CO2-rich phonolitic melt and carbonatite immiscibility in early stage of rifting: Melt inclusions from Hanang volcano (Tanzania)

Hanang volcano is the southern volcano of, the southern area of the east part of the East African Rift (the North Tanzanian Divergence) and represents volcanic activity of the first stage of continental break-up. In this study, we investigate glassy melt inclusions in nepheline phenocrysts to constr...

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Bibliographic Details
Published in:Journal of volcanology and geothermal research 2018-06, Vol.358, p.261-272
Main Authors: Baudouin, Céline, Parat, Fleurice, Michel, Thierry
Format: Article
Language:English
Subjects:
Carbonatite
CO2-rich melt
Earth Sciences
Immiscibility, early-stage rifting
Melt inclusions
Nephelinites
Petrography
Sciences of the Universe
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Summary:Hanang volcano is the southern volcano of, the southern area of the east part of the East African Rift (the North Tanzanian Divergence) and represents volcanic activity of the first stage of continental break-up. In this study, we investigate glassy melt inclusions in nepheline phenocrysts to constrain the late stage of Mg-poor nephelinite evolution and the behaviour of volatiles (CO2, H2O, S, F, Cl) during magma storage and ascent during early stage rifting. The melt inclusions have a green silicate glass, a carbonate phase and a shrinkage bubble free of gas phase indicating that carbonatite:silicate (18:82) liquid immiscibility occurred during nephelinite magmatic evolution. The silicate glasses have trachytic composition (Na + K/Al = 1.6–7.2, SiO2 = 54–65.5 wt%) with high CO2 (0.43 wt% CO2), sulfur (0.21–0.92 wt% S) and halogens (0.28–0.84 wt% Cl; 0.35–2.54 wt% F) contents and very low H2O content (
ISSN:0377-0273
1872-6097
DOI:10.1016/j.jvolgeores.2018.05.019