Conference proceeding
Magmatic dynamics and eruption styles at Volcan de Colima, Mexico
American Geophysical Union Fall Meeting, Vol.2011
American Geophysical Union 2011 fall meeting
12/2011
Abstract
The current phase of activity (1998-ongoing) at Volcan de Colima (VDC) provides a unique opportunity to combine the petrology, geochemistry and monitoring records to investigate the dynamics of magmatic systems feeding andesitic arc volcanoes and to assess the relationship between magmatic processes and eruption style. VDC current phase of activity is characterized by shifts between effusive periods of dome growth and lava flows with intermittent low magnitude explosions and periods of high magnitude explosive Vulcanian events. The magmas are petrographically homogenous andesites with 59.0-61.4 wt% SiO (sub 2) (H (sub 2) O-free), yet the melt inclusion and phenocryst compositions indicate that the melt crystallizing in the subvolcanic system is consistently dacitic in composition (>65 wt% SiO (sub 2) ). Incorporation of gabbroic fragments from the plutonic roots of the volcano and, to a lesser extent, mixing with mafic melts produced the andesitic bulk rock compositions. The melt inclusions have relatively low H (sub 2) O contents (< 2.5 wt%) and variable CO (sub 2) contents (<40 to 1200 ppm) indicative of a vapour-buffered system in which CO (sub 2) -rich vapour are omnipresent. The melt inclusions chemistry does not show obvious changes in degassing and crystallization mechanism associated with shifts from effusive to explosive eruptions. The effusive phases are, however, accompanied by significant increases in SO (sub 2) fluxes and correspond to peaks in measured (super 226) Ra excess in the magmas, suggesting that influxes of less differentiated and undegassed magmas may, to some extent, cause the observed shifts in activity from predominantly Vulcanian to effusive. The 1998-2010 magmas have ( (super 210) Pb/ (super 226) Ra) close to secular equilibrium suggesting, in conjunction with the measured SO (sub 2) flux, that degassing occurred mostly within few months of the onset of activity in 1998. The absence of a consistent ( (super 210) Pb/ (super 226) Ra) trend with time and persistence of magmas in or close to secular equilibrium requires either several influxes of undegassed magmas, as suggested by observed (super 226) Ra excess peaks, and/or accumulation of gas in the upper volcanic conduit. Overall, this indicates that the current phase of activity at VDC is fed by a shallow magmatic system comprising at least two reservoirs. Influxes of undegassed magmas and mixing in the upper conduit certainly played a role in initiating the effusive phases. However, there is no simple and systematic correlation between the petrological and geochemical records and the shifts in volcanic activity, suggesting that non-linear dynamics of conduit flow resulting from the complex relationship between degassing, crystallization, and extrusion rate ultimately control the transitions from effusive to Vulcanian activity on short time scales.
Details
- Title: Subtitle
- Magmatic dynamics and eruption styles at Volcan de Colima, Mexico
- Creators
- Olivier Reubi - Institute of GeochemistryJon D Blundy - University of BristolNick R Varley - Universidad de Colima MEX MexicoK. W Sims - University of WyomingJost Eikenberg - Paul Scherrer InstituteMark K Reagan - University of Iowa USA United States
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2011
- Conference
- American Geophysical Union 2011 fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2011 fall meeting
- Language
- English
- Date published
- 12/2011
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240880802771
Metrics
10 Record Views