Abstract
Time scales of metasomatism, differentiation and degassing at Volcan de Colima
Mineralogical magazine, Vol.75(3), p.1714
Goldschmidt2011
06/2011
Abstract
Volcan de Colima, Mexico (VDC) nearly continuous activity since 1998 provides a unique opportunity to assess the times scales characteristic of intermediate arc volcanoes. VDC andesites have ( (super 238) U/ (super 230) Th) = 1, but have significant excesses of (super 231) Pa and (super 226) Ra. These excesses, and relatively low Th contents, indicate that addition of Th-rich sediments in secular equilibrium to the mantle source cannot account for (super 238) U- (super 230) Th equilibrium, as generally advocated. In the VDC case, the U-series suggest that slab fluids carrying U were not added to the mantle wedge in the last 350 kyr and (super 226) Ra excesses are most likely mantle melting signals. (super 226) Ra and (super 231) Pa excesses indicate that the time scales of differentiation from primary mafic to dacitic melt (composition of the crystallizing melt) are short and < 1.6 kyr. Most 1998-2010 magmas have ( (super 210) Pb/ (super 226) Ra) = 1, however small (super 210) Pb deficits are measured in few samples. This indicates that the magmas erupted at the onset of the eruptive phase (1998) degassed either more than 100 yr ago or within few months of eruption. Observed changes in petrology and the SO (sub 2) flux measured prior to 1998 concur to suggest that significant degassing occurred within few months of eruption. Increasing maximum (super 210) Pb deficits with time are consistent with progressive degassing of a magma batch since 1998, but require several influxes of undegassed magmas and incomplete mixing between the magma batches. Influxes of undegassed magmas may cause the observed shifts in activity from Vulcanian to effusive.
Details
- Title: Subtitle
- Time scales of metasomatism, differentiation and degassing at Volcan de Colima
- Creators
- Olivier Reubi - ETH ZurichK. W. W SimsJ EikenbergMark K ReaganN. R VarleyB Bourdon
- Resource Type
- Abstract
- Publication Details
- Mineralogical magazine, Vol.75(3), p.1714
- Conference
- Goldschmidt2011
- Publisher
- Mineralogical Society
- ISSN
- 0026-461X
- eISSN
- 1471-8022
- Alternative title
- Goldschmidt 2011 abstract volume
- Language
- English
- Date published
- 06/2011
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240900102771
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