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El agua y el estado de oxidación de los magmas de la zona de subducción
Katherine A Kelley1, Elizabeth Cottrell
1Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA. kelley@gso.uri.edu
Science (New York, N.Y.)
|August 1, 2009
Resumen
La fugacidad del oxígeno del manto, crucial para la Tierra.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Petrología Petrología.
- La tectónica es la tectónica.
Sus antecedentes:
- La fugacidad de oxígeno del manto controla el intercambio de masa interno-externo de la Tierra.
- Se debaten los factores que influyen en la fugacidad de oxígeno del manto y su evolución.
Objetivo del estudio:
- Investigar los controles sobre la fugacidad de oxígeno en el manto.
- Enlazar los ciclos tectónicos con los estados de oxidación del manto.
Principales métodos:
- Mediciones de la relación Fe3+/SigmaFe utilizando espectroscopia de estructura de absorción de micro rayos X cercana al borde Fe-K.
- Análisis del contenido de H2O magmático pre-eruptivo en vidrios basálticos y inclusiones fundidas.
- Muestreo global a través de diversas configuraciones tectónicas de placas.
Principales resultados:
- Las relaciones magmáticas Fe3+/SigmaFe aumentan hacia las zonas de subducción (crestales: 0.13-0.17, arcos dorsales: 0.15-0.19, arcos: 0.18-0.32).
- Las relaciones Fe3+/SigmaFe se correlacionan linealmente con el contenido de H2O magmático.
- Las correlaciones observadas se vinculan con los elementos trazadores de fluidos derivados de losas.
Conclusiones:
- La transferencia de masa de las placas subducidas oxida directamente la cuña del manto.
- Los fluidos volátiles y derivados de la losa son los principales impulsores de la oxidación del manto.
- Proporciona información sobre la evolución redox de la cuña del manto.
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