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La posible subducción de material continental a profundidades mayores de 200 km
1Laboratory of Lithosphere Tectonic Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. yekai@hotmail.com
Nature
|October 26, 2000
Resumen
El material continental puede ser subducido a más de 200 km de profundidad, como lo demuestran las exoluciones en granados. Este hallazgo ayuda a comprender el crecimiento de los supercontinentes y la dinámica de los márgenes de las placas.
Área de la Ciencia:
- Geología Geología Geología.
- La geofísica es la geofísica.
- La mineralogía es la Mineralogía.
Sus antecedentes:
- La subducción de la litosfera continental es clave para los ciclos de los supercontinentes y la evolución del margen de las placas.
- Las rocas metamórficas de ultra alta presión (UHP) indican que el material continental puede alcanzar al menos 120 km de profundidad.
- Las inferencias anteriores de una subducción más profunda (150-300 km) se basaron en evidencia indirecta de peridotitas de granate.
Objetivo del estudio:
- Para rastrear directamente la profundidad de la subducción continental en las rocas de la corteza metamórfica UHP.
- Identificar indicadores mineralógicos confiables para la subducción continental profunda.
- Para probar las predicciones de disolución de piroxeno en granate a profundidades >150 km.
Principales métodos:
- Análisis de eclogitas del cinturón metamórfico Sulu UHP, China.
- Análisis microscópico y químico de las exoluciones minerales dentro del granate.
- Interpretación de la química mineral (Na2O, Si octaédrico) para inferir las condiciones de presión y profundidad.
Principales resultados:
- Se observaron altas concentraciones de clinopiroxeno, rutilo y disoluciones de apatita en granate.
- Interpretó estas exsolucciones como evidencia de la formación de soluciones sólidas de piroxeno a alta presión.
- Determinó que las concentraciones observadas de Na2O y Si octaédrico indican profundidades de subducción superiores a 200 km.
Conclusiones:
- El material continental puede ser subducido a profundidades superiores a 200 km.
- Las texturas de exsolución en el granate proporcionan un indicador directo de la subducción continental profunda.
- Esto proporciona datos cruciales para la comprensión de los procesos profundos de la corteza en los márgenes convergentes.
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