Spherulite formation in obsidian lavas in the Aeolian Islands, Italy
- Bullock, LA
- Gertisser, R
- O'Driscoll, B
DOIAbstract
Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterised by spatial, textural and geochemical variations, formed by different processes. Spherulites vary in size from <1 mm to 8 mm, are spherical to elongate in shape, and show variable radial interiors. Spherulites occur individually or in deformation bands, and some are surrounded by clear haloes and brown rims. Spherulites typically contain cristobalite (α, β) and orthoclase, titanomagnetite and rhyolitic glass, and grew over an average period of 5 days, with modification over a few hundred years at lower temperatures. Heterogeneity relates to formation processes of spherulite ‘types’ at different stages of cooling and emplacement. Distinct populations concentrate w...
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