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Difusión de oxígeno de corta duración durante la alteración meteórica caliente y profunda de la anortosita
1Department of Geological Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA. Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6365, USA.
Science (New York, N.Y.)
|December 22, 1999
Resumen
La plagioclase en rocas meta-íneas muestra un agotamiento extremo del oxígeno-18, lo que indica una interacción de alta temperatura con fluidos meteorológicos. Esto sugiere un rápido intercambio de fluidos y difusión dentro del anortosito.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Geología de Isótopos Geología de Isótopos.
- Petrología Metamórfica.
Sus antecedentes:
- La plagioclase en rocas meta-íneas puede preservar registros de la interacción fluido-roca.
- Las composiciones de isótopos de oxígeno proporcionan información sobre los procesos geológicos.
Objetivo del estudio:
- Para investigar la composición isotópica de oxígeno de plagioclase de la anortosita de Boehls Butte.
- Para determinar la naturaleza y el momento de la interacción del fluido dentro del anortosito.
Principales métodos:
- Análisis de isótopos de oxígeno del plagioclase.
- Análisis microestructural de los cristales de plagioclase.
- Modelado geoquímico del intercambio isotópico.
Principales resultados:
- La plagioclasa exhibe valores de oxígeno-18 muy agotados (hasta -16 por milímetro).
- Evidencia de intercambio isotópico a alta temperatura (más de 500°C) con fluidos meteorológicos.
- La permeabilidad mejorada por la reacción facilitó el influjo de fluidos.
- Los gradientes isotópicos pronunciados indican un intercambio difusional de corta duración (~10^4 años) y altas proporciones agua: roca.
Conclusiones:
- El fluido meteorológico alteró significativamente el anortosito a altas temperaturas.
- Se produjo un rápido intercambio de fluidos y posterior cesación de la difusión.
- La anortosita de Boehls Butte proporciona una ventana única a los antiguos sistemas meteorológicos e hidrotermales.
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