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El desequilibrio mineral en las lavas se explica por la auto-mezcla convectiva en cámaras de magma abiertas
S Couch1, R S Sparks, M R Carroll
1Department of Earth Sciences, Bristol University, Bristol BS8 1RJ, UK. Susan.Couch@bristol.ac.uk
Nature
|June 29, 2001
Resumen
La mezcla de magma en lavas de andesita y dacita no siempre puede indicar diferentes orígenes. La convección dentro de un solo cuerpo de magma, calentado desde abajo y enfriado desde arriba, puede crear características cristalinas similares.
Área de la Ciencia:
- Volcanología Volcanología.
- Petrología Petrología.
- La geoquímica es la geoquímica.
Sus antecedentes:
- Las lavas porfiríticas de andesita y dacita a menudo exhiben características de desequilibrio cristalino.
- Estas características se atribuyen típicamente a eventos de mezcla de magma.
Objetivo del estudio:
- Proponer una explicación alternativa para las texturas de desequilibrio en las lavas.
- Para investigar el papel de la auto-mezcla convectiva en los cuerpos de magma.
Principales métodos:
- Análisis petrológico de la lava de andesita del volcán Soufrière Hills, Montserrat.
- Petrología experimental en una composición representativa de la masa del suelo.
- Modelado termodinámico de las interacciones entre mineral y fundido.
Principales resultados:
- Las características observadas en la andesita de Montserrat sugieren un evento de calentamiento y mezcla de cristales.
- Los datos experimentales indican que se requieren altas temperaturas para explicar las composiciones de crecimiento excesivo de plagioclase.
- La auto-mezcla convectiva puede generar minerales con composiciones que parecen no coexistentes bajo equilibrio.
Conclusiones:
- Las texturas de desequilibrio en las lavas pueden surgir de procesos convectivos internos dentro de un solo cuerpo de magma.
- La auto-mezcla convectiva proporciona un mecanismo viable para generar complejos conjuntos minerales.
- Este mecanismo desafía la dependencia exclusiva de la mezcla de magma para explicar las características petrológicas observadas.
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