Characterization of mafic enclaves in the erupted products of Soufrière Hills Volcano, Montserrat, 2009 to 2010

Plail, M.; Barclay, J.; Humphreys, M.C.S.; Edmonds, M.; Herd, R.A.; Christopher, T.E.

doi:10.1144/m39.18

Characterization of mafic enclaves in the erupted products of Soufrière Hills Volcano, Montserrat, 2009 to 2010

Plail, M.; Barclay, J.; Humphreys, M.C.S.; Edmonds, M.; Herd, R.A.; Christopher, T.E.

Authors

M. Plail

J. Barclay

Professor Madeleine Humphreys madeleine.humphreys@durham.ac.uk
Professor

M. Edmonds

R.A. Herd

T.E. Christopher

Contributors

G. Wadge
Editor

R.E.A. Robertson
Editor

B. Voight
Editor

Abstract

Lavas from the current eruption of the Soufrière Hills Volcano, Montserrat exhibit evidence for magma mingling, related to the intrusion of mafic magma at depth. We present detailed field, petrological, textural and geochemical descriptions of mafic enclaves in andesite erupted during 2009-2010, and subdivide the enclaves into three distinct types. Type A are mafic, glassy with chilled margins and few inherited phenocrysts. Type B are more evolved with high inherited phenocryst contents and little glass, and are interpreted as significantly hybridised. Type C are composite, with a mafic interior (type A) and a hybrid exterior (type B). All enclaves define tight linear compositional trends, interpreted as mixing between a mafic end-member (type A) and host andesite. Enclave glasses are rhyolitic, owing to extensive crystallisation during quenching. Type A quench crystallisation is driven by rapid thermal equilibration during injection into the andesite. Conversely, type B enclaves form in a hybridised melt layer, which ponded near the base of the chamber and cooled more slowly. Vesiculation near the mafic-silicic interface resulted in disruption of the hybridised layer and the formation of the Type B enclaves. The composite enclaves represent an interface between types A and B, suggesting multiple episodes of mafic injection.

Citation

Plail, M., Barclay, J., Humphreys, M., Edmonds, M., Herd, R., & Christopher, T. (2014). Characterization of mafic enclaves in the erupted products of Soufrière Hills Volcano, Montserrat, 2009 to 2010. In G. Wadge, R. Robertson, & B. Voight (Eds.), The eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010 (343-360). The Geological Society. https://doi.org/10.1144/m39.18

Publication Date	Jun 2, 2014
Deposit Date	Feb 4, 2014
Publicly Available Date	Jun 23, 2014
Publisher	The Geological Society
Pages	343-360
Series Title	Memoirs.
Series Number	39
Book Title	The eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010.
Chapter Number	18
DOI	https://doi.org/10.1144/m39.18