Shallow-storage conditions for the rhyolite of the 1912 eruption at Novarupta, Alaska

Citation
Ml. Coombs et Je. Gardner, Shallow-storage conditions for the rhyolite of the 1912 eruption at Novarupta, Alaska, GEOLOGY, 29(9), 2001, pp. 775-778
Citations number
25
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOLOGY
ISSN journal
0091-7613 → ACNP
Volume
29
Issue
9
Year of publication
2001
Pages
775 - 778
Database
ISI
SICI code
0091-7613(200109)29:9<775:SCFTRO>2.0.ZU;2-#
Abstract
Recent studies have proposed contrasting models for the plumbing system tha t fed the 1912 eruption of Novarupta, Alaska. Here, we investigate the cond itions under which the rhyolitic part of the erupted magma last resided in the crust prior to eruption. Geothermometry suggests that the rhyolite was held at similar to 800-850 degreesC, and analyses of melt inclusions sugges t that it was fluid saturated and contained similar to4 wt% water. Hydrothe rmal, water-saturated experiments on rhyolite pumice reveal that at those t emperatures the rhyolite was stable between 40 and 100 MPa, or a depth of 1 .8-4.4 km. These results suggest that pre-eruptive storage and crystal grow th of the rhyolite were shallow; if the rhyolite ascended from greater dept hs, it did so slowly enough for unzoned phenocrysts to grow as it passed th rough the shallow crust.