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Published on: May 15, 2017
Transición de fase y expansión térmica de la perovskita MgSiO3
Science (New York, N.Y.)
|January 25, 1991
Resumen
La perovskita MgSiO3) sufre una transición estructural a altas presiones y temperaturas. Este hallazgo sugiere precaución al aplicar sus propiedades al manto inferior de la Tierra, apoyando la convección de todo el manto.
Área de la Ciencia:
- Física de los minerales física de los minerales.
- La geoquímica es la geoquímica.
- Geofísica de las altas presiones geofísicas.
Sus antecedentes:
- Comprender el comportamiento de la perovskita de silicato de magnesio (MgSiO3) es crucial para modelar el interior profundo de la Tierra.
- Estudios anteriores se han basado en propiedades de la fase Pbnm, lo que podría tergiversar las condiciones del manto inferior.
Objetivo del estudio:
- Para investigar el comportamiento estructural a alta presión y alta temperatura de la perovskita MgSiO3.
- Para determinar la aplicabilidad de los datos actuales de perovskita MgSiO3 al manto inferior de la Tierra.
Principales métodos:
- Los experimentos de difracción de rayos X in situ se llevaron a cabo utilizando un aparato de yunque cúbico tipo DIA (SAM 85).
- Las mediciones se realizaron a presiones de 7,3 gigapascales y temperaturas superiores a 600 Kelvin.
Principales resultados:
- La perovskita MgSiO3 se transforma desde la simetría ortorrómbica Pbnm a otra estructura de perovskita por encima de 600 K a 7,3 GPa.
- Se observó un aumento de volumen aparente del 0,7% en toda la transición.
- El volumen de células unitarias mostró una expansión lineal con la temperatura por debajo y por encima de la transición.
Conclusiones:
- Es posible que las propiedades físicas de la fase Pbnm no sean aplicables al manto inferior de la Tierra.
- El análisis de densidad sugiere una composición de pirolita con un 10,4% en peso de hierro en condiciones del manto inferior.
- Los datos apoyan la convección de todo el manto y sugieren que un manto químicamente homogéneo es plausible.
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