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Transiciones de fase entre beta y ggr (Mg, Fe) 2SiO4 en el manto terrestre: mecanismos e implicaciones reológicas
Science (New York, N.Y.)
|June 3, 1994
Resumen
El estudio revela mecanismos contrastantes para las transformaciones de fase de silicato de magnesio bajo alta presión. Estas transformaciones influyen en la Tierra.
Área de la Ciencia:
- Física mineral Física de los minerales
- La geoquímica es la geoquímica.
- Tierra sólida Geofísica Geofísica de la Tierra sólida
Sus antecedentes:
- El silicato de magnesio (Mg2SiO4) existe en múltiples polimorfas, incluidas la espinela (gamma) y la espinela modificada (beta).
- Comprender las transformaciones de fase es crucial para interpretar los datos sísmicos y la dinámica del manto.
Objetivo del estudio:
- Investigar experimentalmente los mecanismos de las transformaciones de gamma a beta y de beta a gamma en Mg2SiO4.
- Para aclarar el papel de la estructura cristalina y los sistemas de deslizamiento en el control de las vías de transformación.
Principales métodos:
- Los experimentos de alta presión y alta temperatura se llevaron a cabo entre 15-20 GPa y 800-950 ° C.
- Análisis de los mecanismos de transformación de fase, incluidos los procesos de cizallamiento, nucleación y crecimiento.
Principales resultados:
- La transformación de gamma a beta se produce a través de un mecanismo de cizallamiento.
- La transformación beta a gamma implica la nucleación del límite del grano y el crecimiento controlado por la interfaz.
- Estos diferentes mecanismos se atribuyen a los sistemas de deslizamiento independientes disponibles en cada polimorfismo.
Conclusiones:
- Los mecanismos de transformación contrastantes tienen implicaciones para la reología y las propiedades sísmicas en el manto de la Tierra.
- Se predice que la transformación de gamma a beta causará una reducción transitoria de la fuerza en las zonas de subducción y las plumas del manto.
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