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Complex colour and chemical zoning of sodalite-group phases in hauynophyre lava from Mt. Vulture, Italy

A. Di Muro, E. Bonaccorsi and C. Principe
Complex colour and chemical zoning of sodalite-group phases in hauynophyre lava from Mt. Vulture, Italy
Mineralogical Magazine (August 2004) 68 (4): 591-614

Abstract

The hauynophyre emitted from a parasitic vent of the Vulture stratovolcano is a S- and Cl-rich, leucite-melilite-bearing lava flow containing an unusually large amount of sodalite-group minerals (>23 vol.%). Mineralogical and chemical study of phenocrysts has led to the identification of black hauynes, blue lazurites and of Cl-rich white or black noseans. X-ray diffraction (XRD) study confirms the occurrence of nosean having a low symmetry (P23). Raman spectra and XRD data show that S is fully oxidized to SO (sub 4) in black hauynes and in white noseans, while it is partly reduced to form S (super -) (sub 3) groups in blue lazurites, which also contain H (sub 2) O molecules. Structural and chemical data strongly question the validity of the Hogarth and Griffin (1976) method widely used to resolve the ratio S (super 6+) /S (super 2-) in sodalite-group phases from EMPA data. Among euhedral phenocrysts, large lazurites are only faintly zoned. All other phases show variable core-rim chemical zoning and many phenocrysts are partially resorbed and/or colour-zoned. Black hauynes have highly variable S/Cl and slightly lower SiO (sub 2) /Al (sub 2) O (sub 3) ratios, larger Fe (sub TOT) contents and more compatible trace elements than lazurites. Thin opaque noseansodalite rims surrounding all crystals are interpreted as a result of rapid crystallization driven by exsolution of a S-scavenging fluid phase. We suggest that the extreme complexity of the mineralogical assemblage reflects variable a (sub SiO2) and a (sub H2O) of the silicate melts.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 68
Serial Issue: 4
Title: Complex colour and chemical zoning of sodalite-group phases in hauynophyre lava from Mt. Vulture, Italy
Affiliation: IPGP-Paris VI, Laboratoire de Physique et Chimie des Systemes Volcaniques, Paris, France
Pages: 591-614
Published: 200408
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 52
Accession Number: 2005-011435
Categories: Mineralogy of silicatesIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables, sketch map
N36°30'00" - N47°30'00", E06°30'00" - E19°00'00"
Secondary Affiliation: Universita di Pisa, ITA, ItalyConsiglio Nazionale delle Ricerche, ITA, Italy
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200504
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