Spherulite formation in obsidian lavas in the Aeolian Islands, Italy

Liam A. Bullock (Corresponding Author), Ralf Gertisser, Brian O’Driscoll

Research output: Contribution to journalArticle

4 Citations (Scopus)
6 Downloads (Pure)

Abstract

Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterisedby spatial, textural and geochemical variations, formed by different processes.Spherulites vary in size from <1 mm to 8 mm, are spherical to elongate inshape, and show variable radial interiors. Spherulites occur individually or indeformation bands, and some are surrounded by clear haloes and brown rims.Spherulites typically contain cristobalite (α, β) and orthoclase, and rhyoliticglass, and grew over an average period of 5 days, with modification at lowertemperatures. Heterogeneity relates to formation processes of spherulite‘types’ at different stages of cooling and emplacement. Distinct populationsconcentrate within deformation structures, with variations in shape andinternal structure. Crystal Size Distribution (CSD) plots show differing sizepopulations and growth periods. Spherulites which formed at high temperaturesshow elongation, where deformation triggered further spherulite nucleationand growth. Spherulites formed at mid-glass transition temperatures arespherical, and spherulites are modified at vapour-phase temperatures. Enhanced undercooling, deformation, and modification are therefore pivotal in thedevelopment spherulite heterogeneity in obsidian lavas.
Original languageEnglish
Pages (from-to)37-54
Number of pages18
JournalPeriodico di Mineralogia
Volume86
Early online dateFeb 2017
DOIs
Publication statusPublished - 2017

Fingerprint

obsidian
spherulite
spherulites
Italy
Undercooling
Silicon Dioxide
Elongation
Vapors
Cooling
Crystals
cristobalite
orthoclase
supercooling
rims
Temperature
glass transition temperature
elongation
halos
emplacement
plots

Keywords

  • Spherulites
  • obsidian
  • Aeolian Islands
  • Glass Transition
  • Lipari
  • Vulcano

Cite this

Spherulite formation in obsidian lavas in the Aeolian Islands, Italy. / Bullock, Liam A. (Corresponding Author); Gertisser, Ralf ; O’Driscoll, Brian.

In: Periodico di Mineralogia, Vol. 86, 2017, p. 37-54.

Research output: Contribution to journalArticle

Bullock, Liam A. ; Gertisser, Ralf ; O’Driscoll, Brian. / Spherulite formation in obsidian lavas in the Aeolian Islands, Italy. In: Periodico di Mineralogia. 2017 ; Vol. 86. pp. 37-54.
@article{a643317eb841418da1019719261dfdcc,
title = "Spherulite formation in obsidian lavas in the Aeolian Islands, Italy",
abstract = "Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterisedby spatial, textural and geochemical variations, formed by different processes.Spherulites vary in size from <1 mm to 8 mm, are spherical to elongate inshape, and show variable radial interiors. Spherulites occur individually or indeformation bands, and some are surrounded by clear haloes and brown rims.Spherulites typically contain cristobalite (α, β) and orthoclase, and rhyoliticglass, and grew over an average period of 5 days, with modification at lowertemperatures. Heterogeneity relates to formation processes of spherulite‘types’ at different stages of cooling and emplacement. Distinct populationsconcentrate within deformation structures, with variations in shape andinternal structure. Crystal Size Distribution (CSD) plots show differing sizepopulations and growth periods. Spherulites which formed at high temperaturesshow elongation, where deformation triggered further spherulite nucleationand growth. Spherulites formed at mid-glass transition temperatures arespherical, and spherulites are modified at vapour-phase temperatures. Enhanced undercooling, deformation, and modification are therefore pivotal in thedevelopment spherulite heterogeneity in obsidian lavas.",
keywords = "Spherulites, obsidian, Aeolian Islands, Glass Transition, Lipari, Vulcano",
author = "Bullock, {Liam A.} and Ralf Gertisser and Brian O’Driscoll",
note = "The authors wish to gratefully acknowledge Andy Tindle (The Open University) for assistance with EMP analyses, and Richard Darton and David Evans (Keele University) for assistance with XRD and Prof Alun Vaughan and Nicola Freebody (University of Southampton) with Raman analyses. LAB is grateful to Sophie Blanchard for support with MATLAB. The authors acknowledge support from Keele University, and grants from the Mineralogical Society (UK and Ireland) and Volcanic and Magmatic Studies Group. The authors thank Silvio Mollo and Francesca Forni for their detailed and helpful comments.",
year = "2017",
doi = "10.2451/2017PM680",
language = "English",
volume = "86",
pages = "37--54",
journal = "Periodico di Mineralogia",
issn = "2239-1002",
publisher = "Bardi Editore",

