Basalt-inherited microlites in silicic magmas: Evidence from Mount Pelée (Martinique, French West Indies)
- 1Institut des Sciences de la Terre d'Orléans, Orléans, France
- 2Laboratoire Magmas et Volcans, Clermont-Ferrand, France
- 3Institut des Sciences de la Terre d'Orléans, Orléans, France
Abstract
During magma ascent in the volcanic conduit, the decompression of a silicic melt may result in the crystallization of morphologically and compositionally specific crystals, designated microlites. Hence, microlites have been considered as probes of mechanisms and time scales of magma ascent. Some microlites, however, appear to be in strong thermodynamic disequilibrium with their surrounding melt. We present here an experimental data set revealing that these microlites actually grew prior to ascent during mafic recharge of the magma chamber. Therefore, these microlites have no genetic relation to decompression-induced crystallization processes. Their presence may affect the rheological properties of the melt, as well as crystal growth mechanisms and kinetics during magma ascent.
Footnotes
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↵GSA Data Repository item 2006204, Appendix (experimental and analytical methods), Table DR1 (composition and the size of 296 natural plagioclase microlites of Mount Pelée), and Table DR2 (P-T conditions and the plagioclase and glass compositions of the experimental charges), is available online at www.geosociety.org/pubs/ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Accepted 23 May 2006.
- Received 1 February 2006.
- Revision received 18 May 2006.
- The Geological Society of America, Inc.
