pyroclastics, or as loose phenocryst in incoherent pyroclastics. Based on optical and electron microscope investigations, as well as crystal chemical and structural data, the micas selected for this study were divided into two groups, the first one encompassing brownish, Fe-rich crystals (type-A phlogopites, hereafter referred as t-A) with 0.68
ISSN:0024-4937
1872-6143
DOI:10.1016/j.lithos.2009.05.030