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Caught in the act: Implications for the increasing abundance of mafic enclaves during the recent eruptive episodes of the Soufrière Hills Volcano, Montserrat
Author(s) -
Barclay Jenni,
Herd Richard A.,
Edwards Ben R.,
Christopher Thomas,
Kiddle Emma J.,
Plail Melissa,
Donovan Amy
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl042509
Subject(s) - mafic , porphyritic , andesite , geology , volcano , lava , basalt , geochemistry , lava dome , basaltic andesite , magma , volcanic rock , paleontology , quartz
An exceptional opportunity to sample several large blocks sourced from the same region of the growing Soufrière Hills lava dome has documented a significant increase in the presence of mafic enclaves in the host andesite during the course of a long‐lived eruptive episode with several phases. In 1997 (Phase I) mafic inclusions comprised ∼1 volume percent of erupted material; in 2007 (Phase III) deposits their volumetric abundance increased to 5–7 percent. A broader range of geochemically distinctive types occurs amongst the 2007 enclaves. Crystal‐poor enclaves generally have the least evolved (basaltic) compositions; porphyritic enclaves represent compositions intermediate between basaltic and andesitic compositions. The absence of porphyritic enclaves prior to Phase III magmatism at Soufrière Hills Volcano suggests that a mixing event occurred during the course of the current eruptive episode, providing direct evidence consistent with geophysical observations that the system is continuously re‐invigorated from depth.