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La composición isotópica del tungsteno del manto de la Tierra antes del bombardeo terminal
Matthias Willbold1, Tim Elliott, Stephen Moorbath
1Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK. m.willbold@bristol.ac.uk
Nature
|September 9, 2011
Resumen
Los metales preciosos en la Tierra se explican por una capa tardía de meteoritos. El análisis de isótopos de tungsteno de rocas antiguas apoya esta teoría, descartando otras explicaciones para la abundancia de metales.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Ciencias planetarias Ciencias planetarias.
- Geología de Isótopos Geología de Isótopos.
Sus antecedentes:
- Los metales preciosos como el oro son abundantes a pesar de las predicciones de formación de núcleos.
- Una explicación propuesta es un "barniz tardío" de los meteoritos después de la formación del núcleo.
- Las antiguas rocas de Isua, Groenlandia, son anteriores a este bombardeo de meteoritos.
Objetivo del estudio:
- Para probar la hipótesis de la "cartilla tardía" para la abundancia de metales preciosos.
- Para determinar la composición de la Tierra antes del bombardeo final de meteoritos.
- Para analizar los isótopos de tungsteno en rocas antiguas en busca de pistas de composición.
Principales métodos:
- Análisis isotópico de alta precisión del tungsteno (W).
- Análisis de rocas de 3.800 millones de años de edad de Isua, Groenlandia.
- Comparación de las proporciones de isótopos W en muestras terrestres antiguas frente a las modernas.
Principales resultados:
- Las rocas de Isua muestran una relación (182) W / 184) W significativamente más alta que las muestras modernas.
- Esta relación elevada se alinea con el impacto esperado de una chapa tardía.
- No se soportaron modelos alternativos como la remezcla del manto o la interacción núcleo-manto.
Conclusiones:
- La hipótesis de la "cartilla tardía" está fuertemente respaldada por los datos de isótopos de tungsteno.
- La composición de la Tierra fue significativamente modificada por impactos tardíos de meteoritos.
- Este bombardeo puede haber iniciado los patrones modernos de convección del manto.
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