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Controls on variations in cristobalite abundance in ash generated by the Soufrière Hills volcano, Montserrat in the period 1997-2010

Horwell, C.J.; Hillman, S.E.; Cole, P.D.; Loughlin, S.C.; Llewellin, E.W.; Damby, D.E.; Christopher, T.

Controls on variations in cristobalite abundance in ash generated by the Soufrière Hills volcano, Montserrat in the period 1997-2010 Thumbnail


Authors

S.E. Hillman

P.D. Cole

S.C. Loughlin

D.E. Damby

T. Christopher



Abstract

The Soufrière Hills Volcano (SHV) crystallizes cristobalite (crystalline silica) in its lava domes, and inhalation of cristobalite-rich ash may pose a chronic respiratory hazard. We investigate the causes of variation in cristobalite abundance (measured by X-ray diffraction) in ash from dome collapses, explosions and ash venting from 1997 to 2010. Cristobalite abundance in bulk dome-collapse ash varies between 4 and 23 wt%. During periods of slow lava extrusion (<5 m3 s−1), cristobalite is abundant (7–23 wt%), which we attribute to extensive devitrification in slow-cooling lava; it can also form rapidly (15 wt% in 2 months), but we find no correlation between cristobalite abundance and dome residence time (DRT). By contrast, during rapid extrusion (>5 m3 s−1), cristobalite abundance is low (4–7 wt%, similar to that associated with Vulcanian explosions), and correlates strongly with DRT. We attribute this correlation to progressive vapour-phase mineralization or devitrification, and the lack of contamination by older lava. Cristobalite abundance is expected to be >7 wt% for collapse of slowly extruded lava, for ash venting through a dome or for incorporation of hydrothermally altered edifice during explosions; cristobalite abundance is expected to be <7 wt% for collapse of rapidly extruded lava, for ash venting without dome incorporation and from Vulcanian explosions at SHV.

Citation

Horwell, C., Hillman, S., Cole, P., Loughlin, S., Llewellin, E., Damby, D., & Christopher, T. (2014). Controls on variations in cristobalite abundance in ash generated by the Soufrière Hills volcano, Montserrat in the period 1997-2010. Memoirs, 39, 399-406. https://doi.org/10.1144/m39.21

Journal Article Type Article
Acceptance Date Feb 15, 2013
Online Publication Date Jun 2, 2014
Publication Date Jun 2, 2014
Deposit Date Oct 18, 2013
Publicly Available Date Jun 17, 2014
Journal Memoirs
Print ISSN 0435-4052
Electronic ISSN 2041-4722
Publisher The Geological Society
Peer Reviewed Peer Reviewed
Volume 39
Pages 399-406
DOI https://doi.org/10.1144/m39.21
Public URL https://durham-repository.worktribe.com/output/1467849

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