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El estado redox del manto de arco utilizando la sistemática Zn/Fe
Cin-Ty A Lee1, Peter Luffi, Véronique Le Roux
1Department of Earth Sciences, Rice University, Houston, Texas 77005, USA.
Nature
|December 3, 2010
Resumen
La relación zinc-hierro (Zn/Fe(T)) en magmas de arco primitivo sugiere que la oxidación del manto no se debe únicamente a la subducción. La diferenciación de nivel superficial, no la alteración de la cuña del manto, probablemente causa estados de oxidación más altos en las lavas de arco.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Petrología Petrología.
- Geodinámica del manto geodinámico.
Sus antecedentes:
- Las lavas de arco suelen estar más oxidadas que los basaltos de la cordillera oceánica media.
- Se cree que la subducción introduce componentes oxidados en el manto, lo que lleva a una cuña oxidada del manto sub-arco.
- Determinar directamente el estado de oxidación del hierro en el manto sub-arco es un desafío, alimentando el debate sobre su estado de oxidación intrínseco.
Objetivo del estudio:
- Para investigar el estado redox de la fuente del manto para magmas de arco.
- Para determinar si la subducción altera significativamente el estado de oxidación de la cuña del manto.
- Para comprender los procesos que controlan la oxidación del hierro en las lavas de arco.
Principales métodos:
- Utilizando la relación Zn/Fe (T) sensible al redox como un proxy para el estado de valencia del hierro en basaltos de arco primario y sus fuentes de manto.
- Analizando el comportamiento de Fe2+, Fe3+ y Zn durante el derretimiento del manto y la diferenciación del magma.
- Comparando el Zn/Fe (T) en magmas de arco con los basaltos de la cordillera oceánica media.
Principales resultados:
- Los magmas de arco primitivo exhiben proporciones de Zn/Fe (T) similares a las de los basaltos de la cordillera oceánica media, lo que indica estados de oxidación de Fe comparables en los fundidos del manto primario.
- La relación Zn/Fe (T) permanece constante durante la fraccionamiento temprano de la olivina, lo que implica un bajo Fe3+) /Fe (T) en el magma.
- El estado de oxidación del hierro (Fe3+/Fe3T) aumenta y la magnetita se estabiliza sólo después de la progresiva cristalización fraccionaria.
Conclusiones:
- La subducción de material oxidado de la corteza terrestre puede no alterar significativamente el estado redox de la cuña del manto.
- Los estados de oxidación más altos observados en las lavas de arco son probablemente una consecuencia de los procesos de diferenciación magmática a bajo nivel.
- Se necesita más investigación para comprender completamente estos procesos de diferenciación de nivel superficial.
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