}

TY - JOUR

T1 - Spherulite formation in obsidian lavas in the Aeolian Islands, Italy

AU - Bullock, Liam A.

AU - Gertisser, Ralf

AU - O’Driscoll, Brian

N1 - The authors wish to gratefully acknowledge Andy Tindle (The Open University) for assistance with EMP analyses, and Richard Darton and David Evans (Keele University) for assistance with XRD and Prof Alun Vaughan and Nicola Freebody (University of Southampton) with Raman analyses. LAB is grateful to Sophie Blanchard for support with MATLAB. The authors acknowledge support from Keele University, and grants from the Mineralogical Society (UK and Ireland) and Volcanic and Magmatic Studies Group. The authors thank Silvio Mollo and Francesca Forni for their detailed and helpful comments.

PY - 2017

Y1 - 2017

N2 - Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterisedby spatial, textural and geochemical variations, formed by different processes.Spherulites vary in size from <1 mm to 8 mm, are spherical to elongate inshape, and show variable radial interiors. Spherulites occur individually or indeformation bands, and some are surrounded by clear haloes and brown rims.Spherulites typically contain cristobalite (α, β) and orthoclase, and rhyoliticglass, and grew over an average period of 5 days, with modification at lowertemperatures. Heterogeneity relates to formation processes of spherulite‘types’ at different stages of cooling and emplacement. Distinct populationsconcentrate within deformation structures, with variations in shape andinternal structure. Crystal Size Distribution (CSD) plots show differing sizepopulations and growth periods. Spherulites which formed at high temperaturesshow elongation, where deformation triggered further spherulite nucleationand growth. Spherulites formed at mid-glass transition temperatures arespherical, and spherulites are modified at vapour-phase temperatures. Enhanced undercooling, deformation, and modification are therefore pivotal in thedevelopment spherulite heterogeneity in obsidian lavas.

AB - Spherulites in obsidian lavas of Lipari and Vulcano (Italy) are characterisedby spatial, textural and geochemical variations, formed by different processes.Spherulites vary in size from <1 mm to 8 mm, are spherical to elongate inshape, and show variable radial interiors. Spherulites occur individually or indeformation bands, and some are surrounded by clear haloes and brown rims.Spherulites typically contain cristobalite (α, β) and orthoclase, and rhyoliticglass, and grew over an average period of 5 days, with modification at lowertemperatures. Heterogeneity relates to formation processes of spherulite‘types’ at different stages of cooling and emplacement. Distinct populationsconcentrate within deformation structures, with variations in shape andinternal structure. Crystal Size Distribution (CSD) plots show differing sizepopulations and growth periods. Spherulites which formed at high temperaturesshow elongation, where deformation triggered further spherulite nucleationand growth. Spherulites formed at mid-glass transition temperatures arespherical, and spherulites are modified at vapour-phase temperatures. Enhanced undercooling, deformation, and modification are therefore pivotal in thedevelopment spherulite heterogeneity in obsidian lavas.

KW - Spherulites

KW - obsidian

KW - Aeolian Islands

KW - Glass Transition

KW - Lipari

KW - Vulcano

U2 - 10.2451/2017PM680

DO - 10.2451/2017PM680

M3 - Article

VL - 86

SP - 37

EP - 54

JO - Periodico di Mineralogia

JF - Periodico di Mineralogia

SN - 2239-1002

ER -