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Restricciones experimentales sobre la anisotropía eléctrica del sistema litosfera-astenosfera
Anne Pommier1, Kurt Leinenweber2, David L Kohlstedt3
11] University of California San Diego, Scripps Institution of Oceanography, Institute of Geophysics and Planetary Physics, La Jolla, California 92093, USA [2] School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA.
Nature
|June 12, 2015
Resumen
Las rocas del manto deformadas exhiben una conductividad eléctrica alineada con la deformación, lo que explica las anomalías sísmicas y eléctricas. Esto sugiere que las capas de olivino alineadas con la fusión controlan la conductividad del manto.
Área de la Ciencia:
- La geofísica es la geofísica.
- Física de los minerales Física de los minerales
- La tectónica es la tectónica.
Sus antecedentes:
- El movimiento de la placa litosférica causa deformaciones cerca del límite litosférico-astenosférico.
- La viscosidad reducida en la astenosfera, posiblemente debido al derretimiento o al agua, explica las anomalías sísmicas y eléctricas.
- La influencia de la fusión en las propiedades del material del manto deformado no se entiende bien.
Objetivo del estudio:
- Investigar el efecto de la fusión en las propiedades eléctricas de las rocas del manto deformadas.
- Restringir el papel del derretimiento en la generación de las anomalías de conductividad del manto observadas.
- Desarrollar un modelo para la anisotropía eléctrica en el manto superior parcialmente fundido.
Principales métodos:
- Medidas de anisotropía eléctrica en olivino deformado y rocas parcialmente fundidas a altas temperaturas (<900°C) y presiones (~3 GPa).
- Deformación experimental de agregados de olivino y rocas parcialmente fundidas.
- Desarrollo de un modelo basado en experimentos para la conductividad eléctrica en capas, manto deformado.
Principales resultados:
- La conductividad eléctrica es la más alta paralela a la dirección de deformación en todas las muestras.
- La olivina altamente cortada mostró un aumento de diez veces en la conductividad en comparación con las muestras no deformadas.
- Un modelo con capas alternas de olivino cortado y fundido explica mejor la alta anisotropía eléctrica (hasta 100x) y los datos de campo.
Conclusiones:
- La deformación y la alineación del fundido son claves para la alta conductividad eléctrica en la astenosfera.
- El modelo propuesto explica los perfiles de conductividad-profundidad del manto en regiones de fusión.
- Una astenosfera eléctricamente anisotrópica que recubre una litosfera inferior conductiva y isotrópica es consistente con los datos de campo.
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