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La evidencia de 186Os y 187Os acoplados para la interacción núcleo-manto
1A. D. Brandon, R. J. Walker, J. W. Morgan, Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, USA. J. W. Morgan, Department of Earth Resources, Colorado State University, Fort Collins, CO 80.
Science (New York, N.Y.)
|June 11, 1998
Resumen
Los análisis de isótopos de osmio revelan que las lavas picríticas hawaianas contienen material de núcleo externo. Esto sugiere que algunas plumas del manto se originan en el límite núcleo-manto, distinguibles por sus firmas isotópicas.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Geología de Isótopos Geología de Isótopos.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Las plumas del manto son conductos de roca caliente que se elevan a través del manto de la Tierra.
- El origen y la composición de las plumas del manto proporcionan información sobre los procesos profundos de la Tierra.
- Los isótopos de osmio (186Os/188Os y 187Os/188Os) son trazadores sensibles de las fuentes del manto.
Objetivo del estudio:
- Para investigar el origen de las lavas picríticas hawaianas utilizando la geoquímica del isótopo de osmio.
- Para determinar si las columnas del manto pueden incorporar material del núcleo de la Tierra.
- Establecer isótopos de osmio como herramienta para distinguir fuentes de manto profundas versus poco profundas.
Principales métodos:
- Medición precisa de las proporciones de osmio-186/osmio-188 (186Os/188Os) y osmio-187/osmio-188 (187Os/188Os) en muestras de lava picrítica de Hawai.
- Comparación de los datos isotópicos con el manto superior condrítico y las posibles composiciones de material del núcleo.
- Modelado de escenarios de mezcla entre el manto y los materiales del núcleo.
Principales resultados:
- Las lavas picríticas de Hawai exhiben enriquecimientos significativos tanto en 186Os/188Os (0.0080.018%) como en 187Os/188Os (5.49.0%) en relación con el manto superior condrítico.
- Estos enriquecimientos isotópicos acoplados se explican mejor por la adición de 0,51 wt% de metal del núcleo externo a una porción de la capa D1.
- La mezcla luego se elevó para formar las lavas picríticas observadas.
Conclusiones:
- Algunas columnas del manto, como las que se encuentran debajo de Hawái, probablemente se originan en el límite núcleo-manto.
- La incorporación de material del núcleo externo en el manto es un proceso viable.
- Los isótopos de osmio sirven como una poderosa herramienta para diferenciar entre las columnas del manto procedentes de regiones poco profundas frente a las profundas del manto, incluida la frontera núcleo-manto.
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