Petrological and geochemical variation during the Soufrière Hills eruption, 1995 to 2010

Christopher, T.; Humphreys, M.C.S.; Barclay, J.; Genareau, K.; De Angelis, S.M.H.; Plail, M.; Donovan, A.

doi:10.1144/m39.17

Petrological and geochemical variation during the Soufrière Hills eruption, 1995 to 2010

Christopher, T.; Humphreys, M.C.S.; Barclay, J.; Genareau, K.; De Angelis, S.M.H.; Plail, M.; Donovan, A.

Authors

T. Christopher

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

J. Barclay

K. Genareau

S.M.H. De Angelis

M. Plail

A. Donovan

Contributors

G. Wadge
Editor

R.E.A. Robertson
Editor

B. Voight
Editor

Abstract

The andesite lava erupted at the Soufrière Hills Volcano (SHV) is crystal-rich with 33–63% phenocrysts of plagioclase (65%), amphibole (28%), orthopyroxene (7%), and minor Fe–Ti oxide and clinopyroxene microphenocrysts. The andesite hosts mafic enclaves that have similar mineral phases to the andesite. The enclaves are generally crystal-poor but can have up to 27% of inherited phenocrysts from the andesite, the majority of which are plagioclase. The eruption is defined by discrete periods of extrusion called phases, separated by pauses. The enclaves exhibit bulk geochemical trends that are consistent with fractionation. We infer that the intruded mafic liquids of Phases I and II interacted and assimilated plutonic residue remaining from the multiple prior mafic intrusions, while the basaltic liquids from Phases III and V assimilated relatively little material. We also infer a change in the basaltic composition coming from depth. The bulk Fe contents of both magma types are coupled and they both show a systematic interphase variation in Fe content. We interpret the coupled Fe variation to be due to contamination of the andesite from the intruding basalt via diffusion and advection processes, resulting in the erupted andesite products bearing the geochemical imprint of the syn-eruptive enclaves.

Citation

Christopher, T., Humphreys, M., Barclay, J., Genareau, K., De Angelis, S., Plail, M., & Donovan, A. (2014). Petrological and geochemical variation during the Soufrière Hills eruption, 1995 to 2010. In G. Wadge, R. Robertson, & B. Voight (Eds.), The Eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010 (317-342). The Geological Society. https://doi.org/10.1144/m39.17

Publication Date	Jun 2, 2014
Deposit Date	Feb 4, 2014
Publicly Available Date	Jun 26, 2014
Publisher	The Geological Society
Pages	317-342
Series Title	Geological Society of London, Memoirs
Series Number	39
Book Title	The Eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010.
Chapter Number	17
DOI	https://doi.org/10.1144/m39.17